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ABSTRACT:

Numerical Model of the Middle Arkansas River Subbasin

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ABSTRACT:

Arid and semi-arid regions present special challenges for water management. Streamflow variation in the upstream countries of the international river basins (River Nile basin), due climate changes or anthropogenic activities such as the ongoing construction of the Grand Ethiopian Renaissance Dam (GERD) is making management of water resources in the downstream countries (Egypt) difficult especially with increasing water demands. Groundwater (GW) and surface water (SW) are two interconnected components of one single resource, impacts on of these components will inevitably affect either the quantity or quality of one another, and that is the situation in the study area. Accordingly, not just SW availability will be affected, but also GW. A three-dimensional transient GW model is used to investigate the impacts of expected decreasing in SW supply due to natural (climate change) or artificial (GRED) changes and increasing GW extraction due to increasing population and agricultural development. This model helps to understand the interaction between the River Nile and the main SW canals and the Quaternary aquifer and to study the recharge possibilities of the aquifer as well as prediction of the aquifer behavior under different stresses in Minia Governorate, Egypt. Three scenarios with eleven probabilities were proposed for the prediction simulations and GW budget, levels and flow exchanges between SW and GW were also calculated on year 2050. The first scenario evaluates the impact of decreasing SW levels by 0.5, 1, and 1.5 m due to climate change or the (GRED), the second scenario studies the effect of increasing GW extraction by 25% and 50% from the extraction rate in the current situation due to agricultural development and increasing demand of GW in different uses. The third scenario examines the potential impact of climate change or the (GRED) and pumping scenarios on GW budget and levels in the Quaternary aquifer where it studies the effect of increasing GW extraction by 25% and 50% with decreasing SW levels by 0.5, 1 and 1.5 m on the aquifer. The maximum change in GW budget and levels was found in the third scenario in the case of increasing GW extraction by 50% and decreasing SW levels by 1.5 m in which AS of the aquifer will decrease to - 712821.9 m(3)/day and GW levels will decrease to range from 23.31 to 43.07 m, respectively.

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ABSTRACT:

A 3D steady state groundwater flow model has been calibrated for the Afram Plains portion of the Southern Voltaian Sedimentary Basin. The model was based on data of hydraulic parameters of the aquifer in the area, and regional groundwater recharge estimates conducted by various researchers using a variety of methods. Model calibration was conducted using hydraulic head data of 43 boreholes in the area. Although the groundwater system in the area appears to receive some amount of recharge from the Volta Lake, the net groundwater outflow into the lake currently outstrips the volumes received from the Lake. The net effect, as suggested by the calibrated model is that groundwater outflows into the Volta Lake amount to approximately 465m(3)/day (169,725m(3)/year). However, with increasing groundwater abstractions at a rate of 2.5%, consistent with annual population projections, a reversal of flow is predicted by 2030 if groundwater recharge remains at the 2015 rates. This would lead to a net lake discharge of approximately 9755m(3)/day into the aquifer system to sustain abstraction rates by 2050. This is predicted to increase further if there is a reduction in groundwater recharge as suggested by regional hydroclimatological data. A 25% reduction in groundwater recharge rate by 2050 will induce a net lake discharge of approximately 11,000m(3)/day into the aquifer system to sustain abstractions for domestic consumption. Lateral outward/environmental flows will reduce from 5200m(3)/day to 2700m(3)/day under the 2015 recharge conditions, and 1300m(3)/day under conditions of reduced recharge by 2050. Groundwater in the area does not appear to hold promise for commercial abstraction for irrigation purposes, especially under climate change conditions.

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ABSTRACT:

In this study, a 3-D groundwater flow model was developed using MODFLOW-USG to investigate the groundwater levels within the Gaza coastal aquifer. Recharge estimation is based on a comprehensive approach including the connection to a surface water model (SWAT) for determining percolation from rainfall as well as detailed approaches regarding further recharge components. An unstructured grid (Voronoi cells) generated by MODFLOW-USG engine was used to reduce run time within complicated aquifer boundary conditions. The results indicate a very good fit between measured and simulated heads. Long-term forecasting (2004-2030) of the groundwater levels was carried out as an essential step to support realistic and sustainable water resources planning and decision making. The increasing built-up area was linked to the potential impacts of urban expansion relating to water supply quantities and groundwater recharge components. The percolation was reduced temporally and spatially in the forecasting period based on the projected built-up area as well as an urban-percolation index. Considering the current management situation, the annual groundwater level correlated negatively with the increasing built-up area; the regression line slope was -0.056 m/km(2) for the average groundwater levels while it became steeper at -0.23 m/km(2) in sensitive locations in the southern part of the Gaza Strip. The groundwater level trend index was developed as a spatial indicator for the appropriate management alternatives that can achieve less negative trend index.

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ABSTRACT:

River basins in or across arid regions have been facing intensified water scarcity and ecological problems, mainly due to the intense irrigated agriculture. Integrating the multiprocesses in hydrological cycle is quite necessary to make reasonable management strategies. In this paper, an integrated multiprocess hydrological model was proposed by coupling river water flow, groundwater flow, canal conveyance, and vadose water flow processes. It was applied to the Zhangye basin of middle Heihe River basin for searching management strategies to restore the ecosystems (i.e., ensure surface runoff into downstream and also recover local groundwater levels). The integrated model was calibrated and validated during 2005-2007 and 2008-2010, respectively. Simulation of groundwater levels (GWLs, 32 wells) and surface runoff both matched well with the observed values, with Nash and Sutcliffe model efficiency > 0.38 and R-2 > 0.57. Then various scenarios were designed with considering five alternatives of different farmland area decrease and three alternatives of groundwater exploitation. Responses of surface runoff and GWLs were predicted for 20 years. Surface runoff change was compared with the water diversion curve, and GWL recovery was also discussed. Results revealed that ecosystems could not be restored with current agricultural area, even shutting down groundwater abstraction for irrigation. A decrease of about 30% of farmland area and using surface river water instead of pumping groundwater for irrigation could satisfy water diversion demand with only a slight GWL decline. Furthermore, the extra irrigation with diverted surface water during nongrowing season could further lead to the recovery of GWLs while without causing negative effects on surface runoff.

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GroMoPo Metadata for Columbia Plateau Regional Aquifer System USGS model
Created: Feb. 6, 2023, 7:12 p.m.
Authors: None · Befus, Kevin M.

ABSTRACT:

Numerical Simulation of Groundwater Flow in the Columbia Plateau Regional Aquifer System, Idaho, Oregon, and Washington By D. Matthew Ely, Erick R. Burns, David S. Morgan, and John J. Vaccaro

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GroMoPo Metadata for Republican River Compact Administration model
Created: Feb. 6, 2023, 7:13 p.m.
Authors: None · Zipper, Samuel C

ABSTRACT:

All input and output available at linked website. Model developed following Supreme Court ruling on allocation of water among Colorado, Nebraska, and Kansas. Originally developed for 1918-2000 period and updated annually. Development team included representatives from each state and federal government. While the core model is MODFLOW, follow-on work has coupled it to agent-based and hydroeconomic models, and perhaps more that I am unaware of.

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GroMoPo Metadata for Manitoba/Winnipeg Model
Created: Feb. 6, 2023, 7:15 p.m.
Authors: None · Grant Ferguson

ABSTRACT:

A three-dimensional density dependent flow and transport model was developed for the Carbonate and Sandstone Aquifers in a 60,000 square-kilometre area of south-central Manitoba. Hydrogeological properties, such as transmissivity, and aquifer response data, were collected for both aquifers. Bayesian Updating was used to determine the heterogeneous transmissivity field of each aquifer. Other parameters were designated based on collected data or typical values from the literature. The resulting model was used to evaluate several water resources scenarios within the Province of Manitoba. The sustainability over 20 years with constant pumping rates was examined. Within both aquifers, hydraulic heads declined in some regions and on average a decline in head was predicted. Model simulations were also conducted to observe the effect of flooding as this is an issue of concern in southern Manitoba. A pseudo-flood was assumed to last for a period of one month. The model was run for a period of 50 years to observe the long-term effects. The solute transport results show a concentration increase in the region south of the City of Winnipeg after one-month, indicating a decline in water quality. Drought simulations were incorporated by reducing recharge rates to the aquifers. The hydraulic heads within the Carbonate Aquifer decline within the Interlake region with a maximum decline within the Sandilands region southeast of the City of Winnipeg. As might be expected, the effects of reduced recharge on the entire aquifer sequence are significant.

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GroMoPo Metadata for Nubian Aquifer System model
Created: Feb. 6, 2023, 7:16 p.m.
Authors: None · Mark Cuthbert

ABSTRACT:

Parsimonious groundwater modeling provides insight into hydrogeologic functioning of the Nubian Aquifer System (NAS), the world's largest non-renewable groundwater system (belonging to Chad, Egypt, Libya, and Sudan). Classical groundwater-resource issues exist (magnitude and lateral extent of drawdown near pumping centers) with joint international management questions regarding transboundary drawdown. Much of NAS is thick, containing a large volume of high-quality groundwater, but receives insignificant recharge, so water-resource availability is time-limited. Informative aquifer data are lacking regarding large-scale response, providing only local-scale information near pumps. Proxy data provide primary underpinning for understanding regional response: Holocene water-table decline from the previous pluvial period, after thousands of years, results in current oasis/sabkha locations where the water table still intersects the ground. Depletion is found to be controlled by two regional parameters, hydraulic diffusivity and vertical anisotropy of permeability. Secondary data that provide insight are drawdowns near pumps and isotope-groundwater ages (million-year-old groundwaters in Egypt). The resultant strong simply structured three-dimensional model representation captures the essence of NAS regional groundwater-flow behavior. Model forecasts inform resource management that transboundary drawdown will likely be minimal-a nonissue-whereas drawdown within pumping centers may become excessive, requiring alternative extraction schemes; correspondingly, significant water-table drawdown may occur in pumping centers co-located with oases, causing oasis loss and environmental impacts.

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GroMoPo Metadata for de Graaf global model
Created: Feb. 6, 2023, 7:17 p.m.
Authors: None · Inge de Graaf

ABSTRACT:

Groundwater is the world's largest accessible source of fresh water. It plays a vital role in satisfying basic needs for drinking water, agriculture and industrial activities. During times of drought groundwater sustains baseflow to rivers and wetlands, thereby supporting ecosystems. Most global-scale hydrological models (GHMs) do not include a groundwater flow component, mainly due to lack of geohydrological data at the global scale. For the simulation of lateral flow and groundwater head dynamics, a realistic physical representation of the groundwater system is needed, especially for GHMs that run at finer resolutions. In this study we present a global-scale groundwater model (run at 6 0 resolution) using MODFLOW to construct an equilibrium water table at its natural state as the result of long-term climatic forcing. The used aquifer schematization and properties are based on available global data sets of lithology and transmissivities combined with the estimated thickness of an upper, unconfined aquifer. This model is forced with outputs from the land-surface PCRaster GlobalWater Balance (PCR-GLOBWB) model, specifically net recharge and surface water levels. A sensitivity analysis, in which the model was run with various parameter settings, showed that variation in saturated conductivity has the largest impact on the groundwater levels simulated. Validation with observed groundwater heads showed that groundwater heads are reasonably well simulated for many regions of the world, especially for sediment basins (R-2 = 0.95). The simulated regional-scale groundwater patterns and flow paths demonstrate the relevance of lateral groundwater flow in GHMs. Inter-basin groundwater flows can be a significant part of a basin's water budget and help to sustain river baseflows, especially during droughts. Also, water availability of larger aquifer systems can be positively affected by additional recharge from inter-basin groundwater flows.

NOTE: Model has global extent, bounding box is positioned over the Atlantic Ocean for visibility.

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GroMoPo Metadata for Santa Barbara USGS SEAWAT model
Created: Feb. 6, 2023, 7:18 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The city of Santa Barbara, in cooperation with the U.S. Geological Survey (USGS) California Water Science Center, developed a three-dimensional density-dependent groundwater-flow and solute-transport model (the Santa Barbara Flow and Transport Model, or SBFTM), based on an existing groundwater-flow model, to simulate seawater intrusion into the Santa Barbara basin under various management strategies. In 2014, California adopted historic legislation to manage its groundwater: the Sustainable Groundwater Management Act (SGMA). Santa Barbara is interested in developing a better understanding of the sustainability of its groundwater supplies to avoid undesirable results: significant and unreasonable groundwater-level declines, reduction in groundwater storage, seawater intrusion, water-quality degradation, land subsidence, and surface-water depletion. The SBFTM uses the USGS code SEAWAT to simulate salinity transport and variable-density flow. The completed SBFTM was coupled with a management optimization tool, Borg, to develop five optimization scenarios that allow the decision makers to evaluate a range of optimal solutions given current water levels and chloride concentrations, and possible future climatic conditions. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20185059)

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GroMoPo Metadata for Lower Bari Doab Canal model
Created: Feb. 6, 2023, 7:19 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Bari Doab on Pakistan side of the border, about 29,000 km2, is one of the most productive agricultural regions in the Sub-continent. The surge in population has increased the competition for available water resources. Ensuing to this, a number of irrigation-related issues have gained prominence. Effects of increasing climate aridity towards lower part of Bari Doab have emerged in the form of accelerated groundwater depletion. Lower Bari Doab Canal (LBDC) command, lying in the centre of Bari Doab, faces maximum spatial climate variability across its command area. This is the first model-based study of the long-term irrigation cost inequities due to successively increasing groundwater depletion towards the tail end. In the model, total water requirements of a grid cell are withdrawn from surface and/or sub-surface sources, based on rainfall and canal water availability. Groundwater pumping estimation is the most complex parameter; crop water deficit approach was adopted for the purpose. Due to excessive groundwater depletion, a tail-end farmer currently incurs 2.19 times higher irrigation costs as compared to the head-end counterpart. An additional depletion of 8-11 m is expected in the lower half of the command till 2031, in contrary to stable conditions in head end. As a result this irrigation cost anomaly is simulated to be further aggravating to 2.36 times in year 2031. Thus, irrigation systems with significant spatial climate variability need appropriate command scale conjunctive management of surface and groundwater by the concerned irrigation planning and management agencies. This would help in plummeting the exacerbating irrigation inequities by reducing waterlogging and groundwater depletion.

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GroMoPo Metadata for Musi Basin model
Created: Feb. 6, 2023, 8:28 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

In general, groundwater flow and transport models are being applied to investigate a wide variety of hydrogeological conditions besides to calculate the rate and direction of movement of groundwater through aquifers and confining units in the subsurface. Transport models estimate the concentration of a chemical in groundwater which requires the development of a calibrated groundwater flow model or, at a minimum, an accurate determination of the velocity and direction of groundwater flow that is based on field data. All the available hydrogeological, geophysical and water quality data in Musi basin, Hyderabad, India, were fed as input to the model to obtain the groundwater flow velocities and the interaction of surface water and groundwater and thereby seepage loss was estimated. This in turn paved the way to calculate the capacity of the storage treatment plants (STP) to be established at the inlets of six major lakes of the basin. The total dissolved solid was given as the pollutant load in the mass transport model, and through model simulation, its migration at present and futuristic scenarios was brought out by groundwater flow and mass transport modeling. The average groundwater velocity estimated through the flow model was 0.26 m/day. The capacities of STP of various lakes in the study area were estimated based on the lake seepage and evaporation loss. Based on the groundwater velocity and TDS as pollutant load in the lakes, the likely contamination from lakes at present and for the next 20 years was predicted.

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GroMoPo Metadata for
Created: Feb. 6, 2023, 8:29 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The application of groundwater resources in Punjab, Pakistan to meet the crop water requirements is increasing rapidly due to constrained surface water supplies. However, the abundant abstraction of groundwater has created serious negative concerns in terms of lowering water table. Thus the sustainability of regional groundwater resources depends upon its proficient management through groundwater modeling technique. Therefore, a research was accomplished to quantify the groundwater pumping and to identify the groundwater depletion areas using MODFLOW model. Three pumping scenarios were developed up to year 2030: such as Scenario-I (Maintaining the current pumping rate for the study period); Scenario-II (Increase in pumping rate according to the historical trend); and Scenario-III (Adjusted canal water supplies and groundwater patterns). The results of Scenario-I indicated that the groundwater level would decline up to 14m for the study period. Scenario-II results showed maximum decline of groundwater level, which would be 18m up to year 2030. The adjusted canal and groundwater supplies among upper and middle part of the study area in Scenario-III, which will recover the groundwater by 2-3m in the middle part of the study area, gave a good management strategy. So, in lower and middle part of study area, groundwater should be artificially recharged and more canal should be supplied water to avoid depletion.

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GroMoPo Metadata for Indus Basin model
Created: Feb. 6, 2023, 8:30 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The exponential increase in groundwater usage over the past few decades in the Punjab province in Pakistan is responsible for the significant groundwater table decline in many parts of the province, leading to an urgent need for policy measures to better manage groundwater use. A better understanding of the underground water balance is necessary for drafting informed groundwater management plans. With limited data, this study develops the first physically-based groundwater model for the entire Punjab province. Using the calibrated provincewide model, simulations are performed to evaluate groundwater dynamics in the future under different scenarios. These scenarios comprise controls on groundwater pumping, canal infrastructure improvements, and precipitation changes. The impacts of these scenarios are highlighted with the mapping of changes in water table, pumping cost, and waterlogged area. The results show that changes in both groundwater abstraction and seepage from the canal system into the aquifer significantly impact groundwater heads, whereas the effect of changing precipitation is negligible. Under status quo conditions, the average provincewide pumping cost is projected to increase by 270% in 23years. The findings emphasize the heterogeneity in groundwater conditions across Punjab and highlight the need for region-specific management of groundwater resources. (C) 2016 American Society of Civil Engineers.

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GroMoPo Metadata for Upper Chaj Doab model
Created: Feb. 6, 2023, 8:31 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A 3-D finite element model (Feflow) has been used for regional groundwater flow modelling of Upper Chaj Doab in Indus Basin, Pakistan. The thematic layers of soils, landuse, hydrology, infrastructure and climate were developed using Geographic Information System (GIS). The numerical groundwater flow model is developed to configure the groundwater equipotential surface, hydraulic head gradient and estimation of the groundwater budget of the aquifer. Integration of GIS with groundwater modelling and satellite remote sensing capabilities has provided an efficient way of analysing and monitoring groundwater status and its associated land conditions. The Arcview GIS software is used as additive tool to develop supportive data for numerical groundwater modelling, integration and presentation of image processing and modelling results. The groundwater behaviour of the regional model shows a gradual decline in watertable from year 1999 onward. The persistent dry condition and high withdrawal rates play an influential role in lowering down the groundwater levels. Different scenarios were developed to study the impact of extreme climatic conditions (drought/flood) and variable groundwater abstraction on the regional groundwater system. The results of the study provide useful information regarding the behaviour of aquifer in order to organize management schemes on local and regional basis to monitor future groundwater development in the area.

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GroMoPo Metadata for Lethbridge-Barons SWAT model
Created: Feb. 6, 2023, 8:32 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Groundwater is a priceless resource in Alberta and therefore, estimating groundwater are crucial to identifying and promoting holistic and integrated management of groundwater-surface water. However, it is a challenge to simulate groundwater storage due to the current rudimentary representation of two-way groundwater-surface water exchange in current hydrologic models, such as Soil and Water Assessment Tool (SWAT), which, in turn, limits our ability to predict land-atmosphere processes and groundwater storage. In this study, we modified the SWAT model to improve module of evapotranspiration in two-way groundwater-surface water exchange. The modified SWAT was calibrated and validated against the groundwater table height and evapotranspiration from 2008 to 2011 period at two location (Lethbridge and Barons) Alberta, Canada. The results showed that the modified SWAT model predicts the groundwater table height very well at both locations. The modified model predicted the daily groundwater table height with R-2 values of 0.86 and 0.89 in the calibration period (2008-2009), 0.81 and 0.83 for the validation period (2010-2011) at Lethbridge and Barons, respectively. The Nash-Sutcliffe model efficiency (NSE) for daily groundwater table height was 0.69 and 0.71 during calibration periods (2008-2009) while the model gives lower values of NSE 0.65 and 0.67 for validation periods (2010-2011) at Lethbridge and Barons, respectively. Similarly, the model estimates evapotranspiration well with correlation coefficient (R-2) of 0.77 during the calibration period and 0.81 for validation period. Our result showed that the modified SWAT model did improve estimates to dynamic groundwater table heights.

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GroMoPo Metadata for Chaudire-Appalaches regional model
Created: Feb. 6, 2023, 8:53 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

As part of the Quebec PACES III provincial groundwater resources assessment programme (Programme d'acquisition des connaissances en eaux souterraines), a regional-scale two-dimensional numerical groundwater model was developed in the Chaudiere-Appalaches region, Quebec, Canada. The model considers groundwater flow, transport of groundwater age and the influence of a fault on the flow system and its implications for groundwater quality. By including deep and shallow flow systems, the study helps fill a knowledge gap with respect to intermediate flow systems and the role they would play during potential energy resource development including shale gas exploitation from the Utica Shale. Physical and chemical hydrogeological data, including an analysis of C-14 in dissolved inorganic carbon in sampled groundwater, supported a regional conceptual flow model forming the basis for numerical simulations. The numerical model is first calibrated to regional piezometry through a semi-automated workflow using the inverse model PEST. Although some evidence for deeper regional flow exists, the area appears to be dominated by local flow systems on maximum length scales of about 5 km, with significant flow through the top 40 to 60 m of the fractured sedimentary rock aquifer. This regional-scale flow model is also supported by the local hydrogeochemical signatures. Simulated mean groundwater ages show young shallow water of <100 years with rapid increases in age with depth suggesting diffusion-controlled age evolution. Groundwater age is likely being perturbed in the vicinity of the Jacques Cartier River fault, which can act as both a barrier and a preferential pathway, provided permeability contrasts with the surrounding rock are at least two orders of magnitude.

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GroMoPo Metadata for Ged Deeble basin model
Created: Feb. 6, 2023, 8:54 p.m.
Authors: None · Befus, Kevin M.

ABSTRACT:

Since the 1970's the Ged Deeble (GD) basin is exploited to supply water to the town of Hargeisa (Somaliland, East Africa, 350,000 inhabitants). The goal of this work is to improve the comprehension of the recharge mechanisms, by the simulation of groundwater flow, in order to assess the sustainability of present-day and future exploitation schemes that aim to satisfy the water demand of the city. For this goal, the exploration activities performed in the past were used to reconstruct the geological framework, the basin shape and the mechanisms of recharge and to define the conceptual model. The mathematical model YAGMod, that simulates groundwater steady flow in presence of head-dependent sources and boundary conditions, was applied to quantify the terms of the groundwater balance. Different management scenarios, accompanied by a sensitivity analysis, have been examined to verify if the future water demand of the city could be satisfied and to provide some indications about the land use planning and the management of water resources.

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GroMoPo Metadata for New Zealand national model
Created: Feb. 6, 2023, 8:55 p.m.
Authors: None · Rogier Westerhoff

ABSTRACT:

Many studies underline the importance of groundwater assessment at the larger, i.e. global, scale. The groundwater models used for these assessments are dedicated to the global scale and therefore not often applied for studies in smaller areas, e.g. catchments, because of their simplifying assumptions. In New Zealand, advanced numerical groundwater flow models have been applied in several catchments. However, that application is piecemeal: only for a limited amount of aquifers and through a variety of groundwater model suites, formats, and developers. Additionally, there are large areas where groundwater models and data are sparse. Hence, an inter-catchment, inter-regional, or nationwide overview of important groundwater information, such as the water table, does not exist. The investment needed to adequately cover New Zealand with high-resolution groundwater models in a consistent approach would be significant and is therefore not considered possible at this stage. This study proposes a solution that obtains a nationwide overview of groundwater that bridges the gap between the (too-) expensive advanced local models and the (too) simple global-scale models. We apply an existing, global-scale, groundwater flow model and improve it by feeding in national input data of New Zealand terrain, geology, and recharge, and by slight adjustment of model parametrisation and model testing. The resulting nationwide maps of hydraulic head and water table depths show that the model points out the main alluvial aquifers with fine spatial detail (200m grid resolution). The national input data and finer spatial detail result in better and more realistic variations of water table depth than the original, global-scale, model outputs. In two regional case studies in New Zealand, the hydraulic head shows excellent correlation with the available groundwater level data. Sensitivity and other analyses of our nationwide water tables show that the model is mostly driven by recharge, model resolution, and elevation (gravity), and impeded by the geology (permeability). The use of this first dedicated New Zealand-wide model can aid in provision of water table estimates in data-sparse regions. The national model can also be used to solve inconsistency of models in areas of trans-boundary aquifers, i.e. aquifers that cover more than one region in New Zealand. Comparison of the models, i.e. the national application (National Water Table model: NWT) with the global model (Equilibrium Water Table model: EWT), shows that most improvement is achieved by feeding in better and higher-resolution input data. The NWT model still has a bias towards shallow water tables (but less than the EWT model because of the finer model resolution), which could only be solved by feeding in a very high resolution terrain model that incorporates drainage features. Although this is a model shortcoming, it can also be viewed as a valuable indicator of the pre-human water table, i.e. before 90% of wetlands were drained for agriculture since European settlement in New Zealand. Calibration to ground-observed water level improves model results but can of course only work where there are such data available. Future research should therefore focus on both model improvements and more data-driven, improved estimation of hydraulic conductivity, recharge, and the digital elevation model. We further surmise that the findings of this study, i.e. successful application of a global-scale model at smaller scales, will lead to subsequent improvement of the global-scale model equations.

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GroMoPo Metadata for Japan creeping landslide model
Created: Feb. 6, 2023, 8:56 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

To predict the movement of an existing creeping landslide, monitoring and analysis of hydrological parameters are crucial. This paper analyses the hydrological parameters of an existing creeping landslide site in western Japan. The groundwater flow and resulting fluctuation in pore water pressure at the slip layer of a sliding block was simulated using a groundwater flow model. A quasi-three-dimensional factor of safety of the block was obtained by combining the groundwater model with slope stability analysis methods. The results show that for prediction purposes at a creeping landslide site the time series analysis using long-term data is of limited use, because the fluctuations of ground surface movement and hydrological parameters are not completely synchronized when the factor of safety of the slope soil is in the creep movement range. The ground surface movement rate dropped after each episode of relatively big movement, even when the hydrological parameters were constant. The factor of safety of the sliding block was more influenced by groundwater recharge from the hills than by rainfall. Pore water pressure fluctuation obtained from groundwater flow model resulting from specific rainfall events indicated better relations between fluctuations in pore water pressure 3 and ground surface movement.

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GroMoPo Metadata for Semarang City model
Created: Feb. 6, 2023, 8:59 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Since 1900, Semarang City has been meeting its industrial water needs by pumping groundwater through its underlying aquifers. The trend toward exploiting groundwater resources has driven the number of deep wells and their production capacity to increase, and therefore leads to the water table to drop from time to time, which has been marked as one of the primary causes of land subsidence there. The main aim of the current study was to numerically model the temporal and spatial evolution of groundwater table under excess abstraction so that a groundwater management strategy can be accordingly drawn up for ensuing the sustainability of groundwater resources in the future. A series of numerical simulations were carried out to take into account hydrogeological data, artificial and natural discharges of deep wells, and boundary effects in Semarang City. The groundwater modeling is calibrated under two flow conditions of the steady state from 1970 to 1990 and the transient state from 1990 to 2005 for six observation wells distributed in Semarang City. Four scenarios that reflect potential management strategies were developed, and then their effectiveness was systematically investigated. The results of our study indicate that the implementation of proper groundwater control management and measure is able to restore the groundwater level to rise back in Semarang City, and in turn achieve the sustainability of groundwater resources.

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GroMoPo Metadata for Jakarta Groundwater Sensitivity Analysis
Created: Feb. 6, 2023, 9 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Location: Jakarta, Indonesia; Bachelor's Thesis focussing on sensitivity analysis.

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GroMoPo Metadata for Nassau County SEAWAT model
Created: Feb. 6, 2023, 9:01 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

A methodology is proposed to define indices for quantifying risks under the threat of reducing in groundwater levels, the existence of saltwater intrusion (SWI), and an increasing nitrate contamination load in submarine groundwater discharge (SGD). The proposed methodology considers coastal regions under geological heterogeneity and it is tested on a groundwater system in Nassau County of Long Island, New York (USA). The numerical model is constructed with the SEAWAT code. The parameter uncertainty of this model is evaluated by coupling the Latin hypercube sampling method (as a sampling algorithm) and Monte Carlo simulation to consider the uncertainty in both hydraulic conductivity and recharge rate. The indices are presented in spatial maps that classify areas of risk to potential threats. The results show that two of the water districts have a high risk under conditions of decreasing groundwater level. Salinity occurs in the southern and southwestern parts of the Nassau County aquifer and a considerable area of high risk of SWI is identified. Furthermore, the average SGD rate with the associated fluxes of nitrate is estimated as 81.4 million m(3)/year (average 0.8 tons of nitrate through SGD per year), which can adversely affect the quality of life in the local coastal ecosystems. The framework developed in this study could help the water district managers to identify high-risk areas for short-term and long-term planning and is applicable to other coastal settings.

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GroMoPo Metadata for Pingtung Coastal Aquifer model
Created: Feb. 6, 2023, 9:02 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

A three-dimensional variable-density finite element model was developed to study the combined effects of overabstraction and seawater intrusion in the Pingtung Plain coastal aquifer system in Taiwan. The model was generated in different layers to represent the three aquifers and two aquitards. Twenty-five multilayer pumping wells were assigned to abstract the groundwater, in addition to 95 observation wells to monitor the groundwater level. The analysis was carried out for a period of 8 years (2008-2015 inclusive). Hydraulic head, soil permeability, and precipitation were assigned as input data together with the pumping records in different layers of the aquifer. The developed numerical model was calibrated against the observed head archives and the calibrated model was used to predict the inland encroachment of seawater in different layers of the aquifer. The effects of pumping rate, sea-level rise, and relocation of wells on seawater intrusion were examined. The results show that all layers of the aquifer system are affected by seawater intrusion; however, the lengths of inland encroachment in the top and bottom aquifers are greater compared with the middle layer. This is the first large-scale finite-element model of the Pingtung Plain, which can be used by decision-makers for sustainable management of groundwater resources and cognizance of seawater intrusion in coastal aquifers.

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GroMoPo Metadata for Lake Chad Basin model
Created: Feb. 6, 2023, 9:03 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

The initial objectives of the efforts portrayed in this report were to (a) integrate all available groundwater data available in the Lake Chad Basin in an updated database; (b) develop an updated and integrative conceptual groundwater model of the Lake Chad Basin, including all old and new information and reflecting the best current understanding, and (c) develop the equivalent numerical groundwater model of the Lake Chad Basin, with emphasis on two focus areas: the Komadougu-Yobe and Chari-Logone river basins, given their relevance for groundwater recharge and use. Even though the overall conceptual model and the numerical model need to be further improved, the basin-wide perspective presented in this work, integrating multiple sources of available data, provides a foundation to better understand and quantify basin-wide hydrogeological dynamics. This enables future efforts to assess potential impacts of future investments and climate futures.

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GroMoPo Metadata for Nile Delta Aquifer model
Created: Feb. 6, 2023, 9:04 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

The Nile Delta Aquifer (NDA) is threatened by salt water intrusion (SWI). This article demonstrates an approach for identifying critical salinity concentration zones using a three-dimensional (3D) variable-density groundwater flow model in the NDA. An innovative procedure is presented for the delineation of salinity concentration in 2010 by testing different simulation periods. The results confirm the presence of saline groundwater caused by SWI in the north of the NDA. In addition, certain regions in the east and southwest of the NDA show increased salinity concentration levels, possibly due to excessive groundwater extraction and dissolution of marine fractured limestone and shale that form the bedrock underlying the aquifer. The research shows that the NDA is still not in a state of dynamic equilibrium. The modeling instrument can be used for simulating future scenarios of SWI to provide a sustainable adaptation plan for groundwater resource.

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GroMoPo Metadata for Variconi Coastal Wetland model
Created: Feb. 6, 2023, 9:05 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Coastal freshwater resources are commonly under high risk of being contaminated from seawater. The main processes that affect seawater intrusion are groundwater overexploitation, land use change, and climate change effects. In this context coastal lagoons represent the more sensitive environments prone to seawater intrusion. Numerical modelling is a useful tool to understand and predict seawater intrusion. In this study, a three-dimensional SEAWAT model is employed to simulate the seawater intrusion to coastal aquifers of Variconi Oasis (Italy). The present simulation was divided into a calibration and a validation model, then the model was used to predict the salinization trend up to 2050. Results show the role of the sea in salinizing the beach front, while the retrodunal environment is characterized by transitional environments. Future seawater intrusion scenarios considering only climate data showed no significative differences in respect to the actual situation. The same happens considering also a low sea level rise prediction. On the contrary, the worst scenario (high sea level rise prediction), depicts a quite different situation, with a saline intrusion in the Variconi oasis that will severely affect the fragile transitional ecosystem. This modelling framework can be used to quantify the effects of climate changes in similar coastal environments.

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GroMoPo Metadata for Great Maputo aquifer model
Created: Feb. 6, 2023, 9:06 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Regional three-dimensional groundwater-flow and saltwater transport models were built to analyse saltwater intrusion in the Great Maputo area, southern Mozambique. Increased water demand has led to many private groundwater abstractions, as the local public water supply network has already reached maximum capacity. Pushing for new strategies to tackle the water-supply shortages exposes the aquifer system to saltwater intrusion from entrapped fossil saline groundwater and seawater. Previous attempts at modelling have been frustrated by data limitations. This study compiled all the available data to build the models, which were subsequently calibrated with observed heads, discharges and salt concentrations. The transport models were used to test hypotheses of potential sources of saltwater resulting in the current salinity distribution. Furthermore, scenarios were simulated to assess the impacts of sea-level rise and projected groundwater abstractions. Results show that saline groundwater is widely distributed in the aquifer's western sector, where it is a limiting factor for groundwater development, and seawater intrusion is a risk along the coastline. Newly constructed wells (46) along the Infulene River can be operated with some impacts of saltwater upconing and must be closely monitored. Although current groundwater abstractions (60,340 m(3)/day) are still small compared with groundwater recharge (980,823 m(3)/day), larger volumes of abstraction are feasible only when using a high number of production wells further away from the city with relatively low yields to avoid saltwater upconing. Capture of fresh groundwater upstream of discharge areas by wells for water supply is possible while maintaining groundwater discharges for groundwater dependent ecosystems.

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GroMoPo Metadata for Dalian City seawater intrusion model
Created: Feb. 6, 2023, 9:07 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Since 1980s, seawater intrusion in coastal aquifers caused by groundwater over-abstraction has led to extensive deterioration in groundwater quality and quantity and has been fazing local residents in Zhoushuizi district of the metropolitan Dalian City in northern China. In this study, a three-dimensional (3D) density-dependent numerical model was constructed to simulate the seawater intrusion process in heterogeneous coastal aquifers in Zhoushuizi district of the metropolitan Dalian City. Considering that the groundwater flow in karst aquifers in northern China is relatively uniform, approximately following Darcy's law, the fracture-karst aquifer in Zhoushuizi district of Dalian City was simplified as an equivalent porous medium. To further identify the hydrogeological parameters of the aquifers in the study area, the model was calibrated and validated using the observation heads and concentrations. Based on the current groundwater abstraction conditions of the study area, the calibrated and validated model was then applied to predict the dynamics and trend of seawater intrusion for the following 30 years from 2010 to 2040 under different rainfall scenarios. The overall extent of seawater intrusion in the future would be even more severe under different prediction scenarios. This 3D seawater intrusion model provides the theoretical basis for implementing a reasonable allocation of groundwater resource, which may significantly affect the sustainability of water resources.

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GroMoPo Metadata for NW Kansas GMD4 SSPA model
Created: Feb. 6, 2023, 9:35 p.m.
Authors: None · Xander Huggins

ABSTRACT:

A re-calibration of the Republican River Compact Administration (RRCA) Groundwater Model only for the northwest Kansas portion of the model. The report misses some essential information (blank answers above), but can be complemented by the original RRCA Groundwater Model's reports/data.

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GroMoPo Metadata for Rapid City area USGS model
Created: Feb. 6, 2023, 9:38 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

The city of Rapid City and other water users in the Rapid City area obtain water supplies from the Minnelusa and Madison aquifers, which are contained in the Minnelusa and Madison hydrogeologic units. A numerical groundwater-flow model of the Minnelusa and Madison hydrogeologic units in the Rapid City area was developed to synthesize estimates of water-budget components and hydraulic properties, and to provide a tool to analyze the effect of additional stress on water-level altitudes within the aquifers and on discharge to springs. This report, prepared in cooperation with the city of Rapid City, documents a numerical groundwater-flow model of the Minnelusa and Madison hydrogeologic units for the 1,000-square-mile study area that includes Rapid City and the surrounding area. Water-table conditions generally exist in outcrop areas of the Minnelusa and Madison hydrogeologic units, which form generally concentric rings that surround the Precambrian core of the uplifted Black Hills. Confined conditions exist east of the water-table areas in the study area. The Minnelusa hydrogeologic unit is 375 to 800 feet (ft) thick in the study area with the more permeable upper part containing predominantly sandstone and the less permeable lower part containing more shale and limestone than the upper part. Shale units in the lower part generally impede flow between the Minnelusa hydrogeologic unit and the underlying Madison hydrogeologic unit; however, fracturing and weathering may result in hydraulic connections in some areas. The Madison hydrogeologic unit is composed of limestone and dolomite that is about 250 to 610 ft thick in the study area, and the upper part contains substantial secondary permeability from solution openings and fractures. Recharge to the Minnelusa and Madison hydrogeologic units is from streamflow loss where streams cross the outcrop and from infiltration of precipitation on the outcrops (areal recharge). MODFLOW-2000, a finite-difference groundwater-flow model, was used to simulate flow in the Minnelusa and Madison hydrogeologic units with five layers. Layer 1 represented the fractured sandstone layers in the upper 250 ft of the Minnelusa hydrogeologic unit, and layer 2 represented the lower part of the Minnelusa hydrogeologic unit. Layer 3 represented the upper 150 ft of the Madison hydrogeologic unit, and layer 4 represented the less permeable lower part. Layer 5 represented an approximation of the underlying Deadwood aquifer to simulate upward flow to the Madison hydrogeologic unit. The finite-difference grid, oriented 23 degrees counterclockwise, included 221 rows and 169 columns with a square cell size of 492.1 ft in the detailed study area that surrounded Rapid City. The northern and southern boundaries for layers 1-4 were represented as no-flow boundaries, and the boundary on the east was represented with head-dependent flow cells. Streamflow recharge was represented with specified-flow cells, and areal recharge to layers 1-4 was represented with a specified-flux boundary. Calibration of the model was accomplished by two simulations: (1) steady-state simulation of average conditions for water years 1988-97 and (2) transient simulations of water years 1988-97 divided into twenty 6-month stress periods. Flow-system components represented in the model include recharge, discharge, and hydraulic properties. The steady-state streamflow recharge rate was 42.2 cubic feet per second (ft3/s), and transient streamflow recharge rates ranged from 14.1 to 102.2 ft3/s. The steady-state areal recharge rate was 20.9 ft3/s, and transient areal recharge rates ranged from 1.1 to 98.4 ft3/s. The upward flow rate from the Deadwood aquifer to the Madison hydrogeologic unit was 6.3 ft3/s. Discharge included springflow, water use, flow to overlying units, and regional outflow. The estimated steady-state springflow of 32.8 ft3/s from seven springs was similar to the simulated springflow of 31.6 ft3/s, which included 20.5 ft3

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GroMoPo Metadata for SW Kansas GMD3 KGS model
Created: Feb. 6, 2023, 9:41 p.m.
Authors: None · Xander Huggins

ABSTRACT:

Ground-water levels have been declining during the last few decades in the Ogallala-High Plains aquifer (HPA) in western Kansas, including within Southwest Kansas Groundwater Management District No. 3 (GMD3). The water-level declines have decreased ground-water discharge to the Arkansas and Cimarron rivers, thereby causing decreasing streamflow. One of the Kansas Water Plan (KWP) objectives is to "Reduce water-level declines rates within the Ogallala aquifer and implement enhanced water management in targeted areas." An associated goal of the KWP is to "Conserve and extend the life of the HPA." As a part of planning and management activities, the Kansas Water Office (under a cooperative agreement with the U.S. Bureau of Reclamation) and GMD3 contracted with the Kansas Geological Survey (KGS) to develop a computer model of the HPA in the GMD3 area to further characterize the hydrologic system and water availability. The model will provide more information on water in storage and allow projection of likely aquifer responses to possible future conditions and management scenarios (KWP, Upper Arkansas River Basin High Priority Issue, Management of the HPA). The KGS constructed a numerical model for a rectangular area of 100 by 150 miles that enclosed GMD3 and extended approximately 6 miles to the north, east, south (into Oklahoma), and west (into Colorado) of the GMD3 boundaries. The active cells included the paleovalley of the Arkansas River in Hamilton and western Kearny counties. The KGS model utilizes MODFLOW, a widely used software program for modeling ground-water flow and stream- aquifer interactions developed by the U.S. Geological Survey. The KWO formed a Technical Advisory Committee to oversee the project, which included staff of the KWO, GMD3, KDA- DWR, and a consulting firm retained by KDA-DWR to provide technical review. The main focus of the project was the development of a calibrated transient model that simulated ground-water flow and stream-aquifer interactions during the period 1947-2007. Predevelopment conditions were simulated for 1944-1946. The model included 12,083 active model cells (each a mile square), involved one layer, and simulated ground-water flow in the HPA and associated alluvial aquifers. Six recharge zones were used and the types of recharge included that from precipitation, enhancement of precipitation recharge in irrigated land, and return recharge below fields irrigated with ground-water and river water diverted from the Arkansas River. The precipitation applied to each cell varied depending on the distribution for each year across the model area. Ground-water pumpage from the HPA for Kansas during 1990-2007 was based on reported water-use records, and for earlier years was estimated from regression equations based on a de-trended ratio of water use/authorized quantity versus precipitation and the Palmer drought severity index for 1990-2007. Similar approaches were applied to estimating pumpage in the Colorado and Oklahoma portions of the model, although the procedures varied because the data and data access for pumping records are not as readily available as those for Kansas. The pumpage rate from the HPA increased from 78,000 acre-ft/yr for predevelopment to a maximum of 2,708,000 acre-ft/yr in 1991 and was 1,844,000 acre-ft/yr for 2007 in the modeled area. The percentage of irrigation return recharge was calculated for each year in Kansas counties based on data for changes in irrigation type and applied to adjacent counties in Colorado and Oklahoma. Results from the calibrated model indicated that the long-term recharge from areal precipitation averaged over the model area was 0.41 in/yr during 1946-2007. Stream-aquifer interactions were simulated for the Arkansas and Cimarron rivers and Crooked Creek. Hydraulic conductivity (K) and specific yield (Sy) were estimated using lithologic data from about 15,000 well logs examined by the KGS PST+ (practical saturated thickness) program. In order to account for the impact of declining water levels on the calculation of K and Sy during the transient period, the calibrated model was broken into six step models: 1) predevelopment, 2) predevelopment to 1966, 3) 1967 to 1976, 4) 1977 to 1986, 5) 1987 to 1996 and 6) 1997 to 2007. In each step model, K and Sy were dynamically updated using the observed water levels for the corresponding time period. During model calibration, the K and Sy values were adjusted by matching streamflows and observed water levels during each step to simulated values. A recharge function with different parameters for each of the six recharge zones was also incorporated into the calibration. The parameter estimation program PEST was employed to optimize parameters during the calibration process. The model indicates that ground-water pumping has caused substantial decreases in aquifer storage. The storage decline rate started to increase in the 1950s, accelerated in the 1960s to mid-1970s, and then approximately leveled from the late 1970s to 2007, although it varied substantially each year depending on pumping. The accumulated decline in ground-water storage simulated for the entire model area for 1947-2007 is 66,409,000 acre-ft, which comprises 29.3% of the simulated predevelopment storage. The storage decreases have been accompanied by a decrease in streamflow out of the model. Water-level declines in the HPA have resulted in the "capture" of ground water that otherwise would have discharged to streams; without this capture, the aquifer storage loss would have been approximately 12% greater than simulated. The total storage volumes simulated for the HPA only within the GMD3 area for predevelopment and the end of 2007 are 193,454,000 and 133,622,000, respectively, giving a storage decline of 59,832,000 acre-ft, which is 30.9% of the predevelopment value. The total storage volumes computed for the GMD3 area from measured water levels are 191,216,000 and 133,726,000 acre-ft for predevelopment and 2007, respectively. These values give a storage decrease of 57,490,000 acre-ft, which is 30.1% of the predevelopment volume. The storage volumes from the model and estimated from observations for the GMD3 area differ by only 1.2% and 0.1% for predevelopment and 2007 conditions. The average water-level decline simulated for all the model cells within the GMD3 area is 69.89 ft in comparison with 67.01 ft for the difference between contoured water-level surfaces based on observations in the predevelopment period to 2007. The calibrated model will be used to simulate ground-water flow and stream-aquifer interactions for future conditions involving continuation and changes in pumping, and different climatic conditions as selected by the KWO and GMD3. A separate report that presents and discusses the results of these scenarios will be prepared.

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GroMoPo Metadata for Ozark Plateau USGS model
Created: Feb. 6, 2023, 9:44 p.m.
Authors: None · Xander Huggins

ABSTRACT:

The study described in this report, initiated by the U.S. Geological Survey in 2014, was designed to evaluate fresh groundwater resources within the Ozark Plateaus, central United States, as an area within a broader national assessment of groundwater availability. The goals of the Ozark study were to evaluate historical effects of human activities on water levels and groundwater availability, quantify groundwater resources now and under probable future pumping and climate conditions, and evaluate existing monitoring networks for their value in making better predictions of future groundwater resources. Previous studies include simulation of local-scale groundwater flow under varying temporal scales, or simulation of the regional system under steady-state conditions. While these studies are useful, particularly for the problem for which they were designed, there is a need to look at the larger regional system under transient conditions to fully evaluate the water resource over time. This study focused on multiple spatial and temporal scales to examine changes in groundwater pumping, storage, and water-level declines. The regional scale provides a broad view of the sources and demands on the system with time. The study area covers approximately 68,000 square miles in the central United States in parts of Missouri, Arkansas, Kansas, and Oklahoma and encompasses the Ozark Plateaus Physiographic Province (Ozark Plateaus), including the Salem Plateau, Springfield Plateau, and Boston Mountains. Groundwater is withdrawn from the Ozark Plateaus aquifer system (Ozark system) for public supply and for domestic, agriculture (including irrigation and aquaculture), livestock, and non-agricultural use (including industrial, thermoelectric power generation, mining, and commercial). The Ozark system provides an important drinking-water supply for people living in the Ozark Plateaus because public supply and domestic use combined constitute the largest groundwater use. Precipitation is the ultimate source of freshwater to the Ozark system; most rainfall occurs during April, May, and June, and precipitation increases generally from north to south across the study area. Groundwater use currently accounts for only 10 percent of the total water use in the areas overlying the Ozark system, but provides a critical drinking-water resource because public supply and domestic groundwater withdrawals are largely from groundwater resources. The 380 million gallons per day of groundwater withdrawn from the Ozark system in 2010 accounts for approximately 2 percent of recharge. Although groundwater use represents a small component of the hydrologic budget, because of low storage in aquifer units, cones of depression with steep water-level gradients can develop quickly around pumping centers. The amount of water entering and leaving the aquifer system from 1900 to about 1965 was relatively constant at a rate of about 13 billion gallons per day (Bgal/d). Much of this inflow of water is discharged through streams in the system to balance the hydrologic budget. Changes in storage over time (from outflows to inflows) reflect the large variability in recharge: if recharge decreases, water levels will decrease, resulting in less groundwater discharge to streams and more water released from aquifer storage. Conversely, when recharge increases, water levels increase, more groundwater discharges to streams, and aquifer storage is replenished. Although pumping generally increased from 1900 to 2016, it does not appear to correlate with the change in storage over the same time period. Regionally, simulated change in groundwater storage corresponds with changes in recharge, more so than with increases in pumping. Average recharge was 11.6 Bgal/d for the period 1900 to 2016. Recharge was generally above average from predevelopment to 1965, followed by a period of below-average recharge from 1965 to about 1980. Recharge remained consistently above average from 1980 to about 1988, after which there was a period of average or below-average recharge, reflected by a decline through the mid-2000s. The implications and potential effects of increased pumping and long-term climate change on the Ozark Plateaus hydrologic system and groundwater availability are a concern for communities and resource managers in the area. Pumping varies from year to year, but is generally expected to moderately increase with population, industrial, and agricultural needs. Most climate models predict warmer minimum and maximum air temperatures by midcentury in the Ozark Plateaus area, especially from midspring through early fall. Three scenarios were developed to simulate possible future conditions from 2016 to 2060 and assess the potential effects on the hydrologic system and availability of water resources. For each scenario, changes in water levels and hydrologic budget components were evaluated from predevelopment (1900) to present (2016) and 45 years into the future (2060). The baseline scenario represents an extension of the average (1996 to 2016) seasonal pumping and recharge values. The pumping scenario is an extension of the average (1996 to 2016) seasonal recharge values with increases in pumping following the historical trend for the period 2016-2060 of up to 120 percent of the 1996 to 2016 average seasonal pumping values. The general circulation model (GCM) scenario is an extension of the average (1996 to 2016) seasonal pumping values and variable recharge based on seasonal averages of soil water storage from a water-balance model using temperature and precipitation from multiple GCMs. The general patterns of water-level decline are similar for each scenario. The areas of water-level decline in southwest Missouri and northeast Oklahoma are only marginally different by 2060 from those of 2009. In one area south of Springfield, Mo., water-level declines are less in the baseline and GCM scenarios than in 2009. This may be the result of a transition from groundwater use to surface-water supplies for a larger percentage of the demand in the area. For all three scenarios, forecasted pumping, recharge, and aquifer properties play an important role in determining the uncertainty of water-level forecasts at 94 real-time observation wells. Simulated aquifer properties in the productive middle and lower Ozark aquifers and the St. Francois confining unit of the Ozark system contribute most to predictive uncertainty in water levels at approximately 35 percent of the real-time observation wells. Out of the 94 real-time observation wells, 82 are developed in the lower Ozark aquifer.

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GroMoPo Metadata for Aberdeen Glacial Aquifer USGS model
Created: Feb. 6, 2023, 9:47 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

The city of Aberdeen, in northeastern South Dakota, requires an expanded and sustainable supply of water to meet current and future demands. Conceptual and numerical models of the glacial aquifer system in the area north of Aberdeen were developed by the U.S. Geological Survey in cooperation with the City of Aberdeen in 2012. The U.S. Geological Survey, in cooperation with the City of Aberdeen, completed a study to revise the original numerical groundwater-flow model using data through water year (WY) 2015 to aid the City of Aberdeen in their development of plans and strategies for a sustainable water supply and to increase understanding of the glacial aquifer system and groundwater-flow system near Aberdeen. The original model was revised to improve the fit between model-simulated values and observed (measured or estimated) data, provide greater insight into surface-water interactions, and improve the usefulness of the model for water-supply planning. The revised groundwater-flow model (hereafter referred to as the revised model) presented in this report supersedes the original model. The purpose of this report is to describe a revised groundwater-flow model including data collection, model calibration, and model results for the glacial aquifer system including the Elm, Middle James, and Deep James aquifers north of Aberdeen, South Dakota, using updated hydrologic data through WY 2015. The original numerical model was revised in several ways. The model was modified by adding four new layers, which included a surficial layer, two intervening confining layers, and a shale bedrock layer. The revised model provides an improved understanding of the groundwater-flow system in comparison to the original model. The principal aquifers of the model area include portions of the Elm, Middle James, and Deep James aquifers. The lithologic information used to define and describe the aquifers in the model area was unaltered; however, aquifer properties and boundary conditions were reviewed and updated using geological information reported by the South Dakota Department of Environmental and Natural Resources and information obtained from geophysical investigations for this study. The horizontal extent of the Elm, Middle James, and Deep James aquifers was unaltered from the original model. The thickness of the Deep James aquifer was modified based on interpretations from the geophysical investigations. In general, groundwater in the Elm aquifer flowed from northwest to southeast and locally towards rivers and streams. Similarly, in the Middle James and Deep James aquifers, groundwater also typically flowed southeast. The revisions made to the original model include use of the following MODFLOW stress packages: Recharge, Evapotranspiration, Time-Variant Specified Head, Wells, Drains, and Stream Flow Routing, all of which were updated from the original model except for the Stream Flow Routing Package, which replaced the River Package used in the original model. Model calibration is the process of estimating model parameters to minimize the differences, or residuals, between observed data and simulated values; therefore, Parameter ESTimation (PEST) software was used to optimize model input parameters by matching model-simulated values to observed data. Calibration parameters included horizontal hydraulic conductivity, vertical hydraulic conductivity, specific yield, specific storage, and vertical streambed conductance for stream and drain cells. Multipliers were used to calibrate the recharge and evapotranspiration stresses. Evapotranspiration extinction depth also was adjusted during model calibration. Comparisons to the original model are described to highlight the changes made in the revised model. In general, the revised model adequately simulates the natural system and compares favorably with observed hydrologic data. Simulated water levels were evaluated by comparing them to single water-level observations at selected well locations. The selected wells were the same wells used in the original model. The coefficient of determination value between simulated and observed water levels for the revised model was 0.89 and included simulated and observed values from October 1, 1974 (WY 1975), through September 30, 2015 (WY 2015). The coefficient of determination value for the original model was 0.94 and included simulated and observed values from October 1, 1974, through September 30, 2009. The difference may indicate that the original model could have been overfit to hydraulic head observations because base flow was not simulated. The additional data used in the revised model included some climatically wetter, more extreme periods, such as 2011, in which annual precipitation was 30.9 inches. Average annual precipitation for the original model timeframe, which included data from WYs 1975-2009, was 20.26 inches. Additional precipitation data for WYs 2010-15, included in the revised model timeframe, resulted in an average annual precipitation for WYs 1975-2015 in the model area of 20.6 inches. The larger variability in climate data coupled with the additional water-level data could explain the lower coefficient of determination for water levels in the revised model. The revised model was used to calculate various groundwater-budget components for steady-state and transient conditions for WYs 1975-2015. The time-variant specified-head cells in the revised model had the largest change when compared to the original steady-state model for inflows and outflows. Comparing the transient budget components between the original and the revised models indicated that inflow from recharge and time-variant specified-head cells had the greatest effect on groundwater inflows, and outflow from storage had the greatest effect on groundwater outflows. The simulated potentiometric contours from the revised model were compared with (1) the observed (interpreted) potentiometric surface (layer 2) and the hydraulic head values (layers 4 and 6) and (2) the simulated contours from the original model. The simulated hydraulic gradients and general direction of groundwater flow in the Elm aquifer in the revised model generally matched the observed potentiometric contours, the simulated potentiometric contours from the original model, and general flow directions interpreted to be perpendicular to the contours. Minor discrepancies between simulated potentiometric contours from the revised model and the observed potentiometric contours may be due to the lack of observed data in the model area. The revised model was designed to reduce the limitations of the original model. The revisions were validated by comparing the results of the original model with the revised model. A primary benefit of the revised model is the inclusion of the surficial deposits and the confining units as explicit layers in the model. The addition of the surficial layer was beneficial for three primary reasons: (1) more accurate representation of recharge from precipitation, (2) more accurate representation of groundwater evapotranspiration, and (3) more accurate representation of groundwater and surface-water interactions. The groundwater model is a numeric approximation of a complex physical hydrologic system, and the revised model data were interpolated in regions with sparse data. Additionally, model discretization included averaged and interpolated values for water use, withdrawal rates, and hydraulic conductivity. The revised model provides a useful estimate for hydraulic gradients, groundwater-flow directions, and aquifer response to groundwater withdrawals.

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GroMoPo Metadata for Canadian Continental Basin Model
Created: Feb. 7, 2023, 1:56 p.m.
Authors: None · Xander Huggins

ABSTRACT:

The development of new, large-scale tools to evaluate water resources is critical to understanding the long-term sustainability of this resource under future land use, climate change, and population growth. In cold and humid regions it is imperative that such tools consider the hydrologic complexities associated with permafrost and groundwater-surface water (GW-SW) interactions, as these factors are recognized to have significant influence on the global water cycle. In this work we present a physics-based, three-dimensional, fully-integrated GW-SW model for Continental Canada constructed with the HydroGeoSphere simulation platform. The Canadian Continental Basin Model (CCBM) domain, which covers approximately 10.5 million km(2), is discretized using an unstructured control-volume finite element mesh that conforms to key river basin boundaries, lakes, and river networks. In order to construct the model, surficial geology maps were assembled, which were combined with near-surface information and bedrock geology into a seven-layer subsurface domain. For the large-scale demonstration, the model was used to simulate historic groundwater levels, surface water flow rates (R-2=0.85), and lake levels (R-2=0.99) across the domain, with results showing that these targets are well reproduced. To demonstrate the regional-scale utility, simulation results were used to perform a regional groundwater flow analysis for western Canada and a water balance analysis for the Laurentian Great Lakes (Superior, Michigan, Huron, Erie and Ontario). The outcome of this work demonstrates that large-scale fully-integrated hydrologic modeling is possible and can be employed to quantify components of a large-scale water balance that are otherwise difficult or impossible to obtain.

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GroMoPo Metadata for Bani River model
Created: Feb. 7, 2023, 1:59 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

The following paper describes the goals and some preliminary work in the Bani sustainability study, an ongoing project in Mali, West Africa. Rural communities in Mali are increasingly relying on hand-pumps, which tap groundwater resources, as a means of obtaining potable water. The long-term sustainable yield of groundwater resources is not known but can be evaluated in sustainability study. In 2005, a groundwater sustainability Study was established along the Bani River of Mali. The Bani study collected groundwater levels that were used in a conceptual groundwater flow model-the Bani model-to develop an understanding of current aquifer conditions and to make limited predictions of sustainability under various future scenarios. The Bani model showed the climatic parameters of recharge (derived from precipitation) and evapotranspiration to influence simulated groundwater levels and groundwater volume available, while increased pumping rates, due to population growth, showed little effect. When considered in the context of the actual Bani sustainability study area, the change in groundwater levels resulting from climatic parameters may have negative implications, especially during several consecutive years of decreased precipitation, such as drought, or if downward trends anticipated for precipitation continue.

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GroMoPo Metadata for Annapolis Valley model
Created: Feb. 7, 2023, 2:25 p.m.
Authors: None · Xander Huggins

ABSTRACT:

The Annapolis-Cornwallis Valley Aquifer Study was a regional hydrogeological study focusing on major aquifer units of the most important agricultural area of Nova Scotia. The study area covered 2100 km2, and included sedimentary rocks of the Wolfville and Blomidon formations, as well as part of the North and South mountains bordering the valley. The surficial sediment cover is mainly composed of glacial tills, but sand and gravel units are also present in the eastern part of the valley. The main objectives of this project were to improve the general understanding of groundwater flow dynamics and to provide baseline information and tools for a regional groundwater resource assessment. The main bedrock aquifers of the Valley are located in the Wolfville and Blomidon formations, which are composed of lenticular bodies of sandstone, conglomerate, shale and siltstone in variable proportions. The aquifers are often confined and the flow is topographically-driven. Their hydraulic conductivities are in the range of 10-6-10-5 m/s. Good aquifers, though limited in extent, can also be found in the sand and gravel units, with hydraulic conductivities on the order of 10-4 m/s. Groundwater recharge was estimated to range between 115 and 224 mm/a over the entire study area. The vulnerability study showed that bedrock aquifers are typically less vulnerable than surficial aquifers, with the Wolfville Formation being the most vulnerable bedrock formation. Groundwater of the Valley is generally of good quality, although nitrate levels are of concern in several areas.

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GroMoPo Metadata for Gilgel-Abay Upper Blue Nile model
Created: Feb. 7, 2023, 2:26 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

Groundwater (GW) is the main source of domestic water supply in Ethiopia (85%), however, despite widespread acknowledgement of its potential for resource-based development and climate change adaptation, the sector is still quite under-investigated. This is mainly due to the scarcity of in situ data, which are essential to building robust impact models. To address this, we developed a fine-resolution (500 m) GW model using MODFLOW-NWT, focusing on the Gilgel-Abay Catchment located in the Upper Blue Nile basin, fed with daily distributed input forcings of recharge and streamflow simulated by the Coupled Routing and Excess Storage (CREST) hydrological model. The model was calibrated against instantaneous observation records of GW table for 38 historical wells, and validated at selected sites using time series data collected from the Citizen Science Initiative (PIRE CSI), and the Innovation Lab for Small Scale Irrigation (ILSSI) project. An RMSE of 14.4 m (1.8% of range) was achieved for calibration and same for validation was 18.21 m and 15.76 mat the PIRE CSI and ILSSI sites, respectively. The findings of this research indicate substantial physical GW resource availability in the Gilgel-Abay region. Moreover, we expect the model to have multiscale future applications. These include obtaining dynamically downscaled boundary conditions for a local-scale GW model, to be developed in the next phase of our research. Further, an upscaled version of this model to encompass the entire Tana Basin would be developed to simulate lake-aquifer interactions. Finally, the approach of this research combining different types of datasets (e.g., reanalysis products, satellite data, citizen science data, etc.) is adaptable to other global data-scarce regions. Moreover, the method overcomes specific challenges associated to in situ data scarcity, limited knowledge on GW resources availability in the area, interaction with complex boundary conditions, and sensitivity under meteorological boundary forcings.

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GroMoPo Metadata for Korba Aquifer Zghibi model
Created: Feb. 7, 2023, 2:28 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Tunisia relies extensively on coastal groundwater resources that are pumped at unsustainable rates to support irrigated agriculture, causing groundwater drawdown and water quality problems due to seawater intrusion. It is imperative for the country to regulate future groundwater allocations and implement conservation strategies based on robust hydrogeological assessments to alleviate the adverse impacts of groundwater depletion. We developed a 3D transient density-dependent groundwater model by coupling MODFLOW-2000 and MT3DMS to improve understanding of seawater intrusion into the Korba aquifer in Tunisia. Results indicate that groundwater overexploitation since 1965 induced 5.15 Mm(3)/year of seawater inflow while reducing submarine discharge into the sea by about 9.74 Mm(3)/year as compared to the steady state water budget in 1965. Projecting withdrawals from 2014 up to 2050 results in a slow but extensive groundwater table decline forming a cone of depression 15 m below sea level. The seawater wedge under this business-as-usual scenario is expected to reach 1.8 km from the shoreline, causing significant mixing of the TDS-rich seawater in the aquifer system. The cone of depression under a 25% increase in groundwater withdrawal drops to about 20 m below sea level while the saltwater front reaches 2.5 km inland. Countering the seawater intrusion problem requires reducing groundwater pumping by 17 Mm(3)/year to push back the saltwater front along the coastline by about 25% over a 43-year period. Application of the presented generic groundwater simulation framework guides developing management strategies to mitigate seawater intrusion in the Korba coastal aquifer and similar areas.

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GroMoPo Metadata for Netherlands Hydrological Instrument
Created: Feb. 7, 2023, 2:29 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Water management in the Netherlands applies to a dense network of surface waters for discharge, storage and distribution, serving highly valuable land-use. National and regional water authorities develop long-term plans for sustainable water use and safety under changing climate conditions. The decisions about investments on adaptive measures are based on analysis supported by the Netherlands Hydrological Instrument NHI based on the best available data and state-of-the-art technology and developed through collaboration between national research institutes. The NHI consists of various physical models at appropriate temporal and spatial scales for all parts of the water system. Intelligent connectors provide transfer between different scales and fast computation, by coupling model codes at a deep level in software. A workflow and version management system guarantees consistency in the data, software, computations and results. The NHI is freely available to hydrologists via an open web interface that enables exchange of all data and tools. (C) 2014 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).

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GroMoPo Metadata for Guarani Aquifer System model
Created: Feb. 7, 2023, 2:31 p.m.
Authors: None · David Serrano

ABSTRACT:

The Guarani Aquifer System (GAS) is a strategic transboundary aquifer system shared by Brazil, Argentina, Paraguay and Uruguay. This article presents a groundwater flow model to assess the GAS system in terms of regional flow patterns, water balance and overall recharge. Despite the continental dimension of GAS, groundwater recharge is restricted to narrow outcrop zones. An important part is discharged into local watersheds, whereas a minor amount reaches the confined part. A three-dimensional finite element groundwater-flow model of the entire GAS system was constructed to obtain a better understanding of the prevailing flow dynamics and more reliable estimates of groundwater recharge. Our results show that recharge rates effectively contributing to the regional GAS water balance are only approximately 0.6 km(3)/year (about 4.9 mm/year). These rates are much smaller than previous estimates, including of deep recharge approximations commonly used for water resources management. Higher recharge rates were also not compatible with known(81)Kr groundwater age estimates, as well as with calculated residence times using a particle tracking algorithm.

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GroMoPo Metadata for El Carrasco landfill model
Created: Feb. 7, 2023, 2:32 p.m.
Authors: None · David Serrano

ABSTRACT:

The poor management of the leachates generated at the solid waste final disposal site in El Carrasco, Bucaramanga, Colombia, has been worrying environmental authorities for some years because its risk of contamination for the soil and the water in the disposal and closed areas. Objective. To establish the migration route for the leachates generated in El Carrasco landfill, in Bucaramanga, and in the direct and indirect areas of influence of the disposal site, by means of the analysis and the interpretation of the data obtained by the use of geoelectric units. Materials and methods. IT tools were used, including geographic information systems, the Modelmouse software, 180 meters deep vertical electrical soundings with a mesh modeling model comprised of 45 lines and 35 columns -10x10m- and six layers that met the units identified in the direct disposal area by means of a stratigraphic profile. Results. The results of the modeling developed within the MODFLOW environment show an East-West flow in most of the layers. The same happens with the flow established by the load coming from the Santander mountain range, where the resistivity rates are very low. Conclusion. Low resistivity zones associated, generated by the leachates, and fully saturated zones that were poorly managed in the disposal site, were identified for the area studied, by means of methodologies that combine geophysics, geology, hydrogeology and geochemistry.

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GroMoPo Metadata for Elkhorn/Loup USGS model
Created: Feb. 7, 2023, 2:33 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

The U.S. Geological Survey, in cooperation with the Lewis and Clark, Lower Elkhorn, Lower Loup, Lower Platte North, Lower Niobrara, Middle Niobrara, Upper Elkhorn, and the Upper Loup Natural Resources Districts, designed a study to refine the spatial and temporal discretization of a previously modeled area. This updated study focused on a 30,000-square-mile area of the High Plains aquifer and constructed regional groundwater-flow models to evaluate the effects of groundwater withdrawal on stream base flow in the Elkhorn and Loup River Basins, Nebraska. The model was calibrated to match groundwater-level and base-flow data from the stream-aquifer system from pre-1940 through 2010 (including predevelopment [pre-1895], early development [1895-1940], and historical development [1940 through 2010] conditions) using an automated parameter-estimation method. The calibrated model then was used to simulate hypothetical development conditions (2011 through 2060). Predicted changes to stream base flow based on simulated changes to groundwater withdrawal will aid in developing strategies for management of hydrologically connected water supplies. Additional wells were simulated throughout the model domain and pumped for 50 years to assess the effect of wells on aquifer depletions, including stream base flow. The percentage of withdrawal for each well after 50 years, which was compensated by aquifer reductions to stream base flow, storage, or evapotranspiration, was computed and mapped. These depletions are influenced by aquifer properties, time, and distance from the well. Stream base-flow depletion results showed that the closer the added well was to a stream, the greatest the effect on the stream base flow. Areas of stream base-flow depletion percentages greater than 80 percent were generally within 1 mile (mi) from the stream. The distance increased to 6 mi near the confluence of the Dismal and Middle Loup Rivers, and the North Loup and Calamus Rivers. The percentage of stream base-flow depletion decreased as the distance from the stream increased. Areas more than 10 mi from the stream generally had a stream base-flow depletion of 10 percent or less. Evapotranspiration depletion was largest in areas closest to streams, specifically in the Elkhorn River watershed. It was also larger in areas of interdunal wetlands within the Sand Hills. Evapotranspiration depletion was negligible in areas greater than 5 mi from a stream, with the exception of interdunal areas in Cherry, Grant, and Arthur Counties. The storage depletion percentage increased as the distance from a stream increased. Storage depletion was largest in areas between streams. Areas experiencing the smallest amount of storage depletion were adjacent to streams. Calibrated model outputs and streamflow depletion analysis are publicly available online. Accuracy of the simulations is affected by input data limitations, system simplifications, assumptions, and resources available at the time of the simulation construction and calibration. Most of the important limitations relate either to data used as simulation inputs or to data used to estimate simulation inputs. Development of the regional simulations focused on generalized hydrogeologic characteristics within the study area and did not attempt to describe variations important to local-scale conditions. These simulations are most appropriate for analyzing groundwater-management scenarios for large areas and during long periods and are not suitable for analysis of small areas or short periods.

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GroMoPo Metadata for Ozark Plateau aquifer USGS model
Created: Feb. 7, 2023, 2:35 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

To assess the effect that increased water use is having on the long-term availability of groundwater within the Ozark Plateaus aquifer system, a groundwater-flow model was developed using MODFLOW 2000 for a model area covering 7,340 square miles for parts of Arkansas, Kansas, Missouri, and Oklahoma. Vertically the model is divided into five units. From top to bottom these units of variable thickness are: the Western Interior Plains confining unit, the Springfield Plateau aquifer, the Ozark confining unit, the Ozark aquifer, and the St. Francois confining unit. Large mined zones contained within the Springfield Plateau aquifer are represented in the model as extensive voids with orders-of-magnitude larger hydraulic conductivity than the adjacent nonmined zones. Water-use data were compiled for the period 1960 to 2006, with the most complete data sets available for the period 1985 to 2006. In 2006, total water use from the Ozark aquifer for Missouri was 87 percent (8,531,520 cubic feet per day) of the total pumped from the Ozark aquifer, with Kansas at 7 percent (727,452 cubic feet per day), and Oklahoma at 6 percent (551,408 cubic feet per day); water use for Arkansas within the model area was minor. Water use in the model from the Springfield Plateau aquifer in 2005 was specified from reported and estimated values as 569,047 cubic feet per day. Calibration of the model was made against average water-level altitudes in the Ozark aquifer for the period 1980 to 1989 and against waterlevel altitudes obtained in 2006 for the Springfield Plateau and Ozark aquifers. Error in simulating water-level altitudes was largest where water-level altitude gradients were largest, particularly near large cones of depression. Groundwater flow within the model area occurs generally from the highlands of the Springfield Plateau in southwestern Missouri toward the west, with localized flow occurring towards rivers and pumping centers including the five largest pumping centers near Joplin, Missouri; Carthage, Missouri; Noel, Missouri; Pittsburg, Kansas; and Miami, Oklahoma. Hypothetical scenarios involving various increases in groundwater-pumping rates were analyzed with the calibrated groundwater-flow model to assess changes in the flow system from 2007 to the year 2057. Pumping rates were increased between 0 and 4 percent per year starting with the 2006 rates for all wells in the model. Sustained pumping at 2006 rates was feasible at the five pumping centers until 2057; however, increases in pumping resulted in dewatering the aquifer and thus pumpage increases were not sustainable in Carthage and Noel for the 1 percent per year pumpage increase and greater hypothetical scenarios, and in Joplin and Miami for the 4 percent per year pumpage increase hypothetical scenarios. Zone-budget analyses were performed to assess the groundwater flow into and out of three zones specified within the Ozark-aquifer layer of the model. The three zones represented the model part of the Ozark aquifer in Kansas (zone 1), Oklahoma (zone 2), and Missouri and Arkansas (zone 3). Groundwater pumping causes substantial reductions in water in storage and induces flow through the Ozark confining unit for all hypothetical scenarios evaluated. Net simulated flow in 2057 from Kansas (zone 1) to Missouri (zone 3) ranges from 74,044 cubic feet per day for 2006 pumping rates (hypothetical scenario 1) to 625,319 cubic feet per day for a 4 percent increase in pumping per year (hypothetical scenario 5). Pumping from wells completed in the Ozark aquifer is the largest component of flow out of zone 3 in Missouri and Arkansas, and varies between 88 to 91 percent of the total flow out of zone 3 for all of the hypothetical scenarios. The largest component of flow into Oklahoma (zone 2) comes from the overlying Ozark confining unit, which is consistently about 45 percent of the total. Flow from the release of water in storage, from general-head boundaries, and from zones 1 and 3 is considerably smaller values that range from 3 to 22 percent of the total flow into zone 2. The largest flow out of the Oklahoma part of the model occurs from pumping from wells and ranges from 52 to 69 percent of the total.

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GroMoPo Metadata for Kansas GMD5 Balleau model
Created: Feb. 7, 2023, 2:36 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

HYDROLOGIC MODEL OF BIG BEND GROUNDWATER MANAGEMENT DISTRICT NO. 5

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GroMoPo Metadata for Llamara Salt Flat model
Created: Feb. 7, 2023, 2:46 p.m.
Authors: None · David Serrano

ABSTRACT:

The Propopis tamarugo Phil, also known as Tamarugo, is an endemic and protected tree that survives in the Atacama Desert-a hyper arid and highly saline environment. The Tamarugo is threatened because of groundwater overexploitation, and its preservation depends on the soil moisture in the vadose zone, as many of the tree roots do not reach the current water table levels. To improve the estimation of soil moisture available for the Tamarugo trees, we applied a hydrogeological model that couples the unsaturated and saturated zones. The model was used to represent different groundwater exploitation and recharge scenarios between February 2006 and September 2030 to predict simultaneously groundwater levels and soil moisture. The model results show that even at locations where water table depletion is relatively small (1-1.5 m), soil moisture can drastically decrease (0.25-0.30 m(3)/m(3)). Therefore, Tamarugo survival can be better addressed, as the applied model provides a management tool to estimate response of Tamarugo trees to changing soil moisture. To further improve the model and its use to assess Tamarugo survival, more field data, such as soil hydrodynamic properties and soil moisture, should be collected. Additionally, relationships between the state of the Tamarugo trees and soil moisture should be further constructed. In this way, the developed model will be able to predict future conditions associated to the Tamarugo's health state.

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GroMoPo Metadata for Big Sioux Aquifer USGS model
Created: Feb. 7, 2023, 2:48 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

The city of Sioux Falls, in southeastern South Dakota, is the largest city in South Dakota. The U.S. Geological Survey (USGS), in cooperation with the city of Sioux Falls, completed a groundwater-flow model to use for improving the understanding of groundwater-flow processes, estimating hydrogeologic properties, and analyzing groundwater and surface-water interactions for the Big Sioux aquifer in the model area. The model area includes the Big Sioux aquifer and the underlying hydrogeologic units from Dell Rapids, South Dakota, to the confluence of the Big Sioux River and the outlet of the Sioux Falls Diversion Channel in eastern Sioux Falls, S. Dak. The Big Sioux aquifer is the primary aquifer in the model area and the focus of the groundwater-flow model. The Big Sioux River is the largest stream in the model area and is in hydraulic connection with the Big Sioux aquifer. A conceptual model for the area was constructed and includes a characterization of the hydrogeologic framework, analysis and construction of potentiometric surfaces, and summary of estimated water budget components in the model area. The primary hydrogeologic units in the model area consist of (1) the Big Sioux aquifer, (2) a glacial till confining unit, and (3) bedrock aquifers (Split Rock Creek and Sioux Quartzite aquifers). Sources of groundwater recharge included infiltration of precipitation, stream seepage, and groundwater exchanges among the hydraulically connected Big Sioux aquifer, glacial till confining unit, and bedrock aquifers. Groundwater losses included evapotranspiration, groundwater discharge to streams, and groundwater withdrawal to supply water-use needs. A numerical groundwater-flow model (numerical model) was constructed and was used to simulate all aspects of the conceptual model for predevelopment (steady-state) and time-varying (transient) monthly conditions for 1950-2017. The numerical model was constructed using the USGS modular hydrologic simulation program, MODFLOW-6, and was calibrated using the Parameter ESTimation software, PEST++. The transient numerical model was calibrated for steady-state and transient monthly conditions for 1950-2017. Calibration targets were observations of hydraulic head, changes in hydraulic head, monthly mean streamflow (as a rate), and cumulative monthly stream discharge (as a volume). Parameters adjusted during model calibration were horizontal and vertical hydraulic conductivity, specific storage, specific yield, recharge and evapotranspiration multipliers, and streambed hydraulic conductivity. Horizontal and vertical hydraulic conductivity were estimated at pilot points distributed within the model area; specific storage and specific yield were assigned to uniform values in each layer in the model area; recharge and evapotranspiration multipliers were assigned uniformly for every stress period in the numerical model; and streambed hydraulic conductivity values were assigned uniformly between stream confluences. The final calibrated parameter values of horizontal and vertical hydraulic conductivity, specific yield, specific storage, streambed hydraulic conductivity, recharge, and evapotranspiration were considered reasonable for the hydrogeologic materials and conditions in the model area for 1950-2017. Overall, simulated hydraulic head altitudes had a linear regression coefficient of determination (R2) of 0.48. Hydraulic head altitude residuals for the glacial till confining unit and bedrock aquifers were typically greater in magnitude when compared to residuals in the Big Sioux aquifer, but simulated hydraulic head altitudes in the Big Sioux aquifer compared favorably with mean observed hydraulic head altitudes and had a linear regression R2 of 0.93. Simulated streamflow hydrographs matched the general trends of observed increases and decreases in streamflow for USGS streamgages 06482000 (Big Sioux River at Sioux Falls, S. Dak.) and 06482020 (Big Sioux River at North Cliff Avenue at Sioux Falls, S. Dak.), but larger streamflows were overestimated at the first streamgage and underestimated at the second streamgage. The numerical model reasonably estimated cumulative monthly stream discharge for the first 10-15 years of available streamflow records at both USGS streamgages. After the first 10-15 years of available streamflow record, cumulative monthly stream discharge was closely estimated for USGS streamgage 06482000 and underestimated at USGS streamgage 06482020. Composite sensitivities without regularization were calculated by PEST++ for the calibrated numerical model parameters and were averaged by parameter group. The parameter group with the highest mean composite sensitivity was the recharge multiplier parameter group. Model simplifications, assumptions, and limitations were necessary for construction of the conceptual and numerical models and for calibration efficiency. Spatial simplification of hydraulic properties could cause the numerical model to misrepresent reactions to changes in localized stresses, such as additional demands for groundwater withdrawal. The numerical model was temporally discretized into monthly periods and required scaling daily rates into representative monthly rates for model input and calibration targets. Based on the comparison between the observed and simulated groundwater levels, monthly mean streamflow and cumulative monthly stream discharge, and general groundwater distribution and flow, the numerical model favorably simulated the flow in the Big Sioux aquifer. Eventual capture was calculated in the model area using a steady-state numerical groundwater-flow model. The eventual capture map shows areas of higher streamflow capture adjacent to the Big Sioux River north of the city of Sioux Falls and along the lower part of the Sioux Falls Diversion Channel, and areas of lower streamflow capture along aquifer boundaries and near the southern Sioux Quartzite barrier. The timing of capture was determined using a transient numerical groundwater-flow model to determine the likely captured water sources for 30 years of groundwater withdrawal at three hypothetical wells using three continuous withdrawal rates (112.5, 450.0, and 900.0 gallons per minute). Supply for all three hypothetical wells became capture-dominated after only a short period of continuous withdrawal. Capture stabilized after about 10-15 years for well A, and after 20-25 years for well B, and after about 10-15 years for well C. The groundwater-flow model is a suitable tool to use for improving the understanding of groundwater-flow processes, estimating hydrogeologic properties, and analyzing groundwater and surface-water interactions for the Big Sioux aquifer near Sioux Falls, S. Dak. The numerical model can be used to simulate hydrologic scenarios, advance understanding of groundwater budgets, compute system response to stress, and determine likely sources of water supplied to wells.

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GroMoPo Metadata for Lake Michigan Basin unstructured grid USGS model
Created: Feb. 7, 2023, 2:49 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

In order to better represent the configuration of the stream network and simulate local groundwater-surface water interactions, a version of MODFLOW with refined spacing in the topmost layer was applied to a Lake Michigan Basin (LMB) regional groundwaterflow model developed by the U. S. Geological. Regional MODFLOW models commonly use coarse grids over large areas; this coarse spacing precludes model application to local management issues (e. g., surface-water depletion by wells) without recourse to labor-intensive inset models. Implementation of an unstructured formulation within the MODFLOW framework (MODFLOW-USG) allows application of regional models to address local problems. A "semi-structured" approach (uniform lateral spacing within layers, different lateral spacing among layers) was tested using the LMB regional model. The parent 20-layer model with uniform 5000-foot (1524-m) lateral spacing was converted to 4 layers with 500-foot (152-m) spacing in the top glacial (Quaternary) layer, where surface water features are located, overlying coarser resolution layers representing deeper deposits. This semi-structured version of the LMB model reproduces regional flow conditions, whereas the finer resolution in the top layer improves the accuracy of the simulated response of surface water to shallow wells. One application of the semi-structured LMB model is to provide statistical measures of the correlation between modeled inputs and the simulated amount of water that wells derive from local surface water. The relations identified in this paper serve as the basis for metamodels to predict (with uncertainty) surface-water depletion in response to shallow pumping within and potentially beyond the modeled area, see Fienen et al. (2015a).

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GroMoPo Metadata for Central Kalahari Basin integrated hydrological model
Created: Feb. 7, 2023, 2:50 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

Distributed numerical models, considered as optimal tools for groundwater resources management, have always been constrained by availability of spatio-temporal input data. This problem is particularly distinct in arid and semi-arid developing countries, characterized by large spatio-temporal variability of water fluxes but scarce ground-based monitoring networks. That problem can be mitigated by remote sensing (RS) methods, which nowadays are applicable for modelling not only surface-water but also groundwater resources, through rapidly increasing applications of integrated hydrological models (IHMs). This study shows implementation of various RS products in the IHM of the Central Kalahari Basin (similar to 200 Mm(2)) multi-layered aquifer system, characterized by semi-arid climate and thick unsaturated zone, both enhancing evapotranspiration. The MODFLOW-NWT model with UZF1 package, accounting for variably saturated flow, was set up and calibrated in transient conditions throughout 13.5 years using borehole hydraulic heads as state variables and RS-based daily rainfall and potential evapotranspiration as driving forces. Other RS input data included: digital-elevation-model, land-use/land-cover and soils datasets. The model characterized spatio-temporal water flux dynamics, providing 13-year (2002-2014) daily and annual water balances, thereby evaluating groundwater-resource dynamics and replenishment. The balances showed the dominant role of evapotranspiration in restricting gross recharge to only a few mm yr(-1) and typically negative net recharge (median,-1.5 mm yr(-1)), varying from -3.6 (2013) to +3.0 (2006) mm yr(-1) (rainfall of 287 and 664 mm yr(-1) respectively) and implying systematic water-table decline. The rainfall, surface morphology, unsaturated zone thickness and vegetation type/density were primary determinants of the spatio-temporal net recharge distribution.

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GroMoPo Metadata for East African Rift Valley integrated model
Created: Feb. 7, 2023, 6:03 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

Study region: East African Rift Valley basin. Study focus: Water availability in the rift valley relies heavily on the discharge from the highlands to rivers that run to the rift floor. This research explores the effect of Land use/Land cover (LULC) and climate change on water yield and groundwater recharge (WYGR) using coupled SWAT-MODFLOW, which integrates Soil and Water Assessment Tool (SWAT) and Newton Modular Finite Difference Groundwater Flow (MODFLOW-NWT). The LULC change was analyzed using artificial neural network-based cellular automata. New hydrological insights: The dominant LULC is cultivated land and expanded by 5% to the forest and grassland areas. The average temperature and precipitation are expected to rise by 8-11% and 3-6%, respectively. Climate change affects the spatiotemporal distribution of WYGR significantly, while LULC change has a trivial effect. Under the baseline scenario, the recharge was 10% of the average annual precipitation, but climate change is projected to reduce it by 47-53%. Water yield reduction up to 48% and change of perennial rivers to intermittent are expected in the coming decades. The region will experience water scarcity, emerging mainly from climate change.

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GroMoPo Metadata for Little Plover River USGS model
Created: Feb. 7, 2023, 6:05 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Groundwater models often serve as management tools to evaluate competing water uses including ecosystems, irrigated agriculture, industry, municipal supply, and others. Depletion potential mapping-showing the model-calculated potential impacts that wells have on stream baseflow-can form the basis for multiple potential management approaches in an oversubscribed basin. Specific management approaches can include scenarios proposed by stakeholders, systematic changes in well pumping based on depletion potential, and formal constrained optimization, which can be used to quantify the tradeoff between water use and stream baseflow. Variables such as the maximum amount of reduction allowed in each well and various groupings of wells using, for example, K-means clustering considering spatial proximity and depletion potential are considered. These approaches provide a potential starting point and guidance for resource managers and stakeholders to make decisions about groundwater management in a basin, spreading responsibility in different ways. We illustrate these approaches in the Little Plover River basin in central Wisconsin, United States-home to a rich agricultural tradition, with farmland and urban areas both in close proximity to a groundwater-dependent trout stream. Groundwater withdrawals have reduced baseflow supplying the Little Plover River below a legally established minimum. The techniques in this work were developed in response to engaged stakeholders with various interests and goals for the basin. They sought to develop a collaborative management plan at a watershed scale that restores the flow rate in the river in a manner that incorporates principles of shared governance and results in effective and minimally disruptive changes in groundwater extraction practices.

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GroMoPo Metadata for Atlantis aquifer MODFLOW model
Created: Feb. 7, 2023, 6:06 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

The Atlantis Water Supply Scheme (AWSS, Western Cape, South Africa) has been in operation for about 40 years as a means to supply and augment drinking water to the town of Atlantis via managed aquifer recharge (MAR). In this study, the numerical model MODFLOW for groundwater flow and contaminant transport was used in support of the management of the AWSS. The aims were: (i) to calibrate the MODFLOW model for the MAR site at Atlantis; (ii) to run realistic scenarios that cannot be replicated through experiments; and (iii) to make recommendations in support of efficient and sustainable management of the aquifer. MODFLOW was calibrated through comparison of observed and simulated groundwater levels (R-2 between 0.663 and 0.995). Scenario simulations indicated possible drawdowns between < 5 m (low groundwater abstraction and low artificial recharge of groundwater through infiltration basins) and > 20 m (high abstraction and high artificial recharge) at localized areas of the Witzand wellfield. At Silwerstroom, large drawdown levels were not predicted to occur, so this wellfield could be exploited more without affecting the sustainability of the groundwater resource. Groundwater moves from the infiltration basins towards the Witzand wellfield at a rate of 120-150 m.a(-1). The modelling results supported recommendations for balancing groundwater abstraction and artificial recharge volumes, monitoring the water balance components of the system, the potential risks of groundwater contamination and the delineation of groundwater protection zones.

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GroMoPo Metadata for Bad River Watershed model
Created: Feb. 7, 2023, 6:09 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

A groundwater-flow model was developed for the Bad River Watershed and surrounding area by using the U.S. Geological Survey (USGS) finite-difference code MODFLOW-NWT. The model simulates steady-state groundwater-flow and base flow in streams by using the streamflow routing (SFR) package. The objectives of this study were to: (1) develop an improved understanding of the groundwater-flow system in the Bad River Watershed at the regional scale, including the sources of water to the Bad River Band of Lake Superior Chippewa Reservation (Reservation) and groundwater/surface-water interactions; (2) provide a quantitative platform for evaluating future impacts to the watershed, which can be used as a starting point for more detailed investigations at the local scale; and (3) identify areas where more data are needed. This report describes the construction and calibration of the groundwater-flow model that was subsequently used for analyzing potential locations for the collection of additional field data, including new observations of water-table elevation for refining the conceptualization and corresponding numerical model of the hydrogeologic system. The study area can be conceptually divided into three primary hydrogeologic environments. The first encompasses the southern uplands with relatively low topographic relief, where groundwater-flow is unconfined and occurs primarily in sandy till and glacial outwash overlying Archean-aged crystalline bedrock. The second includes a transitional area of higher topographic relief and shallow depth to bedrock, in the vicinity of ridges formed by steeply dipping, early-Proterozoic aged metasedimentary units of the Marquette Range Supergroup (including the Ironwood Formation), and late-Proterozoic igneous units associated with the Midcontinent Rift System (MRS). Groundwater-flow in this area likely occurs primarily through connected networks of bedrock fractures that are not well characterized, and also in isolated pockets of Quaternary deposits. The third and last hydrogeologic environment includes lowlands along Lake Superior where a deep sandstone aquifer is confined by thick deposits of clay-rich till. Model input was compiled by using both published and unpublished data. Constant flux boundary conditions for the model perimeter were developed from a regional analytic element model described in appendix 1 of this report. Pumping from 26 high-capacity wells within the model area was included. The SFR stream network was developed from the National Hydrography Dataset (NHDPlus Version 2) and hydrography from the Wisconsin Department of Natural Resources (WDNR). Hydraulic conductivity values were determined for each model cell by interpolation from a network of pilot points, within zones representing major hydrogeologic units. Recharge to the groundwater system was estimated on a cell-by-cell basis by using the Soil Water Balance code (SWB), with gridded daily temperature and precipitation data for the period 1980-2011, and GIS coverages of soil and land-surface conditions. Estimated recharge varies considerably, following spatial patterns in the precipitation and soil hydrologic group inputs. The lowest recharge values occur in the Superior lowlands, whereas the highest values occur in the upland areas, especially those underlain by sandy soils, and in the vicinity of bedrock hills. The model was calibrated to groundwater-levels and base flows obtained from the USGS National Water Information System (NWIS) database, and groundwater-levels obtained from the WDNR and Band River Band well-construction databases. Calibration was performed via nonlinear regression by using the parameter-estimation software suite PEST. Groundwater levels and base-flow observations in the calibration dataset were well simulated by the calibrated model, with reasonable values of hydraulic conductivity. The pilot-point parameters that were most constrained by observations during model calibration coincided with the locations containing the most wells (head observations) especially the population centers of Ashland, Mellen, and other communities along the major highway corridors. Results from the calibrated model illustrate differences in the nature of groundwater-?ow within the watershed. In the southern part of the watershed, where bedrock is shallow, groundwater ?ow paths are relatively short, extending from local recharge areas to adjacent ?rst and second-order streams. In contrast, laterally continuous deposits of clay-rich till covering the Superior Lowlands isolate most smaller streams from the sandstone aquifer, allowing for longer ?ow paths toward larger streams such as the Bad, Marengo, and White Rivers. Approximately three-quarters of all ?rst-order stream cells were dry in the Superior Lowlands, compared to only half of ?rst-order stream cells in the southern bedrock uplands. The model was used to delineate the groundwatershed for the Bad and Kakagon Rivers. Groundwatershed is defned as the area contributing groundwater discharge to one of these streams and their tributaries. The groundwatershed was found to align closely with the surface-watershed, with the most notable exception occurring along the southwestern half of Birch Hill, where surface water drains southwest towards the Potato River, and groundwater ?ows north and east towards Lake Superior. Similarly, the contributing area of groundwater-?ow to the Reservation was delineated. Results indicate the off-Reservation groundwater contributing area to be limited in comparison to the extent of the watershed, extending southward into the highlands underlain by MRS igneous rock units, but not further into the area underlain by the Marquette Range Supergroup. Stable isotope samples were collected from 54 wells within the watershed, to investigate sources of groundwater. Oxygen-18 (? 18O) values lower than -13.0 per mil were documented in the sampling, and likely indicate the presence of recharge water from the last glacial period (>9,500 years old) beneath the northern portion of the Reservation, in the vicinity of Odanah, Wisconsin. Finally, a new data-worth analysis of potential new monitoring-well locations was performed by using the model. The relative worth of new measurements was evaluated based on their ability to increase con?dence in model predictions of groundwater levels and base ?ows at 35 locations, under the condition of a proposed open-pit iron mine. Results of the new data-worth analysis, and other inputs and outputs from the Bad River model, are available through an online dynamic web mapping service at (http://wim.usgs.gov/badriver/).

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GroMoPo Metadata for Trout Lake MODFLOW model
Created: Feb. 7, 2023, 6:11 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Transient recharge to the water table is often not well understood or quantified. Two approaches for simulating transient recharge in a ground water flow model were investigated using the Trout Lake watershed in north-central Wisconsin: ( 1) a traditional approach of adding recharge directly to the water table and ( 2) routing the same volume of water through an unsaturated zone column to the water table. Areas with thin ( less than 1 m) unsaturated zones showed little difference in timing of recharge between the two approaches; when water was routed through the unsaturated zone, however, less recharge was delivered to the water table and more discharge occurred to the surface because recharge direction and magnitude changed when the water table rose to the land surface. Areas with a thick ( 15 to 26 m) unsaturated zone were characterized by multimonth lags between infiltration and recharge, and, in some cases, wetting fronts from precipitation events during the fall overtook and mixed with infiltration from the previous spring snowmelt. Thus, in thicker unsaturated zones, the volume of water infiltrated was properly simulated using the traditional approach, but the timing was different from simulations that included unsaturated zone flow. Routing of rejected recharge and ground water discharge at land surface to surface water features also provided a better simulation of the observed flow regime in a stream at the basin outlet. These results demonstrate that consideration of flow through the unsaturated zone may be important when simulating transient ground water flow in humid climates with shallow water tables.

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GroMoPo Metadata for Kish Island SUTRA model
Created: Feb. 7, 2023, 6:12 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Understanding the fresh groundwater lens (FGL) behavior and potential threat of climatic-induced seawater intrusion (SWI) are significant for the future water resources management of many small islands. In this paper, the FGL of Kish Island, an arid-region case in the Persian Gulf, Iran, is modeled using two-dimensional (2D) and three-dimensional (3D) simulations. These simulations are based on the application of SUTRA, a density-dependent groundwater numerical model. Also, the numerical model parameters are calibrated using PEST, an automated parameter estimation code. Firstly a detailed conceptualization of the FGL model is completed to understand the sensitivity of the FGL to some particular aspects of the model prior to analysis of climate change simulations. For these investigations, the FGL system is defined based on Kish Island system to accomplish the integrated comparison of features of a conceptual model that are representative of real-world systems. This is the first study which adopts such an approach. The comparison of cross-sectional simulations suggests that the two-layer properties of the Kish Island aquifer have a significant influence on the FGL while the impacts of lateral-boundary irregularities are negligible. The impacts of sea-level rise (SLR), associated land-surface inundation (LSI), and variations in recharge rate on the FGL salinization of Kish Island are investigated numerically. Variations of SLR value (1-4 m) and net recharge rate (17-24 mm/year) are considered to cover a possible range of climatic scenarios in this arid-region island. The 2D and 3D simulation results demonstrate that LSI caused by SLR and recharge rate variation impacts are more important factors in the FGL in comparison to estimated SLR impacts without LSI. It is also shown that climate change impacts on the FGL are long-term to reach a new FGL equilibrium in the case of Kish Island's aquifer system. The comparative analysis of 2D and 3D results shows that three-dimensionality is a significant factor, especially in large-scale 3D systems of small islands. The results of this study are expected to have implications for the understanding and management of the fresh groundwater resources of Kish Island and are also expected to be relevant to the study of the impact of climate change on groundwater resources on islands worldwide. (C) 2014 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Shenzen FEFLOW model
Created: Feb. 7, 2023, 6:13 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

During the 1990s, groundwater overexploitation has resulted in seawater intrusion in the coastal aquifer of the Shenzhen city, China. Although water supply facilities have been improved and alleviated seawater intrusion in recent years, groundwater overexploitation is still of great concern in some local areas. In this work we present a three-dimensional density-dependent numerical model developed with the FEFLOW code, which is aimed at simulating the extent of seawater intrusion while including tidal effects and different groundwater pumping scenarios. Model calibration, using waterheads and reported chloride concentration, has been performed based on the data from 14 boreholes, which were monitored from May 2008 to December 2009. A fairly good fitness between the observed and computed values was obtained by a manual trial-and-error method. Model prediction has been carried out forward 3 years with the calibrated model taking into account high, medium and low tide levels and different groundwater exploitation schemes. The model results show that tide-induced seawater intrusion significantly affects the groundwater levels and concentrations near the estuarine of the Dasha river, which implies that an important hydraulic connection exists between this river and groundwater, even considering that some anti-seepage measures were taken in the river bed. Two pumping scenarios were considered in the calibrated model in order to predict the future changes in the water levels and chloride concentration. The numerical results reveal a decreased tendency of seawater intrusion if groundwater exploitation does not reach an upper bound of about 1.32 x 10(4) m(3)/d. The model results provide also insights for controlling seawater intrusion in such coastal aquifer systems.

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GroMoPo Metadata for Wadi Ham FEFLOW model
Created: Feb. 7, 2023, 6:15 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

The control and management of seawater intrusion in coastal aquifers is a major challenge in the field of water resources management. Seawater intrusion is a major problem in the coastal aquifer of Wadi Ham, United Arab Emirates, caused by intensive groundwater abstraction from increased agricultural activities. This has caused the abandonment of salinized wells and ultimately affected farming activities and domestic water supply in the area. In this study, the 3D finite element groundwater flow and solute transport model is developed using FEFLOW to simulate pumping of brackish water from the intrusion zone to control seawater intrusion in the aquifer. The model was calibrated and validated with available records of groundwater levels and salinity distribution. Different simulation scenarios were conducted to obtain optimum pumping locations, rates as well as a number of wells. A comparison between scenarios of non-pumping and pumping of brackish water was conducted. Results showed an increase in the concentration of groundwater salinity under the non-pumping scenario, while it decreased under the pumping scenario. Under the non-pumping scenario, isoline 30,000 mgl(-1) was observed to have intruded into the south-eastern part of the aquifer, while the maximum isoline observed for the same area under the pumping scenario was 20,000 mgl(-1). This result showed an overall improvement in the quality of groundwater and ultimately halted seawater intrusion in the aquifer.

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GroMoPo Metadata for Korba Aquifer Kerrou model
Created: Feb. 7, 2023, 6:16 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

A stochastic study of long-term forecasts of seawater intrusion with an application to the Korba aquifer (Tunisia) is presented. Firstly, a geostatistical model of the exploitation rates was constructed, based on a multi-linear regression model combining incomplete direct data and exhaustive secondary information. Then, a new method was designed and used to construct a geostatistical model of the hydraulic conductivity field by combining lithological information and data from hydraulic tests. Secondly, the effects of the uncertainties associated with the pumping rates and the hydraulic conductivity field on the 3D density-dependent transient model were analysed separately and then jointly. The forecasts of the impacts of two different management scenarios on seawater intrusion in the year 2048 were performed by means of Monte Carlo simulations, accounting for uncertainties in the input parameters as well as possible changes of the boundary conditions. Combining primary and secondary data allowed maps of pumping rates and the hydraulic conductivity field to be constructed, despite a lack of direct data. The results of the stochastic long-term forecasts showed that, most probably, the Korba aquifer will be subject to important losses in terms of regional groundwater resources.

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GroMoPo Metadata for Moghra Aquifer SEAWAT model
Created: Feb. 7, 2023, 6:18 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

The Moghra aquifer has shown promise in land reclamation projects conducted in the Western Desert of Egypt. Although this aquifer has hundreds of pumping wells in new urban communities built to meet the needs of the increased population, the system is threatened by the phenomenon of seawater intrusion (SWI). The present study evaluates the degree to which these pumping wells will attract seawater to the aquifer system in the Western Desert region under different pumping conditions. Using the SEAWAT module of Groundwater Modeling System (GMS) software, a three-dimensional (3D) finite-difference model is built to simulate the flow and salinity distribution in the Moghra aquifer considering the geological and hydrogeological characteristics of the aquifer system. The procedure used to solve the mathematical model relied on merging two different approaches. The first approach described the dividing lines of the transition zone due to the SWI. The second approach was applied to conduct the perfect calibration process for the aquifer system. The results show that the flow and quality of the groundwater aquifer are affected by pumping. The water level and salinity are predicted under different pumping rates, a fivefold increase in the pumping rate results that the salinity increased between 4% and 26.8% according to the well location. Moreover, the drawdown values reached 162 m, which is about 46.3% of the saturated thickness.

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GroMoPo Metadata for Pan-European MODFLOW-LISFLOOD model
Created: Feb. 7, 2023, 6:19 p.m.
Authors: None · Frances Dunn

ABSTRACT:

During the last years, we have developed a model, which is able to simulate hydrological processes at a Pan-European scale. The model has multiple possible uses, including flood forecasting, identification of groundwater recharge / discharge zones and large-scale water resources management. The integrated model is based on the LISFLOOD model, which simulates hydrological processes with a focus on snow and soil hydrology and streamflow routing. The area of interest is the full European continent, divided in 5 x 5 km cells. A conceptual 2D MODFLOW model was linked to improve groundwater simulation. With this coupling, it is now possible to simulate the water exchanges between adjacent cells, and between groundwater and river. Available meteorological data from 1-1-1990 to 31-10-2014 were used as input for the coupled model, together with values of aquifer properties derived from literature. We used observed data of recharge, discharge and hydraulic heads from the Danube river basin to check if the model results correspond to reality. The results show a reasonably high degree of agreement between observed and simulated data, taking into account the limitations of large scale modelling. This model is the first step to improve integrated groundwater and surface water modelling which includes the collection of data and the production of Pan-European groundwater parameter maps.

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GroMoPo Metadata for EURO-CORDEX Terrestrial Systems Modeling Platform
Created: Feb. 7, 2023, 6:21 p.m.
Authors: None · Frances Dunn

ABSTRACT:

Applying the Terrestrial Systems Modeling Platform, TSMP, this study provides the first simulated long-term (1996-2018), high-resolution (~12.5?km) terrestrial system climatology over Europe, which comprises variables from groundwater across the land surface to the top of the atmosphere (G2A). The data set offers an unprecedented opportunity to test hypotheses related to short- and long-range feedback processes in space and time between the different interacting compartments of the terrestrial system. The physical consistency of simulated states and fluxes in the terrestrial system constitutes the uniqueness of the data set: while most regional climate models (RCMs) have a tendency to simplify the soil moisture and groundwater representation, TSMP explicitly simulates a full 3D soil- and groundwater dynamics, closing the terrestrial water cycle from G2A. As anthopogenic impacts are excluded, the dataset may serve as a near-natural reference for global change simulations including human water use and climate change. The data set is available as netCDF files for the pan-European EURO-CORDEX domain.

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GroMoPo Metadata for Wadi Watir delta model
Created: Feb. 7, 2023, 6:22 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

The Wadi Watir delta, in the arid Sinai Peninsula, Egypt, contains an alluvial aquifer underlain by impermeable Precambrian basement rock. The scarcity of rainfall during the last decade, combined with high pumping rates, resulted in degradation of water quality in the main supply wells along the mountain front, which has resulted in reduced groundwater pumping. Additionally, seawater intrusion along the coast has increased salinity in some wells. A three-dimensional (3D) groundwater flow model (MODFLOW) was calibrated using groundwater-level changes and pumping rates from 1982 to 2009; the groundwater recharge rate was estimated to be 1.58 x 10(6) m(3)/year. A variable-density flow model (SEAWAT) was used to evaluate seawater intrusion for different pumping rates and well-field locations. Water chemistry and stable isotope data were used to calculate seawater mixing with groundwater along the coast. Geochemical modeling (NETPATH) determined the sources and mixing of different groundwaters from the mountainous recharge areas and within the delta aquifers; results showed that the groundwater salinity is controlled by dissolution of minerals and salts in the aquifers along flow paths and mixing of chemically different waters, including upwelling of saline groundwater and seawater intrusion. Future groundwater pumping must be closely monitored to limit these effects.

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GroMoPo Metadata for Coastal fresh-saltwater interface model
Created: Feb. 7, 2023, 6:23 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Over the past few decades, seawater desalination has become a necessity for freshwater supply in many countries worldwide, particularly in arid and semi-arid regions. One potentially high-quality feed water for desalination is saline groundwater (SGW) from coastal aquifers, which has lower fouling propensity than seawater. This study examines the effect of pumping SGW from a phreatic coastal aquifer on fresh groundwater, particularly on the dynamics of the fresh-saline water interface (FSI). Initially, we constructed a 3D finite-element model of a phreatic coastal aquifer by using the FEFLOW software, which solves the coupled variable density groundwater flow and solute transport equations. Then, we compared and validated the results of the model to those of a field-scale pumping test. The model indicates that pumping SGW from a coastal aquifer freshens the aquifer and rehabilitates parts that were salinized due to seawater intrusion - an effect that increases with increasing pumping rate. In addition, when simultaneously pumping fresh groundwater further inland and SGW from below the FSI, the freshening effect is less pronounced and the salinity of the aquifer is more stable. In line with the results of the model, the field experiment revealed that salinity in the observation well decreases over the course of pumping. Taken together, our findings demonstrate that, in addition to providing a high-quality source feed water for desalination, pumping SGW does not salinize the aquifer and even rehabilitates it by negating the effect of seawater intrusion. These findings are important for planning shoreline desalination facilities and for managing arid coastal regions with lack of water supply and over exploited aquifers. (C) 2019 Published by Elsevier Ltd.

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GroMoPo Metadata for Almeria saline groundwater model
Created: Feb. 7, 2023, 6:25 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

This study tests for the first time the long-term effects of pumping saline groundwater (SGW) as feed for a desalination plant on a coastal aquifer. Field measurements combined with 3D modeling of the hydrological conditions were conducted to examine the effects of SGW pumping on the aquifer system. The plant is next to the city of Almeria (South East Spain) and has been operating since 2006. It uses multiple beach wells along the shore to draw SGW from beneath the fresh-saline water interface (FSI) of the Andarax coastal aquifer. The long-term impact of the intensive pumping on the aquifer was assessed by electrical conductivity profiles in three observation wells dining 12 years of pumping. The FSI deepened with continuous pumping, reaching a decrease of similar to 50 m in the observation well closest to the pumping wells. A calibrated three-dimensional numerical model of the Anthrax aquifer replicates the freshening of the aquifer due to the continuous pumping, resulting in a salinity decrease of similar to 16% in the vicinity of the wells. The salinity decrease stabilizes at 17%, and the model predicts no further significant decrease in salinity for additional 20 years. Submarine groundwater discharge is lowered due to the SGW pumping and similar to 19,000,000 m(3) of freshwater has not lost to the sea during the 12 years of pumping with a rate of similar to 1,100,000 m(3) yr(-1) after 6 years of pumping. After pumping cessation, hydrostatic equilibrium would take about 20 years to recover. This work presents the complex dynamics of the HI due to the SGW pumping for desalination in the first real long-term scenario. It shows by combining field work and numerical modeling, a significant freshening of the aquifer by pumping SGW, emphasizing an additional advantage and the effectiveness of this use as a negative hydraulic barrier against seawater intrusion. (C) 2020 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Bremerhaven coastal aquifer model
Created: Feb. 7, 2023, 6:26 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Climate change is expected to induce sea level rise in the German Bight, which is part of the North Sea, Germany. Climate change may also modify river discharge of the river Weser flowing into the German Bight, which will alter both pressure and salinity distributions in the river Weser estuary. To study the long-term interaction between sea level rise, discharge variations, a storm surge and coastal aquifer flow dynamics, a 3D seawater intrusion model was designed using the fully coupled surface-subsurface numerical model HydroGeoSphere. The model simulates the coastal aquifer as an integral system considering complexities such as variable-density flow, variably saturated flow, irregular boundary conditions, irregular land surface and anthropogenic structures (e.g., dyke, drainage canals, water gates). The simulated steady-state groundwater flow of the year 2009 is calibrated using PEST. In addition, four climate change scenarios are simulated based on the calibrated model: (i) sea level rise of 1 m, (ii) the salinity of the seaside boundary increases by 4 PSU (Practical Salinity Units), (iii) the salinity of the seaside boundary decreases by 12 PSU, and (iv) a storm surge with partial dyke failure. Under scenarios (i) and (iv), the salinized area expands several kilometers further inland during several years. Natural remediation can take up to 20 years. However, sudden short-term salinity changes in the river Weser estuary do not influence the salinized area in the coastal aquifer. The obtained results are useful for coastal engineering practices and drinking water resource management. (C) 2015 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Global gradient-based groundwater model
Created: Feb. 7, 2023, 6:31 p.m.
Authors: None · Reinecke, Robert

ABSTRACT:

In global hydrological models, groundwater (GW) is typically represented by a bucket-like linear groundwater reservoir. Reservoir models, however, (1) can only simulate GW discharge to surface water (SW) bodies but not recharge from SW to GW, (2) provide no information on the location of the GW table, and (3) assume that there is no GW flow among grid cells. This may lead, for example, to an underestimation of groundwater resources in semiarid areas where GW is often replenished by SW or to an underestimation of evapotranspiration where the GW table is close to the land surface. To overcome these limitations, it is necessary to replace the reservoir model in global hydrological models with a hydraulic head gradient-based GW flow model. We present G(3)M, a new global gradient-based GW model with a spatial resolution of 5 0 (arcminutes), which is to be integrated into the 0.5 degrees WaterGAP Global Hydrology Model (WGHM). The newly developed model framework enables in-memory coupling to WGHM while keeping overall run-time relatively low, which allows sensitivity analyses, calibration, and data assimilation. This paper presents the G3M concept and model design decisions that are specific to the large grid size required for a global-scale model. Model results under steady-state naturalized conditions, i.e., neglecting GW abstractions, are shown. Simulated hydraulic heads show better agreement to observations around the world compared to the model output of de Graaf et al. (2015). Locations of simulated SW recharge to GW are found, as is expected, in dry and mountainous regions but areal extent of SW recharge may be underestimated. Globally, GW dis-charge to rivers is by far the dominant flow component such that lateral GW flows only become a large fraction of total diffuse and focused recharge in the case of losing rivers, some mountainous areas, and some areas with very low GW recharge. A strong sensitivity of simulated hydraulic heads to the spatial resolution of the model and the related choice of the water table elevation of surface water bodies was found. We suggest to investigate how global-scale ground-water modeling at 5' spatial resolution can benefit from more highly resolved land surface elevation data.

NOTE: Model has global extent, bounding box is positioned over the Atlantic Ocean for visibility.

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GroMoPo Metadata for Mekong Delta SEAWAT model
Created: Feb. 7, 2023, 6:32 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Groundwater salinization is one of the most severe environmental problems in coastal aquifers worldwide, causing exceeding salinity in groundwater supply systems for many purposes. High salinity concentration in groundwater can be detected several kilometers inland and may result in an increased risk for coastal water supply systems and human health problems. This study investigates the impacts of groundwater pumping practices and regional groundwater flow dynamics on groundwater flow and salinity intrusion in the coastal aquifers of the Vietnamese Mekong Delta using the SEAWAT model-a variable-density groundwater flow and solute transport model. The model was constructed in three dimensions (3D) and accounted for multi-aquifers, variation of groundwater levels in neighboring areas, pumping, and paleo-salinity. Model calibration was carried for 13 years (2000 to 2012), and validation was conducted for 4 years (2013 to 2016). The best-calibrated model was used to develop prediction models for the next 14 years (2017 to 2030). Six future scenarios were introduced based on pumping rates and regional groundwater levels. Modeling results revealed that groundwater pumping activities and variation of regional groundwater flow systems strongly influence groundwater level depletion and saline movement from upper layers to lower layers. High salinity (>2.0 g/L) was expected to expand downward up to 150 m in depth and 2000 m toward surrounding areas in the next 14 years under increasing groundwater pumping capacity. A slight recovery in water level was also observed with decreasing groundwater exploitation. The reduction in the pumping rate from both local and regional scales will be necessary to recover groundwater levels and protect fresh aquifers from expanding paleo-saline in groundwater.

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GroMoPo Metadata for Puri coastal aquifer model
Created: Feb. 7, 2023, 6:34 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Puri city is situated on the east coast of India, and groundwater is the only source available to meet city water supply. Due to increase in population and urbanization of the city, groundwater withdrawal is continuously increasing, which may lead to the movement of saline water interface toward the fresh groundwater. Therefore, the objective of this study was to assess the hydrodynamics of groundwater flow and to predict withdrawal for future water demand of the city without affecting the saltwater intrusion. For this, a groundwater flow model was conceptualized and validated for the present withdrawal coupled with the saltwater intrusion model. To assess the safe yield of groundwater withdrawal, various iterations were carried out with different withdrawal rates and movement of fresh and saltwater interface. This helped in quantifying the future demand of city water supply without affecting the interface between fresh groundwater and saltwater. Based on the simulation results, various measures were suggested to safeguard the groundwater resource against saltwater intrusion.

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GroMoPo Metadata for Biscayne Aquifer USGS model
Created: Feb. 7, 2023, 6:35 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

To address concerns about the effects of water-resource management practices and rising sea level on saltwater intrusion, the U.S. Geological Survey in cooperation with the Broward County Environmental Planning and Community Resilience Division, initiated a study to examine causes of saltwater intrusion and predict the effects of future alterations to the hydrologic system on salinity distribution in eastern Broward County, Florida. A three-dimensional, variable-density solute-transport model was calibrated to conditions from 1970 to 2012, the period for which data are most complete and reliable, and was used to simulate historical conditions from 1950 to 2012. These types of models are typically difficult to calibrate by matching to observed groundwater salinities because of spatial variability in aquifer properties that are unknown, and natural and anthropogenic processes that are complex and unknown; therefore, the primary goal was to reproduce major trends and locally generalized distributions of salinity in the Biscayne aquifer. The methods used in this study are relatively new, and results will provide transferable techniques for protecting groundwater resources and maximizing groundwater availability in coastal areas. The model was used to (1) evaluate the sensitivity of the salinity distribution in groundwater to sea-level rise and groundwater pumping, and (2) simulate the potential effects of increases in pumping, variable rates of sea-level rise, movement of a salinity control structure, and use of drainage recharge wells on the future distribution of salinity in the aquifer. Results from the simulation of historical conditions indicate that the model generally represents the observed greater westward extent of elevated salinity in the central part of the intruded area relative to the northern and southernmost parts of the intruded area. Results of sensitivity testing indicate that the extent of elevated salinity is most sensitive to pumping in areas where the source of saltwater is largely offshore, from the Atlantic Ocean, and is most sensitive to sea-level rise in areas where the source of salinity is downward leakage of brackish water from canals. Simulations of future scenarios indicate that increases in pumping near the existing interface may cause the interface to advance and decreases in pumping may cause it to retreat. Climatic effects, such as periods of prolonged drought or high precipitation, may augment or counteract long-term effects of changes in pumping on aquifer salinity at well fields. With increasing rates of sea-level rise, the freshwater-saltwater interface advances progressively inland, and flow-averaged salinities at well fields near the existing interface increase commensurately. Hypothetical southeastward (downstream) re-positioning of the existing G-54 salinity-control structure may prevent the interface from moving northwestward along and near the North New River canal, but beneficial effects are localized. Implementation of freshwater recharge wells in the city of Hallandale Beach may also have only a localized freshening effect in the aquifer and little appreciable effect on the freshwater-saltwater interface or on concentrations of salinity at well fields. Model accuracy and use are limited by uncertainty in the physical properties and boundary conditions of the system, uncertainty in historical and future conditions, and generalizations made in the mathematical relationships used to describe the physical processes of groundwater flow and transport. Because of these limitations, model results should be considered in relative rather than absolute terms. Nonetheless, model results do provide useful information on the relative scale of response of the system to changes in pumping distribution, sea-level rise, and mitigation activities.

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GroMoPo Metadata for Edwards Aquifer USGS model
Created: Feb. 7, 2023, 6:53 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

In 2010, the U.S. Geological Survey, in cooperation with the San Antonio Water System, began a study to assess the brackish-water movement within the Edwards aquifer (more specifically the potential for brackish-water encroachment into wells near the interface between the freshwater and brackish-water transition zones, referred to in this report as the transition-zone interface) and effects on spring discharge at Comal and San Marcos Springs under drought conditions using a numerical model. The quantitative targets of this study are to predict the effects of higher-than-average groundwater withdrawals from wells and drought-of-record rainfall conditions of 1950-56 on (1) dissolved-solids concentration changes at production wells near the transition-zone interface, (2) total spring discharge at Comal and San Marcos Springs, and (3) the groundwater head (head) at Bexar County index well J-17. The predictions of interest, and the parameters implemented into the model, were evaluated to quantify their uncertainty so the results of the predictions could be presented in terms of a 95-percent credible interval. The model area covers the San Antonio and Barton Springs segments of the Edwards aquifer; the history-matching effort was focused on the San Antonio segment. A previously developed diffuse-flow model of the Edwards aquifer, which forms the basis for the model in this assessment, is primarily based on a conceptualization in which flow in the aquifer is predominately through a network of numerous small fractures and openings. Primary updates to this model include an extension of the active area downdip, a conversion to an 8-layer SEAWAT variable-density flow and transport model to simulate dissolved-solids concentration effects on water density, history matching to 1999-2009 conditions, and parameter estimation in a highly parameterized context using automated methods in PEST (a model-independent Parameter ESTimation code). In addition to the best-fit parameter values derived from history matching, the uncertainty of model parameters was also estimated by using linear uncertainty analysis. Comparison of prior (before history matching) and posterior (after history matching) variances of parameters indicate that the information within the observation dataset used for history matching informs many parameters. The concentration threshold parameters were well-informed by the observation dataset as their posterior distributions were much narrower than their prior distributions. The transition-zone scaling parameters of hydraulic conductivity, effective porosity, and specific storage were all informed by the observation dataset, as evidenced by the difference between the prior and posterior variances. Saline-zone scaling parameters, alternatively, were not informed by the observation dataset for effective porosity and specific storage. Resulting posterior drier-month, wetter-month, and annual recharge multiplier parameter variances are important to understanding how well recharge is estimated and implemented within the model. The shifts of the posterior distributions left and right indicate that there were zones where less or more water was needed in the model. The widths of the distributions were not decreased substantially, indicating that many of the best-fit recharge parameters are not statistically different from the initial values specified in the history-matching effort. Recharge from rainfall is the driving force behind groundwater flow and heads in the aquifer; therefore, an increase in understanding of this process would benefit model development by potentially decreasing the uncertainty of this parameter. The history-matching effort was most helpful in informing the parameters in the model that control discharge at springs, namely, the spring orifice (drain) altitude and drain conductance parameters for each spring. The uncertainty assessment of the predictive model (a hypothetical recurrence of 1950-56 drought conditions and higher-than-average groundwater withdrawals from wells) provided insights into the potential effects of these conditions on dissolved-solids concentration changes at production wells near the transition-zone interface, discharges at Comal and San Marcos Springs, and heads at Bexar County index well J-17. Results at the 25 production wells near the transition-zone interface indicate that the uncertainty of model input parameters based on expert knowledge yielded an upper bound of the 95-percent credible interval of dissolved-solids concentrations that exceeds the secondary drinking water standards of 1,000 milligrams per liter (mg/L) of the Texas Commission on Environmental Quality (TCEQ) for many wells. However, the history-matching process provided key information to inform prediction-sensitive model parameters and therefore, contributed to a substantial decrease of the upper bound of the 95-percent credible interval to below the secondary drinking water standards. Reductions in dissolved-solids concentration changes were on the order of 400 mg/L to 1,300 mg/L. The reduction in uncertainty in regards to this prediction implies that this prediction of dissolved-solids concentration change can be made with some certainty using this current model and that those parameters that control this prediction are informed by the observation dataset. Even though predictive uncertainty was reduced for this prediction, dissolved-solids concentration changes were still greater than zero, indicating a minimal increase in concentration at these 25 production wells during the 7-year simulation period is likely. However, this minimal concentration increase indicates a small potential for movement of the brackish-water transition zone near these wells during the 7-year simulation period of drought-ofrecord (1950-56) rainfall conditions with higher-than-average groundwater withdrawals by wells. Predictive results of total spring discharge during the 7-year period, as well as head predictions at Bexar County index well J-17, were much different than the dissolved-solids concentration change results at the production wells. These upper bounds are an order of magnitude larger than the actual prediction which implies that (1) the predictions of total spring discharge at Comal and San Marcos Springs and head at Bexar County index well J-17 made with this model are not reliable, and (2) parameters that control these predictions are not informed well by the observation dataset during historymatching, even though the history-matching process yielded parameters to reproduce spring discharges and heads at these locations during the history-matching period. Furthermore, because spring discharges at these two springs and heads at Bexar County index well J-17 represent more of a cumulative effect of upstream conditions over a larger distance (and longer time), many more parameters (with their own uncertainties) are potentially controlling these predictions than the prediction of dissolved-solids concentration change at the prediction wells, and therefore contributing to a large posterior uncertainty.

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GroMoPo Metadata for Santa Barbara and Foothill Basins USGS model
Created: Feb. 7, 2023, 6:55 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Groundwater has been a part of the city of Santa Barbara's water-supply portfolio since the 1800s; however, since the 1960s, the majority of the city's water has come from local surface water, and the remainder has come from groundwater, State Water Project, recycled water, increased water conservation, and as needed, seawater desalination. Although groundwater from the Santa Barbara and Foothill groundwater basins only accounts for a small percentage of the long-term supply, it is an important source of supplemental water during times of surface-water shortages. During the late 1980s and early 1990s, production wells extracted additional groundwater to compensate for drought related water-delivery shortfalls from other sources; in response, water levels declined substantially in the Santa Barbara and Foothill groundwater basins (below sea level in the Santa Barbara groundwater basin). In coastal basins that have groundwater extraction near shore, seawater intrusion is often a problem. Seawater intrusion in the Santa Barbara groundwater basin is thought to be more limited than in other coastal basins because of an offshore fault that acts as a partial barrier to groundwater flow. During the late 1980s and early 1990s, seawater intrusion was observed in the Santa Barbara groundwater basin, as indicated by increased chloride concentrations at several monitoring wells that ranged from 200 ft to 1,300 ft from the ocean and as close as 2,900 ft to the nearest pumping well. This demonstrated that seawater can intrude into the Santa Barbara groundwater basin when groundwater levels fall below sea level near the coast. The city of Santa Barbara is interested in developing a better understanding of the sustainability of its groundwater supplies. In 2014, California adopted historic legislation to manage its groundwater: the Sustainable Groundwater Management Act (SGMA). The SGMA requires the development and implementation of Groundwater Sustainability Plans in 127 priority groundwater basins; although Santa Barbara was not a designated priority basin, the city is taking steps to achieve sustainability. Sustainability was defined in the SGMA in terms of avoiding undesirable results: significant and unreasonable groundwater-level declines, reduction in groundwater storage, seawater intrusion, water-quality degradation, land subsidence, and surface-water depletion. In this project, a cooperative study between the U.S. Geological Survey (USGS) and the city of Santa Barbara, sustainable yield is defined as the volume of groundwater that can be pumped from storage without causing water-level drawdowns and the associated increases in seawater intrusion (as indicated by increases in measured chloride concentrations) at selected wells. In order to estimate the sustainability of Santa Barbara's groundwater basins, a three-dimensional density-dependent groundwater-flow and solute-transport model (the Santa Barbara Flow and Transport Model, or SBFTM) was developed on the basis of an existing groundwater-flow model. To simulate seawater intrusion to the Santa Barbara Basin under various management strategies, the SBFTM uses the USGS code SEAWAT to simulate salinity transport and variable-density flow. The completed SBFTM was coupled with a management optimization tool, in this case a multi-objective evolutionary algorithm, to determine optimal pumping strategies that maximize the sustainable yield and at the same time satisfy user-defined drawdown and chloride-concentration constraints. As part of this study, a three-dimensional hydrogeologic framework model was developed to quantify the extent and hydrogeologic characteristics of the Santa Barbara and Foothill groundwater basins and to help define the discretization and hydraulic properties used in the SBFTM. The development of the hydrogeologic framework model required the collection and reconciliation of geologic and geophysical data from existing maps, reports, and databases, along with geologic and hydrologic data from recently drilled wells. These data were integrated into a three-dimensional hydrogeologic framework model that defines the stratigraphy and geometry of the aquifer zones and the major geologic structures in the basin. The hydrogeologic framework model also quantifies the variation in sediment grain size within each aquifer zone as the percentage of coarse-grained sediment. Previous studies indicated that there are two principal water-producing zones in the Santa Barbara groundwater basin, the upper and lower producing zones; an additional thin, productive zone was identified as part of this study. This middle producing zone is not as areally extensive as the upper and lower producing zones and only exists in the coastal part of Storage Unit I. These producing zones are bounded at depth by less productive shallow, middle, and deep zones. Two versions of the SBFTM were constructed: an initial-condition model and a modern transient model. The initial-condition model is a long-term transient model that simulates flow and solute-transport conditions during a period with limited anthropogenic influences preceeding the modern transient model. The simulation-transient model simulates flow and transport conditions from 1929 through 2013; however, because of data availability, the focus of the model calibration was 1972-2013. The SBFTM was calibrated to measured groundwater levels and drawdown, as well as measured chloride concentrations and change in concentrations, using a combination of automated and trial-and-error parameter-estimation techniques. A sensitivity analysis indicated that, in general, the SBFTM was most sensitive to recharge- and pumping-distribution parameters, specifically those controlling the amount of small-catchment recharge and the distribution of water extraction by hydrogeologic layer for production wells. The model was also sensitive to parameters controlling stream-recharge rates, horizontal and vertical hydraulic conductivity, and porosity. From 1929 to 1971, most of the water entering the area represented by the SBFTM was from creek and small-catchment recharge, and the majority of water leaving the SBFTM area was from pumping, discharge to creeks, and drains. In addition, about 37 percent of the total pumpage came from a net reduction in groundwater storage. From 1972 to 2013, the amount of water entering and leaving the SBFTM was fairly similar as that from 1929 to 1971, except the reduction in pumpage added about 17,000 acre-ft of water to storage. During this later period, there were also times of storage loss. For example, during July 1990, a month when approximately 705 acre-ft of groundwater was pumped in the study area, the pumpage was much greater than all sources of recharge combined, and about 382 acre-ft of water was removed from groundwater storage. Simulated hydraulic heads replicated the observed data to an acceptable matching of the measured water-level, flow direction, and vertical gradients. Simulated hydrographs for selected wells were in good agreement with the measured data, with an average residual of -2.7 ft and a standard deviation of 14.5 ft, indicating that the simulated heads, on average, underestimated the observed water levels. An examination of the model fit indicated that most of the discrepancies were lower simulated heads at wells proximal to production well sites. The simulated chloride concentrations reasonably matched the rising limbs of the measured breakthrough curves in terms of timing and magnitude; however, the simulation overestimated the chloride concentrations on the falling limbs. The overestimation of low chloride concentrations was attributed to the model overestimating the advance of the chloride front during periods of heavy pumping and underestimating the retreat of the chloride front during periods of low pumping. These simulation errors would result in a conservative response by local water managers to seawater intrusion. The SBFTM was used to develop a collection of predictive simulations optimized to produce pumping schedules that maximize yield, subject to a set of constraints and competing objectives. The simulations were grouped as scenarios that differed in their time horizon, initial conditions for groundwater levels and chloride concentrations, as well as precipitation, which was incorporated into the model through simulated recharge. Overall, five scenarios were developed in a multi-objective framework to obtain optimal pumping rates for all of the wells managed by the city, while minimizing excessive drawdown and seawater intrusion. For the current study, complexities in the simulation model and the optimization formulation required additional considerations. Incorporating the solute-transport equations to simulate chloride transport added a highly nonlinear process that is solved iteratively in each time step of the groundwater-flow model. These nonlinearities, coupled with the highly refined grid in the current model, creates challenges for many traditional optimization methods. Therefore, an optimization method was needed that could address nonlinear relationships as well as a very large problem size. Lastly, the optimization problem was reformulated to include multiple objectives without requiring convergence to a single solution. This approach, guided by the city's objectives, allowed the maximum extraction of information from the complex simulation. Borg, a multi-objective evolutionary algorithm, was chosen as the optimization algorithm for this study for several reasons: (1) it is very computationally efficient; (2) it can run in parallel; (3) it requires little user input; and (4) it can solve for multiple competing objectives. The first three points allow the algorithm to proceed toward the optimal solutions at the fastest possible rate. The fourth point is advantageous for large, complex optimization problems because it is difficult to formulate the optimization problem in a way that produces only one optimal solution. The problem formulation consisted of four competing objectives and a constraint set in accordance with the main concerns of the city. The objectives were maximizing total pumpage, minimizing seawater intrusion, minimizing total drawdown in production wells, and minimizing the maximum drawdown. The constraints were pump capacity, meeting drinking-water standards for chloride, maintaining a specified minimum flowrate to a groundwater treatment plant, and maintaining minimum water levels in pumping wells. The decision variables either were quarterly pumpage by well or total pumpage by basin. Five optimization scenarios were developed that allow the decision makers to evaluate a range of optimal solutions for a variety of water levels and chloride concentrations as well as potential future climatic conditions. Three scenarios (1, 2, and 5) were multi-objective optimization formulations that allowed for variations in management preferences and climatic conditions. The other two scenarios (3 and 4) were designed to examine the optimization results to answer specific questions. Scenario 1 described the best-case sustainable yield assuming a full basin (that is, high initial water levels) and typical climate conditions for 10 years. Scenario 2 also started with a full basin; however, this was followed by a 10-year drought. Scenario 3 determined if an empty basin (that is, low initial water levels) would recover to full conditions (1998 conditions) given climate assumptions and optimal pumping schedules from scenarios 1 and 2. Scenario 4 was designed to produce decision rules that can be used by water managers to help choose an optimal pumping schedule based on measured water-level or chloride data. Scenario 5 identified future pumping schedules based on short-term climate variations during a 2-year management horizon. The results from scenarios 1 and 2 described the differences in maximum pumpage in the basin under typical and dry long-term climate projections, respectively. The scenario 1 results indicated the maximum 10-year pumpage of the basin was about 31,300 acre-ft under typical conditions and controlling simulated seawater intrusion and drawdowns. For scenario 2, less recharge over the 10-year dry climate produced a maximum pumpage estimate of 30,000 acre-ft to control seawater intrusion and drawdowns. The larger pumpage for scenario 1 resulted in more seawater intrusion, but less total drawdown, compared to that of scenario 2. Results for scenarios 3 and 4 showed the basin's response to management actions combined with climate projections. Both scenarios used the optimal pumping schedules and the 10-year climates from scenarios 1 and 2. The scenario 3 results showed that under minimal pumping, the basin did not fully recover to 1998 water levels within 10 years under either climate scenario. The relatively larger recharge from the typical climate resulted in less drawdown at coastal monitoring wells after the 10-year recovery period than that from the dry climate. The location of the seawater intrusion front was not appreciably different between the scenarios, however. Scenario 4 used the optimal results from scenarios 1 and 2 to produce decision-rule curves that illustrated the pumpage for each basin, given measured levels of chloride concentration or drawdown. This allowed the use of additional measurements at monitoring wells to assess future management decisions on the basis of the sensitivity of observations of drawdown and seawater intrusion to various pumping rates. Scenario 5 allowed managers to investigate the effects of short-term climate variations on optimal pumping schedules. Three specific 2-year simulations were optimized: typical-to-dry (scenario 5A), dry-to-typical (scenario 5B), and dry-to-dry (scenario 5C). The most noteable result from scenario 5 was the overall reduction in optimal pumpage for most schedules in scenario 5C, when the climate is simulated as dry-to-dry. There are also many optimal pumping schedules that produced an overall increase in waterlevels over the two-year simulation period, regardless of climatic condition. Similar to scenario 2, the scenario 5C results represents conservative yield estimates under a minimal-precipitation climatic condition.

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GroMoPo Metadata for Mississippi Embayment Regional Aquifer Study (MERAS) USGS model
Created: Feb. 7, 2023, 6:56 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Arkansas continues to be one of the largest users of groundwater in the Nation. As such, long-term planning and management are essential to ensure continued availability of groundwater and surface water for years to come. The Mississippi Embayment Regional Aquifer Study (MERAS) model was developed previously as a tool to evaluate groundwater availability within the Mississippi embayment, which encompasses much of eastern Arkansas where the majority of groundwater is used. The Arkansas Water Plan is being updated for the first time since 1990 and serves as the State's primary, comprehensive water-resources planning and guidance document. The MERAS model was selected as the best available tool for evaluation of specific water-use pumping scenarios that are currently being considered by the State of Arkansas. The model, developed as part of the U.S. Geological Survey Groundwater Resources Program's assessment of the Nation's groundwater availability, is proving to be invaluable to the State as it works toward development of a sustained yield pumping strategy. One aspect of this investigation was to evaluate multiple methods to improve the match of observed to simulated groundwater levels within the Mississippi River Valley alluvial and middle Claiborne (Sparta) aquifers in the MERAS model. Five primary methods were evaluated: (1) explicit simulation of evapotranspiration (ET), (2) upgrade of the Multi-Node Well (MNW2) Package, (3) geometry improvement within the Streamflow Routing (SFR) Package, (4) parameter estimation of select aquifer properties with pilot points, and (5) modification of water-use estimates. For the planning purposes of the Arkansas Water Plan, three scenarios were developed to evaluate potential future conditions: (1) simulation of previously optimized pumping values within the Mississippi River Valley alluvial and the middle Claiborne aquifers, (2) simulated prolonged effects of pumping at average recent (2000-5) rates, and (3) simulation of drawdown constraints on most pumping wells. The explicit simulation of ET indicated little, if any, improvement of model fit at the expense of much longer simulation time and was not included in further simulations. Numerous attempts to fully utilize the MNW2 Package were unsuccessful in achieving model stability, though modifications made to the water-use dataset remained intact. Final improvements in the residual statistics may be attributed to a single method, or a cumulative effect of all other methods (geometry improvement with the SFR Package, parameter estimation with pilot points, and modification of water-use estimates) attempted. The root mean squared error (RMSE) for all observations in the model is 22.65 feet (ft) over a range in observed hydraulic head of 741.66 ft. The RMSE for water-level observations in the Mississippi River Valley alluvial aquifer is 14.14 ft (an improvement of almost 3 ft) over a range in observed hydraulic head of 297.25 ft. The RMSE for the Sparta aquifer is 32.02 ft (an improvement of approximately 3 ft) over a range in observed hydraulic head of 634.94 ft. Three scenarios were developed to utilize a steady-state version of the MERAS model. Scenario 1 was developed to use pumping values resulting from the optimization of baseline rates (typically 1997 pumping rates) from previous optimization modeling of the alluvial aquifer and the Sparta aquifer. Scenario 2 was developed to evaluate the prolonged effects of pumping from the alluvial aquifer at recent pumping rates. Scenario 3A was designed to evaluate withdrawal limits from the alluvial aquifer by utilizing drawdown constraints equal to an altitude of approximately 50 percent of the predevelopment saturated thickness of the alluvial aquifer or 30 ft above the bottom of the alluvial aquifer, whichever was greater. The results of scenario 1 indicate large water-level declines throughout the area of the alluvial aquifer, regardless of the substitution of the optimized pumping values from earlier model simulations. The results of scenario 2 also indicate large areas of water-level decline, as compared to half of the saturated thickness, throughout the alluvial aquifer. The results of scenario 3A reveal some effects from the inclusion of multiple aquifers in a single simulation. The initial configuration of scenario 3A resulted in water levels well below the defined drawdown constraint, and some areas of depleted aquifer (water levels that are near or below the bottom of the aquifer) in east-central Arkansas. A fourth simulation (scenario 3B) was configured to apply the same drawdown constraints from the alluvial aquifer wells to the Sparta aquifer wells in the depleted area. These drawdown constraints reduce leakage from the alluvial aquifer to the underlying Sparta aquifer. This configuration did not produce depleted areas within the alluvial aquifer. Scenarios 3A and 3B indicate that even when pumping is limited in the alluvial aquifer, water levels in the alluvial aquifer may continue to decline in some areas because of pumping in the underlying Sparta aquifer.

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GroMoPo Metadata for Northern Gulf Coast aquifer model
Created: Feb. 7, 2023, 6:57 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

In cooperation with the Harris-Galveston Subsidence District, Fort Bend Subsidence District, and Lone Star Groundwater Conservation District, the U.S. Geological Survey developed and calibrated the Houston Area Groundwater Model (HAGM), which simulates groundwater flow and land-surface subsidence in the northern part of the Gulf Coast aquifer system in Texas from predevelopment (before 1891) through 2009. Withdrawal of groundwater since development of the aquifer system has resulted in potentiometric surface (hydraulic head, or head) declines in the Gulf Coast aquifer system and land-surface subsidence (primarily in the Houston area) from depressurization and compaction of clay layers interbedded in the aquifer sediments. The MODFLOW-2000 groundwater flow model described in this report comprises four layers, one for each of the hydrogeologic units of the aquifer system except the Catahoula confining system, the assumed no-flow base of the system. The HAGM is composed of 137 rows and 245 columns of 1-square-mile grid cells with lateral no-flow boundaries at the extent of each hydrogeologic unit to the northwest, at groundwater divides associated with large rivers to the southwest and northeast, and at the downdip limit of freshwater to the southeast. The model was calibrated within the specified criteria by using trial-and-error adjustment of selected model-input data in a series of transient simulations until the model output (potentiometric surfaces, land-surface subsidence, and selected water-budget components) acceptably reproduced field measured (or estimated) aquifer responses including water level and subsidence. The HAGM-simulated subsidence generally compared well to 26 Predictions Relating Effective Stress to Subsidence (PRESS) models in Harris, Galveston, and Fort Bend Counties. Simulated HAGM results indicate that as much as 10 feet (ft) of subsidence has occurred in southeastern Harris County. Measured subsidence and model results indicate that a larger geographic area encompassing this area of maximum subsidence and much of central to southeastern Harris County has subsided at least 6 ft. For the western part of the study area, the HAGM simulated as much as 3 ft of subsidence in Wharton, Jackson, and Matagorda Counties. For the eastern part of the study area, the HAGM simulated as much as 3 ft of subsidence at the boundary of Hardin and Jasper Counties. Additionally, in the southeastern part of the study area in Orange County, the HAGM simulated as much as 3 ft of subsidence. Measured subsidence for these areas in the western and eastern parts of the HAGM has not been documented.

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GroMoPo Metadata for Malioboro MODFLOW model
Created: Feb. 7, 2023, 6:59 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Malioboro is a famous tourism area in Yogyakarta City, in which there are many hotels and increases every years and this follows by the increasing needs of fresh water taken from underlying groundwater. The decreasing of groundwater table become a great issue on this area, therefore the objective of the research is to predict groundwater table change in the next 10 years due to increase abstraction of groundwater. To answer the mentioned objectives, field observation of dug wells and collection of secondary data of log bores also calculation of recharge and water abstraction are used to understand and build the conceptual model of local groundwater system. The prediction is done by conducting simulation on a numerical groundwater model by using MODFLOW. The local groundwater system consists of two aquifer layers; upper aquifer and lower aquifer which separated incompletely by clay layer. Simulation is conducting by distributing the groundwater pumping for domestic and non-domestic utilization by dug wells in the upper aquifer, whereas deep wells non-domestic utilization are applied only in the lower aquifer. Simulations are conducted twice for the recent day and the next ten years prediction of groundwater abstraction. In the case of groundwater abstraction in the next ten years, dug wells abstraction and deep wells pumping are setting to 4727 m3/day and 1648 m3/day, respectively. The groundwater pumping rates is representing increase of groundwater withdrawal of users in the range only between 0.2-1.2 % per year compare to the recent condition. The simulation reveals change occur on groundwater table depth and pattern. In average, the groundwater table will decrease of about 0.25 meter.

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GroMoPo Metadata for Bangkok Basin groundwater age model
Created: Feb. 7, 2023, 7 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A study was undertaken to understand the groundwater flow conditions in the Bangkok Basin, Thailand, by comparing 14 C-based and simulated groundwater ages. 14 C measurements were made on about 50 water samples taken from wells throughout the basin. Simulated ages were obtained using 1) backward-pathline tracking based on the well locations, and 2) results from a three-dimensional groundwater flow model. Comparisons of ages at these locations reveal a large difference between 14 C-based ages and ages predicted by the steady-state groundwater flow model. Mainly, 14 C and 13C analyzes indicate that groundwater in the Bangkok area is about 20,000 years old, whereas steady-state flow and transport simulations imply that groundwater in the Bangkok area is 50,000-100,000 years old. One potential reason for the discrepancy between simulated and 14C-based ages is the assumption in the model of steady-state flow. Groundwater velocities were probably greater in the region before about 10,000 years ago, during the last glacial maximum, because of the lower position of sea level and the absence of the surficial Bangkok Clay. Paleoflow conditions were estimated and then incorporated into a second set of simulations. The new assumption was that current steady-state flow conditions existed for the last 8,000 years but were preceded by steady-state conditions representative of flow during the last glacial maximum. This transient paleohydrologic simulation yielded a mean simulated age that more closely agrees with the mean 14 C-based age, especially if the 14C-based age corrected for diffusion into clay layers. Although the uncertainties in both the simulated and 14 C-based ages are nontrivial, the magnitude of the improved match in the mean age using a paleohydrologic simulation instead of a steady-state simulation suggests that flow conditions in the basin have changed significantly over the last 10,000-20,000 years. Given that the valid age range of 14 C-dating methods and the timing of the last glacial maximum are of similar magnitude, adjustments for paleohydrologic conditions may be required for many such studies.

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GroMoPo Metadata for Southeastern Maine USGS model
Created: Feb. 7, 2023, 7:02 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Watersheds of three streams, the Mousam River, Branch Brook, and Merriland River in southeastern Maine were investigated from 2010 through 2013 under a cooperative project between the U.S. Geological Survey and the Maine Geological Survey. The Branch Brook watershed previously had been deemed at risk by the Maine Geological Survey because of the proportionally large water withdrawals compared to estimates of the in-stream flow requirements for habitat protection. The primary groundwater withdrawals in the study area include a water-supply well in the headwaters of the system and three water-supply wells in the coastal plain near the downstream end of the system. A steady-state groundwater flow model was used to understand the movement of water within the system, to evaluate the water budget and the effect of groundwater withdrawals on streamflows, and to understand streamflow depletion in relation to the State of Maine's requirements to maintain in-stream flows for habitat protection. Delineation of the simulated groundwater divides compared to the surface-water divides suggests that the groundwater divides in the headwater areas do not exactly correspond to the surface-water divides. Under both pumping and non-pumping conditions, groundwater flows from the headwaters of the Branch Brook watershed into the Mousam River watershed. Pumping in the Mousam River watershed captures a small amount of groundwater from the Branch Brook basin. The cumulative effect of groundwater withdrawals on base flows in two rivers in the study area (Branch Brook and the Merriland River) was evaluated using the groundwater flow model. Streamflow depletion in the headwaters of Branch Brook was 0.12 cubic feet per second (ft3/s) for the steady-state simulation, or about 10 percent of the average base flow at that location. Downstream on Branch Brook, the total streamflow depletion from all the wells was 0.59 ft3/s, or 3 percent of the average base flow at that location. In the Merriland River downstream from the Merriland River well, the total amount of streamflow depletion was 0.6 ft3/s, or about 7 percent of the average base flow. The groundwater model was used to evaluate several different scenarios that could affect streamflow and groundwater discharging to the rivers and streams in the study area. The scenarios were (1) no pumping from the water-supply wells; (2) current pumping from the water-supply wells, but simulated drought conditions (25 percent reduction in recharge); (3) current recharge, but with increased pumping from the large water-supply wells; and (4) drought conditions and increased pumping combined. Simulations of increased pumping in the water-supply wells resulted in streamflow depletion in the headwaters of Branch Brook increasing to 16 percent of the headwater base flow. Simulated increases in the pumping in the coastal plain wells increased the amount of streamflow depletion to 6 percent of the flow in Branch Brook and to 8 percent of the flow in the Merriland River. The additional stress of a drought imposed on the model (25 percent less recharge) had a substantial impact on streamflows, as expected. If the simulated drought occurred simultaneously with an increase in pumping, the base flows would be reduced 48 percent in the headwaters of Branch Brook, compared to the no-pumping scenario. Downstream in Branch Brook, the total reduction in flow would be 29 percent of the simulated base flows in the no-pumping scenario, and in the Merriland River, the reduction would be 33 percent of the base flows in the no-pumping scenario. The study evaluated two different methods of calculating in-stream flow requirements for Branch Brook and the Merriland Rivera set of statewide equations used to calculate monthly median flows and the MOVE.1 record-extension technique used on site-specific streamflow measurements. The August median in-stream flow requirement in the Merriland River was calculated as 7.18 ft3/s using the statewide equations but was 3.07 ft3/s using the MOVE.1 analysis. In Branch Brook, the August median in-stream flow requirements were calculated as 20.3 ft3/s using the statewide equations and 11.8 ft3/s using the MOVE.1 analysis. In each case, using site-specific data yields an estimate of in-stream flow that is much lower than an estimate the statewide equations provide.

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GroMoPo Metadata for Pajaro Valley USGS model
Created: Feb. 7, 2023, 7:03 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Increasing population, agricultural development (including shifts to more water-intensive crops), and climate variability are placing increasingly larger demands on available groundwater resources in the Pajaro Valley, one of the most productive agricultural regions in the world. This study provided a refined conceptual model, geohydrologic framework, and integrated hydrologic model of the Pajaro Valley. The goal of this study was to produce a model capable of being accurate at scales relevant to water management decisions that are being considered in the revision and updates to the Basin Management Plan (BMP). The Pajaro Valley Hydrologic Model (PVHM) was designed to reproduce the most important natural and human components of the hydrologic system and related climatic factors, permitting an accurate assessment of groundwater conditions and processes that can inform the new BMP and help to improve planning for long-term sustainability of water resources. Model development included a revision of the conceptual model of the flow system, reevaluation of the previous model transformed into MODFLOW, implementation of the new geohydrologic model and conceptual model, and calibration of the transient hydrologic model. The PVHM model, using MODFLOW with the Farm Process (MF-FMP2), is capable of being accurate at seasonal to interannual time frames and subregional to valley-wide spatial scales for the assessment of the groundwater hydrologic budget for water years 1964-2009, as well as potential assessment of the BMP components and sustainability analysis of conjunctive use. The model provides a good representation of the regional flow system and the use and movement of water throughout the valley. Simulated changes in storage over time show that, prior to the 1984-92 dry period, significant withdrawals from storage occurred only during drought years. Since about 1993, growers in the Pajaro Valley have shifted to more water intensive crops, such as strawberries, bushberries, and vegetable row crops, as well as making additional rotational plantings, which have increased demand on limited groundwater resources. Simulated groundwater flow indicates that vertical hydraulic gradients between horizontal layers fluctuate and even reverse in several parts of the basin as recharge and pumpage rates change seasonally and annually. The majority of recharge predominantly enters the Alluvial aquifer system, and along with pumpage and the largest fractions of storage depletion, occurs in the inland regions. Coastal inflow as seawater intrusion replaces much of the potential storage depletion in the coastal regions. The simulated long-term imbalance between inflows and outflows indicates overdraft of the groundwater basin averaging about 12,950 acre-feet per year (acre-ft/yr) over the 46-year period of water years (1964-2009). Annual overdraft varies considerably from year to year, depending on land use, pumpage, and climate conditions. Climatically driven factors can affect inflows, outflows, and water use by as much as a factor of two between wet and dry years. Coastal inflows and outflows vary by year and by aquifer; the net coastal inflow, or seawater intrusion, ranges from about 1,000 to more than 6,000 acre-ft/yr. Maps of simulated and measured water-level elevations indicate regions with water levels below sea level in the alluvium and Aromas layers. Ongoing expansion of local hydrologic monitoring networks indicates the importance of these networks to the understanding of changes in groundwater flow, streamflow, and streamflow infiltration. In particular, the monitoring of streamflow, groundwater pumpage, and groundwater levels throughout the valley not only indicates the state of the resources, but also provides valuable information for model calibration and for model-based evaluation of management actions. The HS-ASR was simulated for the years 2002-09, and replaced about about 1,290 acre-ft of coastal pumpage. This was combined with the simulation of additional 6,200 acre-ft of deliveries from supplemental wells, recycled water, and city connection deliveries through the CDS that also supplanted some coastal pumpage. Total simulated deliveries were 7,350 acre-ft of the 7,500 acre-ft of reported deliveries for the period 2002-09. The completed CDS should be capable of delivering about 8.8 million cubic meters (7,150 acre-ft) of water per year to coastal farms within the Pajaro Valley, if all the local supply components were fully available for this purpose. This would represent about 15 percent of the 48,300 acre-ft (59.6 million cubic meters) average agricultural pumpage for the period 2005 to 2009. Combined with the potential capture and reuse of some of the return flows and tile-drain flows, this could represent an almost 70 percent reduction of average overdraft for the entire valley and a large part of the coastal pumpage that induces seawater intrusion.

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GroMoPo Metadata for Santa Rosa Plain USGS model
Created: Feb. 7, 2023, 7:05 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Water managers in the Santa Rosa Plain face the challenge of meeting increasing water demand with a combination of Russian River water, which has uncertainties in its future availability; local groundwater resources; and ongoing and expanding recycled water and water from other conservation programs. To address this challenge, the U.S. Geological Survey, in cooperation with the Sonoma County Water Agency, the cities of Cotati, Rohnert Park, Santa Rosa, and Sebastopol, the town of Windsor, the California American Water Company, and the County of Sonoma, undertook development of a fully coupled groundwater and surface-water model to better understand and to help manage the hydrologic resources in the Santa Rosa Plain watershed. The purpose of this report is to (1) describe the construction and calibration of the fully coupled groundwater and surface-water flow model for the Santa Rosa Plain watershed, referred to as the Santa Rosa Plain hydrologic model; (2) present results from simulation of the Santa Rosa Plain hydrologic model, including water budgets, recharge distributions, streamflow, and the effect of pumping on water-budget components; and (3) present the results from using the model to evaluate the potential hydrologic effects of climate change and variability without pumpage for water years 2011-99 and with projected pumpage for water years 2011-40.

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GroMoPo Metadata for Edwards-Trinity USGS model
Created: Feb. 7, 2023, 7:06 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

The Edwards-Trinity aquifer is a vital groundwater resource for agricultural, industrial, and public supply uses in the Pecos County region of western Texas. The U.S. Geological Survey completed a comprehensive, integrated analysis of available hydrogeologic data to develop a numerical groundwater-flow model of the Edwards-Trinity and related aquifers in the study area in parts of Brewster, Jeff Davis, Pecos, and Reeves Counties. The active model area covers about 3,400 square miles of the Pecos County region of Texas west of the Pecos River, and its boundaries were defined to include the saturated areas of the Edwards-Trinity aquifer. The model is a five-layer representation of the Pecos Valley, Edwards-Trinity, Dockum, and Rustler aquifers. The Pecos Valley aquifer is referred to as the alluvial layer, and the Edwards-Trinity aquifer is divided into layers representing the Edwards part of the Edwards-Trinity aquifer and the Trinity part of the Edwards-Trinity aquifer, respectively. The calibration period of the simulation extends from 1940 to 2010. Simulated hydraulic heads generally were in good agreement with observed values; 1,684 out of 2,860 (59 percent) of the simulated values were within 25 feet of the observed value. The average root mean square error value of hydraulic head for the Edwards-Trinity aquifer was 34.2 feet, which was approximately 4 percent of the average total observed change in groundwater-level altitude (groundwater level). Simulated spring flow representing Comanche Springs exhibits a pattern similar to observed spring flow. Independent geochemical modeling corroborates results of simulated groundwater flow that indicates groundwater in the Edwards-Trinity aquifer in the Leon-Belding and Fort Stockton areas is a mixture of recharge from the Barilla and Davis Mountains and groundwater that has upwelled from the Rustler aquifer. The model was used to simulate groundwater-level altitudes resulting from prolonged pumping to evaluate sustainability of current and projected water-use demands. Each of three scenarios utilized a continuation of the calibrated model. Scenario 1 extended recent (2008) irrigation and nonirrigation pumping values for a 30-year period from 2010 to 2040. Projected groundwater-level changes in and around the Fort Stockton area under scenario 1 change little from current conditions, indicating that the groundwater system is near equilibrium with respect to recent (2008) pumping stress. Projected groundwater-level declines in the eastern part of the model area ranging from 5.0 to 15.0 feet are likely the result of nonequilibrium conditions associated with recent increases in pumping after a prolonged water-level recovery period of little or no pumping. Projected groundwater-level declines (from 15.0 to 31.0 feet) occurred in localized areas by the end of scenario 1 in the Leon-Belding area. Scenario 2 evaluated the effects of extended recent (2008) pumping rates as assigned in scenario 1 with year-round maximum permitted pumping rates in the Belding area. Results of scenario 2 are similar in water-level decline and extent as those of scenario 1. The extent of the projected groundwater-level decline in the range from 5.0 to 15.0 feet in the Leon-Belding irrigation area expanded slightly (about a 2-percent increase) from that of scenario 1. Maximum projected groundwater-level declines in the Leon-Belding irrigation area were approximately 31.3 feet in small isolated areas. Scenario 3 evaluated the effects of periodic increases in pumping rates over the 30-year extended period. Results of scenario 3 are similar to those of scenario 2 in terms of the areas of groundwater-level decline; however, the maximum projected groundwater-level decline increased to approximately 34.5 feet in the Leon-Belding area, and the extent of the decline was larger in area (about a 17-percent increase) than that of scenario 2. Additionally, the area of projected groundwater-level declines in the eastern part of the model area increased from that of scenario 2 two individual areas of decline coalesced into one larger area. The localized nature of the projected groundwater-level declines is a reflection of the high degree of fractured control on storage and hydraulic conductivity in the Edwards-Trinity aquifer. Additionally, the finding that simulated spring flow is highly dependent on the transient nature of hydraulic heads in the underlying aquifer indicates the importance of adequately understanding and characterizing the entire groundwater system.

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GroMoPo Metadata for Nauru Island model
Created: Feb. 7, 2023, 7:08 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Water resources sustainable management is a vital issue for small islands where groundwater is often the only available water resource. Nauru is an isolated and uplifted limestone atoll island located in the Pacific Ocean. Politecnico di Milano performed a feasibility study for the development of sustainable use of groundwater on the island. This paper focuses on the first phase of the study that concerns the conceptual site model development, the hydrogeological characterization and the 2D model implementation. During the project, different activities were performed such as GNSS topographic survey of monitoring wells and groundwater level surveys taking into account tidal fluctuation. This data collection and the analysis of previous studies made it possible to identify the most suitable areas for groundwater sustainable extraction. The characterization findings suggested, unlike previous studies and surveys, the presence of only few drought resilient thin freshwater lenses, taking place in low conductivity sandy deposits, unexpectedly next to the seashore. Thanks to the 2D modeling results, it has been possible to clarify the mechanism that allows the storage of freshwater so close to the sea.

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GroMoPo Metadata for Almiros and Lilea spring karst model
Created: Feb. 7, 2023, 7:10 p.m.
Authors: None · Michael Jones

ABSTRACT:

A multicell groundwater model was constructed to investigate the potential improvement in the modelling of karstic aquifers by using a mixed equation suitable for both the free surface and pressure flow conditions in karstic conduits. To estimate the model parameters the shuffled complex evolution (SCE) optimisation method was used. This ensured a fast and objective model calibration. The model was applied to two real-world karstic aquifers and it became clear that in case of absence of water level measurements, the use of the mixed equation did not improved the performance. In cases where both spring discharge and water level measurements were available, the use of the mixed equation proved to be advantageous in reproducing the features of the observed time series especially of the water level. (c) 2005 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Quincy Basin USGS model
Created: Feb. 7, 2023, 7:12 p.m.
Authors: None · Taylor L. Watson

ABSTRACT:

The Miocene Columbia River Basalt Group and younger sedimentary deposits of lacustrine, fluvial, eolian, and cataclysmic-flood origins compose the aquifer system of the Quincy Basin in eastern Washington. Irrigation return flow and canal leakage from the Columbia Basin Project have caused groundwater levels to rise substantially in some areas. Water resource managers are considering extraction of additional stored groundwater to supply increasing demand. To help address these concerns, the transient groundwater model of the Quincy Basin documented in this report was developed to quantify the changes in groundwater flow and storage. The model based on the U.S. Geological Survey modular three-dimensional finite-difference numerical code MODFLOW uses a 1-kilometer finite-difference grid and is constrained by logs from 698 wells in the study area. Five model layers represent two sedimentary hydrogeologic units and underlying basalt formations. Head-dependent flux boundaries represent the Columbia River and other streams, lakes and reservoirs, underflow to and (or) from adjacent areas, and discharge to agricultural drains and springs. Specified flux boundaries represent recharge from precipitation and anthropogenic sources, including irrigation return flow and leakage from water-distribution canals and discharge through groundwater withdrawal wells. Transient conditions were simulated from 1920 to 2013 using annual stress periods. The model was calibrated with the parameter-estimation code PEST to a total of 4,064 water levels measured in 710 wells. Increased recharge since predevelopment resulted in an 11.5 million acre-feet increase in storage in the Quincy Groundwater Management Subarea of the Quincy Basin. Four groundwater-management scenarios were formulated with input from project stakeholders and were simulated using the calibrated model to provide representative examples of how the model could be used to evaluate the effect on groundwater levels as a result of potential changes in recharge, groundwater withdrawals, or increased flow in Crab Creek. Decreased recharge and increased groundwater withdrawals both resulted in declines in groundwater levels over 2013 conditions, whereas increasing the flow in Crab Creek resulted in increased groundwater levels over 2013 conditions.

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GroMoPo Metadata for Southeastern Louisiana Saltwater Intrusion model
Created: Feb. 7, 2023, 7:13 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Projecting the Effects of Saltwater Intrusion on the Fresh Groundwater Resources of Southeastern Louisiana and the New Orleans Area, USA, based on 3D Variable-Density Groundwater Modelling

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GroMoPo Metadata for Florida hurricane saltwater intrusion model
Created: Feb. 7, 2023, 7:15 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Numerical computation of hurricane-induced saltwater intrusion on fresh groundwater availability in peninsular Florida under different climate scenarios

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GroMoPo Metadata for Mojave River Basin USGS model
Created: Feb. 7, 2023, 7:16 p.m.
Authors: None · Chinchu Mohan

ABSTRACT:

Simulation of ground-water flow in the Mojave River Basin, California

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GroMoPo Metadata for Byrds Mill Spring chemograph model
Created: Feb. 7, 2023, 7:18 p.m.
Authors: None · John Richins

ABSTRACT:

Rhythmic springs occur when a groundwater flowpath that supplies a spring's discharge form a hydraulic siphon. The hydraulic siphon brings the spring varying fluxes of water that cycle over time. If these flows are only one flowpath in the total spring system, the influx of water from the siphon may have strong effects on water quality, but be difficult to detect in hydrograph data during spring storm response. Oscillations in electrical conductivity data were observed at Byrds Mill Spring, Pontotoc County, Oklahoma (USA). Byrds Mill Spring is the largest spring in Oklahoma by volume, and oscillations in electrical conductivity were observed during a set of extreme precipitation events in May 2015. A data logger placed at the spring's outflow recorded the electrical conductivity of the spring's oscillating between 520 ?S/cm and 10 ?S/cm multiple times while discharge remained steady. A numerical tank model was developed to simulate the electrical conductivity chemograph of Byrds Mill Spring to test hypotheses about the geometry of the siphoning system. The model simplified the karst system as a tank connected to a siphoning drain and a tank connected to a non-siphoning drain joined together by mixing at a T-junction. Using this approach, the model was able to reproduce key features of the Byrds Mill Springs chemograph. The model results provide controls on where the siphon may be located and the dimensions of the siphon system.

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GroMoPo Metadata for Mar Del Plata landfill transport model
Created: Feb. 7, 2023, 7:19 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The distribution coefficient (Kd) expresses the relationship between the concentration of an element, which is adsorbed in the solid surface and its remaining concentration in the solution. The Kd is a very important factor in reactive transport, representing the source/sink term, and explaining the difference between the velocity of transport of non-conservative elements (Kd > 0) and water flow velocity. In this paper, the Kd value for Zn element in loess like sediments forming the Pampeano aquifer is determined and this value is used in the modeling of reactive transport from the landfill of the city of Mar del Plata (Argentina). The determination of Kd value was done by means of batch experiments. The results obtained showed good agreement with Freundlich isotherm, with a value of K-F = 300.95 ml g(-1) and a super index value b of 0.3961. These values were applied to reactive transport modeling using Visual Modflow code. The Zn plume obtained showed the low mobility of the element in the oxidizing conditions of the environment.

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GroMoPo Metadata for Rio Salado MODFLOW model
Created: Feb. 7, 2023, 7:20 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The Rio Salado catchment covers 170,000km2 of the Buenos Aires province, Argentina. The area suffers from persistent flooding situations that affect a large proportion of the catchment and hence imposes a severe constraint in the existing production levels and in the realisation of the fall economic potential of the region. The complexity of the landscape and the delicate groundwater-surface water interaction in a large dune field area made it essential to develop different approaches to model such interaction, as part of the study for an Integrated Master Plan for the whole basin. An approach using MODFLOW proved to be useful at a regional and prefeasibility level to generate flood risk maps and estimate net benefits for different drainage schemes. However ISISMOD, a groundwater model coupled with a surface water model proved to be a key water resource management tool to support feasibility studies and the detailed design of a drainage network capable of removing flood waters without detriment to the wetlands and fresh groundwater lenses of the area during dry periods.

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GroMoPo Metadata for Dulce Stream Watershed groundwater pollution model
Created: Feb. 7, 2023, 7:22 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

This paper proposes a modeling approach for assessing changes in groundwater pollution hazard under two different socio-economic and environmental scenarios: The first one considers an exponential growth of agriculture land-use (Relegated Sustainability), while the other deals with regional economic growth, taking into account, the restrictions put on natural resources use (Sustainability Reforms). The recent (2011) and forecasted (2030) groundwater pollution hazard is evaluated based on hydrogeological parameters and, the impact of land-use changes in the groundwater system, coupling together a land-use change model (Dyna-CLUE) with a groundwater flow model (MODFLOW), as inputs to a decision system support (EMDS). The Dulce Stream Watershed (Pampa Plain, Argentina) was chosen to test the usefulness and utility of this proposed method. It includes a high level of agricultural activities, significant local extraction of groundwater resources for drinking water and irrigation and extensive available data regarding aquifer features. The Relegated Sustainability Scenario showed a negative change in the aquifer system, increasing (+ 20%; high-very high classes) the contribution to groundwater pollution hazard throughout the watershed. On the other hand, the Sustainability Reforms Scenario displayed more balanced land-use changes with a trend towards sustainability, therefore proposing a more acceptable change in the aquifer system for 2030 with a possible 2% increase (high-very high classes) in groundwater pollution hazard. Results in the recent scenario (2011) showed that 54% of Dulce Stream Watershed still shows a moderate to a very low contribution to groundwater pollution hazard (mainly in the lower area). Therefore, from the point of view of natural resource management, this is a positive aspect, offering possibilities for intervention in order to prevent deterioration and protect this aquifer system. However, since it is quite possible that this aquifer status (i.e. groundwater quality) changes in the near future, the implementation of planning measures and natural resource management is recommended. (C) 2015 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Del Azul basin SWAT-MODFLOW model
Created: Feb. 7, 2023, 7:23 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The study of the dynamics of anthropic disturbances that have an effect on the hydrological systems in plains requires integral simulation tools for their diagnosis. The objective of this article is, first, to analyse and reproduce the spatio-temporal interactions between groundwater (GW) and surface water, net recharge, GW level, surface run-off, and evapotranspiration in the upper creek basin of Del Azul, which is located in the centre of the province of Buenos Aires, Argentina, and second, to obtain insights to apply the methodology to other similar situations. For this purpose, a model coupling the semidistributed hydrological model (Soil and Water Assessment Tool [SWAT]) and the hydrogeological model (MODFLOW) has been used. A simulation was carried out for a period of 13 years (2003-2015) on a daily scale. The application of the SWAT-MODFLOW coupling gave good results based on the adjustment between the calculated flows and levels, reaching a Nash-Sutcliffe of 0.6 and R(2)0.6 at the Seminario hydrometric station located at the watershed outlet point. According to the annual average balance, out of the total rainfall, evapotranspiration accounts for 85%, recharge accounts for 10.2%, and surface run-off accounts for 4.8%. Annual and monthly trends of the stream-aquifer interaction were determined, obtaining on average an annual GW discharge of 34 mm and an annual average recharge of the stream to the aquifer of 1.4 mm. Monthly GW discharges are higher in winter-spring (July to December with an average of 3.3 mm) and lower in summer-autumn (January to June with an average of 2.8 mm). The monthly average recharge of the stream towards the aquifer varies from 0.02 to 0.36 mm and is higher in March, May, and August, when water excess is produced in the basin. Through the analysis of coupled modelling, it is possible to analyse and reproduce the spatio-temporal transitions of flow existing between the stream, the hyporheic zone, and the aquifer.

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GroMoPo Metadata for Peninsula Valdes (Patagonia) groundwater model
Created: Feb. 7, 2023, 7:25 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The Peninsula Vald,s, in northeastern Patagonia, Argentina, is characterised by its arid climate and the lack of perennial watercourses; thus, all economic activities depend on the groundwater resources. Water demand is mainly associated with tourism, which is centralised in Puerto Piramides and supplied by a water desalination plant, and to sheep farming, supplied by the local aquifer. Due to the exponential growth of tourism, the government is planning to exploit groundwater and convey it by aqueduct to the abovementioned locality. The objectives of this study were to corroborate the conceptual geohydrological model, to develop a mathematical model to simulate the response of the aquifer to different scenarios, and to assess the incidence of water input into the system as a variable-a function that poses difficulties in the models for arid regions. The Visual Modflow 4.1 code was used, calibrating it in trial-and-error mode, changing the recharge and hydraulic conductivity parameters with different variants in the recharge zone and in the inclusion or exclusion of the evapotranspiration module. Results indicate the importance of the recharge analysis by treating rainfall at daily time steps. The adjusted model was exposed to four scenarios with variations in water input and in output by pumping. It can be concluded that under different input conditions, but with a controlled extraction, the system responds in a sustainable manner.

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GroMoPo Metadata for Altar Valley (High Andres) model
Created: Feb. 7, 2023, 7:26 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

Groundwater and surface water sourced from the high Andes of Argentina are highly important for societal, agricultural, and domestic usage in the foothills and valleys, less than hundred kilometers away from the headwaters. Despite their importance, efforts to provide estimates and predictions of surface water and especially groundwater sources and sinks have been limited. During most of the year, precipitation in the high Andes falls primarily as snow, with minimal rainfall over the summer. A widespread lack of measurements and statistical analysis in the region makes it difficult to understand groundwater storage and flow patterns in the Andean watersheds. The contribution of mountain snowmelt to groundwater is a key component of recharge to this area. While this study is limited to a small watershed in the Altar valley of the Central Andes of Argentina, it is representative of most of the Dry Andes region, which runs from Bolivia south to a latitude of 35S between Argentina and Chile. This region is characterized by steep and abrupt topography, highly fractured bedrock, and large fault systems. Here, we investigate the groundwater flow system through observations from pressure transducers and weather stations installed by a mining company exploring the area. We use this data to create a MODFLOW groundwater model of the watershed and develop then a sensitivity analysis to gain insight into the hydrologic system. We explore changes in hydraulic conductivity with depth and reduction in recharge due to uncertainties in sublimation and evaporation and potential future trends. We then analyze heads, surface outflows to assess the impact of these changes within the hydrologic system. In addition, ages distribution in particles from the one well and the river are analyzed. ? This research contributes to the understanding of groundwater recharge and discharge estimates and the hydraulic behavior of upland mountainous watersheds toward better water management in the area.

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GroMoPo Metadata for Azul River basin regional MODFLOW model
Created: Feb. 7, 2023, 7:28 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

A three-dimensional modular model (MODFLOW) was used to simulate groundwater flow in the Azul River basin. Buenos Aires Province. Argentina: in order to assess the correctness of the conceptual model of the hydrogeological system. Simulated heads satisfactorily match observed heads in the regional water-table aquifer. Model results indicate that: (1) groundwater recharge is not uniform throughout the region but is best represented by three recharge rates, decreasing downgradient, similar to the distribution of soils and geomorphological characteristics; and (2) evapotranspiration rates are larger than previous estimates, which were made by using the Thornthwaite-Mather method. Evapotranspiration rates estimated by MODFLOW agree with results of independent studies of the region. Model results closely match historical surface-flow records, thereby suggesting that the model description of the aquifer-river relationship is correct.

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GroMoPo Metadata for Pampa Plain groundwater-lake model
Created: Feb. 7, 2023, 7:29 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

This paper gives an account of the assessment and quantification of the water balance and the hydrogeological processes related to lake-groundwater interaction in the Pampa Plain by using hydrogeochemical, isotopic and flow numerical modeling techniques. La Salada is a permanent shallow lake, with an area of 5.8 km(2), located on the SE of Buenos Aires Province. A total of 29 lake water samples and 15 groundwater samples were collected for both hydrochemical analysis and environmental stable isotope determination. Water table depths were measured in wells closed to the lake. Groundwater samples appear grouped on the Local Meteoric Water Line, suggesting a well-mixed system and that rainfall is the main recharge source to the aquifer. Water evaporation process within La Salada is also corroborated by its isotopic composition. The model that best adjusts to La Salada Lake hydrochemical processes includes evaporation from groundwater, calcite precipitation with CO2 release and cationic exchange. The annual water balance terms for the lake basin indicates for each hydrological component the following values: 1.16 E-08 m(3) rainfall, 8.15 E-07 m(3) evapotranspiration, 1.90 E-06 m(3) runoff, 1.55 E-07 m(3) groundwater recharge, 6.01 E-06 m(3) groundwater discharge to the lake, 9.54 E-06 m(3) groundwater discharge to the river, 5.00 E-05 m(3) urban extraction and 4.90 E-06 m(3) lake evaporation. Integrated analysis of hydrochemical and isotopic information helped to calibrate the groundwater flow model, to validate the conceptual model and to quantitatively assess the basin water balance.

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GroMoPo Metadata for Choele Choel Island (Patagonia) MODFLOW + HEC-RAS model
Created: Feb. 7, 2023, 7:31 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

This work describes the application of a methodology designed to improve the representation of water surface profiles along open drain channels within the framework of regional groundwater modelling. The proposed methodology employs an iterative procedure that combines two public domain computational codes, MODFLOW and HEC-RAS. In spite of its known versatility, MODFLOW contains several limitations to reproduce elevation profiles of the free surface along open drain channels. The Drain Module available within MODFLOW simulates groundwater flow to open drain channels as a linear function of the difference between the hydraulic head in the aquifer and the hydraulic head in the drain, where it considers a static representation of water surface profiles along drains. The proposed methodology developed herein uses HEC-RAS, a one-dimensional. (1D) computer code for open surface water calculations, to iteratively estimate hydraulic profiles along drain channels in order to improve the aquifer/drain interaction process. The approach is first validated with a simple closed analytical solution where it is shown that a Piccard iteration is enough to produce a numerically convergent and mass preserving solution. The methodology is then applied to the groundwater/surface water system of the Choele Choel Island, in the Patagonian region of Argentina. Smooth and realistic hydraulic profiles along drains are obtained while backwater effects are clearly represented. (C) 2008 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Lower Piura Sub-basin Aquifer model
Created: Feb. 7, 2023, 7:32 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

The Lower Piura Sub-basin Aquifer is a vital source of water in the north of Peru. Despite its importance, few local studies describe this formation. Most are limited to reporting hydraulic characteristics and abstraction rates, lacking a broader analysis. This article characterizes the aquifer, presenting the development of a conceptual and mathematical model with sparse data, completed using several assumptions and interpolations. The model will improve understanding of the aquifer system and the impacts of abstraction. The aquifer system includes an unconfined aquifer connected to a confined aquifer through an aquitard. Steady-state and transient-state models from 2004 to 2014 were used. The development and calibration of the model have led to proper identification of hydraulic parameters and boundary conditions, clarifying the dynamics of the system. In the unconfined aquifer, groundwater flows towards the south-west without significant variation in the water table. Conversely, the piezometric surface of the confined aquifer shows a cone of depression with a falling trend of 1.6 m/year between 2004 and 2014. Outflows include abstractions (48.42 x 10(6) m(3)/year), gaining surface waters (6.33 x 10(6) m(3)/year), and sea discharge (18.50 x 10(6) m(3)/year). Inflows are from irrigation return (34.67 x 10(6) m(3)/year) and from the Higher Piura Aquifer (27.23 x 10(6) m(3)/year). The imbalance of 11.24 x 10(6) m(3)/year is abstracted from aquifer storage leading to hydraulic head drops and flow changes, revealing a clearly unsustainable overexploitation scenario that impacts more intensively the confined aquifer. Model results provide the basis to understand how this is happening and help to suggest strategies to alleviate the current aquifer situation.

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GroMoPo Metadata for Manglaralto coastal aquifer model
Created: Feb. 7, 2023, 7:45 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

Coastal aquifers are part of the natural resources contributing to local development and promote resilience in the most vulnerable communities near the sea. Manglaralto, an Ecuadorian coastal parish, is affected by water resource scarcity. The increase in salinity and deterioration of the water quality is generated by the local and floating population's demand, causing an increase in the Total Dissolved Solids (TDS) concentrations and decreasing the aquifer's piezometric levels. The aim is to establish a numerical model of flow and transport of the Manglaralto coastal aquifer by using hydrogeological data and Visual Transin software, relating the hydraulic importance of a dyke's design ("tape") and its impact on the quality of the water. The methodology is (i) hydrogeological database analysis, (ii) the system's recharge concerning the soil water balance, (iii) the boundary conditions of the flow and transport model and, (iv) the results and validation of the numerical simulation. The results configure the importance of the coastal aquifer's artificial recharge in the area where the tape is located, as reflected in the increase in piezometric levels and the decrease in salinity in wells near the sea. In conclusion, the numerical model of flow and transport allows expanding the knowledge of the variation of the piezometric levels and TDS concentrations over time, the importance of recharge in the hydrogeological system's operation, and correct community management resilience and projection to sustainable development.

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GroMoPo Metadata for Chambo aquifer model
Created: Feb. 7, 2023, 7:47 p.m.
Authors: None · Andres Quichimbo

ABSTRACT:

The Chambo river basin, in central Ecuador, belongs to the watershed of the upper Pastaza, a major north-western tributary of the Amazon. It is a densely inhabited region, where the drinkable water infrastructures of the cities existing within the basin exclusively rely on the groundwater extracted from the Chambo aquifer. The results thrown by a study based on the use of the C-14 isotopes as groundwater tracers, accompanied by an overall scarcity of scientific knowledge about this hydrological system, have lead the local communities and decision makers to think that the Chambo aquifer is fossil. In this study we demonstrate that the Chambo aquifer is actually recharged over time, providing an estimate of the recharge, and showing that it is caused by the ongoing melting of the glaciers existing on top of the Chimborazo volcano. Such a scenario is compatible with the C-14 analysis, which showed that the aquifer groundwater is about 8000 years old, and suggests that a lateral water inflow actually feeds the Chambo aquifer, highlighting the present influence of the global climate change on the future water availability in central Ecuador.

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GroMoPo Metadata for Goksu Deltaic Plain model
Created: Feb. 7, 2023, 7:50 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Unplanned exploitation of groundwater from coastal aquifers may cause salt water intrusion in coastal aquifers. Coastal areas are generally overpopulated with fertile agricultural lands and diversified irrigated farming activities. The objective of this study was to develop a model to control/prevent seawater intrusion into the coastal aquifer with a case study of the Silifke-Goksu Deltaic Plain. A computer program for the simulation of three-dimensional variable density groundwater flow, SEAWAT, is used to model the seawater intrusion mechanism of the Goksu Deltaic Plain along the Mediterranean coast of Turkey. The calibration analysis of the developed seawater intrusion model is performed using field measured data in the water-year of 2008 including static groundwater head, electrical conductivity, total dissolved solid (TDS), and chloride concentration values collected from 23 observation wells and the existing data which were compiled and reviewed. The main objectives for applying the seawater intrusion model to the Goksu Deltaic Plain were (1) to determine the hydraulic and hydrogeologic parameters of the aquifer, (2) to estimate the spatial variation of the salt concentration in the aquifer and (3) to investigate the impact of the increase and decrease in groundwater extractions. The simulation results show that the Goksu Deltaic Plain aquifer is especially sensitive to the increase in groundwater extraction. (C) 2012 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Grande Glorieuse coral island model
Created: Feb. 7, 2023, 7:51 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

In coral islands, groundwater is a crucial freshwater resource for terrestrial life, including human water supply. Response of the freshwater lens to expected climate changes and subsequent vegetation alterations is quantified for Grande Glorieuse, a low-lying coral island in the Western Indian Ocean. Distributed models of recharge, evapotranspiration and saltwater phytotoxicity are integrated into a variable-density groundwater model to simulate the evolution of groundwater salinity. Model results are assessed against field observations including groundwater and geophysical measurements. Simulations show the major control currently exerted by the vegetation with regards to the lens morphology and the high sensitivity of the lens to climate alterations, impacting both quantity and salinity. Long-term changes in mean sea level and climatic conditions (rainfall and evapotranspiration) are predicted to be responsible for an average increase in salinity approaching 140 % (+8 kg m(-3)) when combined. In low-lying areas with high vegetation density, these changes top +300 % (+10 kg m(-3)). However, due to salinity increase and its phytotoxicity, it is shown that a corollary drop in vegetation activity can buffer the alteration of fresh groundwater. This illustrates the importance of accounting for vegetation dynamics to study groundwater in coral islands.

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GroMoPo Metadata for Monterey sea water intrusion model
Created: Feb. 7, 2023, 7:52 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

This study presents a method to assess the contributions of 21st-century sea-level rise and groundwater extraction to sea water intrusion in coastal aquifers. Sea water intrusion is represented by the landward advance of the 10,000 mg/L iso-salinity line, a concentration of dissolved salts that renders groundwater unsuitable for human use. A mathematical formulation of the resolution of sea water intrusion among its causes was quantified via numerical simulation under scenarios of change in groundwater extraction and sea-level rise in the 21st century. The developed method is illustrated with simulations of sea water intrusion in the Seaside Area sub-basin near the City of Monterey, California (USA), where predictions of mean sea-level rise through the early 21st century range from 0.10 to 0.90 m due to increasing global mean surface temperature. The modeling simulation was carried out with a state-of-the-art numerical model that accounts for the effects of salinity on groundwater density and can approximate hydrostratigraphic geometry closely. Simulations of sea water intrusion corresponding to various combinations of groundwater extraction and sea-level rise established that groundwater extraction is the predominant driver of sea water intrusion in the study aquifer. The method presented in this work is applicable to coastal aquifers under a variety of other scenarios of change not considered in this work. For example, one could resolve what changes in groundwater extraction and/or sea level would cause specified levels of groundwater salinization at strategic locations and times.

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GroMoPo Metadata for Pampa del Tamarugal 2006 regional model
Created: Feb. 7, 2023, 7:54 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The Pampa del Tamarugal Aquifer (PTA) is an important source of groundwater in northern Chile. In this study, a groundwater flow model of this aquifer is developed and calibrated for the period 1983-2004. The model reproduces the observed flow-field and the water balance components reasonably well. Five scenarios are defined to evaluate the response to different pumping situations. These scenarios show that groundwater heads will continue to decrease with the present pumping discharge rates. To account for variations in the model results due to uncertainties in average recharge rates, randomly generated recharge realizations with different levels of uncertainty are simulated. Evaporation flow rates and groundwater flowing out of the modelled area seem unaffected by the recharge uncertainty, whereas the storage terms can vary considerably. For the most intensive pumping scenario under the generated random recharge rates, it is unlikely that the cumulative discharged volume from the aquifer, at the end of the simulation period, will be larger than 12% of the estimated groundwater reserve. Fluctuations in simulated groundwater heads due to uncertainties in the average recharge values are more noticeable in certain areas. These fluctuations could explain unusual behaviour in the observed groundwater heads in these areas.

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GroMoPo Metadata for Upper Santiago Valley Aquifer model
Created: Feb. 7, 2023, 7:55 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The use of groundwater as water supply has increased dramatically in Santiago, Chile, during the last decades, and there is a need for accurately estimating the actual groundwater supply capacity in the upper Santiago Valley aquifer. The behavior of this aquifer was studied in order to determine the availability of water and the long-range sustainable extraction rate. Water-table depths were simulated using a numerical model with information on recharge from the last 48 years under different extraction policies. With this series of groundwater level data, groundwater level probability distribution functions were determined and extraction statistics were estimated by fitting time series models and by using the crossing theory. With this information, it has been possible to calculate the risk of being unable to supply groundwater demand because the results verify that only 67% of the water rights granted are able to be extracted on a sustained basis with a 90% exceedance probability. Furthermore, the results obtained demonstrate that the method is adequate for determining exceedance probabilities of groundwater flow.

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GroMoPo Metadata for Pampa del Tamarugal 2016 regional model
Created: Feb. 7, 2023, 7:57 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

Aquifers within the Pampa del Tamarugal Basin (Atacama Desert, northern Chile) are the sole source of water for the coastal city of Iquique and the economically important mining industry. Despite this, the regional groundwater system remains poorly understood. Although it is widely accepted that aquifer recharge originates as precipitation in the Altiplano and Andean Cordillera to the east, there remains debate on whether recharge is driven primarily by near-surface groundwater flow in response to periodic flood events or by basal groundwater flux through deep-seated basin fractures. In addressing this debate, the present study quantifies spatial and temporal variability in regional-scale groundwater flow paths at 20.5A degrees S latitude by combining a two-dimensional model of groundwater and heat flow with field observations and delta O-18 isotope values in surface water and groundwater. Results suggest that both previously proposed aquifer recharge mechanisms are likely influencing aquifers within the Pampa del Tamarugal Basin; however, each mechanism is operating on different spatial and temporal scales. Storm-driven flood events in the Altiplano readily transmit groundwater to the eastern Pampa del Tamarugal Basin through near-surface groundwater flow on short time scales, e.g., 10(0)-10(1) years, but these effects are likely isolated to aquifers in the eastern third of the basin. In addition, this study illustrates a physical mechanism for groundwater originating in the eastern highlands to recharge aquifers and salars in the western Pampa del Tamarugal Basin over timescales of 10(4)-10(5) years.

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GroMoPo Metadata for Laguna Tuyajto saline lake model
Created: Feb. 7, 2023, 7:58 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

Estimating groundwater recharge in arid regions with seasonal snow cover, as in the Andean Altiplano of northern Chile, is important for sustainable development policies and the effective management of scarce resources in a high water demanding zone, as fragile ecosystems depends on a stable water contribution. This research aims to evaluate and quantify rainfall and snowfall contribution to aquifer recharge while assessing the factors that control the hydrodynamics in such areas, based in the knowledge of the better documented Tuyajto Lake in the Tuyajto catchment/basin. The modeling framework involves an energy balance of the snow cover, a soil water balance and a groundwater flow and chloride transport model. The basin average annual recharge is about 23% of average precipitation. Snowmelt contribution to recharge is important at altitudes above 4700 m a.s.l. during September, while rainfall is more important in February and March, during short intense precipitation events. The hydraulic conductivity of ignimbrites and other volcanic formations are the most important hydrogeological parameters controlling lake level and spring flow rates, while albedo and snowpack surface roughness length on the energy balance causes the greatest variation of lake level. Evaporation is the process controlling the variability of the lake level, as aquifer contribution remains relatively constant and springs flow variability is not enough to cause the observed variations, except during November. Possible buried salts deposits on the eastern edges of Pampa Colorada and Tuyajto Lake, together with volcanic HCl contribution, justify the high measured groundwater chloride concentrations. A recharge 2-3 higher than the current one is necessary to justify a lake level 40 m above its modern value during the Last Glacial period, giving insight into past hydrological changes in the basin due to climate variability. The knowledge gained can be applied to other high altitude volcanic basins with seasonal snow cover. (C) 2019 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Lower Cachapoal River irrigation canal model
Created: Feb. 7, 2023, 8 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

Agricultural production of high value crops in Chile's Central Valley is highly dependent on surface and groundwater resources. They are connected and together form an integrated hydrological system, the individual components of which have to be studied. This research is addressed to answering two questions: 1) to what extent do irrigation and canal seepage contribute to groundwater recharge and 2) what is the influence of the interactions between the Cachapoal River and ground water. The study was carried out from 2003 to 2007 in Peumo Valley (34.3 S, 71.3 W). In winter, the irrigation canal network intercepts and diverts surface runoff, which flows to flat areas and recharges groundwater. In summer, infiltration from the canals recharges the aquifer directly and partially compensates for water uptake from plants and evaporation. The effects of both interactions keep groundwater at a relatively constant level over the whole year. The water balance of the valley is strongly affected by agricultural practices, groundwater recharge mainly originating from irrigation loss (22%) and canal seepage (52%). It is important to know how management decisions, such as change in irrigation practices or canal lining, can affect the hydrological system and agricultural production within the valley.

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GroMoPo Metadata for Agua Verde aquifer (Atacama Desert) model
Created: Feb. 7, 2023, 8:01 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The hyper-arid conditions prevailing in Agua Verde aquifer in northern Chile make this system the most important water source for nearby towns and mining industries. Due to the growing demand for water in this region, recharge is investigated along with the impact of intense pumping activity in this aquifer. A conceptual model of the hydrogeological system is developed and implemented into a two-dimensional groundwater-flow numerical model. To assess the impact of climate change and groundwater extraction, several scenarios are simulated considering variations in both aquifer recharge and withdrawals. The estimated average groundwater lateral recharge from Precordillera (pre-mountain range) is about 4,482 m(3)/day. The scenarios that consider an increase of water withdrawal show a non-sustainable groundwater consumption leading to an over-exploitation of the resource, because the outflows surpasses inflows, causing storage depletion. The greater the depletion, the larger the impact of recharge reduction caused by the considered future climate change. This result indicates that the combined effects of such factors may have a severe impact on groundwater availability as found in other groundwater-dependent regions located in arid environments. Furthermore, the scenarios that consider a reduction of the extraction flow rate show that it may be possible to partially alleviate the damage already caused to the aquifer by the continuous extractions since 1974, and it can partially counteract climate change impacts on future groundwater availability caused by a decrease in precipitation (and so in recharge), if the desalination plant in Taltal increases its capacity.

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GroMoPo Metadata for Besease Inland Valley Bottom model
Created: Feb. 7, 2023, 8:03 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The harsh climate, shallow and erodible soils of low fertility uplands have led to farmers extending their cultivable areas to wetlands for optimal crop production since these systems have the potential for irrigation in the dry season. Inland valleys have been cited as having high potential for development of rice-based, small-holder farming systems at the village level, due to their specific hydrological conditions and relatively high soil fertility. This paper applies a 3D groundwater flow model, PM-WIN MODFLOW to simulate the groundwater heights of the two layered alluvial aquifer of the Besease Inland Valley Bottom. Groundwater recharge estimates from the watertable fluctuation method was used as the recharge input into the model. The results showed that groundwater levels ranged from 259.10-259.97 m in the wet season and 258.19 -258.86 m in the dry season for the simulation period. It also exhibited a form of interaction between the inland valley wetland and the bordering Oda River which varied over time depending on the river stage. The values for storage from the model were substantial and indicated the temporal variability in the watertable with continuous movement of water to and from storage over an annual cycle. Sensitivity analysis was performed, and model outputs were found to be highly sensitive to the catchment parameters such as horizontal hydraulic conductivity, specific yield and specific storage. The model helps to unravel the relationship between recurrent spatial and temporal patterns of watertable response within the inland valley bottom and their controlling factors.

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GroMoPo Metadata for Coastal heterogeneous aquifer model
Created: Feb. 7, 2023, 8:04 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Coastal plains are in the frontline of climate change. Predicted increase in recharge and sea level rise will alter groundwater flow, water quality distribution, recharge, and discharge considerably. This is simulated here in the Belgian western coastal plain. lt consists of a shore, dunes, and polder (low-lying area) with a heterogeneous groundwater reservoir of quaternary age. A three-dimensional density-dependent groundwater flow model based on numerous (hydro)geologic observations was made. First the current groundwater flow and distribution between fresh and salt water was simulated. Then the effects of a 15% recharge increase and 0.4 m of sea level rise in the next 100 years were modelled. Sea level rise results in an increased flow of fresh water toward the polder and a decreased flow toward the sea. An increase in recharge results in more water flowing toward both the polder and the sea. Brackish water present in the polder will be pushed back as is a current saltwater intrusion from the polder in the dunes. The simulations also show that groundwater levels will rise. This will put strain on the ecologically valuable dunes and the drainage system in the polders.

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GroMoPo Metadata for Falster Island saltwater intrusion model
Created: Feb. 7, 2023, 8:05 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Groundwater abstraction from coastal aquifers is vulnerable to climate change and sea level rise because both may potentially impact saltwater intrusion and hence groundwater quality depending on the hydrogeological setting. In the present study the impacts of sea level rise and changes in groundwater recharge are quantified for an island located in the Western Baltic Sea. The low-lying central area of the investigated part of the island was extensively drained and reclaimed during the second half of the 19th century by a system of artificial drainage canals that significantly affects the flow dynamics of the area. The drinking water, mainly for summer cottages, is abstracted from 11 wells drilled to a depth of around 20 m into the upper 5-10 m of a confined chalk aquifer, and the total pumping is only 5-6% of the drainage pumping. Increasing chloride concentrations have been observed in several abstraction wells and in some cases the WHO drinking water standard has been exceeded. Using the modeling package MODFLOW/MT3D/SEAWAT the historical, present and future freshwater-sea water distribution is simulated. The model is calibrated against hydraulic head observations and validated against geochemical and geophysical data from new investigation wells, including borehole logs, and from an airborne transient electromagnetic survey. The impact of climate changes on saltwater intrusion is found to be sensitive to the boundary conditions of the investigated system. For the flux-controlled aquifer to the west of the drained area only changes in groundwater recharge impacts the freshwater-sea water interface whereas sea level rise does not result in increasing sea water intrusion. However, on the barrier islands to the east of the reclaimed area, below which the sea is hydraulically connected to the drainage canals, and the boundary of the flow system therefore controlled, the projected changes in sea level, groundwater recharge and stage of the drainage canals all have significant impacts on saltwater intrusion and the chloride concentrations found in abstraction wells.

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GroMoPo Metadata for Bengal Basin regional model
Created: Feb. 7, 2023, 8:07 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Quantitative evaluation of management strategies for long-term supply of safe groundwater for drinking from the Bengal Basin aquifer (India and Bangladesh) requires estimation of the large-scale hydrogeologic properties that control flow. The Basin consists of a stratified, heterogeneous sequence of sediments with aquitards that may separate aquifers locally, but evidence does not support existence of regional confining units. Considered at a large scale, the Basin may be aptly described as a single aquifer with higher horizontal than vertical hydraulic conductivity. Though data are sparse, estimation of regional-scale aquifer properties is possible from three existing data types: hydraulic heads, C-14 concentrations, and driller logs. Estimation is carried out with inverse groundwater modeling using measured heads, by model calibration using estimated water ages based on C-14, and by statistical analysis of driller logs. Similar estimates of hydraulic conductivities result from all three data types; a resulting typical value of vertical anisotropy (ratio of horizontal to vertical conductivity) is 10(4). The vertical anisotropy estimate is supported by simulation of flow through geostatistical fields consistent with driller log data. The high estimated value of vertical anisotropy in hydraulic conductivity indicates that even disconnected aquitards, if numerous, can strongly control the equivalent hydraulic parameters of an aquifer system.

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GroMoPo Metadata for Nubian Aquifer paleo-saltwater model
Created: Feb. 7, 2023, 8:08 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

A numerical groundwater model of the Nubian Aquifer System was established to prove the influence of rising seawater levels on the groundwater salinity in northern Egypt over the last 140,000 years. In addition, the impact of a groundwater recharge scenario for these 140,000 years, involving climatic change, on the saltwater/freshwater interface was investigated. Saltwater intrusion induced by rising water levels of the Mediterranean Sea led to salinisation from the Mediterranean Sea to the Qattara depression. This modeling approach was supported by a density-driven model setup and calculation. The modelled saltwater/freshwater interfaces partially fitted the observed ones, especially in the southern half of the Qattara depression. In other parts of the northern Nubian Aquifer System, the ingression of salt water was modelled adequately, but in the west, small regions of the measured interface were not. The development in the Qattara depression (Egypt) and Sirte basin (Libya) were investigated in more detail. The different behaviour in the Sirte basin may be due to high evapotranspiration rates in some former periods, salt solutions from the pre-Quaternary layers or saltwater infiltration from sabkha-like recent salt-bearing sediments.

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GroMoPo Metadata for Wadden Sea advective transport model
Created: Feb. 7, 2023, 8:10 p.m.
Authors: None · Zamrsky, Daniel

ABSTRACT:

Effective porosity plays an important role in contaminant management. However, the effective porosity is often assumed to be constant in space and hence heterogeneity is either neglected or simplified in transport model calibration. Based on a calibrated highly parametrized flow model, a three-dimensional advective transport model (MODPATH) of a 1300 km(2) coastal area of southern Denmark and northern Germany is presented. A detailed voxel model represents the highly heterogeneous geological composition of the area. Inverse modelling of advective transport is used to estimate the effective porosity of 7 spatially distributed units based on apparent groundwater ages inferred from 11 C-14 measurements in Pleistocene and Miocene aquifers, corrected for the effects of diffusion and geochemical reactions. By calibration of the seven effective porosity units, the match between the observed and simulated ages is improved significantly, resulting in a reduction of ME of 99 % and RMS of 82 % compared to a uniform porosity approach. Groundwater ages range from a few hundred years in the Pleistocene to several thousand years in Miocene aquifers. The advective age distributions derived from particle tracking at each sampling well show unimodal (for younger ages) to multimodal (for older ages) shapes and thus reflect the heterogeneity that particles encounter along their travel path. The estimated effective porosity field, with values ranging between 4.3 % in clay and 45 % in sand formations, is used in a direct simulation of distributed mean groundwater ages. Although the absolute ages are affected by various uncertainties, a unique insight into the complex three-dimensional age distribution pattern and potential advance of young contaminated groundwater in the investigated regional aquifer system is provided, highlighting the importance of estimating effective porosity in groundwater transport modelling and the implications for groundwater quantity and quality assessment and management.

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GroMoPo Metadata for Madison Group, Powder River Basin USGS model
Created: Feb. 7, 2023, 8:11 p.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A digital simulation model was used to analyze regional ground-water flow in the Madison Group aquifer in the Powder River Basin in Montana and Wyoming and adjacent areas. Most recharge to the aquifer originates in or near the outcrop areas of the Madison in the Bighorn Mountains and Black Hills, and most discharge occurs through springs and wells. Flow through the aquifer in the modeled areas was approximately 200 cubic feet per second. The aquifer can probably sustain increased ground-water withdrawals of up to several tens of cubic feet per second, but these withdrawals probably would significantly lower the potentiometric surface in the Madison aquifer in a large part of the basin. (Woodard-USGS)

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GroMoPo Metadata for Llamara Salt Flat model
Created: Feb. 7, 2023, 8:13 p.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The Propopis tamarugo Phil, also known as Tamarugo, is an endemic and protected tree that survives in the Atacama Desert-a hyper arid and highly saline environment. The Tamarugo is threatened because of groundwater overexploitation, and its preservation depends on the soil moisture in the vadose zone, as many of the tree roots do not reach the current water table levels. To improve the estimation of soil moisture available for the Tamarugo trees, we applied a hydrogeological model that couples the unsaturated and saturated zones. The model was used to represent different groundwater exploitation and recharge scenarios between February 2006 and September 2030 to predict simultaneously groundwater levels and soil moisture. The model results show that even at locations where water table depletion is relatively small (1-1.5 m), soil moisture can drastically decrease (0.25-0.30 m(3)/m(3)). Therefore, Tamarugo survival can be better addressed, as the applied model provides a management tool to estimate response of Tamarugo trees to changing soil moisture. To further improve the model and its use to assess Tamarugo survival, more field data, such as soil hydrodynamic properties and soil moisture, should be collected. Additionally, relationships between the state of the Tamarugo trees and soil moisture should be further constructed. In this way, the developed model will be able to predict future conditions associated to the Tamarugo's health state.

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GroMoPo Metadata for Eckernfoerde Bay model
Created: Feb. 8, 2023, 2:36 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

We investigate (a) the submarine groundwater discharge (SGWD) defined as the net groundwater discharge to the sea and (b) the typical characteristics of the spatial distribution of the groundwater outflow at the sea bottom. The investigation concerns the Eckernforde Bay in the western Baltic Sea. A large-scale groundwater model was established in order to model groundwater flow toward the sea. Due to insufficient field data, different scenarios were simulated in order to approximate the value of SGWD. It is found that the probable range of SGWD in the study area per kilometer of the land-sea interface is from 0.05 to 0.07 m(3)/s. The distribution of the groundwater outflow rates at two sea bottom sites (pockmarks) was investigated using two approaches. First, density effects were neglected. Under this condition, the resulting discharge distribution at one site is approximately uniform whereas at the other site it is strongly non-uniform with high outflow rates at the edges of the pockmark. These differences are due to different hydraulic conductivity distributions of the aquifer. Second, the investigation by means of a density-driven flow model shows that the main effect of the saltwater is to displace the groundwater outflow from the central part of the pockmark to its edges. The approximately uniform distribution estimated by neglecting the density effects does not reflect the conditions at the sea bottom whereas the strongly non-uniform distribution does. The strongly lion-uniform distribution of the outflow rates at the sea bottom indicates that locally measured outflow rates can hardly be used for the estimation of mean outflow rates over large parts of the sea bottom. (C) 2002 Elsevier Science B.V. All rights reserved.

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GroMoPo Metadata for Nordenham cadmium leaching model
Created: Feb. 8, 2023, 2:38 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Over the last century, soils in the region of Nordenham in northern Germany received high loads of heavy-metals by air-borne immissions from a close-by metal smelter. Based on measured soil properties and cadmium contamination data the leaching of Cd to groundwater was predicted for Nordenham using a numerical transport model based on the convection-dispersion equation. The main objective in this study was to account for the spatial variability and uncertainty of Cd sorption controlling soil properties (pH, organic carbon content) and to analyze their propagation into the variance of area-related model outputs, i.e. Cd breakthrough concentrations at the groundwater surface. For this purpose a nested Monte-Carlo method was combined with deterministic numerical 1D simulations of Cd leaching. The transport model was parameterized without any parameter fitting involved. The validity of the model was verified by retrospective simulations from the initial operation of the smelter until the year of soil sampling. Forecast simulations were run for a period of 200 years. Predicted local scale Cd breakthrough concentrations at the groundwater surface were evaluated by spatial aggregation for single blocks at the field scale, yielding area-related concentrations with associated uncertainties from imprecise knowledge on local soil properties. Significant exceedance of the limit of the German drinking water ordinance of 5 mu g L-1 is observed on approximately 90% of the study area with the average point in time of limit value exceedance being the year 2066 and a 90% prediction interval of 2049-2092. At the end of the simulation period, Cd concentrations at the groundwater surface still increase on large parts of the study area. The spatially averaged Cd concentration is 19.89 mu g L-1 with a 90% prediction interval of 15.28-24.69 mu g L-1. Locally, however, concentrations larger than 60 mu g L-1 may be reached. Prediction uncertainty is only moderate and does not question the exceedance of the limit value on the majority of the regarded plots even for spatially averaged concentrations, unless measures to prevent leaching are taken, such as an increase of soil pH by liming. (C) 2009 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Rurscholle mine drainage model
Created: Feb. 8, 2023, 2:39 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A multilevel groundwater model was developed for the geological unit Rurscholle to forecast the impact of drainage from open pit mines on the groundwater balance and to evaluate measures to protect wetlands influenced by the drainage. The numerical model is based on a quasi-3D finite element scheme. Geological faults, wetlands, and the open pit mines are considered by a local mesh refinement. A special feature of the modelling of the open pit mines is the temporal change of the soil parameters caused by the mining process. The calibration challenges included the size of the modelling area and drainage wells with well filters in more than one aquifer. In order to reduce the number of calibration parameters, the soil parameters are divided into zones. The calibration results are presented and evaluated with examples.

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GroMoPo Metadata for DANUBIA MODFLOW decision-support model
Created: Feb. 8, 2023, 2:41 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The research project GLOWA-Danube, financed by the German Federal Government, is investigating long-term changes in the water cycle of the upper Danube river basin (77,000 km(2)) in light of global climatic change. Its aim is to build a fully integrated decision-support tool "DANUBIA" that combines the competence of 11 different research institutes in domains covering all major aspects governing the water cycle-from the formation of clouds, to groundwater flow patterns, to the behaviour of the water consumer. Both the influence of natural changes in the ecosystem, such as climate change, and changes in human behaviour, such as changes in land use or water consumption, are considered. DANUBIA is comprised of 15 individual disciplinary models that are connected via customized interfaces that facilitate network-based parallel calculations. The strictly object-oriented DANUBIA architecture was developed using the graphical notation tool UML (Unified Modeling Language) and has been implemented in Java code. All models use the same spatial discretisation for the exchange of data (1 x 1 km grid cells) but are using different time steps. The representation of a vast number of relevant physical and social processes that occur at different spatial and temporal scales is a very demanding task. Newly developed up- and downscaling procedures [Rojanschi, V., 2001. Effects of upscaling for a finite-difference flow model. Master's Thesis, Institut fur Wasserbau, Universitat Stuttgart, Stuttgart, Germany] and a sophisticated time controller developed by the computer sciences group [Hennicker, R., Barth, M., Kraus, A., Ludwig, M., 2002. DANUBIA: A Web-based modelling and decision support system for integrative global change research in the upper Danube basin. In: GSF (Ed.), GLOWA, German Program on Global Change in the Hydrological Cycle Status Report 2002. GSF, Munich, pp. 35-38; Kraus, A., Ludwig, M., 2003. GLOWA-Danube Papers Technical Release No. 002 (Danubia Framework), Software-Release No.: 0.9.2, Documentation Version: 0.10, Release Date: 27 March 2003] are required to solve the emerging problems. After a first successful public demonstration of the DANUBIA package (nine models) in May 2002 [Mauser, W., Stolz, R., Colgan, A., 2002. GLOWA-Danube: integrative techniques, scenarios and strategies regarding global change of the water cycle. In: GSF (Ed.), GLOWA, German Program on Global Change in the Hydrological Cycle (Phase I, 2000-2003) Status Report 2002. GSF, Munich, pp. 31-34], the research consortium is now preparing a first validation run of DANUBIA for the period 1995-1999 with all 15 models. After successful completion of the validation, a scenario run based on IPCC climate scenarios [IPCC, 2001. Climate Change 2001: Synthesis Report. In: Watson, R.T., Core Writing Team (Eds.), A Contribution of Working Groups I, II, and III to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA, 398pp] for a five year period between 2025 and 2040 will follow at the end of 2003. The research group "Groundwater and Water Resources Management" at the Institute of Hydraulic Engineering, Universitat Stuttgart, is contributing both a three-dimensional groundwater flow model of the catchment and an agent-based model for simulating water supply and distribution. This paper gives a general overview of the GLOWA-Danube project and describes the groundwater modeling segment. Nickel et al. deal with the water supply model in a second contribution to this special issue. A three-dimensional numerical groundwater flow model consisting of four main layers has been developed and is in a continual state of refinement (MODFLOW, [McDonald, M.G., Harbaugh, AW., 1988. A modular three-dimensional finite-difference ground-water flow model: US Geological Survey Techniques of Water-Resources Investigations, Washington, USA (book 6, Chapter A1)]). One main research focus has been on the investigation of upscaling techniques to meet the requirement of a fixed 1 x 1 km cell size. This cell size is compulsory for all models in DANUBIA in order to facilitate a one to one parameter exchange. In a second stage, a transport model (nitrogen) will be added (MT3D): [Zheng, C., Hathaway, D-L., 1991. MT3D: a new modular three-dimensional transport model and its application in predicting the persistence and transport of dissolved compounds from a gasoline spill, with implications for remediation. Association of Ground Water Scientists and Engineers Annual Meeting on Innovative Ground Water Technologies for the '90s, National Ground Water Association, Westerville, Ohio, USA. Ground Water 29 (5)]. (c) 2005 Elsevier Ltd. All rights reserved.

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GroMoPo Metadata for Beelitzhof (Berlin) saltwater upconing model
Created: Feb. 8, 2023, 2:42 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

To date, studies on the geological conditions in inland aquifers leading to pathways for upwelling deep saline groundwater due to pumping have not been published yet. Therefore, this paper conducted a theoretical modeling study to raise two hypotheses about deep saline-groundwater pathways leading to saltwater upconing below a pumping well in an inland aquifer based on the field situation at the Beelitzhof waterworks in southwestern Berlin (Germany), defined as follows: (1) there are windows in the Rupelian clay caused by glacial erosion, where their locations are uncertain, and (2) there are no windows in the clay, but the clay is partially thinned out but not completely removed by glacial erosion, so salt can merely come through the clay upward by diffusion and eventually accumulate on its top. These hypotheses were tested to demonstrate the impact of the lateral distance between windows in the clay and the well, as well as salt diffusion through the clay depending on its thickness on saltwater intrusion in the pumping well, respectively, using a density-dependent groundwater flow and solute transport model. Hypothesis 1 was validated with four scenarios that windows could occur in the clay at the site, and their locations under some conditions could significantly cause saltwater intrusion, while hypothesis 2 could be excluded, because salt diffusion through the clay with thickness greater than 1 m at the site was not able to cause saltwater intrusion.

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GroMoPo Metadata for Elbe River Valley embankment model
Created: Feb. 8, 2023, 2:44 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Ecosystems in river valleys are affected mainly by the hydraulic conditions in wetlands including groundwater dynamics. The quantitative prediction of changes in groundwater dynamics caused by river embankment relocation requires numerical modelling using a physically-based approach. Groundwater recharge from the intermittently flooded river plains was determined by a leakage approach considering soil hydraulic properties. For the study area in the Elbe river valley north of Magdeburg, Germany, a calibrated groundwater flow model was established and the groundwater dynamics for the present situation as well as for the case of embankment relocation were simulated over a 14-year time period. Changes in groundwater depth derived from simulated groundwater levels occurred only during flood periods. By analysing the spatial distributions of changes in statistical parameters, those areas with significant impact on the ecosystems by embankment relocation can be determined.

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GroMoPo Metadata for Groundwater Model for the Netherlands
Created: Feb. 8, 2023, 2:45 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

This publication discusses the computer program development of the "Groundwater Model for the Netherlands (LGM)". The publication is also intended to be a user's guide. It describes the various steps to be taken and procedures to be observed throughout the modelling process while applying LGM. LGM is a coupled system of so-called AQ-computer program packages and the Geographic Information System (GIS). The communication between the AQ-environment and the GIS-environment is based on ASCII files. The AQ programs are based on the numerical technique of finite elements (triangles and quadrilaterals). The saturated multi-aquifer geohydrological system consists of a series of aquifers separated by aquitards. Presently, the main output of simulations with LGM are maps of groundwater heads in aquifer, flux between the upper boundary of the geohydrological system and the top system, and fluxes across the aquitards. LGM can be used to assess the effect of various stresses upon the geohydrological system, for example due to changes in groundwater abstraction. LGM proves to be an efficient and versatile tool to address various types of geohydrological problems.

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GroMoPo Metadata for Nordfjord glacier ice model
Created: Feb. 8, 2023, 2:47 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Basal water pressure and water flow patterns are significant factors in controlling the behavior of an ice sheet, because they influence ice-sheet thickness, stability and extent. Water produced by basal melting may infiltrate the subsurface, or occur as sheet or channelized flow at the ice/bed interface. We examine subglacial groundwater conditions along a flowline of the Scandinavian ice sheet through Nordfjord, in the western fjords region of southern Norway, using a steady-state, two-dimensional groundwater-flow model. Meltwater input to the groundwater model is calculated by a two-dimensional, time-dependent, thermomechanically coupled ice-flow model oriented along the same flowline. Model results show that the subglacial sediments could not have transmitted all the meltwater out of the fjord during times of ice advance and when the ice sheet was at its maximum position at the edge of the continental shelf. In order for pore-water pressures to remain below the overburden pressure of the overlying ice, other paths of subglacial drainage are necessary to remove excess water. During times of retreat, the subglacial aquifer is incapable of transmitting all the meltwater that was probably generated. Pulses of meltwater reaching the bed could explain non-climatically driven margin readvances during the overall retreat phase.

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GroMoPo Metadata for Ovre Romerike aquifer MODFLOW model
Created: Feb. 8, 2023, 2:48 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Using a modified version of the USGS MODFLOW code, coupled with a Penman- Grindley type recharge model, it has been possible to produce a transient, 3- dimensional groundwater flow model of the Ovre Romerike aquifer. A steady state model has been calibrated against 183 regional water level observation data from autumm 1975 and against the flows in groundwater-fed springs and streams. The distribution of hydraulic conductivity calibrated using the steady state model was then used to simulate water table variations over a period in excess of 30 years at 3 observation wells. The results show a satisfactory fit with real data, allowing for the limited spatial resolution of the model. A sevenmonth running average filter has been applied to the re- charge data to simulate the damping effects of the unsaturated zone on recharge naxima and minima, resulting in an even better fit. The modelling work has enabled the project's participants to obtain a deeper understanding of the hydraulics of the aquifer, and has also indicated that hydraulic conductivity values obtained from grain size distributions tend to lead to underestimates of aquifer transmissivity. The model provides a framework for further modelling work on contaminant transport at Trandum land- fill.

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GroMoPo Metadata for Ria Formosa Coastal Lagoon nitrate model
Created: Feb. 8, 2023, 2:49 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

A numerical flow and transport model is developed to assess groundwater discharge and nutrient transport to the Ria Formosa coastal lagoon in southern Portugal. A total N load of 350 ton/year is estimated for the considered area, of which agriculture accounts for 73% of total N load, and domestic effluent and atmospheric deposition for the remaining 9% and 18% respectively. Model results suggest that nutrient recycling has led to the high concentrations observed in the Campina de Faro (M12) aquifer, but is still insufficient to account for observed values at the coastline. Furthermore results suggest that even for the best case mitigation scenario, good quality status will not be achieved by 2027, as mandated by the EU Water Framework Directive. (C) 2017 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

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GroMoPo Metadata for Guarani Aquifer Uruguay-Brazil border region model
Created: Feb. 8, 2023, 2:51 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The cities of Rivera and Santana do Livramento are located on the outcropping area of the sandstone Guarani Aquifer on the Brazil-Uruguay border, where the aquifer is being increasingly exploited. Therefore, recharge estimates are needed to address sustainability. First, a conceptual model of the area was developed. A multilayer, heterogeneous and anisotropic groundwater-flow model was built to validate the conceptual model and to estimate recharge. A field campaign was conducted to collect water samples and monitor water levels used for model calibration. Field data revealed that there exists vertical gradients between confining basalts and underlying sandstones, suggesting basalts could indirectly recharge sandstone in fractured areas. Simulated downward flow between them was a small amount within the global water budget. Calibrated recharge rates over basalts and over outcropping sandstones were 1.3 and 8.1% of mean annual precipitation, respectively. A big portion of sandstone recharge would be drained by streams. The application of a water balance yielded a recharge of 8.5% of average annual precipitation. The numerical model and the water balance yielded similar recharge values consistent with determinations from previous authors in the area and other regions of the aquifer, providing an upper bound for recharge in this transboundary aquifer.

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GroMoPo Metadata for Del Azul basin GW-SW model
Created: Feb. 8, 2023, 2:54 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The analysis of the impact of climate change on water resources in plains requires integral simulation tools that quantify topographic complexity and the strong interaction of groundwater and surfacewater components (GW-SW). The objective of this study is to implement a coupled hydrological-hydrogeological model under climate change scenarios in order to quantify the spatio-temporal dynamics of water balance and GW-SW interactions for the upper creek basin of Del Azul, which is located in the center of the province of Buenos Aires. The simulation was carried out for a baseline scenario calibrated and validated for the period 2003-2015 and contrasted with two scenarios of the regional climate model CCSM4, RCP (4.5 and 8.5) simulated for the period 2020-2050. First, the annual andmonthly anomalies of precipitation, temperature, surface runoff, evapotranspiration, soilmoisture, recharge, flow, aswell as the discharge, head level and reserves of groundwater are studied. Then the spatio-temporal anomalies of the GW-SWinteraction were analyzed and finallywet and dry periods by means of the standardized precipitation index and the annual water balance were studied. Simulation results show that climate change will significantly alter the spatio-temporal patterns of the GW-SW interaction as well as the water balance. These showed monthly, seasonal and annual variations. They show an increase in most of the components of the water balance towards the middle of the 21st century, except soil moisture. Regarding GW-SW interactions, the average annual discharge of the aquifer to the stream is expected to increase by 5% with RCP 4.5while itwill increase 24% with RCP 8.5. The recharge fromthe streamto the aquifer is expected to increase by 12% with RCP 4.5while a decrease by 5% with RCP 8.5. Concerning the SPI related to the water balance for the period 2020-2050, alternations of both the time and the length of dry and wet periods are expected for the two scenarios, with RCP 4.5 lowfrequency ofwet episodes, butwith a greater severity and permanence in time in contrast to RCP 8.5 that presents less frequency in dry periods, but with high permanence and severity. Climate change could alter groundwater mainly through changes in the recharge, leading tomodify groundwater levels and this will cause GW-SWflow to be reversed in some sectors of the stream by increasing or decreasing groundwater discharge into the stream. (C) 2020 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Apuae basin GPGPU model
Created: Feb. 8, 2023, 2:55 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The application of computer simulation models plays a significant role in the understanding of water dynamics in basins. The recent and explosive growth of the processing capabilities of General-Purpose Graphics Processing Units (GPGPUs) has resulted in widespread interest in parallel computing from the modelling community. In this paper, we present a GPGPU implementation of finite-differences solution of the equations of the 2D groundwater flow in unconfined aquifers for heterogeneous and anisotropic media. We show that the GPGPU-accelerated solution implemented using CUDA(1) C/C++ largely outperforms the corresponding serial solution in C/Cthornthorn. The results show that the GPGPU-accelerated implementation is capable of providing up to a 56-fold speedup in the solution using an ordinary office computer equipped with an inexpensive GPU(2) card. The code developed for this research is available for download and use at http://modelagemambientaluffs.blogspot.com.br/. (C) 2017 Elsevier Ltd. All rights reserved.
Note: Bounding box set based on locaiton of Brazil generally since exact location unknown.

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GroMoPo Metadata for Brotas WTF model
Created: Feb. 8, 2023, 2:57 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The estimation of groundwater recharge volume is a crucial requirement for the management of subsurficial water resources. The implementation of monitoring of the water table in shallow aquifers allows the seasonal variation in the water table induced by natural and anthropogenic factors. The assessment of groundwater recharge through analysis of the water table is commonly estimated by the water table fluctuation (WTF) method, an approach subject to uncertainty. Aiming to improve estimation of groundwater recharge, we proposed and tested a simple approach combining a numerical flow model with statistical analysis of cross-correlation. Our strategy produces a time-series of recharge that is able to generate the observed water-table fluctuation and may be especially useful in analyses of the hydrological balance. The obtained results showed that our approach was suitable and was capable of producing a time-series of monthly recharge, with groundwater recharge comprising 17% of total precipitation. The cross-correlation indicates that the most significant correlation (0.63) between precipitation and groundwater recharge is observed at a time lag of 1.5 months, suggesting fast movement of precipitated water toward the unsaturated zone.

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GroMoPo Metadata for Salt River Valley regional model
Created: Feb. 8, 2023, 2:58 a.m.
Authors: None · Kyle Compare

ABSTRACT:

SRV MODFLOW model development began in the late 1980's. Previous to the late 1980's, two groundwater models within the Salt River Valley had been developed. Thomas Anderson (1968) developed an electric analog model simulating the groundwater depletion of Central Arizona between 1923 and 1964. In 1982 Long et al. developed a USGS Trescott Model which simulated 1964 - 1977. Since the first SRV MODFLOW release in 1994 the model has undergone several updates with the most recent update completed in 2009 (transient calibration period 1983-2006). The SRV model geology was updated in 2010 and expanded the model grid to include the Hassayampa sub-basin. The next SRV model update is currently in the initial phase of development and plans to include a simulation of steady state (circa 1900) and transient (1901-2011) conditions.

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GroMoPo Metadata for Indian Creek basin USGS model
Created: Feb. 8, 2023, 3 a.m.
Authors: None · Kyle Compare

ABSTRACT:

The Indian Creek Basin in the southwestern Piedmont of North Carolina is one of five type areas studied as part of the Appalachian Valleys-Piedmont Regional Aquifer-System analysis. Detailed studies of selected type areas were used to quantify ground-water flow characteristics in various conceptual hydrogeologic terranes. The conceptual hydrogeologic terranes are considered representative of ground-water conditions beneath large areas of the three physiographic provinces--Valley and Ridge, Blue Ridge, and Piedmont--that compose the Appalachian Valleys-Piedmont Regional Aquifer-System Analysis area. The Appalachian Valleys-Piedmont Regional Aquifer-System Analysis study area extends over approximately 142,000 square miles in 11 states and the District of Columbia in the Appalachian highlands of the Eastern United States. The Indian Creek type area is typical of ground-water conditions in a single hydrogeologic terrane that underlies perhaps as much as 40 percent of the Piedmont physiographic province. The hydrogeologic terrane of the Indian Creek model area is one of massive and foliated crystalline rocks mantled by thick regolith. The area lies almost entirely within the Inner Piedmont geologic belt. Five hydrogeologic units occupy major portions of the model area, but statistical tests on well yields, specific capacities, and other hydrologic characteristics show that the five hydrogeologic units can be treated as one unit for purposes of modeling ground-water flow. The 146-square-mile Indian Creek model area includes the Indian Creek Basin, which has a surface drainage area of about 69 square miles. The Indian Creek Basin lies in parts of Catawba, Lincoln, and Gaston Counties, North Carolina. The larger model area is based on boundary conditions established for digital simulation of ground-water flow within the smaller Indian Creek Basin. The ground-water flow model of the Indian Creek Basin is based on the U.S. Geological Survey?s modular finite-difference ground-water flow model. The model area is divided into a uniformly spaced grid having 196 rows and 140 columns. The grid spacing is 500 feet. The model grid is oriented to coincide with fabric elements such that rows are oriented parallel to fractures (N. 72 E.) and columns are oriented parallel to foliation (N. 18 W.). The model is discretized vertically into 11 layers; the top layer represents the soil and saprolite of the regolith, and the lower 10 layers represent bedrock. The base of the model is 850 feet below land surface. The top bedrock layer, which is only 25 feet thick, represents the transition zone between saprolite and unweathered bedrock. The assignment of different values of transmissivity to the bedrock according to the topographic setting of model cells and depth results in inherent lateral and vertical anisotropy in the model with zones of high transmissivity in bedrock coinciding with valleys and draws, and zones of low transmissivity in bedrock coinciding with hills and ridges. Lateral anisotropy tends to be most pronounced in the north-northwest to south-southeast direction. Transmissivities decrease nonlineraly with depth. At 850 feet, depending on topographic setting, transmissivities have decreased to about 1 to 4 percent of the value of transmissivity immediately below the regolith-bedrock interface. The model boundaries are, for the most part, specified-flux boundaries that coincide with streams that surround the Indian Creek Basin. The area of active model nodes within the boundaries is about 146 square miles and has about 17,400 active cells. The numerical model is designed not as a predictive tool, but as an interpretive one. The model is designed to help gain insight into flow-system dynamics. Predictive capabilities of the numerical model are limited by the constraints placed on the flow system by specified fluxes and recharge distribution.

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GroMoPo Metadata for Guarani Aquifer Entre Rioas-Salto model
Created: Feb. 8, 2023, 3:01 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

The Water Department at the North Littoral Regional University Center of the Republic University (UDELAR) and the National Water Directorate of Uruguay (DINAGUA) developed a numerical model of the Guarani Aquifer for managing the thermal wells in the area of Concordia (Entre Rios, Argentina) and Salto (Uruguay). The model geometry was built integrating geological and geophysical information. The contact surfaces of the sedimentary package with basalt and basement was reconstructed. By reinterpreting pumping tests estimates transmissivity and storage coefficient. Due to the shortage of piezometric measures the calibration process was carried out simulating the evolution of the aquifer from 1992 to 2002, considering the piezometric levels obtained at the time a new well was drill. Through a series of model simulations the requirements that DINAGUA demands to grant operating licenses in Uruguayan were evaluated. By modelling a set of scenarios the minimum distance criterion that future wells must maintain with existing was assessed. The results showed that, some scenarios that meet the current criteria have a greater impact on the system than others who do not. This highlights the need to consider mathematical modelling in the criteria design for aquifer management, and especially in assessing the impact of specific actions on the system. Keywords: Guarani Aquifer, mathematical model, Well-management, policy evaluation.

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GroMoPo Metadata for South Portugal coastal groundwater model
Created: Feb. 8, 2023, 3:02 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Troia-Melides is a sandy area on SW Portugal, between Lisbon and Algarve, on the Atlantic Portuguese coast. The top north of the tract is a sandy peninsula about 10 kin long and 2 to 4 kin large, and is represented by recent dynamic sand-dune systems (Plio-Plistocene-Halocene) that extends south to the rocky Sines Cape, in a total-extension of 65 km (far beyond the zone covered by this work, that corresponds to northern half of this extension). The central zone of the littoral arch has sandstone cliffs headed by ancient dunes separated from the actual beach, which is continuous along the tract. A great diversity of important ecosystems characterises all the area, conferring it an enormous ecological fragility. Besides the dune and cliffs systems, 3 important coastal lagoons are also present. This diversity. of coastal environments was responsible for the definition of protected areas, classified according the more important species (birds, rare plants). Concerning flora, 45 families belonging to 246 different species where identified in a recent study. The major percentage occupies the inner dunes and includes several priority species (Directive 92/43/CEE) - Lonopsidium acaule, Thymus camphoratus, Linaria ficalhoana, etc. A scarce variety occurs in primary and embryonic dunes (being Ammophila arenaria the most common). This area has a great touristic potential, which is not always in conciliation with its fragile ecology. However, it's a relatively well-preserved tract and is nowadays under strict land management rules. In the study area, 3 touristic areas are approved, with a total number of 39,300 touristic beds, distributed by hotels and vacation houses. As a result, some delicate situations have occurred in natural ecosystems, namely aquifer exploitation, without regarding its recharge capacity, which lead to the infiltration of saline water in the aquifers of the littoral areas. With this work it was possible to understand the role of the saltwater intrusion due to the raise of buildings and fresh groundwater demands, and the previsible impacts on coastal ecosystems. Some procedures were undertaken in order to know the hydrogeochemistry and hydrodynamical characteristics of the aquifers in the area, namely defining the thickness of the fresh groundwater and the position of the interface with the saline water on the coastal area

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GroMoPo Metadata for West-Central New Jersey USGS model
Created: Feb. 8, 2023, 3:04 a.m.
Authors: None · Kyle Compare

ABSTRACT:

This study was undertaken to characterize ground- water flow in the Stony Brook, Beden Brook, and Jacobs Creek drainage basins in west-central New Jersey. The 89-square-mile study area is underlain by dipping beds of fractured siltstone, shale, and sandstone and by massive diabase sills. In all of the rocks, the density of interconnected fractures decreases with depth. A major fault extends through the study area, and rocks on both sides of the fault are extensively fractured. The average annual rates of precipitation and ground-water recharge in the study area are 45.07 inches and 8.58 inches, respectively. The rate of recharge to diabase rocks is about one-half the rate of recharge to other rocks. Part of the surface runoff from diabase rocks enters the ground-water system where it encounters more permeable rocks. Most ground water in the study area follows short, shallow flow paths. A three- dimensional finite-difference model of ground-water flow was developed to test hypotheses concerning geologic features that control ground-water flow in the study area. The decrease in the density of interconnected fractures with depth was represented by dividing the model into two layers with different hydraulic conductivity. The pinching out of water- bearing beds in the dip direction at land surface and at depth was simulated as a lower hydraulic conductivity in the dip direction than in the strike direction. This model can be used to analyze ground-water flow if the area of interest is more than about 0.5 square mile.

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GroMoPo Metadata for Williston Basin USGS model
Created: Feb. 8, 2023, 3:05 a.m.
Authors: None · Kyle Compare

ABSTRACT:

The U.S. Geological Survey developed a groundwater-flow model for the uppermost principal aquifer systems in the Williston Basin in parts of Montana, North Dakota, and South Dakota in the United States and parts of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability in the area. The assessment was done because of the potential for increased demands and stresses on groundwater associated with large-scale energy development in the area. As part of this assessment, a three-dimensional groundwater-flow model was developed as a tool that can be used to simulate how the groundwater-flow system responds to changes in hydrologic stresses at a regional scale. The three-dimensional groundwater-flow model was developed using the U.S. Geological Survey's numerical finite-difference groundwater model with the Newton-Rhapson solver, MODFLOW-NWT, to represent the glacial, lower Tertiary, and Upper Cretaceous aquifer systems for steady-state (mean) hydrological conditions for 1981?2005 and for transient (temporally varying) conditions using a combination of a steady-state period for pre-1960 and transient periods for 1961?2005. The numerical model framework was constructed based on existing and interpreted hydrogeologic and geospatial data and consisted of eight layers. Two layers were used to represent the glacial aquifer system in the model; layer 1 represented the upper one-half and layer 2 represented the lower one-half of the glacial aquifer system. Three layers were used to represent the lower Tertiary aquifer system in the model; layer 3 represented the upper Fort Union aquifer, layer 4 represented the middle Fort Union hydrogeologic unit, and layer 5 represented the lower Fort Union aquifer. Three layers were used to represent the Upper Cretaceous aquifer system in the model; layer 6 represented the upper Hell Creek hydrogeologic unit, layer 7 represented the lower Hell Creek aquifer, and layer 8 represented the Fox Hills aquifer. The numerical model was constructed using a uniform grid with square cells that are about 1 mile (1,600 meters) on each side with a total of about 657,000 active cells. Model calibration was completed by linking Parameter ESTimation (PEST) software with MODFLOW-NWT. The PEST software uses statistical parameter estimation techniques to identify an optimum set of input parameters by adjusting individual model input parameters and assessing the differences, or residuals, between observed (measured or estimated) data and simulated values. Steady-state model calibration consisted of attempting to match mean simulated values to measured or estimated values of (1) hydraulic head, (2) hydraulic head differences between model layers, (3) stream infiltration, and (4) discharge to streams. Calibration of the transient model consisted of attempting to match simulated and measured temporally distributed values of hydraulic head changes, stream base flow, and groundwater discharge to artesian flowing wells. Hydraulic properties estimated through model calibration included hydraulic conductivity, vertical hydraulic conductivity, aquifer storage, and riverbed hydraulic conductivity in addition to groundwater recharge and well skin. The ability of the numerical model to accurately simulate groundwater flow in the Williston Basin was assessed primarily by its ability to match calibration targets for hydraulic head, stream base flow, and flowing well discharge. The steady-state model also was used to assess the simulated potentiometric surfaces in the upper Fort Union aquifer, the lower Fort Union aquifer, and the Fox Hills aquifer. Additionally, a previously estimated regional groundwater-flow budget was compared with the simulated steady-state groundwater-flow budget for the Williston Basin. The simulated potentiometric surfaces typically compared well with the estimated potentiometric surfaces based on measured hydraulic head data and indicated localized groundwater-flow gradients that were topographically controlled in outcrop areas and more generalized regional gradients where the aquifers were confined. The differences between the measured and simulated (residuals) hydraulic head values for 11,109 wells were assessed, which indicated that the steady-state model generally underestimated hydraulic head in the model area. This underestimation is indicated by a positive mean residual of 11.2 feet for all model layers. Layer 7, which represents the lower Hell Creek aquifer, is the only layer for which the steady-state model overestimated hydraulic head. Simulated groundwater-level changes for the transient model matched within plus or minus 2.5 feet of the measured values for more than 60 percent of all measurements and to within plus or minus 17.5 feet for 95 percent of all measurements; however, the transient model underestimated groundwater-level changes for all model layers. A comparison between simulated and estimated base flows for the steady-state and transient models indicated that both models overestimated base flow in streams and underestimated annual fluctuations in base flow. The estimated and simulated groundwater budgets indicate the model area received a substantial amount of recharge from precipitation and stream infiltration. The steady-state model indicated that reservoir seepage was a larger component of recharge in the Williston Basin than was previously estimated. Irrigation recharge and groundwater inflow from outside the Williston Basin accounted for a relatively small part of total groundwater recharge when compared with recharge from precipitation, stream infiltration, and reservoir seepage. Most of the estimated and simulated groundwater discharge in the Williston Basin was to streams and reservoirs. Simulated groundwater withdrawal, discharge to reservoirs, and groundwater outflow in the Williston Basin accounted for a smaller part of total groundwater discharge. The transient model was used to simulate discharge to 571 flowing artesian wells within the model area. Of the 571 established flowing artesian wells simulated by the model, 271 wells did not flow at any time during the simulation because hydraulic head was always below the land-surface altitude. As hydraulic head declined throughout the simulation, 68 of these wells responded by ceasing to flow by the end of 2005. Total mean simulated discharge for the 571 flowing artesian wells was 55.1 cubic feet per second (ft3/s), and the mean simulated flowing well discharge for individual wells was 0.118 ft3/s. Simulated discharge to individual flowing artesian wells increased from 0.039 to 0.177 ft3/s between 1961 and 1975 and decreased to 0.102 ft3/s by 2005. The mean residual for 34 flowing wells with measured discharge was 0.014 ft3/s, which indicates the transient model overestimated discharge to flowing artesian wells in the model area. Model limitations arise from aspects of the conceptual model and from simplifications inherent in the construction and calibration of a regional-scale numerical groundwater-flow model. Simplifying assumptions in defining hydraulic parameters in space and hydrologic stresses and time-varying observational data in time can limit the capabilities of this tool to simulate how the groundwater-flow system responds to changes in hydrologic stresses, particularly at the local scale; nevertheless, the steady-state model adequately simulated flow in the uppermost principal aquifer systems in the Williston Basin based on the comparison between the simulated and estimated groundwater-flow budget, the comparison between simulated and estimated potentiometric surfaces, and the results of the calibration process.

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GroMoPo Metadata for La Plata urban recharge model
Created: Feb. 8, 2023, 3:07 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

Leakage from water mains, storm drainage and sewer systems in urban areas constitutes a source of recharge that is difficult to identify and quantify at a regional scale. The objective of this work is to apply a methodology that would make it possible to evaluate urban recharge at a regional scale, taking as a case study the city of La Plata (Argentina). In the study area, population growth and an increase in water demand has caused the intensive exploitation of groundwater with resulting alteration in groundwater flow. The methodology used was developed on the basis of a water balance and the simulation of the temporal evolution of the cones of depression and the volumes of water extracted from the aquifer. The method consists of adjusting the piezometry resulting from the numerical modelling to the measured piezometry, by means of the variation of the recharge parameter in the urban area. The results obtained make it possible to identify and quantify urban recharge, which in this case represents a volume of water similar to the recharge from precipitation.

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GroMoPo Metadata for Salinas-Patillas USGS model
Created: Feb. 8, 2023, 3:08 a.m.
Authors: None · Kyle Compare

ABSTRACT:

This report describes the geohydrology of the Salinas to Patillas area of the South Coastal Plain aquifer system in Puerto Rico.

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GroMoPo Metadata for Great Plains Cambrian/Ordovician USGS model
Created: Feb. 8, 2023, 3:10 a.m.
Authors: None · Kyle Compare

ABSTRACT:

This is a large modelencompassing the main aquifers of the central US a saprt of the USGS RASA program. There is no DOI associated with report, and reprot is too large to be uploaded, but can be found at https://pubs.usgs.gov/pp/1414c/report.pdf

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GroMoPo Metadata for Western San Joaquin Valley drain model
Created: Feb. 8, 2023, 3:11 a.m.
Authors: None · Kyle Compare

ABSTRACT:

Groundwater flow modeling was used to quantitatively assess the hydrologic processes affecting groundwater and solute movement to drain laterals. Modeling results were used to calculate the depth distribution of groundwater flowing into drain laterals at 1.8 m (drain lateral 1) and 2.7 m (drain lateral 2) below land surface. The simulations indicated that under nonirrigated conditions about 89% of the flow in drain lateral 2 was from groundwater originating from depths greater than 6 m below land surface. The deep groundwater has higher selenium concentrations than shallow groundwater. Simulation of irrigated conditions indicates that as recharge (deep percolation) increases, the proportional contribution of deep groundwater to drain lateral flow decreases. Groundwater flow paths and travel times estimated from the simulation results indicate that groundwater containing high concentrations of selenium (greater than 780-mu-g L-1) probably will continue to enter drain lateral 2 for decades.

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GroMoPo Metadata for Western San Joaquin Valley model calibration
Created: Feb. 8, 2023, 3:13 a.m.
Authors: None · Kyle Compare

ABSTRACT:

The occurrence of selenium in agricultural drain water from the western San Joaquin Valley, California, has focused concern on the semiconfined ground-water flow system, which is underlain by the Corcoran Clay Member of the Tulare Formation. A two-step procedure is used to calibrate a preliminary model of the system for the purpose of determining the steady-state hydraulic properties. Horizontal and vertical hydraulic conductivities are modeled as functions of the percentage of coarse sediment, hydraulic conductivities of coarse-textured (K(coarse)) and fine-textured (K(fine)) end members, and averaging methods used to calculate equivalent hydraulic conductivities. The vertical conductivity of the Corcoran (K(corc)) is an additional parameter to be evaluated. In the first step of the calibration procedure, the model is run by systematically varying the following variables: (1) K(coarse)/K(fine), (2) K(coarse)/K(corc), and (3) choice of averaging methods in the horizontal and vertical directions. Root mean square error and bias values calculated from the model results are functions of these variables. These measures of error provide a means for evaluating model sensitivity and for selecting values of K(coarse), K(fine), and K(corc) for use in the second step of the calibration procedure. In the second step, recharge rates are evaluated as functions of K(coarse), K(corc), and a combination of averaging methods. The associated K(fine) values are selected so that the root mean square error is minimized on the basis of the results from the first step. The results of the two-step procedure indicate that the spatial distribution of hydraulic conductivity that best produces the measured hydraulic head distribution is created through the use of arithmetic averaging in the horizontal direction and either geometric or harmonic averaging in the vertical direction. The equivalent hydraulic conductivities resulting from either combination of averaging methods compare favorably to field- and laboratory-based values.

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GroMoPo Metadata for Columbia Plateau Regional Aquifer System 1991 USGS model
Created: Feb. 8, 2023, 3:14 a.m.
Authors: None · Kyle Compare

ABSTRACT:

A MODFLOW model of the Columbia River flood basalts in the Pacific Northwest of the United Stares.

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GroMoPo Metadata for Upper Danube mountain MODFLOW model
Created: Feb. 8, 2023, 3:15 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

In large mountainous catchments, shallow unconfined alluvial aquifers play an important role in conveying Subsurface runoff to the foreland. Their relatively small extent poses a serious problem for ground water flow models on the river basin scale. River basin scale models describing the entire water cycle are necessary in integrated water resources management and to study the impact of global climate change on ground water resources. Integrated regional-scale models must use a coarse, fixed discretization to keep computational demands low and to facilitate model Coupling. This can lead to discrepancies between model discretization and the geometrical properties of natural systems. Here. an approach to overcome this discrepancy is discussed using the example of the German-Austrian Upper Danube catchment, where a coarse ground water flow model was developed using MODFLOW. The method developed uses a modified concept from a hydrological catchment drainage analysis in order to adapt the aquifer geometry such that it respects the numerical requirements of the chosen discretization, that is, the width and the thickness of cells as well as gradients and connectivity of the catchment. In order to show the efficiency of the developed method, it was tested and compared to a finely discretized ground water model of the Ammer subcatchment. The results of the analysis prove the applicability of the new approach and contribute to the idea of using physically based ground water models in large catchments.

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GroMoPo Metadata for Ammer Catchment model
Created: Feb. 8, 2023, 3:17 a.m.
Authors: None · Sacha Ruzzante

ABSTRACT:

In large mountainous catchments, shallow unconfined alluvial aquifers play an important role in conveying Subsurface runoff to the foreland. Their relatively small extent poses a serious problem for ground water flow models on the river basin scale. River basin scale models describing the entire water cycle are necessary in integrated water resources management and to study the impact of global climate change on ground water resources. Integrated regional-scale models must use a coarse, fixed discretization to keep computational demands low and to facilitate model Coupling. This can lead to discrepancies between model discretization and the geometrical properties of natural systems. Here. an approach to overcome this discrepancy is discussed using the example of the German-Austrian Upper Danube catchment, where a coarse ground water flow model was developed using MODFLOW. The method developed uses a modified concept from a hydrological catchment drainage analysis in order to adapt the aquifer geometry such that it respects the numerical requirements of the chosen discretization, that is, the width and the thickness of cells as well as gradients and connectivity of the catchment. In order to show the efficiency of the developed method, it was tested and compared to a finely discretized ground water model of the Ammer subcatchment. The results of the analysis prove the applicability of the new approach and contribute to the idea of using physically based ground water models in large catchments.

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GroMoPo Metadata for Amsterdam Water Supply model
Created: Feb. 8, 2023, 3:18 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Thr Amsterdam Water Supply has been using both the finite difference model MODFLOW (McDonald, M.G., Harbaugh, A.W., 1989. A modular three-dimensional finite-difference ground water flow model. Chapter Al, USGS, Book 6, Modeling Techniques) and the analytic element model MLAEM (Strack, O.D.L,, 1989. Groundwater Mechanics. Prentice Hall, Englewood Cliffs, NJ, (ISBN 0-13-365412-5); Strack, O.D.L,, 1999. Principles of the analytic element method. Journal of Hydrology, 226, 128-138) for many years. Choosing one or the other depends on the hydrologic system, its scale and the hydrologic features to be taken into account. Either method has its specific advantages. (C) 1999 Elsevier Science B.V. All rights reserved.

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GroMoPo Metadata for Netherlands analytic element model
Created: Feb. 8, 2023, 3:20 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

In 1985, I attended the first course on analytic element modeling in the Netherlands, where Professor Otto Strack of the University of Minnesota presented his newly conceived analytic element method (AEM; Strack 1989) at the Technical University Delft from which he graduated years before. While he explained the principles and applications of the method, I started to realize that the AEM might be uniquely suited to modeling detailed ground water flow systems covering large regions because it enables cutting, pasting, and linking of entire models as well as of model parts. In 1987, at the National Institute for Inland Water Management and Waste Water Treatment in the Netherlands (RIZA), there was much interest in national modeling in the Netherlands because of serious water management problems that first became apparent during the major drought of 1976. In fact, there existed a national water management system of models, called PAWN (Policy Analysis for Water management in the Netherlands; Rand Corporation 1982). PAWN is an integrated system of models for simulating the distribution over the numerous national and regional surface waters in this wet country and the effects on agriculture, nature (ecology), power plants, shipping, flushing of coastal areas against salt water intrusion, and drinking water. PAWN was lacking treatment of the ground water reservoir, which had become apparent in the policy analysis of 1985 (Pulles 1985). The NAtional GROundwater Model (NAGROM) should cover this gap as part of PAWN.

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GroMoPo Metadata for Kampinos National Park model
Created: Feb. 8, 2023, 3:21 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Hydrogeological modelling of the Kampinos National Park (KNP) region has been carried out. The KNP comprises a hydrogeological unit of valley relatively simple structure, and has been investigated empirically and theoretically since the 1970's. Results of numerical modelling given here provide a quantitative evaluation of hydrogeological parameters, recharging infiltration, river drainage and evapotranspiration processes (groundwater evaporation), water balance and the role of hydrodynamic zones in the recharge and drainage contribution in the water balance of the Vistula valley unit.

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GroMoPo Metadata for Jeffara of Medenine coastal aquifer MODFLOW-MT3DMS model
Created: Feb. 8, 2023, 3:23 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

The study of water quality and the quantification of reserves and their variations according to natural and anthropogenic forcing is necessary to establish an adequate management plan for groundwater resources. For this purpose, a modeling approach is a useful tool that allows, after calibration phase and verification of simulation, and under different scenarios of forcing and operational changes, to estimate and control the groundwater quantity and quality. The main objective of this study is to collect all available data in a model that simulates the Jeffara of Medenine coastal aquifer system functioning. To achieve this goal, a conceptual model was constructed based on previous studies and hydrogeological investigations. The regional groundwater numerical flow model for the Jeffara aquifer was developed using MODFLOW working under steady-state and transient conditions. Groundwater elevations measured from the piezometric wells distributed throughout the study area in 1973 were selected as the target water levels for steady state (head) model calibration. A transient simulation was undertaken for the 42 years from 1973 to 2015. The historical transient model calibration was satisfactory, consistent with the continuous piezometric decline in response to the increase in groundwater abstraction. The developed numerical model was used to study the system's behavior over the next 35 years under various constraints. Two scenarios for potential groundwater extraction for the period 2015-2050 are presented. The predictive simulations show the effect of the increase of the exploitation on the piezometric levels. To study the phenomenon of salinization, which is one of the most severe and widespread groundwater contamination problems, especially in coastal regions, a solute transport model has been constructed by using MT3DMS software coupled with the groundwater flow model. The best calibration results are obtained when the connection with the overlying superficial aquifer is considered suggesting that groundwater contamination originates from this aquifer. Recommendations for water resource managers The results of this study show that Groundwater resources of Jeffara of Medenine coastal aquifer in Tunisia are under immense pressure from multiple stresses. The water resources manager must consider the impact of economic and demographic development in groundwater management to avoid the intrusion of saline water. The results obtained presented some reference information that can serve as a basis for water resources planning. The model runs to provide information that managers can use to regulate and adequately control the Jeffara of Medenine water resources.

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GroMoPo Metadata for Viannos Basin (Crete) model
Created: Feb. 8, 2023, 3:24 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Recent climate change studies for the Mediterranean region have projected the near future temperature and precipitation trends. The increasing water demands for human consumption and agricultural purposes, as well as the potential overexploitation of the groundwater resources, in combination with the climatic projections are expected to affect the groundwater resources of the Mediterranean hydrological basins. This work focuses on the Viannos alluvial basin at the island of Crete, Greece. It considers primarily the increasing water demands for irrigation in the area of interest and the projected precipitation trend in the next five hydrological years for the island of Crete. The groundwater system is simulated based on the current hydrological/hydrogeological conditions of the basin and based on anticipated hydrological events. Scenarios concerning future precipitation trends and pumping schemes at existing wells are examined to assess the near-future stresses on the basin groundwater resources. Groundwater flow modeling is performed using the Visual Modflow software. Based on the study of different scenarios modeling results show that the aquifer is primarily affected during the dry period of the hydrological year. However, sufficiently replenishment is observed during the wet period as the highest water table drop is 0.65 m at the end of the 5 years modelling period. Therefore, the aquifer is not expected to face serious problems in the near future from the increased irrigation demands and from the short-term projected precipitation trends. Simulations for 10 and 20-year periods following the precipitation projections and the specified pumping schemes also show that the aquifer resources are not expected to be significantly affected.

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GroMoPo Metadata for Mediterranean karst MODFLOW-SEAWAT model
Created: Feb. 8, 2023, 3:25 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

The study and management of the groundwater resources of a large, deep, coastal, karstic aquifer represent a very complex hydrogeological problem. Here, this problem is successfully approached by using an equivalent porous continuous medium (EPCM) to represent a karstic Apulian aquifer (southern Italy). This aquifer, which is located on a peninsula and extends to hundreds of metres depth, is the sole local source of high-quality water resources. These resources are at risk due to overexploitation, climate change and seawater intrusion. The model was based on MODFLOW and SEAWAT codes. Piezometric and salinity variations from 1930 to 2060 were simulated under three past scenarios (up to 1999) and three future scenarios that consider climate change, different types of discharge, and changes in sea level and salinity. The model was validated using surveyed piezometric and salinity data. An evident piezometric drop was confirmed for the past period (until 1999); a similar dramatic drop appears to be likely in the future. The lateral intrusion and upconing effects of seawater intrusion were non-negligible in the past and will be considerable in the future. All phenomena considered here, including sea level and sea salinity, showed non-negligible effects on coastal groundwater.

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GroMoPo Metadata for Lakshadweep atoll model
Created: Feb. 8, 2023, 3:27 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

The groundwater is the only source of availability of fresh water in tiny coral islands. In the past decades, there has been growing demand for fresh water to meet the need of domestic besides other purposes. The aquifer system on these islands is fragile besides being subjected to various stresses like high subsurface discharge, increased abstraction, improper disposal of waste water and tidal waves of ocean all of which subject the aquifer prone to sea water intrusion and thus reduction and deterioration the water quality. Therefore, understanding the aquifer's behavior and then work out a sustainable option for fresh water is essential. The paper concerns optimizing of pumping and artificial recharge paces to reduce the effects of various stresses over tiny and fragile lens-shaped coral island aquifer system. The density driven ground water flow was simulated using SEAWAT (MODFLOW and MT3D based computer program) model. Detailed hydrogeological investigations were carried out to determine the quantity of freshwater that could be pumped to avoid the seawater intrusion into the aquifer through modeling. Initial heads, physical parameters and boundary conditions of the study area have been defined in the model based on field data, geophysical measurements and interpretations and hydrogeological studies. The model was calibrated by obtaining a match of computed and observed values of the water table, as hydraulic head is much more sensitive to pumping rates than any other stress. A few sentences about: flow model were utilized to derive optimal pumping rate; the effect of artificial recharge through the model, has also proved that the salt-water intrusion could be stopped by raising the water level through temporarily storing the artificially recharged water post construction of subsurface dam near the coast. (C) 2011 Elsevier Ltd. All rights reserved.

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GroMoPo Metadata for Mosian plain model
Created: Feb. 8, 2023, 3:28 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Quantifying recharge from agricultural areas is important to sustain long-term groundwater use, make intelligent groundwater allocation decisions, and develop on-farm water management strategies. The scarcity of data in many arid regions, especially in the Middle East, has necessitated the use of combined mathematical models and field observations to estimate groundwater recharge. This study was designed to assess the recharge contribution to groundwater from rainfall and irrigation return flow in the Mosian plain, west of Iran. The Inverse modeling approach and remote sensing technology (RS) were used to quantify the groundwater recharge. The recharge for steady-state conditions was estimated using the Recharge Package of MODFLOW. The land-use map for the research area was produced using remote sensing and satellite images technology. According to results, groundwater recharge from the rainfall and irrigation return flow was at the rate of 0.15 mm/day. The recharge to the groundwater from rainfall was about 0.08 mm/day (10.8 % of total rainfall). The average of groundwater recharge contribution in the study area was about 0.39 mm/day that include 15.2 % of the total water used in the irrigated fields. We can conclude that irrigation water is the most important resource of groundwater recharge in this area, consequently, it should be integrated into relevant hydrological models as the main source of groundwater recharge.

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GroMoPo Metadata for Korba aquifer model
Created: Feb. 8, 2023, 3:30 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

This study was carried out to examine the impact of an artificial recharge site on groundwater level and salinity using treated domestic wastewater for the Korba aquifer (north eastern Tunisia). The site is located in a semi-arid region affected by seawater intrusion, inducing an increase in groundwater salinity. Investigation of the subsurface enabled the identification of suitable areas for aquifer recharge mainly composed of sand formations. Groundwater flow and solute transport models (MODFLOW and MT3DMS) were then setup and calibrated for steady and transient states from 1971 to 2005 and used to assess the impact of the artificial recharge site. Results showed that artificial recharge, with a rate of 1500 m(3)/day and a salinity of 3.3 g/L, could produce a recovery in groundwater level by up to 2.7 m and a reduction in groundwater salinity by as much as 5.7 g/L over an extended simulation period. Groundwater monitoring for 2007-2014, used for model validation, allowed one to confirm that the effective recharge, reaching the water table, is less than the planned values.

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GroMoPo Metadata for Sfax region MODFLOW model
Created: Feb. 8, 2023, 3:31 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The water resources are exhausted by the increasing demand related to the population growth. They are also affected by climate circumstances, especially in arid and semi-arid regions. These areas are already undergoing noticeable shortages and low annual precipitation rate. This paper presents a numerical model of the Sfax shallow aquifer system that was developed by coupling the geographical information system tool ArcGIS 9.3 and ground water modeling system GMS6.5's interface, ground water flow modeling MODFLOW 2000. Being in coastal city and having an arid climate with high consumption rates, this aquifer is undergoing a hydraulic stress situation. Therefore, the groundwater piezometric variations were calibrated for the period 2003-2013 and simulated based on two scenarios; first the constant and growing consumption and second the rainfall forecast as a result of climate change scenario released by the Tunisian Ministry of Agriculture and Water Resources and the German International Cooperation Agency "GIZ" using HadCM3 as a general circulation model. The piezometric simulations globally forecast a decrease that is about 0.5 m in 2020 and 1 m in 2050 locally the decrease is more pronounced in "Chaffar" and "Djbeniana" regions and that is more evident for the increasing consumption scenario. The two scenarios announce a quantitative degradation of the groundwater by the year 2050 with an alarming marine intrusion in "Djbeniana" region. (C) 2018 Elsevier Ltd. All rights reserved.

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GroMoPo Metadata for Mahanadi Delta MODFLOW model
Created: Feb. 8, 2023, 3:33 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Despite being a biodiversity hotspot, the Mahanadi delta is facing groundwater salinization as one of the main environmental threats in the recent past. Hence, this study attempts to understand the dynamics of groundwater and its sustainable management options through numerical simulation in the Jagatsinghpur deltaic region. The result shows that groundwater in the study area is extensively abstracted for agricultural activities, which also causes the depletion of groundwater levels. The hydraulic head value varies from 0.7 to 15 m above mean sea level (MSL) with an average head of 6 m in this low-lying coastal region. The horizontal hydraulic conductivity and the specific yield values in the area are found to vary from 40 to 45 m/day and 0.05 to 0.07, respectively. The study area has been calibrated for two years (2004-2005) by using these parameters, followed by the validation of four years (2006-2009). The calibrated numerical model is used to evaluate the net recharge and groundwater balance in this study area. The interaction between the river and coastal unconfined aquifer system responds differently in different seasons. The net groundwater recharge to the coastal aquifer has been estimated and varies from 247.89 to 262.63 million cubic meters (MCM) in the year 2006-2007. The model further indicates a net outflow of 8.92-9.64 MCM of groundwater into the Bay of Bengal. Further, the outflow to the sea is preventing the seawater ingress into the shallow coastal aquifer system.

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GroMoPo Metadata for Mujib aquifer MODFLOW model
Created: Feb. 8, 2023, 3:34 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Mujib watershed is an important groundwater basin which is considered a major source for drinking and irrigation water in Jordan. Increased dependence on groundwater needs improved aquifer management with respect to understanding deeply recharge and discharge issues, planning rates withdrawal, and facing water quality problems arising from industrial and agricultural contamination. The efficient management of this source depends on reliable estimates of the recharge to groundwater and is needed in order to protect Mujib basin from depletion. Artificial groundwater recharge was investigated in this study as one of the important options to face water scarcity and to improve groundwater storage in the aquifer. A groundwater model based on the MODFLOW program, calibrated under both steady- and unsteady-state conditions, was used to investigate different groundwater management scenarios that aim at protecting the Mujib basin. The scenarios include variations of abstraction levels combined with different artificial groundwater recharge quantities. The possibilities of artificial groundwater recharge from existing and proposed dams as well as reclaimed municipal wastewater were investigated. Artificial recharge options considered in this study are mainly through injecting water directly to the aquifer and through infiltration from reservoir. Three scenarios were performed to predict the aquifer system response under different artificial recharge options (low, moderate, and high) which then compared with no action (recharge) scenario. The best scenario that provides a good recovery for the groundwater table and that can be feasible is founded to be by reducing current abstraction rates by 20% and implementing the moderate artificial recharge rates of 26 million(M)m(3)/year. The model constructed in this study helps decision makers and planners in selecting optimum management schemes suitable for such arid and semi-arid regions.

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GroMoPo Metadata for Isfahan-Borkhar aquifer MODFLOW model
Created: Feb. 8, 2023, 3:36 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Recently, many studies have investigated the effect of climate change on groundwater resources in semiarid and arid areas and have shown adverse effects on groundwater recharge and water level. However, only a few studies have shown suitable strategies for reducing these adverse effects. In this study, climate conditions were predicted for the future period of 2020-2044, under the emission scenarios of RCP2.6, RCP4.5, and RCP8.5, for Isfahan-Borkhar aquifer, Isfahan, Iran, using MODFLOW-2000 (MODFLOW is United States Geological Survey product). Results showed that the average groundwater level of the aquifer would decrease to 13, 15, and 16 m in 2012 to 2044 approximately under RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively. Then, three groundwater sustainability management scenarios were defined that included 10%, 30%, and 50% reduction in groundwater extraction. These strategies simulated the reduced negative effects of climate change on the aquifer. The results showed that decreases in water withdrawal rates of 10%, 30%, and 50% under RCP8.5 scenario (critical scenario) could decrease the mean groundwater level by 14, 11, and 7 m, respectively. The main result of the study showed that 50% reduction in groundwater withdrawal may increase the groundwater levels significantly in order to restore the aquifer sustainability in the study area. In this study, with assuming that the current harvest of wells in the future period is constant, so the results of studies showed that for the aquifer's sustainability management, the water abstraction from the aquifer should reduce up to 50% of the existing wells. Changing the irrigation method from surface to subdroplet irrigation plays an important role in reducing the withdrawal from the aquifer. The results of a study in Iran have shown that the change in the irrigation method from surface to subdroplet irrigation causes a 40% reduction in water use for agriculture.

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GroMoPo Metadata for Indianapolis Analytic Element model
Created: Feb. 8, 2023, 3:37 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Overlapping and adjacent ground water investigations are common in areas where aquifers are threatened by industrial development. In the Indianapolis area in Marion County, Indiana, a patchwork of ground water flow models have been used during the past 20 years to evaluate ground water resources and to determine the effects of local contamination. In every case these ground water models were constructed from scratch. Site specific finite difference grids or finite element meshes inhibit the direct reuse of input data when the area of interest shifts. Because the aquifer is not discretized into a grid or mesh with analytic element models, there are unique opportunities for direct reuse of model input data. In two applications of this principle we illustrate how the newly emerging analytic element method allows a fairly straightforward reuse of model input data from previous models in the same general area. In analytic element models of Central Indiana, streams and their tributaries are represented in different resolutions. Input data items of several modeling studies are stored and cataloged on disk in such a manner that they can be selectively retrieved by a data management program PREPRO. In this manner, a new ground water model can be set up quickly with input data which have been previously defined and tested during model calibration.

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GroMoPo Metadata for Dahaban Region model
Created: Feb. 8, 2023, 3:38 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Shallow renewable groundwater sources have been used to satisfy the domestic needs and the irrigation in many parts of Saudi Arabia. Increased demand for water resulting from accelerated development activities has placed excess stress on the renewable sources especially in coastal aquifers of the western region of Saudi Arabia. It is expected that the current and future development activities will increase the rate of groundwater mining of the coastal aquifer near the major city Jeddah and surrounding communities unless management measures are implemented. The current groundwater development of Dahaban coastal aquifer located at alluvial fan at the confluence of three major Wadis is depleting the shallow renewable groundwater sources and causes deterioration of its quality. Numerical models are known tools to evaluate groundwater management scenarios under a variety of development options under different hydrogeological regimes. In this study, two models are applied-the MODFLOW for evaluating the hydrodynamic behaviors of the aquifer and MT3D salinity distribution to the costal aquifer near Dahaban town. The models' simulation evaluates two development scenarios-the impact of excessive abstraction and the water salinity variation keeping abstraction at its current or increases in levels with or without groundwater recharge taking place. The simulation evaluated two scenarios covering a 25-year period-keeping the current abstraction at its current and the other scenario is increasing the well abstraction by 50% for dry condition (no recharge) and wet condition (with recharge). The analysis reveals that, under the first scenario, the continuation of the current pumping rates will result in depletion of the aquifer resulting in drying of many wells and quality deterioration at the level of 2,500 ppm. The results are associated with the corresponding salinity distribution in the region. Simulation of salinity in the region is a density-independent problem as salt concentration does not exceed 2,000 ppm, which is little value compared with sea salinity that amounts to 40,000 ppm. It is not recommended to increase the pumping rate than the current values. However, for the purpose of increasing water resources in the region, it is recommended to install new wells in virgin zones west of Dahaban main road. Maps of high/low potential groundwater and maps of salinity zones (more or less than 1,000 ppm) are provided and could be used to identify zones of high groundwater potential for the four studied scenarios. The implemented numerical simulation of Dahaban aquifer was undertaken to assess the water resources potential in order to reduce the depletion of sources in the future.

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GroMoPo Metadata for Rural Buenos Aires Province conceptual model
Created: Feb. 8, 2023, 3:40 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

In Argentina, the complementary irrigation has increased in most agricultural regions, where it is necessary to minimize possible negative impacts on the quantity and quality of groundwater. Numerical modeling techniques are used to obtain projections of the aquifer dynamics, for which a conceptual model is needed that provides the input data in the numerical simulations. A hydrogeological conceptual model for a rural area of Buenos Aires Province (Argentina), where complementary irrigation has caused significant depletion of groundwater levels during the irrigation season, has been developed. It was based on available geophysical and hydrogeological information and measurements of piezometric levels and hydraulic parameters of the aquifer together with the geochemical analysis of groundwater. This model was imported to a numerical model and the hydrogeological parameters were adjusted by the calibration with static piezometric levels measured in the wells. The conceptual model was validated satisfactorily using a fitting criterion to reach a value of root mean square error less than 5%. Different simulations of the probable drawdowns of the levels due to pumping were performed in the study area. The main hydrogeological unit is semi-confined, mostly comprising of a multilayer unit with good quality of water. Its minimum and maximum thickness was 60 and 240 m, respectively. The groundwater flows northwards from the hilly area to the plains. The recharge was 4.6 mm.year(-1), representing 5% of annual precipitation. Dynamic simulations show that the aquifer gets dried, which questions its sustainability. The alternating condition of the source or drain of the streams depends on the irrigation period or the dry season, respectively. Great drawdowns of piezometric levels in some areas might be the cause of changes in water classification. These results lead to the need of planning the use of groundwater as a complement to agricultural activity, considering sustainable employment of the resource.

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GroMoPo Metadata for South Platte SWAT-MODFLOW model
Created: Feb. 8, 2023, 3:41 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Climate change can have an adverse effect on agricultural productivity and water availability in semi-arid regions, as changes in surface water availability lead to groundwater depletion and resultant losses in crop yield. These inter-relationships necessitate an integrated management approach for surface water, groundwater, and crop yield as a holistic system. This study quantifies the future availability of surface water and groundwater and associated crop production in a large semi-arid agro-urban river basin in which agricultural irrigation is a leader consumer of water. The region of study is the South Platte River Basin (72,000 km(2)), Colorado, USA. The coupled SWAT-MODFLOW modeling code is used as the hydrologic simulator and forced with five different CMIP5 climate models downscaled by Multivariate Adaptive Constructed Analogs (MACA), each for two climate scenarios, RCP4.5, and RCP8.5, for 1980-2100. The hydrologic model accounts for surface runoff, soil lateral flow, groundwater flow, ground-water-surface water interactions, irrigation from surface water and groundwater, and crop yield on a per-field basis. In all climate models and emission scenarios, an increase of 3 to 5 degrees C in annual average temperature is projected. Whereas, variation in the projected precipitation depends on topography and distances from mountains. Based on the results of this study, the worst-case climate model in the basin is IPSL-CM5A-MR-8.5. Under this climate scenario, for a 1 degrees C increase in temperature and the 1.3% reduction in annual precipitation, the basin will experience an 8.5% decrease in stream discharge, 2-5% decline in groundwater storage, and 11% reduction in crop yield. These results indicate the significant effect of climate change on water and food resources of a large river basin, pointing to the need for immediate implementation of conservation practices. (C) 2021 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Yonglian Irrigation Area salinization model
Created: Feb. 8, 2023, 3:43 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Irrigation plays an important role in agricultural production, especially in arid and semi-arid regions. However, the conflict between water supply and demand will become more serious with increasing population. This study was to evaluate the effects of limited irrigation on regional-scale water movement and salt accumulation processes in agricultural areas. Due to frequent vertical interactions between the saturated groundwater zone and the unsaturated soil water zone and significant lateral groundwater movement between different horizontal areas in arid and semi-arid agricultural areas with shallow groundwater level, a quasi-three-dimensional (quasi-3D) model was adopted, which coupled one-dimensional (1D) soil water and salt movement and 3D groundwater and salt movement. The Yonglian irrigation area was used as the typical study site. Nine limited irrigation scenarios based on different allocations of irrigation water and hydrological years were set and analyzed. The main results were as follows: (1) The net groundwater recharge is negative under most of limited irrigation conditions, causing the decline of groundwater level ranging from 0.028 m to 0.199 m within one year. (2) With the decrease of irrigation and precipitation in farmland during the crop growth period, the groundwater recharge, groundwater recharge concentration, leaching efficiency coefficient will decrease linearly, while soil salt storage index will increase linearly. (3) Salts may accumulate in the root zone for dry years or normal years with autumn irrigation water less than 100 mm per unit area. (4) Lateral groundwater fluxes and salts contained in lateral groundwater fluxes will reduce approximately 30% and 40% under limited irrigation conditions. (5) The root zone will suffer from a very severe threat of soil salinization in farmlands in the future when considering the average annual increase rate of soil salt in the root zone is 3.6% under limited irrigation conditions, and necessarily intervenes are needed. The results could support decision-making for water-saving and soil salinity prevention in arid agricultural districts.

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GroMoPo Metadata for Nishapur Plain model
Created: Feb. 8, 2023, 3:44 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

In Iran, due to arid and semi-arid climate, groundwater resources play an essential role in food production, as well as domestic and industrial water supply. In recent years, increasing population, scarcity of surface water resources, and effects of worldwide and regional climate change have resulted in over-exploitation and unsustainability of these resources in the country. The present study aims to estimate groundwater sustainable yield, examine effects of spatial and temporal scale, and propose a plan for groundwater sustainable use in Nishapur Plain, in the north-east of Iran. In investigating the effects of spatial scale, the area of the plain is divided into several zones, with estimation of groundwater recharge and discharge for each zone and the temporal scale refers to the different time-scales used to estimate the average value of groundwater recharge and discharge. The results of the transient groundwater model of Nishapur Plain, revealed that average annual groundwater storage depletion is about 311 MGM(1) during the 8-year period of 2005-2013 with the minimum, average, and maximum water table decline of 0.6 m, 7.7 m and 11 m, respectively. The study results suggest that sustainable yield is closely correlated to the spatial and temporal scales, and refinement of spatial and temporal scales increases sustainable yield from 39 % to 59 % of the current pumping volume equal to about 100 MCM of water (or 8000 ha of irrigated land). Furthermore, when the groundwater withdrawals are limited to sustainable yield, increasing irrigation efficiency from 38 % (current efficiency) to about 60 %, can potentially result in maintaining irrigated areas and minimize adverse social and economic impacts of limiting groundwater usage. This is an achievable rate, based on data from the Iranian government organizations. The results of this study can be extended to other semi-arid agricultural areas, which primarily depend on groundwater.

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GroMoPo Metadata for Reclaimed land model
Created: Feb. 8, 2023, 3:46 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

In this study, the applicability of the composite model for assessing seawater intrusion and soil salinization in coastal aquifers due to climate change was investigated. In this approach, flow in the saturated zone of a coastal aquifer is simulated using a three-dimensional saturated-unsaturated transport model and flow in the unsaturated zone between the surface and groundwater level is simulated using a one-dimensional model in the vertical direction. Long-term sea-level predictions obtained using the representative concentration pathway (RCP) 4.5 and 8.5 scenarios were applied for computing the sea-level rise for 91 country-managed reclaimed areas in the Republic of Korea. Composite results were obtained and analyzed for seawater intrusion and soil salinization due to sea-level rise. In the results of groundwater and soil salinity in all 91 reclaimed land, the increasing rate of groundwater and soil salinity in the RCP 4.5 scenario was 13.5% and 10.4%, respectively. In the RCP 8.5 scenario, the increasing rate of groundwater and soil salinity was 14.1% and 11.1%, respectively. The groundwater level increased to 0.41 m in the RCP 4.5 scenario and 0.51 m in the RCP 8.5 scenario. The results for two representative reclaimed land areas in the Heungwang and Deokchon districts were examined in detail. The composite analysis revealed that widespread damage could be caused by sea-level rise in the reclaimed land and that seawater intrusion in many regions will accelerate groundwater salinization over time. Moreover, the reclaimed land areas were characterized in terms of watershed size, presence of ponds, water levels of the ponds, and pond locations. In reclaimed land located in small watersheds, the groundwater recharge area was smaller than in land located in larger watershed areas. Consequently, the seawater in small watersheds penetrated further inland. Ponds with water levels higher than the sea level effectively prevented seawater intrusion into groundwater. If the water level of a pond is similar to or lower than the sea level, it indicates that seawater has already penetrated a large part of the aquifer. The composite model developed in this study seems to be one of the simulation methods that can be applied when simulating saturated and unsaturated zone to a large number of sites. Also, the study results could be used to establish and implement a long-term comprehensive plan for water resources at the national level, considering seawater intrusion due to climate change and providing a basis for establishing countermeasures against future seawater intrusion.

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GroMoPo Metadata for Berlin Waterworks regional model
Created: Feb. 8, 2023, 3:49 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Using available observed and digital data from the hydrogeological systems within the Berlin region, two regional numerical groundwater flow models were developed using a common methodology. These models encompass for the first time an entire area of about 1,300 km(2) of the groundwater flow system within the common sub-surface catchment area of the Berlin water works. The hydrogeological model and the model aquifers were developed using a unique approach from the available hydrogeological maps and sections of the Geological surveys from Berlin and Brandenburg. The numerical models were calibrated using equipotentials of the pumped aquifer for representative conditions of groundwater extraction as well as using hydraulic information. The models were applied to predict the groundwater yield of eleven water works for the Berlin government water agency.

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GroMoPo Metadata for Nebraska Sand Hills MODFLOW model
Created: Feb. 8, 2023, 3:50 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The Nebraska Sand Hills have a unique hydrologic system with very little runoff and thick aquifers that constantly supply water to rivers, lakes, and wetlands. A ground water flow model was developed to determine the interactions between ground water and streamflow and to simulate the changes in ground water systems by reduced precipitation. The numerical modeling method includes a water balance model for the vadose zone and MODFLOW for the saturated zone. The modeling results indicated that, between 1979 and 1990, 13 percent of the annual precipitation recharged to the aquifer and annual ground water loss by evapotranspiration (ET) was only about one-fourth of this recharge. Ground water discharge to rivers accounts for about 96 percent of the streamflow in the Dismal and Middle Loup rivers. When precipitation decreased by half the average amount of the 1979 to 1990 period, the average decline of water table over the study area was 0.89 m, and the streamflow was about 87 percent of the present rate. This decline of the water table results in significant reductions in ET directly from ground water and so a significant portion of the streamflow is maintained by capture of the salvaged ET.

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GroMoPo Metadata for Beijing Mihuaishun plain GISFEFLOW model
Created: Feb. 8, 2023, 3:51 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A three dimensional finite element model (FEFLOW) has been used for regional ground water flow modeling of Mihuaishun plain located in the south of Beijing, China. The numerical groundwater flow model is developed considering recharge components (precipitation infiltration, river leakage, and irrigation return flow). GIS interface is created for each source of recharge. Hydraulic conductivities and storage coefficient have been calibrated by the steady state model using the recorded data from 2007 to 2009. The model results is useful to identify the aquifer characteristics and to analyze the groundwater dynamics. The groundwater level monitoring network will be improved by analyzing groundwater levels. The future development scenarios are proposed to predict the trend changes of groundwater levels.

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GroMoPo Metadata for Maknassy basin model
Created: Feb. 8, 2023, 3:53 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

To demonstrate the capabilities of Geographic Information System (GIS) techniques and numerical modeling for groundwater resources development in arid areas, specifically for the demarcation of suitable sites for the artificial recharge of groundwater aquifers, a study was carried out in the Maknassy basin, which is located in Central Tunisia. Thematic maps were prepared using a Hydrogeological Information System. All of the thematic layers were integrated using an ARCVIEW based model, enabling a map showing artificial recharge zones to be generated. Meanwhile, a ground water model, MODFLOW-2001, was used to estimate the effect of such water recharge on the piezometric behavior of the hydrological system. Additionally, these simulations helped manage ground water resources in the study area. The GIS-based demarcation of artificial zones developed in this study was based on logical conditions and reasoning, so that the same techniques, with appropriate modifications, could be adopted elsewhere, especially in similar aquifer systems in arid areas where the occurrence of groundwater is restricted and subject to a greater complexity. The efficiency of artificial recharge may be tested using hydrogeological modeling by simulating the effect of a potential groundwater refill. (C) 2010 Elsevier Ltd. All rights reserved.

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GroMoPo Metadata for Laubau alpine basin model
Created: Feb. 8, 2023, 3:54 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

In the alpine basin of the Laubau, located south of Ruhpolding, a groundwater system connected to glacial gravels is characterized by groundwater level dynamics. Infiltration processes along streams which vary frequently in time and space, in combination with differentiated groundwater inflows from adjacent karstified and fractured hard rock, lead to frequent shifts in the groundwater level by more than 10 meters in the unconfined gravel aquifer. The hydrogeological context holds challenges for groundwater management and the design of water protection zones in this area. Accordingly, the hydrogeological-geohydraulic characteristics had to be carefully examined and quantified. The complex hydrogeological conceptual model is confirmed by a transient calibrated groundwater flow model that considers temporal and spatial variability of the infiltration rates of the streams as well as inflows from the adjacent hard rock.

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GroMoPo Metadata for South Florida intergrated model
Created: Feb. 8, 2023, 3:56 a.m.
Authors: None · Kyle Compare

ABSTRACT:

The unique characteristics of the hydrogeologic system of south Florida (flat topography, sandy soils, high water table, and highly developed canal system) cause significant interactions between ground water and surface water systems. Interaction processes involve infiltration, evapotranspiration (ET), runoff, and exchange of flow (seepage) between streams and aquifers. These interaction processes cannot be accurately simulated by either a surface water model or a ground water model alone because surface water models generally oversimplify ground water movement and ground water models generally oversimplify surface water movement. Estimates of the many components of flow between surface water and ground water (such as recharge and ET) made by the two types of models are often inconsistent. The inconsistencies are the result of differences in the calibration components and the model structures, and can affect the confidence level of the model application. In order to improve model results, a framework for developing a model which integrates a surface water model and a ground water model is presented. Dade County, Florida, is used as an example in developing the concepts of the integrated model. The conceptual model is based on the need to evaluate water supply management options involving the conjunctive use of surface water and groundwater, as well as the evaluation of the impacts of proposed wellfields. The mathematical structure of the integrated model is based on the South Florida Water Management Model (SFWMM) (MacVicar et al., 1984) and A Modular Three-Dimensional Finite-Difference Groundwater Flow Model (MODFLOW) (McDonald and Harbaugh, 1988).

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GroMoPo Metadata for South-Central Kansas geostatistical model
Created: Feb. 8, 2023, 3:57 a.m.
Authors: None · Kyle Comapre

ABSTRACT:

This paper emphasizes the supportive role of geostatistics in applying ground-water models. Field data of 1994 ground-water level, bedrock, and saltwater-freshwater interface elevations in south-central Kansas were collected and analyzed using the geostatistical approach. Ordinary kriging was adopted to estimate initial conditions for ground-water levels and topography of the Permian bedrock at the nodes of a finite difference grid used in a three-dimensional numerical model. Cokriging was used to estimate initial conditions for the saltwater-freshwater interface. An assessment of uncertainties in the estimated data is presented. The kriged and cokriged estimation variances were analyzed to evaluate the adequacy of data employed in the modeling. Although water levels and bedrock elevations are well described by spherical semivariogram models, additional data are required for better cokriging estimation of the interface data. The geostatistically analyzed data were employed in a numerical model of the Siefkes site in the project area. Results indicate that the computed chloride concentrations and ground-water drawdowns reproduced the observed data satisfactorily.

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GroMoPo Metadata for Martinsville Alternative Site (Illinois) model
Created: Feb. 8, 2023, 4:11 a.m.
Authors: None · Kyle Compare

ABSTRACT:

The regulatory requirements for characterization of the Martinsville Alternative Site (MAS) were fulfilled by applying an iterative approach to the groundwater flow modeling of the site and surrounding area The approach consisted of field data collection and development of an initial conceptual model. The numerical model was then constructed to be consistent with the data and conceptual model. Next, the calibration results were evaluated statistically, and visually by a groundwater modeling review committee, to determine if the model accurately represented groundwater flow at the site. Initial results failed acceptance criteria because the values of numerical model input parameters had to be varied beyond observed data ranges to calibrate the results, and therefore the model was inconsistent with the initial conceptual model. This led to additional field data collection in areas where the numerical model deviated most from field-determined data. The new data provided sufficient information to revise the conceptual model and calibrate the numerical model successfully. Model calibration was followed by validation. Validation of the numerical model provided additional assurance that the model correctly simulated the observed system. No additional data were found to be necessary during validation of the MAS numerical model. The iterative approach proved to be successful for calibrating and validating this groundwater flow model and should be implemented from the onset of characterization planning in other applications.

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GroMoPo Metadata for Muschelkalk Formation karst aquifer model
Created: Feb. 8, 2023, 4:12 a.m.
Authors: None · Kyle Compare

ABSTRACT:

In three-dimensional (3-D) implicit geological modeling, the bounding surfaces between geological units are automatically constructed from lithological contact data (position and orientation) and the location and orientation of potential faults. This approach was applied to conceptualize a karst aquifer in the Middle Triassic Muschelkalk Formation in southwest Germany, using digital elevation data, geological maps, borehole logs, and geological interpretation. Dip and strike measurements as well as soil-gas surveys of mantel-borne CO(2)were conducted to verify the existence of an unmapped fault. Implicit geological modeling allowed the straightforward assessment of the geological framework and rapid updates with incoming data. Simultaneous 3-D visualizations of the sedimentary units, tectonic features, hydraulic heads, and tracer tests provided insights into the karst-system hydraulics and helped guide the formulation of the conceptual hydrogeological model. The 3-D geological model was automatically translated into a numerical single-continuum steady-state groundwater model that was calibrated to match measured hydraulic heads, spring discharge rates, and flow directions observed in tracer tests. This was possible only by introducing discrete karst conduits, which were implemented as high-conductivity features in the numerical model. The numerical groundwater flow model was applied to initially assess the risk from limestone quarrying to local water supply wells with the help of particle tracking.

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GroMoPo Metadata for Silver Bell Mountains model
Created: Feb. 8, 2023, 4:14 a.m.
Authors: None · Kyle Compare

ABSTRACT:

This study examines the groundwater characteristics in the Silver Bell Mountains, Arizona, USA, using a numerical model. Groundwater modeling is developed to describe the flow pattern in the study area and subsequently explores the possible interaction with regional porphyry copper deposits. A conceptual model is developed for the study area and regional hydrogeological conditions are simulated using the finite-difference groundwater flow model, MODFLOW-2005. The model results show that groundwater flow in the Silver Bell Mountains is strongly influenced by topography and its velocity varies with depth. In addition, the numerical model supports the idea of a continuous sustained interaction between groundwater flow and porphyry copper deposits in the Silver Bell Mountains. This interaction may result in continuing leaching of trace elements from the ore deposit, an important implication for continuing supergene alteration and enrichment of the porphyry copper deposit.

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GroMoPo Metadata for Yukon Eagle Gold Mine model
Created: Feb. 8, 2023, 4:15 a.m.
Authors: None · Kyle Comapre

ABSTRACT:

An investigative study to determine the impact of a mining operation on local water resources over a 27 year period.

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GroMoPo Metadata for Heihe River Basin regional model
Created: Feb. 8, 2023, 4:16 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

Numerical groundwater modeling is an effective tool to guide water resources management and explore complex groundwater-dependent ecosystems in arid regions. In the Heihe River Basin (HRB), China's second largest inland river basin located in arid northwest China, a series of groundwater flow models have been developed for those purposes over the past 20 years. These models have elucidated the characteristics of groundwater flow systems and provided the scientific basis for a more sustainable management of groundwater resources and ecosystem services. The first part of this paper presents an overview of previous groundwater modeling studies and key lessons learned based on seven different groundwater models in the middle and lower HRB at sub-basin scales. The second part reviews the rationale for development of a regional basin-scale groundwater flow model that unifies previous sub-basin models. In addition, this paper discusses the opportunities and challenges in developing a regional groundwater flow model in an arid river basin such as the HRB.

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GroMoPo Metadata for Nebraska Sand Hills lake/wetland model
Created: Feb. 8, 2023, 4:18 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

The feasibility of a hydrogeological modeling approach to simulate several thousand shallow groundwater-fed lakes and wetlands without explicitly considering their connection with groundwater is investigated at the regional scale (similar to 40,000 km(2)) through an application in the semi-arid Nebraska Sand Hills (NSH), USA. Hydraulic heads are compared to local land-surface elevations from a digital elevation model (DEM) within a geographic information system to assess locations of lakes and wetlands. The water bodies are inferred where hydraulic heads exceed, or are above a certain depth below, the land surface. Numbers of lakes and/or wetlands are determined via image cluster analysis applied to the same 30-m grid as the DEM after interpolating both simulated and estimated heads. The regional water-table map was used for groundwater model calibration, considering MODIS-based net groundwater recharge data. Resulting values of simulated total baseflow to interior streams are within 1% of observed values. Locations, areas, and numbers of simulated lakes and wetlands are compared with Landsat 2005 survey data and with areas of lakes from a 1979-1980 Landsat survey and the National Hydrography Dataset. This simplified process-based modeling approach avoids the need for field-based morphology or water-budget data from individual lakes or wetlands, or determination of lake-groundwater exchanges, yet it reproduces observed lake-wetland characteristics at regional groundwater management scales. A better understanding of the NSH hydrogeology is attained, and the approach shows promise for use in simulations of groundwater-fed lake and wetland characteristics in other large groundwater systems.

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GroMoPo Metadata for Jeju Island WTF model
Created: Feb. 8, 2023, 4:19 a.m.
Authors: None · Daniel Kretschmer

ABSTRACT:

A generalized water table fluctuation model based on precipitation was developed using a statistical conceptualization of unsaturated infiltration fluxes. A gamma distribution function was adopted as a transfer function due to its versatility in representing recharge rates with temporally dispersed infiltration fluxes, and a Laplace transformation was used to obtain an analytical solution. To prove the general applicability of the model, convergences with previous water table fluctuation models were shown as special cases. For validation, a few hypothetical cases were developed, where the applicability of the model to a wide range of unsaturated zone conditions was confirmed. For further validation, the model was applied to water table level estimations of three monitoring wells with considerably thick unsaturated zones on Jeju Island. The results show that the developed model represented the pattern of hydrographs from the two monitoring wells fairly well. The lag times from precipitation to recharge estimated from the developed system transfer function were found to agree with those from a conventional cross-correlation analysis. The developed model has the potential to be adopted for the hydraulic characterization of both saturated and unsaturated zones by being calibrated to actual data when extraneous and exogenous causes of water table fluctuation are limited. In addition, as it provides reference estimates, the model can be adopted as a tool for surveilling groundwater resources under hydraulically stressed conditions.

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GroMoPo Metadata for Luanhe Plain GSFLOW model
Created: Feb. 8, 2023, 4:21 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Water resources in coastal areas can be profoundly influenced by both climate change and human activities. These climatic and human impacts are usually intertwined and difficult to isolate. This study developed an integrated model-based approach for detection and attribution of climatic and human impacts and applied this approach to the Luanhe Plain, a typical coastal area in northern China. An integrated surface water-groundwater model was developed for the study area using GSFLOW (coupled groundwater and surface-water flow). Model calibration and validation were performed for background years between 1975 and 2000. The variation in water resources between the 1980s and 1990s was then quantitatively attributed to climate variability, groundwater pumping and changes in upstream inflow. Climate scenarios for future years (2075-2100) were also developed by downscaling the projections in CMIP5. Potential water resource responses to climate change, as well as their uncertainty, were then investigated through integrated modeling. The study results demonstrated the feasibility and value of the integrated modeling-based analysis for water resource management in areas with complex surface water groundwater interaction. Specific findings for the Luanhe Plain included the following: (1) During the historical period, upstream inflow had the most significant impact on river outflow to the sea, followed by climate variability, whereas groundwater pumping was the least influential. (2) The increase in groundwater pumping had a dominant influence on the decline in groundwater change, followed by climate variability. (3) Synergetic and counteractive effects among different impacting factors, while identified, were not significant, which implied that the interaction among different factors was not very strong in this case. (4) It is highly probable that future climate change will accelerate groundwater depletion in the study area, implying that strict regulations for groundwater pumping are imperative for adaptation. (C) 2017 Elsevier B.V. All rights reserved.

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GroMoPo Metadata for Regueb basin model
Created: Feb. 8, 2023, 4:22 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Climate and anthropogenic changes are expected to reduce renewable groundwater resources and to increase the risks of water scarcity, particularly in arid regions. Understanding current and future risks of water scarcity is vital to make the right water management decision at the right time. This study aims to analyze the impact of both human and climate pressures on groundwater availability in an arid environment: the Regueb basin in Central Tunisia. An integrated approach was used and applied at a monthly time step over a reference period (1976-2005) and a future period (2036-2065). Groundwater resources were assessed using hydrogeological modeling. Irrigation water withdrawals were evaluated based on remote sensing and the CropWat model. Urban water use was estimated from population growth and specific monthly water consumption data. The resulting values were used to compute two indicators (water stress index, groundwater balance) to evaluate water scarcity risks at the 2050 horizon. To assess current and future climate forcing on water resources, three climate scenarios were generated based on simulations from Coupled Model Intercomparison Project Phase 5 (CMIP5) data. A business-as-usual and an adaptation scenario (optimal cropping scenario) were performed by varying the surface areas and the crops grown in the irrigated area. Results show that the average annual water use will increase by 3.8 to 16.4% under climate change only, whereas it will increase by 100% under the business-as-usual scenario. Under the optimal cropping scenario, total water demand will increase by 50%. Water stress index indicates that under the climate change only scenario, water demand should be satisfied by the 2050 horizon, while under the other two scenarios, severe water stress will occur by 2050. The developed framework in this paper aims to fit in arid and semiarid regions in order to evaluate groundwater stress and to assess the efficiency of adaptation strategies. It results in two major recommendations regarding changes in land use and the improvement of groundwater monitoring.

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GroMoPo Metadata for Mediterranean coastal aquifer models
Created: Feb. 8, 2023, 4:24 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

A comparative study on climate change and its impacts on coastal aquifers is performed for three Mediterranean areas. Common climate scenarios are developed for these areas using the ENSEMBLES projections that consider the A1b scenario. Temperature and precipitation data of three climate models are bias corrected with two different methods for a historic reference period, after which scenarios are created for 2020-2050 and 2069-2099 and used to calculate aquifer recharge for these periods based on two soil water budget methods. These multiple combinations of models and methods allow incorporating a level of uncertainty into the results. Groundwater flow models are developed for the three sites and then used to integrate future scenarios for three different parameters: (1) recharge, (2) crop water demand, and (3) sea level rise. Short-term predictions are marked by large ranges of predicted changes in recharge, only showing a consistent decrease at the Spanish site (mean 23 %), particularly due to a reduction in autumn rainfall. The latter is also expected to occur at the Portuguese site, resulting in a longer dry period. More frequent droughts are predicted at the Portuguese and Moroccan sites, but cannot be proven for the Spanish site. Toward the end of the century, results indicate a significant decrease (mean [25 %) in recharge in all areas, though most pronounced at the Portuguese site in absolute terms (mean 134 mm/year) and the Moroccan site in relative terms (mean 47 %). The models further predict a steady increase in crop water demand, causing 15-20 % additional evapotranspiration until 2100. Scenario modeling of groundwater flow shows its response to the predicted decreases in recharge and increases in pumping rates, with strongly reduced outflow into the coastal wetlands, whereas changes due to sea level rise are negligible.

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GroMoPo Metadata for Swan Coastal Plain recharge model
Created: Feb. 8, 2023, 4:25 a.m.
Authors: None · E. Leijnse

ABSTRACT:

The groundwater resource contained within the sandy aquifers of the Swan Coastal Plain, south-west Western Australia, provides approximately 60 percent of the drinking water for the metropolitan population of Perth. Rainfall decline over the past three decades coupled with increasing water demand from a growing population has resulted in falling dam storage and groundwater levels. Projected future changes in climate across south-west Western Australia consistently show a decline in annual rainfall of between 5 and 15 percent. There is expected to be a reduction of diffuse recharge across the Swan Coastal Plain. This study aims to quantify the change in groundwater recharge in response to a range of future climate and land cover patterns across south-west Western Australia. Modelling the impact on the groundwater resource of potential climate change was achieved with a dynamically linked unsaturated/saturated groundwater model. A vertical flux manager was used in the unsaturated zone to estimate groundwater recharge using a variety of simple and complex models based on climate, land cover type (e. g. native trees, plantation, cropping, urban, wetland), soil type, and taking into account the groundwater depth. In the area centred on the city of Perth, Western Australia, the patterns of recharge change and groundwater level change are not consistent spatially, or consistently downward. In areas with land-use change, recharge rates have increased. Where rainfall has declined sufficiently, recharge rates are decreasing, and where compensating factors combine, there is little change to recharge. In the southwestern part of the study area, the patterns of groundwater recharge are dictated primarily by soil, geology and land cover. In the sand-dominated areas, there is little response to future climate change, because groundwater levels are shallow and much rainfall is rejected recharge. Where the combination of native vegetation and clayey surface soils restricts possible infiltration, recharge rates are very sensitive to reductions in rainfall. In the northern part of the study area, both climate and land cover strongly influence recharge rates. Recharge under native vegetation is minimal and is relatively higher where grazing and pasture systems have been introduced after clearing of native vegetation. In some areas, the recharge values can be reduced to almost zero, even under dryland agriculture, if the future climate becomes very dry.

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GroMoPo Metadata for Punjab FEFLOW model
Created: Feb. 8, 2023, 4:27 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

In recent years, extensive competition for groundwater use among different consumers has exploited major freshwater aquifers in Pakistan. There is an urgent need for appraisal of this precious resource followed by some mitigation strategies. This modelling study was conducted in the mixed cropping zone of the Punjab, Pakistan. Both remote sensing and secondary data were utilized to achieve objectives of this study. The data related to piezometric water levels, canal gauges, well logs, meteorological and lithological information were collected from Punjab Irrigation Department (PID), Water and Power Development Authority (WAPDA). Groundwater flow models for both steady and transient conditions were set-up using FEFLOW-3D. Water balance components and recharge were estimated using empirical relations and inverse modelling approaches. Both manual and automated approaches were utilized to calibrate the models. Moreover, sensitivity analysis was performed to see the response of model output against different model input parameters. Followed by calibration and validation, the model was run for different management scenarios, including lining of canal sections, minimization of field percolation, and change of groundwater abstraction. The study results show a drop in groundwater levels for almost all scenarios. The highest negative change was observed for the 4th scenario (i.e. 25% increase in groundwater pumping over a 10-year period), with a value of 3.73 m, by ignoring very wet summer and winter seasons. For normal weather conditions, the highest negative change was observed for the 4th scenario with a value of 2.91 m followed by 2.68 m for the 3rd scenario (i.e. 50% reduction in canal seepage and field percolation l over a 10-year period). For very wet summer and winter seasons, only one positive change was observed, for the 5th scenario (i.e. 25% decrease in groundwater pumping during 10 years period), with a value of 1.17 m. The changes for all other scenarios were negative. The mitigation strategy may include less groundwater pumping, by supporting cultivation of low delta crops and adjusting cropping patterns considering canal water supplies. It is further suggested to support current modelling results by incorporating more detailed information on cropping and by exploring the effect of climate change.

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GroMoPo Metadata for Zhangye Basin MT3DMS model
Created: Feb. 8, 2023, 4:28 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

Water resources, as the primary limiting factor, constrain the economic and social development in arid inland areas. The Zhangye Basin is a representative area of inland river basins, which is located in the middle parts of the Heihe River watershed, northwestern China. Facing with the huge water shortage, people exploited groundwater at a large scale in recent years. The reducing recharge from surface water and over-exploitation of groundwater led to the decline of groundwater levels and threatened the sustainability of water resources. This study constructed a conceptual and numerical groundwater flow model and calibrated the model based on the observed wells. A solute transport model was built using MT3DMS to calculate the groundwater age distribution in the Zhangye Basin. The simulated result shows that the youngest groundwater is distributed near the most upstream areas in the model domain, which is less than 1,000 a, older groundwater is distributed in deeper parts of the aquifer and near the discharge outlets, ranging from 6,000 a to over 20,000 a. Spatial variation of groundwater ages in the middle area indicates the recharge diversity between unconfined and confined aquifer. Groundwater age can serve as an indicator to evaluate groundwater's renewal capacity and sustainability. The formation of groundwater resources in the lower stream area would spend 10,000 a or even more than 20,000 a, so exploitation of groundwater in these areas should be restrained.

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GroMoPo Metadata for Palar sub-basin MODFLOW model
Created: Feb. 8, 2023, 4:29 a.m.
Authors: None · Emilia Leijnse

ABSTRACT:

The assessment of groundwater potential zones is crucial for estimating and managing available groundwater resources. In the proposed study, quantification of groundwater availability is performed using the information collected from the hydrogeological and geophysical (electrical resistivity) investigation of the aquifer. We delineate groundwater potential zones using a weighted overlay analysis based on the conventional method with 110 electrical resistivity surveys and 40 lithological data. MODFLOW is used to calibrate and validate the flow pattern and groundwater characteristics. The study area comprises a complex geological formation. The groundwater potential map is prepared using the observed groundwater level instead of rainfall data as the study area lacks rainfall stations. The final potential map is validated with the specific capacity obtained from the pumping test. This map is divided into 13 zones and each zone is considered as boundaries for the MODFLOW simulation. The thickness of each zone is assessed using the electrical resistivity method. The calibration and validation of the groundwater model are performed for one year and 1.5 years, respectively, between November 2012 and March 2015. We consider two layers, namely topsoil and unconfined/semi-confined aquifers in the groundwater model. During the calibration and validation periods, the groundwater volume is found to be 7.12 and 7.51 Mm(3), respectively. The groundwater mass balance assessment performed in this study will be helpful in the planning and management of groundwater resources in the area.

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