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Sarah Null

Utah State University;iUTAH | Associate Professor

Subject Areas: water resources management, systems modeling, aquatic habitat

 Recent Activity

ABSTRACT:

Watershed-scale stream temperature models are often one-dimensional because they require fewer data and are more computationally efficient than two- or three-dimensional models. However, one-dimensional models assume completely mixed reaches and ignore small-scale spatial temperature variability, which may create temperature barriers or refugia for cold-water aquatic species. Fine spatial and temporal resolution stream temperature monitoring provides information to identify river features with increased thermal variability. We used distributed temperature sensing (DTS) to observe small-scale stream temperature variability, measured as a temperature range through space and time, within two 400 meter reaches in summer 2015 in Nevada’s East Walker and mainstem Walker Rivers. Thermal infrared (TIR) aerial imagery collected in summer 2012 quantified the spatial temperature variability throughout the Walker Basin. We coupled both types of high resolution measured data with simulated stream temperatures to corroborate model results and estimate the spatial distribution of thermal refugia for Lahontan cutthroat trout and other cold-water species. Temperature model estimates were within the DTS measured temperature ranges 21% and 70% of the time for the East Walker River and mainstem Walker River, respectively, and within TIR measured temperatures 17%, 5%, and 5% of the time for the East Walker, West Walker, and mainstem Walker Rivers, respectively. DTS, TIR, and modeled stream temperatures in the mainstem Walker River nearly always exceeded the 21°C optimal temperature threshold for adult trout, usually exceeded the 24 °C stress threshold, and could exceed the 28 °C lethal threshold for Lahontan cutthroat trout. Measured stream temperature ranges bracketed ambient river temperatures by -10.1 to +2.3 °C in agricultural return flows, -1.2 to +4 °C at diversions, -5.1 to +2 °C in beaver dams, -4.2 to 0 °C at seeps. To better understand the role of these river features on thermal refugia during warm time periods, the respective temperature ranges were added to simulated stream temperatures at each of the identified river features. Based on this analysis, the average distance between thermal refugia in this system was 2.8 km. While simulated stream temperatures are often too warm to support Lahontan cutthroat trout and other cold-water species, thermal refugia may exist to improve habitat connectivity and facilitate trout movement between spawning and summer habitats. Overall, high resolution DTS and TIR measurements quantify temperature ranges of refugia and augment process-based modeling.

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ABSTRACT:

One of the greatest threats to Great Salt Lake wetlands is the invasion of Phragmites australis. Recent research has highlighted effective control strategies for Phragmites, however natural recolonization of native plants needed to support wetland functions has been limited. Seeding is a feasible restoration option, however seedling mortality is often high. Understanding the mechanisms that drive early seedling outcomes by quantifying regeneration traits can improve our ability to manipulate and predict restoration actions. Additionally, managers involved in wetland restoration need to know how many seeds to sow, which sites should be prioritized for restoration, and when they should seed. I developed a simulation model to explore changes in native and invasive seed germination across initial seeding density, restoration site, and seasonal timing scenarios. Additionally, I incorporated the influence of seed mass on native species germination into my model. This approach represents a starting point for developing an important management tool that can be used to identify targeted, cost-effective wetland restoration strategies following Phragmites treatment.

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ABSTRACT:

Globally changing temperature and precipitation patterns are causing rapid changes stream temperatures, which in turn drive changes in the life histories and distributions of aquatic biota. However, large-scale stream temperature datasets have not been developed, and observational data remains limited. In order to better understand how ongoing thermal regime changes impact aquatic species, managers and researchers need better methods of quantifying stream temperatures at large spatial scales. Here, a linear regression model is used to develop a relationship between air and stream temperature, then is used to predict stream temperatures across the state of Utah in the month of August. Model validity was assessed by examining goodness of fit to observation data using R², Nash-Sutcliffe Efficiency index, and root mean square error-observations standard deviation ratio (RSR). Impact of outliers were assessed by examining mean absolute error (MAE), root mean square error (RMSE), and residuals. The approach presented here contributes to the well-described linear air/stream temperature model by providing a study of its performance at large spatial scales.

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ABSTRACT:

This report details a model that uses a nonlinear penalty function in a linear reservoir optimization model to identify a monthly reservoir release strategy that maximizes end-of-water-year storage in Island Park Reservoir, while satisfying habitat and flow requirements for fish and anglers. Using historic hydrologic data, I explore how strategies for reservoir release, storage, and irrigation reduction change across varying hydrologic regimes (wet, average, dry) and environmental flow requirements (800, 1000, 1200 cfs).

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ABSTRACT:

Data collection on water the potential for water markets to address Great Salt Lake water conservation needs.

To create cost estimates we build on the approach of Edwards et al (2017) to create conservation cost curves estimates for each of the Bear River, Weber River, and Jordan River watersheds. We designate potential conservation measures as occurring in the agricultural or urban sectors. Estimates come from other sources and are then applied to the case at hand. Overall we estimate the conservation potential and cost savings of 15 measures, shown in the table. While the list is not comprehensive, efforts were made to include the measures likely to be implemented.

Conservation measures by category.
Urban Residential: low-flow toilets
Residential: low-flow showers
Residential: high-efficiency clothes washers
Residential irrigation: rainwater harvesting
Residential irrigation: watering at night
Residential irrigation: scheduling
Residential irrigation: partial turf conversion
Institutional irrigation: watering at night
Institutional irrigation: scheduling
Commercial irrigation: watering at night
Commercial irrigation: scheduling
Secondary wastewater reuse
Agriculture Conversion to sprinkler irrigation
Improved irrigation efficiency
Canal piping

For each conservation we estimate the quantity of water that could be conserved as well as the cost of conserving that water. We create a low, baseline, and high estimate of costs for each measure. We also create a high, baseline, and low estimate of the amount of water made available by each measure. The low cost estimate is combined with the high water availability estimate to arrive at an upper bound of each water supply curve; similarly the high-cost and low water-availability estimates are combined to create a lower-bound.

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Resources
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Composite Resource 0
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Geographic Feature 0
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Multidimensional (NetCDF) 0
Script Resource 0
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Generic Generic

ABSTRACT:

This data set contains measurements for discharge in cfs and cms, stream temperature in °C , dissolved oxygen (DO) in mg/L and %/L, total dissolved solids (TDS) in µs/cm, pebble count, and geomorphic condition, at sites in the Weber River Basin and Bear River Basin. Discharge was measured using a Marsh McBurney hand-held flowmeter. DO, TDS, and stream temperature were measured using a YSI Pro 2030 water quality probe. Pebble count was conducted using a modified Wolman procedure where a random pebble is picked up every step diagonally across a stream in a zig-zag pattern until at least 100 pebbles are measured. The pebble is then measured to obtain size and recorded. Geomorphic condition was assessed visually by taking note of conditions such as stream complexity (presence or lack of pools, riffles, meandering thalweg etc.), percent shade on stream, flow and depth variability, bank stability, access to floodplain, wood recruitment, unnatural barriers and condition and quantity of riparian vegetation. Based on the these conditions, a classification of excellent, good, moderate, or poor was assigned. Atmospheric pressure, wind speed and air temperature were measured with a Kestrel handheld weather meter, cloud cover was assessed visually. A site key in addition to the date, time and location (latitude/longitude and UTM) is included. Not all sites have values for discharge and pebble count due to hazardous conditions.

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Composite Resource Composite Resource
Optimizing Barrier Removal in Utah's Weber Basin
Created: Aug. 7, 2017, 5:44 p.m.
Authors: Maggi Kraft · Sarah Null

ABSTRACT:

In-stream barriers, such as dams, culverts and diversions alter hydrologic processes and aquatic habitat. Removing uneconomical and aging in-stream barriers to improve stream habitat is increasingly used in river restoration. Previous barrier removal projects focused on score-and-rank techniques, ignoring cumulative change and spatial structure of barrier networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. In this study, a dual objective optimization model prioritized removing in-stream barriers to maximize aquatic habitat connectivity for trout, using streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using agricultural and urban economic penalty functions, and a budget constraint monetizes costs of removing small barriers like culverts and diversions. The optimization model is applied to a case study in Utah’s Weber River Basin to prioritize removing barriers most beneficial to aquatic habitat connectivity for Bonneville cutthroat trout, while maintaining human water uses. Solutions to the dual objective problem quantify and graphically show tradeoffs between connected quality-weighted habitat for Bonneville cutthroat trout and economic water uses. Removing 54 in-stream barriers reconnects about 160 km of quality-weighted habitat and costs approximately $10 M, after which point the cost effectiveness of removing barriers to connect river habitat decreases. The set of barriers prioritized for removal varied monthly depending on limiting habitat conditions for Bonneville cutthroat trout. This research helps prioritize barrier removals and future restoration project decisions within the Weber Basin. The modeling approach expands current barrier removal optimization methods by explicitly including both economic and environmental water uses and is generalizable to other basins.

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Geographic Feature (ESRI Shapefiles) Geographic Feature (ESRI Shapefiles)
Identifying street gutters used for secondary water delivery in urbanized areas of Cache Valley, UT
Created: Oct. 29, 2017, 6:06 p.m.
Authors: Sarah E. Null · Andrew Hackett · Heather Bottelberghe

ABSTRACT:

We created a shapefile of Utah's Cache Valley street water conveyance system using ArcGIS. This included gutters, canals, and discontinued canals that transport secondary water to customers. This data collection and research supports coupled human-natural systems research because it connects human and environmental water systems. The purpose of our data collection and mapping is to support future analysis of street gutters and canals as unique secondary water delivery systems. We georeferenced the network of street water conveyance in summer 2016 that delivers secondary water. We drove, cycled, and walked Logan streets and marked those with observed water conveyance through gutters and canals on a printed map that was then transferred into an ArcGIS shapefile. To accurately determine which street gutters are part of the irrigation water delivery system, we contacted Cache County irrigation companies to receive guidance and feedback.

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Composite Resource Composite Resource
Optimizing Barrier Removal in Utah's Weber Basin
Created: April 10, 2018, 6:29 p.m.
Authors: Maggi Kraft · Sarah Null

ABSTRACT:

In-stream barriers, such as dams, culverts and diversions alter hydrologic processes and aquatic habitat. Removing uneconomical and aging in-stream barriers to improve stream habitat is increasingly used in river restoration. Previous barrier removal projects focused on score-and-rank techniques, ignoring cumulative change and spatial structure of barrier networks. Likewise, most water supply models prioritize either human water uses or aquatic habitat, failing to incorporate both human and environmental water use benefits. In this study, a dual objective optimization model prioritized removing in-stream barriers to maximize aquatic habitat connectivity for trout, using streamflow, temperature, channel gradient, and geomorphic condition as indicators of aquatic habitat suitability. Water scarcity costs are minimized using agricultural and urban economic penalty functions, and a budget constraint monetizes costs of removing small barriers like culverts and diversions. The optimization model is applied to a case study in Utah’s Weber River Basin to prioritize removing barriers most beneficial to aquatic habitat connectivity for Bonneville cutthroat trout, while maintaining human water uses. Solutions to the dual objective problem quantify and graphically show tradeoffs between connected quality-weighted habitat for Bonneville cutthroat trout and economic water uses. Removing 54 in-stream barriers reconnects about 160 km of quality-weighted habitat and costs approximately $10 M, after which point the cost effectiveness of removing barriers to connect river habitat decreases. The set of barriers prioritized for removal varied monthly depending on limiting habitat conditions for Bonneville cutthroat trout. This research helps prioritize barrier removals and future restoration project decisions within the Weber Basin. The modeling approach expands current barrier removal optimization methods by explicitly including both economic and environmental water uses and is generalizable to other basins.

Show More
Generic Generic

ABSTRACT:

Representing urban water demands economically is useful to understand how anticipated changes like population growth, conservation, water development, climate change, and environmental water demands may affect water deliveries and scarcity. Utah is the second driest state in the nation, while per capita water use is near the highest in the nation, averaging 167 gallons per person per day. This implies that creative water management will be ongoing in Utah’s future. Urban economic loss functions are estimated using residential demand functions for Utah’s Wasatch Front Metropolitan Area, which includes Logan, Salt Lake City, Ogden, Layton, Provo, and Orem urban regions. Water price, volume of water applied at that price, urban population, and price elasticity data are presented. Results show seasonal residential water demand functions and seasonal urban (residential, industrial, institutional, and commercial) economic loss functions for Logan, Ogden, Salt Lake City, and Provo metropolitan areas. Limitations to this method are outlined and discussion focuses on estimating urban water demand functions and potential economic losses input into hydro-economic models and ecological-economic models to evaluate promising solutions to Utah’s persistent water problems.

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Composite Resource Composite Resource
Great Salt Lake Water Markets
Created: June 25, 2018, 5:34 p.m.
Authors: Eric Edwards · Sarah Null

ABSTRACT:

Data collection on water the potential for water markets to address Great Salt Lake water conservation needs.

To create cost estimates we build on the approach of Edwards et al (2017) to create conservation cost curves estimates for each of the Bear River, Weber River, and Jordan River watersheds. We designate potential conservation measures as occurring in the agricultural or urban sectors. Estimates come from other sources and are then applied to the case at hand. Overall we estimate the conservation potential and cost savings of 15 measures, shown in the table. While the list is not comprehensive, efforts were made to include the measures likely to be implemented.

Conservation measures by category.
Urban Residential: low-flow toilets
Residential: low-flow showers
Residential: high-efficiency clothes washers
Residential irrigation: rainwater harvesting
Residential irrigation: watering at night
Residential irrigation: scheduling
Residential irrigation: partial turf conversion
Institutional irrigation: watering at night
Institutional irrigation: scheduling
Commercial irrigation: watering at night
Commercial irrigation: scheduling
Secondary wastewater reuse
Agriculture Conversion to sprinkler irrigation
Improved irrigation efficiency
Canal piping

For each conservation we estimate the quantity of water that could be conserved as well as the cost of conserving that water. We create a low, baseline, and high estimate of costs for each measure. We also create a high, baseline, and low estimate of the amount of water made available by each measure. The low cost estimate is combined with the high water availability estimate to arrive at an upper bound of each water supply curve; similarly the high-cost and low water-availability estimates are combined to create a lower-bound.

Show More
Composite Resource Composite Resource

ABSTRACT:

This report details a model that uses a nonlinear penalty function in a linear reservoir optimization model to identify a monthly reservoir release strategy that maximizes end-of-water-year storage in Island Park Reservoir, while satisfying habitat and flow requirements for fish and anglers. Using historic hydrologic data, I explore how strategies for reservoir release, storage, and irrigation reduction change across varying hydrologic regimes (wet, average, dry) and environmental flow requirements (800, 1000, 1200 cfs).

Show More
Composite Resource Composite Resource
A Linear Approach to Modeling Stream Temperature in Utah
Created: Feb. 21, 2019, 8:24 p.m.
Authors: Greg Goodrum

ABSTRACT:

Globally changing temperature and precipitation patterns are causing rapid changes stream temperatures, which in turn drive changes in the life histories and distributions of aquatic biota. However, large-scale stream temperature datasets have not been developed, and observational data remains limited. In order to better understand how ongoing thermal regime changes impact aquatic species, managers and researchers need better methods of quantifying stream temperatures at large spatial scales. Here, a linear regression model is used to develop a relationship between air and stream temperature, then is used to predict stream temperatures across the state of Utah in the month of August. Model validity was assessed by examining goodness of fit to observation data using R², Nash-Sutcliffe Efficiency index, and root mean square error-observations standard deviation ratio (RSR). Impact of outliers were assessed by examining mean absolute error (MAE), root mean square error (RMSE), and residuals. The approach presented here contributes to the well-described linear air/stream temperature model by providing a study of its performance at large spatial scales.

Show More
Composite Resource Composite Resource

ABSTRACT:

One of the greatest threats to Great Salt Lake wetlands is the invasion of Phragmites australis. Recent research has highlighted effective control strategies for Phragmites, however natural recolonization of native plants needed to support wetland functions has been limited. Seeding is a feasible restoration option, however seedling mortality is often high. Understanding the mechanisms that drive early seedling outcomes by quantifying regeneration traits can improve our ability to manipulate and predict restoration actions. Additionally, managers involved in wetland restoration need to know how many seeds to sow, which sites should be prioritized for restoration, and when they should seed. I developed a simulation model to explore changes in native and invasive seed germination across initial seeding density, restoration site, and seasonal timing scenarios. Additionally, I incorporated the influence of seed mass on native species germination into my model. This approach represents a starting point for developing an important management tool that can be used to identify targeted, cost-effective wetland restoration strategies following Phragmites treatment.

Show More
Composite Resource Composite Resource

ABSTRACT:

Watershed-scale stream temperature models are often one-dimensional because they require fewer data and are more computationally efficient than two- or three-dimensional models. However, one-dimensional models assume completely mixed reaches and ignore small-scale spatial temperature variability, which may create temperature barriers or refugia for cold-water aquatic species. Fine spatial and temporal resolution stream temperature monitoring provides information to identify river features with increased thermal variability. We used distributed temperature sensing (DTS) to observe small-scale stream temperature variability, measured as a temperature range through space and time, within two 400 meter reaches in summer 2015 in Nevada’s East Walker and mainstem Walker Rivers. Thermal infrared (TIR) aerial imagery collected in summer 2012 quantified the spatial temperature variability throughout the Walker Basin. We coupled both types of high resolution measured data with simulated stream temperatures to corroborate model results and estimate the spatial distribution of thermal refugia for Lahontan cutthroat trout and other cold-water species. Temperature model estimates were within the DTS measured temperature ranges 21% and 70% of the time for the East Walker River and mainstem Walker River, respectively, and within TIR measured temperatures 17%, 5%, and 5% of the time for the East Walker, West Walker, and mainstem Walker Rivers, respectively. DTS, TIR, and modeled stream temperatures in the mainstem Walker River nearly always exceeded the 21°C optimal temperature threshold for adult trout, usually exceeded the 24 °C stress threshold, and could exceed the 28 °C lethal threshold for Lahontan cutthroat trout. Measured stream temperature ranges bracketed ambient river temperatures by -10.1 to +2.3 °C in agricultural return flows, -1.2 to +4 °C at diversions, -5.1 to +2 °C in beaver dams, -4.2 to 0 °C at seeps. To better understand the role of these river features on thermal refugia during warm time periods, the respective temperature ranges were added to simulated stream temperatures at each of the identified river features. Based on this analysis, the average distance between thermal refugia in this system was 2.8 km. While simulated stream temperatures are often too warm to support Lahontan cutthroat trout and other cold-water species, thermal refugia may exist to improve habitat connectivity and facilitate trout movement between spawning and summer habitats. Overall, high resolution DTS and TIR measurements quantify temperature ranges of refugia and augment process-based modeling.

Show More