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GroMoPo Metadata for Rapid City area USGS model


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Created: Feb 06, 2023 at 9:38 p.m.
Last updated: Feb 06, 2023 at 9:39 p.m.
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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

Subject Keywords

Coverage

Spatial

Coordinate System/Geographic Projection:
WGS 84 EPSG:4326
Coordinate Units:
Decimal degrees
Place/Area Name:
United States
North Latitude
44.4874°
East Longitude
-102.7443°
South Latitude
43.8055°
West Longitude
-103.6287°

Content

Additional Metadata

Name Value
DOI 10.3133/sir20095205
Depth 430
Scale < 10 000 km²
Layers 2-5 layers
Purpose groundwater resources;scientific investigation
GroMoPo_ID 36
IsVerified True
Model Code MODFLOW
Model Link https://doi.org/10.3133/sir20095205
Model Time SS
Model Year 2009
Model Authors L.D.Putnam , A.J.Long
Model Country United States
Data Available report/paper only
Developer Email ldputnam@usgs.gov
Dominant Geology Model focuses on multiple geologic materials
Developer Country USA
Publication Title Numerical groundwater-flow model of the Minnelusa and Madison hydrogeologic units in the Rapid City area, South Dakota
Original Developer No
Additional Information Numerical groundwater-flow model of the Minnelusa and Madison hydrogeologic units, which contain the Minnelusa and Madison aquifers, in the Rapid City area in South Dakota
Integration or Coupling None of the above
Evaluation or Calibration static water levels;dynamic water levels
Geologic Data Availability

How to Cite

GroMoPo, C. Mohan (2023). GroMoPo Metadata for Rapid City area USGS model, HydroShare, http://www.hydroshare.org/resource/d31f0aea7f7647609214b32d962ea28c

This resource is shared under the Creative Commons Attribution CC BY.

http://creativecommons.org/licenses/by/4.0/
CC-BY

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