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A digital simulation of the glacial-aquifer system in the northern three-fourths of Brown County, South Dakota

Water-Resources Investigations Report 88-4198

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Abstract

A digital model was developed to simulate groundwater flow in a complex glacial-aquifer system that includes the Elm, Middle James, and Deep James aquifers in South Dakota. The average thickness of the aquifers ranges from 16 to 32 ft and the average hydraulic conductivity ranges from 240 to 300 ft/day. The maximum steady-state recharge to the aquifer system was estimated to be 7.0 in./yr, and the maximum potential steady- state evapotranspiration was estimated to be 35.4 in/yr. Maximum monthly recharge for 1985 ranged from zero in the winter to 2.5 in in May. The potential monthly evapotranspiration for 1985 ranged from zero in the winter to 7.0 in in July. The average difference between the simulated and observed water levels from steady-state conditions (pre-1983) was 0. 78 ft and the average absolute difference was 4.59 ft for aquifer layer 1 (the Elm aquifer) from 22 observation wells and 3.49 ft and 5.10 ft, respectively, for aquifer layer 2 (the Middle James aquifer) from 13 observation wells. The average difference between the simulated and observed water levels from simulated monthly potentiometric heads for 1985 in aquifer layer 1 ranged from -2.54 ft in July to 0.59 ft in May and in aquifer layer 2 ranged from -1.22 ft in April to 4.98 ft in November. Sensitivity analysis of the steady-state model indicates that it is most sensitive to changes in recharge and least sensitive to changes in hydraulic conductivity. (USGS)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
A digital simulation of the glacial-aquifer system in the northern three-fourths of Brown County, South Dakota
Series title:
Water-Resources Investigations Report
Series number:
88-4198
Edition:
-
Year Published:
1990
Language:
ENGLISH
Publisher:
U.S. Geological Survey ; Books and Open-File Reports [distributor],
Description:
v, 74 p. :ill., maps ;28 cm.