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Potential hydrologic effects of ground-water withdrawals from the Dakota Aquifer, southwestern Kansas

Open-File Report 85-567

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Abstract

A study was conducted to evaluate the effects of potential development of the Dakota aquifer on the layered aquifer system above Permian rocks in a 5,000 sq mi area of southwestern Kansas. Transmissivity of the Dakota aquifer, determined from analyses of pumping tests, ranges from 100 to 7,100 sq ft/day. Water in the Dakota aquifer is a calcium bicarbonate type water, similar to water in the High Plains aquifer, in the subcrop area. However, in areas distant from the subcrop, water in the Dakota aquifer is a sodium bicarbonate type water with dissolved solids concentrations in excess of 500 mg/L. Gradual declines in the potentiometric surface of the Dakota aquifer have occurred since the onset of pumpage in the 1960's; however, water levels in some wells have risen during the late 1970's. A digital computer model of 3-D groundwater flow was developed to simulate hydrologic conditions of a five-layer hydrologic system for 1975-82 conditions. The major components of the simulated 1975-82 water budget were well discharge from the High Plains aquifer and loss of ground water from storage in the High Plains aquifer. Although downward leakage from the High Plains aquifer in the study area represented only 18,000 acre-ft of the 1,365 ,000 acre-ft discharged from the High Plains aquifer during 1982 , it was a major source of inflow to the Dakota aquifer. Changes in storage in the Dakota aquifer in the study area during 1982 were about 5,000 acre-ft. A base-line projection was made using 1982 simulated hydraulic heads from the calibrated model and 1982 rates of pumpage from both the High Plains and the Dakota aquifers for comparison with eight additional projection simulations in which maximum pumpage from the Dakota aquifer at the end of the projections ranged from about 78,000 to 294,000 acre-ft/yr. The results from the projections indicate that: (1) pumpage from the Dakota aquifer will have a limited effect on hydraulic heads in the High Plains aquifer, (2) drawdown in the hydraulic heads in the Dakota aquifer will result in conversion of much of the Dakota aquifer to unconfined conditions, (3) change in storage will become the major water-budget component for the Dakota aquifer, (4) continuation of 1982 rates of withdrawal from the High Plains aquifer will result in dewatering of a substantial part of the aquifer in the study area. (Lantz-PTT)

Additional Publication Details

Publication type:
Report
Publication Subtype:
USGS Numbered Series
Title:
Potential hydrologic effects of ground-water withdrawals from the Dakota Aquifer, southwestern Kansas
Series title:
Open-File Report
Series number:
85-567
Edition:
-
Year Published:
1985
Language:
ENGLISH
Publisher:
U.S. Geological Survey,
Description:
x, 72 p. :ill., maps ;28 cm.