Appraisal of the water resources of the eastern part of the Tulare aquifer, Beadle, Hand, and Spink Counties, South Dakota

A system of glacial outwash aquifers lie in the central James Valley in east-central South Dakota. Within this system, the eastern part of the Tulare aquifer, which has an area of approximately 681 square miles, was simulated by means of a numerical ground-water flow model. The model estimates the yearly average recharge rate for that part of the aquifer lying west of the James River to be approximately 23,000 acre-feet per year. This rate is considerably more than the estimated 1978 yearly average irrigation pumpage rate of 9,800 acre-feet per year. It is expected that, since pumping will reduce discharge from the aquifer through evapotranspiration and flow to the James River, this part of the aquifer would be able to supply irrigation water at recent pumpage rates for an indefinite period. For that part of the aquifer lying east of the river, estimated recharge is 6,800 acre-feet per year; a rate slightly smaller than the estimated 1978 yearly average irrigation pumpage rate of 7,200 acre-feet per year. It is estimated that this part of the aquifer would be able to supply irrigation water at 7,200 acre-feet per year for approximately 50 years, at which time excessive drawdown would begin to cause reduced well yields at several locations. (USGS)