Appraisal of The Pelican River Sand-Plain Aquifer, Western Minnesota

The Pelican River sand-plain area includes approximately 200 square miles of outwash deposits in parts of Decker, Otter Tail, and Clay Counties in west-central Minnesota. Saturated thickness of the outwash is as much as 140 feet and yields of properly constructed wells locally may exceed 1,200 gallons per minute. Recharge to the outwash from snowmelt and rain ranged from 3.2 to 6.1 inches during 1979-80. Discharge from the aquifer, as base flow of the Pelican River, averaged 2.0 inches during 1979-80. Evapotranspiration is 22.4 inches per year. The chemical quality of ground water is suitable for irrigation, as measured by sodium-adsorption ratios, but locally high concentrations of calcium, magnesium, and bicarbonate may cause clogging of well screens. Mathematical models of parts of the ground-water-flow system indicate that lake levels and streamflow may decline because of pumping wells. The exact water-level decline depends on the total number of wells, pumping rates, location of pumping wells with respect to one another and to surface-water bodies, duration of pumping, and the quantity of ground-water recharge. Sensitivity analyses of the models indicates that additional data on hydraulic conductivity, evapotranspiration, and recharge may increase the reliability of model results. Buried aquifers are known to be present in the area. Aquifer-test results showed that pumping from a buried aquifer had no effect on water levels in the unconfined aquifer.