INVESTIGATION OF THE UPPER-VERMILLION-MISSOURI AQUIFER, A GLACIAL OUTWASH BODY IN SOUTHEASTERN SOUTH DAKOTA

South Dakota’s water law requires that the “quantity of water withdrawn annually from the aquifer does not exceed the estimated average annual recharge to the aquifer” (ARSD 74:02:05:07). Due to the recent drought in South Dakota, a large number of permit requests for withdrawal of water from the Upper-Vermillion-Missouri aquifer were received by the State. Due to uncertainty regarding the availability of unappropriated water in that aquifer, the South Dakota Department of Environment and Natural Resources, Geological Survey Program, performed an investigation which included 43 weeks of drilling in the region and collection of 82 water samples for chemical analysis. The aquifer is a large Wisconsin-age glacial outwash body deposited primarily in the Ancient White River channel, which downcut through significant thicknesses of bedrock. It is located in the southeastern part of the state, where many rely on it for drinking water and irrigation. New maps of the Precambrian topography, bedrock type and topography, cross sections, and aquifer boundaries were created. Results of the study will be used to justify the granting or denial of the requests for irrigation permits. This study will also be used to guide the format and extent of aquifer-specific studies to be performed in the future.