In 1960 the U.S. Geological Survey, in cooperation with the South Dakota State Water Resources Commission and the South Dakota State Geological Survey, started a program for the hydrogeologic investigation of glacial drift in selected drainage basins in eastern South Dakota. This program was designed to delineate water-bearing deposits of glacial-outwash sand and gravel, and to determine their water-yielding characteristics, particularly with regard to irrigation and industrial use. Investigations of this type will aid in planning the use and conservation of ground water for future agricultural and industrial growth in South Dakota.

This report describes the part of the Big Sioux River drainage basin from Sioux Falls north to a U.S. Geological Survey gaging station 9M miles southeast of Brookings (see fig. 1).

The drainage area, about 675 square miles, is in the southwestern part of the Coteau des Prairies section of the Central Lowland physiographic province, as defined by Flint (1955, p. 5). It includes the Big Sioux River valley in Moody and north-central Minnehaha Counties, and the uplands that drain into the valley, from Brookings, Lake, Moody, and Minnehaha Counties, South Dakota, and Pipestone and Lincoln Counties, Minnesota.

This report is based on data from field and laboratory studies and from published and unpublished records of State and Federal agencies. The investigations included: (1) Delineating area of water-bearing glacial outwash deposits; (2) inventorying wells to locate areas of greatest ground-water potential; (3) examining samples from auger holes to define thickness, extent, and character of water-bearing deposits; (4) determining the altitudes of selected test holes and wells for use in preparing cross sections and watertable maps; (5) collecting and analyzing water samples to determine the chemical character of water; and (6) testing aquifers to determine the hydrologic properties of the water-bearing deposits.

Data consisting of logs of wells and test holes, waterlevel measurements, chemical analyses of water, stream-runoff measurements, and determinations of the hydrologic properties of aquifers are contained in a separate report by Ellis and Adolphson (1968).