The Crow Creek Sand Lake area is in the northeastern part of South Dakota and consists of flat to gently rolling land. It is roughly 25 miles square and is bounded on the west by the James River, on the north by the North Dakota State line, and on the south and east by arbitrary land lines. Natural drainage, which is very poor, is augmented by a now very dilapidated system of man made drains; undrained or poorly drained potholes and sloughs are common. Most of the report area is in the drainage basin of Crow Creek, a tributary of the James River. About 60 square miles along the west border of the area is drained directly by the James River; and about 36 square miles in the northeastern corner of the area is drained by the Wild Rice River, a tributary of the Red River of the North.

Granite and other related rocks of Precambrian age underlie the entire area below a depth of about 1,100 to 1,200 feet. Under part of the area these rocks are overlain by the Sioux quartzite, also of Precambrian age. Next above is the Dakota sandstone of Cretaceous age, which is about 250 feet thick and is the aquifer tapped by more than 600 deep wells in the area. The Dakota sandstone in turn is overlain by younger formations of Cretaceous age, which include the Graneros shale, Greenhorn limestone, Carlile shale, Niobrara formation, and Pierre shale. These younger formations have an aggregate thickness of about 700 to 950 feet and generally do not yield water. Mantling, the consolidated stratified rocks are unconsolidated deposits of Quaternary age that are absent locally but in places are as much as 200 feet thick. These deposits consist principally of glacial outwash, glacial till, and lake sediments and are the source of water for all shallow wells in the area.

Precipitation is the principal source of recharge to the ground-water reservoir tapped by the shallow wells. The water table ranges in depth from less than 1 foot to a little more than 30 feet below the land surface; in July 1951 the depth to water was less than 5 feet in 15 percent of the area and 5 to 10 feet in an additional 25 percent of the area. Because the hydraulic gradient in most of the area is less than 10 feet per mile and because much of the water-bearing material is only slightly permeable, lateral movement of the ground water in the unconsolidated deposits is exceedingly slow.

Transpiration by vegetation and evaporation account for most of the ground water discharged in the area; relatively little ground water is discharged by streams, wells, and springs, or as underflow out of the area. Much of the low-lying land is waterlogged. However, by improving and cleaning both the natural and artifical drains and by lowering the water table by pumping, waterlogging can be materially decreased and its recurrence prevented.