The Oahe Unit, in the James River basin in eastern South Dakota, extends for about 100 miles north and south and is 20 to 80 miles wide, having the river as its east border. The Oahe irrigation project is planned to supply water to 750,000 to 1,500,000 acres of the most suitable land within the area.
The studies that have been undertaken in the Oahe area by the Ground Water Division of the U. S. Geological Survey form a part of the investigations which are being carried on by several bureaus of the Department of the Interior and other government agencies for the conservation, control and utilization of the water resources of the Missouri River Basin.
The field studies on which the present report is based were made during May 1947 through November 1948 and cover about 1,890 square miles in the southern part of the Oahe area. Data were collected on the character of the surficial geological deposits, and on the occurrence, movement, quantity, and quality of the groundwater supplies.
The report describes the several water-bearing formations and presents nine typical logs of deep artesian wells. The records of fluctuation of the water table in 168 wells in or near the Oahe area are listed. Tabulated inventory of 3,257 wells and springs includes information on the observation wells and on all other wells that were noted within the area examined.