This coverage contains information about the probability of obtaining a water supply within the Standing Rock Indian Reservation, Sioux County, North Dakota, and Corson County, South Dakota. The digital data were produced by the U.S. Geological Survey (USGS) in cooperation with the U.S. Environmental Protection Agency.

The possibility of obtaining adequate supplies of good quality water from surficial deposits generally is limited to bedrock formations overlying the Pierre Shale where their total thickness is at least 150 feet, to four buried glacial valleys in eastern Sioux County, and to alluvium along Cedar Creek and the Cannonball and Missouri Rivers. In a few places, adequate supplies of stock or domestic water may be found in alluvium along the Grand River and in a few terraces (Howells, 1982).

Identified units include: 1) Excellent--Well yields may range from 500 to 1,000 gallons per minute. Dissolved-solids concentration probably is less than 1,600 milligrams per liter; 2) Very good--May range from 200 to 500 gallons per minute. Dissolved-solids concentration probably is less than 1,600 milligrams per liter; 3) Good--Well yields range from 10 to 200 gallons per minute. Dissolved-solids concentration is probably less than 1,600 milligrams per liter; 4) Good to fair--Well yields range from 2 to 10 gallons per minute, locally may be larger; 5) Fair--Well yields may range from 2 to 10 gallons per minute. Greater chance that any water found will be of poor quality; 6) Fair to poor--Locally possible to obtain well yields of 1 to 5 gallons per minute. Water is commonly of poor quality; and 7) Very poor--Low probability of obtaining water. Any water found is likely to be of very poor quality.

Figure 6 in Howells (1982) was scanned and digitized on-screen to create this coverage. See cross reference information for more detail.