The aquifers are shallow. The high hydraulic conductivities of overlying soils make them vulnerable to contamination. The Anoka Sand Plain is characterized by high hydraulic conductivity, shallow depth to water table, flat topography, and low runoff. The underlying 1,700 square mile aquifer is one of the largest in the state. The soils are excessively drained.
Irrigation is necessary for profitable crop production.
The Oakes Irrigation Research site aquifer in North Dakota consists of medium sand to gravel. The depth to the water table is approximately 10 feet. Annual precipitation averages 18 inches. The aquifer underlies some 1,200 square miles in eastern South Dakota, and is the water supply for Sioux Falls, Brookings, and many smaller communities. Preliminary ground water samples from the Anoka Sand Plain in 1990 showed nitrate nitrogen levels at 15 to 18 ppm.