Hydrogeologic and water-quality characteristics of the Red River-Winnipeg aquifer northwestern Minnesota

The Red River-Winnipeg aquifer of Ordovician age occupies a depression in the Proterozoic crystalline bedrock of northwestern Minnesota. The Winnipeg Formation, which underlies the Red River Formation, consists of two units: A lower shaley mudstone and an upper medium-grained sandstone. The Red River Formation consists of a lower dolomitic, dark-gray limestone and upper, slightly less-dolomitic, limestone. A porous zone at the top of the upper limestone yields most of the water to wells in the Red River-Winnipeg aquifer.

Ground water generally flows eastward through the aquifer from North Dakota and discharges upward to wells and to overlying deposits. Yields of wells open to the full thickness of the aquifer range from 100 t 250 gallons per minute. The water is unsuitable for most uses because of the high mineral content. Dissolved-solids concentrations range from about 3,000 milligrams per liter in the eastern part of the aquifer to about 60,000 milligrams per liter in the northwestern corner of Minnesota.