Ground Water for Irrigation in the Viking Basin, West-Central Minnesota

The Viking Basin consists of six separate but close together areas underlain by surficial glacial-outwash aquifers in Douglas, Otter Tail, and Todd Counties, west-central Minnesota. The total area is 340 mi 2 (square miles) or 880 km 2 (square kilometres). Soils developed on the outwash are generally sandy and excessively well drained. Crops grown on the outwash would benefit from supplemental irrigation. The outwash is underlain by 300 to 400 ft (feet) or 90 to 120 m (metres) of glacial drift, consisting largely of clay till but locally containing buried sand and gravel aquifers capable of yielding large quantities of water to wells. Igneous and metamorphic bedrock beneath the till is not a source of water. Well yields greater than 1,000 gallons per minute (0.06 cubic metre per second) can be obtained from the surface outwash aquifer in about one-third of the outwash area near Carlos (28 mi 2 or 73 km 2 ) and in about half of the outwash area near Parkers Prairie (190 mi 2 or 490 km 2 ). Extensive irrigation with ground water in the Carlos area would lower average water levels from 2 to 8 ft (0.6 to 2.4 m) in the developed area. Average water levels in the irrigated part of the Parkers Prairie area would decline 1 to 3 ft (0.3 to 1 m) Environmental effects would include lowering the levels of lakes and marshes and reducing streamflow out of the areas. An area south of Alexandria (83 mi 2 or 210 km 2 ) is underlain by outwash generally less than 40 ft (12 m) thick. The surface outwash aquifer here can supply enough water for irrigation in only a few places. One irrigation system now operates from a well in a buried outwash aquifer; test drilling may reveal more such aquifers. Outwash in an area near Clotho (15 mi 2 or 39 km 2 ) is locally more than 80 ft (24 m) thick. About 3 mi 2 (8 km 2 ) of this area is irrigable and can probably be supplied with water from the outwash. An area south of Urbank (14 mi 2 or 36 km 2 ) has generally less than 40 ft (12 m) of surface outwash; a few irrigation supplies may be obtainable where the outwash is thickest. In an area southeast of Rose City (13 mi 2 or 34 km 2 ), outwash is generally less than 20 ft (6 m) thick, and no irrigation from the outwash seems possible. Water from the outwash is of excellent chemical quality for irrigation. The outwash aquifer is easily contaminated from the surface, however, and a significant danger exists of nitrate contamination of drinking-water supplies.