The Natural Quality of Ground Water in Minnesota

Ground water occurs in four hydrogeologic environments in Minnesota – fractures in crystalline rocks, Paleozoic sedimentary rocks, Cretaceous sedimentary rocks, and glacial drift. The movement of water through and the chemical and mineralogic properties of these rocks result in distinct water-quality types in different parts of the State. Chemical analyses of ground-water samples were classified by a graphical technique. This classification shows the following distribution of ground-water types in Minnesota. Calcium magnesium bicarbonate type water occurs throughout and predominates in the east three-fourths of the State. Calcium magnesium sulfate, sodium bicarbonate, and sodium chloride types occur in complex vertical and areal relationships in west Minnesota. Water having dissolved-solids content greater than 1,000 milligrams per liter is limited largely to northwest and southwest Minnesota, where types other than calcium magnesium bicarbonate are common.