Water in Minnesota 's glacial drift aquifers generally is of acceptable quality for most uses, including household supply, industrial use, and irrigation. The aquifers generally contain calcium magnesium bicarbonate-type waters, but other types are present also.
Calcium magnesium sulfate-type waters are common in the confined drift aquifers in the southwestern and northwestern parts of the State. The elevated concentrations of sulfate, which exceed limits recommended for drinking water by the EPA, results mainly from solution of sulfate bearing minerals in rocks of Cretaceous age that have been reworked in deep glacial drift.
Sodium and chloride-type waters are common in drift aquifers in northwestern Minnesota owing to the inflow of saline water from bedrock aquifers of Paleozoic age North Dakota. Cation exchange with clay minerals in the drift also is a source of sodium to these waters, particularly in the confined drift aquifers. Some of the water from these aquifers are unsuitable for irrigation because of elevated concentrations of sodium, and some are unsuitable for drinking because of elevated concentrations of chloride.
Concentrations of nitrite plus nitrate (as N) locally exceed the EPA recommended limits for drinking water in central and northwestern Minnesota. Shallow, unconfined drift aquifers are particularly susceptible to nitrate contamination from land surface. Confined drift aquifers are much less susceptible because overlying till deposits retard downward movement of contaminants to the deeper aquifers. Nitrate contamination, which may cause methemoglobinemia in infants, is one of the more serious water quality concerns in Minnesota. Iron and manganese concentrations commonly exceed EPA 's recommendations for drinking water throughout the State, but these constituents affect aesthetic properties of water rather than health.
