Twenty-eight public water supply systems, or less than half a percent of Minnesota's 8,121 public water supply systems, had average nitrate-nitrogen concentrations above the drinking water standard in 1999-2000. Public water supply systems include both community and non-community systems. Community systems supply drinking water for more than 15 connections or 25 residents year-round. Non-community water systems, such as for schools, factories, hospitals, restaurants, and the like serve at least 15 connections used by people other than year-round residents for 60 days a year or 25 or more people for at least 60 days a year.

Nearly one-fourth of Minnesota's population relies on private wells as a primary source of drinking water. Local water quality databases, developed by counties such as Nicollet, Brown, and Cottonwood in the southwestern part of the state, indicate that the statewide database for public water supply wells does not accurately reflect nitrate-nitrogen concentrations for private water wells. This is because wells installed by the homeowner (such as sand points), those installed before the state well code went into effect in 1974, and hand-dug wells with large diameters are not included in statewide databases. According to data from these counties, about 5 percent of the private wells in Nicollet County, 12 percent of the private wells in Brown County, and 27 percent of the private wells in Cottonwood County have average nitrate-nitrogen concentrations above the drinking water standard of 10 parts per million. However, if wells of questionable construction (i.e., wells less than 50 feet in depth and with diameters 10 inches or greater) are excluded, the percentage of unacceptable nitrate-nitrogen concentrations drops to 3 percent for Nicollet and Brown counties and to 11 percent for Cottonwood County.

Nitrate contamination is more frequent in wells that are poorly constructed or sited. In addition, some areas are more susceptible to nitrate contamination because geologic conditions, such as sandy soil, allow nitrate to seep into the ground more easily or the chemical makeup of the groundwater does not break down nitrate.

• Growth in gross state product
• Freeway congestion
• Energy use per person
• Renewable energy sources
• Vehicle miles
• Air pollutants
• Water use
• Urban air pollution
• Erosion of cropland

• Amount of groundwater and surface water used, by type of use (Minnesota Department of Natural Resources, Division of Waters, water appropriation permits, www.dnr.state.mn.us/waters).
• Levels of atrazine, a common agricultural pesticide, in groundwater in southwest Minnesota and the central sand plain (Minnesota Department of Agriculture, www.mda.state.mn.us).
• Water quality in three watershed basins: Minnesota River, Lake Superior, Red River of the North (Minnesota Pollution Control Agency, www.pca.state.mn.us).