According to the Minnesota Department of Natural Resources, Groundwater supplies approximately 75 percent of Minnesota's drinking water and nearly 90 percent of the water used for agricultural irrigation. There is one hundred times more groundwater than the quantity of surface water in all of the world's rivers and lakes.
A County Geologic Atlas (CGA) provides information about the geology and groundwater resources of a county, including the groundwater quality, quantity, and sensitivity to pollution. The Atlas is divided into two parts (A & B). Part A is produced by the Minnesota Geological Survey, which includes the geology, geologic layering, sand distribution, bedrock surface, and depth to bedrock for a specific county. The DNR produces the Part B atlas, which includes maps and reports identifying the direction of groundwater flow, aquifer properties, groundwater chemistry, and pollution sensitivity of aquifers.