Groundwater is the water beneath the land surface that fills the spaces in rock and sediment. It is replenished by precipitation. Under natural conditions much of that recharge returns to the atmosphere by evapotranspiration from plants and trees or discharges to surface waters. Groundwater discharge to surface waters allows streams to flow beyond rain and snowmelt periods and sustains lake levels during dry spells.
Groundwater occurs everywhere in Minnesota, but the availability of groundwater for water supplies vary throughout the state. Availability for larger withdrawals may be limited in some areas. Groundwater supplies about 75 percent of Minnesota's drinking water and nearly 90 percent of the water used for agricultural irrigation.