Groundwater is the water that fills the cracks and pores of rocks and sediments that lie beneath the surface of the earth — much the way water saturates a sponge. In the Twin Cities metro area, groundwater is an abundant but finite and vulnerable resource.
Groundwater is the source of drinking water for 75% of the people in the metro area. Groundwater is stored in the pore spaces of rock formations, called aquifers. The amount of water and how quickly it moves underground depends on the rock formation and pore space size.
The groundwater used in the metro area is pumped from one of four aquifers under the surface of the region: the Quaternary aquifer, the Prairie Du Chien-Jordan aquifer, the Tunnel City-Wonewoc aquifer, or the Mt. Simon-Hinckley aquifer.