Aquifers and soil filter effect : nitrogen in the environment
Groundwater is like a very large, saturated underground sponge made of sands and gravels. Water seeps through this sponge at varying rates, depending on the permeability of the sands or gravel. Water filters down through the soil until it reaches the aquifer. The water table indicates the top level of groundwater, or aquifer. Aquifers may be present very near the ground surface or more than 1,000 feet down.