ABSTRACT
Part of the precipitation that falls on land may infiltrate the surface, percolate downward through the soil under the force of gravity, and become what is known as groundwater. Like surface water, groundwater is an extremely important part of the hydrologic cycle. Almost half of the people in the U.S. obtain their public water supply from groundwater. Overall, the U.S. has more groundwater than surface water, including the water in the Great Lakes. Unfortunately, pumping it to the surface for use is sometimes uneconomical and, in recent years, the pollution of groundwater supplies from improper disposal has become a significant problem (Spellman, 1996).
