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. Groundwater, like surface water, is an extremely important part of the hydrologic cycle. Almost half of the people in the United States obtain their public water supply from groundwater. Overall, there is more groundwater than surface water in the United States, including the water in the Great Lakes, but sometimes it is not economical to pump it to the surface for use, and in recent years the pollution of groundwater supplies from improper disposal has become a significant problem (Spellman, 1996).
