Ground water is the water that fills cracks and other openings in beds of rocks and sand. Each drop of rain that soaks into the soils moves downward to the water table, which is the water level in the ground water reservoir. Ground water does not normally occur in underground streams, lakes, or veins.
Ground water is found in soils and sands able to retain the water - much like a sponge holds water.
Of the total 341 billion gallons of fresh water the United States withdraws each day, ground water is estimated to be 76.4 billion gallons, or 22 percent. There is a relationship between ground water and surface water. In large part, the flow in a stream represents water that has flowed from the ground into the stream channel. About 90 percent of our fresh water supplies lie underground, but, less than 23 percent of the water Americans use comes from underground sources, which illustrates the under-utilization of ground water. Ground water is a significant water supply source - the amount of ground water storage dwarfs our present surface water supply.