With increased use of water by industry, homes, and municipalities, our national reliance on ground water is expected to increase. Ground water is a vital link in the water cycle. Ground water feeds rivers, lakes, and streams used for drinking water. Aquifers are replenished by rainfall or other surface water percolating through the soil. In turn, ground water supplies the base flow of many streams and feeds lakes through underground springs.
Ground water can move across state boundaries.
It continually moves, sometimes recharging surface waters miles from where it started. Preventing the contamination of ground water resources is an important public concern. Pollutants in surface water or substances like pesticides and fertilizers deposited on the soil may be carried into aquifers. The land disposal of wastes into injection wells , landfills, and surface impoundments can also cause contaminants to enter ground water. Ground water is usually assumed to be of high quality and is often used with little or no treatment.