It provides about 40 percent of the Nation's public water supply. In addition, more than 40 million people, including most of the rural population, supply their own drinking water from domestic wells.
Ground water is also the source of much of the water used for irrigation.
It is the Nation's principal reserve of freshwater and represents much of the potential future water supply. Ground water is a major contributor to flow in many streams and rivers and has a strong influence on river and wetland habitats for plants and animals. This is the explanation for the revision. From an overall national perspective, the ground-water resource appears ample. Locally, however, the availability of ground water varies widely.