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Ground Water
Environmental Protection Agency: Region2 Ground Water
There are two sources of water supply available to society - surface sources, which include rivers, lakes and reservoirs, and ground sources, which include wells and springs that tap aquifers and other underground sources. Roughly 40 percent of the Region's drinking water comes from underground sources.
Underground water and subterranean water are other terms used in referring to water in the zone of saturation, but ground water is the preferred term
Ground water is contained in what is called the zone of saturation -- typically from the water table down to bedrock -- which may be viewed as a huge natural reservoir or system of reservoirs whose capacity is the total volume of the pores or openings in the rocks that are filled with water.
Ground water that is fluid -- free to move -- is contained in aquifers, and is generally available as a source of drinking water. Some ground water is bound up -- in clay, for instance -- and cannot be tapped through wells.
Ground water supplies are replenished by surface water that percolates through soil or flows through rock crevices to reach the zone of saturation. Land areas where this occurs are called recharge zones. Hard surfaces such as roofs and parking lots that divert the normal flow of water can affect ground water recharge. A major concern in many areas is aquifer depletion, where water is removed from the ground faster than it can be replenished.
Ground water may be found in one continuous body or in several separate strata. The thickness of the zone of saturation varies from a few feet to many hundreds of feet. Factors that determine its thickness are: the local geology, the availability of pores or openings in the formations, the recharge and the movement of water within the zone from areas of recharge toward points in areas of discharge.
Addition background information is available on our Ground Water Basics Web page and on the national Office of Ground Water and Drinking Water page.
Region 2 Ground Water Protection
Ground Water Protection is made up of several different programs: Comprehensive State Ground Water Protection, Wellhead Protection, and the Sole Source Aquifer Protection Program. These programs are authorized under different statutes and regulations, whose common goal is to prevent the contamination of ground water and protect public health.
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Sole Source Aquifers and Petitioners Guidance for Sole Source Aquifer Designation of areas which are dependent upon ground water supplies. Following designation, the review process will ensure that federal agencies will not commit funds toward projects which may contaminate these ground water supplies.
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Source Water Assessment Program requires the states to perform a source water assessment for each and every public water system. The assessment required:
- The determination of the area contributing water to the well(s) or intake(s).
- The development of an inventory of potential pollution threats within the area.
- An evaluation of the water supply's susceptibility to the potential threats.
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Well Head Protection Program protects ground water-based public water supplies. (The term "wellhead" is essentially synonymous with either a well or with the column or "head" of water within a well.)
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Underground Storage Tank Program protect ground water from leaking underground storage tanks. One gallon of leaked or spilled gasoline can contaminate one million gallons of underground drinking water.