Source Water Glossary

Aquifer—A natural underground layer, often of sand or gravel, that contains water.

Assessment—An analysis of the susceptibility of drinking water sources to contamination, communicated effectively to the public.

Groundwater—The water that systems pump and treat from aquifers.

Potential Contaminant Source—Specific point or nonpoint sources from which contamination of drinking water may originate; activities that may result in drinking water contamination.

Public Water System (PWS)—Any water system that provides water to at least 25 people for at least 60 days annually. There are more than 170,000 PWSs providing water from wells, rivers and other sources to about 250 million Americans. The others drink water from private wells. There are differing standards for PWSs of different sizes and types.

Risk Ranking—Rating or prioritizing levels of concern of potential contaminant sources based on susceptibility of public water systems.

Sole Source Aquifer—A drinking water supply in an area with few or no alternative sources to the groundwater resource, and where if contamination occurred, using an alternative source would be extremely expensive. If such an aquifer supplies a public water system on which at least 50 percent of the population depends, it may be designated as a sole source aquifer.

Source Water Protection Area—The area delineated by the state for a public water system, or including numerous PWSs, whether the source is groundwater, surface water, or both. Delineating the source water protection area is part of the state source water assessment plan approved by EPA under section 1453 of the Safe Drinking Water Act.

Surface Water—The water that systems pump and treat from sources open to the atmosphere, such as rivers, lakes, and reservoirs.

Susceptibility—The level of risk of drinking water contamination, based on the nature and severity of contaminants, and the likelihood of the contaminants getting into a drinking water source.

Underground Injection Control Program—A program to prevent injection activities from endangering underground sources of drinking water.

Wellhead Protection Area—The surface and subsurface area surrounding a well or well field, supplying a public water system, through which contaminants are reasonably likely to move toward and reach such water well or field.

Source: U.S. Environmental Protection Agency Consider the Source: A Pocket Guide to Protecting Your Drinking Water