Groundwater is water that is under the ground. Water from rainfall, snowmelt, lakes, streams, and wetlands seeps into the ground. The water collects in the spaces in materials like sand and gravel, similar to water in a sponge. It can also collect in fractures in hard rock. These underground "ponds" are called aquifers.
Groundwater provides drinking water through wells, as well as base flow for many streams and rivers. This base flow is especially important during dry summer months for fish.
Groundwater is important to the economy and environment of Washington State. Over 60 percent of Washington residents get their drinking water from groundwater. Groundwater is also used for irrigation, agriculture, and a number of other industries in the state.
Because groundwater is underground and out of sight, various chemicals used or dumped on the ground's surface can infiltrate into the ground, or leak from septic systems, and end up in the groundwater. Once these pollutants enter groundwater, they can be difficult to detect by taste or smell, and difficult to remove. They can then end up in drinking water and water used for irrigation. Because groundwater supplies many of our streams, especially in the late summer, pollutants in groundwater can end up in those rivers and streams.
Underground Injection Control | Other Groundwater-Related Links | Groundwater-Related Reports and News Items | Contact Information
Chapter 173-200 WAC: Water Quality Standards for Ground Waters of the State of Washington
Implementation Guidance for Groundwater Quality Standards
Ecology Publication 96-02, revised October 2005
Explains and interprets the standards, providing clear direction to promote consistent statewide implementation for all activities which have a potential to degrade groundwater quality.
This program protects groundwater quality by regulating the disposal of fluids into the subsurface.
Information on the UIC Program
Ecology's Groundwater Portal
A great source of information for all things groundwater at the Department of Ecology.
Critical Aquifer Recharge Area (CARA)
This ordinance provides local governments with a mechanism to protect the functions and values of a community’s drinking water by preventing pollution and maintaining supply.
Interagency Groundwater Committee
Representatives from state agencies, federal and local governments, tribes, and other public groups with an interest in protecting and preserving the groundwater of Washington State. The committee is inactive at this time.
Groundwater Assessment in Washington State
Environmental Assessment Program
Information on technical studies of groundwater-related issues.
Columbia Basin Groundwater Management Area (GWMA)
A voluntary, local planning effort to work on nitrate in groundwater issues, formed by locally elected leaders and citizens of Adams, Franklin and Grant Counties.
The Ground Water Story (Note: requires Micromedia FLASH software to view. See webpage for more information.)
An animated lesson about ground water. Courtesy of King County Metro.
Vancouver Helps Protect Vancouver′s Water (WQ Success Story)
The city of Vancouver created a consensus team to develop an ordinance and other resources to protect the city′s surface, storm, and groundwaters.
Homestead Assessment System (HAS) / Farmstead Assessment System (FAS) Programs for WA State
Provides voluntary and confidential water quality/environmental risk assessments for home and/or farm property. The program helps protect the watershed's water quality, including drinking water resources.
Ground Water and Drinking Water
Environmental Protection Agency (EPA)
Provides information on how EPA works with states, tribes, and others to ensure safe drinking water and protect groundwater.
Land Application Guidance Documents
Guidance on Land Treatment of Nutrients in Wastewater, with Emphasis on Nitrogen
Ecology Publication No. 04-10-081
Guidance on land treatment of nutrients in wastewater, with emphasis on nitrogen.
State Waste Discharge to Ground Permits
Relationship between Land Use and Nitrate Concentrations In Washington State Department of Ecology Monitored Watersheds: Technical Memorandum
Ecology Publication No. 15-10-037
Quality Assurance Project Plan: Washington Nitrate Prioritization Project
Ecology Publication No. 14-10-005
Ground Water Studies and Reports
Environmental Assessment Program page
Information on ground water assessment studies performed by the Department of Ecology.
Groundwater in Washington State Report
Ecology Publication No. 96-007
General summary of ground water in Washington State.
Nitrate Contamination in the Mid-Columbia Basin Report
Information on nitrate contamination in ground water in the mid-Columbia Basin area, including Adams, Benton, Franklin, Grant, Lincoln, and Whitman counties.
Nitrogen Use by Crops and the Fate of Nitrogen in the Soil and Vadose Zone
Ecology Publication No. 00-10-015
Report on a literature review on the fate of residual nitrogen (N) in the soil and vadose zone. Provides background information on nitrogen use by crops and interactions between the soil water and nitrogen balances and crop water and N use.
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