Hydrologic Cycle Diagram.  Courtesy of King County Metro.

Nitrate Contamination in the Mid-Columbia Basin

An interagency study of ground water in the mid-Columbia Basin found that of 631 wells examined, 127 (approximately 20 percent) had an average nitrate-nitrogen level above the state drinking water standard at least once during the past three years. It is not known if the elevated nitrate levels have harmed the health of people living in the mid-Columbia Basin. Currently, doctors do not report such public health information so it is impossible to know the health affect.


In May 1995, the Washington State Departments of Agriculture, Ecology, Health and the Conservation Commission directed a subcommittee of the Interagency Ground Water Committee to conduct an environmental and public health assessment of elevated nitrate levels in ground water. The subcommittee studied an area that included Adams, Benton, Franklin, Grant, Lincoln, and Whitman counties. The review of nitrate contamination accomplished the following:

Where are nitrate levels high in the mid-Columbia Basin?

In the Report on Nitrate Contamination of Ground Water in the Mid-Columbia Basin, the subcommittee’s conclusion is that nitrate contamination of ground water at concentrations above state drinking water standards does exist within the mid-Columbia Basin. Wells with high nitrate-nitrogen levels are clustered within eastern Benton County, western Franklin County, Othello, Quincy, and Moses Lake areas.

Shallow wells of less than 300 feet in depth appear to be at much greater risk for nitrate contamination than deeper wells. Most private, domestic drinking water wells are shallow wells.

Should I be concerned about my drinking water?

Most people in the area get their drinking water from public water systems. These supplies are routinely monitored and have few problems. Sixty-six percent of the population has drinking water which has not exceeded state drinking water standards for nitrate. Public water supply systems serving 13 percent of the basin’s population have, at least once in the past three years, used ground water which exceeded state drinking water standards. The report looked closely at this finding and determined that, in most of these cases, the public water supply systems used more than one water source. The wells contaminated by high nitrate concentrations were likely one of several sources. When these various water sources were combined, the quality of water delivered to the consumer by public water systems had nitrate concentrations below drinking water standards.

However, the report shows that a significant number of people using private domestic wells may currently be exposed to drinking water which exceeds the nitrate-nitrogen levels for safe drinking water. If you live in the areas identified in the report and get your drinking water from a private domestic well, then you should have your water tested as soon as possible.

How do I get my water tested?

The Washington Department of Health has a fact sheet on how to get water from private wells tested. The Department of Health is also developing a strategy to communicate to local citizens the possible hazards of nitrate in drinking water and how to help protect drinking water supplies from contamination.

What is being done to reduce nitrate contamination?

Steps are already underway to reduce nitrate contamination. Ecology has been working with food processors, municipal wastewater treatment plants, and other industries that apply treated wastewater to land. Many treatment plants have lowered nitrate levels in their discharge water, thus reducing nitrate from seeping into ground water. Area conservation districts are promoting the use of Best Management Practices for agriculture. These practices are expected to reduce the amount of nitrogen getting into the ground water over time.

At the request of the Adams, Franklin and Grant Counties' Boards of Commissioners, Ecology designated those counties as the Columbia Basin Groundwater Management Area in February 1998. This designation is a key part of the long-term solution to protect the ground water from nitrate pollution. The management area is a locally driven and locally managed process that will identify and implement specific actions to reduce nitrate contamination. Ground water advisory committees representing various interests within the mid-Columbia region are working toward recommendations to reduce nitrate contamination in groundwater. Current information about this effort can be obtained from the Columbia Basin GWMA website: http://www.cbgwma.org/.

To obtain A Report on Nitrate Contamination of Ground Water in the Mid-Columbia Basin, please contact Ecology’s Publications Office at (360) 407-7472 and ask for publication number 96-17.  You may also go to Ecology's Publications Website and find a copy of the publication at https://fortress.wa.gov/ecy/publications/SummaryPages/96017.html.

Who to contact for more information

For more information on nitrate contamination in the mid-Columbia Basin, contact any of the following:

Kirk Cook, Dept. of Agriculture; (360) 902-1804; e-mail kcook@agr.wa.gov; Director’s Office, P.O. Box 42560, Olympia, WA 98504-2560

David Jennings, Dept. of Health; (360) 586-9041; e-mail david.jennings@doh.wa.gov; Drinking Water Division, P.O. Box 47822, Olympia, WA 98504-7822

Laurie Morgan, Dept. of Ecology; (360) 407-6415; e-mail Laurie.Morgan@ecy.wa.gov; Water Quality Program, P.O. Box 47600, Olympia, WA 98504-7600


Back to top of page

Last updated December 2011