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Water Quality Improvement Projects (TMDLs)

Water resource inventory area (WRIA) 37, Washington State.

Water Quality Improvement Projects
Yakima River Basin Area


The Yakima River originates in Kittitas County, Washington State, from the Keechelus, Kachess, and Cle Elum lakes, all located on the east side of the Cascade Mountains near Snoqualmie Pass. The river flows over two hundred miles, heading southeast through the Kittitas and Yakima valleys, then discharges into the Columbia River near Richland. River tributaries include the Cle Elum, Teanaway, and Naches rivers, as well as numerous creeks and irrigation returns. The confluence of the Yakima and Naches Rivers at the city of Yakima divides the Yakima River into "upper" and "lower" portions. About one-half of the Yakima Basin (Basin) is within and occupies most of Yakima County. The upper part of the Basin lies in Kittitas County and occupies most of that county. The southeastern part of the Basin occupies about one-half of Benton County, and the southern part of the Basin extends slightly into Klickitat County. The entire Yakima basin lies within areas either ceded to the United States by the Yakama Nation or areas within the boundaries of the Yakama Indian Nation. The Yakama Reservation occupies about 40 percent of Yakima County and about 15 percent of the Basin. Along with its tributaries, the river system drains about 6,150 square miles or 4 million acres.

Average annual precipitation ranges in the Yakima Basin vary from 91 inches annually at Snoqualmie Pass (at the headwaters of the Yakima River in the Cascade Range) to 7.9 inches annually in the city of Yakima. Most of the water in the Yakima River comes from snowmelt, and is caught in a series of five reservoirs to ensure a sufficient water supply throughout the irrigation season. Much of the water is diverted for irrigation in the Yakima Valley, but some is recovered through surface and subsurface routes. From 50 to 100 percent of the water delivered to the lower basin from the Naches River and upper Yakima River is diverted for agriculture during the irrigation season.

Land use in the Basin includes nearly 40 percent forested, 40 percent rangeland, 15 percent cropland, and the remaining acreage in other land uses. Irrigated agriculture, the main economy of the Basin, occupies about 1,000 square miles. Cattle grazing is the main use of 2,900 square miles of rangeland. Timber harvest, cattle grazing, and recreation are the major uses of the 2,200 square miles in the forested areas of the Basin to the north and west. About one-fourth of the forested area is designated as wilderness.

Water quality issues

Water quality issues in the Basin range from fecal coliform bacteria to suspended sediments and turbidity, as well as toxics and temperature.

The role of food production is evident in this green high desert valley east of the Cascade Foothills. The Kittitas and Yakima Valleys enjoy the most sophisticated and extensive network of irrigation canals and returns in the world. Each withdrawal and return has direct effect on the quality of water. The Yakima Valley watershed is listed on the state 303(d) list of impaired waters for Fecal Coliforms, Temperature, Turbidity, Toxic Chemicals, Sulphur and Nitrogen Compounds, and reduced Dissolved Oxygen. Please see the state's water quality assessment for a list Yakima River water quality issues.

Why this matters

The water quality issues in the Basin impact the beneficial uses of the water, potentially making it unsafe for drinking or recreation and threatening the health of aquatic animals and fish living in it. At this time there are two fish species listed as endangered: Mid-Columbia Bulltrout and Mid-Columbia Steelhead. Studies in the Upper and Middle Yakima River indicated that temperature, toxic chemicals, lack of foraging habitat and refuge from predators was creating obstacles for survival of these species. At this time, Ecology's temperature standards are based on current understanding of survivable temperature ranges.

What is being done

There are a number of water quality improvement projects, mainly in the form of total maximum daily loads (TMDLs), in various stages of development across the watershed. Please use the following links to get more information on a project.

Project information

Projects Parameters
Crystal Creek Multi-parameter
Granger Drain Fecal Coliform
Naches River, Upper Temperature
Selah Ditch Multi-parameter
Teanaway River Temperature
Wilson Creek Fecal Coliform Bacteria
Yakima River, Mid Basin Tributaries Fecal Coliform Bacteria
Yakima River Toxics
Yakima River, Lower DDT
Yakima River, Upper Organochlorine Pesticides
Suspended Sediments

Related information

WRIA 37: Lower Yakima Watershed Information (Environmental Assessment Program web site)

WRIA 38: Naches Watershed Information (Environmental Assessment Program web site)

WRIA 39: Upper Yakima Watershed Information (Environmental Assessment Program web site)


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Last updated December 2013