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Water Quality Improvement Projects (TMDLs)

Water resource inventory area (WRIA) 7, Washington State.

Water Quality Improvement Projects
Snohomish River Watershed Area Projects


The Snohomish River basin is the second largest watershed that drains into Puget Sound in Washington State. The basin  drains 1,978 square miles and discharges to Possession Sound near the city of Everett, Washington. The river is formed by the junction of the Skykomish and Snoqualmie rivers near the city of Monroe. The river then continues on into an estuary near the city of Snohomish, which then enters Puget Sound near the cities of Everett and Marysville. Streams in the Snohomish basin provide important fish habitat and recreational opportunities. (See Study Area map)

Land use

Historically, the land uses in the Snohomish River basin have been mainly agriculture and forest related. Over the last century, diking and other engineering activities in the lower part of the basin greatly changed how water is stored and managed in floodplain areas. More recently, cities and suburban areas have grown rapidly, creating more change to the natural water cycle.

Water quality issues

Many of the streams in the lower Snohomish Watershed do not meet state standards for swimming and wading because there is too much bacteria in the water. There are also problems with dissolved oxygen, temperature, and pH in some areas (find out more by visiting our Water Quality Assessment webpage). The federal government determined that Chinook salmon and steelhead trout are threatened in many of these areas.

Waterfall on the Snohomish River, Washington State.  Photo courtesy of Ralph Svrjcek, WA Department of Ecology.

Project information

French Creek and Pilchuck River

Snohomish River

Snoqualmie River

  • Ammonia/BOD/Fecal Coliform
  • Temperature

Related Information

WRIA 7: Snohomish Watershed Information (Water web site)
Water information on the Snohomish watershed, including reports and data.

Data resources:

Snohomish River Salmon Recovery (Snohomish Public Works: Surface Water Management Division

Contact us for more information

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