The diversity of streams in the county is a reflection of the diversity of its geography. From the small rivulets that begin high in the Cascade Mountains, to the brooks that flow gently across the lowlands, to the five major rivers of the county, there are over 4,800 kilometers (3,000 miles) of perennial streamcourses in King County.
The Snoqualmie watershed covers 677 square miles, and supports agriculture, forestry, rural residences, and urban development. From Snoqualmie Falls to its meeting with the Skykomish, the Snoqualmie River travels over 43 miles. Tributaries of the Snoqualmie produce more coho salmon than all of Oregon, and a growing population of Chinook salmon return to the Snohomish and Snoqualmie to spawn. Habitat in the basin has been affected by roads, agriculture, and flood control efforts, and much of the Snoqualmie River has little to no riparian vegetation.
- Counties: King, Kittitas, Snohomish
- National Estuary Programs: Puget Sound
- Other Watersheds Upstream: None
- Other Watersheds Downstream: Snohomish