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Seattle’s Urban Watersheds

Seattle has four major receiving waters: Lake Washington, the Ship Canal and Lake Union, the Duwamish River and Puget Sound. Three urban basins, or watersheds, contribute to each of these receiving waters. These watersheds represent discrete areas that contribute to Seattle's receiving waters through stormwater drainage and combined sewer overflows (CSOs).


Duwamish River

  • Duwamish Basin
  • East Waterway Basin
  • West Waterway Basin

Lake Washington

  • North Lake Washington Basin
  • Central Lake Washington Basin
  • South Lake Washington Basin

Puget Sound

Ship Canal/Lake Union

  • North Lake Union Basin
  • South Lake Union Basin
  • Ship Canal Basin