Watershed Facts

What is a Watershed? A watershed is an area of land that contains a common set of streams and rivers that all drain into a larger water body such as the Chehalis River or Grays Harbor.

Here are some facts about the Chehalis Watershed:

  • The Chehalis River Basin is the largest watershed that originates entirely within the boundaries of Washington State
  • Over 140,000 people call the Chehalis Basin home (as of 2000 Census). 220,000 are projected to live in the basin by 2025
  • Water Source: There are no significant areas with snow pack high in our watershed. This means that streams are maintained by groundwater flows and rainfall only.
  • Lakes: There are 180 lakes, ponds and reservoirs in the basin
  • Streams: There are 3,350 miles of rivers and streams in this basin
  • Forests: 87% of the land use in the basin is forestry
  • Agriculture: 8% of the land in the basin is used for agriculture

Click here to download a document with these and more facts.

Chehalis River Watershed Sub-basins




In addition to the Chehalis River Mainstem there are 11 sub-basins in the Chehalis River Watershed and the Grays Harbor Estuary. Click the name to learn more!





Salmonids in the Chehalis River Watershed include Chinook, coho, chum, steelhead, bull trout and cutthroat.