ABOUT THE CHEHALIS BASIN
The Chehalis Basin, Water Resource Inventory Areas (WRIA) 22 and
23, is one of the larger river basins in the state of Washington. It
is bound on the west by the Pacific Ocean, on the east by the
Deschutes River Basin, on the north by the Olympic Mountains, and on
the south by the Willapa Hills and Cowlitz River Basin.
Elevations vary from sea level at Grays Harbor, to 5,054 feet in the Olympic National Forest.
The Chehalis Basin encompasses 2,520 square miles and drains 2,660 square miles.
The Chehalis River system flows through three distinct eco-regions; Cascade (including the Olympic Mountains), Puget Lowland, and Coast Range before emptying into Grays Harbor near Aberdeen.
The Chehalis Basin encompasses large portions of Grays Harbor, Lewis, and Thurston counties, and lesser parts of Mason, Pacific, Cowlitz, Wahkiakum, and Jefferson counties.
The mainstem and South Fork Chehalis drain areas west and south of the City of Chehalis. Two major tributaries in mid-basin, the Newaukum and Skookumchuck Rivers, have their headwaters in the foothills of the Cascade Range. Another mid-basin tributary, the Black River, originates in Black Lake.
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:
- Black
- Boistfort
- Cloquallum
- Hoquiam-Wishkah
- Humptulips
- Lincoln
- Newaukum
- Satsop
- Skookumchuck
- South-Harbor
- Wynoochee
Chehalis River Council provides additional information on each subbasin.
Salmonids in the Chehalis River Watershed include Chinook, coho, chum, steelhead, bull trout and cutthroat.
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