Pilchuck River Watershed

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The Pilchuck River is a 341 square km lowland tributary to the Snohomish River. It originates in the cascade foothills in a glacially formed valley between the Sultan River and South Fork Stillaguamish River. It flows into the lowlands, past the outskirts of Granite Falls, past Lake Stevens in a trough carved into the glacial plateau, and finally entering the Snohomish River at the town of Snohomish.

Notes

Workgroup

This effort is linked to Coordinated Investment pilot work
There is no formal Coordinated Investment workgroup in place.

Excerpts

The middle reaches are identified as a 'primary restoraiton' zone in the Snohomish River Basin Salmon Conservation Plan (SBSRF 2005). Savery & Hook 2003 documents habitat conditions and Chinook salmon use in the pilchuck river.

Roughly 100-200 Chinook return to spawn in the pilchuck river (Savery & Hook 2003). Winter Steelhead returns have fluctuated from the last high of 1522 in 2005 to the most recent 294 in 2010 (WDFW survey data). Puget Sound Steelhead are now listed as threatened with becoming endangered, and the Pilchuck runs are considered depressed (WDFW). The Pilchuck supports a substantial proportion of the approximately 100,000 coho that return to the Snohomish system every year.

(Savery & Hook 2003) describes a habitat survey of the Pilchuck River. With the clearing of forests, the river has become wide and shallow, and poorly shaded. Pool frequency is many times lower than in more wild rivers. Large logs in the river historically created the pools and riffles which are where chinook salmon prefer to spawn. Likely caused by the shallow channel, lack of shading and loss of wetlands, river temperature is very high in summer (the river is listed for violating water quality standards for temperature. High temperature reduces the rivers ability to carry oxygen, causing stress in cold water fish. Long reaches of river have rock on the bank (rip-rap), and do not provide pools, overhanging plants or other cover. Logs in the river are small, and form many fewer jams below the Russell Road bridge than in a more natural river. This lack of wood is anticipated to be causing the wide shallow channel with few pools. The low quality of floodplain vegetation provides few opportunities for wood to enter the river. Lack of wood and forests results in bank erosion, which adds fine sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. to the river, which can clog gravel used for spawning.

Chinook enter the river before fall rains, and usually hold in pools near spawning grounds. Small infrequent pools, and warm water make conditions difficult for these fish (Savery & Hook 2003).

Chinook salmon returns to the Pilchuck River have not been consistently monitored over time. Estimates of chinook salmon returns to the Pilchuck River since 1999 range from 100 to 200 fish. It is presumable that availability of suitable habitat and water quantity and quality has an effect on both juvenile and adult survival and abundance. Land uses have contributed to changes in flow routing and timing in the river, low channel roughness, prevalent bank armoring, and a lack of habitat complexity in the channel. Glides that are long and often shallow dominate habitat in the river. Pool spacing is frequently high, thereby offering little migratory refuge for adult chinook and other salmonids. Off-channel rearing habitat does not exist in the Pilchuck River study area, except in the side channel, Reach 12 (RK 23.1). The Pilchuck River has been placed on the 303(d) list for excessive temperature levels (WDOE, 1997) and experiences temperatures well above 15.5°C during chinook migration. (Savery & Hook 2003)

The Centennial Trail beginning in Snohomish follows an old railroad grade along the lower Pilchuck River valley. Much of the river is zoned 5 acre rural residential.