Outside Influences

Fish harvest
Harvest management of Cedar River Chinook salmon in Washington State is managed by the Washington Department of Fish and Wildlife and many Tribes, and overseen by federal courts (Boldt Decision). Some harvest is regulated through the Pacific Salmon Treaty, between the United States and Canada. Learn more about the impact of fish harvest.

Fish hatchery production
SPU does not control hatchery production of Chinook salmon in the Lake Washington basin. Hatchery production of Chinook salmon within the Lake Washington system occurs at the Issaquah Salmon Hatchery and at the University of Washington.

Land use decisions and habitat
SPU has limited influence on the effects of land and water management practices on the Cedar River downstream of Seattle’s municipal watershed ownership boundaries.

Peak flows
Water resource management facilities and operations on the Cedar River have the ability to moderate, but not eliminate the magnitude of peak flow events in the Cedar River. Large salmon redd scouring events are driven primarily by heavy rainfall events during the fall and winter. These events have occurred in the past and are expected to occur with roughly the same frequency in the future.

The average water residence time in the lake is approximately 2 years. Very large amounts of thermal energy are collected in the surface waters of Lake Washington during the spring and summer. Relatively large inputs of thermal energy are also input to the river as it flows between Landsburg and Renton.

Global climate change can alter thermal inputs to watersheds and their rivers and lakes. These changes can affect water temperature and hydrologic features in the Cedar River, Lake Washington, Lake Washington Ship Canal, Puget Sound, and the Pacific Ocean.

Ocean conditions
Chinook salmon are also affected by ocean conditions such as El Nino, La Nina, Pacific Decadal Oscillation, and coastal upwelling.

El Nino and La Nina impact weather patterns affect Chinook habitat in the Cedar River, as well as in marine environments. Learn about the influence of ocean conditions and survival.

Ballard Locks operations, associated fish passage facilities and Lake Washington elevation management
The complex set of operations conducted by the U. S. Army Corps of Engineers at the Ballard locks affects upstream and downstream fish passage in the Lake Washington Ship Canal.

Marine nearshore conditions outside Seattle city limits
Near-shore marine habitats are especially important for young salmon as they migrate from Lake Washington to the open ocean. When fully functional, these potentially rich environments support rapid growth in the young fish and help prepare them for life at sea.

Rerouting of the Cedar River into Lake Washington
In 1917, the elevation of Lake Washington was reduced by approximately nine feet, the Cedar River was rerouted from the Duwamish River Basin into Lake Washington and the outlet of the Lake Washington was shifted from the Black River, at the south end of the Lake, to the Lake Washington Ship Canal. These changes continue to pose associated thermal, migratory and life history diversity challenges for both adult and juvenile Chinook.