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.

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.

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