Hydropower and Dams
Salmon and steelhead travel between spawning and rearing habitats in rivers to areas where they grow and develop, and eventually to the ocean. When hydropower dams and other barriers block their migration, salmon populations decline.
General impacts from dams can include blocked fish passage and delayed migration. One study showed that dams block more than 55 percent of the spawning and rearing habitat once available to salmon and steelhead in the Columbia River basin.49
In addition, dams can create places where salmon become easy prey as they wait to pass through the dams. Seals and other animals feed on the congregating salmon at the entrances to fish ladders. Dams also can kill salmon, cause temperature and water quality issues, slow downstream migration, and alter environmental processes, which impact salmon habitat.
As a result, hydropower systems are highly regulated and highly mitigated in an attempt to offset impacts to salmon. Government agencies, industry, treaty Indian tribes, and nonprofits have worked diligently to address the impacts of dams, while attempting to preserve the benefits dams provide for people, such as flood control, relatively green and on-demand power, shipping assistance, and irrigation of farmland.
Each hydropower facility is unique and requires customized actions to minimize its effects on salmon. In addition, the cumulative impacts of all dams must be considered for salmon that migrate through hundreds of miles of rivers to and from the ocean.
There have been significant changes to increase salmon’s survival through the dams across the state. Indian tribes have led efforts to remove dams on the Elwha, Middle Fork Nooksack, and Pilchuck Rivers. There are additional efforts underway to improve passage such as at Mud Mountain Dam near Enumclaw or to place salmon above dams where they have not been for nearly 100 years such as at Chief Joseph Dam near Bridgeport and Grand Coulee Dam near the town of Grand Coulee. Efforts also are underway to adjust spill schedules at large dams to increase the amount of water available for salmon during critical migration periods. The State and tribes also have secured a federal permit to reduce the number of sea lions feeding on migrating salmon below dams in the lower Columbia River.
Continued cooperation, diligence, advocacy, and robust science is required to ensure dams and hydropower systems continue to improve operations and passage survival for salmon and steelhead.
Each hydropower facility is unique and requires customized actions to minimize its effects on salmon.
Photograph of Ross Dam in Whatcom County courtesy of the U.S. Army Corps of Engineers