Dams on the lower Columbia River and several of its key tributaries have significantly harmed salmon and steelhead populations. For example, Bonneville Dam is a significant barrier to migrating adult chum salmon. In addition, the water behind the dam has inundated historic spawning habitat in the Columbia River and its tributaries. Below the dam, regulated water releases no longer help form salmon habitat in the spring, reducing the quantity and quality of habitat available to migrating salmon.
In tributaries, dams on the Cowlitz and Lewis Rivers eliminated access to areas that can support productive populations of Chinook and coho salmon and steelhead. Hatchery programs were established to mitigate the impact of these dams, but recovery will require restoration of access and reintroduction of these Endangered Species Act-listed populations to blocked habitats. Efforts to improve fish passage, collection and transport, hatchery management practices, and habitat quality and availability are ongoing.
Dams have been removed in the Wind River and White Salmon River watersheds, and monitoring of steelhead, coho, and Chinook recolonization is ongoing.