Emergency Release Targets Salmon and Steelhead Protection
The Army Corps of Engineers deployed cold water from Dworshak Reservoir on July 25 to combat dangerously warm conditions in two major Idaho river systems during an intense heat wave affecting western Idaho and southeastern Washington.
The Clearwater River near Orofino reached 79.7 degrees that day, while the Snake River 25 miles southwest of Lewiston hit 74.4 degrees. When these rivers converge at Lewiston, the mixing of hot water creates conditions hazardous to salmon and steelhead populations already stressed by summer temperatures.
A fish biologist with the Corps explained the biological stakes. Chris Peery noted that steelhead and salmon “start showing signs of stress, migration delay” when temperatures exceed 68 degrees, with mortality possible at higher levels.
Managing Limited Cold Water Resources
Dworshak Dam’s position and structure make it uniquely suited to provide relief. The 717-foot structure—the third tallest dam in the United States—maintains water at 42 degrees year-round at its deepest point, creating a natural cold-water reserve that can be released strategically downstream. The reservoir holds more than 3.4 million acre-feet of water.
The Corps coordinated the release with the National Marine Fisheries Service and U.S. Fish and Wildlife Service, both of which oversee salmon and steelhead protection under federal law. The controlled discharge succeeded in holding temperatures behind Lower Granite Dam at 66.1 degrees or cooler.
However, the tool has sharp limits. Peery acknowledged that “there is a limited amount of water that we can release from Dworshak,” and careful management is required to maintain cool conditions in the Lower Granite tailrace without depleting the reservoir. Multiple factors beyond dam operations influence river temperatures—agricultural and industrial water demands, habitat quality, drought severity, snowpack levels, and precipitation all play roles.
Historical Context and Fish Mitigation
Dworshak Dam, constructed beginning in 1966, physically blocks salmon and steelhead from reaching natural spawning grounds upstream. The structure’s 717-foot height made installation of a traditional fish ladder impractical. To address fish losses caused by the dam’s construction, federal authorities and the Nez Perce Tribe established the Dworshak National Fish Hatchery, which operates today under joint management by the U.S. Fish and Wildlife Service and the tribe.
Cold-water releases from the dam provide tactical short-term protection but cannot solve temperature problems throughout the entire river system. A 2024 report from Save Our Wild Salmon noted that while cold water offers benefits, those advantages dissipate quickly in summer heat. The coalition further argued that a free-flowing Lower Snake River would enhance the cooling benefits of Dworshak releases, a position that remains contested among water managers and conservation groups.
The Corps’ July 25 action reflects the narrow operational flexibility available to federal dam managers during extreme heat events. The release kept critical sections of the Clearwater and lower Snake rivers within survivable ranges for the fish species that depend on them, though such measures address symptoms rather than root causes of seasonal temperature stress.
What Comes Next
As climate patterns continue to produce intense summer heat, the Corps will likely face similar decisions in coming years. Managers must balance fish protection against competing demands for water storage and power generation. Continued coordination with fisheries agencies will shape how aggressively cold-water reserves are deployed when temperatures spike.
For more on regional water management and environmental concerns, see Idaho Panhandle Groups Agree on Major Public Lands Designations for Bonner, Boundary Counties and Invasive Brown Trout Discovered in Ashley Lake and Church Slough Waters.