Emergency Water Release Targets Salmon Habitat Protection
The Army Corps of Engineers released cold water from Dworshak Reservoir on July 25 to lower river temperatures across the Clearwater and Snake Rivers during a heat wave that pushed local waterways toward dangerous levels for fish populations.
Temperatures in the region had climbed significantly by late July. The Clearwater River near Orofino measured 79.7 degrees on July 25, while the Snake River 25 miles southwest of Lewiston reached 74.4 degrees on the same day. Both rivers converge at Lewiston, creating a confluence zone critical to regional aquatic ecosystems.
The cold-water release proved effective in the immediate downstream area. Water temperatures behind Lower Granite Dam, located further downriver, remained at 66.1 degrees or cooler following the intervention, well below stress thresholds for sensitive species.
Protecting Fish From Temperature-Related Stress
Salmon and steelhead begin experiencing physiological stress when water temperatures exceed approximately 68 degrees, according to Corps fish biologist Chris Peery. “Above about 68 degrees, they start showing signs of stress, migration delay, and, if temperatures go higher, mortality can start to occur,” Peery noted.
The Corps coordinated the emergency release with the National Marine Fisheries Service and U.S. Fish and Wildlife Service to maximize the protective effect while managing Dworshak’s water reserves responsibly. Peery acknowledged the practical constraints: “If we manage it carefully, we can help cool the Snake River so it stays around 68 degrees in the tailrace of Lower Granite Dam, but there is a limited amount of water that we can release from Dworshak.”
Dworshak Reservoir maintains exceptionally cold water throughout the year due to its depth and intake design. The 717-foot-tall dam, the third tallest in the United States, holds a reservoir 600 feet deep with a storage capacity exceeding 3.4 million acre-feet. Water drawn from the reservoir’s lower depths remains at approximately 42 degrees year-round, making it an ideal source for temperature management during warm-weather periods.
Infrastructure and Tribal Partnership
Construction of Dworshak Dam began in 1966, establishing a water management tool that has served flood control, hydroelectric generation, and fish protection purposes across the region. The Dworshak National Fish Hatchery, operated jointly by U.S. Fish and Wildlife and the Nez Perce Tribe, operates within the facility and benefits from the cold-water environment the reservoir provides.
Environmental advocates have noted limitations to cold-water release strategies. A 2024 report from Save Our Wild Salmon documented that benefits from such releases do not persist over extended distances or durations, and the cold water does not cool the three reservoirs positioned downstream of Lower Granite Dam. This reality underscores the importance of targeted, carefully timed releases like the July 25 intervention.
What Comes Next
The Corps will continue monitoring river conditions throughout the warm season and releasing water as conditions warrant. The Lewis-Clark Valley faces ongoing summer heat, and water management agencies will balance competing demands: protecting aquatic life from thermal stress while maintaining adequate storage for flood control and power generation in the months ahead. Coordination among federal agencies and tribal partners will remain essential to preserving salmon and steelhead populations that depend on cool-water habitat.