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Save Our Wild Salmon

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September 19, 2023

Joseph Bogaard,, 206-300-1003
Tanya Riordan,, 509-990-9777

Rising River Temperatures Take a Toll on Snake River Salmon

SEATTLE (Sept. 19, 2023) — Throughout this summer, temperatures have been rising to lethal levels in the Columbia River Basin. Save Our wild Salmon Coalition and 16 NGOs released a weekly Hot Water Report, tracking water temperatures in the lower Snake and lower Columbia river reservoirs and reporting how increasingly hot waters impact cold-water-reliant salmon and steelhead leading to their low returns each year. The once-abundant anadromous fish populations in the Columbia-Snake River Basin are on the brink of extinction today due primarily to harms caused by federal dams and their warming reservoirs. The four reservoirs on the lower Snake River are large, stagnant pools that absorb enormous amounts of solar radiation that cause the water to warm. These waters inundate and destroy diverse micro-habitats that healthy rivers support, including cold-water refuges that salmon and steelhead rely upon during their migration.

Below, we present a summary of the highest water temperatures recorded in each of the 4 reservoirs in the lower Snake River and the number of days the reservoirs reached above the 68°F “harm” threshold—the legal and biological limit scientists identified to protect salmon.

  • Ice Harbor Dam: On 8/19/23, the reservoir behind the Ice Harbor Dam registered the highest temperature recorded this summer—72.73°F over 4 degrees above the 68°F threshold. The Ice Harbor reservoir registered above 68°F for 62 days.
  • Lower Monumental Dam: On 8/20/23, the Lower Monumental reservoir registered a high water temperature of 71.71°F. The Lower Monumental reservoir registered above 68°F for 60 days.
  • Little Goose Dam: On 8/20/23, the Little Goose reservoir registered a high water temperature of 71.24°F. The Lower Monumental reservoir registered above 68°F for 60 days.
  • Lower Granite Dam: The Lower Granite reservoir was the first reservoir to reach 68°F this summer. This reservoir registered a high temperature this summer of 71.20°F on August 22, 2023. Lower Granite reservoir registered above 68°F for 32 days, fewer days compared to other reservoirs, due to the US Army Corps of Engineers' annual release of cold waters from the Dworshak reservoir. However, the benefit of this cold water release does not last long in the heat of the summer and does not cool the other three downstream lower Snake reservoirs.

For over 60 days, salmon and steelhead migrated through water temperatures between 68°F - 72°F on the lower Snake River. Migration stops altogether when water temperatures reach 72 to 73°F. Salmon that have stopped or slowed their migration, and languish for days or weeks in warm water, begin dying from stress and disease. This summer, due to hot water in the reservoirs of the lower Columbia and lower Snake rivers, roughly 80% of the returning adult Snake River sockeye that entered the mouth of the Columbia River died before spawning.

Since the completion of the dams on the lower Snake River, wild Snake River fish returns have plummeted and are far below the levels required to delist them from the Endangered Species Act, much less meet their Columbia Basin Partnership recovery goal. According to Nez Perce Tribe fishery scientists, nearly half of Snake River salmon and steelhead populations have reached quasi-extinction thresholds—a critical threshold signaling they are nearing extinction, and without intervention, many may not persist. In addition, without big improvements in water quality, federal scientists predict that adult Snake River sockeye survival will further decline by 80% in coming years, likely resulting in extinction.

A restored lower Snake River would provide the largest availability of high-quality free-flowing, cold-water habitat for salmon populations to recover to significant levels of abundance, mitigating the impacts of changing ocean conditions and climate change. The benefits of dam removal would improve the ability of migrating fishes to access high-elevation, groundwater- and snowmelt-fed freshwater refuges, likely increasing survival and productivity in what will be an otherwise inhospitable future climate.

Salmon and steelhead—and endangered Southern Resident orcas and other fish and wildlife that highly depend on salmonare running out of time. The current status quo to keep the lower Snake River dams violates our nation’s 150-year old Treaty commitments to Northwest Tribes, the Endangered Species Act, and the Clean Water Act to reduce heat pollution known as hot water temperatures. At this moment, we have an urgent opportunity to restore ecosystem health across the basin and recover salmon and steelhead by removing the four lower Snake River dams and replacing the dams’ services. We must develop and deliver a comprehensive solution to restore a healthy, and resilient lower Snake River, protect the Northwest native fish from extinction, and uphold our nation's promises to Tribes by reconnecting this emblematic fish to 5,500 miles of pristine, protected river and streams in Idaho, Oregon, and Washington.

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, American RiversAssociation of Northwest SteelheadersColumbia RiverkeeperEarthjusticeEndangered Species CoalitionEnvironment OregonIdaho Conservation League, Idaho Rivers United, Natural Resources Defense Council, National Wildlife FederationNorthwest Sportfishing Industry AssociationOrca NetworkSierra Club, Snake River Waterkeeper, Wild Orca and Wild Steelhead Coalition.

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