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Scientists alert policymakers in letter that urgent action needed to cool river waters to prevent salmon extinction


55 scientists say restoring free-flowing lower Snake River in Washington State is critical

October 22, 2019


BOISE, ID – Fifty-five scientists sent a letter today to policymakers in Washington state, Idaho and Oregon highlighting the need to address the harmful effects of hot water on salmon and steelhead in the Columbia-Snake River Basin due in large part to reservoirs behind federal dams.

Salmon and steelhead are cold water fish and their survival depends on river temperatures not exceeding 20°C/68°F. The effects of the federal hydro-system, however, are now combining with climate impacts to push reservoir temperatures well above 68°F for extended periods in summer months and delaying normal fall cooling.

Dave Cannamela, M.S., Idaho Fish and Game (IDFG) fisheries biologist (ret), Boise, Idaho said, “Hot water kills cold water fish. That’s what’s happening now when adult salmon try to return home through reservoirs that are too warm for long periods of time.”

Climate heating is leading to more frequent, more intense, and longer lasting high temperature episodes resulting in greater harm to the Northwest’s native fishes. In 2015, low flows and unusually hot weather pushed the Columbia and Snake river temperatures as high as 75°F in some areas for weeks at a time. More than 250,000 returning adult salmon died in the hot water reservoirs. Ninety-six percent of the endangered adult Snake River sockeye that returned from the ocean to the Columbia River in 2015 died before reaching Lower Granite dam.

Margaret Filardo, Ph.D., Fish Passage Center fisheries biologist (ret), Portland Oregon said, “The issue of increased temperatures and the potential impacts to salmonid survival has long been recognized in the Columbia/Snake River hydrosystem. The four lower Snake reservoirs typically add several degrees to the overall water temperature in the river, commonly driving it above 68°F for weeks at a time, causing salmon to die. This problem must be solved if we hope to save the Northwest’s most iconic fish – endangered salmon and steelhead populations – from extinction.”

Howard Schaller, Ph.D., USFWS fisheries biologist (ret), Portland, Oregon said, “The four long slackwater reservoirs created by the lower Snake River dams absorb sunlight and elevate water temperatures to levels that are lethal for adult salmon and steelhead. These elevated water temperatures in the Columbia and Snake rivers, including adult fishways at dams, is a long-recognized problem that to date remains largely unmitigated. Fishways at the dams often expose migrating adults to the highest temperatures and thermal stress encountered in the hydrosystem. The science is quite clear on this.”

Salmon and steelhead populations in the Snake and Columbia rivers have been declining for decades; this year brought some of the lowest counts on record. Just 17 adult Snake River sockeye successfully returned to spawning gravels in the Stanley Basin of central Idaho this summer. More than a million wild spring/summer chinook once returned annually to the Snake River Basin, but this year brought fewer than 5,000.

The low returns are also harming other fish and wildlife populations that rely on salmon and steelhead, including critically endangered Southern Resident orcas. In 2015, NOAA included these salmon-eating orcas among eight “Species in the Spotlight” – species the agency described as most likely to go extinct unless immediate action is taken. Since NOAA’s announcement, 8 more orcas have died. Just 73 individual whales survive today.

The federal dam operators – Army Corps of Engineers, Bonneville Power Administration, and U.S. Bureau of Reclamation – are analyzing recovery options and developing a new federal salmon plan ordered by a federal court. In 2016, a federal judge ruled that the government’s last plan for Columbia Basin salmon was inadequate and illegal.

With that ruling, the judge ordered the federal agencies in charge to study all credible salmon recovery alternatives, including the removal of the lower Snake River dams, as required by the National Environmental Policy Act (NEPA), and develop a new federal plan that will protect salmon and steelhead populations imperiled by the federal hydrosystem. A draft Environmental Impact Statement is expected in February 2020, and a final EIS and Biological Opinion, or federal salmon plan, are both expected in September 2020.

Rick Williams, Ph.D., former chair of the Independent Scientific Advisory Board for the Northwest Power and Conservation Council, fisheries consultant, Boise, Idaho said, “As federal agencies announce their plans for Snake/Columbia salmon policy and actions in early 2020, they must do more than just tweak the system a bit to deal with temperature. We will fail to solve the hot water problem, and fail to restore salmon runs, if federal agencies select any long-term plan that does not include removal of lower Snake dams. That action appears to be the only one available that can significantly lower water temperatures and aid in recovering Idaho’s salmon and steelhead populations.”