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SOS Blog

Save Our Wild Salmon

Hot Water Report 1


Welcome to Save Our wild Salmon’s Hot Water Report 2021. During the summer, this weekly report will provide an update on real-time water temperatures in the lower Snake and Columbia river reservoirs via graphs and analyses, a report on the highest weekly water temperature at the forebay/reservoir of each dam, and the status of adult returns for the different salmon and steelhead populations as they make their way back to their natal spawning grounds. We’ll also hear first-hand from scientists, fishers, guides, advocates, and other experts about challenges facing the Columbia and Snake rivers - and the opportunities we have to restore these rivers, leading to the recovery of healthy, resilient fish populations and the many benefits they deliver to the Northwest’s culture, economy, and ecology.

The once-abundant anadromous native fish populations that call the Columbia-Snake River Basin home are struggling to survive primarily due to multiple harmful effects caused by the system of federal dams and their reservoirs. The federal hydro-system creates conditions that harm and kill both juvenile and adult salmon and steelhead, including by elevating water temperatures in the large, stagnant reservoirs, especially in the summer months. As cold water species, these fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit. The longer and higher temperatures rise above 68°F, the greater the harm, including disruption in their migration, increased metabolism, increased susceptibility to disease, reduced fecundity or reproductive potential (by reducing egg viability), and in the worst case - death.

These harmful hot water episodes above 68 degrees in the Columbia and Snake Rivers are increasing in duration, frequency, and intensity. Our changing climate is making this bad situation for the Northwest’s iconic fish even worse. Our region and nation must take urgent action to lower these temperatures - or scientists tell us that we will lose these species forever. Restoring a freely flowing lower Snake River by removing its four federal dams is our best and very likely only option for lowering water temperatures in this 140 mile stretch of river in southeast Washington State. Restoring the Snake River is one essential part of what must be a larger regional strategy to protect and rebuild healthy, abundant salmon and steelhead populations in order to benefit other fish and wildlife populations, including critically endangered Southern Resident orcas, to honor tribal rights, and to ensure prosperous communities across the Northwest.

Will you be on the river this summer? Do you have a story or photo you would like to share? Please send them to Martha Campos

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Washington Sierra Club, Columbia Riverkeeper, Idaho Rivers United, National Wildlife Federation, Snake River Waterkeeper, Northwest Steelheaders, Defenders of Wildlife, and Endangered Species Coalition.

II. READING THE DATA - Lower Snake and Columbia River Temperatures


The daily mean temperature at the four reservoir forebays (immediately upstream from the dam) in the lower Snake River (above) and the lower Columbia River (below) for 2021 is represented with solid lines and their 10-year average (2011-2021) temperatures with dashed lines of the same color. The dotted line across the graph represents the 68°F “harm threshold” for adult and juvenile fish. Salmon and steelhead begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit. The longer temperatures remain above 68°F and the higher the temperatures rise above 68°F, the more severe the potential effects, including: increased metabolism, increased susceptibility to disease, reduced fecundity or reproductive potential, and/or death. (see Issue 1 for more detailed information).

A note on the lower Snake River Water Temperature Graph: The mean water temperature data from these reports comes from the USGS Current Conditions for Washington State and the 10-year average water temperature data comes from the Fish Passage Center. USGS began recording water temperatures at Ice Harbor and Lower Monumental on June 16, 2021, Little Goose on June 19, 2021, and Lower Granite on June 18, 2021. Although we are not able to compare spring water temperatures to summer water temperatures, we can see June temperatures rising above the 10-year average and all water temperatures in the lower Snake River are above 60°F. Harmful water temperatures reached in the lower Snake and lower Columbia River reservoirs: This week, all reservoirs exceed the 10-year average for this time of the year. On the lower Snake River, the Lower Monumental and Little Goose Dams have peaked over the threshold (68 degrees) this week. In addition, the Little Goose dam has significantly peaked above the 68°F threshold, with a high mean temperature of 71.6°F.

Like the lower Snake River, current reservoir temperatures in the lower Columbia River are above the 10-year average for this time of the year. The Dalles, Bonneville, John Day and McNary reservoirs all registered temperatures at or above 68°F.


On the lower Snake River this week, the Little Goose Dam registered the highest temperature at 73.04°F - nearly 5°F warmer than levels that coldwater fish require. Lower Monumental Dam had the second-highest temperature at 69.8°F.

On the lower Columbia River, all reservoirs registered high temperatures above 68°F for multiple days. Both John Day Dam and the Bonneville Dam registered the highest temperature this week at 69.8°F, followed closely by the McNary Dam with a high temperature of 69.44°F.

Temperature data included in these reports come from the USGS Current Conditions for Washington State and the Fish Passage Center. Graphs and tables were assembled by SOS Staff.

 IV. COLUMBIA RIVERKEEPER REPORT (2017): Removing dams will reduce lower Snake River water temperatures and deliver critical survival benefits to endangered salmon and steelhead

In 2015, high water temperatures driven by hot weather and a low snowpack killed more than 250,000 salmon in the Columbia and Snake rivers. This incident of mass mortality inspired SOS member organization Columbia Riverkeeper to publish a report - Columbia Riverkeeper White Paper: Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015 - that evaluated what the water temperatures of the lower Snake would have been during the summer of 2015 if its four federal dams did not exist.


Using an U.S. Environmental Protection Agency (EPA) water temperature model, Columbia Riverkeeper found that each of the four reservoirs behind the dams increased the river temperature by about 2 °F. The reservoirs create large, stagnant pools that steadily absorb heat from the sun. When warm water from one reservoir moves downstream to the next pool, the already warmed water is stopped again by the next dam and continues to heat up. The model indicates clearly that this effect would be absent from the free-flowing lower Snake River.

Since Columbia Riverkeeper published its study in 2017, federal science agencies have released more information corroborating its findings. First, the U.S. Army Corps of Engineers used EPA’s model, as well as another water temperature model, to recreate Columbia Riverkeeper’s study—and got similar results. Second, the EPA released a study showing that, in warm years, water flowing into the lower Snake River is cool enough for fish, but water flowing out of the lower Snake River is too hot and the dams cause much of this heat pollution.

A reservoir-free lower Snake River flows freely and does not absorb the same amount of solar radiation. Considerably cooler waters deliver big benefits to migrating juvenile and adult salmon and steelhead populations – leading to increased survival and reproductive success. A free-flowing lower Snake River also has the additional benefit of cold waters that are released from behind the Dworshak reservoir upstream on the Clearwater River in the hot summer months.


Dworshak dam’s large reservoir is used to deliver cold water into the Clearwater River, which enters the Snake River at Lewiston, Idaho. The Army Corps has traditionally released the cold water from the Dworshak Dam after July 4th. However this year, on June 22nd, due to the extreme heat wave in the Pacific Northwest, the Army Corps began to release “43-degree Fahrenheit (6-degree Celsius) water at Dworshak Dam” to prevent the water temperature from reaching 68 degrees Fahrenheit and higher at the Lower Granite Dam’s reservoir near Lewiston (ID) and Clarkston (WA).

With the dams in place, the cooling benefits of Dworshak releases are limited to the uppermost reservoir of Lower Granite dam. This year, for example, the Lower Granite reservoir reached 68.36°F (20.2°C) on Friday June 25, 2021 (see table above). The release of cold water from the Dworshak reservoir cooled the Lower Granite reservoir to below the 68°F threshold for three days. Immediately downstream, however, the Little Goose reservoir experienced the highest water temperatures so far this summer - at 73.04°F (22.8°C). Despite the release of cold water from the Dworshak reservoir, the Little Goose Dam and Lower Monumental Dam (immediately downstream from Lower Granite Dam) continued to experience temperatures well above 68°F. As long as these four dams remain in place, the benefits of Dworshak’s cold flows are limited and serve only as a short-term solution to cooling water temperatures to the Lower Granite Dam’s reservoir.

In recent years, the lower Snake River routinely suffers weeks and/or months of hot water with temperatures above – and often well above - 68°F (the upper end of the comfort zone for coldwater fish like salmon and steelhead) - and this year is no exception. However, by restoring this 140-mile stretch of river through dam removal, EPA models used in the Columbia Riverkeeper report show that while temperatures in a freely flowing river may spike above 68 degrees periodically, they will quickly return to the cool temperatures that salmon and steelhead need to survive and thrive. Cold summer flows from Dworshak further help keep temperatures healthy for fish all the way downstream to where the Snake River joins the Columbia River in south-central Washington State near the Tri-Cities.

In summarizing findings of the study, Miles Johnson, senior attorney at Columbia Riverkeeper, notes that, "removing the four lower Snake River dams would keep the river cooler and help salmon reach their spawning areas. This is critical for healthy salmon and a healthy river – especially as the changing climate tightens its grip on our waters in the Northwest. It's time for bold action to protect the Northwest's fishing traditions, orcas, and salmon. It’s time to restore the lower Snake River."

A 2016 court ruling that invalidated the federal government’s latest Columbia-Snake salmon plan as inadequate and illegal highlighted, among other things, the government’s failure to account for the growing impacts of a changing climate on the already endangered wild salmon and steelhead populations of the Snake and Columbia rivers. Unfortunately, the new plan developed during the Trump Administration in response to that court ruling by the federal agencies in charge (Bonneville Power Administration, Army Corps of Engineers, NOAA-Fisheries) still fails to contain any effective strategy to maintain cool, salmon-friendly water temperatures in these reservoirs in summer months. The Trump Plan has been challenged in court by the Nez Perce Tribe, state of Oregon and more than a dozen conservation and fishing organizations (and members of the Save Our wild Salmon Coalition).

1. U.S. Army Corps of Engineers, Final Environmental Impact Statement for Columbia River System Operations, Appendix D, p. A-1-28 (2020).
2. EPA, Columbia and Lower Snake River Temperature TMDL, pp. 47–50 (2020).


  Martha Bio picMartha Campos is the Hot Water Report Coordinator with Save Our wild Salmon this summer while she resides on Kizh/Tongva ancestral lands in California. Martha holds a BA from the University of California, Davis in Native American Studies (and two minors: Environmental Policy, Analysis, and Planning and Climate Science and Policy) and is a queer, non-binary person of color with ancestral roots in Mexico.

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