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Save Our Wild Salmon

HWR Banner sockeye salmon with lesions image by Conrad GowellSockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin ©Conrad Gowell


Welcome to the 2023 Hot Water Report: Warming Waters in the lower Snake and Columbia rivers.

During the summer, this weekly report provides an update on real-time water temperatures in the lower Snake and Columbia river reservoirs via graphs and analyses, a summary of the highest weekly water temperatures at the forebay/reservoir of each dam, and a monthly status of adult returns for different salmon and steelhead populations as they make their way back to their natal spawning grounds. We’ll report first-hand from scientists, Tribal members, fishing guides, advocates, and other experts about the challenges facing these rivers - and our opportunities to improve and restore them - in order to recover healthy, resilient fish populations and the benefits they deliver to Northwest communities, other fish and wildlife populations (including the critically endangered Southern Resident orca), and ecosystems.

The once-abundant anadromous fish populations of 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 Columbia-Snake federal hydro-system harms and kills both juvenile and adult fish in multiple ways, including by elevating water temperatures in the summer months in their large, stagnant reservoirs. These cold-water fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit.

This July marked the first time in 2023 the lower Snake and Columbia river reservoirs surpassed the 68°F “harm” threshold for salmon and steelhead, and now salmon are migrating through dangerous and lethal water temperatures. In Issue 2, we’ll review the water temperatures suitable for juvenile and adult salmon as well as lethal, and the urgent need to restore a freely flowing lower Snake River to provide cold, clean, and healthy waters for salmon and steelhead.

A restored, healthy, and resilient lower Snake River is a necessary step in order to uphold our nation's promises to Tribes and sustain salmon populations in perpetuity. Dam removal will reconnect the Northwest’s emblematic fish to over 5,500 miles of pristine, cold-water river and streams in Idaho, Oregon, and Washington.

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Association 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.

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

Figure 1. Lower Snake River Water Temperatures - 2023 Daily Average and 10-year Average. Click on the image to view the graph.

Introduction to the data:

The daily average temperature at the four reservoir forebays (immediately upstream from the dam) in the lower Snake River (above) and the lower Columbia River (below) for 2023 is represented with solid lines and the 10-year average (2013 - 2023) 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.

The longer and the higher these temperatures rise above 68°F, the greater the harm, including: migration disruption, increased metabolism, increased susceptibility to disease, reduced reproductive potential (by reducing egg viability), suffocation (warm water carries less oxygen), and in the worst case - death.

Reservoirs are large, slow-moving pools that absorb enormous amounts of solar radiation, causing waters 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 summer migrations. Without these vital pockets of cold water, salmonids struggle to rest and recover on their journeys – adults moving upstream to spawn and juveniles moving downstream to the ocean. Rising temperatures and reductions in snowpack in recent decades due to climate change create warmer waters, which results in lower survival and reduced reproductive success for salmon and steelhead. The lower Snake River dams and their reservoirs exacerbate these already-warmed waters, creating conditions that harm these fish.

LCR July 11Figure 2. Lower Columbia River Water Temperatures - 2023 Daily Average and 10-year Average. Click on the image to view the graph.

Discussion of data:

Since April, temperatures in the lower Snake River and the lower Columbia River reservoirs have steadily increased. Water temperatures in June this year were considerably higher than 10-year average. As Figure 1 shows, this week, the reservoir behind the Ice Harbor Dam had the highest recorded average temperature of 69.45°F on July 11. The Little Goose reservoir had the second highest recorded average temperature of 69.42°F on July 8.

As Figure 2 shows, the reservoir behind the John Day dam on the lower Columbia River had the highest recorded average temperature of 70.34°F on July 6. Both juvenile and adult salmon are now experiencing water temperatures 1- 2 degrees above the 68°F “harm” threshold.

Last week, on the lower Snake River, the reservoir behind the Lower Granite Dam had the highest recorded average temperature of 68.63°F on July 5. This week, however, the pool behind Lower Granite Dam fell to an average temperature of 65.71°F on July 11. This significant decrease in temperatures is the result of the US Army Corps of Engineers’ annual summer release of cold waters from the Dworshak reservoir into the Clearwater River, a tributary to the lower Snake River. The goal of this release is to lower water temperatures and aid salmon migration, but the benefit of this cold water does not last long in the heat of the summer and does not cool the other three downstream reservoirs. With a free-flowing lower Snake River, the additional benefit of cold waters released from the Dworshak reservoir will extenddown the lower Snake River to its confluence with the Columbia River.

Below, we present the highest temperatures for each reservoir on the lower Snake and Columbia rivers for July 6 - July 11.

A note on the data: The 2023 lower Snake River and lower Columbia River water temperature data presented in the Hot Water Report are collected from the Columbia River DART program by Columbia Basin Research, University of Washington, using data courtesy of the U.S. Army Corps of Engineers (USACE). The 10-year average water temperature data is courtesy of the Fish Passage Center. There is no data available for the Lower Monumental 10-year average water temperature, and McNary reservoir water temperature data is collected from USACE with current available data. Graphs and tables were assembled by SOS Staff.


On the lower Snake River, the reservoir behind the Ice Harbor reservoir registered the highest water temperature at 70.02°F on July 11, and the Little Goose Dam registered the second highest temperature at 69.98°F on July 8.

LCR July 11 high temps On the lower Columbia River, the John Day reservoir registered the highest water temperature at 71.24°F on July 6.

IV. Salmon and Steelhead are in Hot Water

Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin ©Conrad Gowell, July 2021

This July marked the first time in 2023 the lower Snake and Columbia river reservoirs surpassed the 68°F “harm” threshold for salmon and steelhead. This week, the Ice Harbor reservoir registered the highest water temperature at 70.02°F on July 11, and the John Day reservoir reached 71.24°F on July 6 – both temperatures significantly exceed the legal (and biological) limit of 68°F, which scientists have identified as critical for protecting salmon. Salmon and steelhead are now in hot water.

Hot Water Temperatures and Their Impact on Salmon

Dead sockeye hangs upside down in Columbia River.CreditCredit Columbia RiverkeeperDead sockeye hangs upside down in Columbia River. ©Conrad Gowell, July 2021

Salmon require cold, clean water and freshwater habitat to thrive and complete their ancestral migration. The once free-flowing river has been transformed into reservoirs that produce lethal high water temperatures and significantly reduce access to the cold-water, high-quality spawning, and nursery habitat that are essential for fish sustainability.1

Below is a brief list of temperature ranges suitable and lethal to salmon and steelhead:

  • Although varying by species, life stage, and season, the optimal range for juvenile and adult salmon in this region is 55-64°F.2
  • 68°F: Adult salmon have difficulty migrating upstream when water temperatures approach 68°F.
  • 69°F: As temperatures reach 69°F, salmon become sluggish.3 An increase of even a few degrees above the optimum range can change migration timing, reduce growth rates, reduce available oxygen, and increase susceptibility to parasites, predators, and disease.4 Warm water temperature can alter growth and development rates for juvenile salmon.5
  • 70°F: Stream temperatures of 70°F and above are extremely stressful for most species,6 stress including concurrent thermal stress and energy depletion.7 As of July 2023, water temperatures are reaching between 68 - 71°F.
  • 72-73°F: Migration stops altogether when water temperatures reach 72-73°F. Salmon that have stopped or slowed their migration, and languish for days or weeks in warm water, begin dying from thermal stress and disease.8
  • 77°F and above: If salmon are exposed to water above 77°F for more than 24 hours, they will die.9

Restoring the lower Snake River by removing its four federal dams is an essential cornerstone for any credible regional salmon recovery strategy. Up to 70 percent of total out-migrating smolts are killed each year before they reach the ocean as a result of dam encounters, hot stagnant reservoirs, predation, and extended travel time.10 A letter signed by 68 national and Northwest scientists stated, “These four dams must be removed not only to avoid extinction of Snake River fish, but, because these dams block the gateway to high quality, resilient spawning habitat in a world facing increasing impacts of climate change, their removal is essential to restore abundant, harvestable salmon,... and honor the nation’s promises to Northwest Tribes.”11

Salmon need cold, clean water

Salmon Neil Ever Osborne Scientists state excessively high water temperatures above 68°F, are now normal for extended periods in July, August, and September in the lower Snake River. In the summer of 2015, 96 percent of the returning adult Snake River sockeye salmon run died prematurely (pre-spawn) in the lower Snake and Columbia rivers because the reservoirs, coupled with record air temperature and low flows, caused the water to become too warm.12 In early July 2021, video footage showed heat-stressed sockeye salmon with large, open lesions and fungus returning to the Columbia and Snake rivers in waters exceeding 71°F, leading Oregon and Washington to order drastic emergency fishing closures. Scientists predict this year will be another summer of lethally hot water conditions for endangered salmon and steelhead.

“The Snake basin contains the largest area of high-quality Pacific salmon and steelhead habitat left in the lower 48 states. This habitat is increasingly important for them as climate change proceeds, providing a haven of cold waters and the habitat integrity and complexity they need to build and maintain healthy, resilient populations. And yet, even here in the best of the best habitat remaining, the impact of the dams on our salmon and steelhead is unquestionable. Downstream, salmon and steelhead populations on the John Day Rivers and Yakima Rivers must cross three and four dams, respectively. These populations are returning at sustainable rates, nearly four times as high as salmon and steelhead in the Snake basin, which must cross 8 dams and are reaching critical thresholds of risk.”

Helen Neville, Senior Scientist, Trout Unlimited13

In a published report by Columbia Riverkeeper – ‘Columbia Riverkeeper White Paper: Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015’ – confirmed, through computer modeling, “A cooler, free-flowing Lower Snake River could provide refuge for endangered sockeye and other salmon that survive the first part of their difficult journey—rather than forcing these fish to migrate through another 140 miles of hot, stagnant reservoirs. A free-flowing lower Snake River would create opportunities and flexibility, both for migrating salmon and for the state, federal, and tribal governments working to recover these iconic fish.”14

The American Fisheries Society (AFS) and the Western Division AFS, in a statement, affirmed that “breaching the four lower Snake River dams would provide greater certainty of achieving long-term survival and restore riverine habitats in the lower Snake River that will also benefit ecosystem processes, entire biological communities, and increase climate change resilience of anadromous fishes.15

The science is clear: salmon are headed to extinction unless we remove the four lower Snake River dams and replace the dams' services. Salmon and steelhead desperately need a cold free-flowing lower Snake River to ensure resilient and abundant salmon and steelhead populations for generations to come.

View the Hot Water Report Issue 1 and past issues here: Hot Water Reports - Compiled

1, 15. Statement of the American Fisheries Society (AFS) and the Western Division AFS (WDAFS) About the Need to Breach the Four Dams on the Lower Snake River
2, 4, 6. A Great Wave Rising: Solutions for Columbia and Snake River Salmon and McCullough, D.A., 1999. “A Review and Synthesis of Effects of Alterations to the Water Temperature Regime on Freshwater Life Stages of Salmonids, With Special Reference to Chinook Salmon.” Region 10 Water Resources Assessment Report No. 910-R-99-010
3. National Wildlife Federation: How Water Temperatures affect salmon
5, 7. Poole, G., et al., 2001. Technical Synthesis: Scientific Issues Relating to Temperature Criteria for Salmon, Trout, and Char Native to the Pacific Northwest
8, 12, 14. Columbia Riverkeeper White Paper - Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015.
9. Columbia River Inter-Tribal Fish Commission: Climate Change
10. Save Our wild Salmon Press Release: Congressional field hearing ignores the urgency for protecting salmon from extinction and opportunity to invest in Northwest communities and infrastructure
11. Scientists’ letter on the need for lower Snake River dam removal to protect salmon and steelhead from extinction and restore abundant, fishable populations.
13. Spokesman-Review: Helen Neville: The need to breach the Lower Snake River dams: A look at 2022 fish returns 

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