INTRODUCTION:
The Hot Water Report provides real-time data in the lower Snake and Columbia river reservoirs and details the collective impacts of hot, stagnant, and toxic waters on already-imperiled salmon and steelhead. Discover how you can get involved and support comprehensive solutions to heal the river and recover healthy, abundant salmon and steelhead across the Columbia Basin.
EXECUTIVE SUMMARY:
- The Hot Water Report: Issue 1 dives into how the lower Snake River dams have transformed a healthy, free-flowing river into a series of large, warm, stagnant, toxic reservoirs that harm salmon and steelhead and severely impact their migration, reproductive success, and habitat quality. Read more.
- Breaking News! Action for Cold Water: Washington Department of Ecology is using its Clean Water Act authority to require the Army Corps to study all possible ways to cool the lower Snake River and prevent the dams and reservoirs from heating it to levels that kill endangered salmon. Once again, the Army Corps and Bureau of Reclamation’s proposed plans failed to analyze all potential solutions to the dams’ hot water pollution, also known as heat pollution, and failed to follow other regulatory requirements. Read more.
- Current water temperatures in the lower Snake and Columbia reservoirs: On the lower Snake River, Little Goose Dam’s reservoir registered the highest water temperature of 71.94°F on July 14. On the lower Columbia, The Dalles and John Day dams' reservoir had a highest water temperature of 69.44°F on July 15. View water temperature data here.
Warming waters in the lower Snake and Columbia rivers
Since time immemorial, wild salmon and steelhead from the Snake and Columbia rivers have delivered vast cultural, economic, nutritional, and ecological benefits to the people, fish, and wildlife of the Northwest. Before the construction of the dams, the pristine, clear, cold waters of the Snake River Basin supported millions of spawning adult salmon and steelhead.
Today, salmon and steelhead face dramatically decreased survival rates, largely due to the federal system of dams and reservoirs in the Columbia River Basin. For highly endangered Snake River stocks, the centerpiece action necessary is restoring the lower Snake River via dam breaching. The four lower Snake River dams between Tri-Cities and Lewiston, Idaho—Ice Harbor, Lower Monumental, Little Goose, and Lower Granite—have transformed a healthy and free-flowing river into 140 miles of large, hot, stagnant, toxic reservoirs. As a result, we have a sick river that cannot support healthy and abundant salmon, steelhead, wildlife, and communities.
Due to the dams’ harmful impacts on native fish populations and water quality, the current efforts to preserve the status quo and retain 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. With on-going attacks from the federal government, including weakening the Endangered Species Act, it is imperative to advance regionally supported comprehensive solutions to restore ecosystem health across the basin and recover salmon and steelhead, including by removing the four lower Snake River dams and replacing the dams’ services.
Click the video above (or here) to learn more from Tanya Riordan, Policy and Advocacy Director at Save Our wild Salmon Coalition, on this year’s environmental crisis that is magnifying the already dire river conditions caused by the dams and reservoirs, and the forecast of very low 2026 returns for adult salmon and steelhead.
Army Corps’ draft plan to reduce the water temperatures in the lower Snake reservoirs would continue to violate the Clean Water Act and Washington State rules
By Miles Johnson, Legal Director for Columbia Riverkeeper
Endangered sockeye salmon in Redfish Lake - 900 miles inland and 6500 feet above sea level. © Emily Nuchols
During the summer, water temperatures in the lower Snake and Columbia reservoirs routinely reach lethal levels between 70-72°F, violating standards set under one of our strongest environmental laws — the Clean Water Act. Scientists have identified 68°F as the biological and legal water temperature threshold under the Clean Water Act to protect salmon and steelhead.
The Clean Water Act defines heat as a pollutant, and the states of Oregon and Washington have recognized that the lower Columbia and Snake rivers have too much hot water pollution, also known as heat pollution, and must address this to stop salmon and steelhead extinction.
One tool under the Clean Water Act for reducing heat pollution is called a Water Quality Attainment Plan. These plans should identify and evaluate the structural and operational changes at dams needed to reduce heat pollution and keep the river cool enough for fish. As a condition of their Clean Water Act permits, the Army Corps and the Bureau of Reclamation are required to prepare and submit Water Quality Attainment Plans for the dams on the Columbia and lower Snake rivers. The ultimate goal of these plans is to meet the temperature reduction target for dams created by the EPA, as a result of Columbia Riverkeeper’s litigation.
What just happened: The Washington Department of Ecology (Ecology) rejected—again—the Army Corps and Bureau of Reclamation’s proposed Water Quality Attainment Plans for Columbia and lower Snake river reservoirs. As explained in the letter disapproving the Army Corps’ plan for the lower Snake River dams, the Army Corps’ plan ignored and prematurely eliminated several potential temperature reduction measures. Ecology’s rejection letters identify specific problems for the Army Corps to fix in order to bring these plans into compliance with the law.
Simultaneously, Ecology has committed to conduct a system-wide analysis of temperature, in partnership with EPA and Oregon Department of Environmental Quality. This project will utilize EPA’s computer model and look at ways to operate the dams in a coordinated manner to achieve the best outcomes for temperature and fish. We strongly support this effort to find solutions to the hot water crisis!
How did we get here? A quick timeline:
- 2014: Columbia Riverkeeper sues the Corps for discharging oil and heat pollution into the lower Snake River without Clean Water Act Permits.
- 2015: 96% of adult endangered Snake River sockeye salmon die because of hot water in the lower Snake and Columbia rivers. Major temperature-related fish kills occurred in the summers of 2013, 2021, and 2023.
- 2016: Columbia Riverkeeper and allies sue under the Clean Water Act to require EPA to create a pollution budget (called a Total Maximum Daily Load analysis, or TMDL) for heat pollution in the Columbia and lower Snake rivers.
- 2017: Columbia Riverkeeper uses computer modeling to show that, without the dams, the lower Snake River would be cool enough for salmon to migrate safely.
- 2019: Ninth Circuit Court of Appeals sides with Columbia Riverkeeper and allies, and orders EPA to write a temperature TMDL for the lower Snake and Columbia Rivers.
- 2021: EPA releases a final temperature TMDL for the lower Snake and Columbia rivers. The TMDL identifies the dams and reservoirs as major sources of heat pollution, and sets numeric temperature reduction targets for each dam.
- 2022: As a result of Columbia Riverkeeper’s original suit against the Corps, EPA finally issues Clean Water Act discharge permits for the Corps’ lower Snake River dams. These permits require the Corps to make a plan (called a Water Quality Attainment Plan) to achieve the temperature reductions mandated by the TMDL.
- 2024: Ecology rejects the Army Corps’ first Water Quality Attainment Plan, which proposed no new measures to reduce temperature. Ecology required the Army Corps to produce better Water Quality Attainment Plans, with input from States, Tribes, and the EPA.
- 2026: The Army Corps and Bureau of Reclamation submit new Water Quality Attainment Plans for Columbia and lower Snake river dams. Ecology rejects these plans—again—for failing to analyze all potential solutions to the dams’ heat pollution and follow other regulatory requirements.
What’s next?
The Army Corps and Bureau of Reclamation must keep studying ways to prevent the dams and reservoirs from heating up the lower Snake River to levels that kill endangered salmon. The federal agencies have until September 7, 2026, to develop a plan for revising the plans that Ecology just rejected.
As part of the effort to find system-wide solutions to the temperature problem, the Washington Department of Ecology and the Oregon Department of Environmental Quality are both developing large scale temperature reduction plans that apply to federal dams on the Columbia and lower Snake. Those plans will be released for public comment later this summer or fall; stay tuned for more information about how to make your voice heard and let these states know you support their work to reduce heat pollution from dams to protect cool, clean water!
Thank you!
Thank you to Ecology and the State of Washington for continuing to advocate for abundant salmon and clean, cool water! Important decisions like this require dedication to detail, courage, and vision.
READING THE HOT WATER TEMPERATURE DATA:
Introduction to the water temperature data:
- We track water temperatures in all eight reservoirs on the lower Snake and Columbia rivers to understand the overall water temperature conditions that salmon and steelhead must migrate through to reach their spawning grounds (adults) or the ocean (juveniles).
- 68°F Threshold: The longer and the higher water temperatures rise above 68°F, the greater the harm to the fish, including: migration disruption, increased metabolism, increased vulnerability to disease, suffocation as warm water carries less oxygen, and in the worst case - death.
- Water temperature measurements: The daily average and high water temperature data at the eight reservoirs (also known as forebays) are measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dams. See data sources here.
Highest water temperature: The Little Goose Dam's reservoir had a highest water temperature of 71.94°F on July 14.
Average water temperature: The Little Goose Dam's reservoir had a high average temperature of 69.29°F on July 15.
Highest water temperature: The Dalles and John Day dams' reservoir had a highest water temperature of 69.44°F on July 15.
Average water temperature: The John Day Dam’s reservoir had a high average temperature of 69.08°F on July 15.
DISCUSSION OF DATA:
The lower Snake and Columbia River dams create stagnant reservoirs, which are large, slow-moving pools that absorb enormous amounts of solar energy or heat.1 The reservoirs slow the flow of water, which accumulates heat with very little relief throughout the summer.2
Salmon and steelhead are highly resilient. They can tolerate episodes of warm water, but they also have limits on how long and how much hot water they can withstand. The warming waters in these reservoirs also destroy diverse micro-habitats that healthy rivers support, including cold-water refuges that salmon and steelhead have historically relied upon to rest and recover during their long upstream migration.
The cumulative impact of hot reservoirs in the lower Columbia and the lower Snake must be addressed quickly - to reduce water temperatures and the overall exposure time for these fish to waters above 68°F.
Water temperature ranges that are harmful and lethal to salmon and steelhead:
68°F: Adult and juvenile salmon have difficulty migrating upstream when water temperatures meet and exceed 68°F.3
69°F: As temperatures reach 69°F, salmon become sluggish.4 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.5 Warm water temperature can alter growth and development rates for juvenile salmon.6
70-71°F: Temperatures of 70°F and above are extremely stressful for most species,7 including concurrent thermal stress and energy depletion.8 Harmful fungus begins to grow on salmon.9 Water temperatures of 70°F have been demonstrated to inhibit or stop migrating salmon and steelhead.
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.10
This week, water temperatures are reaching between 68°F - 71°F across the river. Removing the four lower Snake River mainstem dams is key to recovering healthy and abundant salmon and steelhead and restoring salmon's migratory habitat and reconnecting this emblematic fish to 5,500 miles of pristine, protected river and streams in Idaho, Oregon, and Washington.
READ PAST ISSUES OF THE HOT WATER REPORT
The Hot Water Report is a project of: Save Our wild Salmon Coalition, Association of Northwest Steelheaders, Columbia Riverkeeper, Earthjustice, Idaho Conservation League, Idaho Rivers United, National Wildlife Federation, Northwest Sportfishing Industry Association, Orca Network, Pacific Rivers, Sierra Club, and Snake River Waterkeeper.
Data Sources: The 2026 water temperature data for the lower Snake River and lower Columbia River presented in the Hot Water Report are collected from the USGS, and the Columbia River DART program by Columbia Basin Research, University of Washington, with data courtesy of the U.S. Army Corps of Engineers (USACE). These data temperatures are provisional. The 10-year average water temperature data is courtesy of the Fish Passage Center and Columbia River DART program. Water temperature data is provisional. Graphs and tables are assembled by SOS Staff.
Video:
- Six Sovereigns: Fish Facts Columbia Basin Salmon, Steelhead, and Other Native Fish in Crisis
- NPCC, Compilation of Information on Salmon and Steelhead Losses in the Columbia River Basin (March 1986), p.21. This was Appendix D of the 1987 PPCC Fish and Wildlife Program https://www.nwcouncil.org/reports/1987-columbia-river-basin-fishwildlife-program/
- Tribal Circumstances Analysis developed by the Department of Interior, in collaboration and coordination with the Columbia Basin Tribes.
- Seattle Times: What a ‘very strong’ El Niño could mean for WA
- News Tribune: ‘Very strong’ El Niño predicted in 2026. What does it mean for WA weather?
- Department of Ecology: Washington water supply update: El Niño is here and likely to be strong
- Joint Columbia River Management Staff: Stock Status And Fisheries For Spring Chinook, Summer Chinook, Sockeye, Steelhead, And Other Species
- Lewiston Tribune: Snake River sockeye solutions
- Spokesman-Review: Snake River sockeye running behind forecast
Water Temperature discussion:
1, 2, 9, 10. Columbia Riverkeeper White Paper: Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015. U.S. Environmental Protection Agency, Application of a 1-D Heat Budget Model to the Columbia River System, p.1 (2001) (“Construction of impoundments for hydroelectric facilities and navigational locks . . . increase the time waters of the Columbia and Snake are exposed to high summer temperatures . . . .”).
3,4. EPA: Columbia and Lower Snake Rivers Temperature Total Maximum Daily load
5. Poole, G., et al., 2001. Technical Synthesis: Scientific Issues Relating to Temperature Criteria for Salmon, Trout, and Char Native to the Pacific Northwest
6,7,8. A Great Wave Rising: Solutions for Columbia and Snake River Salmon; 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
