INTRODUCTION: 
The Hot Water Report provides real-time data in the lower Snake and Columbia river reservoirs to detail the collective impacts of hot, stagnant, and toxic waters on already-imperiled salmon and steelhead. This year’s reports will focus on bringing the data to life, featuring stories from scientists, Tribes, and community members regarding the challenges our Northwest native fish face, and the opportunities to heal their rivers and the ecosystem.

EXECUTIVE SUMMARY:

• Bringing the data to life: Columbia Basin Restoration Initiative (CBRI) webinar and recommended approaches- the comprehensive pathway forward!
• The Hot Water Report: Issue 2 dives into how the lower Snake River dams have transformed a healthy and free-flowing river into a series of large, warm, stagnant, toxic reservoirs that harm salmon and steelhead by severely impacting their migration, reproductive success, and habitat quality
• Hot water temperatures in the lower Snake and Columbia River: Each summer, water temperatures in the lower Snake River routinely reach lethal levels between 70-72°F (and above), significantly above the 68°F legal and biological harm threshold for salmon and steelhead.
• These hot water temperatures threaten the future of salmon and steelhead: The longer these cold water fish must spend in waters 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 dissolved oxygen), and, in the worst case, death.
• Path to recovery: The collaborative implementation of the CBRI represents our region’s greatest opportunity to achieve a healthy, resilient Columbia-Snake River Basin, uphold our nation's promises to Tribes, and reconnect endangered fish in the Snake River Basin to 5,500 miles of pristine, protected rivers and streams in Idaho, Oregon, and Washington. 
• Current lower Snake River water temperatures: The reservoirs behind the Lower Monumental and Little Goose Dams registered the highest water temperature of 72.1 on July 16. Read more on water temperatures in the lower Snake and Columbia rivers here.

Bringing the Data to Life

Before we launch into the hot water data and challenging river conditions salmon and steelhead are facing, we’d like to invite you to watch the webinar we recorded on April 17th, in partnership with Sierra Club featuring representatives of the Six Sovereigns.

In the spirit of bringing the data to life and sharing stories, this presentation provides important background, purpose, and goals of the groundbreaking, collaborative, and comprehensive plan—the Columbia Basin Restoration Initiative (CBRI).

The Northwest’s native fish – and the great gifts they bring – are under unprecedented attack today. Strongly supported laws like the ESA and NEPA are in the crosshairs. Agency staff and funding are being slashed. And in mid-June, the Trump administration issued an order to terminate the Resilient Columbia Basin Agreement (RCBA). The RCBA was a first big step forward to realize the Columbia Basin Restoration Initiative (CBRI) – a holistic strategy to recover Columbia Basin fish and invest in regional communities and infrastructure. It is inclusive and collaborative – a way forward that leaves no one behind. While the current administration may have walked away from the RCBA, the larger CBRI endures and will serve as a North Star to guide our region’s work forward.

We are grateful to the Six Sovereigns — the four lower Columbia River Treaty Tribes (Yakama, Umatilla, Nez Perce, and Warm Springs) and the states of Oregon and Washington — for their leadership to ensure our region is on a pathway to recovery, resilience, and a more just and prosperous future. With the solutions outlined in the CBRI, we can restore salmon and other native fish to healthy and abundant levels, ensure a clean and socially just energy future, support local economic resilience, and honor long-standing federal commitments to Tribal Nations. 

Impacts of hot, toxic, and stagnant water on salmon and steelhead

The Columbian recently reported, “Fish face a ‘triple threat’ in the Columbia River: Rising temperatures, stagnant water and toxic algae”. The article noted the challenges that endangered salmon and steelhead are already facing this summer throughout the Columbia Basin-- as Washington is in a drought, the low snowpack is quickly melting and once-rare toxic algae blooms have started up early this season.

Salmon require cold, clean, oxygenated water to survive and spawn.The dams on the lower Snake River in southeast Washington State—Ice Harbor, Lower Monumental, Little Goose, and Lower Granite—and their stagnant reservoirs heat up this historic, once highly productive river, harming and killing both juvenile and adult fish.

Salmon and steelhead are in hot water — a problem scientists warn us will continue to worsen because of climate change, but we can take action to address this crisis by implementing the CBRI and removing the lower Snake River dams.

• U.S. Environmental Protection Agency estimates that dams on the Columbia and lower Snake Rivers have a cumulative warming impact on the mainstem rivers in the critical late-summer period, and has cited climate change and dams as the main sources of temperature increases above the 68°F (20°C) threshold established by the Clean Water Act.¹
• The lower Columbia and Snake rivers are listed on WA State's polluted waters list for high water temperatures. They routinely exceed the state’s water quality standards in the summer months and harm salmon.
• On the lower Snake River, the four reservoirs have been above the 68°F (20°C) threshold for an average of 15.25 days as of July 23, compared to an average of 13 days above the threshold this time last year. Ice Harbor reservoir has been above 68°F for the longest - at 21 days (compared to 15 days this time last year).

Water temperature ranges suitable, harmful, 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 Studies have also indicated that all Snake River salmon species (sockeye, spring/summer Chinook, fall Chinook, and steelhead) experience reduced survival at elevated water temperatures above 64°F, depending on the timing of their upriver migration.³ 

Impacts of toxic algal blooms on human health, pets, and aquatic life:

When toxic algal blooms form, they usually appear as blue-green scum, foam, froth, or a paint-like slick on the water body’s surface.¹² Under the right set of conditions (including factors like light intensity, nutrient loads, and water temperature and salinity), these cyanobacterial blooms can become toxic, producing byproducts known as cyanotoxins.¹³ Cyanobacteria can produce many cyanotoxins, such as microcystins, which were found on the lower Snake River in 2023 and again in 2024.

Microcystins are very stable and can withstand environmental forces (such as sunlight or temperature variations) without breaking down, which means this toxin can last up to several months under these “favorable” conditions.¹⁴ Microcystins are a group of toxins that can harm the liver and are commonly responsible for human and animal poisonings, and habitat degradation.

• Impacts on human health: Direct exposure to water contaminated by Microcystin (via drinking, swimming, boating, fishing, or other activities that may lead to contact or accidental consumption) can cause these short-term health effects: headache, sore throat, vomiting, nausea, diarrhea, pneumonia, lethargy, skin rash, muscle cramping, and muscle twitching.^15,16 Long-term exposure effects include tumor development, liver failure, and decreased sperm count and motility.¹⁷
• Impacts on domestic animals (primarily dogs): Direct exposure to water contaminated by Microcystin (via drinking, swimming, or licking fur that has been exposed) can cause these health effects in dogs and livestock: vomiting, diarrhea, weakness, pale gums, excessive drooling, paralysis, difficulty breathing, lethargy, skin rash, muscle cramping, muscle twitching, seizures, and sudden death from cyanotoxin poisoning.^18,19
• Impacts associated with habitat degradation caused by algal blooms: Significant increases in algae harm water quality, food resources, and habitats, and decrease the oxygen that fish and other aquatic life need to survive – particularly upon the death of blooms when decomposing algae absorb large quantities of oxygen. This oxygen depletion can lead to injury and death in fish, especially resident species. Algal blooms also block sunlight that submerged aquatic vegetation needed to survive (and produce oxygen via photosynthesis), another way blooms deplete oxygen in freshwater systems.²⁰

Public Health Officials are urging residents to check for potentially harmful algae anytime they are recreating in and along the Columbia River and other waterbodies this summer. Report a sighting of algae or check HERE for news and announcements regarding toxic algal blooms.

Transforming a free flowing river into 140 miles of stagnant reservoirs:

• The lower Snake and Columbia River dams create 140 miles of stagnant reservoirs - large, slow-moving, shallow pools that absorb enormous amounts of solar energy (heat), causing water temperatures to reach harmful levels for migrating salmon and steelhead during the summer months, with very few areas of refuge to escape the dangerous heat.
• Water moves slowly through these reservoirs, which gives more time to accumulate heat and allows reservoirs to retain higher temperatures throughout the day and night. Water temperatures in reservoirs do not cool until air temperatures drop, typically in September. 
• In comparison, a free-flowing river cools down much more quickly as air temperatures drop. 
• Each summer in the lower Snake region, extreme heat warnings, droughts, reduced snowpack, and low river flow conditions all contribute to rising river water temperatures, which are then exacerbated by the dams and their reservoirs to harmful levels for cold water fish such as salmon.

The Columbia Basin Restoration Initiative- “A New Opportunity to Restore Salmon, Honor Treaties, and Invest in the Northwest”

With this continuing crisis in the lower Snake River, and many Columbia-Snake River salmon and steelhead populations facing extinction, the “Six Sovereigns” — Confederated Tribes of the Umatilla Indian Reservation, Confederated Tribes of the Warm Springs Reservation of Oregon, the Confederated Tribes and Bands of the Yakama Nation, Nez Perce Tribe, State of Oregon, and State of Washington — jointly developed in 2023 the Columbia Basin Restoration Initiative (CBRI). It is a comprehensive, science-based, and durable strategy to restore salmon and other native fish populations to healthy and abundant levels, ensure a clean energy future, support local and regional economic and climate resilience, restore ecosystem function, and honor longstanding unmet commitments to Tribal Nations.

In the CBRI, the Six Sovereigns outlined the following recommended approaches, and key pathways to achieve the purpose and stated objectives:

• Ensure that federal hydropower mitigation efforts in the Columbia Basin are directed by joint recommendations of tribal and state fish management entities in coordination with federal fisheries services. 
• Significantly increase funding for restoration to levels sufficient to address identified mitigation needs and obligations and support “healthy and abundant” fisheries recovery goals. Address the significant backlog of authorized and recommended, but historically underfunded, actions necessary for the safe and effective operation of critical fisheries infrastructure, assets, and programs. 
• Replace the benefits of the LSR dams with due urgency to enable breaching to move forward,and ensure interim fish measures are adequate to minimize additional generational decline of fish populations.
• Implement the Upper Columbia United Tribes’ Phase Two Implementation Plan to reintroduce and provide passage of priority anadromous species above Chief Joseph and Grand Coulee dams.
• Establish a long-term biological performance monitoring and reporting program to measure progress and support accountability towards the qualitative and quantitative recovery and abundance goals identified in the CBP Phase II Report.

For more detailed information about the CBRI, please see the Six Sovereigns Slide Deck HERE. 

The continued, collaborative, and focused implementation of the CBRI represents our region’s very best opportunity to achieve a healthy, resilient Columbia-Snake River Basin, uphold our nation's promises to Tribes, and reconnect endangered fish to 5,500 miles of pristine, protected rivers and streams in Idaho, Oregon, and Washington.

The CBRI is the only plan that has been developed to comprehensively address the issues facing salmon, health of our rivers, community needs, and infrastructure. There is NO other plan. Returning to the status quo means extinction, and continued pain, loss, and uncertainty for all affected communities. The CBRI represents an historic opportunity for the people of the Northwest and nation - and we all need to work together to support the Six Sovereigns leadership in collaboration with others in the region to move it forward.

READING THE DATA: LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES:

Introduction to the water temperature data:

• Throughout the summer, the Hot Water Report will provide bi-weekly updates on real-time water temperatures in the lower Snake and Columbia River reservoirs.
• We track water temperatures in all eight reservoirs in the lower Snake and Columbia rivers to understand the river conditions that salmon and steelhead must migrate through.
• The daily average and high water temperature data at the eight reservoir forebays are measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dams.

DISCUSSION OF DATA:

LOWER SNAKE RIVER WATER TEMPERATURES: 7/9 - 7/23

Click here to view the lower Snake River water temperatures - 2025 Daily Average and 10-year Average

Average water temperature: Between July 9 - July 23, the highest daily average temperature across all four lower Snake reservoirs was at Ice Harbor reservoir, averaging 71.38°F.

Highest water temperature: The Lower Monumental and Little Goose reservoirs both registered the highest water temperature of 72.1°F on July 16.

LOWER COLUMBIA RIVER WATER TEMPERATURES: 7/9 - 7/23

Click here to view the lower Snake River water temperatures - 2025 Daily Average and 10-year Average.

Average water temperature: Between July 9 - July 23, the highest daily average temperature was at John Day reservoir, averaging 72.5°F.

Highest Water Temperatures: The John Day reservoir registered the highest water temperature of 73.04°F on July 15.

References: 

1,4. EPA: Columbia and Lower Snake Rivers Temperature Total Maximum Daily load
2,6,8. 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
3. Letter to NW policymakers signed by 55 Fisheries and natural resource scientists.
7. National Wildlife Federation: How Water Temperatures affect salmon
5, 9. Poole, G., et al., 2001. Technical Synthesis: Scientific Issues Relating to Temperature Criteria for Salmon, Trout, and Char Native to the Pacific Northwest
10. Idaho Fisheries Resources Office, U.S. Fish and Wildlife Service, DOI Temperature and handling of adult salmon and steelhead at Bonneville Dam January 24, 2010
11. Columbia Riverkeeper White Paper - Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015.
12,14. Toxic Algae Blooms, Benton-Franklin Health District; webpage accessed on April 25, 2024.
13,15,17. Harmful Algal Blooms (HABs) in Water Bodies, U.S. Environmental Protection Agency; webpage accessed on April 23, 2024.
16,18. Toxic Algal Blooms website by Whitman County Public Health 
19. CDC: For Veterinarians: Harmful Algal Bloom-Associated Illnesses
20. Nutrient Pollution: Dead Zones and Harmful Algal Blooms, U.S. Environmental Protection Agency; webpage accessed on April 28, 2024.

READ PAST ISSUES OF THE HOT WATER REPORT

Data Sources: The 2025 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. There is no data available for the Lower Monumental 10-year average water temperature. Graphs and tables are assembled by SOS Staff.