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: A health advisory from the Idaho Department of Health, “warns residents to avoid contact with water at Brownlee and Hells Canyon reservoirs after detecting dangerous levels of toxin producing algae.”
- Fish Facts: Excerpts from Columbia Snake River Campaign and their webinar presentation with Jay Hesse, Director of Biological Services, Nez Perce Tribe's Department of Fisheries Resources Management—outlining the facts regarding the status of salmon and steelhead across the Columbia/Snake River basin.
- Historical Abundance: The Columbia/Snake River Basin was once the most productive Chinook Habitat in the world.
- Recovery Goals: In 1987, the Northwest Power and Conservation Council set a goal of 5 million salmon returning annually to the Columbia Basin by 2025. Today, we’re at about 2.3 million—of which about 80% are hatchery fish.
- Status of Endangered and threatened species: Four of 16 historical Snake River stocks are extinct. Seven are listed as endangered or threatened under the Endangered Species Act (ESA). Of these, not a single stock currently meets the abundance criteria for ESA delisting—let alone meets the goals for healthy and harvestable.
- Impacts: The impact of the lower Snake River dams is undeniable. Juvenile salmon now take 10–30 days to migrate from Lewiston to the ocean, compared to 2–4 days historically—dramatically increasing their exposure to predators, warm water, and water quality events like toxic algae. These four dams alone inundate 140 miles of critical river habitat.
- Current lower Snake River water temperatures: The reservoir behind the Ice Harbor Dam registered the highest water temperature of 72.14°F on August 5 and August 6.
- Average days above 68°F (20°C): The four lower Snake reservoirs have been above the 68°F threshold for an average of 30.25 days, compared to 25.5 days this time last year.
- Total consecutive days above 70°F (21°C) in the lower Snake River: Ice Harbor reservoir’s daily average has been above 70°F for 24 consecutive days. Lower Monumental’s daily average has been above 70°F for 11 consecutive days.
- Longest amount of days above 68°F in all eight Columbia Basin reservoirs: Ice Harbor reservoir has been above 68°F for the longest - at 36 days, compared to 29 days this time last year.
- Total consecutive days above 68°F in all eight Columbia Basin reservoirs: All reservoirs have been above the 68°F threshold for 22 consecutive days.
- Read more on water temperatures in the lower Snake and Columbia rivers here.
In the Hot Water Report Issue 2, we documented the harm caused by toxic algal blooms occurring across the Columbia/Snake River Basin. Unfortunately, our featured story for issue 3 is the recent health advisory from the Idaho Department of Health, “warning residents to avoid contact with water at Brownlee and Hells Canyon reservoirs after detecting dangerous levels of toxin producing algae.”
“The Idaho Department of Health and Welfare announced the precautionary measure following laboratory tests that revealed elevated concentrations of cyanobacteria in both Snake River reservoirs. The microscopic organisms produce cyanotoxins that pose serious health risks to humans, pets and livestock.”
Read more here: KTVB: Idaho issues health advisory for Snake River Reservoirs due to toxic algae | ktvb.com
The news of the toxic algal blooms comes just weeks before the fall chinook fishing season opens on August 18th across the Columbia/Snake River.
While fishing remains permitted, the toxic algae bloom poses significant risks to fishing activities. Fish caught in waters affected by the bloom should be cleaned thoroughly in uncontaminated water before consumption. Boiling or standard filtration methods do not eliminate toxins, and the risk of liver damage and other health issues remains. Anglers are advised to follow strict preparation guidelines to ensure safety, including cleaning fish in uncontaminated water, removing all fat, skin, and internal organs before cooking, as toxins accumulate in these tissues.
Save Our wild Salmon and partners will closely monitor the status and impacts to the upcoming fall chinook fishery, which Tribes, rural communities, recreational guides, and anglers depend on as a significant economic and cultural resource.
Columbia/Snake River Basin Fish Facts:
On June 27, 2025, the Columbia Snake River Campaign published a webinar presentation with Jay Hesse, Director of Biological Services, Nez Perce Tribe's Department of Fisheries Resources Management—outlining the facts regarding the status of salmon and steelhead across the Columbia/Snake River basin.
All of the following information represents excerpts from the Columbia Snake River Campaign webinar, and presentation materials. Please watch the full webinar for additional details.1
Historical Abundance:
Recovery Goals:
We are far from recovery goals. In 1987, the Northwest Power and Conservation Council set a goal of 5 million salmon returning annually to the Columbia Basin by 2025. Today, we’re only at about 2.3 million—of which 80% are hatchery fish.
In 2020, the Columbia Basin Partnership Phase 2 Report established nonpartisan, collaborative, science-based low-, mid-, and high-level abundance levels for each Columbia Basin salmon and steelhead stock.
The following infographic explains the dangerously low recovery status of imperiled wild salmon and steelhead stocks based on the established Columbia Basin Partnership goals.
Status of Endangered and Threatened Species:
Four of the 16 historical Columbia Basin stocks are extinct. Seven are listed as endangered or threatened under the Endangered Species Act (ESA), and four others are also well below the historic abundance. Of these, not a single stock currently meets the abundance criteria for ESA delisting—let alone meets the goals for healthy and harvestable.
Only one of the wild salmon and steelhead stocks that return to the Columbia Basin above Bonneville Dam, (Mid-Columbia River Summer/Fall Chinook), is anywhere near its historical abundance.
Over 24% of Snake River spring/summer Chinook populations had fewer than 50 fish in 2024—a warning sign of functional extinction. The prognosis for 2025 is nearly identical.
Source: Rebuilding Interior Columbia Basin Salmon and Steelhead, NOAA 2022 (Table 2).
“The fish are anything but healthy.” Despite ads claiming that salmon returns have “tripled” since dam construction, Jay Hesse cautioned that those figures rely on hatchery returns and obscure the full collapse of wild stocks.
Impacts:
The impact of the lower Snake River dams is undeniable. Juvenile salmon now take 10–30 days to migrate from Lewiston to the ocean, compared to 2–4 days historically—dramatically increasing their exposure to predators, warm water, and water quality events like toxic algae. These four dams alone inundate 140 miles of critical river habitat.
Ecological and cultural collapse is at stake. This is not just about fish—it’s about tribal rights and identity, iconic wildlife like Southern Resident orcas, the Northwest’s recreational and fishing economy, and a collapsing nutrient cycle once sustained by millions of salmon. These are irreplaceable life sources balanced against the demand for energy, irrigation, and transportation dam services – all of which can be replaced.
References:
Columbia Snake River Campaign Fish Facts Briefing. https://www.youtube.com/watch?v=n04tNaWrByk
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: 7/24 - 8/7
Average water temperature:
- Between July 24 - August 6, the highest daily average temperature across all four lower Snake reservoirs was at Ice Harbor reservoir, averaging 71.90°F.
- Ice Harbor reservoir’s daily average has been above 70°F (21°C) for 24 consecutive days. Lower Monumental’s daily average has been above 70°F for 11 consecutive days.
Highest water temperature: Ice Harbor reservoir registered the highest water temperature of 72.14°F on August 5 and 6.
Total days above 68°F in the lower Snake River:
- Ice Harbor reservoir has been above 68°F for the longest - at 36 days, compared to 29 days this time last year.
- The four lower Snake reservoirs have been above the 68°F (20°C) threshold for an average of 30.25 days, compared to 25.5 days this time last year.
LOWER COLUMBIA RIVER WATER TEMPERATURES: 7/24 - 8/7
Average water temperature: Between July 24 - August 4, the highest daily average temperature was at the Dalles reservoir, averaging 72.50°F.
Highest water temperature: The Dalles reservoir registered the highest water temperature of 72.86°F on July 30.
Total days above 68°F in all eight Columbia Basin: All reservoirs have been above the 68°F (20°C) threshold for 22 consecutive days.
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.
