Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin © Conrad Gowell
Welcome to the Hot Water Report 2024: Warming Waters in the Lower Snake and Columbia Rivers.

I. EXECUTIVE SUMMARY

• All four lower Snake River reservoirs exceed the legal and biological limit of 68°F, which scientists have identified as critical for protecting salmon. The reservoir behind the Little Goose Dam registered the highest water temperature of 71.87°F on July 16, and the Ice Harbor Dam reservoir registered the second highest water temperature of 71.46°F on July 17.
• The longer salmon must swim through 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.
• Due to current heat stress and lethal reservoir heating, the Idaho Fish and Game Department is implementing an emergency program and rescue effort for Snake River Sockeye by capturing adults at Lower Granite Dam and trucking them to the Eagle Fish Hatchery near Boise ID.
• Scientists have consistently reaffirmed that the four lower Snake River dams must be removed to avoid the extinction of Snake River fish, restore them to abundant and harvestable levels, and provide new access for them to high-quality, resilient spawning habitat in a world experiencing worsening impacts of climate change. 

II. INTRODUCTION

Final Act © Amy GulickSnake River salmon today are migrating through dangerous and lethal water temperatures. This week, all four lower Snake River reservoirs have registered high temperatures above the 68°F “harm threshold". The reservoir behind the Little Goose Dam registered the highest water temperature of 71.87°F on July 16, and the Ice Harbor Dam reservoir registered the second highest water temperature of 71.46°F on July 17–both temperatures significantly exceed the legal (and biological) limit of 68°F, which scientists have identified as critical for protecting salmon.

In Issue 4, we’ll review different water temperatures and their effects on juvenile and adult salmon, and we'll reflect on the importance of restoring a free-flowing lower Snake River to provide cold, clean, and healthy waters for salmon and steelhead.

A restored, healthy, and resilient lower Snake River is an essential step to uphold our nation’s promises to Tribes - as it is necessary to sustain and rebuild healthy salmon populations for future generations by providing a cold, free-flowing river.

During the summer, the Hot Water Report will provide real-time water temperatures in the lower Snake and Columbia river reservoirs, with updates and reports from scientists, Tribal members, fishing guides, and other experts about the challenges facing these rivers, our opportunities to recover healthy, resilient fish populations, and the benefits they deliver to Northwest communities and other fish and wildlife populations.

View the Hot Water Report issues at wildsalmon.org/HWR

III. READING THE DATA - LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES

INTRODUCTION TO THE WATER TEMPERATURE DATA:

• Throughout this summer, the Hot Water Report will provide, on a weekly basis, an update on real-time water temperatures in the lower Snake and Columbia River reservoirs.
• The daily average and high water temperature data at the four reservoir forebays are measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dams in the lower Snake River and the lower Columbia River for 2024. The water temperatures are taken on the hour. Hourly temperatures are used to find the highest temperatures reached in each reservoir, and hourly temperature measurements are used to find the daily average temperatures.
• Average Water Temperature Graphs (below): Daily average temperatures are represented with solid lines, and the 10-year average (2014 - 2023) temperatures are with dashed lines of the same color. The dotted line across the graph represents the 68°F “harm threshold” for adult and juvenile fish.
• Weekly High Water Temperature Tables (below): This table outlines the highest water temperatures reported for each reservoir during the week and how many days water temperatures have exceeded 68°F.
• 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 worst case - death.

IV. DISCUSSION OF DATA - LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES 

LOWER SNAKE RIVER AVERAGE TEMPERATURES: 7/11 - 7/17
Lower Snake River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir.

• Lower Snake River Water Temperatures: this week, the reservoir behind the Ice Harbor Dam reached a high average water temperature of 71.15°F on July 17, exceeding its 10-year average of 70°F.
• The Lower Monumental reservoir reached an average temperature of 70.08°F on July 16. The Little Goose Dam reached an average water temperature of 70.08°F on July 17 and has reached over its 10-year average of 68.20°F.
• Lower Granite reservoir reached 68.34°F, above its 10-year average of 66.70. In the past weeks, the average temperatures in the Lower Granite reservoir stayed between 67- 68°F due to the US Army Corps of Engineers releasing cold water of 41-42°F from the Dworshak Reservoir; the Lower Granite reservoir’s hourly water temperature data reported a high temperature of 68.09°F on July 14 and 68.24°F on July 17.

WEEKLY HIGH TEMPERATURES IN THE LOWER SNAKE RIVER: 7/11 - 7/17

• This week, on the lower Snake River, all four reservoirs have registered high temperatures above the 68°F “harm” threshold. Little Goose Dam reservoir registered the highest water temperature of 71.87°F on July 16.
• The reservoir behind the Ice Harbor Dam registered the second highest water temperature of 71.46°F on July 17. Lower Monumental Dam reservoir registered the highest water temperature of 70.63°F on July 16.
• This week, Lower Granite Dam reached a high water temperature of 68.85°F on July 17. In previous weeks, Lower Granite Dam registered water temperatures from 66-67°F due to the Army Corps releasing cooler water from Dworshak Reservoir.

LOWER COLUMBIA RIVER AVERAGE TEMPERATURES: 7/11 - 7/17

Lower Columbia River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir.
Lower Columbia River Water Temperatures - 2024 Daily Average and 10-year Average.

• Lower Columbia River Water Temperatures: this week, all four reservoirs on the lower Columbia River reached water temperatures above the 68°F “harm threshold." 
• This week, the John Day Dam reservoir reached a high average temperature of 70.88°F on July 17, exceeding its 10-year average temperature of 69.40°F.
• The reservoir behind the Bonneville Dam and The Dalles Dam had a high average temperature of 70.34°F on July 16 and July 17, exceeding its 10-year average temperature of 69.30 - 69.40°F. The reservoir behind the McNary Dam reached an average temperature of 69.98°F on July 17.

WEEKLY HIGH TEMPERATURES IN THE LOWER COLUMBIA RIVER: 7/11 - 7/17

• On the lower Columbia River, the John Day Dam reservoir registered the highest water temperature at 71.24°F on July 17. The lower Columbia River water temperatures exceeding 68°F imperil salmon and steelhead as they migrate through the stagnant reservoirs created by federal dams to reach the ocean and again on their journey back upstream as adults.

Data Sources: The 2024 lower Snake River and lower Columbia River water temperature data presented in the Hot Water Report are collected from the USGS, 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. Lower Monumental 10-year average water temperatures are unavailable. Graphs and tables are assembled by SOS Staff.

V. Salmon and Steelhead are in Hot Water

Lower Snake River Dam © EcoFlight

All eight lower Snake and Columbia River reservoirs have surpassed the 68°F “harm threshold" for salmon and steelhead. The reservoir behind Little Goose Dam registered the highest water temperature of 71.87°F on July 16, and the Ice Harbor Dam reservoir registered the second highest water temperature of 71.46°F on July 17—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 in hot water.

Hot Water Temperatures and Their Impact on Salmon

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

Reservoirs are large, slow-moving pools that absorb enormous amounts of solar radiation, causing waters to warm. The reservoirs warm during the summer months and create a block of hot water that retains its heat through the night until fall air temperatures drop. These hot 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.

The lower Snake River dams and their reservoirs create hot waters, which results in lower survival and reduced reproductive success for salmon and steelhead. Rising temperatures and reductions in snowpack in recent decades due to climate change exacerbate these warming waters, worsening the conditions that further harm these fish.

The longer and higher water temperatures rise above 68°F, the greater the harm to salmon and steelhead, 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.

For Snake River stocks, the centerpiece action is restoring the lower Snake River via dam breaching.

Breaching will reduce hydrosystem-caused mortality by decreasing travel time for juvenile fish to reach the Pacific Ocean, reducing fish/powerhouse encounters, reducing stress on juvenile fish associated with the hydrosystem that contributes to delayed mortality after reaching the ocean. By restoring the river, dam removal will provide 140 miles of historic rearing and spawning habitat.– National Oceanographic and Atmospheric Administration

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

Below is a brief list of water 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 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
• 68°F: Adult salmon have difficulty migrating upstream when water temperatures approach 68°F.⁴
• 69°F: As temperatures reach 69°F, salmon become sluggish.⁵ 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.⁶ Warm water temperature can alter growth and development rates for juvenile salmon.⁷
• 70-71°F: Stream temperatures of 70°F and above are extremely stressful for most species,⁸ stress including concurrent thermal stress and energy depletion.⁹ Water temperatures of 70°F have been demonstrated to inhibit or stop migrating salmon and steelhead.¹⁰ As of July 2024, 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.¹¹
• 77°F and above: If salmon are exposed to water above 77°F for more than 24 hours, they will die.¹²

Devastatingly low salmon and steelhead returns because of hot water temperatures

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. Major temperature-related fish deaths are occurring frequently during the summer months. 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, energy depletion and extended travel time.¹³

• 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.¹⁴
• In early July 2021, video footage shows heat-stressed sockeye salmon with large, open lesions and fungus returning to the Columbia and Snake rivers with temperatures exceeding 71°F, leading Oregon and Washington to order drastic emergency fishing closures. Only 4 wild/natural Snake River sockeye survived the hot water temperatures in the lower Snake and Columbia River and reached their spawning grounds in Sawtooth Valley lakes, Stanley basin in central Idaho.
• For 2023, the Washington and Oregon Departments of Fish and Wildlife officially estimated that 1,999 endangered Snake River Sockeye entered the Columbia River. But only 174 of those Sockeye actually reached the Sawtooth Valley lakes, and only 31 of those were wild/naturally-spawned. In other words, 91% of endangered Snake River Sockeye entering the Columbia last year died before reaching the Sawtooth lakes, which are the only place on earth that Snake River Sockeye spawn, more than 850 miles from the ocean and 6000 feet above sea level. Heat stress, particularly in 320 miles of unbroken dam-and-reservoir on the lower Columbia and lower Snake Rivers, is the main cause of this extremely high mortality.

This summer, Snake River salmon and steelhead have been migrating through the lower Columbia and Snake rivers with temperatures between 68°F - 71°F. Due to heat stress and lethal reservoir heating, the Idaho Fish and Game Department decided to implement an emergency rescue effort for Snake River sockeye by capturing adults at Lower Granite Dam and trucking them to the Eagle Fish Hatchery near Boise, ID.

Over $24 billion have been invested in salmon recovery programs in the Columbia/Snake Basin, including mitigation efforts such as removing the fish from the river and transporting them by truck and barge. However, according to scientists, the only permanent solution to protect Snake River salmon and steelhead from extinction: restore the lower Snake River by removing its four dams. This is more urgent now than ever before as the frequency, magnitude, and duration of elevated high water temperature events in the river have increased with climate change and are exacerbated by the dams in the Columbia-Snake River Basin.

Despite spending billions on ineffective recovery efforts, these species continue to decline, harming both aquatic and terrestrial ecosystems, other species, tribal rights, and commercial and recreational fishing communities.

Scientific studies consistently demonstrate that breaching the four lower Snake River dams will provide greater certainty of achieving long-term survival and recovery of native wild fishes more than any other measure or combination of measures without dam breaching. Breaching the dams to restore riverine habitats in the lower Snake River will also benefit ecosystem processes, entire biological communities, and increase climate change resilience of anadromous fishes. – American Fisheries Society (AFS) and the Western Division AFS

Salmon need cold, clean water

Salmon will continue to decline toward extinction unless we restore the lower Snake River by removing its dams and replacing their services. Salmon and steelhead desperately need a cold, free-flowing lower Snake River to ensure resilient and abundant salmon and steelhead populations thrive for future generations.

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’ – confirms through computer modeling that a free-flowing lower Snake River would not absorb the same amount of solar radiation. The cooler waters of a free-flowing river would deliver benefits to migrating juvenile and adult salmon and steelhead populations—leading to increased survival and reproductive success.¹⁵ Another computer model from the Environmental Protection Agency shows that removing the four lower Snake River dams would reduce Snake River water temperatures by 6.3 degrees F, on average, during the summer and early fall.¹⁶

The science is clear: the four lower Snake River dams must be removed to avoid extinction of Snake River fish and restore them to abundant, harvestable levels; provide access to high quality, resilient spawning habitat in a world enduring worsening impacts of climate change; and honor our nation’s promises to Northwest Tribes.¹⁷

Restoring the lower Snake River by removing its four federal dams is an essential cornerstone for any credible regional salmon recovery strategy.

References:
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, 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.
4. EPA: Columbia and Lower Snake Rivers Temperature Total Maximum Daily load
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, 14, 15, 16. Columbia Riverkeeper White Paper - Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015.
12. Columbia River Inter-Tribal Fish Commission: Climate Change
13. 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
17. Scientists’ letter on the need for lower Snake River dam removal to protect salmon and steelhead from extinction and restore abundant, fishable populations.

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Association of Northwest Steelheaders, Columbia Riverkeeper, Earthjustice, Endangered Species Coalition, Idaho Conservation League, Idaho Rivers United, National Wildlife Federation, Natural Resources Defense Council, Northwest Sportfishing Industry Association, Orca Network, Sierra Club, Snake River Waterkeeper, and Wild Steelhead Coalition.

View previous Hot Water Report issues at wildsalmon.org/HWR