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

• This summer, for approximately 60 days, all four reservoirs created by the lower Snake River dams have experienced temperatures exceeding 68°F “harm” threshold. Many of the reservoir waters reached between 70°F and 72°F for several weeks.
• The once free-flowing river has been transformed by the dams and their reservoirs now produce lethal high water temperatures and provide conditions that support toxic algal blooms–further threatening the survival and recovery of salmon and steelhead.
• Wild-origin returns of salmon to the Snake Basin are 0.1-2% of their historical abundance, with many populations at or below a Quasi-Extinction Threshold (QET), which signals adult Snake River salmon abundance are nearing absolute extinction, and the probability of recovery is low without substantial and immediate intervention.
• The science is clear: in its report published in Sept. 2022, NOAA states that restoring Snake River salmon and steelhead to healthy and abundant levels would require restoration of the lower Snake River and its migration corridor by breaching the four lower Snake River dams as part of a comprehensive suite of actions for the Basin.

II. INTRODUCTION

Shine and Flow II © Rachel Teannalach

During the summer, our Hot Water Report provided real-time water temperatures in the lower Snake and Columbia river reservoirs, and reported on the challenges facing these rivers, opportunities to recover healthy, resilient fish populations, and the benefits they deliver to Northwest communities and other fish and wildlife populations.

The final Hot Water Report issue for summer 2024 will review this year’s high water temperatures in the lower Snake and Columbia reservoirs and the number of days each of the reservoirs experienced above the 68°F threshold. Issue 12 will provide a brief update on the Quasi-Extinction Threshold for Spring/summer Chinook salmon and steelhead and the urgency to restore Snake River fish.

The four federal dams and their reservoirs on the lower Snake River are the single largest factor in preventing salmon from migrating safely to the Pacific and returning to spawning grounds to reproduce in viable numbers. Restoring a free-flowing Snake River by removing its four dams and replacing their services is essential to provide cold, clean, healthy water for salmon and steelhead, protect and recover these once-highly prolific fish populations, uphold our nation's promises to Tribes, and help feed the critically endangered Southern Resident orcas and other fish and wildlife species.

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

III. INTRODUCTION TO THE DATA: Highest Water Temperatures in the Lower Snake and Columbia Rivers from July 1 - September 16, 2024.

From April 1 - September 10, 2024, the Hot Water Report reported water temperatures at the four reservoir forebays in the lower Snake River and the lower Columbia River. In the following tables, below, we present a summary of the highest water temperatures in 2024, the date of the highest temperatures, and the number of days each of the reservoirs reached above the 68°F “harm” threshold.

Hot water temperature effects to salmon: Snake River salmon and steelhead experienced another summer of hot, harmful water temperatures in the lower Snake River and the lower Columbia River. The longer and the higher water temperatures rise above 68°F (this threshold is the legal and biological limit scientists identify to protect salmon), the greater the harm to salmon, 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.

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

HIGHEST WATER TEMPERATURES IN THE LOWER SNAKE RIVER: July 1 - September 16, 2024

• Hot water temperatures on the lower Snake River: This summer, for approximately 60 days, all four reservoirs created by the lower Snake River dams have experienced temperatures exceeding 68°F. Many of the reservoir waters reached between 70°F-72°F for several weeks. Depending on salmon species, migration for salmon and steelhead stops altogether when water temperatures reach 72-73°F. Salmon that have stopped or slowed their migration can languish for days or weeks in warm water and die from thermal stress and disease.
• On August 5, 2024, the reservoir behind the Lower Granite Dam registered the highest water temperature recorded this summer – 72.52°F, more than 4 degrees above the 68°F “harm” threshold. The Lower Granite Dam’s reservoir registered above 68°F for 20 days.
• Ice Harbor Dam's reservoir registered the highest water temperature of 72.50°F on August 10 and registered above 68°F for 69 days. 
• Little Goose Dam's reservoir reached the highest water temperature of 71.87°F on July 16, and the reservoir registered above 68°F for 56 days.
• Lower Monumental Dam’s reservoir registered a high water temperature of 71.53°F on July 24, and the reservoir registered above 68°F for 61 days.
• Cool water from Dworshak Reservoir provides cold water to Lower Granite Reservoir: The Lower Granite Reservoir registered above 68°F for 20 days, fewer days compared to the other reservoirs, due to the US Army Corps of Engineers’ cold water release effort from the reservoir behind Dworshak Dam in the Clearwater River, a tributary to the lower Snake River. The goal of this release is to lower water temperatures and aid salmon and steelhead survival, but the benefit of this cold water does not last long in the summer heat and does not cool the other three downstream reservoirs on the lower Snake. According to scientists at the Environmental Protection Agency (USEPA), with a free-flowing lower Snake River, cold water releases from Dworshak Dam during the summer months would further help keep temperatures cool and healthy for fish from Lewiston (ID) downstream to where the Snake River joins the Columbia River in south-central Washington State near the Tri-Cities.

HIGHEST WATER TEMPERATURES IN THE LOWER COLUMBIA RIVER: July 1 - September 16, 2024

• Hot water temperatures on the lower Columbia River: On July 21, 2024, the reservoir behind the John Day Dam registered the highest temperature recorded this summer – 72.68°F over 4 degrees above the 68°F “harm” threshold.
• The water temperatures in the four reservoirs created by dams on the lower Columbia River give us an in-depth look at the lethal conditions and temperatures that many Columbia Basin salmon and steelhead must now migrate through in the summer months. Endangered Snake River fish must traverse a total of eight stagnant reservoirs and their fish ladders/fish passages on their migration to the ocean as juveniles and again on their journey back upstream as adults. For instance, as adults migrate through the lower Columbia River dams, they are faced with hot water temperatures between 68 - 72°F and must continue to migrate through four other hot and stagnant reservoirs in the lower Snake River.

Data collection: The 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. Hourly temperatures are used to find the highest temperatures reached in each reservoir.  Data Sources: Water temperature data 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. Urgency to restore the lower Snake River and to recover its native fish

Free Flowing III 2023, acrylic and graphite on birch panel 24" x 48" x 1.5" © Britt Freda

For millennia, wild Snake and Columbia River salmon and steelhead have delivered vast cultural, economic, nutritional, and ecological benefits to the people, fish, and wildlife of the Northwest. Before the lower Snake River dams were built, the pristine, clear, cold waters of the Snake River Basin were home to millions of adult salmon and steelhead, along with sturgeon, lamprey eel, and other native fishes. Each year, salmon and steelhead return from the Pacific Ocean, swimming against the current in search of their natal spawning gravels and delivering many millions of pounds of high-quality marine-derived nutrients to the landscape and wildlife of the Northwest.

Salmon and steelhead require clean, cold water, and free-flowing rivers for successful migration, spawning, and rearing. However, the once free-flowing river has been transformed by the dams and their reservoirs now produce lethal high water temperatures that significantly reduce access to the cold water, high-quality spawning, and nursery habitat that are essential for fish sustainability.¹ Since the completion of the dams on the lower Snake River, wild Snake River fish returns have plummeted and are far below the levels required to delist them from the Endangered Species Act, much less meet their recovery goals necessary to achieve healthy and abundant levels.

Hot Water Temperatures and Toxic Algal Blooms in the Lower Snake River

Toxic algal blooms in Lower Granite Reservoir on the Snake River.  Photos taken on September 1, 2024.

The lower Snake River dams create stagnant reservoirs, which are large, slow-moving pools that absorb enormous amounts of solar radiation, causing water temperature to reach lethally high levels. The reservoirs warm during the summer months and create a block of slow-moving hot water that retains the heat through the night and does not cool only until air temperatures drop. Fish ladders are the only route past the dams that Snake River salmon and steelhead have to enter. These ladders frequently contain water that is warmer than the average river temperature, and such conditions can create or exacerbate migration blockages, reducing salmon survival.

These warming waters in the lower Snake River reservoir 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 cannot rest and recover on their journeys – adults moving upstream to spawn and juveniles moving downstream to the ocean.

This summer, many of the reservoirs behind the lower Snake River dams reached high temperatures between 71-72°F – above the biological and legal threshold scientists identified to protect salmon from lethal water temperatures. In late July, many Snake River sockeye have been observed this summer seeking refuge from hot water temperatures in the lower Snake River by moving (straying) into the Mid-Columbia River, where water temperatures are cooler.

The lower Snake River dams, their reservoirs, and fish ladders impact fish in many ways, including by elevating water temperatures that destroy and degrade habitat required for salmon and steelhead’s key life stages. For the second consecutive year in a row, the lower Snake River dams’ warming and stagnant reservoirs are providing conditions that support toxic algal blooms.

Since August 16, 2024, Whitman County Public Health has continued to collect toxic algal bloom samples along the lower Snake River. All water samples have tested positive for toxic algae with microcystins, a liver toxin, causing the river to become unsafe and dangerous to people, pets, communities, the environment, and native fish.

Endangered Snake River salmon and steelhead must now attempt to migrate through an increasingly sick lower Snake River, with dangerously high water temperatures and large toxic algal blooms—further threatening their survival and recovery.

Snake River Salmon and Steelhead on the Brink of Extinction

Figure 1. Over half the historical populations are extinct, and none of the existing populations are considered healthy and harvestable. Less than half of the 117 historical populations remain. Source: Nez Perce Department of Fisheries Resources Management.

Salmon runs have plummeted since the signing of the treaties and reservation executive orders that would protect the Tribes’ harvest rights.² Many of the Columbia-Snake River Basin salmon runs have been locally extirpated. Thirteen populations, including all four Snake River populations, are listed as threatened or endangered under the Endangered Species Act and remain at risk of extinction (Figure 1).

Wild-origin returns of salmon to the Snake Basin are 0.1-2% of their historical abundance, with many populations at or below a Quasi-Extinction Threshold (QET)—50 or fewer natural-origin spawners on the spawning grounds for 4 consecutive years.^3,4 Quasi-Extinction Threshold signifies that adult salmon and steelhead abundance in a population are nearing absolute extinction, and the probability of recovery is low without substantial and immediate intervention.

The Nez Perce Department of Fisheries Resources Management released an update on their Snake Basin Chinook and Steelhead Quasi-Extinction Threshold Alarm analysis:

Snake River Spring/Summer Chinook:

• As of the 2023 return, 17% or 6 out of the 35 populations in the Snake River Basin are currently meeting the QET.
• 13 or 37% of these populations below 50 spawners in 2023.
• The Nez Perce Department of Fisheries Resources Management is projecting that nearly 57% of these populations, 20 out of the 35, are predicted to be at or below 50 or fewer natural origin fish before 2028.

Snake River steelhead:

• As of the 2023 return, 19% or 4 out of the 21 populations in the Snake River Basin the QET in four consecutive years of 50 or fewer natural-origin spawners.
• 4 or 19% of these populations below 50 spawners in 2023.
• The Nez Perce Department of Fisheries Resources Management is projecting about 38% or 8 out of the 21 populations are predicted to be at or below 50 or fewer natural origin fish before 2028.

The Snake and Columbia River Basin contains some of the very best available habitat for salmon populations to recover to any significant level of abundance. However, with predictions pushing the populations below 50 spawners, the four lower Snake River dams are a major factor preventing salmon from reaching spawning grounds and reproducing in viable numbers.

Recovering Healthy, Abundant, and Harvestable Salmon and Steelhead Populations

Figure 2. Snake Basin salmon and steelhead current abundance (black dots) relative to historical abundance and Columbia Basin Partnership (CBP) goals; Columbia Basin Partnership high-range goals 5 – 31% of historical. All but one stock is below low-range goals. Fall Chinook salmon are above low-range but below mid-range goals. Source: Nez Perce Department of Fisheries Resources Management.

Over the past several decades, these fish have returned annually far below the recovery goals necessary to remove them from the protections of the Endangered Species Act.

The Columbia Basin Partnership (a diverse group of 31 Columbia Basin stakeholders and sovereigns, including Columbia Basin Tribes; representatives of the four Columbia Basin states (Washington, Oregon, Idaho, and Montana); ports, hydropower interests and public power entities; irrigators; transportation representatives; commercial and recreational fishers and conservationists convened by NOAA) released a set of recovery goals and common vision for the Basin and its salmon and steelhead to ensure that healthy runs of salmon and steelhead thrive into the future. The Partnership unanimously defined “recovery” to mean healthy, abundant, and harvestable naturally reproducing populations of salmon and steelhead, in which naturally produced fish need to meet the recovery goals established by the Partnership (Figure 2) – roughly five times the number needed to lift Endangered Species Act protections.⁵

Despite decades of failed mitigation efforts and many billions of dollars in recovery spending, these fish remain on the edge of extinction. An analysis of the actions necessary to achieve healthy and abundant salmon and steelhead completed by the National Oceanic and Atmospheric Administration (NOAA) Fisheries, Rebuilding Interior Columbia Basin Salmon and Steelhead, reports for Snake River stocks, the centerpiece action is restoring the lower Snake River via dam breaching, along with a comprehensive suite of other actions.

Salmon and steelhead—and endangered Southern Resident orcas and other fish and wildlife that highly depend on salmon—are running out of time. At this moment, we have an urgent opportunity to restore ecosystem health across the Basin and recover salmon and steelhead by removing the four lower Snake River dams and replacing the dams’ services. We must deliver a comprehensive solution to restore a healthy and resilient lower Snake River, protect the Northwest native fish from extinction, and uphold our nation's promises to Tribes by reconnecting this emblematic fish to 5,500 miles of pristine, protected river and streams in Idaho, Oregon, and Washington.

References:
1. American Fisheries Society (AFS) and the Western Division AFS (WDAFS): Statement about the Need to Breach the Four Dams on the Lower Snake River
2, 3. Tribal Circumstances Analysis developed by the Department of Interior, in collaboration and coordination with the Columbia Basin Tribes.
4. Nez Perce Department of Fisheries Resources Management: Snake Basin Chinook and Steelhead Quasi-Extinction Threshold Alarm
5. Trout Unlimited: What does salmon and steelhead “recovery” mean and who decides?

The Hot Water Report is a 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