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

I. INTRODUCTION

Welcome to the 2023 Hot Water Report: Warming Waters in the Lower Snake and Columbia Rivers, our final issue for this summer.

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. Prior to the construction of the lower Snake River dams, the pristine, clear, cold waters of the Snake River Basin were home to millions of adult salmon and steelhead. Each year, they would return from the Pacific Ocean, swimming against the current in search of their natal spawning gravels, and deliver many millions of pounds of high-quality marine-derived nutrients to the landscape and wildlife of the Northwest.

These once-abundant anadromous fish populations—fish that hatch in freshwater, go to sea, and return to freshwater to spawn—in the Columbia-Snake River Basin are on the brink of extinction today due primarily to harms caused by federal dams and their warming reservoirs. Thirteen populations, including all four Snake River populations, are listed as threatened or endangered under the Endangered Species Act and at grave risk of extinction. The lower Snake River’s dams and reservoirs harm and kill both juvenile and adult fish in multiple ways, including by elevating water temperatures in the summer months in their large, stagnant reservoirs. These cold-water fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit.

In this final Hot Water Report issue, we summarize this year’s high water temperatures in the lower Snake and Columbia reservoirs, the number of days each of the reservoirs exceeded 68°F, and review the current return status for Snake River salmon and steelhead in comparison to their recovery goals. Given the current returns for wild Snake River Spring/Summer Chinook, steelhead, and sockeye, these fish are far closer to extinction than recovery. Wild fish return as adults todasy at just 1-2% of historic levels and each year salmon and steelhead are returning far, far below their historic and recovery levels.

The four federal dams and their reservoirs on the lower Snake River are the primary factor preventing salmon from reaching spawning grounds and reproducing 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 past Hot Water Report issues here: Hot Water Reports - Compiled

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

II. READING THE DATA - Highest Water Temperatures in the Lower Snake and Columbia Rivers from April 1 - September 7, 2023.

Introduction to the data:
From April 1 - September 7, 2023, we recorded water temperatures at the four reservoir forebays (measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dam) in the lower Snake River and the lower Columbia River. In the following tables (Table 1 and Table 2), we present a summary of the highest water temperatures in 2023, the date of the highest temperatures, and the number of days each of the reservoirs reached above the 68°F “harm” threshold.

The longer and the higher temperatures rise above 68°F (this threshold is the legal and biological limit scientists identify to protect salmon), 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.

Table 1: Highest water temperatures in the lower Snake River in 2023.

Discussion of data:
This year, salmon and steelhead experienced another summer of hot, harmful water temperatures in the lower Snake River and the lower Columbia River. From early July to September, all four lower Snake River reservoirs had water temperatures above 68°F.

• Hot water temperatures on the lower Snake River (Table 1): On August 19, 2023, the reservoir behind the Ice Harbor Dam registered the highest temperature recorded this summer – 72.73°F more than 4 degrees above the 68°F “harm” threshold. The Ice Harbor reservoir registered above 68°F for 62 days. Both Lower Monumental and Little Goose reservoirs registered above 68°F for 60 days.
  • Salmon in hot water: Adult and juvenile salmon have difficulty migrating when water temperatures exceed 68°F. Migration 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 begin to die from thermal stress and disease.
  • Lower Granite reservoir: The Lower Granite reservoir was the first reservoir to reach 68°F. This summer, the reservoir registered a high temperature of 71.20°F on August 22, 2023. Lower Granite reservoir registered above 68°F for 32 days, fewer days compared to the other reservoirs. This distinction is the result of the US Army Corps of Engineers' annual release of cold water from the Dworshak reservoir into 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 heat of the summer and does not cool the other three downstream reservoirs on the lower Snake. According to scientists and modelers at the Environmental Protection Agency (USEPA), with lower Snake River dam removal, the additional benefit of cold water released from the Dworshak reservoir will extend all the way down the lower Snake River to its confluence with the Columbia River in south-central Washington State.

Table 2: Highest water temperatures in the lower Columbia River in 2023.

Hot water temperatures on the lower Columbia River (Table 2):

• On August 16, 2023, the reservoir behind the Bonneville Dam registered the highest temperature recorded this summer – 73.58°F over 5 degrees above the 68°F 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 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 72 - 73°F and must continue to migrate through 4 other hot and stagnant reservoirs in the lower Snake River, often disrupting migration and increasing susceptibility to disease, suffocation (warm water carries less oxygen) and in the worst case - death.

Salmon and steelhead require clean, cold water, intact/contiguous rivers, and reliable streamflows for spawning, rearing, and migrating. Before the dams were built, juvenile salmon were able to migrate quickly to the ocean - within a few days to several weeks - due to the swiftly moving current of the mainstem Snake and Columbia rivers. Now, because of the harmful conditions created by the lower Snake River dams and their hot reservoirs, salmon and steelhead require on average more than a month to reach the ocean. Up to 70 percent of all out-migrating smolts can be killed each year before they reach the ocean as a result of dam encounters, hot stagnant reservoirs, in-reservoir predation, and extended travel time.

The science is clear: restoring the Snake River by removing the four lower Snake River dams is an essential action we must take as quickly as possible, or we will lose these wild salmon and steelhead populations forever.

A note on the data: The 2023 lower Snake River and lower Columbia River water temperature data presented in the Hot Water Report are collected from the Columbia River DART program by Columbia Basin Research, University of Washington, using data courtesy of the U.S. Army Corps of Engineers (USACE) and USGS. Tables were assembled by SOS Staff.

III. A Look at Snake River Wild Salmon & Steelhead Adult Returns as of September 11, 2023

The Snake River's anadromous fish populations have been on a steady downward trajectory for decades. These salmon and steelhead face multiple obstacles, including increasingly hot water in the summer months in the lower Snake River reservoirs. Below are the current estimated returns for native Snake River fish so far, including (1) wild Snake River Spring/Summer Chinook, (2) wild steelhead, and (3) wild/natural sockeye. We will also look at how the historical and 2023 adult returns compare to established recovery goals – the adult fish returns deemed necessary to recover these populations to abundance and remove them from the Endangered Species Act list.

In summary - since the four lower Snake River dams were built, over 60 years ago, Snake River salmon and steelhead populations have steadily declined. Long before the dams were built, scientists predicted that the construction of the lower Snake River dams would devastate salmon and steelhead populations. 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. Without immediate and meaningful conservation actions, scientists predict these populations will continue to decline to extinction.

1) Wild Snake River Spring/Summer Chinook:

• Endangered Species Act Status: Threatened (listed in 1992)
• Historical Annual Return: Over 2 million
• Columbia Basin Partnership Recovery Goal: Escapement of 127,000 wild adults per year
• Endangered Species Act Delisting Goal: 43,000 wild Snake River Spring/Summer Chinook
• 2023 Estimated Wild Returns: 10,714 wild Snake River Spring/Summer Chinook

2) Wild Steelhead: 

• Endangered Species Act Status: Threatened (listed in 1997)
• Historical Annual Return: Over 1 million
• Columbia Basin Partnership Recovery Goal: Escapement of 104,500 wild adults per year
• Endangered Species Act Delisting Goal: 30,800 wild steelhead
• 2022/2023 Wild Returns: 19,138 wild steelhead

3) Wild/natural sockeye: 

• Endangered Species Act Status: Endangered (listed in 1991)
• Historical Annual Return: Over 100,000+/yr to central Idaho’s high mountain lakes
• Columbia Basin Partnership Recovery Goal: 9,000 wild adults per year to the Stanley Basin
• Endangered Species Act Delisting Goal: 2,500 wild/natural-origin sockeye
• 2023 Estimated Wild Returns: 26 wild/natural-origin sockeye

A note on the ‘Snake River Wild Salmon Returns’ report: The data from this report comes from the Fish Passage Center and Idaho Department of Fish and Game. Tables and graphs were assembled by Idaho Rivers United staff.

IV. Urgency to restore the lower Snake River - to recover its native fish

This summer, due to hot water in the reservoirs of the lower Columbia and lower Snake rivers, roughly 80% of the returning adult Snake River sockeye that entered the mouth of the Columbia River died before spawning. In Hot Water Report Issue 9, Miles Johnson, Legal Director of Columbia Riverkeeper reported, “Hot water in these reservoirs prevented almost an entire generation of critically endangered fish from reaching their spawning gravels in Idaho—violating the Endangered Species Act and dealing another blow to the Shoshone-Bannock Tribes’ long-running effort to recover this unique and culturally important species...Without big improvements in water quality, federal scientists predict that adult Snake River sockeye survival will further decline by 80% in coming years, likely resulting in extinction.”

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 Columbia Basin Partnership recovery goal (as seen in the above section 3). According to Nez Perce Tribe fishery scientists, nearly half of Snake River salmon and steelhead populations have reached quasi-extinction thresholds—a critical threshold signaling they are nearing extinction, and without intervention, they may not persist.

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

A restored lower Snake River would provide the largest availability of high-quality free-flowing, cold-water habitat for salmon populations to recover to significant levels of abundance, and help to mitigate the impacts of cyclic ocean conditions and climate change. The benefits of dam removal would improve the ability of migrating fishes to access high-elevation, groundwater- and snowmelt-fed freshwater refuges, likely increasing survival and productivity in what will be an otherwise inhospitable future climate.

At this moment, we have an opportunity to restore ecosystem health in the heart of the Columbia Basin and recover salmon and steelhead abundance by removing the four lower Snake River dams and replacing their services. A restored, healthy, and resilient lower Snake River is necessary to 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. Restoring the lower Snake River through dam removal is our most significant river and salmon restoration opportunity anywhere in the nation today.