Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin ©Conrad Gowell
Welcome to the 2023 Hot Water Report: Warming Waters in the Lower Snake and Columbia Rivers.
During the summer, this weekly report provides an update on real-time water temperatures in the lower Snake and Columbia River reservoirs via graphs and analyses, a summary of the highest weekly water temperatures at the forebay/reservoir of each federal dam, and a monthly status of adult returns for different salmon and steelhead populations as they make their way back to their natal spawning grounds. We’ll report first-hand from scientists, Tribal members, fishing guides, advocates, and other experts about the challenges facing these rivers – and our opportunities to improve and restore them - in order to recover healthy, resilient fish populations and the benefits they deliver to Northwest communities, other fish and wildlife populations (including the critically endangered Southern Resident orca), and ecosystems.
Many 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. The Columbia-Snake federal hydro-system harms and kills 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.
This week, on the lower Snake River, the reservoir behind the Ice Harbor Dam registered the highest water temperature at 72.73°F on August 19. This week, on the lower Columbia River, the John Day reservoirs registered the highest water temperature at 73.40°F. Salmon and steelhead entering the lower Columbia River are facing temperatures at 73°F—5 degrees above the 68°F “harm” threshold. In Issue 8, we’re addressing how the lower Snake River dams’ impact Snake River salmon and steelhead and their freshwater ecosystems. There is a misleading narrative that warming ocean conditions are the real obstacle to recovering healthy, abundant populations of Snake River salmon and steelhead. Yet, Snake River salmon and steelhead suffer the highest mortality rates, and lowest smolt-to-adult return ratios, compared to other fish that spawn lower in the watershed and encounter fewer dams and reservoirs. This issue reports the current estimated status of Snake River salmon and steelhead returns as of August 17, 2023.
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, recover and protect these once-highly prolific fish populations from extinction, uphold our nation's promises to Tribes, and help feed the critically endangered Southern Residents.
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 - Water Temperatures in the Lower Snake and Columbia Rivers
Figure 1. Lower Snake River Water Temperatures - 2023 Daily Average and 10-year Average. Click on the image to view the graph.
Introduction to the data:
The daily average temperature 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 (above) and the lower Columbia River (below) for 2023 is represented with solid lines and the 10-year average (2013 - 2023) temperatures with dashed lines of the same color. The dotted line across the graph represents the 68°F “harm threshold” for adult and juvenile fish.
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 dissolved oxygen), and in the worst case - death.
Figure 2. Lower Columbia River Water Temperatures - 2023 Daily Average and 10-year Average. Click on the image to view the graph.
Discussion of data:
Since April, temperatures in the lower Snake River and the lower Columbia River reservoirs have steadily increased. As Figure 1 shows, the reservoir behind the Ice Harbor Dam had the highest average temperature of 71.83°F on August 19. The Lower Monumental reservoir had the second highest average temperature of 71.52°F on August 14.
As Figure 2 shows, the reservoir behind the John Day Dam registered the highest average temperature of 72.86°F on August 20. Both juvenile and adult salmon continue to experience water temperatures well above the 68°F “harm” threshold for over 50 days.
Below, we present the weekly high water temperatures for each reservoir on the lower Snake and Columbia rivers for August 18 - August 23.
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). 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, and McNary reservoir water temperature data is collected from USACE with current available data. Graphs and tables were assembled by SOS Staff.
III. WEEKLY HIGH WATER TEMPERATURES: August 18 - August 23
This week, on the lower Snake River, the reservoir behind the Ice Harbor Dam registered the highest water temperature at 72.73°F on August 19, and the Lower Monumental Dam registered the second highest temperature at 71.71°F on August 20.
This week, on the lower Columbia River, the John Day reservoirs registered the highest water temperature at 73.40°F.
IV. Restoring a healthy lower Snake River for salmon and steelhead
Northwest salmon and steelhead all swim in the same ocean; however, their mortality rates increase significantly with the number of dams and reservoirs they encounter. Endangered Snake River salmon and steelhead must traverse eight stagnant reservoirs created by federal dams on their migration to the ocean and again on their journey back upstream as adults. There is a misleading narrative advanced by defenders of the status quo that warming ocean conditions are the real obstacle to recovering healthy, abundant populations of Snake River salmon and steelhead. Yet, Snake River salmon and steelhead suffer the highest mortality rates, and lowest smolt-to-adult return ratios, compared to other fish that spawn lower in the watershed and encounter fewer dams and reservoirs.
Salmon and their ecosystems:
Freshwater: Salmon and steelhead require clean, cold water, intact/contiguous rivers, and reliable streamflows for spawning, rearing, and migration. 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 Snake and Columbia rivers. Now, because of the harmful conditions created by the lower Snake River dams and their hot reservoirs, it takes salmon and steelhead on average more than a month to reach the ocean. According to scientists, Snake River fish that successfully reach the ocean, often arrive injured, stressed, and weak, leading to 'delayed mortality' in the estuary and the ocean. The fish that do survive will range in the ocean for one to six years. Adult salmon then return to freshwater to spawn, and die, in the same rivers or streams where they were born. Steelhead are a little different; they have the ability to return to the ocean after they spawn and repeat this process one or more times–albeit this capacity has diminished due the number of dams and reservoirs they encounter on their journey.
Saltwater: The ocean has a long-running and well-documented cyclic pattern of good conditions followed by bad conditions. Ocean conditions play a significant role in salmon and steelhead survival. When ocean conditions are good (abundant food availability for salmon and steelhead to eat), salmonid survival in the ocean increases, and we see increased survival of juvenile fish as they enter the ocean and increased adult salmon returns back into the Columbia-Snake Basin. When ocean conditions decline (reduced food availability), we often see adult returns decline too.
“Scientific studies continue to show that breaching the four lower Snake River dams would 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.” –The American Fisheries Society (AFS) and The Western Division AFS
The lower Snake River dams' impact on freshwater habitat and salmon:
This summer, the Northwest is experiencing ocean heat waves amplified by climate change and El Niño. While addressing ocean conditions must be a priority now and over time, there are necessary and meaningful actions we can - and must - take today in freshwater ecosystems to protect our region’s emblematic Snake River fish from extinction and to restore them to abundance. Like many other parts of the country this summer, the Northwest is experiencing land and river heat waves. Due to early snowmelt, a lack of spring rain and warmer spring, and low streamflows, the Washington Department of Ecology declared a drought emergency on July 24, for multiple counties located in the lower Snake River Basin.
Dams increase water temperatures in the lower Snake River reservoirs to lethal levels. They absorb solar radiation and destroy diverse microhabitats within healthy rivers, including cold-water refuges for migratory fish. During summer nights, there is little opportunity for reservoirs to cool. Restoring a free-flowing Snake River by removing its four dams is essential for preventing salmon extinction.
In the Columbia-Snake Basin, the construction of the federal hydro system has profoundly degraded viable fish habitat. The four lower Snake River dams are an undeniably large source of mortality for salmon and steelhead.
“The basin’s native salmon and steelhead hover on the brink of extinction. Today, only 1-2% of historic wild salmon and steelhead return to the Snake River to spawn above the four lower Snake River dams. Climate change will continue to worsen the outlook for these coldwater species.
Ensuring access to this high-elevation habitat is the best opportunity to promote broad-scale population recovery in the face of warming waters.” –Doug Austen, Executive Director of American Fisheries Society and Helen Neville, Senior Scientist at Trout Unlimited
How do we know the lower Snake River dams are a large source of mortality for Snake River fish?
Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin ©Conrad Gowell
We use the smolt-to-adult ratio - or SAR - to see the percentage of ocean-bound juvenile fish that return as adults to spawn in freshwater.1 SAR is the only metric that captures the cumulative impacts of the hydro-system on salmon and steelhead and thus indicates the sustainability of adult returns. In order to maintain current population levels, Snake River salmon must return consistently at a 2 percent SAR (meaning, for every 100 smolts that head out to the ocean, 2 adults must successfully return to spawn). Rebuilding abundant, harvestable Snake River salmon and steelhead populations will require SARs between 4 and 6 percent (for every 100 smolts that head out to the ocean, 4 to 6 adults must successfully return to spawn).
After the completion of the lower Snake River dams in 1975, SARs for Snake River Chinook salmon have fallen consistently below 1 percent and steelhead SARs average just over 1%. This decline in SARs below 1% represents a trajectory toward extinction as not enough smolts survive to maintain healthy population numbers over time.
Smolt-to-Adult Ratios (SARs) decrease as the number of dams and reservoirs fish encounter increase:
- Fish encountering 2 - 3 dams: Almost 7% of steelhead smolts from Oregon’s Deschutes River, who pass just two dams going and coming, successfully return as adults. More than 5% of Steelhead smolts from the John Day River, (three dams) return as adults, as do about 3.6% of Chinook smolts.
- Fish encountering 4 dams: On the Yakima River, about 4.5% of steelhead smolts return to spawn, as do a little over 2.7% of Chinook.
- Fish encountering 8 dams: Snake River salmon and steelhead encounter 8 dams and reservoirs - twice, in each direction - to successfully return as adults. On average, just 1.6% of these steelhead smolts return as adults and only 0.76% of Chinook pass the Lower Granite Dam and complete the journey.
The evidence is clear – the more dams that anadromous fish populations must navigate, the lower the smolt-to-adult return ratio.
“The SARs tell the story that matters: passage through four dams or fewer allows SARs that equal maintaining and rebuilding salmon populations. Passage through eight dams yields SARs that point to imminent extinction. Clearly, the fewer dams and the more juvenile salmon we can get to the ocean in good condition, the better chance we have of getting more adults back to their spawning grounds regardless of ocean conditions.” –Rick Williams, Fisheries ecologist and Research Associate in the Department of Biology at The College of Idaho.
Restoring the lower Snake River and its fish:
Through modeling, scientists compared Spring Chinook returns with the dams in place and with removal of the lower Snake River dams under three ocean conditions: bad, average, and good.2 With dam removal, Spring Chinook returns increased in abundance and above healthy and harvestable recovery goals under each ocean condition.
As ocean conditions continue to decline in the face of climate change, it is critical that now, more than ever, we focus our efforts on near-term, tangible solutions that will increase and improve salmon survival in freshwater habitat. We may not be able to control the cyclical ocean conditions that salmon encounter, but we can restore health to the rivers they journey through on their way to and from the ocean. 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 its wild salmon and steelhead populations forever.
1. Trout Unlimited, What is a smolt-to-adult ratio and why is it important?
2. NMFS (National Marine Fisheries Service), 2020. A vision for salmon and steelhead: goals to restore thriving salmon and steelhead to the Columbia River basin. Phase 2 report of the Columbia River Partnership Task Force of the Marine Fisheries Advisory Committee. Portland, OR
V. Current Status of Snake River Returns as of 8/17/23
“As we consider the future of our Northwest salmon and the communities that rely on it, we must make decisions grounded in scientific evidence. As returns continue to decline, decision-makers at all levels must take swift and decisive action to breach the lower four Snake River dams.” –Doug Austen, Executive Director of American Fisheries Society and Helen Neville, Senior Scientist at Trout Unlimited
Below are the current estimated returns of native Snake River fish so far, including (1) wild Snake River Spring/Summer Chinook, (2) wild steelhead, and (3) wild/natural sockeye. 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 toward extinction.
- Endangered Species Act Status: Threatened (listed in 1992)
- Historical Annual Return: Over 2 million
- Recovery Goal: Escapement of 127,000 wild adults per year
- 2023 Estimated Wild Returns as of August 17: 10,714
- Endangered Species Act Status: Threatened (listed in 1997)
- Historical Annual Return: Over 1 million
- Recovery Goal: Escapement of 104,500 wild adults per year
- 2022/2023 Estimated Wild Returns as of August 17: 19,138
- Endangered Species Act Status: Endangered (listed in 1991)
- Historical Annual Return: Over 100,000+/yr to central Idaho’s high mountain lakes
- Recovery Goal: 9,000 wild adults per year to the Stanley Basin
- 2023 Estimated Wild Returns as of August 17: 12 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.