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 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.
The once-abundant anadromous fish populations of 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 71.98°F on July 18 – over 3 degrees above the 68°F “harm" threshold set to protect salmon and steelhead from extinction. In Issue 3, we’ll explore historical and 2022 wild Snake River salmon and steelhead returns and compare the returns to their established recovery goals – the adult returns deemed necessary to recover these populations and remove them from the Endangered Species Act list. Since the four lower Snake River dams were built over 60 years ago, Snake River salmon and steelhead returns have declined and remained far below the recovery goals necessary to remove them from the Endangered Species Act list. Without immediate and meaningful conservation actions, scientists predict we will lose these fish forever.
A restored, healthy, and resilient lower Snake River is a necessary step in order to uphold our nation's promises to Tribes and sustain salmon populations in perpetuity.
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 - Lower Snake and Columbia River Temperatures
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.
Reservoirs are large, stagnant pools that can absorb enormous amounts of solar radiation, and cause waters to warm. These waters inundate and destroy diverse micro-habitats that healthy rivers support, including cold-water refuges that salmon and steelhead rely upon during their migration. 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. Rising temperatures and reductions in snowpack in recent decades due to climate change create warmer waters, which results in lower survival and reduced reproductive success for salmon and steelhead.
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, this week, the reservoir behind the Ice Harbor Dam had the highest average temperature of 71.99°F on July 16 and July 18. The Lower Monumental reservoir had the second highest average temperature of 69.67°F on July 12.
As Figure 2 shows, this week, the reservoir behind the Bonneville dam had the highest average temperature of 71.42°F on July 16. Both juvenile and adult salmon are now experiencing water temperatures 1- 3 degrees above the 68°F “harm” threshold in several of the reservoirs they pass.
On the lower Snake River, the reservoir behind the Lower Granite Dam recorded an average temperature of 68.63°F on July 5. This week, however, the pool behind Lower Granite Dam fell to an average temperature of 67.1°F on July 18. This decrease in temperatures is the result of the US Army Corps of Engineers’ annual summer release of cold waters 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 migration, 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. By restoring a freely flowing lower Snake River, the additional benefit of cold waters released from the Dworshak reservoir will extend down the lower Snake River to its confluence with the Columbia River.
Below, we present the weekly high temperatures for each reservoir on the lower Snake and Columbia rivers for July 12 - July 18.
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 TEMPERATURES: 7/12 - 7/18
This week, on the lower Snake River, the reservoir behind the Ice Harbor Dam registered the highest water temperature at 71.98°F on July 18, and the Lower Monumental Dam registered the second highest temperature at 70.12°F on July 18.
IV. A Look at Snake River Wild Salmon & Steelhead Adult Returns
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, we present background information on the status of native fish returns, 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 2022 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 projected 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 toward extinction.
A. What Are Wild Salmon and Steelhead Returns?
The size and condition of a given population of salmon or steelhead are typically measured by the number of adult fish that return from the ocean to their upriver spawning grounds each year. The most straightforward method to measure the size of a salmon run is to count the fish as they swim upstream.
Snake River salmon and steelhead runs are counted at Lower Granite Dam, the last impediment on the river before the fish enter thousands of miles of tributary spawning and rearing habitat in central Idaho, Oregon, and Washington. Salmon returns have been counted on the lower Snake River since Ice Harbor Dam was first completed in 1962. This dataset of 60+ years, coupled with informed estimates of run sizes before the dams were constructed, provides valuable insight into the precipitous declines wild salmon and steelhead have experienced in the last 4-5 decades.
B. Historical Context
Historical data for the Columbia and Snake rivers estimates that 10-16 million wild salmon and steelhead entered the Columbia River Basin to spawn, annually, with 2-4 million more utilizing the Snake River watershed.1 The Columbia River Basin was once home to the largest runs of Chinook salmon in the world, and roughly half of those Chinook returned to the Snake River in the spring and fall seasons about 200 years ago.2 The health of these populations has plummeted over time from historic levels that were once in the hundreds of thousands or millions, depending on the particular population.
Any enthusiasm today about a modest uptick in adult returns in a given year is a symptom of what scientists call “the shifting baseline syndrome,” where the perception of what constitutes a healthy population is based only on very recent reference points. These benchmarks today are extraordinarily low due to long-term population declines. The result is that our collective perception of what constitutes a healthy salmon run continually shifts downward. Put simply, since the completion of the dams on the lower Snake River, 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, many may not persist, according to Nez Perce Tribe fishery scientists.
C. Recovery Goals: Informed By the Past, Potential for the Future
Recovery goals for wild Snake River salmon and steelhead have been set to reflect the healthy runs that returned to Idaho in the 1950s – before the dams were constructed. These goals represent self-sustaining, harvestable populations that the currently available, high-quality habitat in the Snake River Basin can support. Restoring abundant populations will allow salmon to once again function as keystone species, feeding countless animals, forests, and plants, and supporting the Northwest's unique cultures and economies. Restoring the lower Snake River through dam removal is our most significant river and salmon restoration opportunity anywhere in the nation today. A restored, healthy and resilient lower Snake River is necessary to 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.
D. Current Status of Snake River Returns
(1) Snake River Spring/Summer Chinook:
- Endangered Species Act Status: Threatened (listed in 1992)
- Historical Annual Return: Over 2 million3
- Recovery Goal: Escapement of 127,000 wild adults per year
- 2022 Wild Returns4: 16,462
- Analysis: Spring/summer chinook were once the Pacific Northwest’s most widely distributed and abundant salmon, numbering in the millions.5
In the past five years, wild Snake River Spring/Summer Chinook numbers averaged less than half of their total return when the fish were first listed under the ESA in 1992. Despite last year's small improvement in adult return wild spring/summer Chinook (16K total), we remain far from the recovery goal (a minimum of 127K annually), and the population remains in long-term decline and at risk of extinction.6
In June 2023, the Oregon Department of Fish and Wildlife (ODFW) and Washington Department of Fish and Wildlife (WDFW) announced an emergency fishing closure after Endangered Species Act limits on listed salmon were exceeded.
“Rather than pointing fingers at a particular fishery, it’s important to acknowledge the real problem, that there are way too few wild Snake River spring/summer Chinook coming back,” said Tucker Jones, ODFW Columbia River Program Manager. “NOAA’s recent ‘Rebuilding Interior Columbia Basin Salmon and Steelhead’ report acknowledges this, and notes that without aggressive, urgent actions, including restoration of the lower Snake River for Snake River spring/summer Chinook, achieving healthy and abundant populations won’t be possible. While fisheries are playing their critical role in the conservation and recovery story, it’s important that the region continue to push other sectors to do the same.”7
(2) Snake River Steelhead:
- Endangered Species Act Status: Threatened (listed in 1997)
- Historical Annual Return: Over 1 million8
- Recovery Goal: Escapement of 104,500 wild adults per year
- 2021/22 Returns9: 9,807
- Analysis: Historic runs of steelhead to the Snake River Basin were estimated to be over one million fish annually.10 The Snake River and its tributaries produced 55 percent of summer steelhead in the entire Columbia River basin.11 However, today, steelhead are returning below their recovery goal. During the summer of 2021, steelhead saw the lowest returns in history, forcing emergency fishing closures in Washington and Oregon.
(3) Snake River Sockeye:
- Endangered Species Act Status: Endangered (listed in 1991)
- Historical Annual Return: Over 100,000+/yr to central Idaho’s high mountain lakes12
- Recovery Goal: 9,000 wild adults per year to the Stanley Basin
- 2022 Wild Returns: 46 wild/natural-origin sockeye returned to the Stanley Basin13
- Analysis: Historic runs to Idaho’s high mountain lakes used to be over 100,000+ sockeye per year but have also severely declined over the years.14 In 1991, the Shoshone-Bannock Tribes successfully petitioned the federal government to list the run under the Endangered Species Act - making Snake River sockeye the first ESA-listed salmonid in the Columbia Basin. According to the Idaho Fish and Game, in 1991, only four adult sockeye returned to the Sawtooth Basin. The total number of sockeye that returned between 1991-99 was 23 fish, including two years when no sockeye returned.15
Sockeye are particularly susceptible to hot water, and along with summer Chinook, have shifted their run timing earlier to avoid warming river temperatures.16 In 2015, only 15% of migrating adult Snake River sockeye survived the trip from Bonneville to McNary Dam.16
Hot water is jeopardizing the existence of this already very fragile population. During the summer of 2021, video footage, and images showed sockeye with large, open lesions and fungus caused by hot water conditions from the lower Snake and lower Columbia River reservoirs. In 2021, only 4 wild adult sockeye salmon survived and reached their spawning grounds in the Stanley Basin in central Idaho, after struggling past eight dams and warm, stagnant reservoirs downstream.
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.
E. Hot Water Impacts
Sockeye salmon with lesions dying from hot water in the Columbia-Snake River Basin ©Conrad Gowell
Given the current returns for wild Snake River Spring/Summer Chinook, steelhead, and sockeye, these fish are much closer to extinction than recovery. Each year, salmon and steelhead are returning far, far below their historical and recovery levels.
The four federal dams and their reservoirs on the lower Snake River continue to be the main obstacle to recovery. The rising temperatures caused by these stagnant reservoirs and reductions in snowpack in recent decades due to climate change are contributing to lower survival and reproductive success for already endangered salmon and steelhead.
Restoring this historic salmon river is essential for protecting these fish from extinction and rebuilding the many benefits they provide for the people of the Northwest and our nation.
View the past Hot Water Report issues here: Hot Water Reports - Compiled
1, 2. Orca Action Month: Exploring the History of Salmon in the Columbia and Snake River Systems
3, 5, 8, 10, 11, 12, 14, 15 The Salmon Community’s View: The status of wild salmon and steelhead populations in the Columbia and Snake River Basin
4, 9, 13 Idaho Rivers United: Snake River Wild Salmon Returns report
6. Spokesman-Review: Helen Neville: The need to breach the Lower Snake River dams: A look at 2022 fish returns
7. Northwest Sportsman Magazine: Lower Columbia Closing Thursday For Chinook, Steelhead
14. Idaho Fish & Game: Idaho sockeye returns at Lower Granite Dam are already the second-highest in a decade
16. U.S. Environmental Protection Agency Region 10: Columbia River Cold Water Refuges Plan - January 2021