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

I. EXECUTIVE SUMMARY

• For decades, summer water temperatures in the lower Snake and Columbia rivers have been rising to levels that are lethal to salmon and steelhead.
• 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.
• Snake River salmon and steelhead populations suffer the highest mortality rates compared to other fish that spawn lower in the watershed and encounter fewer dams and reservoirs. Snake River salmon and steelhead encounter 8 dams and reservoirs - twice, in each direction - to successfully complete their anadromous lifecycle.
• Despite fluctuating ocean environments and influences due to a changing climate, scientists have consistently found that dam removal will significantly increase the survival and abundance of Spring Chinook and other salmon to achieve healthy and harvestable recovery goals that have been identified by regional tribes, stakeholders, and state and federal agencies.
• Scientists have determined that breaching the four lower Snake River dams is essential for avoiding extinction and would greatly improve the ability of migrating fishes to access these high-elevation, groundwater- and snowmelt-fed freshwater refuges, increasing their survival and productivity.

 II. INTRODUCTION

Pilgrimage, 2020, acrylic painting on birch panel, 24" x 30" © Josh Udesen

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 warm, stagnant reservoirs. The Columbia-Snake federal hydro-system harms and kills both juvenile and adult fish in multiple ways, including by elevating water temperatures in its reservoirs in the summer months. These cold-water fish begin to suffer harmful effects when water temperatures exceed 68° F.

In Issue 2 of the Hot Water Report 2024, we correct the record misleading narratives that warming ocean conditions are the real obstacle to recovering healthy, abundant populations of Snake River salmon and steelhead. 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.

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 critically endangered Southern Resident orcas.

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 and 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. REMOVING THE LOWER SNAKE RIVER DAMS WILL RECOVER 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 during their migration. Endangered Snake River salmon and steelhead must traverse eight stagnant reservoirs created by federal dams as they migrate to the ocean and again on their journey back upstream as adults. Defenders of the status quo falsely claim that warming, unproductive ocean conditions - rather than the federal hydro-system - are the real obstacle to protecting and 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 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 currents of the Snake and Columbia rivers. Now, because of the harmful conditions created by the lower Snake River dams and their reservoirs, it takes often takes young fish more than a month to reach the ocean. According to scientists, Snake River fish that successfully reach the ocean, often arrive injured, energy-depleted, and weak, leading to 'delayed mortality' in the estuary and the ocean. The few fish that do survive and grow into adults will range in the ocean between one and six years. Adult salmon then return to spawn, and die, in the same river or stream 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.

In the Columbia-Snake Basin, the construction of the federal hydro system has profoundly degraded viable fish habitat and is the primary source of mortality for salmon and steelhead.

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 salmon returns decline too.

How do we know the lower Snake River dams are a large source of mortality for Snake River fish?

We use the smolt-to-adult ratio - or SAR - to understand 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). According to regional Tribal, federal, and state scientists, 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 four lower Snake River dams in 1975, SARs for Snake River Chinook salmon fell dramatically. Today, adult salmon return 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 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.

The cold, clean, high-elevation streams, just beyond the four lower Snake River dams, can serve as a safe haven for salmon in the face of climate change — if only the salmon can reach them. Stanley Lake in front of McGowan Peak. Sawtooth Mountains, Idaho. (Neil Ever Osborne / Save Our Wild Salmon / iLCP)

Does removing the four lower Snake River dams recover salmon and steelhead as climate change impacts continue?

Climate change has altered salmon and steelhead’s freshwater and saltwater ecosystems. As climate changes affect air temperatures, precipitation, snowpack, and wind patterns in the Pacific Northwest, it brings an increase of land and river heat waves, droughts, wildfires, and variations in river flow patterns.² 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. Dams and their reservoirs continue to elevate high water temperatures that impair salmon and steelhead survival and productivity and prevents salmon and steelhead from accessing cold clean water.

The science is clear: even with climate change impacts, the tributary habitat in the Snake River Basin will remain suitable for fish. The Snake River Basin currently contains 20% of the habitat occupied by salmon and steelhead in rivers of the Pacific Northwest; by 2080 it is forecast to contain 65% of the coldest, most climate-resilient stream habitats in the region.³ Scientists have determined that breaching the four lower Snake River dams would significantly improve the ability of migrating fishes to access these high-elevation, groundwater- and snowmelt-fed freshwater refuges, increasing survival and productivity in what will be an otherwise inhospitable future climate.⁴

“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

Ocean environments fluctuate between good and bad conditions, and climate change is affecting the health of the ocean as well. 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.⁵ Under the model's dam removal scenario, Spring Chinook salmon increased in abundance and above healthy and harvestable recovery goals under all ocean conditions.

While addressing the health of the ocean and tackling climate change by dramatically reducing our fossil fuel consumption must be a top priority now and over time, it is also critical that we focus our efforts on effective, near-term solutions that will increase and improve salmon survival in their 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 - and miss one of our nation's great restoration opportunities - forever.

References:
1. Trout Unlimited: What is a smolt-to-adult ratio and why is it important?
2. National Oceanographic and Atmospheric Administration and National Marine Fisheries Service: Rebuilding Interior Columbia Basin Salmon and Steelhead
3, 4. Storch et al. 2022. A review of potential conservation and fisheries benefits of breaching four dams in the Lower Snake River (Washington, USA)
5. 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.

IV. 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.
• Daily average temperatures are represented with solid lines and the 10-year average (2014 - 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 oxygen), and in worst case - death.

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

AVERAGE LOWER SNAKE AND COLUMBIA RIVER TEMPERATURES: 6/26 - 7/2

Figure 1. Lower Snake River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph.

Figure 2. Lower Columbia River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph.Discussion of average water temperature data:

• Since April, temperatures in the lower Snake River and the lower Columbia River reservoirs have steadily increased.
• Figure 1. Lower Snake River Water Temperatures: this week, the reservoir behind the Lower Granite Dam reached a high average water temperature of 66.16°F on July 2 and has reached over their 10-year average.
• Figure 2. Lower Columbia River Water Temperatures: this week, the reservoirs behind the Bonneville Dam had a high average temperature of 65.66°F on July 1.
• As we begin the month of July, the water temperatures are below the 68°F “harm” threshold, which is good news for cold-water species like salmon and steelhead. However, we expect these temperatures will rise considerably in these reservoirs as the summer progresses.

WEEKLY HIGH TEMPERATURES IN THE LOWER SNAKE AND COLUMBIA RIVER: 6/26 - 7/2

• On the lower Snake River, the reservoir behind the Lower Granite Dam registered the highest water temperature of 66.51°F.
• On July 1, due to Lower Granite reaching high water temperatures above 66°F and nearing the 68°F “harm” threshold, the US Army Corps of Engineers announced the start of their annual summer release of cold waters from the Dworshak Reservoir in 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 on the lower Snake River. With a free-flowing river, the additional benefit of cold waters 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.

• On the lower Columbia River, the Bonneville reservoir registered the highest water temperature at 66.02°F.

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.

 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