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

• For over a month, the lower Columbia and Snake River reservoirs have experienced temperatures above the 68°F “harm” threshold; many of the reservoir waters are between 70°F and 72°F.
• Populations of wild Snake River spring/summer Chinook, steelhead, and sockeye all remain listed under the Endangered Species Act and at continued risk of extinction.
• As of August 15, only 4 natural-origin Snake River sockeye have successfully migrated past eight dams and their hot reservoirs on the lower Columbia and Snake rivers and returned to their spawning grounds in Stanley Basin in Central Idaho.
• 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

Salmon Leaping © Dave McCoy

The once-abundant anadromous fish populations in the Columbia-Snake River Basin are struggling to survive today primarily due to multiple harms caused by the federal dams and their reservoirs. The federal hydro-system creates conditions that harm and kill both juvenile and adult fish, including by elevating water temperatures in large, stagnant reservoirs in the summer months. These cold-water fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit.

In Issue 8, Idaho Rivers United reports on the current status of adult wild Snake River Spring/Summer Chinook, steelhead, and sockeye. Despite decades of effort and many billions of dollars in recovery spending, these fish remain on the edge of extinction. Wild fish return as adults today at just 0.1-2% of historic levels - far, far below their historic and recovery levels.

During the summer, SOS’ Hot Water Report provides 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, 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. 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.
• Data collection: 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. The water temperatures are taken on the hour. Hourly temperatures are used to find the highest temperatures reached in each reservoir, and hourly temperature measurements are used to find the daily average temperatures.
• Average Water Temperature Graphs (below): Daily average temperatures are represented with solid lines, and the 10-year average (2014 - 2023) temperatures are with dashed lines of the same color. The dotted line across the graph represents the 68°F “harm threshold” for adult and juvenile fish.
• Weekly High Water Temperature Tables (below): This table outlines the highest water temperatures reported for each reservoir during the week and how many days water temperatures have exceeded 68°F.
• Hot water temperature effects to salmon: The longer and the higher water temperatures rise above 68°F, 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 worst case - death.

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

LOWER SNAKE RIVER WATER TEMPERATURES: 8/8 - 8/16

Lower Snake River - 2024 Daily Average and 10-year Average.

Lower Snake River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir.

• Lower Snake River Water Temperatures: this week, the Ice Harbor Dam's reservoir reached a high average water temperature of 72.01°F on August 10.
• The Lower Monumental Dam's reservoir registered a high average temperature of 71.11°F on August 8.
• On August 9, the Little Goose reservoir registered 70.89°F, and the Lower Granite reservoir registered a high average of 70.26°F.

WEEKLY HIGH TEMPERATURES IN THE LOWER SNAKE RIVER: 8/8 - 8/16

• For over a month, the lower Columbia and Snake river reservoirs have exceeded the 68°F “harm” threshold and many of the reservoirs’ temperatures have ranged between 70°F - 72°F.
• The Ice Harbor Dam's reservoir reached the highest water temperature of 72.50°F on August 10. 
• This week, Lower Monumental Dam’s reservoir registered a high water temperature of 71.37°F and the Little Goose Dam's reservoir registered a high temperature of 71.38°F. 
• The Lower Granite Dam's reservoir registered a high water temperature of 71.24°F.
• Water temperatures in the Ice Harbor Dam reservoir have exceeded 68°F for 38 consecutive days, and ranged between 70°F - 72°F for 35 consecutive days. Both the Lower Monumental Dam’s and Little Goose Dam’s reservoirs have exceeded 68°F for 40 days.

LOWER COLUMBIA RIVER WATER TEMPERATURES: 8/8 - 8/16

Lower Columbia River - 2024 Daily Average and 10-year Average.

Lower Columbia River Water Temperatures - 2024 Daily Average and 10-year Average. Click on the image to view the graph and click here to view the PDF version with separate graphs for each reservoir

• Lower Columbia River Water Temperatures: this week, all four reservoirs on the lower Columbia River exceeded 68°F.
• The reservoir behind The Dalles Dam had a high average temperature of 71.96°F on August 10 and 11. This week. the reservoir behind Bonneville Dam and John Day Dam both reached an average temperature of 71.60°F.

WEEKLY HIGH TEMPERATURES IN THE LOWER COLUMBIA RIVER: 8/8 - 8/16

• On the lower Columbia River, the John Day Dam reservoir registered the highest temperature at 72.50°F on August 8 and August 9. The Dalles Dam reservoir reached the second highest temperature at 72.32°F on August 10 and August 11.
• The Bonneville Dam reservoir has spent 42 consecutive days above 68°F and both The Dalles Dam and John Day Dam reservoirs registered above 68°F for 41 days.

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.

V. Current Status of Wild Adult Snake River Salmonids Returns (Numbers as of 8/12/24)

A report by Idaho Rivers United

“Salmon runs have plummeted since the signing of the treaties and reservation executive orders that would protect the Tribes’ harvest rights.[...] 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.” — Historic and Ongoing Impacts of Federal Dams on the Columbia River Basin Tribes, Dept. of Interior

 SNAKE RIVER SPRING/SUMMER CHINOOK

SNAKE RIVER STEELHEAD (as of: 8/12/24)

SNAKE RIVER SOCKEYE

Current Status of Wild Snake River Salmonids

Populations of wild Snake River spring/summer Chinook, steelhead, and sockeye all remain listed under the Endangered Species Act, and on a long-term trajectory towards extinction.

NOAA Fisheries’ 2022 report Rebuilding Interior Columbia Basin Salmon and Steelhead outlines the actions necessary to achieve regionally agreed upon mid-range goals for salmonid abundance by 2050. These goals were developed by a diverse group of sovereigns and stakeholders within the Columbia Basin Partnership effort, convened by NOAA’s Marine Fisheries Advisory Committee (MAFAC) in 2017.

The high-range abundance goals reflect “healthy and harvestable” levels of wild salmonids returning to currently accessible habitat in the Snake Basin and are displayed in the compiled data above. The mid-range goals are a halfway point between the low-range, ESA-delisting targets of abundance necessary to ensure long-term survival of the species, and high-range goals.

It is important to note that the high-range goals for Snake River salmonids do not reflect historical abundance, but are based on 1950s spawning escapements. Since then, the still-accessible Snake Basin river habitat of Central Idaho and Eastern Oregon has remained pristine and in places seen improvements in quality and connectivity via restoration activities. As a result, there are thousands of miles of high-quality, cold-water spawning and rearing habitat capable of supporting “healthy and harvestable” salmonid abundances now and into a warmer future.

The premier example of this habitat is the Middle Fork of the Salmon River in central Idaho. It possesses high-quality habitat that supports 100% wild, genetically-diverse salmon runs with unique, locally adapted populations and high resilience to disturbances. If Snake River salmon should be doing well anywhere, it is here. However, every Middle Fork population is non-viable and at high risk of extinction due to low abundance and low productivity. Population graphs of salmon in the Middle Fork mirror those of Snake River salmon in general. This fact underscores that the problem is out of Basin - in the downstream migration corridor.

The Columbia Basin Restoration Initiative (CBRI) document, crafted by the Six Sovereigns, envisions how a comprehensive solution to recovering Columbia Basin salmonid populations will occur. In the case of Snake River salmonids it references NOAA’s findings and says this:

“The NOAA Rebuilding Report concludes that achieving the “highest and only reasonable certainty” of 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. The Rebuilding Report found that breaching is an essential “centerpiece” action for Snake River stocks. Current and projected fish status (as described in the NOAA Rebuilding Report) clarifies that implementation of this centerpiece action is urgent, but implementation can be sequenced appropriately to secure continuity of services provided by the dams if necessary investments are expedited.”

Lower Snake River dam breaching and maximum spill over the remaining four lower Columbia River dams was modeled by the Fish Passage Center (FPC). The FPC found that this would result in 4 times higher smolt-to-adult returns (SARs) and return abundances compared to current population levels.

Sockeye Impacted by Hot Water

Sockeye salmon © Neil Ever Osborne

Hot July and August water temperatures in the lower Snake River reservoirs have created significant problems for Snake River sockeye. It resulted, for example, in approximately 18% of returning adult Snake River sockeye that were detected downstream at the Bonneville Dam failing to return to the Snake and instead straying into the cooler upstream waters of the mainstem Columbia River above McNary Dam. Some level of straying is normal - it’s an adaptive behavior that contributes to salmon’s astonishing resilience and productivity - but a normal year would see stray rates in the range of 2-3%. Unfortunately, despite the slight but encouraging uptick in Snake River sockeye that entered the mouth of the Columbia River this spring/summer, too many aren’t actually returning to the Snake River as they seek cooler waters elsewhere in the Columbia. And few adult sockeye have been detected passing Lower Granite Dam - the last dam on the lower Snake River before crossing the border into Idaho.

These conditions, combined with the fragile status of endangered Snake River sockeye, motivated Idaho Department of Fish and Game (IDFG) to initiate an emergency "Trap and Haul” operation at Lower Granite Dam. Through July, a total of 255 sockeye salmon were trapped at the dam and transported to the Eagle Fish Hatchery. Through genetic stock identification, biologists will determine how many Columbia River sockeye strays are included in that total. This is an important strategy this year to help boost the survival of this critically endangered population, but it is in no way an effective long-term strategy for sustaining, much less restoring it.

As of this writing, just 4 natural-origin sockeye have returned to the Stanley Basin in Central Idaho. Sockeye and other cold water salmonids can handle some hot water—especially in rivers like the Salmon River where cooler tributaries provide refuge during their upriver migration. But the cumulative impact of hot reservoirs in the lower Columbia and the lower Snake must be addressed as quickly as possible to reduce water temperatures and reduce the overall exposure time for these fish to waters above 68°F.

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