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

• Snake River salmon and steelhead are struggling today to migrate through lethal water temperatures in the lower Snake and Columbia rivers. On all eight lower river reservoirs, temperatures continue to register above the 68°F “harm” threshold.
• On the lower Snake River, the Ice Harbor Dam reservoir registered the highest water temperature of 71.96°F on July 25. This July, the Ice Harbor Dam reservoir has reached 22 consecutive days above 68°F and 19 consecutive days above 70°F. Both Lower Monumental and Little Goose reservoirs have registered 24 days above 68°F.
• A free-flowing lower Snake River would significantly cool water temperatures and significantly reduce the slow, effortful migration through 140 miles of hot, stagnant reservoirs and fish ladders.
• In the lower Snake River, fish ladders/fish passages are the only way for fish to pass the dams. Fish ladders frequently contain water that is hotter than the average river temperature, and such conditions create or exacerbate migration blockages. By stopping or delaying migration, these blockages reduce salmon survival and reproduction.
• A free-flowing river will provide cold-water refuges that salmon and steelhead rely upon during summer migrations, improve their migration travel time, reduce stress and in-reservoir predation, and significantly increase the overall survival of endangered salmon and steelhead. 

II. INTRODUCTION

Free Flowing III 2023, acrylic and graphite on birch panel 24" x 48" x 1.5" © Britt FredaThe 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 6, we discuss how adult salmon and steelhead must migrate through eight dams and their lethally hot water reservoir and fish ladders. In the lower Snake River, fish ladders are the only route for returning adult salmon to pass the dams. Defenders of the status quo falsely claim the lower Snake River fish ladders allow salmon and steelhead to complete their migration in their historic and natural timing and without additional stress or injury to salmon. Hot water flowing in fish ladders at each dam cause salmon and steelhead to stop or substantially slow their migration, severely reducing their ability to complete their journey and spawn.

During the summer, the 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: 7/25 - 7/31

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 reservoir reached a high average water temperature of 71.67°F on July 25, exceeding its 10-year average of 71°F.
• The Lower Monumental reservoir registered a high average temperature of 70.62°F and the Little Goose Dam registered 70.21°F on July 27.
• The Lower Granite reservoir registered a high average of 67.19°F. Lower Granite Dam’s reservoir’s average registered below 67°F due to the US Army Corps of Engineers’ continued cold water release effort from the reservoir behind Dworshak Dam. However, these cold water releases do not significantly cool the other three lower Snake River reservoirs.

WEEKLY HIGH TEMPERATURES IN THE LOWER SNAKE RIVER: 7/25 - 7/31

• On the lower Snake River, all four reservoirs continue to register temperatures above the 68°F “harm” threshold. This July, the Ice Harbor Dam reservoir reached 22 consecutive days above 68°F and 19 consecutive days above 70°F. The Lower Monumental and Little Goose reservoirs reached 24 days above 68°F.
• Ice Harbor Dam reservoir registered the highest water temperature of 71.96°F on July 25. The reservoir behind the Lower Monumental Dam registered the second highest water temperature of 71.26°F on July 27.
• The Little Goose Dam reservoir registered a high water temperature of 70.56°F and Lower Granite Dam reservoir reached a high water temperature of 68.52°F on July 26.

LOWER COLUMBIA RIVER WATER TEMPERATURES: 7/25 - 7/31

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 reached water temperatures above 68°F.
• The reservoir behind The Dalles Dam had a high average temperature of 70.88°F on July 27. The reservoir behind the John Day Dam reached an average temperature of 70.70°F on July 25.

WEEKLY HIGH TEMPERATURES IN THE LOWER COLUMBIA RIVER: 7/25 - 7/31

• On the lower Columbia River, The Dalles Dam reservoir registered the highest water temperature at 71.24°F on July 27. The John Day Dam reservoir reached the second highest water temperature at 70.88°F on July 25-July 26.
• The Bonneville Dam reservoir reached 26 consecutive days above 68°F and both The Dalles Dam and John Day Dam reservoirs registered above 68°F for 25 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. Restoring a free-flowing lower Snake River is vital for protecting its endangered salmon and steelhead from extinction

Fish ladder at Lower Monumental Dam © Trout Unlimited

Each summer, adult salmon and steelhead struggle to migrate from the Pacific Ocean to their spawning grounds in tributaries above the lower Columbia and Snake Rivers. In this process, they encounter eight dams with fish ladders and eight hot water reservoirs. Defenders of the status quo falsely claim the lower Snake River fish ladders allow fish to complete their migration in their historical and natural timing and without additional stress or injury. Despite fish ladders at the lower Snake River dams, returning adult fish often stop or slow their migration as they encounter increasingly hot water in fish ladders and in reservoirs.

What are fish ladders?

Fish ladder and passage diagram by U.S. Army Corps of Engineers

According to the Army Corps of Engineers, as part of their salmon recovery program, fish ladders and devices to attract fish to the entrances of the ladders help fish pass the dams, “allows adult salmon and steelhead to migrate upstream of a dam on their own, provides fish time to rest as they migrate up the ladder, allows natural migration timing, and ladders are less stressful than other fish passage methods.”

Ohhh…if it were only that simple!

Hot water in fish ladders harms returning adult salmon and steelhead and interrupts their migration.

In the lower Snake River, fish ladders/fish passages are the only route past the dams. Fish ladders frequently contain water that is warmer than the average river temperature, and such conditions can create or exacerbate migration blockages, reducing salmon survival. The ladders can expose adult salmon to especially warm surface waters that are used, causing salmon and steelhead to slow or stop their migration upstream to reach the reservoir. These types of delays can reduce successful migration to spawning grounds, and increase a fish’s total thermal exposure.

Among various salmon and steelhead species, sockeye are especially sensitive to elevated water temperatures. As we reported in Issue 5, many Snake River sockeye have been observed this summer seeking refuge from hot water temperatures in the lower Snake River by moving (straying) into the Mid-Columbia River, where water temperatures are cooler.

Last summer, sockeye salmon counts at the lower Snake River dams declined when water temperatures increased. The Fish Passage Center (FPC) reported sockeye ladder counts and PIT-tag conversion in the lower Snake River dropped precipitously during the first two weeks of July. This drop in fish migrating coincided with a sharp rise in river temperature and an even larger spike in ladder temperatures at Little Goose and Lower Monumental dams. During 2023 high-temperature events, far fewer fish passed the Lower Monumental and Little Goose dams than scientists predicted. In July 2023, the highest temperatures in these fish ladders were between 68°F - 77°F. The FPC also reported that the hot water temperatures in the ladders likely contributed to the additional migration travel time for fish, which resulted in further heat stress accumulation and, therefore, a decline in adult survival and reproduction.

Throughout this month of July, Columbia Basin Research reported lower Snake River fish ladders registered high temperatures between 68°F - 78°F–significantly higher temperatures than the 68°F “harm” threshold, the legal and biological limit identified to protect salmon from lethal water temperatures.

Our options to cool the lower Snake River fish ladders are extremely limited

Fish ladder at Little Goose Dam on the lower Snake River © Tess McEnroe/Idaho Rivers United

After the catastrophic 2015 fish kill event, in which at least 96 percent of returning adult Snake River sockeye salmon died in the hot water reservoirs, the Army Corps of Engineers implemented fish cooling systems at Lower Granite and Little Goose dams in an effort to alleviate warming water. They constructed a system to pump this cool water into the Lower Granite Dam fish ladder. It is, however, totally inadequate and does nothing to cool the three downstream Snake reservoirs or meaningfully improve fish passage in those ladders.

When aging ladders and their cooling systems fail, the consequences can be dire, as there are no other options for adult salmon to pass dams and reach their spawning grounds. The water used in ladders are provided either by turbines or pumps, many of which are aging and have failed. In the event of failure, the ladders become inoperable and fish passage ceases. The Fish Passage Center reported that in 2023, fish had an especially difficult time passing the lower Monumental Dam due to high temperatures in the reservoir and fish ladders, made worse by the loss of the ladder’s cool water pump that went out of service.

A report by the Columbia River Inter-Tribal Fish Commission, states that the total cost of ladder repairs and improvements in the lower Columbia and Snake Rivers, identified by tribal, federal, and state technical experts is $160.4M today. Many billions of dollars have been spent to maintain and repair the dam infrastructure on the lower Snake River, yet, wild salmon returning to the Snake River Basin are just 0.1-2% of the abundance at the time the United States entered the 1855 Treaties with Tribes.

Restoring a free-flowing lower Snake River will provide cold clean water for salmon and steelhead and deliver big survival benefits

The lower Snake River dams, their reservoirs, and fish ladders impact fish in many ways, including elevating water temperatures, creating large, stagnant reservoirs, destroying and degrading habitat required for key life stages, and much more.

The science is clear: A free-flowing lower Snake River would no longer force fish to migrate through 140 miles of hot, stagnant reservoirs and fish ladders. A free-flowing river will provide cold-water refuges that salmon and steelhead rely upon during summer migrations, reduce their migration travel time, and significantly increase their survival.

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