INTRODUCTION: 
The Hot Water Report provides real-time data in the lower Snake and Columbia river reservoirs to detail the collective impacts of hot, stagnant, and toxic waters on already-imperiled salmon and steelhead. This year’s report focuses on bringing the data to life, featuring stories from scientists, Tribes, and community members regarding the challenges our Northwest native fish face, and the opportunities to heal their rivers and the ecosystem.

EXECUTIVE SUMMARY:

1. Hot water temperatures in the lower Snake and Columbia rivers: Many of the reservoirs behind the lower Snake and Columbia River dams have experienced more than 70 days of water temperatures exceeding the 68°F “harm threshold” set to protect migrating salmon and steelhead. 
   • Highest water temperature in the lower Snake River: Lower Granite Dam’s reservoir registered the highest water temperature of 71.73°F on September 7.
   • Total days above 68°F: Ice Harbor reservoir has been above 68°F for 74 consecutive days.
   • Read current water temperatures in the lower Columbia and Snake rivers here. 
2. Toxic water in the lower Snake River: Water in the lower Snake River continues to test positive for microcystins, a toxin that harms the liver and is commonly responsible for human and animal poisonings, and habitat degradation. On September 4, Whitman County Public Health issued another Health Advisory after a water sample tested positive for microcystins at Wawawai Landing in the Lower Granite Dam’s reservoir. The toxic algal blooms have grown over the course of this summer and are located today intermittently between the Little Goose Dam and Lower Granite Dam.
3. Benefits of a free-flowing lower Snake River: We have a once-in-a-lifetime opportunity to lead the largest salmon and river restoration in history, bolster the Northwest economy, and modernize our infrastructure and replace the services of the lower Snake River dams for a more resilient future. In this issue of the Hot Water Report, we’ll focus on the importance of salmon recovery and the opportunity that restoration of the lower Snake River represents to expand the recreation economy, and how the benefits of service replacement can better serve the needs of communities, ratepayers, and businesses throughout the Columbia-Snake River Basin and Pacific Northwest region.

WATER TEMPERATURE DATA FOR LOWER SNAKE AND COLUMBIA RIVERS

Introduction to the water temperature data:

• The Hot Water Report provides bi-weekly updates on real-time water temperatures in the lower Snake and Columbia River reservoirs. We track water temperatures in all eight reservoirs in the lower Snake and Columbia rivers to understand the river conditions that salmon and steelhead must migrate through.
• The daily average and high water temperature data at the eight reservoir forebays are measured with sensors stationed at various depths below the reservoir surface, immediately upstream from the dams.

LOWER SNAKE RIVER WATER TEMPERATURE DATA 8/29 - 9/14

Click here to view the lower Snake River water temperatures - 2025 Daily Average and 10-year Average.

Average water temperature: Between August 29 - September 14, the highest daily average temperature across all four lower Snake reservoirs was at Ice Harbor reservoir, averaging 71.47°F. 

Highest water temperature: Lower Granite Dam’s reservoir registered the highest water temperature of 71.73°F on September 7.

Total days above 68°F in the lower Snake River: Ice Harbor reservoir has been above 68°F for 74 consecutive days.

LOWER COLUMBIA RIVER WATER TEMPERATURE DATA 8/29 - 9/14

Click here to view the lower Columbia River water temperatures - 2025 Daily Average and 10-year Average.

Average water temperature: Between August 29 - September 14, John Day reservoir had the highest daily average temperature at 73.76°F.

Highest water temperature: The John Day reservoir registered the highest water temperature of 74.30°F on 9/6.

DISCUSSION OF DATA: 

Many of the reservoirs behind the lower Snake and Columbia River dams have experienced over 70 days of water temperatures exceeding the 68°F “harm threshold” set to protect migrating salmon and steelhead. All lower Columbia and Snake river reservoirs have reached temperatures of at least 70°F - 72°F, with temperatures as high as 73°F - 74°F in the lower Columbia River. The dams and their reservoirs are heating much of this river system, making it difficult and/or impossible for adult salmon and steelhead to safely migrate to their spawning grounds, and for summer-migrating juvenile fish to reach the ocean.

Salmon and steelhead are highly resilient. They can tolerate episodes of warm water, but they also have limits on how long and how much hot water they can withstand. The cumulative impact of hot reservoirs in the lower Columbia and the lower Snake must be addressed quickly - to reduce water temperatures and the overall exposure time for these fish to waters above 68°F.

In a recent Lewiston Tribune article, Joe DuPont, regional fisheries manager for the Idaho Department of Fish and Game, stated steelhead and fall chinook appear to be waiting for water to cool in the Snake River before moving further upstream. Fish are passing dams on both the Columbia and Snake rivers, but some fish appear to be reluctant to enter the Snake. “Once it cools down, we think there will be a pulse of fish coming [to Idaho],” DuPont states.

An effective collaboration between the Northwest states, the federal agencies, and Tribal Nations is urgently needed to address rising water temperatures across the basin. Restoring a free-flowing lower Snake River is one essential piece of this puzzle. It will provide a critical cold-water refuge that salmon and steelhead have historically relied upon to rest and recover during their long upstream migration. A freely-flowing river - rather than stagnant reservoirs - will remain much cooler through the summer, especially with cold water infusions released from the Dworshak Reservoir upstream on a tributary to the Clearwater River near Lewiston, ID. With a restored lower Snake River, its significantly cooler waters will extend 140 miles downstream - from the town of Lewiston to its confluence with the Columbia River in south-central Washington State near the Tri-Cities.

Toxic water in the lower Snake River

Left photo: Lower Snake River aquatic fish in toxic algal blooms near Clarkston, WA. Right photo: Toxic algal blooms in the lower Snake River near Lower Granite Dam. © Scott Putnam / Bluz River Production, 2025

The lower Snake River continues to test positive for microcystins, a toxin that harms the liver and is commonly responsible for human and animal poisonings, and habitat degradation.

On September 4, Whitman County Public Health issued another Health Advisory after a water sample tested positive for microcystins at Wawawai Landing in the Lower Granite Dam’s reservoir. The toxic algal blooms can be found intermittently today between the Little Goose Dam and Lower Granite Dam.

Below are confirmed toxic algal blooms present in the lower Snake River and Snake River region and health advisories:

TOXIC ALGAL BLOOMS IN THE LOWER SNAKE RIVER

Lower Granite Reservoir (at or near):

• Nisqually John Landing - Whitman County Public Health’s Advisory (water sample taken on 8/18/25)
• Rice Bar (Snake River) - Garfield County Public Health’s Advisory (water sample taken on 8/26/25)
• Wawawai Landing - Whitman County Public Health’s Algal Bloom webpage (water samples taken on 9/2/25 and 9/8/25)

TOXIC ALGAL BLOOMS NEAR THE CONFLUENCE BETWEEN LOWER COLUMBIA AND SNAKE RIVERS

McNary National Wildlife Refuge:

• McNary Slough - Walla Walla County Department of Community Health (water sample taken on 8/25/25)
• McNary Slough - Walla Walla County Department of Community Health (water sample taken on 9/2/25)
• Casey Pond - Walla Walla County Department of Community Health (water sample taken on 9/2/25)

TOXIC ALGAL BLOOMS IN THE SNAKE RIVER

Snake River (between Oregon and Idaho):

• Brownlee and Hells Canyon Reservoir - Idaho Department of Health & Welfare (water sample taken on 7/23/25)
• Eagle Bar (Hells Canyon) - Idaho Department of Health & Welfare (water sample taken on 8/14/25) 

Restoring a free-flowing lower Snake River to benefit the ecosystem, wildlife, communities, and economy 

We have a once-in-a-lifetime opportunity to lead the largest salmon and river restoration in history, bolster the Northwest economy, and modernize our infrastructure by replacing the services of the lower Snake River dams. With strong political leadership and strategic investments, we can restore a free-flowing lower Snake River, recover salmon, steelhead, and orca populations, uphold our nation’s commitments to Northwest Tribes, and affordably, efficiently, and urgently replace the services currently provided by the four lower Snake River dams.

In the remainder of this issue of the Hot Water Report, we’ll cover the importance of salmon recovery and how the restoration of the lower Snake River would support the recreation economy, and the benefits of service replacement would better serve the needs of communities, ratepayers, and businesses throughout the Columbia and Snake River Basin.

RECREATION OPPORTUNITIES IN A RESTORED LOWER SNAKE RIVER:

• Restoring the lower Snake River to recover salmon, habitat, and provide a safer river to enjoy: The lower Snake River dams and their reservoirs have transformed a healthy, living river into stagnant, hot water reservoirs, creating conditions where toxic algal blooms are now a yearly occurrence. The lower Snake River is becoming a hazardous place for wildlife, pets, and people to enjoy and connect with this historic river. A restored river would recover 140 miles of river, re-create salmon spawning habitat, lower water temperatures, dramatically reduce the incidence of toxic algal blooms, and support a healthier Snake River overall – one that benefits fish, people, communities, watersheds, and cultures.
  • Restoring habitat for native fish, plants, and wildlife, and for people to recreate: A healthy Snake River and abundant salmon will provide new habitat for native fish, plants, and wildlife. A flourishing ecosystem will bring and support a vibrant outdoor economy, drawing hunters, anglers, birdwatchers, and other wildlife viewers from the Northwest and beyond. A free-flowing and clean river will bring new opportunities to camp in the lower Snake River, explore over 60 named rapids, and enjoy activities such as whitewater rafting, canoeing, and kayaking. This has the potential to support the only multi-day river adventure in Washington State.
  • Recovering historical and cultural areas in the lower Snake River: People have lived in the lower Snake River region for more than 12,000 years, and restoring the free-flowing river would uncover Indigenous villages, burial grounds and archaeological sites, as well as recreation areas and important wildlife habitat that have been flooded by the dams and their reservoirs. The Snake River is central to four National Park Service units, including the Lewis & Clark National Historic Trail and Nez Perce National Historic Park. With a restored river, these park units will create avenues to highlight protected and important Indigenous cultural sites, additional storytelling, and enhanced recreation. 

• Columbia Basin recreational salmon & steelhead fishing fuels the Northwest economy: The four lower Snake River dams and their reservoirs have helped decimate salmon and steelhead runs, causing emergency fishing closures and reduced fishing opportunity on the Columbia and Snake Rivers and their tributaries. These closures have had significant impacts on the sport and Tribal fisheries—threatening many businesses and Tribal communities’ ways of life. When emergency fishing closures can occur at a moment's notice, it makes it more difficult for businesses to book clients to fish and reserve flights and hotels. Just earlier this week, fisheries officials raised the possibility of having to increase regulations for fall chinook due to “exceptionally high” river temperatures slowing the run.
  • Columbia Basin sportfishing industry consists largely of small, often family-run businesses, produces around $3 billion in economic development annually, and acts as a reliable transfer of wealth from urban to rural areas.
  • Fishing licenses in the Columbia Basin: There are more than half a million people who have purchased a license to be able to fish for salmon and steelhead in the Columbia Basin.
  • Recreational anglers made 539,214 trips for salmon and steelhead in 2022 on the mainstem Columbia and Snake Rivers, from the mouth into Idaho. This fishing activity pumped $49.6 million into the Northwest’s economy.
  • Healthy and harvestable salmon provide stability for fishing businesses and tourism: If salmon and steelhead populations were restored to healthy, harvestable abundance, the Northwest Sportfishing Industry Association anticipates angler trip values in the mainstem and into Idaho could grow to $124 million or more annually. Angler trip value is money spent in a day; this does not include boats, motors, trailers, rods, reels, or any of the big durable goods that are used. The estimate of $124 million of angler trips is really the tip of the iceberg in terms of what the economic benefits are to the rural communities across the Northwest.

REPLACING HYDROPOWER IN THE LOWER SNAKE RIVER:

• The Northwest is undergoing a rapid energy transition to meet our region’s energy needs and climate goals – and address the escalating pressure of climate change. Climate change is affecting air temperatures, precipitation, snowpack, and wind patterns in the Northwest and, in turn, increasing land and river heat waves, droughts, and variations in river-flow patterns. The lower Snake River dams are “run-of-river” - they do not store appreciable amounts of water and thus only generate electricity when water is available flowing down the river. In the lower Snake River, recent climate trends show a significant reduction in river flows, due to increased drought and reduced snowpack. This is limiting the power and capacity functions - and value - of these dams. 
  • Lower Snake River hydropower is declining: Bonneville Power Administration (BPA) (a federal agency that markets lower Snake River power to utility customers, including public utility districts in the region) in most years publishes their Pacific Northwest Loads and Resources Study, a document showing energy outputs of various dams and showcasing BPA’s and the region’s ability to meet loads under different conditions and time periods. For the lower Snake River dams, BPA shows the forecast of energy output under average or median water conditions. That forecast has changed dramatically over the last decade:
    • 2016 — 1078 aMW
    • 2018 — 1032 aMW
    • 2019 — 933 aMW
    • 2022 — 888 aMW
    • 2024 — 784 aMW
    • 2025 — 676 aMW
    • Power generation from the four dams has declined for years and will continue to decline as climate change and drought reduce snowpack and river flows, and in addition to the spill program.
  • Lower Snake River hydropower generates the least when the region needs it the most: The lower Snake River dams and the lower Columbia River dams are effectively two separate energy systems. The lower Snake River dams produce the most power from March to June, when the rest of the system is also generating significant output—often in excess of customer demand. The lower Snake River dams produce significantly less power when the region needs it the most - for heating in the winter and cooling in the summer.
  • Cost of maintaining the dams: The lower Snake River dams are aging and have passed their 50-year life expectancy. In order to keep them running, these dams will require 21 new turbines in the coming decade. This maintenance is expected to cost nearly $1 billion. Mitigation for the decline of salmon has cost over $26 billion over the past three decades and will continue to increase if the dams remain in place. Replacement of the lower Snake River dams’ services will improve our energy system, provide more output in summer and winter, when power is most needed, and result in better year-round reliability and higher system value to the region.

• Replacing the lower Snake River dams is an energy resiliency approach: The energy services of these four dams are replaceable with affordable, clean, and reliable alternatives:
  • A portfolio of clean energy alternatives will help to modernize our energy grid and improve certainty and reliability in the face of a changing climate and an evolving energy market, all while maintaining affordability for ratepayers. BPA must modernize its energy services with renewed focus on energy efficiency, demand response, wind, solar, battery storage, and transmission. 
  • Diverse renewable energy saves money: Studies have shown that replacing the lower Snake River dams' hydropower with clean energy sources is feasible and cost-effective. Replacing hydropower with a mixed renewable energy portfolio would generate power at times when the region needs it most, resulting in $69- $131 million per year of energy value above and beyond what the lower Snake River dams provide for the same time period. 
  • Cost of renewable power continues to decrease: The cost of building clean, renewable power (wind/solar/battery) has fallen 50% over the past five years and has led to the development of thousands of megawatts of new renewable power and battery storage. Recent requests for proposals (RFPs) from investor-owned utilities for development of clean energy resources have drawn responses providing three to five times the amount of power requested by the utilities.² We have more clean energy resources available to replace the energy generated by the lower Snake River dams.

IRRIGATION IN A FREE-FLOWING LOWER SNAKE RIVER:

• The Ice Harbor reservoir provides irrigation to 53,000 acres of farmland. Notably, there are only nine landowners who manage 92% of the irrigated land, including the LDS Church, Crown West Realty, and Harvard, among others.¹ Comprehensive planning will ensure that the irrigation services provided by the Ice Harbor reservoir will be fully accounted for as the Northwest makes the transition to a free-flowing Snake River. Agricultural regions throughout the country irrigate from freely flowing rivers, and it can also be done for the lower Snake River Basin.

• Water supply planning in the lower Snake River: We can plan for, upgrade, and modernize irrigation systems to continue important agricultural production without relying on salmon-killing reservoirs. A groundbreaking report in 2024 from the Bureau of Reclamation and Washington Department of Ecology outlined the most comprehensive and inclusive plan yet for addressing the water needs of farmers, communities, and ecosystems along the lower Snake River. The report prioritizes Tribal treaty rights and interests, providing clear evidence that a free-flowing lower Snake River is compatible with the region's agricultural and municipal water demands. It makes clear that with the right investments, water users can draw water from a restored river while ensuring salmon populations have a chance to recover from the brink of extinction.

  Key Findings from the 2024 water supply study:

  • Honoring Treaty Rights: Restoring a free-flowing river upholds Tribal treaty rights, revitalizes salmon, and restores traditional fishing areas essential to Tribal cultures and livelihoods.
  • Water availability: Sufficient water exists in a free-flowing Lower Snake River to meet all current agricultural, municipal, and industrial needs year-round, even under low-water scenarios. The report provides clear evidence that there would be plenty of water in a free-flowing lower Snake River to support farmers, cities, and industries.
  • Economic contributions: Farms using lower Snake River irrigation directly contribute nearly $637 million in gross revenue annually to the regional economy.
  • Groundwater resilience: 90% of groundwater wells will remain operational after dam removal, with the remainder requiring deepening or replacement. 
  • Replacing irrigation infrastructure: The report identifies practical solutions for replacing irrigation infrastructure and ensuring uninterrupted water access. Each solution considered had to be technically feasible, able to be constructed and operational before dam breaching, to avoid environmental, cultural, social, and water availability fatal flaws, and to make economic sense. With smart investments and planning, we can continue to use water from the Snake River for agriculture while also restoring salmon and steelhead populations, honoring treaty obligations, and healing our ecosystems.

TRANSPORTATION IN THE LOWER SNAKE RIVER REGION:

• Barging on the lower Snake River: The lower Snake River dams were built with the intention of transforming Lewiston, ID into a vibrant seaport. However, this vision did not come to fruition, and over the last several decades, barging has been in steep decline. The Washington State Department of Transportation (WSDOT) released a Phase 1 status report on transportation in the lower Snake River region. The report confirmed:
  • Barging on the four lower Snake River dams has declined over the years. The primary use of Snake River barges is to move wheat downriver. Fertilizer components also ship upriver, and some wood pulp moves from Lewiston to Portland. Products like paper, pulp, petroleum, lumber, dried peas, lentils, and garbanzo beans are no longer shipped by barge on the Snake River.
  • Rail has the capacity to absorb increased traffic: Rail lines through the Columbia Gorge likely have the capacity to handle additional freight. Some commodities will continue to ship by barge on the lower Columbia River, ensuring multimodal freight options remain available. Most Washington wheat (67%) arrives at the deepwater ocean ports at the mouth of the Columbia by rail. 17% of the wheat exported from those ports arrives via Snake River barge. The area near the Snake River that ships wheat by barge previously shipped their wheat by rail before the dams were built. We can (re)establish grain elevators and rail closer to wheat farms, reducing truck miles and costs to farmers.
  • Trucks are an important part of moving grain and fertilizer today and will continue to be in the future, but infrastructure upgrades are needed: Every grain of wheat leaves the farm on a truck and will continue to do so in the future. While roads in the Palouse region largely have the capacity, the report shows the surface and bridge upgrades that will be necessary. Future phases of the study will analyze how road usage may shift with new or expanded rail elevators and terminals.
  • Port terminals near the Columbia River confluence will remain open: Ports downstream of Ice Harbor Dam will continue to operate even in a restored lower Snake River. According to the U.S. Army Corps of Engineers, navigation in this area can remain open with adequate dredging.

    By investing in rail infrastructure, upgrading roads, and leveraging multimodal transportation options, we can ensure a thriving agricultural industry and a restored river for future generations.

As the dams continue to age, maintenance costs are increasing. It would be a better use of limited time, resources, and taxpayer dollars to invest in replacing the services of the four dams with modern, more resilient energy, irrigation, and transportation systems. If we act quickly, we can restore healthy and abundant Columbia-Snake River salmon and steelhead, honor treaty obligations, and heal ecosystems - and invest in our economy - by replacing the services and breaching the four federal dams on the lower Snake River.

READ PAST ISSUES OF THE HOT WATER REPORT

Data Sources: The 2025 water temperature data for the lower Snake River and lower Columbia River presented in the Hot Water Report are collected from the USGS, and the Columbia River DART program by Columbia Basin Research, University of Washington, with data courtesy of the U.S. Army Corps of Engineers (USACE). These data temperatures are provisional. 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. Graphs and tables are assembled by SOS Staff.

Article sources: 

1. Agricultural Land Use (WSDA, 2019), Irrigated Lands (Franklin Co. Conservation District, 2019; Reclamation, 2020.
2. Columbia Snake River Campaign Factsheet and Frequently Asked Questions.