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SOS Blog

Save Our Wild Salmon

Hot Water Report 1


Welcome to Save Our wild Salmon’s Hot Water Report 2022.

During the summer, this weekly report will provide an update on real-time water temperatures in the lower Snake and Columbia River reservoirs via graphs and analyses, a summary on the highest weekly water temperatures at the forebay/reservoir of each dam, and the status of adult returns for different salmon and steelhead populations as they make their way back to their natal spawning grounds. We’ll hear first-hand from scientists, Tribal members, fishing guides, advocates, and other experts about challenges facing the Columbia and Snake Rivers - and our opportunities to improve and restore them - in order to recover healthy, resilient fish populations and the benefits they deliver to the Northwest’s culture, economy, and ecology.

The once-abundant anadromous fish populations of the Columbia-Snake River Basin are struggling to survive today in large part due to multiple harms caused by the system of federal dams and 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. 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 fecundity or reproductive potential (by reducing egg viability), suffocation (warm water carries less oxygen), and in the worst case - death.

These harmful hot water episodes above 68°F in the Columbia and Snake Rivers are increasing in duration, frequency, and intensity. Our changing climate is making a bad situation for the Northwest’s iconic fish worse. Our region and nation must take urgent action to maintain cool water temperatures - or we will lose these species forever. Restoring a freely flowing lower Snake River by removing its four federal dams is likely our only option to address high water temperatures in this 140-mile stretch of river running through southeast Washington State. Restoring the Snake River is one essential element of what must be a larger regional strategy to protect and rebuild healthy, abundant salmon and steelhead populations in order to benefit other fish and wildlife populations, including critically endangered Southern Resident orcas, to uphold our nation’s promises to Native American tribes, and to ensure prosperous communities across the Northwest.

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Columbia RiverkeeperAmerican Rivers, Endangered Species Coalition, Environment Washington, Idaho Conservation League, Idaho Rivers United, Idaho Wildlife Federation, National Resource Defense Council, National Wildlife Federation, Nimiipuu Protecting the Environment, Northwest Sportfishing Industry Association, Sierra Club, Snake River Waterkeeper, and Wild Steelhead Coalition.

II. READING THE DATA - Lower Snake and Columbia River Temperatures

The daily mean temperature at the four reservoir forebays (immediately upstream from the dam) in the lower Snake River (above) and the lower Columbia River (below) for 2022 is represented with solid lines and their 10-year average (2012 - 2022) 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. Salmon and steelhead begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit. The longer temperatures remain above 68°F and the higher the temperatures rise above 68°F, the more severe the potential effects, including: increased metabolism, increased susceptibility to disease, reduced fecundity or reproductive potential, and/or death.

Since April, temperatures in the lower Snake River and the lower Columbia River reservoirs have steadily moved upward. During April and May, trends have tracked closely with the 10-year average. In June, however, water temperatures have dropped considerably below this average. This is good news for cold-water species like salmon and steelhead, though we expect these temperatures will rise considerably in these reservoirs as the summer progresses. The reservoir behind the Little Goose Dam had the highest mean temperature of 55.76°F and Ice Harbor Dam’s reservoir had the second highest mean temperature of 55.22°F. A note on data information: The mean water temperature data from these reports comes from the USGS Current Conditions for Washington State and the 10-year average water temperature data comes from the Fish Passage Center. There is no available data for Lower Monumental 10-year average water temperature. Graphs and tables were assembled by SOS Staff.


On the lower Snake River this week, the reservoir behind the Little Goose Dam registered the highest temperature at 56.66°F, followed closely by Lower Granite and Lower Monumental reservoirs with 56.66°F.

On the lower Columbia River, the reservoir behind the Bonneville Dam registered the highest temperature at 57.92°F. The second highest temperatures came from the reservoirs behind The Dalles Dam and the John Day Dam with a temperature of 57.56°F.

IV. How the Snake and Columbia river reservoirs harm endangered salmon and steelhead populations.

Historically, abundant Snake and Columbia River salmon and steelhead delivered vast cultural, economic, nutritional, and ecological benefits to the people and fish and wildlife of the Pacific Northwest. Not long ago, the Columbia Basin would annually see millions of adult salmon and steelhead swimming back from the Pacific Ocean. Chinook, or King salmon, are the largest and richest of the salmonid species. They are also the primary food source (roughly 80 percent of their diet) of endangered Southern Resident orcas. Columbia Basin chinook can spend up to five years in the Pacific Ocean before they return to freshwater to spawn.

Today, however, these fish are in crisis - thirteen Columbia Basin populations are at risk of extinction. The dams and their reservoirs harm and kill salmon and steelhead in numerous ways, including by elevating water temperatures. This situation is being made worse - and the need for meaningful action more urgent - due to the changing climate. These reservoirs warm water above the temperatures of freely flowing rivers by creating large, slow-moving pools that absorb large amounts of solar radiation. These bodies of water also inundate and destroy diverse micro-habitats that healthy rivers support, including cold-water refuges that salmon and steelhead rely upon during their migration in summer months. When available, these vital pockets of cold water can enable adult (moving upstream) and juvenile (moving downstream) fish to rest and recover before continuing their migration. Rising temperatures and reductions in snowpack in recent decades due to climate change has resulted in lower survival and reproductive success for salmon and steelhead.

Temperature affects salmon behavior, reproduction, and survival. According to the National Wildlife Federation, the optimum water temperature range for most salmon is approximately 55 to 64 degrees Fahrenheit1. While different stocks and species of salmon and steelhead may have different requirements and tolerances, the National Ocean and Atmospheric Administration indicates that Chinook salmon, for example, prefer/require certain water temperatures for all phases of their life history: spawning, egg survival, smoltification, and migration2:

Influence of water temperatures on Chinook salmon spawning and egg incubation:

  • Upstream migration will cease if temperatures are below 3.3°C (37.94°F) or above 20°C (68°F).
  • The majority of spawning may occur between 6°C (42.8°F) and 15 °C (59°F)
  • The optimal temperature range for egg survival is 8°C (46.4°F) to 12°C (53.6°F).
  • The optimal temperature range for development to the alevin (larval stage after hatching before yolk absorption stage) is 4°C (39.2°F) to 8°C (46.4°F)

Influence of water temperatures on smoltification by Chinook salmon:

  • Water temperatures above 14°C (57.2°F) and below 7°C (44.6°F) can cause mortality in fry.
  • High (sub-lethal) water temperatures accelerate growth of fry, but can also result in increased susceptibility to disease.
  • High temperatures can lead to early seaward emigration by influencing physiology.

The lower Snake River dams regularly drive water temperatures above 68°F in the summer for weeks or more at a time. Last year, for example, from June through September, all four lower Snake River reservoirs had waters above 68°F for between 40 to 67 days. The Ice Harbor Dam reservoir registered the highest temperature last summer at 73.22°F on July 18, 2021.

Lower Snake River dam removal will deliver big survival benefits to endangered salmon and steelhead

Columbia Riverkeeper, an SOS member organization, published this analysis - White Paper: Computer modeling shows that Lower Snake River dams caused dangerously hot water for salmon in 2015. This analysis shows how a restored lower Snake River would flow freely, absorb far less sunlight and remain much cooler through the summer. Considerably cooler waters would deliver big benefits to migrating juvenile and adult fish populations – leading to increased survival and reproductive success (more information here).

Currently, we are seeing water temperatures below the 10-year average for this time of year in both the lower Snake and Columbia Rivers due mainly to cool weather and a relatively good snowpack. While salmon returning this spring to spawn are benefiting from these cold water conditions, we expect these temperatures to rise as the summer advances.


The Snake River Basin historically (before the dams) annually produced millions of returning adult salmon and steelhead. It supported nearly half of all the spring chinook that returned to the Columbia Basin overall. Notably, these spring chinook are very important to Southern Resident orcas. Before construction of the dams, they were available as large, numerous, and fat-rich prey for the Southern Resident orcas during the winter months when there are few other fish.

Restoring the lower Snake River through dam removal is our very best river and salmon restoration opportunity anywhere on the West Coast today. Scientists predict it could annually produce between 600K and 1.1M adult spring chinook entering the mouth of the Columbia River in the spring and summer months. Increased adult returns of Snake River sockeye, fall chinook, and steelhead would add significantly to these anticipated numbers.


  1. The National Wildlife Federation: Chinook Salmon
  2. National Oceanic and Atmospheric Administration: The Influence of In-stream Habitat Characteristics on Chinook Salmon (Oncorhynchus tshawytscha) (November, 2002)


 Martha Bio picMartha Campos is the Hot Water Report Coordinator with Save Our wild Salmon this summer while she resides on Kizh/Tongva ancestral lands in California. Martha holds a BA from the University of California, Davis in Native American Studies (and two minors: Environmental Policy, Analysis, and Planning and Climate Science and Policy) and is a queer, non-binary person of color with ancestral roots in Mexico.


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