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SOS Blog

Save Our Wild Salmon

Hot Water Report 1


Welcome to Save Our wild Salmon’s Hot Water Report 2021. 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 report on high weekly water temperature at the forebay/reservoir of each dam, and the status of adult returns for the different salmon and steelhead populations as they make their way back to their natal spawning grounds. We’ll also hear first-hand from scientists, anglers, guides, advocates, and other experts about challenges facing the Columbia and Snake rivers - and the opportunities we have to restore the healthier river conditions needed to support abundant fish populations and the many benefits they bring to the Northwest’s culture, economy and ecology.

The once-abundant anadromous native fish populations that call the Columbia-Snake River Basin home are struggling to survive today primarily due to harmful effects caused by the system of federal dams and their reservoirs. The federal hydro-system creates conditions that harm and kill both juvenile and adult salmon and steelhead, including by elevating water temperatures in the large, stagnant reservoirs, especially in the summer months. As cold water species, these fish begin to suffer harmful effects when water temperatures exceed 68° Fahrenheit. The longer and higher temperatures rise above 68°F, the greater the harm, including disruption in their migration, increased metabolism, increased susceptibility to disease, reduced fecundity or reproductive potential (by reducing egg viability), and in the worst case - death.

These hot water episodes above 68 degrees 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 lower these high temperatures or we will lose these species forever. Restoring a freely flowing lower Snake River by removing its four federal dams is our best and likely only option for lowering water temperatures in this 140-mile stretch of river in southeast Washington State. Restoring the Snake River is one essential part 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 honor tribal rights, and to ensure prosperous communities across the Northwest.

Will you be on the river this summer? Do you have a story or photo you would like to share? Please send them to Martha Campos

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Washington Sierra Club, Columbia Riverkeeper, Idaho Rivers United, National Wildlife Federation, Snake River Waterkeeper, Northwest Steelheaders, and Defenders of Wildlife.

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 2021 is represented with solid lines and their 10-year average (2011-2021) 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.

A note on the lower Snake River Water Temperature Graph: 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. USGS began recording water temperatures at Ice Harbor and Lower Monumental on June 16, 2021, Little Goose on June 19, 2021, and Lower Granite on June 18, 2021. Although we are not able to compare spring water temperatures to summer water temperatures, we can see the temperatures rising above the 10-year average and all water temperatures in the lower Snake River are above 60°F.

Temperatures in the lower Snake River and the lower Columbia River reservoirs over the last seven days are all trending at or above the 10-year average for this time of year. As we officially enter the summer season, temperatures in the mainstem lower Columbia river, like the Snake, are steadily rising toward the 68 degree “harm threshold” for salmon and steelhead.


On the lower Snake River this week, Lower Granite Dam’s reservoir registered the highest temperature at 65.66°F, followed closely by Little Goose Dam with 65.48°F.

The McNary Dam registered the highest temperature on the lower Columbia River this week at 65.48°F. The Dalles and the Bonneville Dam also registered a high temperature at 65.3°F.

Temperature data included in these reports come from the USGS Current Conditions for Washington State and the Fish Passage Center. Graphs and tables were assembled by SOS Staff.

IV. How the Snake and Columbia River reservoirs impact cold-water species of salmon and steelhead.

Spring.Chinook.Salmon.Print.Klatt.08Historically, 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 experience millions of adult salmon and steelhead that flooded into the Columbia River Basin each year. Chinook, or King salmon, are the largest and richest of the salmonid species. They are also notably the primary food source (roughly 80 percent of their overall diet) of the critically endangered Southern Resident orcas. Columbia Basin chinook can spend five or more years in the Pacific Ocean before they return to freshwater to spawn.

These fish, however, are in crisis - thirteen distinct populations in the Columbia Basin are at risk of extinction today. The elevated water temperatures caused by the reservoirs and made worse by a changing climate must be addressed or scientists tell us we will lose these fish forever. Reservoirs created by these dams warm water above the temperatures of freely flowing rivers by slowing the current and creating large pools that absorb large amounts of solar radiation. These bodies of water 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 fish (moving downstream) 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 endangered salmon and steelhead.

How 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 Fahrenheit. While different stocks and species of salmon and steelhead may have different requirements and temperature 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 migration:

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 occurs 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 temperature above 14°C (57.2°F) and below 7°C (44.6°F) can cause mortality in fry.
  • High (sub-lethal) water temperatures accelerates 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 and Columbia river dams have disrupted the salmon’s life cycle in various ways, including by driving water temperatures past 68°F in the summer for weeks at a time. This week, the dams in the lower Columbia River and the Little Goose and Lower Granite dams in the lower Snake River are reaching the above optimum water temperature range of 55 to 64 degrees Fahrenheit.

Restoring the lower Snake River is our only feasible option for addressing its dangerously high water temperatures. River restoration will also help address other problems created for fish by the dams. It will, for example, significantly reduce predator populations and by increasing current velocity, significantly decrease juvenile salmon migration times to the estuary. All things considered, bypassing the lower Snake River dams is an essential ingredient for protecting salmon and steelhead from extinction and for rebuilding their populations and the many benefits they provide for the people and ecosystems of the Pacific Northwest and nation.


sos.logo1Founded in 1991, Save Our wild Salmon (SOS) is a diverse coalition of organizations working together to secure policies to protect and restore healthy, self-sustaining and fishable populations of salmon and steelhead in the marine- and fresh-waters of the Pacific Northwest. As many as 16 million salmon and steelhead once returned to the Columbia-Snake River Basin annually. Today in the Snake River Basin, all four remaining populations face extinction. The steep losses of this keystone species in the Columbia Basin and across the Northwest has had devastating effects on many communities, cultures, economies and other fish and wildlife populations.


Martha Bio pic

Martha 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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