Slide background
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 provides 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 the 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 reproductive potential (by reducing egg viability), suffocation (warm water carries less oxygen), and in the worst case - death.

Today, 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 our only feasible 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 2022 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, Spokane Riverkeeper, Wild Orca, and Wild Steelhead Coalition.

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

Introduction: 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 reproductive potential, and/or death (see Issue 1 for more detailed information).

Discussion: 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 dropped considerably below this average. This was good for cold-water species like salmon and steelhead, but since July, temperatures have reached and exceeded the 68°F “harm threshold” in the reservoirs on the lower Snake and Columbia River. Below, we present the highest temperatures for each reservoir on the lower Snake and Columbia River. 

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.


Harmful water temperatures in the lower Snake River reservoirs: This week, all reservoirs exceeded 68 degrees. The Little Goose Dam reservoir has spent 25 days above 68°F and similarly, the Ice Harbor Dam spent 23 consecutive days above 68°F. The reservoir behind Ice Harbor Dam registered the highest temperature at 71.96°F on August 4th. The waters behind Lower Monumental Dam and Little Goose Dam registered the second highest temperature at 70.34°F.

On the lower Columbia River, all reservoirs peaked over 68°F. The reservoirs behind the John Day Dam and The Dalles dam registered the highest temperature: 71.96°F.

 IV. Salmon and steelhead need healthy oceans and healthy rivers (of course!)

Wild salmon and steelhead are long-migrating fish that spend significant parts of their lives in freshwater and in saltwater ecosystems. The condition of each - saltwater and freshwater - affects fish survival. However, there’s a misleading narrative advanced by defenders of the status quo that ocean conditions, rather than the four lower Snake dams, are the real obstacle to recovering healthy, abundant populations of Snake River salmon and steelhead. This is false - Northwest salmon and steelhead all swim in the same ocean, but the mortality rates they experience in freshwater increase significantly with the number of dams and reservoirs they encounter. Specifically, endangered Snake River salmon and steelhead have to cross eight dams and reservoirs to reach the ocean and then again as they return to their spawning grounds. And these fish suffer from the highest mortality rates, and lowest smolt-to-adult return ratios, compared to other fish that spawn lower in the watershed and encounter fewer dams and reservoirs. 

Salmon and their ecosystems:

Ocean conditions do play a significant role affecting salmon and steelhead survival. When ocean conditions are good (abundant food availability for salmon and steelhead to eat), salmonid survival in the ocean increases, and we see increased survival of juvenile fish as they enter the ocean and increased adult salmon returns back into the Columbia-Snake Basin. When ocean conditions decline (reduced food availability), we often see adult returns (survival) decline too. The ocean has a long-running and well-documented cyclic pattern of good conditions followed by bad conditions. 

It should surprise no one that the condition of freshwater ecosystems also significantly affect salmon and steelhead survival and reproduction. In the Columbia-Snake Basin, the construction of the federal hydro system - the dams and their reservoirs - has profoundly degraded available fish habitat and also profoundly reduced access to historic habitat. The federal hydro system in the Columbia Basin is far and away the largest single source of human-caused mortality for salmon and steelhead. Dams and reservoirs destroy spawning and rearing habitat; they warm waters, slow currents, increase energy expenditures by young migrating fish, significantly increase predation by invasive and other fish that thrive in these stagnant warm-water reservoirs. The more dams and reservoirs that these fish encounter in their life, the greater their mortality. And, importantly, a significant number of dams completely block access to once-highly productive habitat in the Columbia and Snake Rivers and their tributaries.

In a free flowing river, smolts ride the cold current quickly to the ocean. With dams and reservoirs, they need to swim to the ocean. This takes much longer and requires lots of energy that they then don’t have for reserves when they arrive at the ocean, if they arrive at the ocean. This issue of stagnant waters on one more way that dams and reservoirs harm and kill salmon and steelhead.

Dams are the major case of salmon and steelhead deaths:

Wild Spring Chinook Salmon Deaths by Cause

The science demonstrates clearly that salmon and steelhead who live in the same Pacific Ocean have drastically different mortality rates depending on how many dams and reservoirs they encounter on their journey to and from the ocean. Fish who encounter four dams or less return at comparatively higher levels and are far more able to sustain themselves. Salmon and steelhead in the Snake River, however, encounter eight dams and reservoirs and are not sustaining themselves today.

For Snake River fish, the dams and their reservoirs can kill up to 70% of out-migrating juvenile fish before they ever reach the ocean. Since Snake and Columbia Basin salmon and steelhead swim in the same ocean, the cause of the mortality of Snake River fish is not found in ocean waters. The Snake River salmon and steelhead mortality rates increase due to high number of dams - and hot water reservoirs - they must pass.

Smolt-to-Adult Ratios (SARs) decrease as the number of dams/reservoirs fish encounter increase.

Columbia Basin SAR Chinook 2021

How do we know dams are the primary source of mortality for Snake River fish? Let’s look at the smolt-to-adult ratio of these populations. Smolt-to-adult ratio - or SAR - reflects the percentage of ocean-bound juvenile fish that return as adults to spawn in freshwater.

SAR is crucial as it’s the only metric that captures most of the cumulative impacts of the hydro system on salmon and steelhead, telling us how sustainable the returns of adults are over time. This is critical because even if high-quality habitats produce a lot of smolts, the population can only sustain if those smolts can make it out to the ocean and survive to return and spawn as adults at sufficient SAR.1

Before the last three Snake River dams were completed in the mid-1960s (Ice Harbor was in place, as were the Columbia dams), SAR for Snake River spring/summer Chinook salmon ranged from 3.5 to 6.5 percent (average 4 percent from 1964-1968).2 

However, over the last 25 years (after the construction of the lower Snake River dams), SARs for Snake River salmon and steelhead have fallen consistently below 2 percent despite restrictions and closures of modern fisheries, and massive investments in Snake River Basin habitat restoration and juvenile fish passage systems at the lower Snake River dams.2 This decline in SARs below 2 percent represents a trajectory toward extinction because not enough smolts survive to return and spawn as adults.2

Rebuilding Snake River salmon and steelhead populations will require increasing their SAR. The Northwest Power and Conservation Council determined long ago that a SAR of 4 to 6 percent (that is, for every 100 smolts that head out to the ocean, 4 to 6 adults must successfully return to spawn) is needed to recover and maintain healthy, harvestable populations.2 Further, scientists have concluded that removing the four lower Snake River dams allows the fish to consistently achieve 4 to 6 percent SAR.2

Restoring the Snake River and its fish:

While both ocean and freshwater habitat conditions affect salmon survival and recovery, there is one big difference. Our decisions and policies - past, present and future - have a huge influence on the condition of freshwater habitat. By restoring the Snake River through dam removal, we will significantly increase salmon survival in freshwater and significantly decrease mortality caused by the dams and their reservoirs. 

Further, the higher the quality of the freshwater habitat - colder waters, faster currents, less predation, and less dam/powerhouse encounters - the better the condition of young out-migrating salmon and steelhead when they arrive at the ocean. The better condition that juvenile fish are when they arrive at the ocean - whether its conditions are good or poor - the higher the survival of the fish and the higher the eventual returns of adults a few years later.

The science is clear: The four dams on the lower Snake River are the single-biggest source of human-caused mortality for the salmon and steelhead that call the Snake River Basin home. And removing the lower Snake River dams is the single most important action we can take to recover these fish and improve the quality of freshwater rivers and streams and help them survive their time in the ocean - regardless of its condition at any given time.

1. Trout Unlimited: What is a smolt-to-adult ratio and why is it important?
2. Trout Unlimited: Is it possible to recover salmon and steelhead without removing the dams?


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.



Share This