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Tackling the Climate Challenge


Issue 2 - July 12, 2019

Welcome to the Snake and Columbia River Hot Water Report, Week 2. This weekly report during Summer 2019 will present conditions - including water temperatures and status of salmon and steelhead returns - on the lower Snake and Columbia rivers via graphs, analyses, and stories. The harmful effects on struggling fish populations caused by federal dams and their reservoirs is now being exacerbated each year due to our warming, changing climate.

Each week’s report will give an update on water temperatures in the lower Snake and Columbia River reservoirs, the highest weekly temperature of each dam, and the status of adult returns for each species as they make their way back toward their natal spawning grounds. We’ll also hear from scientists, tribal fishers, fishing guides, and salmon and river advocates about challenges facing the Columbia and Snake rivers - and the opportunities to improve their health and begin to rebuild healthy, resilient fish populations and the many benefits they deliver to Northwest culture, economy and ecology.

If you are unfamiliar with the location of the lower Snake and Lower Columbia rivers and their dams, find them on this map.

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

The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Idaho Rivers United, Idaho Conservation League, Sierra Club, Friends of the Clearwater, Columbia Riverkeeper, Pacific Rivers, American Rivers, and Natural Resource Defense Council.


The daily mean temperature at the forebay - the upstream side of each dam - is represented with solid lines, while the 10-year average (2009-2019) for each reservoir is represented by the dashed line of the same color. For this initial report, 10-year historic data was only available for 4 of the 8 dams we will be monitoring. Finally, the dotted line across the top of the graph represents 68° - the upper end of “comfort zone” for juvenile and adult salmon. 


Over the past week, temperatures have begun to even out across the lower Snake River. As central Idaho snowpack melts, the typically cooler, upstream reservoirs begin to resemble the more downstream reservoirs (see below summary on the Columbia Riverkeeper report for more information). Note that Little Goose dam has already peaked above the 68° threshold, the first of any in the system this year.


The Columbia River dams continue to climb and all have converged within 0.5° of each other this week. Although not as significantly as in mid-June, Bonneville and McNary dam are still continually registering daily temperatures above the 10 year average.



Little Goose, the second dam on the Snake River when moving east from the Columbia, has already had 2 days above 68°. Meanwhile, the entire Columbia River system had its hottest day on July 10th, with all dams reaching temperatures 1° or less below 68 degrees.

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

FEATURED FISH: Summer Chinook


ESA recovery goal is 80,000 wild origin spring/summer chinook to Lower Granite Dam for 8 consecutive years.

*Wild salmon numbers are calculated as a proportion of total returns  

While “spring” and “summer” chinook salmon are grouped together under the Endangered Species Act, they are counted separately by the Fish Passage Center. It is crucial that in looking at the data we recognize that wild salmon make up a smaller portion of the total return every year, with hatchery-origin fish constituting over 80% of the run in some years. (See Issue 1 of the 2019 Hot Water Report for information on spring chinook).

Salmon.ChinookSummer chinook begin to return to the Snake and Columbia basin in mid-June, with the termination of the run in late July. Like spring chinook, these fish can be a major food source for endangered Southern Resident orcas. Snake River summer-run chinook salmon spawn approximately one month later than spring-run fish and tend to spawn lower in elevation, although their spawning areas often overlap with those of spring-run spawners. 

Typically, just 8% of summer chinook that pass Bonneville Dam make it through the river system to Lower Granite Dam on the lower Snake. Furthermore, summer chinook returns to Lower Granite are just half of what they were at this time last year. These ong-migrating fish already face difficult navigation through fish ladders and predators in their homeward migration. Even under perfect conditions, this is a trying journey. As water temperatures rise above levels suitable for salmon, deleterious health impacts further increase salmon mortality along their journey.  

COLUMBIA RIVERKEEPER REPORT: Removing dams will reduce lower Snake River water temperatures

In 2015, extreme water temperatures driven by hot weather and a low snowpack killed more than 250,000 salmon in the Columbia and Snake rivers. This incident of mass mortality inspired SOS member organization Columbia Riverkeeper to publish a report that evaluated what the water temperatures of the lower Snake would have been during the summer of 2015 if its four federal dams did not exist.


Using an earlier EPA water temperature model, Columbia Riverkeeper found that each of the four reservoirs behind the dams increase the river temperature by about 2 °F. The reservoirs create large, stagnant water pools which steadily absorb heat from the sun. When waters from one reservoir move downstream to the next, these already warmed waters are stopped once again by the next dam and continue to heat up. The model indicates clearly that this effect would be absent from free-flowing lower Snake River.

A reservoir-free lower Snake River flows freely and does not absorb the same amount of solar radiation. Considerably cooler waters deliver big benefits to migrating juvenile and adult salmon and steelhead populations – leading to increased survival and reproductive success. A free-flowing lower Snake River also has the additional benefit of cold waters that are released from behind the Dworshak reservoir upstream on the Clearwater River in the hot summer months.

Dams.Dworshak.SnakeThe Dworshak reservoir collects cold snowmelt from high in the mountains of central Idaho and stores it in a deep, cool reservoir. An important operation of Dworshak dam today is to deliver cold water into the Clearwater River, which then enters the Snake River near Lewiston, Idaho. As long as the dams remain in place, the benefits of Dworshak’s cold flows are limited to this one reservoir behind Lower Granite dam near Lewiston (ID) and Clarkston (WA). However, as water incrementally warms behind each reservoir, the cold-water benefits from Dworshak are quickly lost.

Today, the lower Snake River routinely suffers weeks and/or months of hot water with temperatures  above – and often well above - 68°F (the upper end of the comfort zone for coldwater fish like salmon and steelhead). However, by restoring this 140-mile stretch of river through dam removal, models in the Columbia Riverkeeper report show that while temperatures in a freely flowing river may spike above 68 degrees periodically, they will quickly return to cool temperatures that salmon and steelhead need to survive and thrive. Cold summer flows from Dworkshak further help keep temperatures healthy for fish all the way downstream to where the Snake River joins the Columbia River in south-central Washington State near the Tri-Cities.

In summarizing findings of the study, Miles Johnson, senior attorney at Columbia Riverkeeper, notes that, "removing the four Lower Snake River dams would keep the river cooler and help salmon reach their spawning areas. This is critical for healthy salmon and a healthy river – especially as the changing climate tightens its grip on our waters in the Northwest. It's time for bold action to protect the Northwest's fishing traditions, orcas, and salmon. It’s time to restore the lower Snake River." 

A 2016 court ruling that invalidated the federal government’s latest Columbia-Snake salmon plan as inadequate and illegal highlighted, among other things, the government’s failure to account for the growing impacts of a changing climate on the already endangered wild salmon and steelhead populations of the Snake and Columbia rivers. Federal agencies in charge (Bonneville Power Administration, Army Corps of Engineers, NOAA-Fisheries) have consistently failed to develop any effective strategy to maintain cool, salmon-friendly water temperatures in these reservoirs in summer months. And, there is no evidence today that the government’s next plan – required by law, ordered by the court and now in development – will address these temperatures issues either.


Idaho Fish & Game: Very few sockeye salmon returning to Idaho (July 9, 2019)

CBB: Treaty Fishing To Begin For Summer Chinook, Sockeye; Run Forecasts Down From Last Year’s Actual Returns (June 12, 2019)

CBC: Southern resident killer whales last seen in poor health now missing (July 9, 2019)

Previous Links:

Lewiston Morning Tribune: Spring Chinook Season Comes to a close (June 5, 2019)

Seattle Times: Chinook bust on the Columbia - Spring returns worse than forecast on Northwest’s largest river (May 30, 2019)

Seattle Times: Washington State to Regulate Federal Dams on Columbia, Snake to Cool Hot Water, Aid Salmon (January 31, 2019)

Seattle Times: Hunger, the Decline of Salmon Adds to the Struggle of Puget Sound’s Orca (February 24, 2019)

Past reports are archived here: Hot Water Reports - Compiled

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