Welcome to Save Our wild Salmon’s Hot Water Report 2020, Week 8, our final issue of the summer! This summer we’ve reported on weekly conditions on the lower Snake and Columbia rivers - such as water temperatures, status of salmon and steelhead returns and related topics - via graphs, analyses, and stories. Federal dams and reservoirs harm struggling native fish populations, an effect that is exacerbated by warming waters and a changing climate.
We’ve heard from scientists, anglers, guides, and salmon and river advocates about the status of returning adult salmon and steelhead and the challenges facing their rivers. We've explored opportunities for rebuilding abundant, resilient populations, as well as the many benefits they deliver to Northwest culture, economy and ecology.
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. Today, however, these fish are in crisis - 13 populations in the Basin face extinction - endangering jobs, communities, and wildlife populations. The region’s critically endangered Southern Resident orca, for example, depend mainly on chinook salmon for their diet. As salmon abundance has decreased in Northwest coastal waters - and especially Snake River spring chinook - the orca population has crashed. Just 72 individual whales remain today.
The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Washington Sierra Club, Columbia Riverkeeper, Idaho Rivers United, Idaho Wildlife Federation, Snake River Waterkeeper, Northwest Steelheaders, Orca Conservancy, Idaho Conservation League, Defenders of Wildlife, Pacific Rivers, the Natural Resources Defense Council, American Rivers, and Friends of the Clearwater.
II. READING THE DATA (through September 31st)
The daily mean temperature at the forebay (upstream reservoir) of each dam is represented in the solid lines and the 10-year average (2010-2020) for each reservoir is represented by the dashed line of the same color. The dotted line across the top of the graph represents the 68°F survival threshold for salmon and steelhead. These fish 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 these effects, including: increased metabolism (energy expenditure), increased susceptibility to disease, reduced fecundity or reproductive potential, and/or death.
Temperatures in 3 out of the 4 lower Snake River reservoirs currently remain above 68°F. Lower Granite Dam’s reservoir registered below the 68°F threshold three times this week. This is not uncommon for this reservoir as it receives cold water input from Dworshak reservoir on the Clearwater River. There is also less fluctuation this week, which is seen on the graph above. In previous weeks, the temperatures were a couple degrees above the 68°F threshold, but this week those temperatures have decreased slightly. Similarly to last week, the temperatures in the reservoirs are above the 10-year average for this time of year by at least one degree. At this point, we expect the current temperatures reflected in the graph to continue for the next several weeks, and then begin to cool toward the middle of September. So far this summer, three of these four reservoirs have exceeded 68°F this summer for at least 41 days. Lower Granite Dam’s reservoir has exceeded 68°F 15 days this summer.
Similar to the lower Snake River dams, temperatures in all four of the lower Columbia River reservoirs have recently flattened out above 68°F. All reservoirs continue to exceed 68°F by between one and three degrees; this will probably be the case through the middle of September. The Columbia River reservoirs are fairly similar to the 10-year average for this time of year, however some are below by at least one degree. All four reservoirs have now exceeded 68°F this summer for at least 42 days.
III. WEEKLY HIGH TEMPERATURES: 8/25-8/31
On the lower Snake River this week, the reservoir created by Ice Harbor Dam registered the highest temperature at 71.06°F - significantly above the level that coldwater fish require. All reservoirs registered above 68°F this week by at least one degree, however Lower Granite dropped below this threshold for 3 days this week.
On the lower Columbia River, the John Day Dam registered the highest temperatures this week at 70.88F, with the Dalles Dam (70.7F) and Bonneville Dam (70.52F) close behind. All four of the reservoirs on the Columbia River exceed 68°F as it has been in the last few weeks.
Temperature data included in these reports come from the USGS Current Conditions for Washington State. Graphs and tables were assembled by SOS Staff.
IV. Final 2020 Summer Hot Water Report
This report is the last of this summer, however that does not mean the water temperatures are decreasing below the threshold right now. The water temperatures will continue to be above 68°F as long as the warm weather remains. Hot water impacts animals (both aquatic and non-aquatic) as well as human communities that rely on these fish and wildlife. Already endangered salmon and steelhead populations are struggling to survive because of hot water in these reservoirs, affecting human communities as well as wildlife like Southern Resident orcas, bears, and the ecosystem as a whole. Restoring the Lower Snake River is an essential part of a larger regional solution that restores the Northwest’s native fish, helps feed starving orcas, invests in communities and sustains a clean, reliable and affordable energy system.
Links to further information:
Bend Bulletin guest column: Let's heal our rivers and restore salmon
Register Guard Guest Opinion: A Failure to Save the Salmon
The Columbian guest opinion: Snake River dams too costly
Past Hot Water Reports are archived here: Hot Water Reports - Compiled