Welcome to the Lower Snake and Columbia River Hot Water Report, week nine. This weekly report presents the conditions on the Lower Snake and Columbia Rivers via graphs, analyses, and stories. We have been tracking the rivers as they become too hot for migrating salmon, as well as the return of each individual salmon species. Reports will conclude soon, once temperatures settle below 68°.
In 2015, extreme water temperatures killed upwards of 300,000 salmon in the Columbia Basin. Extinction is looming for wild Snake River salmon and steelhead, with myriad threats facing these dwindling stocks. As each salmonid species journeys through the Columbia and Snake, we will highlight its unique attributes and discuss how different species respond to increasing river temperatures. We’ll also hear first-hand from scientists, tribal fishers, guides, and citizens on the Columbia and Snake rivers throughout the summer.
Will you be on the river this summer? Do you have a story or photo you would like to share? Please send them to Jacob Schmidt
If, in the course of your river trips this summer, you come across a dead sturgeon, remember to contact the Washington Department of Fish and Wildlife.
The Hot Water Report is a joint project of the Save Our wild Salmon Coalition, Idaho Conservation League, Columbia Riverkeeper, Idaho Rivers United, Friends of the Clearwater, and Washington Sierra Club.
Check out previous Hot Water Reports here.
READING THE DATA
The daily mean temperature at the forebay (upstream reservoir) of each dam is represented in the solid lines, while the 10 year average (2008-2017) 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° survival threshold for juvenile salmon. The longer temperatures remain above 68° and the farther the temperatures rise above 68°, the more severe the effects, including: increased metabolism, increased susceptibility to disease, reduced fecundity (reproductive potential), and/or death.
If you are unfamiliar with the location of the Lower Snake and Lower Columbia dams, you can find them on this map.
Temperatures at all four of the Lower Snake dams have began to decrease over the last three or four days. Daily highs are still breaking above the 68 degree survival threshold, with the exception of Lower Granite and Little Goose, whose high temperatures measured 67.6° and 67.5° respectively on August 30th. Continuing along last week’s trend, air temperatures have been cooler overall this week. Nonetheless, warm temperatures in the 80’s and occasionally the low 90’s persist. Temperatures at Ice Harbor, the furthest downstream of the lower four Snake River dams, remain the warmest and continue to register well above the 68° survival threshold. Meanwhile, at the forebay of Lower Granite dam - the furthest upstream and most direct recipient of high elevation streamflows - temperatures have begun to dip back below the 68° threshold.
The general trend toward lower temperatures apparent on the lower Snake is also evident on the lower Columbia. Though the temperatures at the forebays of all four dams have begun to dip, they remain above 68°. McNary is the first of the four dams to see days without a daily max temperature above the threshold. Yet, until all daily temperatures remain consistently below 68°, fishing closures will likely continue. Last week’s night fishing closure remains in place, as does the closure at the mouth of the Deschutes.
WEEKLY HIGH TEMPERATURES 8/24 - 8/30
2018 Columbia-Snake Basin Adult Salmon Returns – year-to-date
Chinook arriving at the mouth of the Columbia after August 18 are no longer counted as Summer Chinook, but rather as Fall Chinook. Snake River Fall Chinook have fared far better than Spring/Summer runs, but are still listed as a threatened species. There was talk of delisting the species after the banner year of 2014, in which more than 50,000 chinook returned to the Snake River and its tributaries.
So far, this year’s fall return has been far below average. However, the improvement over 2017 results at this point in the year gives hope that we might see a return to the sort of recovery that was underway in the first half of the decade. These returns are, however in a very early stage. The numbers on the graph above represent less than 30% of the complete run.