Rocky Barker concludes (Oct. 8 front page salmon article) that the Snake/Columbia hydroelectric dams act as “giant solar collectors” that helped cause river temps to reach 73 degrees (lethal for salmon) in 2015. He also mentions that the lower Salmon (without dams) rose to 76 degrees that year. Hmm…
Dam pools create a “thermocline effect” in which water temperatures on the bottom are much colder than surface temperatures. The S.F. Boise River below Anderson Ranch Dam (as delighted fly fisherman can affirm) remains frigid throughout the hottest summers because it’s fed from the bottom of the dam pool. Ditto the Owyhee River (below Owyhee reservoir). Both are renowned “tail-race” trout fisheries with miles of year-round ice-cold flows.
Any scientific model that compares Snake/Columbia river temperatures with/without dams must accurately calculate the cumulative thermocline effect on all dams on every river that feeds the Columbia ... otherwise the algorithm is flawed. In other words, removing dams to offset rising river temps associated with climate change may not be the panacea we’re betting on. Once the dams are removed, we lose billions in annual “salmon survival mitigation funds” that power companies currently pony up – along with the gargantuan loss in cheap, carbon-free hydroelectricity.
Michael Howard, Boise