Last week the Oregon Chapter of the American Fisheries Society held their annual meeting in Bend. I attended the 21 presentations on Water & Climate. I’ll make a few posts with highlights and, hopefully, some copies of presentations I have requested. One of the presentations was on the unintended consequences of selective water withdrawal at Cougar Dam on the South Fork of the McKenzie River. There are some interesting analogues to what is happening on the Deschutes.
Like on the Deschutes, a tower has been installed that allows water to be withdrawn at different depths in the reservoir to create a more natural temperature profile (“thermal restoration”) in an attempt to aid downstream fish and salmon migration. Also like on the Deschutes, this entails releasing surface water containing algae and organisms that would not be naturally occurring in the same quantities in the downstream river.
The conclusion from the researcher was one of concern but no negative consequences to downstream fish have been observed. She stated that while the mix of food sources in the river has changed, fish are benefiting from the new temperature regime. She stated that only long term monitoring could determine if surface water discharge would continue to be beneficial or ultimately detrimental to fish.
I asked her what she knew about the Deschutes. She replied that from the reports she had read there has been an increase in worms in the lower river since the SWW has been in operation but that worms are a “yummy” food source for fish. I am really looking forward to the overdue water quality report from PGE/CTWS.
As an aside, I was honored to be awarded the 2018 Award of Merit at this meeting. In the citation they stated that this blog should be required reading for everyone in Central Oregon. I write this blog because I love to fly fish, but it is nice to have some positive feedback from biologists and scientists whose work I respect.