Thursday August 10, 2023

Mendofever Reporting

The public comment period for a proposed reduction in the diversion of water from the Eel River into the East Branch of the Russian River is now closed. PG&E, which still owns and operates the Potter Valley Project, has asked regulators for permission to reduce the flow into the East Branch from 75 cubic feet per second to 25. The utility is also asking for the flexibility to cut the flow to five cfs if the water temperature at a gage near Scott Dam exceeds 16 degrees Celsius. That’s about 60 degrees Fahrenheit, which creates dangerous conditions for juvenile salmon. Last year, only 145 adult steelhead were counted at a fisheries station at Cape Horn Dam, downstream of Scott Dam.

Scott Greacen is the Conservation Director for Friends of the Eel River, which has long fought for the full removal of the Potter Valley Project. On August 1, he reported, “The water coming out of the needle valve right now is 17.44 degrees Celsius. That is already approaching the point where pikeminnow, not native to the Eel, but introduced via the Lake Pillsbury reservoir, begin to out-compete juvenile steelhead. And as water temperatures continue to rise into the 19, 20, 21 degree range, you’ll eventually see mortality of all the juvenile steelhead.”

Water is released from Lake Pillsbury into a stretch of the Eel River from a needle valve at the bottom of Scott Dam, which impounds the reservoir. From there, it makes its way to a diversion tunnel that directs the water to Potter Valley and the Russian River. Due to seismic concerns, the Division of Dam Safety has instructed PG&E to leave a set of gates on top of the dam open all year round, lowering the level of the lake. Initial engineering analysis has indicated that the dam is more susceptible to earthquake damage than was previously known. Lowering the lake level is a precautionary safety measure.

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