In recent years the Feather River was the second largest fall-run spawning zone in the Central Valley after the upper Sacramento. In 2001, 170,000 fall-run fish returned. In 2009, only 3,950 returned then the population somewhat recovered.
In the fall, the salmon are subject to lethal temperatures in the high flow channel from hot water dumped in to the river from the Theramilto Afterbay. This is a man-made, shallow, reservoir built to aid in power generation that heats water. The relicensing of the Oroville Dam by FERC envisioned major improvements in operations for the benefit of salmon. However, relicensing and the improvements have been stalled since 2006 and now are stalled further in the wake of the Oroville Spillway failure of 2017.
This project proposes installation of a cold water bypass to replace the hot water coming out of the Thermalito Afterbay. This would open up over 15 miles of new cold water spawning area downstream of the Thermalito outlet. Various bypass designs have been considered and scoped. Without any additional delay, GGSA calls on the CA Dept. of Water Resources to implement one of them and restore the river for salmon spawning.