Chinook salmon lay their eggs below Hells Canyon Dam in the fall. The eggs need the right flow of water to develop, so we control the water released from Brownlee Reservoir from October through December, until the eggs hatch. We keep the flow between 8,500 cubic feet per second (cfs) and 13,000 cfs.
To do this, we sometimes lower the water in Brownlee Reservoir. Because of lower water levels, we may not be able to use as much hydropower and may buy power from other sources.
To check on the health of fall Chinook salmon, the U.S. Department of Fish and Wildlife Service and Idaho Power survey their nests (also called redds) in the spring. View a chart of our total annual fall Chinook redd counts.