With inflows expected to be higher than normal this year, the Idaho Power Company has begun a steep draft of the Hells Canyon Complex’s Brownlee Reservoir to set the stage for operations this fall and winter to protect what has become a growing annual community of salmon “redds.”
After Labor Day weekend, Idaho Power began drawing down the reservoir in preparation for its Fall Chinook Program which provides flat flows for salmon spawning in the Snake River below Hells Canyon Dam. Outflows in recent days have risen to more than 20,000 cubic feet per second after simmering in the teens for most of August.
Brownlee Reservoir – the primary “storage” project among Complex’s three dams on the Idaho-Oregon border -- elevation will continue to drop through the month of September. As of Monday the reservoir level was 2,047 feet, leaving the boat ramps at Hewitt and Woodhead parks the only usable ramps on Brownlee. The water level will drop below Hewitt’s boat ramp by this weekend.
The company anticipates all boat ramps will be out of the water during October. The water level is expected to fall to approximately 2,015 feet by the end of the month. To maintain flat flows during fall chinook spawning, Oct. 10 through Dec. 5, space must be made in Brownlee Reservoir prior. As the spawning period begins, the reservoir will begin to refill.
For updated Snake River flow and Brownlee elevation and boat ramp information, please visit http://www.idahopower.com/OurEnvironment/WaterInformation/default.cfm
The company anticipates the minimum flow set during the spawning period can be maintained until fry emergence (when the young fish leave the redds, or nests) in the spring without emptying Brownlee Reservoir.
The number of fall chinook salmon redds counted each year from Hells Canyon Dam, which blocks fish passage, down to Asotin, Wash., has been rapidly rising, particularly over the past decade. The count was 346 in 2000. The Snake River redd count last year totaled 2,944, which was the most since counts began in 1988.
The 2010 fall chinook return, as measured at Lower Granite Dam, streaming into the Snake and tributaries such as the Clearwater was 41,815, which more than doubled the previous high count of 16,624 in 2008. Lower Granite is located on the lower Snake River in eastern Washington downstream of Hells Canyon.
Many of the spawners are of natural origin. Some are fish acclimated by the Nez Perce Tribe at Pittsburg Landing, Captain Johns Landing and Big Canyon before their release. Still others are fin-clipped hatchery fish released below Hells Canyon Dam by Idaho Power.
This year’s return looks strong. A total of 8,510 adult fall chinook had been counted at Lower Granite through Wednesday. The run appears to be at its peak with a high count of 1,063 on Monday, followed by 656 Tuesday and 830 Wednesday.