Operators of Columbia River hydroelectric dams are now managing flows to protect thousands of nests left by more than 60,000 fall Chinook salmon that returned to spawn in the Vernita Bar area of the Columbia's Hanford Reach this past fall.
Vernita Bar flows reverse the water pattern typically dictated by hydroelectric generation to protect the eggs of one of the region's healthiest wild salmon populations until the young salmon hatch and begin migrating to the ocean.
The total number of gravel nests, called redds, counted at Vernita Bar in 2011 should bode well for the fall Chinook returns in the next three to five years, according to Scott Bettin, Bonneville Power Administration fish biologist. Redd counts for this season amounted to 8,915, well in excess of the 10-year average of 6,972.
Fish biologists from the Washington Department of Fish and Wildlife, Grant County Public Utility District, the U.S. Army Corps of Engineers and BPA went to Vernita Bar on Nov. 20 of 2011, to survey redds and determine river flows necessary to protect the salmon during the winter and spring.
A redd is a gravel nest created by female salmon or trout where its eggs are laid, subsequently hatched and from which fry emerge.
"With our ability to use the hydro system to protect the salmon during the winter and spring, we have practically doubled the amount of spawning habitat and ensured that it will stay wet compared to what it would be without the hydro system," Bettin said.
He said, "This is a case where the salmon are actually better off with the hydro system there."
To count the redds, Grant County Public Utility District, which owns and operates Priest Rapids Dam, located four miles upstream from Vernita Bar, reduced flows about 50 percent to 50,000 cubic feet per second. At that level, the biologists were able to get an accurate count of the redd nests. Even though some redds were exposed, they were not harmed because they can be out of water and remain viable for up to 12 hours at this stage of development.
As a result of the count and location of the redds, this year's flows are set at a minimum of 65,000 cubic feet per second to protect them.
Vernita Bar is a large gravel bar in the Columbia River nearly 35 miles east of Yakima. There, and in several other places in the 50-mile long Hanford Reach, salmon dig redds in the gravel to lay their eggs. When fish biologists found the first redds in early October, the Vernita Bar flows were activated, adjusting water flow from Grand Coulee, Chief Joseph and five public utility district dams upstream of the reach to protect the redds.
The Vernita Bar agreement, signed in 1988 and updated in 2004, calls for the hydropower system to discharge more water during the night and less during the day. Other operations discharge more water during the day and less at night to meet the demand for power. This agreement reversed the process and puts the needs of fish ahead of optimizing the hydro system for power to help ensure higher survival of the Hanford Reach Chinook salmon.
From mid-October to the weekend before Thanksgiving, river levels below Priest Rapids Dam were reduced during the day to 65,000 cubic feet per second.
Lower water encourages salmon, which mainly spawn during the day, to dig their redds lower on the river bar. Knowing this, flows were increased at night to as much as 172,000 cubic feet per second to allow the daily average flow of 100,000 cubic feet per second to pass downstream. The objective is to ensure that eggs are deposited in areas that will remain submerged until they hatch.
The salmon will hatch in the spring and stay in the reach for about six weeks. The 2004 Vernita Bar agreement added in a requirement to limit how quickly flows could change to reduce the likelihood that fish would be stranded on the riverbanks.
The agreement was signed by Grant, Chelan and Douglas public utility districts, and by the Bonneville Power Administration, National Marine Fisheries Service, Washington Department of Fisheries, Oregon Department of Fish and Wildlife and the Yakama, Umatilla and Colville tribes.
"The incredibly high level of cooperation among the agreement's many partners is the reason this very unique and complex operation works for both fish and the region's ratepayers," Bettin said.