Flows from Mid-Columbia River basin hydroelectric projects are now being managed 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 fall.
The so-called 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 hatch and begin migrating to the ocean.
The total number of gravel nests, called redds, counted at Vernita Bar this year 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 were 8,915, well in excess of the 10-year average of 6,972, said BPA.
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 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. “This is a case where the salmon are actually better off with the hydro system there.”
To count the redds, Grant County PUD, 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 redds. Even though some redds were exposed, they were not harmed because they can be out of water and remain viable 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 about 35 miles east of Yakima, Wash. 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. Normal operations discharge more water during the day and less at night to meet the demand for power.
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 kcfsto allow the daily average flow of 100kcfsto 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 update added in 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 county PUDs, and by BPA, WDFW, National Marine Fisheries Service, Oregon Department of Fish and Wildlife and the Yakama, Umatilla and Colville tribes.