BEND-With the Columbia River system's water supply forecasts shrinking with nearly every passing day of the New Year, hydro and fishery managers this week agreed to back off, for at least the near future, the river flow levels intended to maintain higher elevation spawning areas for chum salmon.
The decision represents somewhat of a tradeoff between two fish stocks that are listed under the Endangered Species Act, threatened lower Columbia chum and endangered Upper Columbia spring chinook salmon.
A ratcheting down of flows between Feb. 20 and Feb. 26 through the lower Columbia's Bonneville Dam will drop the hydro project's tailwater elevation from about 13.5 feet, which has been maintained since late November, to 11.8 feet.
Related operational changes at, primarily, Grand Coulee Dam will allow the saving of more water behind the mid-Columbia facility that can be unleashed in springtime to pad spring chinook juveniles' migratory path toward the Pacific Ocean. That would also result in the dewatering of chum salmon eggs deposited below Bonneville in redds at elevations above 11.8 feet.
"Right now we're using storage out of Coulee to support operations" for chum salmon downstream, the Bureau of Reclamation's John Roache said during Wednesday's Technical Management Team meeting. The TMT is made up of representatives of federal hydro and fishery management agencies as well as federal, state and tribal "salmon" managers. The panel discusses day-to-day hydro operational strategies that might benefit fish stocks within the Columbia-Snake hydro system operated by the U.S. Army Corps of Engineers and the Bureau.
Roache said that the elevation of Lake Roosevelt, Grand Coulee's reservoir, had dropped by about 4 feet in elevation over the past week, and would continue to drop at from one-half feet to a foot per day under operations needed to provide enough water to maintain the 13.5-foot tailwater elevation downstream at Bonneville. That could compromise the ability to fill Roosevelt by April 10 to levels required under the federal government's strategy aimed at improving fish survival down through the hydro system.
Grand Coulee-Lake Roosevelt has the most storage capability of any facility in the system. Along with other projects upstream it is called on to "augment" river flows during fish migrations.
As its ESA listing status would indicate, the upper Columbia spring chinook stock is considered to be the more imperiled of the two species. The 1973 law says that an endangered species is one that is in danger of extinction; a threatened species is one likely to become an endangered species within the foreseeable future.
The listed upper Columbia spring chinook "evolutionarily significant unit" as endangered merits strong consideration, NOAA Fisheries' Paul Wagner told the TMT.
NOAA Fisheries among its duties is charged with protecting anadromous fish stocks listed under the ESA. That list includes 13 Columbia-Snake salmon and steelhead species.
The upper Columbia spring chinook "are not responding as well as other populations in the basin" to ongoing efforts improve their population status, Wagner said. It is the species that flow augmentation likely benefits the most, he said.
That said, Wagner proposed a new hydro operation that would allow more water storage and hopefully minimize harm to one of NOAA Fisheries' charges, the chum salmon. He suggested that beginning Wednesday Bonneville's tailwater elevation be dropped by a half foot every other day until it reached 11.8 feet, which would be next Tuesday. That would allow for a reduction in flows out of Grand Coulee.
He also asked that during that stepdown period the tailwater elevation would be pushed up to 13.5 feet for an hour or two within every 24-hour period. That temporary rewetting would be intended to "keep fish that may not have hatched yet alive" and also help newly hatched chum that might become stranded by the lowered water levels.
"An hour or two is not optimal but it would produce benefits," Wagner said.
The seven-day operation would allow the TMT to reconsider the operation, as well as updated weather forecasts, when it meets Feb. 27.
Current forecasts "are on the dry side," Wagner said.
Operations in recent years have sought to maintain through the winter incubation period tailwater elevations of from 11.3 to 11.7 feet, an average of 11.5. The idea is to allow access to as much of the spawning area in the Pierce-Ives island spawning area below the dam along the Washington shore as possible but at tailwater elevations the involved parties believe can be maintained through the winter to when young chum emerge from the eggs and nests.
The proposal to drop down to 11.8 feet allows a buffer of 0.3 feet to help dissipate total dissolved gas that could be generated by dam operations. High gas levels can cause fish physical harm.
The high elevation operation was forced by high precipitation levels in the fall that pushed up river flows across the Columbia-Snake river basin. The high water forced the Corps, which operates the dam, to flush more water through the project.
The strategy adopted last fall called for tailwater elevations to be managed between a 13.5 and 15.5 feet during the day, with a target of 14 feet. Water releases at night were to be limited to volumes that raise the below-dam water level to no more than 18.5 feet.
Those boosted tailwater elevation were implemented right in the middle of the chum spawning season, and allowed access to prime spawning areas at the higher elevation.
Because of the unusually high water levels, Washington Department of Fish and Wildlife biologists were "never really able to quantify" the number of redds in the Ives Island area this year. Wagner said as much as 50 percent of the spawning this year is at the higher elevation, because about half of the typical spawning period remained at the time of the elevation increase, and because the upper level habitat was likely the arriving fishes' preference.
Wagner said that in recent years as many as 300-400 spawners have settled in the area. He did say that the chum return in 2012 did not appear to be very high. Chum spawn at a variety of off-channel sites in the lower Columbia.
Republished with permission from the Columbia Basin Bulletin.
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