The sluiceway at Bonneville Dam’s Powerhouse 1 (nearest the Oregon shore) passed with flying colors tests evaluating whether it would be a suitable passage route for spawned out steelhead, or kelt.
The kelt are headed downstream toward saltwater and thus have the potential to turn around and return later in the year to spawn again.
“It came out great. Both sluiceways looked extremely good for adult passage,” said researcher Dennis Schwartz of the U.S. Army Corps of Engineers, which operates the dam.
The tests completed last week involved sending balloon tagged surplus kelt from central Oregon’s Round Butte Hatchery down both the PH1 sluiceway, which is designed to pass debris, and the Powerhouse 2 “corner collector,” which is a sluiceway that has been retrofitted to provide a safe surface oriented passage route, primarily for outmigrating juvenile salmon and steelhead. The intent was to find out what immediate mortalities and/or injury might occur.
“We want to measure direct effects on large fish so we can make a decision as to what surface route we open and make available to kelts moving in early spring,” Schwartz said.
As it turned out 1 of 100 fish sent down through the corner collector died, and three of the tags quit emitting signals for unknown reasons, one after being sent down the corner collector and two down the PH1 sluiceway. Schwartz said researchers suspect that sea lions, which congregate below the dam in late winter and spring to prey on spawning salmon and steelhead, might have made off with the three ballooned tagged fish that came up missing.
With predation the survival rate was 98 percent for both passage routes; excluding predation PH1 sluiceway survival was 100 percent and corner collectors was 99 percent.
Only one recaptured fish from each of the passage routes sustained an injury attributed to passage; thus the malady free rate was 99 percent for both sites. The maladies involved “a little bit of bruising,” Schwartz said.
The corner collector had been evaluated in 2007 and 2008 to see if its attractive flows would bring in kelt, and they did.
“Kelt normally look for a surface passage route,” Schwartz said. Steelhead juveniles too have more of a surface orientation as compared to deeper swimming chinook.
The corner collector was used last year early in the season (before spill was started to help pass juvenile fish April 10) but had to be closed at times because the 5,000 cubic feet of water it spills into the dam’s tailwater stirred up just enough additional total dissolved gas to push the dam’s output over state prescribed limits. It was feared that heightened gas levels could cause harm to just emerging juvenile chum salmon below Bonneville in the Ives Island area.
“We opened it and closed it several times,” Schwartz said. This year the Corps decided to evaluate the sluiceway to see if it would serve just as well as the corner collector in passing in passing kelt.
This sluiceway is opened by March 1 and is operated with a flow of 1.8 kcfs as opposed to the 5 kcfs used by the corner collector, which is typically not opened until spill starts. That means less TDG would be stirred up by plunging water down through the sluiceway than would be created by opening the corner collector early. And less water is lost that could have been sent through turbines to generate power.
Schwartz said that the Bonneville Power Administration, which markets power generated at the dam, and federal, state and tribal salmon managers have said they support a switch of the kelt passage emphasis from PH2 to PH1 as long as the PH1 sluiceway performs as well as the corner collector.
The Corps plans to switch powerhouse priority over to PH1 early in the season, meaning its turbines start first to draw water and fish in that direction.
At river flows of more than 180 kcfs, as they often are in springtime, Corps operators will have to also turn on PH2’s turbines, as well as open the corner collector, to pass flow.
“So this is more of a water saving measure with equal fish passage in those years where early spring flows are less than 180 kcfs or in excess of PH1 capacity,” Schwartz said.
A number of entities were involved in the tests led by the Corps. They include contractor Normandeau Associates, Inc. U.S. Department of Agriculture and Columbia River Inter-Tribal Fish Commission personnel engaged in sea lion hazing at the dam. The Oregon Department of Fish and Wildlife, which operates Round Butte, supplied the fish and Portland General Electric, which owns the hatchery, donated the use of an adult fish transport truck, fuel and a driver for two round trips from Round Butte near Madras to the dam.
This was the first year of direct releases of tagged adult steelhead through the PH2 corner collector. For the earlier study the Corps installed a special camera early in the season to try to quantify kelt sized targets in camera images that were using the corner collector early in March when facility was opened.
The sluiceway at The Dalles Dam, the next project upriver, will this year and in the future open earlier and close later in the year to provide a wider kelt passage window. A two-year hydro-acoustic evaluation indicated the presence of overwintering steelhead and kelt both March and beyond the end of November.
“We found out there was quite a bit of activity during both of those periods,” Corps researcher Sean Tackley said. The Corps will now open the facilities March 1 instead of April 1 and keep it open until Dec. 15, instead of the end of November closures of the past.
Researchers are looking for “simple solutions” at the dam that can provide downstream passage for what are relatively frail fish, Tackley said. The kelt are returning to the ocean immediately after completing their spawning mission.
A 2008 Endangered Species Act “biological opinion” on the operation of Columbia-Snake river mainstem dams bid federal agencies to "evaluate operation of the Bonneville PH2 corner collector from March 1 through start of spill as a potential means to provide a safer downstream passage route for steelhead kelts, and implement if warranted."
It says that "NOAA Fisheries considers improvement in kelt survival a key element to improving the survival of all steelhead ESUs." Because of their relatively poor post-spawning condition, kelt survival is generally considered to be quite low irregardless of what they encounter.
Middle and Upper Columbia and Snake River steelhead stocks are all listed under the Endangered Species Act. NOAA Fisheries is charged with assuring that federal actions, such as the dams’ operations, don’t jeopardize protected fish.