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Robust Spill Evaluation at Dams Faces Tough Hurdles

by Bill Rudolph
NW Fishletter, October 20, 2003

Evaluating the benefits to fish of the $100 million annual summer spill strategy at Columbia River dams is a top priority on the NOAA Fisheries policy radar, Power Council members heard last week, but there could be one big hangup--not enough salmon in the river at that time of the year for researchers to develop a robust survival study.

That was the take-home message from federal agency folks who spoke at last week's meeting of the Northwest Power and Conservation Council in Missoula, Montana. The Council's latest fish and wildlife plan calls for such an evaluation of spill and flow augmentation. Four study alternatives are under review, ranging from looking at status quo operations to other scenarios of more or less spill and investigating more specific survival rates of summer migrants at the dams.

NOAA Fisheries spokesman John Palensky said conducting this type of research "is not easy" with such small numbers of fish to study. He said researchers have gathered very little information on Snake River fall chinook, a stock listed for protected under the ESA and principal benefactors of summer spill operations.

Palensky said the agency was "somewhat skeptical" that it would be able to develop a research plan that will give them the statistical power for a valid study He said high water temperatures make it risky to tag fish in August, and the questionable availability of chinook for the study "can be problematic depending on what the scientists tell us are the numbers of fish that are necessary to get the power of the test that we want..."

Other logistical logjams Palensky named were the short time-frame left to order radio-tags and develop ways to sample more fish in the Columbia estuary, while making sure the spill research doesn't conflict with other ongoing studies.

About $30 million in research is being conducted throughout the hydro system every year, said Witt Anderson, chief of the Corps of Engineers' fish management office. He briefed the council on ongoing spill research at federal dams, where some spill regimes have been altered after intense survival studies.

Anderson pointed to places like Ice Harbor Dam on the lower Snake, where juvenile fish survival was found to be only about 88 percent for juvenile fish, instead of the 98 percent previously estimated. Spill survival at John Day Dam was also found to be less than expected, so spill levels have been adjusted to maintain biological benefits to fish while reducing spill costs.

Anderson said John Day spill may be re-adjusted once again to 30 percent both day and night from the 0 percent daytime/60 percent nighttime spill strategy now in effect during the juvenile migration.

The Corps' spokesman also said that some spill tests have shown evidence of adverse effects on both adults and juveniles. Adult fish may have more trouble finding fish ladders when spillways are operation, and tailrace currents created by certain spill patterns can create eddy currents where river predators like pikeminnow find it easier to pick off juvenile salmon migrants.

Improved juvenile fish survival from new dam modifications like the $45 million "corner collector" at Bonneville Dam will have to be quantified to create a new baseline for future survival studies, Anderson said. About 90 percent of juvenile fish in the forebay of the dam's Second Powerhouse are expected to use either the new corner collector or the bypass outfall already in place, with an estimated survival rate greater than 95 percent. Spillway survival is estimated in the 98-percent range.

BPA VP Greg Delwiche explained different options for "offsets" his agency is studying to make up for any less survival of both listed and non-listed salmonids from a reduced spill regime. These offsets would be created by expanding strategies besides spill that are designed to improve fish survival, like increasing predator control projects in the reservoirs.

Council members will hear more on spill evaluation at their meeting next month after a technical review is completed by fish agencies.

But Rod Sando, director of the Columbia River Fish and Wildlife Authority inserted a note of caution towards the end of the discussion. He said regional fish managers recognize the difficulties of quantifying the benefit of spill, but potential adverse effects on non-listed salmon stocks and the last migrating segment of ESA-listed salmon should be acknowledged, because the last five percent of the run is "the most innovative" part of that population. Nevertheless, he said he understood the economic reasons for the analyses.

He called on policymakers to borrow a concept from conservation biologists-"the precautionary principle," which generally permits a lower level of proof of harm to be used in policy-making whenever the consequences of waiting for higher levels of proof may be very costly and irreversible.

Montana council member Ed Bartlett had a different view. With his state pushing hard all year for flow and spill evaluations to be included in the council's program, and later calling for an early end to spill last August, Bartlett said he was aware of the difficulties of measuring the impact of the spill program. "We knew that temperature makes it difficult to tag fish, and there may be few fish to tag. But if there are so few fish in the river, why are we spilling?"

Federal agency heads faced mounting pressure last August to end the summer spill program early (which was costing $1 million a day) because most listed fish had passed through the hydro system by the middle of the month, the vast majority being barged from Snake River dams, anyway. The agencies went on record noting the excessive cost of the strategy relative to the biological benefits. They cited a council analysis that showed August spill at four mainstem dams increased the survival of ESA-listed Snake River fall chinook by only five fish and boosted non-listed upriver bright numbers from the Hanford Reach by about 2,400 fish.

By the middle of October, so many fish had returned to the Hanford Reach area to spawn that the number of extra fish that would have been saved by the August spill effort amounted to less than two-tenths of a percent of the returning run.

Bill Rudolph
Robust Spill Evaluation at Dams Faces Tough Hurdles
NW Fishletter, October 20, 2003

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