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Council Hears More Tutorials on Flow and Survival

by Bill Rudolph
NW Fishletter, December 17, 2002

Members of the Northwest Power Planning Council spent most of an entire day last week listening to the pros and cons of flow augmentation as they geared up to tackle their mainstem amendments. The council was scheduled to take a final vote on the proposal in February, but Gene Derfler, one of Oregon's new council members, asked for an extra month to help the Oregon contingent get up to speed on the topic. His wish was granted.

Karl Dreher, director of the Idaho Department of Water Resources, gave the council an update on his department's earlier report on flow augmentation on the Snake River. Dreher said the latest research into fish survival and flow augmentation hasn't changed his view that adding flows to help fall chinook doesn't improve their survival. The Idaho hydrologist said that in spite of the development of irrigated agriculture in Idaho, average daily flows in the Snake River haven't changed and are still highly variable from year to year.

Dreher said analysis of the newest NMFS PIT tag data doesn't make a case for extra flows in the summer. "This data is so inconclusive that it shouldn't be used to justify flow augmentation," he told the council.

He used the 1999 fish migration as an example, noting the data showed that later-migrating fish traveled faster than earlier migrants even though flows were lower.

Also, by calculating fish survival using a broader flow index than that used in the NMFS analysis, Dreher said fall chinook survival was actually less in 1997 than 1998, which was a lower water year. He also noted that in good water years, "fish are better, but adding water in bad water years doesn't help fish, especially if that additional volume is coming from the upper Snake, which is too hot."

Oregon council member Eric Bloch, disagreed with Dreher's analysis. Bloch cited the conclusions drawn by panel of independent scientists [ISAB], which reviewed the earlier Idaho report. The panel said the report went beyond the data when it concluded that NMFS studies cannot be used to justify flow augmentation. "... by the same criteria," the panel said, " the data are also inadequate to deny beneficial effects of flow augmentation." The ISAB said it endorsed the augmentation policy largely because of results from a study of wild fish that admittedly suffered from a small sample size, along with the results of the NMFS studies, which used hatchery releases, and correlated fish survival with four factors--flow, temperature, turbidity and release date. The feds have been unable to tease out any more answers from that, however.

Dreher told Bloch the panel admitted to misreading part of his report after he responded to their review.

NMFS scientists were on hand to report on this year's Snake River survival studies, which they had earlier described at the Corps of Engineers research review in November. Biologist Bill Muir reported that about 67 percent of all Snake River hatchery-raised spring chinook made it to Lower Granite last spring, with inriver migrants averaging about 50 percent survival (from the Snake River trap to Bonneville Dam) and steelhead about 27 percent.

Muir said the spring chinook survival was above the standard set in the current BiOp, but he called steelhead survival "alarming" because it was down compared to recent years with good flows. The largest drop was between Lower Monumental Dam on the Snake River and McNary on the mainstem Columbia. He suggested the drop may be due to bird predation, mainly Caspian terns, near the confluence of the two rivers. At Crescent Island, more than 12,000 PIT tags had been retrieved this year, a number that represents nearly 10 percent of the steelhead population that had been counted at Lower Monumental Dam on the Snake River.

Muir said juvenile fall chinook survival between McNary and John Day dams was about the same this season as in other recent years--nearly 75 percent, with survival again correlating with flow, temperature, turbidity and release date. Manipulative experiments would have to be performed to sort out the variables, Muir also said.

The benefits of flow still seemed somewhat elusive for the later migrating fish.. "Until they're ready [fall juveniles]," Muir told the council, "you can add all the flow in the world and you can do more harm than good."

Fellow NMFS scientist John Williams, from the agency's science center in Seattle, presented the council with an extensive display of graphs to explain what his agency suspects--that the increase in the amount of time it takes migrating fish to pass the dams may have a significant effect on fish survival because it changes the time when the fish reach the estuary and the ocean. In some cases, travel time past the dams has doubled. In the hydro system itself, Williams said that "above some threshold average, [spring chinook and steelhead] survival appears to vary little, is relatively high and does not correlate with flow."

Below that threshold, as indicated by data from the extremely low flow year of 2001, fish survival is a good deal lower, Williams said. But even at the lower levels, the relationship between flow and survival "is not strong."

Williams said biologists have seen higher smolt-to-adult returns in recent years, but they are still below levels estimated for the 1960s. NMFS is conducting research to relate juvenile migration history and flow within the hydro system to adult returns. Scientists are looking at other factors for adult returns besides timing of ocean entry, he said, by investigating characteristics of the estuary and near-ocean plume environment.

But Williams said the agency feels that lack of a strong flow/survival relationship in reaches such as the stretch between Lower Granite and McNary dams does not support an end to flow augmentation. That had some onlookers puzzled. "I'm not sure we're asking the right questions regarding flow augmentation," said Rob Walton, assistant director of the Public Power Council. "The key uncertainty here is not whether in-river survival rates are low in very low water conditions. The key question for decision-makers in such a situation is what measures produce the best bang, in terms of increased survival, for the buck."

After the NMFS presentation, Walton was left with several questions. "How much do we know about the change in survival produced by a release of water from a reservoir in these conditions? Is there a measurable increase in survival attributable to the release of water, and if so, how far does the benefit continue downstream? If there is a measurable benefit, is it greater, for the money, than alternative measures?"

NMFS scientist Williams told the council most of the fish losses can be attributed to dam passage, "leaving little mortality in the reservoirs, where flow would affect survival the most." He said adult returns varied widely depending on juvenile migration timing, but the agency cannot presently predict when favorable estuary and ocean conditions will exist.

The council also heard modeling results of the council's preferred alternative for mainstem operations from Columbia Basin Research, the UW-based group that developed the CRiSP passage model. CBR's Chris Van Holmes told the council that the CRiSP modeling tracked closely with council staffer Bruce Suzumoto's analysis using NMFS' SIMPAS model. Averaging over all stocks, survival through the hydro system was estimated to be only 0.032 percent less than under the current BiOp regime, with only about 0.14 percent fewer fish barged under the council's proposed program than under BiOp operations. Survivals for strictly in-river migrating fish was virtually identical for the council and BiOp operations, said Van Holmes.

A minor flap developed over the model inputs, which caused Oregon council member Eric Bloch to question the CRiSP results. But Suzumoto said the problem was just a staff mistake over which spill input was used to model low flow years. The difference was not expected to change the results much at all, he said. Another analysis would be completed and its results presented at next month's council meeting.

Council staffer John Fazio reported on power impacts from the proposed alternative. He estimated that it would amount to an $8 million reduction in regional power costs. The proposal calls for reducing flow augmentation in the spring, but adding more in summer. It would remove the April 10 refill requirement for federal reservoirs, extend drafts for fish flows through September and provide level outflows at Montana reservoirs to improve conditions for resident fish.

After hearing that the difference in power costs amounted to only $8 million, one fish and wildlife veteran wondered out loud why the council was wasting so much of everybody's time.

Later, council chair Larry Cassidy responded. "I don't think $8 million is insignificant, especially when it's seen as a year-to-year gain." The bottom line, Cassidy said, is "can we improve things without adverse impacts to fish?" Cassidy said the council should not support operations that would help resident fish populations at the expense of anadromous stocks.

The council chair said new data is in the works that will help his group work with fish and wildlife managers to reach agreement on future hydro operations. "We think we're at a different level now," Cassidy said, noting that those who argue for maintaining the status quo "because that's how we've always done it" are holding a position that is no longer defensible.

Bill Rudolph
Council Hears More Tutorials on Flow and Survival
NW Fishletter, December 17, 2002

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