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Commentaries and editorials

Council Hears New Report
on Flow Augmentation Benefits

by Barry Espenson
Columbia Basin Bulletin - February 21, 2003

A report released last week says that Columbia/Snake river managers would be wise to test river management techniques other than flow augmentation as a means to improve in-river survival of, particularly, Snake River fall chinook salmon.

"The (flow/survival) issue requires re-evaluation," according to the 11-member Independent Scientific Advisory Board. The ISAB advises both the Northwest Power Planning Council and the federal NOAA Fisheries, which enforces the Endangered Species Act for salmon and steelhead in the Snake and Columbia rivers.

"The prevailing flow-augmentation paradigm, which asserts that in-river smolt survival will be proportionally enhanced by any amount of added water, is no longer supportable. It does not agree with the information now available," according to the report.

Based largely on data collected in studies of Snake River fish, the scientists' report says rapid fluctuations in flow, which are related to increases and decreases in electricity generation at the dams, may have the greatest impact on fish survival, particularly during periods of low flows.

"This is important information for the region to consider," Council Chair Judi Danielson said. "The ISAB report should point research toward investigating the value of stable flows as a challenge to the conventional wisdom that all the fish need is higher volumes of water and faster flow, as has been the practice with flow augmentation."

If the panel's hypotheses prove true, the scientists say the survival benefits could quite possibly be gained a lesser cost.

The water, for example, drawn from Idaho reservoirs to augment river flows has great value in that state for agricultural production, recreation and other uses, ISAB member Charles Coutant said.

"It may be a whole lot better to stabilize the flows, using the flows you already have," rather than adding water from the reservoirs, Coutant said. Smoothing out those fluctuations, which are exaggerated when flows are at their lowest, could involve leaning more heavily on other dams to answer power load.

The scientists say that recent studies "suggest a survival benefit from increasing flow when flow is low, but no indications of added benefit at higher flows, within the range of flows that have occurred in the past few years." The breaking point on the Snake River appears to be at about 100,000 cubic feet per second for steelhead and yearling (spring/summer chinook) and 50 kcfs for fall chinook.

Below those levels, survival drops. Flow augmentation is intended to boost river flows to levels that keep the young fish moving downriver.

The problem with flow augmentation is that, for the fall chinook at least, the necessary volume may not be available to make a difference.

"The chances of having that water available is pretty slim" Coutant said, in late summer and early fall. It would be of benefit if the flows were near the 100 kcfs threshold and just needed a small -- relatively -- boost.

He said that it would be "more manageable" to stabilize flows and manipulate river hydrology to provide the fish better migration cues at low flows.

Research should be directed at evaluating the impact of smoothing flows that now are manipulated even hourly to respond to electrical demand, which is "low at night and highest at the beginning and end of the workday."

"These fluctuating discharges produce pulses of flow in downstream reservoirs and dam forebays that are not described by the average annual, weekly, or daily flows that to-date have been used in fish-survival studies. .The frequency and duration of fluctuations are greater at low flows than at higher flows," according to the report.

"During flows typical when underyearling chinook migrate the difference between daily maximum and minimum flow rates can exceed 150 percent. At the lowest flows, typified by those in January 2003, we determined that pulses of high and low discharges induce an oscillation in the reservoirs, similar to water sloshing in a bath tub, that can induce reverse flow," the report says.

"These altered hydraulic patterns likely affect fish orientation and migration, with increased exposure to predators and increased energy consumption at lower flows," the report says. And the river's own contours add to the mix.

"There are probably some awful complex hydrology going on in these reservoirs" that, when agitated by the rapid flow fluctuations, further confuse the young fish.

"We believe stabilization of flows could be more effective in improving survival of juvenile salmonids than simply adding a volume of flow, as in flow augmentation, where water can be released intermittently. Instituting stable flows might be undertaken as an experiment. The effects on survival of juvenile salmonids should be measurable immediately."

The report was prepared in response to questions posed by the Council and the Columbia River Inter-Tribal Fish Commission, which helps appoint members to the panel.

The ISAB said the prevailing rationale for flow augmentation is inadequate and "neither complete nor comprehensive."

According to the report, "there is room for alternative explanations of available data that have both scientific justification and practical value for managing the hydrosystem for multiple uses including salmon recovery."

"We identified several alternative explanations (hypotheses) for the correspondence of observed flow-survival data and radio-telemetry data, which are not necessarily mutually exclusive. These alternatives do, indeed, lead logically to management opportunities that extend beyond flow augmentation as presently defined. This report outlines several of them. We assembled enough information about them to suggest that they need serious further study and evaluation.

"The ISAB believes that, with improved knowledge and subsequent management actions, it may be possible to achieve improved survival of juvenile salmonids through the lower Snake River reaches and their dams, even at lower flows. With an expanded perspective, this might occur at lower costs for operation of the hydrosystem and more effective use of stored water for other purposes than is possible with the prevailing flow-augmentation paradigm," the report says.

The Council on Nov. 14 of last year asked the ISAB to update and clarify its review of flow augmentation.

The ISAB report's executive summary says that "the issue is important in a broader context, because flow commitments are part of the legal agreements under ESA for some listed stocks. The relationship between river flows and salmon production has been reviewed before by the ISAB, but many questions remain."

The ISAB in a Dec. 19 memo suggested that that it could make a short response to the questions within that timeframe requested by the Council (the end of January) and follow with more detailed information at a later date.

The ISAB report notes that there have been improvements in study designs over the years, particularly in the PIT-tag and radiotelemetry studies.

Also, the quantity and quality of accumulated data have improved, and the range of factors potentially related to survival of anadromous fish has been extended. This has allowed more patterns to be resolved in analyses, according to the summary.

To focus only on the specifics of the questions posed to the ISAB would be to miss the point: the whole issue of flow and fish survival requires reevaluation. Management alternatives for improving survival of migrating juvenile anadromous fish include many dimensions beyond the current procedures for "flow augmentation," the summary says.

The ISAB answered the specific questions in the text of its report, but considers them to be a subset of the broader issue.

The ISAB was established by the Council and the National Marine Fisheries Service to provide independent scientific advice and recommendations on issues related to regional fish and wildlife recovery programs under the Northwest Power Act and the Endangered Species Act. The ISAB is designed to foster a scientific approach to fish and wildlife recovery and ensure the use of sound scientific methods in the planning and implementation of research and recovery strategies related to these programs.

The flow/survival issue is timely because the Council is now considering amendments to its Columbia River Basin Fish and Wildlife Program regarding dam operations and flows in the mainstem Columbia and Snake rivers. For that reason, the Council is inviting public comments on the ISAB report through Tuesday, Feb. 25.

Comments should be directed to:
Mark Walker
Director, Public Affairs Division
Northwest Power Council
851 SW Sixth Avenue, Suite 1100
Portland, OR 97204
fax 503-820-2370 or email

The Council has said it expects to adopt final amends in March. Written comments on the draft were accepted through Feb. 7. Comments about the draft mainstem amendments that are not directly related to the ISAB's report will not be accepted.

The full report can be found at Council Hears New Report on Flow Augmentation Benefits
Columbia Basin Bulletin, February 21, 2003

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