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ISAB Offers 'Different Perspective' on Flow Augmentation

by CBB Staff
Columbia Basin Bulletin - February 14, 2002

The Independent Science Advisory Board says "a different perspective emerged" from its latest review of one of the Columbia River basin's most frequently debated topics -- the effect of flows on salmon and steelhead survival.

In particular, the ISAB report issued Tuesday analyzed the relationship of fish survival and river flows that are augmented from storage reservoirs created for other uses, such as recreation, irrigated agriculture, flood control and to feed hydroelectric projects. The report was prepared in response to questions posed by the Northwest Power and Conservation Council and others.

The scientists will present their findings to the Council at next week's Council meeting. The full report can be found at .

The ISAB's report has obvious relevance for the draft amendments to the mainstem portion of the Council's Fish and Wildlife Program that are now before the Council for consideration. The comment period on the draft amendments has closed, but the Council is re-opening the comment period on the draft mainstem amendments for the very limited purpose of allowing people to respond to this report.

"We realize that the prevailing rationale for flow augmentation is inadequate. It is neither complete nor comprehensive," the ISAB wrote in the report that has been offered for public comment. "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 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."

The Council on Nov. 14 of last year asked the ISAB to update and clarify its review of flow augmentation. The Council and the Columbia River Inter-Tribal Fish Commission submitted specific questions on the subject for the ISAB to answer.

The report will inform the Council as it crafts final amendments to the mainstem portion of its Fish and Wildlife Program. The Council has said it expects to adopt final on the draft were accepted through Feb. 7.

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 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."

In addition, the ISAB expressed concern about the impacts of "pulsing" at the Lower Snake dams, where water releases follow electricity demand -- "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.

"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.

"These altered hydraulic patterns likely affect fish orientation and migration, with increased exposure to predators and increased energy consumption at lower flows.

"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 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.

Stimulated by the specific questions posed by Council and others, the ISAB has taken a fresh look at the whole matter of river flow and fish survival with special emphasis on the Lower Snake River reaches, according to the summary.

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 public is invited to submit comments to the Council about the report and the implications of for the Council's deliberations on the mainstem amendments. Comments will be accepted until 5 p.m., 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

Comments about the draft mainstem amendments that are not directly related to the ISAB's report will not be accepted.

CBB Staff
ISAB Offers 'Different Perspective' on Flow Augmentation
Columbia Basin Bulletin, February 14, 2003

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