A PANEL OF INDEPENDENT scientists has issued a report challenging the conventional view that increased flow volumes in the lower Columbia and Snake river systems help juvenile salmon survival. The report, discussed at a meeting of the Northwest Power Planning Council in Portland, Oregon, US, specifically questioned the benefits of ongoing ‘flow augmentation’ operations that involve Libby and Hungry Horse dams in Montana.

In the past, the two dams in northern Montana have released surges of water in August, to benefit salmon passage. The Independent Scientific Advisory Board, an 11-member panel of scientists, concluded that the prevailing rationale for flow augmentation is inadequate, and ‘neither complete nor comprehensive’. The report also finds that stabilising flows in the lower Columbia may be more effective in improving juvenile salmon survival than simply boosting water volumes through flow augmentation.

The State of Montana Fish, Wildlife and Parks has long questioned the benefits of flow augmentation compared to the ecological damage the August releases cause above and below the dams. When releases are ramped up, the reservoirs are left with biologically fertile shorelines high and dry during the most productive time of year. Riverbanks downstream, meanwhile, are swamped by higher flows, adversely impacting habitat for threatened bull trout and other resident fish. River and reservoir recreation have also been affected.

The Northwest Power Planning Council is currently considering amendments to its Fish and Wildlife Programme concerning dam operations in the Columbia and Snake rivers.