Ecological impacts of the flow provisions of the Biological Opinion for endangered Snake River salmon on resident fishes in the Hungry Horse and Libby systems in Montana, Idaho, and British Columbia

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Within the community of biologists in the basin, contention exists with respect to the scientific rationale for late summer flow augmentation in the mainstem Columbia River intended to assist outmigration of endangered Snake River fall chinook, as called for in the Biological Opinion (BiOp). Contention primarily exists with respect to three concerns:1. Flow augmentation in August and September is provided by deep drafting of Hungry Horse and Libby reservoirs in the headwater reaches of the Columbia River in Montana, leading to negative effects borne by residents there (Figures 1, 2 and 3). Such drafting can also impact refill schedules, leading to negative effects with basin- wide implications. 2. Summer drafting, following on the heels of deeper flood control drafting in early spring, might cause significant negative impacts on the ecology of both reservoirs, as well as lakes and river segments downstream to the target reaches in the mainstem , and; 3. Flow augmentation in the mainstem during summer and fall (normally low flow periods) may or may not significantly benefit endangered fall chinook.Litigation has been threatened or pursued owing to a lack of resolution of these concerns by policy makers. People in the headwater areas believe that the impacts of drawdowns on resident fisheries are substantial and not warranted on the basis of a presumed weak or non-existent flow-survival relationship for endangered fall chinook using the mainstem. On the other side, the Biological Opinion (BiOp) concluded the flows were needed because slow water movement in the lower Columbia River, and high water temperatures at that time of year negatively impact the endangered fish. Additionally, downstream constituents want the BiOp implemented as called for under the authority of the Endangered Species Act.

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