As part of the ongoing studies for the Yakima Basin storage project, the U.S. Bureau of Reclamation retained ICF to provide ecosystem diagnosis and treatment (EDT) model support that linked physical models developed by Reclamation and others to EDT parameters.
The studies included analysis of fisheries benefits, including new flow parameters characteristic of highly regulated systems and habitat parameters for side channels and floodplains. The EDT analysis was conducted on 69 reaches on the Naches River and Yakima River below five existing Reclamation dams in the Yakima River watershed.
ICF provided modeling support using data and information from physical models and EDT to provide a clearer understanding of the production of salmon and steelhead in medium-to-large river systems, and especially in highly regulated systems. These physical models predicted changes to the aquatic environment expected under hydrographs associated with seven potential storage and river management alternatives. Reclamation also conducted two-dimensional river modeling on unconfined reaches of the Yakima River, and the flow habitat relationships that were produced were used to populate the EDT model with values for habitat quantity and quality.
The project also sets a precedent and provides guidance for linking EDT to physical models and, particularly, to two-dimensional river modeling. EDT estimates fish production under specific environmental scenarios, but does not include the physical models. In this project, state-of-the-art physical models were combined with EDT to increase the accuracy and precision of fish production estimates ascribed to regulated hydrographs.
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