Yakima Basin Reservoir Food Webs
August 2014 - September 2015
- WA Department of Ecology
The U.S. Bureau of Reclamation (USBOR) and the Washington State Department of Ecology (WSDOE), through the Office of Columbia River, worked with the Yakima River Basin Water Enhancement Workgroup to develop an integrated water resource management plan designed to balance irrigation, recreation, and conservation needs in the Yakima River Basin, Washington (USBOR and WSDOE 2012). To meet these objectives, the integrated plan proposed numerous alterations to the structure and operation of existing reservoirs and dams within the basin. Three individual projects identified in the integrated plan are currently undergoing project-level environmental review. These include: (1) the Kachess Drought Relief Pumping Plant (KDRPP), (2) the Keechelus-to-Kachess Conveyance (KKC), and (3) the Cle Elum Pool Raise. How these proposed water management alterations might impact food web structure and populations of sensitive species (i.e., bull trout Salvelinus confluentus) within these reservoirs remains a key uncertainty for the environmental review process. However, before potential impacts can be identified and assessed, a contemporary understanding of the food web structure of these reservoirs is needed. Information on the physical and biological characteristics of Kachess and Keechelus Reservoirs is most limited. The purpose of this study was to synthesize existing information with new data to fill key knowledge gaps regarding the physical environment, food web structure, and predator–prey interactions in Kachess and Keechelus Reservoirs as they relate to supporting the production of bull trout. This information will (1) help identify important trophic pathways (i.e., pelagic vs. benthic production) supporting adult bull trout in these reservoirs, (2) provide key baseline data needed to consider the suitability of these reservoirs as potential rearing habitats and migratory corridors for reintroduced anadromous salmonids, and (3) aid in the project-level environmental review for KDRPP and KKC.