DEVELOPMENT AND APPLICATION OF A DECISION SUPPORT SYSTEM FOR WATER MANAGEMENT INVESTIGATIONS IN THE UPPER YAKIMA RIVER, WASHINGTON

The need for better integration of science and decision making in environmental management is widely documented. In light of anticipated climate change and associated changes in demographics, land use, and water management practices, decision makers are confronted with the need to make major decisions in the face of high system complexity and uncertainty. The integration of useful and relevant scientific information is necessary and critical to enable informed decision-making (Liu and others, 2008). The Yakima River Decision Support System (YRDSS) was designed to quantify and display the consequences of different water management scenarios for a variety of state variables in the upper Yakima River Basin, located in central Washington. The impetus for the YRDSS was the Yakima River Basin Water Storage Feasibility Study, which investigated alternatives for providing additional water in the basin for threatened and endangered fish, irrigated agriculture, and municipal water supply. The additional water supplies would be provided by combinations of water exchanges, pumping stations, and off-channel storage facilities, each of which could affect the operations of the Bureau of Reclamation’s (BOR) five headwaters reservoirs in the basin. The driver for the YRDSS is RiverWare, a systems-operations model used by BOR to calculate reservoir storage, irrigation deliveries, and streamflow at downstream locations resulting from changes in water supply and reservoir operations. The YRDSS uses output from RiverWare to calculate and summarize changes at 5 important flood plain reaches in the basin to 14 state variables: (1) habitat availability for selected life stages of four salmonid species, (2) spawning-incubation habitat persistence, (3) potential redd scour, (4) maximum water temperatures, (5) outmigration for bull trout (Salvelinus confluentus) from headwaters reservoirs, (6) outmigration of salmon smolts from Cle Elum Reservoir, (7) frequency of beneficial overbank flooding, (8) frequency of damaging flood events, (9) total deliverable water supply, (10) total water supply deliverable to junior water rights holders, (11) end-of-year reservoir carryover, (12) potential fine sediment transport rates, (13) frequency of events capable of armor layer disruption, and (14) geomorphic work performed during each water year. Output of the YRDSS consists of an extensive series of conditionally formatted scoring tables, wherein the changes to a state variable resulting from an operational scenario are compiled and summarized. This convention was designed to provide decision makers with a quick visual assessment of the overall results of an operating scenario, but the large number of individual output tables made comparison of competing scenarios difficult in practice. In order to demonstrate a better way of presenting YRDSS results we developed a graphical user interface (GUI) that assisted with navigating DSS output. This interface was designed to provide decision makers with summary charts comparing operating scenarios but added the ability to progressively drill down to the specific data and modeling behind the summary statistics. Additionally, we provide decision makers with insight into our spatial habitat modeling by embedding a simple GIS into the DSS which allows a user to visually inspect the species habitat data and the inputs that went into its creation.