Forecasting Reservoir Operations to Address Climate Impacts on Fish Sustainability Below Shasta Lake

River regulation is a major issue on freshwater ecosystems worldwide, changing natural lotic river systems into fragmented networks of regulated flows and artificial ‘lentic' reservoirs. In some cases, scientists and managers have advocated adjusting dam operations to lessen riverine impacts to aquatic ecosystems. The potential implications of climate change on stream temperatures is an additional consideration for water managers as any variability in the regional and local hydroclimatology would impact stream temperatures. Reservoir re-operation may be a useful strategy for managing downstream temperatures to mitigate for detrimental climate change impacts. In this project funded by the NOAA Sectoral Applications and Research Program, we are partnering stochastic weather generation with two-dimensional hydrodynamic modeling of reservoir operations using CE-QUAL-W2 to examine the feasibility of meeting downstream temperature targets for the salmon fishery on the Sacramento River in California below Shasta Lake. The coupling of these modeling approaches allows us to examine how climate forecasts can be used to inform reservoir operations decisions for downstream fisheries management. Our project aims to examine the impacts of climate variability on meeting downstream temperature targets for Chinook salmon and assess the ability of using reservoir operations to meet downstream temperature targets under current and projected climate conditions. We are interacting with water managers for the reservoir and the Sacramento River to employ methods of decision-making and institutional analysis to represent how managers make decisions about multipurpose demands in reservoir operations. As part of the project, we are developing stochastic daily inflow with sub-daily weather scenarios for Shasta Lake under historic and future climate conditions, implementing workshops with reservoir managers to obtain operating guidelines and decision-making criteria, simulating historic and future climate scenarios with operations guidelines from managers using the CE-QUAL-W2 mode, and assessing outflow temperatures from the CE-QUAL-W2 model regarding meeting downstream temperature targets for the scenario runs. This project will demonstrate how human-operated systems can be incorporated with analysis of operational guidelines and decision-making constraints to minimize detrimental climate impacts to fisheries in the Sacramento River and the Sacramento-San Joaquin Delta. In this presentation, we will present results of initial scenario runs and their implications.