Climate Warming in California's Sierra Nevada: Potential Water Temperature Impacts and Resiliency

HYDRA Watersheds

Abstract submitted to the American Water Resources Assocation specialty meeting on Managing Water Resources and Development in a Changing Climate

Title:  Climate Warming in California's Sierra Nevada: Potential Water Temperature Impacts and Resiliency

Authors:  Sarah E. Null, Joshua H. Viers, Jeffrey Mount, Michael L. Deas, Stacy K. Tanaka

Abstract:  Global climate models predict that air temperature will rise in California’s Sierra Nevada Mountains in coming decades. Implications include precipitation as rainfall instead of snowfall, changes to runoff timing and magnitude, and warming river water temperatures. This study assesses the extent to which unimpaired river and stream water temperatures may be affected by increasing levels of climate warming in west-slope Sierra Nevada watersheds. Climate warming alternatives examined for this study include baseline meteorological conditions, and increases of 2ºC, 4ºC, and 6ºC to air temperature. Water temperature predictions for unimpaired and climate warming alternatives were estimated using a weekly one-dimensional hydrologic model (WEAP21) and an equilibrium water temperature model (RTEMP) for fifteen major watersheds of the western Sierra Nevada. We identified watersheds and stream reaches for which water temperature is most impacted by climate warming, as well as thermal variability within watersheds. Model results were analyzed to highlight water temperature resiliency, including contributing factors such as elevation, latitude, baseflow, drainage area, and stream order. This study improves our understanding of water temperature resiliency for rivers in the Sierra Nevada with climate warming, which should help balance instream habitat protection and aquatic ecosystem functioning with utilitarian water uses, such as water supply, hydropower, flood control, and recreation. Future research will include assessing water temperature resiliency with climate warming alternatives and current infrastructure, such as hydropower facilities and appurtenant works.