Potential impacts on hydrology and hydropower production under climate warming of the Sierra Nevada

Watersheds of the Cosumnes, American, Bear and Yuba (CABY) Rivers in the Sierra Nevada, California, are managed with a complex network of reservoirs, dams, hydropower plants and water conveyances. While water transfers are based on priorities among competing demands, hydropower generation is licensed by the Federal Energy Regulatory Commission (FERC) and regulated by federal and state laws and multi-party agreements. This paper presents an integrated river basin management (IRBM) model for the CABY region, built to evaluate management and regional climate change scenarios using the Water Evaluation and Planning (WEAP) system. We simulated potential impacts of climate warming on hydrology and hydropower production by imposing a fixed increase of temperature (+2, 4 and 6 degrees C) over weekly historical (1981-2000) climate, with all other climate variables unchanged. Results demonstrate that climate warming will reduce hydropower generation if operational rules remain unchanged, making the case for climate change induced hydrological change as a foreseeable future condition to be included in the FERC licensing process. IRBM tools such as the CABY model presented here are useful in deliberating the same.