California Institute for Energy and Environment (CIEE)

The work presented in this paper shows an estimate of the impacts of climate change on two high-elevation hydropower systems in California: the Upper America River Project, operated by Sacramento Municipal Utility District in Northern California, and the Big Creek system, operated by Southern California Edison in Southern California. The study builds on previous work modeling the Upper American River Project System. The model presented here includes methodological improvements to better simulate historical operations and more accurately project future operations of both hydropower systems. The operations of these two highelevation systems were simulated using historical and climate change scenarios. Hydrologic scenarios under climate change imply an average reduction in runoff for both systems (with a greater reduction for the Big Creek systems) and a change in the hydrograph towards earlier timing of runoff. The change in the hydrograph is greater for the Upper America River Project system because of the lower elevation of the basins where the system is located. The simulation results show that associated with the reduction in runoff there is a reduction in energy generation in both systems. However, due to the greater change in the hydrologic conditions for the Upper America River Project system, spills are greater in that system, and hence the reduction in energy generation (and associated revenues) is greater as well. In both systems the ability to meet peak historical power demands in the summer months would remain basically unaltered. However, an increase in the occurrence of heat waves especially later in the summer period (September) would increase peak power demand at times when these systems might not be at peak power capacity unless operating strategies are modified.