California Institute for Energy and Environment (CIEE)

This paper explores water management adaptation in California to warm-dry and warm-only climate warming scenarios from the updated scenarios for the California Climate Change Scenarios Assessment 2008. CALVIN, an optimization model of California’s intertied water supply system, is employed to explore adaptation strategies for year 2050. EBHOM, an optimization model of high-elevation hydropower systems in California, is used to estimate adaptation in energy generation. A historical (1921–1993) hydrology is used as a reference. The warm-dry scenario is developed using permutation ratios for a 30-year downscaled simulation (from the Geophysical Fluid Dynamics Laboratory’s CM2.1 model using the Special Report on Emissions Scenarios A2 scenario) centered at 2085. The warm-only scenario was developed based on the warm-dry hydrology, preserving the early snowmelt from the warm-dry scenario while maintaining the mean annual flows of the historical hydrology. This will aid separation of precipitation and temperature effects for adaptation to climate change. Agricultural and urban water uses for the year 2050 are obtained from two ancillary models. Results predict significant adaptation to warm-dry and warm-only climates. Water scarcity occurs from the drier climate in the warm-dry scenario, with increasing competition among water uses. Early snowmelt and peak storage characterize warmer climate scenarios in California. Warm-only scenario scarcity costs are significantly less than for the warm-dry scenario.