CS29A - Concurrent Session 29A: Climate Vulnerability Assessment for Possible Hot-Dry and Warm-Wet Future Climates for Dams in California

Work supporting Southern California Edison’s (SCE) evaluation of the hydrologic hazards of dams under future climate conditions as recommended by the California Public Utilities Commission (CPUC) Climate Vulnerability Assessment will be presented.

Hydrometeorological inputs to a stochastic hydrologic model were adjusted based on global climate model output (CMIP5), provided on cal-adapt.org, to quantify the effects of anthropogenic climate change. Predicted changes in temperature and precipitation (per month) between a historical reference period (1986-2005), and a forecast period (2006-2100) were used to represent two future climate scenarios: hot-dry (hotter temperatures with diminished precipitation magnitudes) and warm-wet (warmer temperatures with enhanced precipitation magnitudes). The most severe scenario, RCP 8.5, was used in the analysis per CPUC recommendations.

The Stochastic Event Flood Model (SEFM) was used to develop hydrologic hazards for the time horizons 2050 and 2070. Climate-adjusted magnitude-frequency relationships for peak reservoir inflow rate, peak reservoir release, maximum 72-hour reservoir inflow volume, and maximum reservoir water surface elevation are presented for each.

The greatest changes in projected precipitation magnitudes occurred in the winter months, which, along with changes in temperature and freezing level, affects snowpack. Temperature is projected to increase throughout the year, with the greatest increases in the summer months.

The Mid-latitude Cyclone (MLC) storm type hydrologic loading curves increased (were more severe, more common) for the warm-wet scenario and decreased (were less severe, less common) for the hot-dry scenario for both future time horizons. The local storm hydrologic loading curves decreased (were less severe, less common) for both scenarios for both future time horizons. The annual exceedance probability of dam overtopping is presented in the tables below for current climate conditions and both climate change scenarios.