Examining Climate Change Effects on the Use of Stormwater for Alternative Water Supply: A Method to Conduct Continuous Simulation Hydrologic Modeling with Global Climate Model Results

The potential impact of climate change on the effectiveness of stormwater capture facilities used for alternative water supply was examined using continuous simulation hydrologic modeling. A methodology was developed to transform future projected daily precipitation simulated from regionally downscaled global climate models (GCMs) to hourly time series. The methodology was tested on historic measured rainfall for Oakland, California, and was applied to projected future daily GCM precipitation results for two regions in California: the Monterey Peninsula and Santa Clarita, California. Hourly time series were input into an hourly continuous simulation hydrologic model framework to enable comparison of estimated stormwater facility capture under historic precipitation conditions and projected future precipitation conditions for the Monterey Peninsula region for a range of GCMs. The results of the comparison demonstrated differences in total precipitation, total water captured by facilities ranging in size and drawdown time, and the facility performance in terms of percent of average annual runoff captured.