Assessing California streamflow under present day and a 2040 to 2049 climate change scenario

Coupled climate system models are useful tools for understanding the range of uncertainty in potential greenhouse warming impacts. As part of a coordinated end-to-end climate scenario and impacts analysis study in California, we have simulated a set of representative river systems for input to water demand, vegetation, and agro-economic models. The focus of this presentation is on the flow of hydrologic climate change from large-scale HadCM2 output through regional mesoscale models (RegCM2, RCSM, and HIRHAM) to the watershed basin scale, simulated by the Sacramento model. We have selected twelve representative river basins, including watersheds from the California Department of Water Resources eight river index, and simulated mean monthly streamflow climatologies. Sets of ten-year regional model simulations driven by NCEP reanalysis for 1979 to 1988, HadCM2 output for late twentieth century, and HadCM2 output for a 2040 to 2049 scenario provide input to the Sacramento model. An analysis of observed streamflow and simulated streamflow forced by observations, RegCM2, RCSM, and HIRHAM is provided. Bias, variance, and confidence in the climate change response are discussed.

The results from this study are providing input to the VEMAP models of ecosystem behavior and several California-specific water demand and agro-economic response models as part of a California Energy Commission impacts study on California climate change.