Assessing impacts of climate change in a semi arid watershed using downscaled IPCC climate output

This presentation discusses our research aimed at helping water managers at Salt River Project (SRP), Phoenix, assess long term climate change impacts for the Salt and Verde River basins, and make informed policy decisions. Our goal is to assess the change in future 100 year water balance variables in comparison to past observations by development, application and testing of a physically based distributed hydrologic model forced by downscaled IPCC climate information. The variable infiltration capacity (VIC) model is set up to simulate historical observed streamflow at the outlet of Salt and Verde River basins using gridded observed precipitation and temperature data. The model is calibrated using the Shuffled Complex Evolution (SCE-UA) method incorporating observed climate elasticities of the Salt and Verde River basins. The MPI-ECHAM5, UK-HADCM3 model output for three emission scenarios used in the IPCC fourth assessment were chosen and statistically downscaled to be incorporated with the VIC model. This forcing dataset was used to analyze the basin scale responses to climate change. In this presentation, the scenarios based on future climate forcing data will be presented. In addition results from a synthetic study using downscaled future temperature and past precipitation and vice versa will be presented to check the robustness of the model to non-stationary input.