Sensitivity of Columbia Basin Runoff to Long-Term Changes in Multi-Model CMIP5 Precipitation Simulations

Tuesday, 16 December 2014
Mehmet Cuneyd Demirel, Portland State University, Portland, OR, United States and Hamid Moradkhani, Portland State University, Civil and Environmental Engineering, Portland, OR, United States
In this study, we used precipitation elasticity index of streamflow to reflect on the sensitivity of streamflow to changes in future precipitation. We estimated precipitation elasticity of streamflow from: (1) observed streamflow and precipitation; (2) simulated streamflow by the VIC model using simulated precipitation from a multi-model CMIP5 dataset for the current climate (1970–1999); (3) simulated streamflow using simulated precipitation from a multi-model CMIP5 dataset for the future climate (2040–2080) including two different pathways (RCP4.5 and RCP8.5). The hydrological model was calibrated at 1/16 latitude-longitude resolution and the simulated streamflow was routed to the subbasin outlets of interest. We used hydrological model simulations from 1970-1999 and calculated runoff sensitivities for 1980-1999 using observed climate (case 1) and simulated climate (case 2). The runoff sensitivity to long-term (e.g., 20-year) average annual and seasonal changes in precipitation is calculated based on the elasticity of streamflow for reference historical period (1970-1999), which are of importance to reservoir management in the Columbia River basin (case 3). These three cases are compared to assess the effects of forcing by different climate models and different pathways on the precipitation elasticity of streamflow.