Application of HVB Model for Studying the Effect of Climate Change on Hydrological Drought in Zayendehrood River Basin

Green house gases extend have caused to intensity the climate change and their negative impact on human communities are one of the main disturbances of human in 21st. century. The climate change phenomenon has different impact on various systems. The vital role of water on human life causes the study of these negative impacts on severity and occurrence of drought events in a region to be very important. In this study, three Global Climate Models (GCMs) output (precipitation and temperature), bias corrected with the WATCH Forcing Data (WFD), for the A2 and B1 scenarios, are used for drought assessment at a basin scale. The produced hydrological variables, flow, soil moisture and lower groundwater reservoir volume were used for the hydrological regime assessment and drought identification with the aid of the threshold level method. For A2 scenario, it was found that the number of drought events could increase up to 98%, 109% and 81% in flow, soil moisture and groundwater respectively. B1 scenario provided more conservative estimates, with an increase of drought events number up to 56%, 92% and 34% in flow, soil moisture and groundwater, respectively. The drought duration difference between scenarios reaches up to 33%, 89% and 34% for simulated flow, soil moisture and groundwater respectively till 2100. Moderate changes can be noticed in drought deficit volume with an estimated maximum increase of 19%, 33% and 22% in flow, soil moisture and groundwater involving A2 scenario, whereas B1 scenario projected 10%, 2% and 26% maximum increase for the former parameters. The evolution of the hydrological parameters is in line with the projected decreasing precipitation and increasing temperature trends.