Investigation of Climate Change Impact on Hydrological Behavior of Arazkoose Watershed based on Runoff Indices

In this study the HBV hydrological model and runoff indices have been applied to investigate the impacts of climate change on runoff in the ArazKoose watershed. Therefore, the projected future temperature and precipitation under the three representative concentration pathways (RCPs) 2.5, 4.5 and 8.5 scenarios for the first future epoch (2031-2051) and the second future epoch (2051-2071) were incorporated into the calibrated HBV model. The Dynamic Dimension Selection (DDS) optimization technique was used to calibrate the HBV model’s input data of precipitation, potential evapotranspiration and temperature in daily scale. Daily flow data from 1986 to 1999 and from 2006 to 2009 were used to calibrate and validate the model, respectively. The Support Vector Machine (SVM) model projected the evapotranspiration in two future epochs. Future runoff simulations compared to the base period with respect to hydrological indices of flow duration curves indicating a decreasing trend in monthly runoff of ArazKoose watershed. Furthermore, projected extreme events resulted in decreasing high flow and low flow by 60% and 25%, respectively, in the future when compared to the baseline period. While, the annual mean flow projected to increase by 25% than that of historical period in two scenarios except in RCP8.5.