The Impact of Climate Change on Watershed Runoff and Sedimentation Using SWAT and WEPP Models (Case Study: Dehbar Basin)

Climate change is one of the most important factors influencing the hydrological cycle.The present study investigate the impact of climate change on runoff and sedimentation of the Dehbar watershed for the next 30 years using statistical model, LARS-WG and conceptual hydrological model, SWAT and WEPP. First, LARS-WG model was calibrated to generate future meteorological data in the basin. Then, the HadGEM2 model with three scenarios; RCP8.5, RCP4.5 and RCP2.6 were used to downscale meteorological data for period of 2020 to 2050. The results indicate a decrease in rainfall and an increase in temperature on the horizon of 2050. Also, the results of SWAT model show the runoff variations for RCP8.5, RCP4.5 and RCP2.6 scenarios which are -22.16%, -17.93% and -17.34%, respectively, and for sedimentation variations which are -4.4%, +9.4% and +3.2%, respectively, relative to the base period. In the WEPP model by choosing the hillslop method and using downscaled results of RCP8.5, RCP4.5 and RCP2.6 scenarios, sediment variations were estimated -6.4%, +12.6%, and +4.8%, respectively, compared to the base period.