Impact of climate change on surface runoff: a case study of the Darabad River, northeast of Iran

Climate change is one of the major challenges affecting natural ecosystems and various aspects of human life. The effects of global warming on the hydrology and water cycle in nature are very serious, and the quantitative recognition of these effects creates more readiness to deal with its consequences. In the present study, the 2006–2100 period is predicted based on the statistical downscaling model (SDSM). Finally, the effects of climate change on the hydrological conditions in the Darabad watershed are simulated using the Soil and Water Assessment Tool (SWAT) model. The SWAT model calibration is done based on the SUFI-2 algorithm, and the effective and optimal parameter is identified. The results of the study, while confirming the efficiency of both SDSM in climate simulations and SWAT in hydrological simulation, showed that the increase in precipitation and temperature is probably in future climate conditions for the 2010–2040 period. The surface flow and runoff at the watershed area during the observation period (1970–2010) is 0.29 m3/s, but this value for the predicted period with regard to climate change in the RCP 2.6, RCP 4.5, and RCP 8.5 scenarios is equal to 0.43, 0.44, and 0.45 m3/s. The results of research, while highlighting the importance of effects of climate change, make it essential to apply them for proper management in order to adapt to climate change in the future policies of the Darabad watershed management. HIGHLIGHTS Evaluation of climate change effects on surface runoff.; SWAT model, the best simulation daily runoff for watershed.; The model predicted average temperature increase by 2006–2100 of 6 °C by the CanEMS2.; Precipitation in the upcoming period of 2006–2100 shows a 52% increase.; The runoff in the upcoming periods of 2006–2040 under RCP 2.6, RCP 4.5, and RCP 8.5 scenarios is increased by 45, 49, and 50%, respectively.