Projection of the temperature and precipitation impacts on the runoff using a representative concentration pathway scenario in the Agh-Darband basin, Iran

Assessment of the impact of climate change on the hydrological cycle of river basins plays an essential role in managing water resources in areas facing challenges in future periods. Hydrological models are used as a tool for water and soil management in watersheds, which is a framework for assessing the relationship between climate, human activities, and water resources. The present study investigates the impact of future climate changes (2041–2060) on runoff in the Agh-Darband basin. The Soil and Water Assessment Tool (SWAT) model was used. At the first step, the runoff was calibrated and validated from 1980 to 2011. The most sensitive parameters were moisture condition II curve number (CN2) and baseflow alpha factor (ALPHA_BF) in the Agh-Darband basin. The model simulation results showed acceptable performance for monthly simulation runoff in the study area. Then, the climatic data using the HadGEM2-ES model were micro-scaled under the Representative Concentration Pathway (RCP) 8.5 emission scenario with the LARS-WG model during 2041–2060. Also, the performance of the LARS-WG model to generate climatic data was evaluated. The results indicated that it generated satisfactory results. In the next section, the micro-scale data were introduced to the SWAT model, and runoff changes were examined for the future. The results showed that maximum and minimum temperatures will increase by 3.36 °C and 3.23 °C, respectively, during 2041–2060 in the Agh-Darband basin. Precipitation will vary between 54 and −95% under the RCP8.5 scenario in different months. The amount of runoff in the future period will decrease between 97 and 100% in different months. Graphical abstract