Assessing the impacts of climate change on precipitation, temperature extremes, and runoff via Lars-WG and IHACRES: A case study of the Darband River watershed, Golpayegan Basin

Owing to its location in the arid belt, the impacts of climate change on Iran are significant. In this study, the effects of climate change on average precipitation, maximum and minimum temperatures, and Golpayegan Darband River runoff for the next 90 years were analyzed on the basis of the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC), utilizing Coupled Model Intercomparison Project Phase 5 (CMIP5) model outputs and the Representative Concentration Pathway (RCP) scenarios. The analysis was conducted via Lars-WG 6 for climate variables and IHACRES for runoff variations, incorporating historical data. According to the results, In January, the coldest month, the historical average minimum temperature was -3.26°C, expected to increase under RCP2.6 to -1.97°C (a 1.29°C rise), under RCP4.5 to -1.84°C (a 1.42°C rise), and under RCP8.5 to -0.98°C (a 2.28°C rise). in July, the hottest month, the historical average air temperature was 34.33°C, projected to rise under RCP2.6 to 35.40°C (a 1.07°C increase), under RCP4.5 to 36.96°C (a 2.63°C increase), and under RCP8.5 to 37.88°C (a 3.55°C increase). The annual average precipitation is forecasted to grow by 5.7% under RCP2.6, 1.8% under RCP4.5, and 1.9% under RCP8.5 compared with the historical period. However, the annual average runoff is projected to decline by 20.5%, 29.7%, and 35% under RCP2.6, RCP4.5, and RCP8.5, respectively.