Investigation of the Effect of Climate Change on Some of Hydrological Parameters in Jamishan Watershed using SWAT Model

The increase in greenhouse gases in recent decades and the resulting increase in temperature have upset the balance of the planet's climate system and caused widespread climate change in most parts of the world. In this study, first the SWAT model was calibrated for Jamishan watershed. The calibration and validation stages, NS and R2 coefficients were 0.6, 0.61, 0.52, and 0.54, respectively. According to the results of sensitivity analysis in the region, it was found that among the 20 parameters affecting runoff, the curve number was the most important parameter. Then, the values of temperature and precipitation for the next period based on the climate change scenario were subscaled with the outputs of the HadCM3 general atmosphere rotation model for the three scenarios A2, B1 and A1B using the LARS-WG model. Later, in order to simulate the watershed runoff, the data were introduced to the SWAT model and the results showed that the runoff in the statistical period of 2015 and 2026 increased by 6, 7 and 6% respectively compared to the observation period in each scenario A2, A1B and B1 and this shows the impact of climate change on runoff in the near future from 2016 to 2026. This study showed that changes in meteorological parameters will lead to significant changes in hydrological regime such as watershed runoff. Increasing rainfall and temperature are likely to cause floods in the region in the future.