Impact of climate change on river flow in the Zagros Mountain Region, Iran

Long-term droughts, temperature rise, and extreme weather events cause changes in runoff, evaporation, and transpiration in basins. These changes are more severe in arid and semi-arid regions. Since 2007, the discharge of baseflow of the Zagros Mountain has decreased and made the supply of agricultural, industrial, and drinking water a big challenge. In this investigation, utilizing data from weather stations, the output of CORDEX, and the WetSpass model, the impact of climate change on river discharge in the Great Karun Basin (GKB) was examined. The temperature and precipitation projections for the period 2019-2040 were analyzed using the Coupled Model Intercomparison Project Phase Six (CMIP6) under scenarios SSP2-4.5 and SSP5-8.5. The findings reveal that the minimum and maximum temperatures are expected to increase by 0.2℃ to 5.1℃ and 0.1℃ to 3.6℃, respectively. Annual precipitation will decrease between 1.3% and 16.7% in scenario SSP2-4.5 and 23.4% in scenario SSP5-8.5. The results of the WetSpass Model for predicting future scenarios indicate a decrease in direct flow (5%), total discharge (27%), and interception (15%). As evapotranspiration will increase by 15% due to climate change, it will be more difficult to predict the water resources' volume of the Karoun Basin for the next decades. Adapting to climate change is the appropriate solution to solve this problem. Changes in temperature and precipitation in these areas pose major challenges to water resources.