A. Dehghan Moroozeh - Department of Water Engineering, Faculty of Agriculture, Razi University, Kermanshah, Islamic Republic of Iran.
B. Farhadi Bansouleh - Department of Water Engineering, Faculty of Agriculture, Razi University, Kermanshah, Islamic Republic of Iran.
M. Ghobadi - Department of Plant Production and Genetics, Faculty of Agriculture, Razi University, Kermanshah, Islamic Republic of Iran.

Climate change can have significant impacts on crop growth, yield, water requirement and, consequently, crop water productivity. In this study, the effect of climate change under RCP۲.۶, RCP۴.۵, and RCP۸.۵ projection scenarios of the CanESM۲ model on soybean yield and water requirement was investigated in Kermanshah, west of Iran. Crop growth was simulated using crop growth simulation models (DSSAT and AquaCrop) based on historical (۱۹۸۵-۲۰۱۵) and projected (۲۰۲۵-۲۰۶۴) weather data. Using the AquaCrop model in RCP۲.۶, RCP۴.۵, and RCP۸.۵ scenarios, the average increase in seasonal crop evapotranspiration (ETc) was estimated to be ۹.۴, ۱۱, and ۱۴.۹%, respectively. The results of the DSSAT model showed ۴.۱, ۸.۵, and ۱۲.۱% increase in seasonal ETc under the RCP۲.۶, RCP۴.۵, and RCP۸.۵ scenarios, respectively. Based on the AquaCrop and DSSAT models, soybean yield decreases by ۵.۳, ۳.۷, and ۲% and by ۵.۷, ۴.۸, and ۱.۶% for the RCP۸.۵, RCP۴.۵, and RCP۲.۶ scenarios, respectively. The results also show a decrease in crop water productivity under climate change scenarios as a result of increased ETc and reduced grain yield. According to AquaCrop and DSSAT models, the maximum daily ETc that should be used for the design of irrigation systems will increase by ۱۱.۵ and ۱۰.۲%, respectively.

AquaCrop, CanEsm۲, Crop yield, DSSAT.