Application of WEAP model in predicting potential evapotranspiration under climate change SSP scenarios

Climate change has a significant impact on evapotranspiration (ET) as the one of the main components of the hydrological cycle. The main purpose of this research is to project the amount of potential evapotranspiration (ETp), under RCP scenario comparing to the baseline period using the WEAP model in the selected stations of Karkhe basin, Iran. The 1999-2019 and 2020-2100 years were considered as the baseline and future periods. The projected climatic variables by KIOST-ESM and MPI-ESM1-2-LR climate models under two climate change scenarios of SSP2-4.5 and SSP5-8.5 and the observed data of the selected stations in Karkheh basin were used to estimate the  for the future and. According to the outputs of the WEAP model, the potential evapotranspiration will increase by 2100. The highest increase was projected under SSP5-8.5 scenario by the MPI-ESM1-2-LR model, with amount of 89 mm in June and by the KIOST-ESM model, 73 mm in May. The lowest values were equal to 26 and -0.5 mm in the months of December and September, respectively. Correspondingly, these values under SSP2-4.5 scenario were estimated as 85.4, 64.3, 23.3 and -4.6 during June, May, December and September compared to the base period, which the latter indicated a decrease for September comparing to the baseline. Also, the amount of potential evapotranspiration in regions with temperate Mediterranean climates will experience more variations comparing to those with arid temperate climates.