Prediction of Monthly Potential Evapotranspiration under RCP Scenarios in Future Periods: A Case Study of Golpayegan Basin

The evapotranspiration is the transfer of energy between the Earth's surface and the atmosphere and it is the most productive mechanism of communication between the hydrosphere, lithosphere and biosphere. This study focuses on predicting potential evapotranspiration in Golpayegan basin as a response to climate change. For this purpose, six algorithms including Hargreaves-Samani, Thornthwaite, Romanenko, Oudin, Kharrufa and Blaney-Criddle and also, Penman- Monteith- FAO as a standard algorithm, were used for estimating the potential evapotranspiration. The results showed that the Hargreaves-Samani algorithm performed closer to the Penman-Monteith-FAO standard algorithm compared to other algorithms. Therefore, this algorithm was used to evaluate the potential impact of climate change in future periods on the rate of potential evapotranspiration. After that, the amount of potential evapotranspiration using general circulation models (GCM) was estimated under RCP scenarios 2.6,4.5,8.5 for near, middle and far periods of 2021-2040, 2041-2060 and 2061-2080 by the LARS-WG6 model using the HadGEM2-ES climatic model. Finally, the predicted evapotranspiration values in future periods were compared with the evapotranspiration results in the baseline period of 1992-2017 to investigate the impact of climate change on potential evapotranspiration. The results showed an increase in potential evapotranspiration under all RCP scenarios in future periods. Increase under scenarios of RCP2.6, RCP4.5 and RCP8.5 in the near future were obtained 6.31, 7.5 and 7.10 percent, In the middle future period, 9.69, 9.84 and 11.82 percent and in the distant future period, 8.17, 13.79 and 18.15 percent, respectively.