Assessing the consequences of climate change on potential evapotranspiration in Iran in the coming decades

Potential evapotranspiration (ETP) is one of the important elements of the hydrological cycle that plays an important role in water resources management projects, agricultural studies, irrigation network design, water structures, and climate research. In the present study, the CANESM2 and GFDL exponential microscale models from the set of CMIP5 model ((RCP) scenarios) under the CORDEX project were used. The value of ETP in 52 synoptic stations in Iran for the basic period (1976–2005) and future periods was estimated using the Hargreaves-Samani method. Based on the results, future periods indicate an increase in the rate of evapotranspiration in the future compared to the base period in all seasons. The highest rate of increase will be related to the summer. In general, it is predicted that in Iran, due to the significant increase in potential evapotranspiration in summer, the water requirement of the few plants whose growth period corresponds to this season will increase significantly. Therefore, agricultural and irrigation activities during the summer should change according to the impact of climate change on water resources management. The least impact of climate change was in winter. In terms of how different scenarios affect the rate of evapotranspiration in possible future climate change conditions, the highest increase occurred in all seasonal and annual series in all stations, in the 2071–2099 and under the RCP8.5 scenario based on the CanESM2 model. Evaluation of climatic conditions shows that in the future, stations of the northern coast (such as Bandar Anzali station) and northwest of the country will have the lowest rate of evapotranspiration. Therefore, they are suitable for the growth and development of agriculture. Southwestern regions are one of the regions with relatively high potential evapotranspiration in Iran.