Climate change impact on the estimation of reference evapotranspiration, water requirement, and irrigation requirement in irrigated areas (a case study: Bardsir plain)

Abstract

Abstract Climate change impacts have been felt deeply by farmers of the Bardsir region, which is situated in the southeast of Iran. The current research focuses on the climate change impacts on the region's agricultural sector by the horizon of 2051. In the first step, by means of data generated by two micro lysimeters, the best-localized formula for estimating reference evapotranspiration was derived. Then the irrigation requirements of wheat, barley, rape, corn, alfalfa, potato, and onion crops were estimated by GFDL-ESM2M and Had GEM2-ES model outputs with two scenarios, RCP4.5 and RCP8.5. According to the findings, under both scenarios, the irrigation requirements of all plants will be increasing. Assuming that the current water consumption patterns remain unchanged, this will increase the total annual water demand of the plain from its present value of 331.9 to 369.66 million cubic meters (MCM) in the RCP4.5 scenario and 375.58 MCM in the RCP8.5 scenario based on GFDL-ESM2M model output. These values would be 345.11 and 349.85 MCM for RCP4.5 and RCP8.5, respectively, based on Had GEM2-ES model output by 2051. To conserve the current cultivation area, GCM models indicate, under a pessimistic scenario, even after modernizing the irrigation systems of the region the plain will encounter negative balance due to groundwater overdraft.