Evaluation of Climate Change Effect on Estimation of Reference Evapotranspiration and Comparison with Lysimetric Data (case study, Bardsir plain)

Climate change has relatively great effects on water demand of plants by changing temperature and precipitation pattern. this investigation aims was to predict temperature and precipitation in The new future and to evaluate their effects on evapo-transpiration and water demand of alfalfa plant in Bardsir region in kerman province. The best equation for estimating real evaporation-transpiration in the region was derived by using measured data obtained by a lysimetric device in during 7 months. For this purpose, 6 common equations were studied in addition to artificial neural network techniques under different scenarios. The best equation among the presented ones was Blaney-Criddle with R2= 0.884, RMSE=0.11 and the best artificial neural network scenario was mean daily temperature scenario with R2=0.802, RMSE=1.516. Therefore, the Blaney-Criddle equation was selected as a reference for prediction. Then, the GFDI-ESM2M model was used to simulate precipitation and temperature for the near future 2020-2050. Observed Temperature and precipitation data. which were obtained from a weather station in the region, were used for the reference period of 1987-2016. Temperature and precipitation changes trends were by extracted three scenarios; under optimistic RCP2.6, medium RCP6 and pessimistic RCP8.5 scenarios, during 2020-2050. The results showed that the mean temperature for mentioned three scenarios increased by 2.5, 2.8 and 3.1 Celsius degree in the 2050 respectively, and precipitation remained virtually unchanged. In this regard, it is expected that agricultural water demand will increase 3.64, 4.69 and 5.25 mm per year, respectively compared with the reference period.