The effects of climate change on water requirement of apple tree during the growth period A case study of Orumiyeh and Semirom stations

Water and food security are serious challenges in climate change studies. the purpose of this study is to investigate the effects of climate change on water requirements of apple during the growing season. For this purpose, the ECMWF database has been used for observation data of Semirom and Urmia stations during the 20-year period (1996-2001).To check this quantity in the next 20 years, the daily  Downscaling dynamic data of the CORDEX project with a precision of 44% * 44% for the output of the ICHEC-EC-EARTH model under the two lines of 4.5 and 8.5 (RCP) was used for the period (2017-2037). In order to reduce the errors in the model estimates, the post-processing action of the estimated events was fulfilled. Then, minimum temperature data, maximum temperature, relative humidity, wind speed and radiation, potential evapotranspiration have been calculated using Penman-Monteith FAO method, which is more accurate than other models, and using the non-parametric Man-Kendall test and the Sen’s Slope estimator nonparametric Method in the confidence range, 95% evapotranspiration was determined. In the end, the water requirement was also examined during the growing season of apples. The results showed that evapotranspiration in both stations is increasing during the growing season. The ETo increase in the growing season of the apple tree stations was predicted from the base period for the trajectory of 4.5 and 8.5 for the Semirom 4.14.7 and 7.99.7, respectively, and for Orumiye Station, 26.5 and 11.8, respectively, and however, this increasing process will raise the apple's need for water. The highest amount of evaporation and water requirement in the observed and estimated data has occurred in the bud break periods, growth fruits. At this stage, the lowest effective rainfall and the highest average temperature have occurred but generally, the percentage of upcoming changes of germination stage was more than other stages.