The Impact of Climate Change on Reference Evapotranspiration in Mazandaran Province

Greenhouse gas emissions cause warming and impacting climate components and consequently affecting water demand in agricultural sector. This study aimed to identify the impact of climate change on reference evapotranspiration in Mazandaran province. For this purpose, climatic data of Gharakheil, Babolsar, Noshahr, and Ramsar weather stations were used during 1985-2005. Meteorological data for a future period (2006-2081) were estimated using the CanEMS2 model under RCP2.6, RCP4.5, and RCP8.5 scenarios and the reference evapotranspiration was calculated using climatic data for future periods. The SVM model was used for downscaling the climatic parameters. The results showed that the maximum and minimum temperatures would increase over the coming period and the annual maximum temperatures in the selected meteorological stations under RCP2.6, RCP4.5, and RCP8.5 scenarios will be increased by 1.5, 2, and 3° C, respectively. Minimum temperatures in the selected stations under RCP2.6, RCP4.5, and RCP8.5 scenarios will be increased by 3.8, 5.7, and 5.7° C, respectively. Precipitation will also be reduced between 8 to 29 percent over the selected weather stations. The results show that the reference evapotranspiration will be increased or decrease in some months in all meteorological stations compared with the base period. The highest increase in maximum temperature under different climatic scenarios will be occured in March between 1.4 to 6.4° C at Babolsar Meteorological Station, and the highest increase in minimum temperature under different climatic scenarios will be occured between 3.8 to 5.7° C in February at the Gharakheil Meteorological Station. The results showed that the highest and lowest percentages of reference evapotranspiration changes would occur in October and March, respectively. Evaluation of the reference evapotranspiration at the selected stations shows that the percentage of evapotranspiration variations in different months varies between -16.1 to 25.7% and the highest increase and decrease in reference evapotranspiration will occur in Ramsar and Gharakheil stations, respectively.