Estimating of Future Agricultural Drought by Use of the SMDI Index and Data of the Fifth Report on Climate Change

Moisture content of surface soil is an important variable in nature's water cycle, which plays an important role in the global equilibrium of water and energy due to its impact on hydrological, ecological, and meteorological processes. Soil moisture is a determining factor in many complex environmental processes and plays a determinative role in the occurrence of agricultural drought. In this study, based on estimated soil moisture data by SWAP model and data of the IPCC Fifth Assessment Report, agricultural drought was determined by the use of soil moisture deficit index for the future period. The climatic data was estimated using six GCM models and two RCP4.5 and RCP8.5 emissions scenarios, and downscaled by LARS-WG model, and was entered into the SWAP model. Finally, by using soil moisture data of 30 cm depth, agricultural drought was evaluated using SMDI index. The results of climate parameter changes showed that the minimum and maximum temperatures and rainfall in the future period would increase compared to the base period and RCP8.5 scenario estimated higher temperatures and less rainfall than RCP4.5 scenario. Results of estimated SMDI values for the future period showed that RCP4.5 scenario has a higher average of SMDI amount than RCP8.5 scenario. Also, both scenarios show the normal moisture amount for future period and the predicted SMDI amount for the future period is higher than the base period.