The Effects of Climate Change on the Hydrological and Agricultural Drought Characteristics Zarinehrud Basin Using SRI and SSWI Indices and SWAT Model

In this study the drought characteristics of Zainehrud Basin have been evaluated under climate change condition using Standardized Runoff Index (SRI), Standardized soil moisture Index (SSWI) and SWAT model. The SWAT model was calibrated and validated over the period 1987-2010 using four meteorological stations and five hydrometric stations. The SRI and SSWI indices were calculated for all sub-basins during the base period (1981-2010) based on the runoff and soil moisture derived from SWAT model. Then, the downscaled results of AOGCM models presented at the AR5 under two emission scenarios were introduced to the SWAT model and the drought indices were simulated for the future period (2017-2046) and they were compared with the ones of based period. The results showed that the mean highest occurrence and continuity of drought of the whole basin in the future compared to the based period will increase by 23%, under the scenario 3 (BNU-ESM model under RCP2.6 emission scenario), and by 19.7% under scenario 4 (model BNU-ESM under the RCP8.5 emission scenario) based on SRI and SSWI respectively. Also, according to the results, agricultural drought is more sensitive to climate change than hydrological drought. Thus, it can be said that Zarinehrud basin is still in danger of continuous and long term droughts due to current trend of activities and possible climate changes in near future.