Assessing the impacts of climate change on the future droughts in Gorganroud Watershed under CIMP6 models

The characteristics of drought, as one of the environmental events, may change under the effect of climate change in future periods. The current study was conducted with the aim of predicting meteorological drought in Gorganroud watershed. For this purpose, the output of temperature and precipitation of 8 General Circulation Models (GCMs), were investigated under two scenarios (SSP2-4.5) and (SSP5-8.5) during two periods of 2025-2054 and 2071-2100. To downscale the GCMs, quintile mapping bias correction method was used. After projecting the future precipitation and temperature, the SPEI index was calculated at the annual scale for the baseline and future periods. Thereafter, the drought characteristics (duration, intensity and Severity) were computed using the median results of SPEI bands based on the Run theory method. With the aim of improving the process of evaluating and quantifying the effects of climate change on future droughts in the region and showing the uncertainties caused by climate models, the prediction bands of climate variables have been used to quantify the SPEI index. According to the simulated results of performance of multi model ensemble, that in the future climate conditions, the average values of mean temperature and precipitation will increase in both scenarios; So that the temperature increases from 1.2 to 4.4 Celsius and precipitation increases by 2 to 11.9 percent. The results of this study show that the conditions of the region in the coming decades likely the normal or wet climate conditions in the near decades, but these conditions would change in the far future as the more we move towards the last decades of the century, the more occurrences of droughts would happen. The results obtained from of the Run theory indicate that the duration and magnitude intensity profiles will decrease in the SSP2-4.5 scenario and the near future period in the SSP5-8.5 scenario.