Evaluation of the effects of SSP scenarios of Coupled Model Intercomparison Project Phase 6 (CMIP6) on water resources and agricultural crop in Hashtgerd region with the approach of applying an adaptation strategy

Considering the not very suitable state of the country's water resources as well as the phenomenon of climate change and its effects, simulating the state of climate change in the future and evaluating its effects in order to reduce vulnerability and deal with it can be very important in future decisions. In this regard, in order to reduce the negative effects of climate change and benefit from its possible positive effects in watersheds, various adaptation strategies are presented.In this research, adaptation to climate change in the agricultural sector under the CMIP6-SSP climate change scenarios has been investigated and evaluated. Considering the characteristics of the Hashtgerd region and the risks that threaten agriculture in the region, this research tries to have a comprehensive view of this system. For this purpose, adaptation strategies to reduce the negative effects of climate change in the agricultural sector were evaluated.

 In this research, the SWAT model was used to simulate and evaluate the adaptive strategy in Hashtgerd region in 2018. To model climate change conditions in the region, the NorESM2-MM climate model related to the 6th IPCC report and different SSP scenarios (SSP1.26, SSP2.54, SSP3.70, SSP 5.85) were used and minimum and maximum temperature data and the precipitation were downscaled for the years 2020 to 2049. After calculating the changes in temperature and rainfall compared to the current conditions, the values ​​of these changes were applied to the SWAT model in order to investigate its effect on the water resources of Hashtgerd region. Finally, the values ​​of water stress and crop performance were estimated under the conditions of climate change.

The results indicated an average increase in water stress and also a decrease in yield of crops other than corn in all SSP scenarios. After evaluating the effects of climate change in the region, in order to adapt to these changes in the agricultural sector, two adaptation strategies were used 1) The strategy of changing the cultivation pattern from tomato and alfalfa crops to wheat and barley and 2) Changing the cultivation pattern from tomato and alfalfa to corn. These strategies were evaluated with criteria such as changes in water stress and yield of crops compared to BAU conditions.

The results showed that changing the cultivation pattern to wheat and barley has reduced the water stress of regional crops. In general, in the strategy of changing the cultivation pattern, the yield of all three crops, wheat, barley and corn, was increased compared to the BAU strategy. In the strategy of changing the cultivation pattern to corn, a significant reduction in water stress was estimated and, accordingly, the yield of this product was acceptable. This increase in performance is due to the reduction of water stress caused by the increase in available water.