Evaluation of climate change impacts on blue and green water by using CMIP5 model in Kashafrood River Basin

Evaluation of climate change impacts on blue and green water by using CMIP5 model in Kashafrood River Basin

Hydrology cycle of river basins and available water resources (such as blue and green water) in arid and semi-arid regions are highly affected by climate changes and rainfall pattern. In this study, the impacts of climate change on virtual water parameters in Kashafrood River (KR) as a large scale basin in north east of Iran was evaluated by using Soil and Water Assessment Tool (SWAT) model in combination with the Sequential Uncertainty Fitting Program (SUFI-2) by considering sensitivity and uncertainty analysis in five runoff stations to calibrate and validate model. The Blue Water (BW), Green Water Flow (GWF) and Green Water Storage (GWS) was analyzed by MIROC-ESM model in series of the Coupled Model Intercomparison Project Phase 5 (CMIP5) and compared by two Representative Concentration Pathways (RCPs: RCP2.6 and RCP8.5) downscaled based on the observed data under three future periods: near future (2014-2042), intermediate future (2043-2071) and far future (2072-2100) relative to the historic period (1992-2013). Calibration and validation results at five stations show good performance of the SWAT model in modelling hydrological processes in this basin. Results of climate change impacts on blue and green water components show that in historic period, the basin did not have the appropriate climate conditions for accessing the water resources. Also, in future time periods, considerable spatial variations in different hydrological components has been observed. On the other hand, in both RCPs and all future periods, the blue water contents will increase about 46-74% and green water flow will decrease about 2-15% relative to historic period and results show that the conditions of basin will improve. But the green water storage tends to increase about 11-18% or decrease about 6-60% in the future. The blue water and green water flow will decrease and green water storage will increase by changing from near to intermediate-future. While changing from intermediate to far-future, blue water and green water flow in RCP2.6 will increase and in RCP8.5 will decrease, respectively and also green water storage in both RCPs will decrease.