Application of hydrological model for assessment of water security using multi-model ensemble of CORDEX-South Asia experiments in a semi-arid river basin of India

This study analyses the impacts of climate change on water resources in the Banas River Basin, which is located in a semi-arid part of the state of Rajasthan in India. A bias-corrected ensemble mean of three CORDEX-SA driving GCM experiments (CNRM-CM5, CCSM4, and MPI-ESM-LR) was used with the Soil Water Assessment Tool (SWAT) to predict water yield and evapotranspiration for three future periods (2011-2040, 2041-2070, and 2071-2099) under two representative concentration pathway scenarios (RCP4.5 and RCP8.5), and the results were compared with the data of a historical period (1979-2008). The SUFI-2 method was used for the calibration and validation of the SWAT model. The model was calibrated for the period of five years (1982-1986) and validated for the next five years (1987-1991). The values of R-2, NSE, bR(2), PBIAS, and RSA were, respectively, 0.78, 0.77, 0.61, 47.4 and 0.48 during the calibration period, and 0.71, 0.65, 0.60, 72.1 and 0.59 during the validation period. Trend analysis was also performed for annual future predicted flows using the Sen Slope method. From the results, it can be predicted that precipitation, evapotranspiration, and water yield will increase in all the three future periods under both RCP4.5 and RCP8.5. Water availability in the future in the basin (zone wise) was identified using appropriate indicators. Per-capita water availability and meteorological variation were used to calculate future water availability and, considering these indicators, it can be concluded that zone 3 will better than the other zones. Zone 3 exhibits high values of per capita water availability and meteorological variation. This study will be useful in understanding the impacts of climate change on the water availability of the river basin and may help in overall water management in the present and the future.