A hydrological modelling-based approach for vulnerable area identification under changing climate scenarios

The hydrologic behaviour of the Brahmani River basin (BRB) (39,633.90 km(2)), India was assessed for the base period (1970-1999) and future climate scenarios (2050) using the Soil and Water Assessment Tool (SWAT). Monthly streamflow data of 2000-2009 and 2010-2012 was used for calibration and validation, respectively, and performed satisfactorily with Nash-Sutcliffe Efficiency (E-NS) of 0.52-0.55. The projected future climatic outcomes of the HadGEM2-ES model indicated that minimum temperature, maximum temperature, and precipitation may increase by 1.11-3.72 degrees C, 0.27-2.89 degrees C, and 16-263 mm, respectively, by 2050. The mean annual streamflow over the basin may increase by 20.86, 11.29, 4.45, and 37.94% under representative concentration pathway (RCP) 2.6, 4.5, 6.0, and 8.5, respectively, whereas the sediment yield is likely to increase by 23.34, 10.53, 2.45, and 27.62% under RCP 2.6, 4.5, 6.0, and 8.5, respectively, signifying RCP 8.5 to be the most adverse scenario for the BRB. Moreover, a ten-fold increase in environmental flow (defined as Q(90)) by the mid-century period is expected under the RCP 8.5 scenario. The vulnerable area assessment revealed that the increase in moderate and high erosion-prone regions will be more prevalent in the mid-century. The methodology developed herein could be successfully implemented for identification and prioritization of critical zones in worldwide river basins.