Analyzing future water availability and hydrological extremes in the Krishna basin under changing climatic conditions

The present study aims to investigate the impact of climate change on water availability and hydrological extremes in the Krishna River basin, the second largest eastward draining river of Peninsular India. The hydrological response of the basin for the past observed climatic data (1985-2005) and future climatic scenarios (RCP 4.5 and RCP 8.5, respectively, for 2006-2099) is simulated using the Variable Infiltration Capacity (VIC) model. The soil, vegetation, topographic, and meteorological inputs for the model are derived from remote sensing and field-observed data. The model calibration is performed using observed discharge data at 4 gauging stations for the time period of 21 years (1985-2005); the coefficients of determination (R-2) are in the range of 0.81-0.95. The model validation is carried out at the Vijayawada station (R-2 = 0.82), near the basin outlet. The meteorological forcing consisting of future climatic inputs for the entire century (2006-2099) for RCP 4.5 and RCP 8.5 scenarios extracted from IITMRegCM4-4 predictions are used to simulate the future hydrological regime of the basin. The hydrological response analysis shows increase in annual discharge by 13.8 and 27.8 cumec under RCP 4.5 and RCP 8.5, respectively. The hydrological extreme events are also found to increase under RCP 4.5 and RCP 8.5 scenarios as compared with the past records of 1985-2005. The peak discharge is observed to increase in the range of 57.7-76.8 and 68.5-77.5% under RCP 4.5 and RCP 8.5, respectively. The study highlights that the annual water potential and hydrological extremes in the Krishna basin will increase under the future climatic scenarios.