Impact of Climate Change on Runoff Generation in the Upper Godavari River Basin, India

The probable impacts of climate change on water resources are of great concern to hydrologists, water managers, and policymakers. The impact of climate change on hydrological variables in the upper Godavari River basin has not been studied and was the focus of this research. Two general circulation model (GCMs), the Hadley Centre Coupled Model, Version 3 (HadCM3) and the Canadian Centre for Climate Modelling and Analysis’s Coupled Global Climate Model, Version 3 (CGCM3), which have been shown to produce good results in India, were used to study climate change impacts in the study area. Downscaled projected results of a statistical downscaling model (SDSM) were used to simulate runoff for future climatic scenarios using the soil and water assessment tool (SWAT). The SWAT model was calibrated using the sequential uncertainty fitting algorithm. The Nash–Sutcliffe efficiency (NSE) and the determination coefficient ($R^2$) were used for performance assessment during calibration and validation. The values of both NSE and $R^2$ were 0.63 during calibration and 0.71 during validation for the daily time step. The SWAT simulation results showed that at the end of the 21st century, the increase in runoff will be 70% and 61% under Scenarios A2 and A1B (obtained using the CGCM3 model) and 47% and 36% under Scenarios A2 and B2 (obtained using the HadCM3 model). Because the downscaling results showed a greater $R^2$ value for the HadCM3 model than for the CGCM3 model, the runoff scenario developed using the HadCM3 model will be used for future water resource planning and management.