Projected Discharge of Dudhnai River: A Tributary of the Brahmaputra River

The present study assessed the impact of climate change on the discharge of a mountainous watershed-Dudhnai, India, using the Soil and Water Assessment Tool (SWAT). First, the SWAT model was calibrated and validated using rainfall and observed discharge data. Then, bias-corrected meteorological data from four climate models (CCSM4, CNRM-CM5, MPI-ESM-LR, and NorESM1-M) from two emission scenarios (RCPs 4.5 & 8.5) were used to predict future discharge. The model efficiencies and per cent bias indicated that the SWAT model was subpar (NSE = 0.54) at daily timescale, however, performed better at monthly timescale with an NSE of 0.70. According to the ensemble of climate models, in comparison with the baseline discharge scenario, the discharge in the watershed was projected to increase towards the end of the century by about 16.6% under RCP 4.5 and 27.5% under RCP 8.5. The mean monthly variation of discharge in the Dudhnai indicated that monsoonal discharge would increase in the future, while cases of a decrease in discharge were observed during lean flow periods, particularly during November to March. The rate of increase in the surface flow component was found significantly greater than the lateral and groundwater flow components. Results imply that the Dudhnai watershed would be subjected to severe hydrological events in the future. Despite the potential growth of water resources, their distribution patterns may cause water scarcity in the watershed, especially during dry seasons.