Impact of climate change on the runoff regime of an Eastern Himalayan river basin

The present study has been carried out for the trans-boundary Subansiri sub-basin of Brahmaputra river basin. Subansiri is the largest tributary of Brahmaputra within India and the river system has its practical importance as it holds a high water resources as well as hydropower potential for the country, which still remains highly under-developed. The probable impact of climate change has been analyzed using hypothetical climate scenarios to understand the behavior of total streamflow as well as snowmelt runoff under the changing conditions. Based on the simulations of a daily snowmelt runoff model (SNOWMOD) using six years of data, it has been observed that the total stream flow as well as the snowmelt runoff increase with temperature. Snowmelt runoff was found to increase by about 5% and 12% for the increase of 1°C and 2°C in temperature respectively.  However, not much change in snowmelt runoff was observed with changed precipitation scenarios. It has been found from this study that total stream flow changes in all scenarios of temperature (T) and precipitation (P). The observed maximum % increase in mean annual stream flow was about 6% for the T+2°C & P+10% scenario and the minimum % decrease in mean annual stream flow observed was about 11% for T+1°C & P-10% scenario. The present study aims to provide information for planning of climate change adaptation strategies for the Subansiri sub-basin of the Brahmaputra River.