Runoff Variation of the Nianchu River in Yarlung Tsangpo River Basin and Its Response to Climate Change

This paper analyzed the natural runoff data,monthly temperature and precipitation data of Xigaze Hydrological Station,the control station of Nianchu River basin on a tributary of the Brahmaputra River,from 1956 to 2012,to explore the variation characteristics of precipitation,temperature and runoff. Then it used the monthly water balance model to simulate the monthly changes of runoff in Nianchu basin,and verified the adaptation of this model in the research area. The results prove that: the monthly change of runoff is relatively stable in Nianchu River basin,but annual distribution of runoff is uneven as the discharge of flood season and dry period varies a lot,where the former covers 67% of annual runoff; by analyzing the parameters of monthly water balance model,the sensitive parameters in Nianchu River basin are soil water storage capacity( STC) and direct runoff coefficient( drofrac); the sensitivity analysis of impact of climate change on runoff shows that the increasing precipitation has more sensitive impact on runoff than that of the reducing precipitation,and the temperature rise has less effect on runoff.