Hydrological Rule and Isotopic Composition of Water Bodies in Yarlung Zangbo River

Based on data of runoff and water isotopic compositions in the Yarlung Zangbo River,this paper mainly analyzes the spatio-temporal distribution of runoff and isotopic effect of precipitation in this area. In the trunk-stream drainage area,the average annual runoff presents a trend of gradual decrease from lower reaches to upper reaches,and the intra-annual surface runoff mostly concentrates in summer and autumn (June to October). The isotopic compositons of most water samples fall on the top right of the global precipitation line,δD = 8δ18O+10,showing that they have experienced intensive evaporation. With obvious region-continental effect and altitude effect,the distribution of water isotopic compositions is related to the movement of precipitation clouds from Bay of Bengal and Nujiang River and is affected by the topographic and climatic conditions of the Qinghai-Tibet Plateau.