A preliminary investigation on the climate-discharge relationship in the upper region of the Yarlung Zangbo River basin

River discharge is one of the key elements in the global water cycle; however, its observation and projection are still lacking in alpine regions. This study analyzed the annual and seasonal variability of the river discharge in the upper region of the Yarlung Zangbo River basin, investigated the climate-discharge relationship, and projected the annual trend in the next few decades (2021–2100) based on a distributed hydrological model (Soil and Water Assessment Tool, SWAT). Results show that river discharge did not show the same trend as precipitation at either annual or seasonal scale in the study area. It indicated that precipitation might not be the primary source of river discharge, and meltwater from snow, glacier, and frozen soil could account for a large percentage of river discharge. The projected river discharge would vary significantly among years with different changing rates under different climate change scenarios. Overall, this study contributes to investigate the unusual climate-discharge relationship which is different from that in the whole river basin. Moreover, to separately consider the parameters related to snow melt could significantly improve the simulation accuracy; however, it could be further improved by considering the freeze and thaw processes of soil and glacier which are not included in the SWAT model.