Tracing potential water sources of the Nagqu River using stable isotopes

•The variations were elaborated among three types of water sources in streamflow.•The stable isotope method and HYSPLIT model were used to trace the vapor sources.•Groundwater and snowmelt contribute about 39.8 % and 32.2 % to the Nagqu River, respectively.•The groundwater age in the northern part is older than the southern part.