Heihe River,one of the greatest inland rivers in China,is confronted with shortage of water resources due to unreasonable development and utilization.To utilize effectively the limited water resources,isotope techniques are widely used to study water cycle.Oxygen and hydrogen isotopes in precipitation are discussed based on the study of some precipitation samples in the middle basin and the mountain areas of Heihe River.Some conclusions are drawn as follows: The averaged δD and δ18O compositions have a rela...