资源环境科技发展态势分析平台

Precipitation plays an important role in global water cycle, and the stable hydrogen and oxygen isotopes of precipitation provide useful information in hydrological processes. To evaluate the controlling factors on stable isotopes of precipitation in the northwesternmost Tibetan Plateau (NWTP), the spatial-temporal variation of delta O-18 and delta H-2 in precipitation was investigated based on 120 event-based precipitation samples collected from 3 stations (Jiangka, Shaman and Xihexiu) during 2011-2014 and 45 monthly average precipitation data of Hetian station (GNIP) and 23 individual precipitation events of Shiquanhe station during 2001. The values of delta O-18 and delta H-2 in precipitation are more positive in the summer (June to July) and negative in the winter (November to March). The seasonal d-excess pattern observed in the NWTP is remarkably different from that in adjacent regions. The local meteoric water line (LMWL) was calculated as delta H-2 = 8.22 delta O-18 + 12.41 (R-2 = 0.98, n = 194) based on the event-based samples. Temperature and altitude effects show significant influence on the precipitation delta O-18 in the study area. Sub-cloud evaporation and recycling moisture also are important controlling factors during the precipitation process. The sub-cloud evaporation decreased d-excess between 1.7% and 45.8%, and the d-excess decreased linearly with increasing sub-cloud evaporation at about 1.15 parts per thousand per 1% change of sub-cloud evaporation. The recycled moisture has an important influence on the precipitation on the Xihexiu, Shaman and Jiangka stations. The result of this study is helpful to the understanding of regional water cycling and optimal water resource management during water shortages.