Temporal and spatial variations of δ18O in precipitation of the Yarlung Zangbo River Basin

This paper reveals the temporal and spatial variations of stable isotope in precipitation of the Yarlung Zangbo River Basin based on the variations of delta O-18 in precipitation at four stations (Lhaze, Nugesha, Yangcun and Nuxia) in 2005. The results show that delta O-18 of precipitation has distinct seasonal changes in the Yarlung Zangbo River Basin. The higher value of delta O-18 occurs in spring prior to monsoon precipitation, and the lower value occurs during monsoon precipitation. From the spatial variations, with the altitude-effect and rainout process during moisture transport along the Yarlung Zangbo River Valley, O-18 of precipitation is gradually depleted. Thus, delta O-18 of precipitation decreases gradually from the downstream to the upstream, and the lapse rate of delta O-18 in precipitation is approximately 0.34 parts per thousand/100m and 0.7 parts per thousand/100km for the two reasons. During monsoon precipitation, spatial variation of delta O-18 in precipitation is dominated by the amount effect in the large scale synoptic condition.