Abstract: Hydrogen and oxygen isotopic composition of precipitation affected by a variety of factors, such as temperature, precipitation amount, altitude, vapor source and others, is the important tool for investigating the regional hydrologic cycle. The variations of δD and δ¹⁸O values in every rain and snow samples at three stations along the Pailugou catchment from November 2012 to December 2013 were presented in this syudy. The hydrogen and oxygen isotopes in individual precipitation events exhibited extensive variation. The δ¹⁸O varied from +32.32‰ to +3.23‰, while the δD values ranged from -254.46‰ to +12.11‰. Results showed that the δ¹⁸O displayed a distinct seasonal variation, with enriched values occurred in summer and relatively depleted in winter. There was a statistically significant positive correlation between the δ¹⁸O and δD values and local surface air temperature at all the three stations, which was valuable for regional quantitative temperature reconstruction. The Local Meteoric Water Llines (LMWLs) for three stations had similar intercepts and slopes, which reflected the regional climate feature. The nearest Global Network of Isotopes in Precipitation (GNIP) station (Zhangye), compared to the LMWLs for the Pailugou catchment, showed the obvious recycled moisture and secondary evaporation effects with lower intercept and slope. Additionally, the d-excess parameter in precipitation exhibited an anti-phase seasonal variability with the δ¹⁸O. The 96-hr back trajectories for each precipitation event using the HYSPLIT model indicated a dominant effect of westerly air masses in summer and the integrated influence of westerly and polar air masses in winter.

Key words: Pailugou catchment, precipitation, oxygen and hydrogen isotopes, meteoric water line, moisture source