Preliminary Research on Hydrogen and Oxygen Isotope Characteristics of River Waters in the Source Region of the Yangtze River and the Lancang River

By surveying and evaluating the δD and δ18O values of the water in the source region of the Yangtze River and the Lancang River, the characteristics of the hydrogen and oxygen stable isotope composition have been analyzed. The results showed that the ranges of δD and δ18O values varied from −126.28‰ to −47.96‰ and −16.77‰ to −7.13‰. The standard deviation of δD and δ18O value are 18.58‰ and 2.34‰. The stability of δ18O value is better than δD. Atmospheric precipitation is the principal source of river water supply in the region. The Local Meteoric Water Line equation is δD = 7.73 δ18O + 4.81 (R2 = 0.96, n = 19). Due to strong evapotranspiration, its slope and intercept are smaller than the Global Meteoric Water Line. The strong evapotranspiration in the source regions causes most of the d-excess to be negative, and the ice-snow melt water replenishment feature causes some d-excess to be positive. δD and δ18O values in the source regions exhibited certain latitude effect and continental effect.