Characteristics of δ~(18)O and δ~2H and their implication for the interaction between precipitation, groundwater and river water in the upper River Tuojiang, Southwest China

摘要

The Tuojiang River has multiple water sources and serious pollution problems, but its hydrological mechanismin the upper reaches is still unclear. To better understand the hydrological characteristics of the TuojiangRiver, the isotopic compositions of its precipitation, river water and groundwater in the upper reaches havebeen investigated from May 2018 to April 2019. The results indicated that the isotope values of precipitation,river water and groundwater fluctuate significantly throughout the year with depleted value in the wet seasonand enriched value in the dry season. Spatially, the isotope values of river water increase gradually from upstreamto downstream. River water is the main source of recharge to groundwater and precipitation is the minor one. Theisotope-based hydrograph separation shows that the Mianyuan River and Pihe River contribute more greatly toTuojiang River than the Shiting River and Yazi River. The mean residence time of river water from the TuojiangRiver varies from 0.95 to 1.49 years, which indicates that rivers in the upper reaches of the Tuojiang River respondto precipitation quickly. This study proved the usefulness of stable isotopes to identify the different water cyclecomponents and reflect the pollution problem in multiple water source confluence areas.