基于氢氧稳定同位素技术的青藏高原典型小流域水分交换

Water exchange of typical small watershed in Qinghai⁃Tibet Plateau based on hydrogen and oxygen isotopes tracing

青藏高原水分循环研究是一个受到广泛关注的热点问题,但流域尺度内水分运移的研究相对薄弱。本文基于氢氧稳定同位素技术(δ^(2)H和δ^(18)O)研究了青海海北高寒草地生态系统国家野外科学观测研究站(海北站)的典型流域内的降水、浅层地下水、中层地下水、沼泽水、泉水、河水、湖水和土壤水的时空变异,利用MixSIAR模型定量分析各水体的水分来源与交换。结果表明:海北站小流域不同水源氢氧稳定同位素特征存在显著差异,湖水和降水同位素值变幅大于其他水体,湖水同位素富集程度高于其他水体;浅层地下水(3 m)是小流域水源涵养发挥的重要调节库,泉水是浅层地下水的地表表现形式;土壤水是小流域重要的水源涵养体,是大气降水-浅层地下水(3 m)-中层地下水(20 m)垂向交换的过渡,土壤水、浅层地下水通过横向径流向河流、沼泽进行水分补充。本研究可为高寒小流域水文模型的优化和水资源利用提供依据。

Water cycling in Qinghai-Tibet Plateau is a hot topic.However,the research on water transport at the watershed scale is relatively weak.In this study,stable isotopes of hydrogen and oxygen(δ^(2)H andδ^(18)O)were used to determine the temporal and spatial variation of precipitation,shallow groundwater,middle-layer groundwater,marsh water,spring water,creek water,lake water and soil water in a typical watershed of Haibei National Field Scientific Observation and Research Station(Haibei Station)in Qinghai Province.The MixSIAR model was used to quantitatively analyze water source of each water body and their exchange.The results showed that there were significant differences in the characteristics of hydrogen and oxygen stable isotopes of different water sources.The variations of isotope values in lake water and precipitation were greater than that of other waters,and the isotope enrichment in lake water was higher than that of other water bodies.Shallow groundwater(3 m)was an important regulating reservoir for water conservation in small watershed,while spring water was the surface manifestation of shallow groundwater.Soil water was important in water conservation of small watershed,as well as the transition in vertical exchange of precipitation-shallow groundwater(3 m)-middle groundwater(20 m).Soil water and shallow groundwater replenished water to creeks and marshes through lateral runoff.This study provides a basis for the optimization of hydrological model and the utilization of water resources in small alpine watersheds.