高寒干旱区降水氢氧稳定同位素组成及其水汽来源:以昆仑山北坡格尔木河流域为例

Stable hydrogen-oxygen isotope composition and atmospheric moisture sources of precipitation in an arid-alpine region:A case study of the Golmud River Watershed on the north slope of the Kunlun Mountains

降水来源是高寒干旱区水文循环研究中的重要内容。本研究以格尔木河流域山区段纳赤台水文站为研究点,收集2019年6—10月的51个降水事件样品,开展了降水氢氧(H-O)稳定同位素组成及其水汽来源研究。结果表明:(1)降水δ^(18)O与δ^(2)H值变化显著,气温是其变化的主控因素;(2)降水经历了多次蒸发-凝结过程,其同位素值大多落在全球降水线上方;(3)山区降水线方程为δ^(2)H=7.4×δ^(18)O+13.2,可视为流域降水线方程,为流域水循环研究提供可靠的参考。氘盈余分析揭示了西风环流及局地水汽循环是流域山区降水的主要贡献者。HYSPLIT模拟进一步表明流域山区高空水汽由西风环流携带而来而低空水汽还与内陆水体蒸发有关。该成果有助于深入理解高寒山区水汽循环理论,可为当地水资源管理决策提供科学依据。

The source of precipitation is an important content in the hydrologic study in arid-alpine regions.In this study,51 precipitation event samples were collected from June to October 2019 at Nachitai of the Golmud River watershed on the northern slope of the Kunlun Mountains,and the stable hydrogen-oxygen isotope composition and atmospheric moisture of precipitation were investigated.The results showed that theδ^(18)O andδ^(2)H values of precipitation varied greatly and were mainly controlled by air temperature;precipitation experienced multiple evaporation-condensation processes and its stable H-O isotope data mostly fell above the global meteoric water line;and the local meteoric water line wasδ^(2)H=7.4×δ^(18)O+13.2 for the mountainous region of the Golmud River watershed,and may characterize the whole watershed,which provides a good reference for studying the watershed-scale hydrological cycle.The analyses of deuterium excess values revealed that the westerly circulation and local moisture transport were the main contributors to mountainous precipitation in the Golmud River watershed.The HYSPLIT model simulation further showed that atmospheric moisture of high levels was carried by the westerly circulation and atmospheric moisture of low levels were recharged by the inland moisture cycle.The findings are helpful to deeply understand the water cycle in the arid-alpine areas and also may provide a scientific basis for local water resource management.