渭河源区水汽来源及地表径流组成的稳定同位素研究

Precipitation is a primary input source for the water cycle process, and plays an important role in terrestrial water cycle. Under natural conditions, as the total recharge source of terrestrial ecosystem, precipitation originating from moisture regions and its transportation is directly related to terrestrial water resource. Spatial and temporal variations in stable hydrogen and oxygen isotopes in precipitation and surface water not only can provide important clues to the origins of moisture and the climatic conditions under which it formed and contribution of precipitation to runoff, but also is the main research content and frontier in hydrological science. In the project, we combined the spatial and temporal variations of δD, δ18O, δ17O, 17O-excess and d-excess in precipitation and surface water, the NECP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) re-analysis data, meteorological and hydrological data, air mass trajectory model and endmember mixing model, our goal was to determine the origins of moisture and the climatic conditions under which it formed in the headwaters of the Weihe River basin and the contribution of precipitation to surface runoff of the Weihe River basin during different hydrological year. Based on hydrological and water cycle study frontier and more isotopic parameter such as 17O-excess, this project has two main aims: one is to study the spatial, seasonal and annual variations of origins of moisture and its controlling factors of the Weihe River basin, as well as meteorological condition at their moisture source regions. The other is to reveal the spatial, seasonal and annual variations of contributions of precipitation to surface water. Our ultimate aim is reveal the responsive mechanism between the precipitation/moisture source and surface runoff in the headwaters of the Weihe River basin, and illustrate the main role of moisture origin in water cycle processes and water resource formation in the Weihe River basin.

降水是水循环中重要的输入因子，在陆地水循环中起着极为重要的作用。天然情况下由水汽源地气团输送的大气降水为陆地水资源的总补给源。降水和地表水中稳定氢、氧同位素指标的时空变化特征对探讨大气降水的水汽来源、水起源地的气候条件及降水对河川径流的贡献具有重要意义，也是水文学研究的重要内容和研究前沿。本项目拟基于渭河源区(渭源、黄土高原及秦岭山地)降水和地表水的氢、氧同位素组成(δD、δ18O和δ17O)、过量17O(17O-excess)及过量氘(d-excess)的时空变化特征，结合气象、水文资料、NECP/NCAR再分析资料、气团轨迹模型及端元混合模型，研究渭河源区大气水汽来源、水起源地的气候条件及降水对河川径流的贡献时段与贡献率。本项目立足于全球瞩目的水文学研究的前沿流域，旨在认识渭河源区地表径流与降水和水汽来源的响应机理，揭示渭河源区水汽来源在流域水循环过程和水资源形成中的重要作用。

降水是水循环中重要的输入因子，在陆地水循环中起着极为重要的作用。降水和地表水中稳定氢、氧同位素指标的时空变化特征对探讨大气降水的水汽来源、水汽源地的气候条件及降水对河川径流的贡献具有重要意义，也是水文学研究的重要内容和研究前沿。本项目基于渭河源区(渭源、黄土高原及秦岭山地)降水和地表水的氢、氧同位素组成(δD、δ18O)和过量氘(d-excess)的时空变化特征，结合气象、水文资料、NECP/NCAR再分析资料、气团轨迹模型及端元混合模型，研究渭河源区大气水汽来源、水汽源地的气候条件及降水对河川径流的贡献时段与贡献率。结果表明：(1) 就水汽来源而言，渭河源区的水汽来源如黄土高原、关中盆地和秦岭北麓降水中δD、δ18O和d-excess既有显著的空间变化特征，也有明显的季节变化特征，反映了渭河源区形成降水的水汽来源的复杂性，既有大气环流的影响，也有区域内循环的影响。同时在空间上看，渭河源区降水的δD、δ18O既有显著的海拔效应，也有显著的经度效应，其形成机理有待于将来用更为详实的数据进行进一步分析。(2) 就降水对地表径流的贡献而言，渭河发源地的渭源和黄土高原区，地表水的δD、δ18O和d-excess对降水δD、δ18O和d-excess的变化的响应较秦岭北麓弱，说明除黄土高原人类活动影响外，秦岭北麓降水对地表水的贡献大于黄土高原。本项目将获取的关键数据包括7个站的降水、地表水δD、δ18O数据和4个站的降水δD、δ18O数据。基于本项目获取的关键数据，本项目将在揭示渭河源区大尺度的水汽输送和不同下垫面降水对当地水资源形成的影响方面取得结论性的研究成果。

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