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A rapid groundwater circulation system inferred from temporal water dynamics and isotopes in a typical alluvial-fluvial fan of the Nalenggele River in arid Qaidam Basin, China
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  • Hongbing Tan,
  • Yu Zhang,
  • Wenbo Rao,
  • Wanquan Ta,
  • Hongye Guo,
  • Shicheng Lu,
  • Peixing Cong
Hongbing Tan
Hohai University

Corresponding Author:tan815@sina.com

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Yu Zhang
School of Earth Sciences and Engineering, Hohai University
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Wenbo Rao
Institute of Isotope Hydrology, College of Earth Sciences and Engineering, Hohai University
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Wanquan Ta
Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Sciences
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Hongye Guo
Qinghai Province Hydrogeology and Engineering Geology Environmental Institute of Geological Survey
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Shicheng Lu
Hohai University
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Peixing Cong
Hohai University
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Abstract

A rapid groundwater recharge and circulation system has developed in Qaidam Basin, China. Stable H and O isotopes were monthly sampled in both river water and groundwater, and water table fluctuations were monitored over a complete seasonal cycle from dry-season to wet-season conditions in the Nalenggele River catchment in Qaidam Basin. The main goals are to demonstrate and explain rapid circulation in the groundwater system. A distinct seasonal fluctuation of the water table with associated stable isotopic variations can be observed in the alluvial-fluvial fan of the Nalenggele River catchment. During the wet season, replenishment of the aquifer results in a rising water table rises. The recharge mechanism appears to be related to the coincidence of several favorable hydrological conditions: an abundant recharge water source from summer precipitation and glacial-snow melt in the high Kunlun mountains, large-scale active faults, a volcanic crater and other macro-structures that act as favorable recharge conduits, the large hydraulic head from recharge areas to the alluvial-fluvial fan, and the presence of over 100 m of unconsolidated sand and gravel acting as the main aquifer. Warming climate is expected to increase precipitation and to accelerate melting of glaciers in the Kunlun Mountains, increasing recharge and leading to rapid rise in the water table in the alluvial-fluvial fan. Increased recharge in the future will provide water of improved quality to the Qaidam Basin, and will allow management of land in ways that reduce soil salinity and alkalinity.