State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering Hohai University Nanjing 210098 China;
Institute of Isotope Hydrology Research Hohai University Nanjing 210098 China;
Institute of Geology and Geophysics Chinese Academy of Science Beijing 100018 China;
isotope; CFC; Ejin Basin; Gurinai; groundwater recharge; precipitation; Qilian Mountain;