Understanding of groundwater evolution through chemical and age dating information in the Yongding River alluvial fan in Beijing

Groundwater plays important roles in human community development and the urbanization process as results of global environmental change rapid population growth. A clear understanding vertical horizontal spatial distribution characteristics groundwater sediment is premise efficient resource management utilization alluvial plains. To explore evolution Yongding River (YDR) fan, a typical profile from Mentougou to Fengheying was chosen conduct an extensive hydrogeological investigation with multiple hydrochemical, isotopic, age dating analyses, which represents one most units YDR fan. The analysis show that (i) along profile, water’s chemistry type gradually changes HCO 3 -Ca·Mg -Na. contents coarse grain decrease while fine particles regularly increase. Also, similar trend found direction. (ii) annual renewable rate > 10% upper 2%–8% nearby Daxing, < 2% Fengheying. (iii) In proximal fan area, average flow velocity single double layer about 65 m yr −1 approximately 18.9 . From mid distal value hydraulic conductivity decreases 12.4 3.75 8.54 0.64 , respectively. (iv) 14 C indicate shallow deep ranges 5a 60a 4000a 12000a, increases depth direction northwest southeast Understanding hydrochemistry provides valuable reference for development, utilization, pollution prevention