Numerical simulation of groundwater age distributions in the hierarchical subsurface flow system: a case study of Jinan in northern China

Understanding groundwater age is essential for the aquifer management. In this study, a typical hydrogeological cross section in Jinan is selected to set up a coupled groundwater flow and age transport model. The simulation results show that hierarchical groundwater flow systems, composed by the nested local, intermediate and regional subsystems, are developed from the northern piedmont of Mount Taishan to Qiguang Fault. The scales of these flow subsystems are primarily controlled by the topography. Aquifer lithology variations also influence the groundwater flow system. Groundwater age distributions are closely related to the flow system. Groundwater age becomes older along the flow paths and increases abruptly near the internal stagnation point, which can be used as a characteristic boundary between different groundwater flow hierarchies. The results of the present research will not only help understand the groundwater circulation regimes in Jinan, promote the rational development and utilization of groundwater resources, but also provide references for the practical applications of groundwater flow system theory.