Investigation of discharge-area groundwaters for recharge source characterization on different scales: the case of Jinan in northern China

Abstract

Discharge-area groundwater in Jinan, a typical karst region in northern China, was investigated by studying both the hydrological and chemical processes evolving from the recharge in mountainous terrains to the karst-spring outflows in the metropolitan area. Large-scale exploitation of karst groundwater has led to a disturbing trend in the ever-decreasing spring outflow rates and groundwater level. There is insufficient information about the Jinan karst aquifers, which provide the main water sources to meet human demand and to sustain spring outflow. The coupling of hydrological and chemical processes quantifies the flow system through aqueous chemistry characterization of the water sources. This approach is used to study the groundwater flow discharges in different locations and geological settings. The potentiometric data indicated limited vertical connectivity between distinct hydrogeological units and alteration of the recharge regime by the faults and by artificial exploitation. Shallow groundwater primarily belongs to the local flow system, with high nitrate concentration and enriched stable isotopic contents. Thermal groundwater has high concentrations of chloride and total dissolved solids, derived from a regional flow system with the highest recharge altitudes and long residence time. Non-thermal karst water may be attributed to the intermediate flow system, with uniform HCO3–Ca(Mg) facies and low nitrate concentration. This work highlighted discharge as a fingerprint of groundwater flow conditions and provides a better insight into the hydrogeological system.