Mapping regional and nested flow systems in the karst aquifers of Jinan spring using hydrochemical and isotope data

This study enhances the understanding of the evolution of water transport in karst water flow systems. This paper explores the karst water flow system from a hydrogeochemical perspective. It has been discovered that in the recharge area, the hydrochemical effect of karst water is primarily influenced by dissolution and filtration. In the fault zone and concentrated discharge area, it is primarily influenced by mixing. In the geothermal area, the dominant factors are dissolution, precipitation, and dolomitization. From the southern to the northern area, the hydrochemical type of karst water gradually changes from HCO3-Ca type to SO4·Cl-Ca·Na type. Atmospheric precipitation is the primary recharge source of karst water, with a recharge elevation range of 181–1,495 m. According to geological drilling statistics, the groundwater transport depth transits from the shallow transport in the south to the deep transport in the north, with a depth range of 3,000–3,500 m, and using isotope data to obtain the groundwater retention time range is 6–27,000 years. The groundwater transport mode is divided into three levels: open-shallow transport karst cold water phreatic flow, semi-open-medium-deep transport karst cold water confined flow, and weak open-deep transport geothermal water confined water flow.