Water Source Identification and Circulation Characteristics of Intermittent Karst Spring Based on Hydrochemistry and Stable Isotope—an Example from Southern China

An Intermittent karst spring is a particular type of groundwater discharge with periodic groundwater flow processes, but a systematic understanding of its hydrological cycle process is lacking. This study considers the Chaoshuidong Spring (CSD), an intermittent karst spring in China, as an example. Integrated water chemistry and isotope methods were used to identify the recharge sources, migration paths, and evolution processes of its groundwater hydrochemistry. According to the statistical analysis of the water chemistry and isotopic characteristics of multiple groundwater discharge points in the basin, the structure of the CSD karst water system consists of an upper aquifer system in the Shilongdong Formation dominated by dolomite and a lower aquifer system in the Tianheban Formation dominated by limestone. The base flow of the CSD exhibits the hydrochemical characteristics of the upper limestone aquifer system. In contrast, the groundwater after the rain and siphon period shows the mixed hydrochemical characteristics of the lower dolomite aquifer system. However, the stable hydrogen and oxygen isotopes during the siphon period demonstrate apparent hysteresis. This indicates that the CSD includes both a shallow circulation system dominated by fractured media, which is susceptible to human pollution owing to short circulation path and fast renewal speed, and a deep circulation groundwater system consisting of multiple types of aquifer media with a longer circulation path and lower renewal speed owing to groundwater regulation and storage. The results can provide beneficial guidance for the rational development and protection of the groundwater resources of karst geysers and the development of tourism.