Investigation of karst hydrogeological conditions and connectivity tests at a tailings pond in Guangxi

Investigating whether there is a hydraulic connection between underground karst systems can be effectively achieved through groundwater connectivity tests. Taking a tailings pond in Guangxi as an example, by understanding the hydrogeological conditions of the study area, the characteristics of the aquifers, and the recharge, flow, and discharge patterns of groundwater are identified. Through flow monitoring of the Shanhu River, it is determined that the surface water of the Shanhu River primarily originates from groundwater recharge, accounting for approximately 63.3% of the river’s recharge in this section. The Shanhu River serves as the discharge boundary for the secondary hydrogeological unit of Shanmuchong. Further field connectivity tests revealed no karst conduit connections between the boreholes and the karst spring in Xinmin Village, the Shanhu River, or the ponds, validating the conclusion in the original tailings pond survey report that the lower karst filling rate is 97.4%. The visual detection limit of the colorimetric analysis method is 0.097 6 mg/L, while the detection limit using the fluorescent lamp irradiation method is 0.024 4 mg/L, which are 19.52 times and 4.88 times different from the spectrophotometric method, respectively. The difference is not significant, and the colorimetric analysis method using visual inspection and fluorescent lamp irradiation can basically meet the requirements for simple field monitoring. It is easy to use and particularly suitable for temporary local monitors entrusted with the task.