Anomalous spontaneous electrical potential characteristics of epi-karst in the Longrui Depression, Southern Guangxi Province, China

Abstract

This paper examines the use of the temporal and spatial distribution of natural electric fields in karst depressions to detect shallow groundwater resources. Under specific osmotic pressures, vadose water is filtered through the soil layer, and supplies deep karst water through pipes or underground rivers along the carbonate dissolution fracture network. As a result, a natural electric field is generated by ions at the interface between conductive soil and rock layers. Detecting this natural electric field can be used as a research method for shallow karst water exploration. This method has been applied to a karst depression in Longrui, China, and the results show that an anomalous zone with electric potential values of − 60 mV to − 80 mV occurs in the center of the depression. The anomalous zone has an S-shaped, north-to-south distribution, with a width of about 40 m. Changes in the plane of the anomalous zone indicate differences in shallow karst development in depressions, and hydrogeological drilling reveals shallow caves, sags and fault zones that correspond with the natural potential anomalies at different depths in the Longrui Depression. Additionally, advancement of boreholes reveals a water yield of 60 m3/h. This highlights the effectiveness of using the natural electric field method to detect karst water in epi-karst areas.