Application of self-potential and high-density resistivity method to the water exploration in karst terrain of middle-lower reaches of Xijiang River

Based on hydrodynamic conditions of the shallow karst groundwater seepage, we mainly study the natural polarization phenomenon of geological structures in water-enriched karst induced by the action of groundwater seepage and distribution characteristics of the natural electric field therefrom. By comprehensive prospecting with the combination of self-potential method and high-density electronic resistivity method, we analyse and evaluate the application effect of the combination on the exploration of karst groundwater in different hydrogeological environments of middle and lower reaches of Xijiang River. In this study, we also integrate geophysical prospecting results with the data derived from exploration & production wells in the survey project of hydrogeological environment initiated and supported by China Geological Survey. Study results show that induced electrical methods, such as transient electromagnetic method, audio magnetotelluric sounding method, ground nuclear magnetic resonance method, induced polarization method, sonic frequency geoelectric field method, VLF electromagnetic method, etc., are seriously affected by electromagnetic fields like power transmission and communication network. The high-density resistivity method shows a strong anti-interference ability and high signal-to-noise ratio. But its exploration depth is relatively shallow, and it is easily disturbed by ore bodies with high conductivity such as charry limestones or karst minerals. The self-potential method is used in the situation of polarization of geological structures in water-enriched karst caused by groundwater migration. Anomalies of the natural electric field are closely related to the groundwater recharge and migration. The complementation of self-potential method and high-density electronic resistivity method in groundwater exploration can contribute to the mutual corroboration of prospecting results, hence improving prospecting resolution and precision.