Application of geophysical and geological analyses to identify the main karst conduit close to the Sarabegarm spring, west Iran

The Sarabegarm karstic spring is located near the NW plunge of the Danehkhoshk anticline in western Iran. The spring is the main source of drinking water in the region, therefore understanding the path and location of its main karst conduit is crucial to protecting it from the risk of contamination. Near the spring, karstic limestone was dissected by two main sets of tension joints with N20E and N30W direction. The Mise-A-La-Masse (MALM) investigation showed that the main direction of groundwater flow towards the spring was elongated about N25E, almost coinciding with the surface trace of the NE trending fractures. The 2D frequency-domain induced polarisation surveys indicated that the zones with low resistivity and chargeability values were located below the trace of two main fractures. Since the main conduit system of the spring was most likely developed in the crushed zones of these fractures, the area near them has the highest vulnerability and must be protected from any activity posing a risk of ontamination. Results of this study showed that the application of frequency domain electrical resistivity, in combination with the geological analysis, could be suitable in characterising the shallow main conduits, particularly in the vicinity of big karst springs.