Distinguishing Groundwater Flow Paths in Fractured Rock Aquifers Formed Under Tectonic Stress Using Geophysical Techniques: Cankurtaran Basin, Denizli, Turkey

Abstract

Gokpinar spring is one of the most important drinking water resources of Denizli city (Turkey), covering more than one third of the water need of the municipality. In this paper, we present a combination of geophysical methods in order to define the groundwater flow paths in Gokpinar spring region. The spring of Gokpinar is a result of the Fault-fracture network formed during the tectonic events which took place in the study area. This fault and fracture system present in the Gokpinar spring zone are characterized by the Cankurtaran fault in the east and Babadag fault in the south. To highlight the main directions of the groundwater flows feeding Gokpinar spring, an electrical resistivity tomography (ERT) survey was carried out in the study area. The results obtained from this survey have been confirmed by a frequency domain electromagnetic (FEM) survey carried out along four profiles in addition to four ground penetrating radar profiles (GPR) profiles. The comparison of the two auxiliary methods with the ERT profiles allowed a better understanding of the groundwater movements. The ERT data was collected along six profiles corresponding to Wenner–Schlumberger array and located predominantly in the southern and eastern parts of the spring surrounding area. In order to confirm the hypothesis from the interpretation of the ERT profiles, two simplified different scenarios were numerically and experimentally considered. The results of the combined methods have ultimately led to define the main direction of groundwater flows feeding the Gokpinar spring, which is related to four factors: The Fault-Fracture network, karstic features, the topography, and deep groundwater.