Mapping aquifer geometry using electrical resistivity tomography: a case study from Sanliurfa, south-eastern Turkey

A shallow aquifer system was investigated with 2D electrical resistivity tomography (ERT) to determine the hydrogeological setting of the Balikli Lake region, Sanliurfa, Turkey. Many spring waters are found in the study area where groundwater flow paths merge and reach the surface. A recreation complex was planned near the Balikli Lake by the Municipality of Sanliurfa. Therefore, an ERT survey was carried out to reveal the subsurface characterization, particularly to investigate the possible shallow aquifer system beneath the recreation area. Consequently, 2D resistivity data along thirteen profiles were acquired in the study area and the data were inverted by a tomographic inversion technique. The conductive layers in the ERT results indicated a shallow aquifer zone probably related to a karstic environment. The high conductivity observed in this layer might be caused by pollution resulting from the industrial and domestic wastes of the residential areas. The high resistive bottom layer was considered to be the basement in the study area. The geometry of the shallow aquifer environment was confirmed by slicing maps obtained from the ERT data. To build the conceptual geological model, a 2D forward resistivity modelling study was also achieved after the inversion studies. The inversion parameters and borehole result underlie the background of the forward model. Field and synthetic data were compared to each other and tested in means of calculation of the misfits to determine the reliability of these models.