Assessment of Hydrogeological Heterogeneities in Qaleh Tol Aquifer, North East of Khuzestan, Using Deep Geoelectrical Surveys

Water extraction from groundwater resources has been increasing in recent decades. Qaleh Tol plain is one of the critical plains in Iran, located in Khuzestan province, that is necessary to determine the groundwater potential in the plain to meet the water needs of the region. Also, in spite of the regional decline in groundwater level in the plain in recent years, the drop of water level in some observation wells in special areas, is lower than other plain areas. Accordingly, it was necessary to carry out deep geoelectrical exploration in Qaleh Tol plain for the purpose of detection of buried formations under the alluvium and determining the hydrogeological heterogeneities of the plain. Therefore, a combination of hydrogeological and geoelectrical studies in Qaleh Tol plain was carried out. Vertical Electrical Sounding (VES) using Schlumberger array was carried out at 86 VES stations in six profiles. 1-D interpretation have been performed using IPI2WIN to determine the types and depths of subsurface layers and geoelectrical tomography of subsurface was done by RES2DINV. In order to provide an appropriate image of underground the electrical resistivity tomography maps (ERT) were prepared. In the tomography sections, the investigation depth over than 450 meters has been able to accurately determine the bedrock of Qaleh Tol plain. The results showed that the bedrock of Qaleh Tol plain are composed of limestone of Asmari Formation, conglomerate of Bakhtiari formation and shale of Pabdeh formation. The Asmari limestone strip shaped bedrock in deeper parts of the aquifer with high groundwater potential along the plain is the cause of hydrogeological heterogeneities in the Qaleh Tol plain, which has led to very different hydrogeological behaviors in neighborhood water wells.