Role of the Geologic Structures on the Aquifers Vulnerability in Arid Areas: Case Study from Swaqa - Ghabawi / Jordan

Abstract

In this study, the geological structures in the area extending between Ghabawi solid waste and Swaqa hazardous waste deposits were investigated in detail to study the impacts of human activities on the aquifer vulnerability. Two indices were used to evaluate that vulnerability, namely; DRASTIC and SINTACS. The hazardous waste disposal site of Swaqa in the southern part of the study area, the landfill deposit in its northern part and the intended oil shale and uranium mining are the main sources of potential groundwater pollution. The study aims at building a new approach to combine structures with known vulnerability indices to better evaluate the prevailing conditions. Chemical analyses of the groundwater quality in the area were performed to validate the findings. All relevant variables of the study area were put in a GIS environment as digits to ease layering of the different types of spatial data. The aquifers in the study area refer to the Lower Tertiary and Upper Cretaceous and are composed mainly of carbonate types of rocks. Three major structures are found in the area consisting of faults differently trending in directions. These faults were found to intersect the aquifers in the area. Without the consideration of the effects of the faults, the area would locate in middle vulnerability zones, but their presence caused an elevation in the vulnerability class. This was clear from the spatial distribution of the values of nitrates, which was found to correlate with the structural map of the area. DRASTIC and SINTACS vulnerability indices are unable alone to evaluate the spatial vulnerability of the aquifers when geologic structures are dominant. Accordingly, some modifications and merging were made to the DRASTIC and SINTACS indices to account for the structures in order to make thse indices suitable to evaluate similar areas with prevailing geologic structures, especially faults and fissures.