Hidrogeological implications of Beja fault location using geoelectrical methods

Due to widely spread nitrate pollution that reaches the groundwater supply in the Beja area, deeper aquifer zones that may be considered as an alternative to the present situation must be identified. A deep unpolluted aquifer below the unaltered rock was detected using several surface geoelectrical methods: a dipole-dipole survey was therefore conducted, which made it possible to detect the main fracturing zones to a depth of about 600 metres, as well as deep alteration zones corresponding to possible groundwater circulation. More precise studies were then carried out in areas of interest detected during the above-mentioned survey, namely a Rectangular Survey and three Vertical Electrical Soundings (VES). Data interpretation has revealed a good adjustment with local geology and has allowed the determination of the approximate geometry and type of geological formations at these depths. It has also indicated the existence of two zones with potential groundwater circulation: one shallower and more vulnerable to the pollution; and a deeper aquifer, associated with the Beja Fault, less vulnerable to pollution.