Long-term Pumping Test and Ert to Visualize Hydrogeologic Barriers in Heterogeneous and Karstic Coastal Aquifers

In coastal areas, groundwater may represent the main resource for human needs. The over-exploitation of coastal aquifers could cause seawater intrusion that induces depletion both in quality and quantity of the water resource, with no negligible environmental impacts. Moreover, locally geological heterogeneities of the aquifer can affect the flow and transport processes. In such cases, an integrated hydro-geophysical approach could provide useful information to evaluate the response of the aquifer and to estimate changes in the main hydraulic parameters such as transmissivity and permeability. In this study Electrical Resistivity Tomography (ERT) survey combined with traditional techniques of measuring the main groundwater parameters have been performed to assess the hydrogeological properties of a coastal heterogeneous aquifer. The conventional interpretation of pumping test drawdown allowed to detect a hydraulic barrier located to a specific distance with respect to the pumping well; furthermore, the transmissivity of the portion of aquifer involved in the pumping and the corresponding changes of its hydraulic conductivity due to the presence of the barrier has been estimated. Confirming the conventional interpretation of the pumping test drawdowns, the ERT image was able to locate the hydraulic barrier over space, visualizing a high resistive body, located below the water table.