Open questions about the hydrodynamic behaviour of the deep, coastal aquifer of the Salento peninsula (south-eastern Italy): Coupling expert knowledge, data, and numerical modelling for testing hydrogeological conceptual models

This paper investigates the role of numerical models for testing the suitability of Hydrogeological Conceptual Models (HCMs). This approach has been applied to model the hydrodynamics of the deep, karst aquifer of the Adriatic portion of the Salento peninsula (south-eastern Italy), focusing on a coastal sub-area between Lecce and Otranto. The scope was to test two HCMs for the explanation of anomalous piezometric levels close to the coast ( from 4.0 m to 4.5 m above mean sea level) occurring in this sub-area. Two different hypothesis were tested, assuming that the hydraulic contact between the aquifer and the sea in this sub-area occurs (a) offshore (HCM-A), or (b) at the shoreline (HCM-B). In HCIVI-B, we assumed a hydraulic connection between the deep aquifer and the Pliocene superficial aquifer. Results show that both HCMs can explain the anomalous piezometric values recorded close to the coast, but HCM-B would not completely clarify such occurrence. Calibration results for HCM-B, indeed, show two points located north of Otranto where the simulated hydraulic head is underestimated by the model and shows a poor sensitivity to any model parameter. As such, this is probably due to local phenomena not considered in the modelling framework and requiring further investigations. (C) 2020 Elsevier B.V. All rights reserved.