Karstic and alluvial aquifers: a conceptual model for the plain – Prealps system (northeastern Italy)

A 3D geostructural model, extending north–south from the Valsugana Line to the southern border of the high plain, trough the pre-Alpine thrust, and east–west from the Adige valley to the Brenta valley, trough the Schio–Vicenza Line, has been constructed. A detailed reconstructions of the regional aquiclude (pre-Permian basement-Werfen formation) integrated with information on the position of the main karstic springs allowed the geometric definition of the karstic saturated zone. Plain groundwater hydrochemical data, suggests (i) a hydraulic connection between the carbonate units of the pre-Alpine plateau and the same formations buried under the plain and (ii) the important role of the faults to connect the carbonate aquifer to the alluvial porous system, cutting the entire thickness of the Tertiary unit. Such relation implies an effect of the pre-Alpine aquifer on pressure and flow contributions of the intensely exploited phreatic system of the Venetian plain.