A multidisciplinary approach for groundwater modeling: a case study in the Mantova province of the Northern Po Plain (Italy)

The work aims to develop a large-scale numerical hydrogeological model to support the groundwater management of the multilayered aquifer of Mantova province. The hydrogeological setting of this sector of Po Plain was reconstructed through a multidisciplinary approach, starting from stratigraphic, hydrochemical and hydraulic punctual data and arriving at an experimentally supported numerical model. Primarily, stratigraphic data allowed the reconstruction of subsurface bodies realizing a 2D sections grid, the base for the subsequent 3D geological model. This reconstruction revealed a high heterogeneity of aquifer and aquitard bodies along both horizontal and vertical directions, due to their sedimentary geological origins. Hydraulic tests confirmed a high permeability for gravels-sands strata, and a low permeability for silts-clays strata, giving to the aquifer a multilayer character with varying relationships between the different bodies, as the hydrochemical analysis also confirms. Thanks to the multidisciplinary approach, the resulting model permitted to outline the hydraulic interconnections between the multilayer aquifer and the surface water bodies, over all Garda Lake located on the northern boundary of the study area. The model domain was discretized using an unstructured grid to reproduce the geometries of the geological bodies. The resulting numerical grid, at model scale, consists of about 650000 3D Voronoi's cells with varying sizes, and 11 layers. The flow process has been implemented in the Modflow-USG framework. Using PEST with pilot points, the numerical model was set up and validated in transient condition considering hydraulic head data observed at monitoring points.