Is it possible to use different data types and scales to reduce flow and transport uncertainty in natural heterogeneous formations? The experimental setup of the Settolo aquifer (Italy)

The uncertainty characterizing the description of hydraulic properties of aquifers, together with those implied in the process modeling and measurement errors, can be successfully dealt with by stochastic approaches, which allow the interpretation and the prediction of flow and transport processes in natural heterogeneous formations. The practical application of these approaches still encounters many difficulties, mainly due to the need for a detailed hydrogeological characterization of the site and to the unsuitability of the models, sometimes related to simplistic schematizations when describing in random terms the aquifer and its processes. The need to describe the spatial joint probability distribution of the hydraulic properties at different scales demands a large amount of data, to be obtained by several in situ and laboratory measurements. Moreover, modeling of these processes is often limited by the hypotheses of statistical homogeneity of the flow field and ergodicity of the dispersive process. These approaches are not suitable for the cases of practical interest, where the finite domain is characterized by irregular shapes and the flow field can be highly non-homogeneous, due to the influence of the boundary conditions, the presence of localized pumpings or inflows, or the lack of spatial stationarity of the hydraulic conductivity. Such circumstances emerge clearly in the real case of Settolo, an alluvial phreatic aquifer in a piedmont area of Northeastern Italy, where the effects related to the variability of the geological structures crossed by paleo-riverbeds and characterized by different facies, to the interactions between watercourses and the aquifer, to the recharge linked to the precipitation, and to the correct interpretation of concentration measurements of solutes must be challenged for an effective protection and/or a sustainable exploitation of the water resources. For these reasons, a careful site characterization is in progress, with a number of different measurements and scales involved. A surface geophysical survey has been carried out to investigate the thickness of the aquifer; water levels in the Piave river are being monitored for a detailed characterization of the boundary conditions; a network of piezometric wells has been installed to monitor water table and for the development of incoming pumping tests; and the geophysical interpretation of tracer tests (ERT) and breakthrough curve measurements are being planned for a local scale characterization of transport. We present here the data recorded at Settolo in the first six months of monitoring activities and the preliminary modeling results. The ultimate objective of the research is to suggest an integrated approach developed by means of models operating at different scales to seek a solution to the overall problem of flow and transport in natural heterogeneous formations.