3D modeling of a complex alluvial aquifer for efficient management – application to the lower valley of Var river, France

Complex alluvial aquifers are frequently essential resources for cities that are looking for reliable and safe resources for water supply. The location of such aquifers is frequently combined with intense urban developments that may, potentially, generate pollutants that could affect badly the quality of the resources. An efficient and safe management of water supply system requests to develop a good knowledge of the dynamics of the aquifer and to characterize the exchanges that could exist with free surface flows in associated rivers. The most efficient way to understand the behaviour of the aquifer is to implement a 3D physically-based hydrodynamic model that could represent all physical processes. However, this approach, in order to become an operational tool, requests a structured methodology for data integration and validation. The paper describes the construction of a 3D hydraulic model of groundwater flow in the Var lower valley, on the French Riviera, with FEFLOW modeling system. Despite a very complex geological structure and a limited knowledge on the aquifer itself, the results demonstrate that the model is able to represent the groundwater flows over long chronologies and to provide an accurate diagnostic on various hydraulic structures that are affecting negatively the aquifer conservation.