3D Hydraulic Modeling of a Complex Alluvial Aquifer for Groundwater Resource Management

Many cities take nearby alluvial aquifers as their main resource of water supply. Therefore the aquifers, especially shallow aquifers, are always under either the influence of extreme hydrological events, or the threat of pollutants that are generated by the intense urban developments. To ensure an efficient management of water supply regarding both quantity and quality aspect, it requires a good knowledge of the dynamics of the aquifer. Characterizing the exchanges that could exist with free surface flow in associated rivers is one of the key issues. The most efficient way to understand the behaviour of the aquifer is to implement a 3D physically-based hydrodynamic model that can represent all physical processes. However, this approach, in order to become an operational tool, requests a structured methodology for data integration and validation. In this paper, a 3D hydraulic model of the Var lower valley is set up with FEFLOW modeling system. All the important hydrological processes such as precipitation, evapotranspiration, river-aquifer exchanges are considered. Despite a very complex and partially known geological structure, the results for a simulation of 1266 days demonstrate that the model is able to provide an accurate diagnostic on various hydraulic structures that are affecting the aquifer and may induced management difficulties. The proposed approach answers the current management demand and can provide efficient support within the underground resource exploitation.