Groundwater plays a number of very important roles in our environment and in our economies. It supports rivers, lakes and wetlands. As such, groundwater resources must be preserved. To that end, numerical models are an essential tool for sustainable management. TK Consult AG has developed a modelling strategy consisting of (1) analysis of existing information, (2) conceptualization of the system`s behavior, (3) implementation of such concept into a numerical model, (4) model calibration and validation and (5) forecasting of anthropic actions over the aquifer. Such methodology has been successfully applied to a large number of projects all over the world.