A mathematical model has been developed to simulate groundwater flow in the Quaternary aquifer system east of De Haan (Belgium). The estimated lateral variations of the hydraulic parameters have repeatedly been adjusted by comparing the calculated hydraulic-head configuration to the observed one. After this calibration of the model was achieved, the influence of groundwater extraction has been examined. Even at pumping rates as low as 250.000 m³/year, artificial replenishment of the aquifer system will be necessary in order to avoid flow of salt water towards the wells
