A detailed 3D geological model was generated on the basis of borehole and Airborne EM data. In total 20 buried valleys structures was delineated with high detail due to the areal coverage with airborne geophysical methods. The study illustrates the need for a groundwater model covering a regional area, in areas that contains buried valleys subject to large groundwater abstractions. Because aquifer responses transmit quickly through the valley systems, the outer model boundary conditions must be placed carefully and at large distances. Using MODFLOW-USG makes it straightforward to update the regional model by embedding local detailed models. The regional model can thereby be used as basis for multiple local scale studies.