In Denmark the water supply is entirely based on ground water. In some parts of the country these resources are found in buried quaternary tunnel valleys. Intensive mapping has shown that the valleys typically have a complex internal hydrogeology with multiple cut and fill structures. The administration of groundwater resources has been based on simulations using regional scale groundwater models. However, regional scale models have difficulties with accurately resolving the complex geology of the buried valleys, which bears the risk of poor model predictions of local scale effects of groundwater abstraction. To enable effective administration of the groundwater resources new methods need to be investigated to improve simulation of local scale flow in buried valleys that interact with surrounding regional groundwater systems. The purpose of this synthetic case study is to test the Local Grid Refinement (LGR) method developed for MODFLOW-2005 for simulation of groundwater flow in areas containing buried valleys. The tests are conducted as comparative analysis between simulations made with a globally refined model, a locally refined model, and a globally coarse model, respectively. Based on the results we will evaluate how to use the method to refine a regional scale model covering an area north of the town of Aarhus, Denmark. The area, which contains several buried valleys, is marked with a red square on the map.