Contamination of groundwater with pesticides and nitrate has compelled the Danish Government to launch a major hydrogeological mapping programme covering about 40% of the land area of Denmark. Numerous geophysical surveys are currently being carried out in order to acquire the necessary data. These new data are crucial for the 3-D geological models that are used in the planning of future water supply and landuse. Normally, site-specific groundwater protection zones (Thomsen et al. 2004) are based on groundwatermodelled catchment areas for each well, but proper 3-D geological models are needed in order to create a valid basis for the groundwater models. Since most of the Danish nearsurface geology is complex, a full geological understanding is required combined with in-depth interpretation of geological and geophysical data.