A multidisciplinary approach to determine the structural geometry of hard-rock aquifers. Application to the Plancoet migmatitic aquifer (NE Brittany, W France)

A new multidisciplinary methodology is developed to determine the structural geometry of hard-rock aquifers. The Plancoet migmatitic basement, chosen as an example for the use of this methodology, is studied both at a regional (300 km(2)) and a local (4 km(2)) scale. The regional mapping, based on field mapping of the tectonic structures and the weathered layers, on geostatistics and on aerial photographs and Digital Elevation Model (DEM) analyses, demonstrates the influence of the tectonic structures on the weathering processes. Some geo-electric investigations, added to the first mapping at the local scale, lead to the building of a local geometrical model of the aquifer.