Combined GPR and surface magnetic resonance investigation for aquifer characterisation

Ground-penetrating radar (GPR) and magnetic resonance tomography (MRT) are used for aquifer architecture mapping and characterisation. We combine both techniques on a hydrogeophysical test site with glacigenic and periglacial deposits that show distinct lateral variability. A pseudo 3D GPR investigation provides the architecture on a large area and, e.g., the topography of a till layer, which acts as an aquitard. We use this structural information as constraint for the 2D MRT data inversion to overcome the limited spatial resolution of the method. Inversion results show that the imaging of water content and relaxation time, which is related to pore-size distribution, is improved using a mesh including the GPR reflections and by applying a sharp boundary constraint at the GPR reflectors. Some anomalies remain in the inverted relaxation times that are probably caused by 3D effects of the till topography as mapped by GPR.