Présentations Colloques

Remote sensing and hydrogeophysical methods supported by field observation, were applied in the Sardon (Spain) experimental hard rock catchment (80km2) to define its conceptual model, further used to develop integrated hydrological model of that area. In line with a general conceptual model of hard rock aquifers, we identified two main hydrostratigraphic layers- a saprolite layer and a fissured layer. Both layers were intersected and drained by fault zones that control the hydrogeology of the catchment. The spatial discontinuities of the saprolite layer were well defined by RS techniques while subsurface geometry and aquifer parameters by hydrogeophysics. The processing of high-resolution satellite images and digital terrain model allowed mapping efficiently the main fault zones and the horizontal distribution of the hydrostratigraphic layers. The GPR method was able to detect shallow water table although the quantitative assessment of the water table depth could not be made routinely because it required local calibration based on measurements made in piezometers and soils and was restricted to the locations with water table depth <3 m b.g.s. The ERT method allowed to confirm local subsurface hydrostratigraphy and provided input for the MRS inversion. The multi-frequency FDEM method combined with the laterally constrained inversion technique showed to be very efficient, providing long cross-sections depicting large hydrogeological structures coherent with direct field observation, geological mapping and drilling. The MRS provided valuable results in the saprolite layer, but only in the locations with sufficient signal to noise ratio. The proposed multi-technique method of hydrogeological characterization of complex hard rock catchments, involving non-invasive, so cost effective techniques such as remote sensing and hydrogeophysics, turned to be highly suitable for development of hydrogeological conceptual models in hard rock environments.