Integrating Multi-scale Geophysical Data for the 3D Characterization of an Alluvial Aquifer

Understanding groundwater flow and contaminant transport within alluvial aquifers requires the detection and detailed characterization of preferential flow paths. We present an integrated interpretation of a 3D geoelectric data set, 2D crosshole radar and seismic tomograms and the results of sparse direct-push slug tests that allows us to identify potential preferential flow paths within an alluvial aquifer in northwest Switzerland. The 3D electrical resistivity model is divided into clusters of high and low electrical resistivity using a fuzzy c-means cluster analysis technique. Despite significant differences in resolution, dominant structures identified in a 2D cross-section extracted from the clustered 3D resistivity model largely coincide with those obtained from an independent fuzzy c-means cluster analysis of crosshole radar and seismic tomograms. By linking the 3D electrical resistivity clusters to hydraulic conductivity measurements obtained from a limited number of slug tests, we derive a 3D aquifer model distinguished by zones of increased hydraulic conductivity that may act as preferential flow paths.