Characterizing aquifer heterogeneity using hydraulic tomography

Abstract

Fine-scale heterogeneity in a geologic medium determines rates and directions of flow and of contaminant transport. Traditional methods of determining hydraulic conductivity provide only average values of hydraulic conductivity, as opposed to a distribution throughout the aquifer. Hydraulic tomography can be used to relate phase shifts and amplitude decays of a sinusoidal pressure signal to hydraulic conductivity. Hydraulic tomography can provide fine-scale interwell resolution, but processing methods require extensive time and computing power to handle the large amounts of data necessary. This tomography study comprises a combination of multiple offset gather surveys taken at the University of Kansas' Geohydrologic Experimental and Monitoring Site, a well-studied site in northeastern Kansas. A computer program has been developed to analyze the data by extending the 3D homogeneous spherical radial equation to the heterogeneous case. The analysis program is capable of efficiently resolving zones with dimensions of about one meter on each side.