Mapping Aquifer Heterogeneity: Integrated Analysis of Electrical Resistance Tomography, Tracer Tests, and Hydraulic Data

Stanford University, Stanford CA

Investigators

Abstract

0124262 Gorelick Accurately characterizing flow and solute transport in groundwater systems is a critical problem in hydrology. In order to predict the fate and long-term transport of contaminants, an accurate depiction of the spatial variability of the hydraulic conductivity field is essential. Hydraulic conductivity measurements are generally too sparse to obtain a high-resolution image of the subsurface. Given the large volume of data required to develop an accurate model of subsurface flow, and the cost of direct sampling, the use of geophysical methods can contribute significantly to information about the subsurface. The focus of this research is two-fold. First is the use of electrical resistance topography (ERT) as a tool to map subsurface relative flow paths and flow barriers in detail. Second is the establishment of a systematic procedure capable of delineating hydraulic conductivity through integrated analysis of multiple data types. By analyzing these data together in a simulation-inversion framework, we intend to provide images of aquifer properties consistent with all data inversion framework, we intend to provide images of aquifer properties consistent with all data types. We plan to develop a multiple data type simulation-framework, and test it using results from laboratory-scale experiments collected in 6 x 8 x 6 foot sand tank at the Lamont Doherty Earth Observatory at Columbia University (funded independently by NSF) and field-scale demonstration at the Massachusetts Military Reservation on Cape Cod, Massachusetts. This work will quantify the worth of different types of data, and their combination, to develop high-resolution maps of aquifer properties. It will also improve the understanding of the relationship between electrical resistance and hydraulic conductivity. Both of these results will be valuable to physical hydrogeologist, contaminant hydrogeologists, and geophysicists.