Integrating Geophysical Well Logs, Surface Geophysics, And Hydraulic Test And Geologic Data In Ground-Water Studies - Theory And Case Histories

Integration of surface geophysical surveys, borehole geophysics,<br>hydraulic tests, and geologic data has the potential to: 1) relate detailed<br>aquifer properties at specific well locations to large-scale structure mapped<br>across an investigation site; and 2) calibrate geophysical measurements in<br>terms of hydraulic variables of direct interest in most contaminant dispersion<br>studies. This paper reviews the physical and mathematical constraints on the<br>formal inversion of such data sets as illustrated by a number of case studies.<br>Our analysis demonstrates that the coupled inversion of these data depends on<br>1) formulation and verification of a specific site model, 2) statistical<br>sampling of the distribution of formation properties which depends mostly on<br>the number of boreholes, 3) specific location of boreholes with respect to<br>contacts and boundaries given in the model and interpretation. The importance<br>of these considerations is demonstrated by the synthesis of various field<br>studies including photo lineament analyses, magnetic surveys, surface seismic<br>reflection profiles and electrical resistivity soundings with well logs, and<br>with the results of various hydraulic tests. The case histories illustrate<br>the importance of logs in formulating and testing specific site models. These<br>results repeatedly demonstrate the need for obtaining logs from enough<br>boreholes to relate the boundaries and contacts inferred from surface surveys<br>to the much greater vertical spatial resolution given by the logs.