Inversion of tracer test data using tomographic constraints

We have developed a methodology for inverting tracer test data using zonation information obtained from two-dimensional radar tomograms to improve the (typically overly smooth) hydraulic conductivity fields obtained from conventional inversion of tracer test data. The method simultaneously yields two-dimensional estimates of hydraulic conductivity as well as petrophysical relationships that relate hydraulic conductivity to radar velocity; these relationships can be assumed to be stationary throughout the area of investigation or to vary as a function of zonation. Using a synthetic three-dimensional hydraulic conductivity field, we apply the developed inversion methodology and explore the impact of the strength and stationarity of the petrophysical relationship as well as the impact of errors that are often associated with radar data acquisition (such as unknown borehole deviation). We find that adding radar tomographic data to tracer test data improves hydrogeological site characterization, even in the presence of minor radar data errors. The results are contingent on the assumption that a relationship between radar velocity and hydraulic conductivity exists. Therefore the applicability of the proposed method may be limited to field sites where this condition is partially or fully satisfied.