REGULARIZED INVERSION OF TOMOGRAPHIC PUMPING TESTS IN THE KANSAS RIVER VALLEY ALLUVIAL AQUIFER

A tomographic approach to the analysis of hydraulic tests in aquifers – essentially simultaneous analysis of multiple tests or stresses on the flow system – can help to reduce the nonuniuqueness of the estimated distribution of flow properties (primarily hydraulic conductivity, K). In addition to adopting the simultaneous inversion approach of geophysical tomography, hydrogeologists can also benefit from some of the associated diagnostic tools employed in geophysical inversion, including model resolution analysis and systematic analysis of the effects of different levels of regularization or model smoothing on the model fit. These diagnostic tools help to clarify the degree of confidence we can place in the estimated parameters, particularly which regions of the estimated K field are well resolved by the data and which can be estimated only in a bulk fashion. In this presentation I demonstrate the application of these tools to a set of tomographic pumping tests at a site in the Kansas River valley northeast of Lawrence, Kansas. In addition, I present a preliminary assessment of a technique for incorporating information from crosshole radar surveys into the hydrologic estimation problem through a nonparametric (smoothing spline) representation of the relationship between K and radar velocity and attenuation.