Improved aquifer characterization using a combination of Hydraulic Tomography and Tracer Testing
P 13.1 in Reactive transport modeling
In recent years, hydraulic tomography has become a more spread method for the characterization of the spatial distribution of hydraulic parameters. Even though this method is able to better reveal subsurface heterogeneity, many details of the hydraulic conductivity distribution remain unresolved that are important for solute transport. Against this background, we developed an approach combining data from hydraulic tomography experiments with tracer testing to gain improved predictions of solute transport. In this work we present the application of the approach for which we estimated the hydraulic-conductivity field in an alluvial aquifer by inverting tomographic pumping tests performed at the Hydrogeological Research Site Lauswiesen close to Tübingen using a regularized pilot-point method. We validated the estimated parameter field with direct-push injection logging profiles and hydraulic-head measurements not used in the inversion. The spatially uniform parameters for transport were estimated by fitting tracer data collected during a forced-gradient tracer test. The estimation required the assumption of a dual-porosity domain to parameterize effects of the unresolved heterogeneity of the aquifer and was necessary in the breakthrough curve fitting to achieve reasonable parameter values. With the estimated hydraulic-conductivity field and transport parameters we were able to successfully predict a second, independent tracer test. The work we present provides an efficient and practical approach to predict solute transport in heterogeneous aquifers without performing elaborate field tracer tests with a tomographic layout.