In this study, we examined four tracer displacement experiments in a large undisturbed soil column under unsaturated steady-state conditions. Using electrical resistivity tomography (ERT), we were able to investigate the corresponding solute transport processes in unprecedented three-dimensional (3-D) spatiotemporally resolved detail. In addition, time-domain reflectometry (TDR) probes and tensiometers provided hydrologic state variables relevant to transport. One important result from the study is that despite considerable differences between soil hydrologic variables of the low- and high-flux experiments, the 3-D-resolved transport patterns remained approximately and were aligned to a structural feature in the topsoil. Furthermore, the ERT image data indicated that the front evolutions were influenced by spatiotemporal heterogeneities of the irrigation system. Another result is the column-scale mixing regime was found to be convective-dispersive, although the transport process exhibited heterogeneities at smaller scales. We introduced an upscaling approach that allowed us to predict the scale apparent dispersivity on the basis of the convection-dispersion equation parameters at the scale of the voxels. The approach proved to be useful to evaluate at which scale the apparent dispersivity was generated. We the investigation of the relationship between apparent dispersivity and lateral scale as a promising tool for solute transport in future studies.