Is it More Important to Characterize Heterogeneity or Differences in Hydraulic Conductivity Measurements?

As a first step toward understanding the role of sedimentary structures in flow and transport through porous media, this work deterministically examines how transport simulations compare to observed transport through simple, artificial structures in a laboratory experiment. Small-scale laboratory-measured values of hydraulic conductivity were used to simulate transport in an intermediate-scale (10-m long), two-dimensional, heterogeneous porous medium (s 2 lnK=1.26, mlnK = 4.18, where K is cm hr-1 ). Results were judged based on how well the simulated transport matched observed transport through the tank. Permeameter and column experiments produced laboratory measurements of hydraulic conductivity for each of the five sands used in the intermediate-scale experiments. Despite explicit numerical representation of the heterogeneity, predictions using the laboratory-measured values under-estimated the mean arrival time by as much as 35%. The significance of differences between simulated and observed mean arrival time was investigated by comparing variability of transport predictions using the different measurement methods to that produced by different realizations of the heterogeneous distribution. Results indicate that the variations in measured hydraulic conductivity were more important to transport than variations between realizations of the heterogeneous distribution of hydraulic conductivity.