Prediction of contaminant plumes (shapes, spatial moments and macrodispersion) in aquifers with insufficient geological information

Abstract

The first Macrodispersion Experiment (MADE1) at Columbus Air Force Base in northern Mississippi is utilized to perform numerical simulations of solute transport in an aquifer. The purpose is to illustrate the capability of the coupled Markov chain (CMC) model in delineating the complex geometrical configuration at the site for solute transport simulations under the lack of geological information. The CMC model is also used to study the effect of reducing geological information on the transport predictions in terms of plume configuration, first and second spatial moments and macrodispersion. The results show the power of the coupled Markov chain methodology in delineating aquifer heterogeneity at the site. Conditional simulations on 16, 9 and 6 boreholes show reasonably the same plume behavior in terms of average longitudinal and vertical extensions, especially in the far-field; 9 boreholes seem to provide practically acceptable results in terms of the global plume shape. This indicates more reliability on the use of the CMC model for subsurface characterization. Comparison of CMC model results, in terms of aquifer characterization, with the model used by Eggleston and Rojstaczer [Water Resour. Res. 34 (1998) 2155] (polynomial regression trend, Kalman filter trend, hydrofacies trend and Kriging) shows that the CMC model behaves better. The CMC model conditioned on 9 and 16 boreholes with mid-range conductivities for each lithology captures both the plume shape and the observed plume spatial moments at the MADE site.

Keywords:

• Heterogeneity
• conditioning
• flow
• transport
• field data
• Markov chains