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WATER RESOURCES RESEARCH, VOL. 40, W04211, doi:10.1029/2002WR001935, 2004

Investigating the Macrodispersion Experiment (MADE) site in Columbus, Mississippi, using a three-dimensional inverse flow and transport model

Heidi Christiansen Barlebo

Geological Survey of Denmark and Greenland, Copenhagen, Denmark


Mary C. Hill

U.S. Geological Survey, Boulder, Colorado, USA


Dan Rosbjerg

Environment and Resources DTU, Technical University of Denmark, Kongens Lyngby, Denmark


Abstract

Flowmeter-measured hydraulic conductivities from the heterogeneous MADE site have been used predictively in advection-dispersion models. Resulting simulated concentrations failed to reproduce even major plume characteristics and some have concluded that other mechanisms, such as dual porosity, are important. Here an alternative possibility is investigated: that the small-scale flowmeter measurements are too noisy and possibly too biased to use so directly in site-scale models and that the hydraulic head and transport data are more suitable for site-scale characterization. Using a calibrated finite element model of the site and a new framework to evaluate random and systematic model and measurement errors, the following conclusions are derived. (1) If variations in subsurface fluid velocities like those simulated in this work (0.1 and 2.0 m per day along parallel and reasonably close flow paths) exist, it is likely that classical advection-dispersion processes can explain the measured plume characteristics. (2) The flowmeter measurements are possibly systematically lower than site-scale values when the measurements are considered individually and using common averaging methods and display variability that obscures abrupt changes in hydraulic conductivities that are well supported by changes in hydraulic gradients and are important to the simulation of transport.

Received 20 December 2002; accepted 30 January 2004; published 22 April 2004.

Index Terms: 1832 Hydrology: Groundwater transport; 1829 Hydrology: Groundwater hydrology; 1869 Hydrology: Stochastic processes; 3260 Mathematical Geophysics: Inverse theory.

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Citation: Barlebo, H. C., M. C. Hill, and D. Rosbjerg (2004), Investigating the Macrodispersion Experiment (MADE) site in Columbus, Mississippi, using a three-dimensional inverse flow and transport model, Water Resour. Res., 40, W04211, doi:10.1029/2002WR001935.