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Uncertainty in Model Conceptualization: Case Study of Carbon Tetrachloride Migration in Groundwater

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  033105,  2003 ASAE Annual Meeting . (doi: 10.13031/2013.14058) @2003
Authors:   Ram C. Marahatta, Wayne E. Woldt
Keywords:   model conceptualization, uncertainty analysis, groundwater simulation, contaminant transportation, carbon tetrachloride

Simulation studies for groundwater contaminant migration are often associated with different types of uncertainties and imprecision. The imprecision associated with model conceptualization of a site is studied by comparing the results of two independent modeling efforts that were conducted to predict migration of a carbon tetrachloride (CCl4) plume. The two independent groundwater simulation studies were compared for a former USDA Commodity Credit Corporation (CCC) grain storage site near Raymond, Nebraska. Long-term prediction for extent of the plume, and plume concentration were found different in two simulations. Predicted CCl4 concentration in the municipal supply wells were also found different from the two model conceptualizations, high above the risk level from one simulation, and a little threat from the other for the same well. The multiple independent model conceptualization results from the same available data, and the decisions based on the preferred conceptualization, or a compromise of the available conceptualization is expected to offer better decisions on remedial action or deciding about the extent of the risk for the particular situation. As a result, the issue of multiple conceptualizations and their impact on simulation results for decision purposes is presented to the scientific and modeling communities to explore the methods of uncertainty analysis in model conceptualization.

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