A moment method for calculating groundwater flow uncertainty: the analysis of a landfill.

The numerical analysis or modelling of groundwater flow and solute migration in support of remedial investigation studies or applications for the development of sanitary landfills is a multi-step process. In the first step, a conceptual model of the site is developed. This description delineates the spatial domain, designates the lithologic zones assigning preliminary values to the hydraulic conductivities and porosities and establishes the boundary condition configuration. Modelling is then used to evaluate the conceptual model; an important objective being the confirmation of the conceptual model description and parameter selection. For many groundwater studies, little or no modelling analyses are undertaken. It is assumed that the posed conceptual model is correct. When modelling is included in a remedial investigation study or landfill application, it is usually deterministic in nature; the techniques of parameter estimation and stochastic modelling as described in the literature are rarely used. Many hydro-geologists feel that these techniques are too theoretical for practical use. While this may be true for some methods, some uncertainty techniques can be applied to practical problems.