Groundwater modeling

Air models Groundwater models Surface Water Models Muliiwedtii models... 

Models of atmospheric phenomena are similar to those of combustion and involve the coupling of exceedingly complex chemistry and physics with three-dimensional hydrodynamics. The distribution and transport of chemicals introduced into groundwater also involve a coupling of chemical reactions and transports through porous solid media. The development of groundwater models is critical to understanding the effects of land disposal of toxic waste (see Chapter 7). 

The groundwater model simulation indicates that the shallow aquifer could be restored to 5 pg/L (MCL) in 25 to 40 yr with soil remediation. Without soil remediation, between 60 and 100 yr would be required. 

Groundwater models and other analytic techniques are available to assist in proper pump siting, choosing pump capacities, and calculating the movement of the contaminant plume. The characteristics of the aquifer, the flow of groundwater, and the size of the plume should be known. 

There is no scientific reason for a soil model to be an unsaturated soil model only, and not to be an unsaturated (soil) and a saturated soil (groundwater) model. Only mathematical complexity mandates the differentiation, because such a model would have to be 3-dimensional (e.g., 7) and very difficult to operate. Most of the soil models account for vertical flows, groundwater models for horizontal flows. 

In the following sections more emphasis is placed on the unsaturated soil zone than on groundwater modeling. This emphasis can be justified by the fact that similar modeling concepts govern both environments. 

Saturated soil zone (or groundwater) modeling is formulated almost exclusively via a TDE system, consisting of two modules, the flow and the solute module. The two modules are written as (9) ... 

Mathematical groundwater modeling has been the least problematic in its scientific formulation, but has been the most problematic model category when dealing... 

Table 3 lists selected soil and groundwater models and their main features. Table 4 lists limitations and advantages of major model categories. Models listed in Table 3 are documented, operational and very representative of the various structures, features and capabilities. For example ... 

PATHS (30) is mainly an analytical groundwater model, that provides a rough evaluation of the spatial and temporal status of a pollutant fate. 

MMT (32) is a 1- or 2-dimensional solute transport numerical groundwater model, to be driven off-line by a flow transport, such as VTT (Variable Thickness Transport). MMT employs the random-walk numerical method and was originally developed for radionuclide transport. The model accounts for advection, sorption and decay. 

Important issues in groundwater model validation are the estimation of the aquifer physical properties, the estimation of the pollutant diffusion and decay coefficient. The aquifer properties are obtained via flow model calibration (i.e., parameter estimation see Bear, 20), and by employing various mathematical techniques such as kriging. The other parameters are obtained by comparing model output (i.e., predicted concentrations) to field measurements a quite difficult task, because clear contaminant plume shapes do not always exist in real life. 

Mercer, J.W. C.R. Faust (1981). Groundwater modeling. National Water Well Association, Washington, DC. 

Pollard, A.M. (1995). Groundwater modeling in archaeology - the need and the potential. In Science and Site, ed. Beavis J. and Barker K., Bournemouth University School of Conservation Sciences Occasional Paper 1, pp. 93-98. 

Anderson, M. R., Johnson, R. L., and Pankow, J. F., 1992, Dissolution of Dense Chlorinated Solvents into Groundwater. Modeling Contaminant Plumes Form Fingers and Pools of Solvent Environmental Science and Technology, Vol. 26, No. 5, pp. 901-907. 

Development of analytical and numerical groundwater models to (1) predict the fate and transport of LNAPL and its dissolved constituents (2) provide more reliable LNAPL volume determinations and (3) enhance design for optimal groundwater cleanup strategies ... 

Davis, A., Bellehumeur, T., Hunter, P. et al. (2006) The nexus between groundwater modeling, pit lake chemogenesis and ecological risk from arsenic in the Getchell main pit, Nevada, U.S.A. Chemical Geology, 228(1-3 Special Issue), 175-96. 

Organic Chemicals in Groundwater Modeling Fate and Transport... 

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