Aquifer parameter estimation

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. 

OASIS Parameter Estimation System for Aquifer Restoration Models User s Manual Version 2.0... 

Jin-Yong Lee, ICang-Kun Lee. Analysis of the quality of parameter estimates from repeated pumping and slug tests in a fracture porous aquifer system in Wonju, ICorea. Ground Water, 1999, 37(5) 692-700. 

Rouen D, Scher H, Blunt M (1997) On the structure and flow processes in the capillary fringe of phreatic aquifers. Transp Porous Media 28 159-180 Rose CW (1993) The transport of adsorbed chemicals in eroded sediments. In Russo D, Dagan G (eds) Water flow and solute transport in soils. Springer, Heidelberg, pp 180-199 Rosenberry DO, Winter TC (1997) Dynamics of water-table fluctuations in an upland between two prairie-pothole wetlands in North Dakota. J Hydrol 191 266-289 Russo D (1997) On the estimation of parameters of log-unsaturated conductivity covariance from solute transport data. Adv Water Resour 20 191-205 Russo D, Toiber-Yasur 1, Laufer A, Yaron B (1998) Numerical analysis of field scale transport of bromacU. Adv Water Resour 21 637-647... 

Hints and Help Assume, as a first approximation, that water temperature is a conservative, nonretarded parameter. You can then interpret the fw value calculated for PCE as a retardation factor relative to water temperature. Then you may try to estimate the retardation of water temperature. To do so it may be helpful to assume, as a rough estimate, an average value for the specific heat of the solids in the aquifer, cp, of 1 J g- K-. ... 

A technique for determination of effective aquifer surface area in contact with percolating ground water has been presented. The method utilizes laboratory-determined chemical kinetic dissolution data with geologic, hydrologic, and ground-water-quality data to yield an estimate of effective aquifer surface area, a parameter not obtained by other techniques. 

The rate at which groundwater moves through an aquifer is not usually directly measurable, and thus it must be estimated from known relationships among measurable parameters. The discussion of groundwater flow presented here is only an introduction to the topic many of the relationships described are approximations, and most are restricted in their applicability to situations in which the flow of groundwater is steady over time. When a more detailed analysis is necessary, the reader is referred to the following texts on ground-water Bear (1972, 1979), Freeze and Cherry (1979), Heath (1984), Strack (1989), McWhorter and Sunada (1977), and Davis and de Wiest (1966). 

A model was built using the best estimates of the variables including volumetries, stratigraphy, leak window area, hydrocarbon and aquifer properties. By producing hydrocarbons, the pressure in one block was depleted at the measured rate while the depletion profiles of the non-producing block were monitored. The least known parameter, the transmissibility of the faults, was varied until a history match was achieved between the modelled and observed depletion profiles. Comparison for different faults showed that faults with small displacements had to be modelled with higher transmissibilities than faults with large displacements. 

Of course, inverse-modeling approaches can also be used to determine the parameters of numerical ground-water transport models from fits to observed tracer data. Estimates of residence times for a number of locations in an aquifer provide a powerful calibration target for numerical ground-water transport models. If enough data are available to constrain the numerous unknowns in such models, this is presumably the most effective way to extract useful information from tracer data, in particular because the numerical models can be used to make predictions for the future development of the investigated system. Such predictions may become much more constrained and trustworthy if the model has been calibrated against tracer data. 

The rate at which groundwater moves through an aquifer is not usually directly measurable, and thus it must be estimated from knovm relationships among measurable parameters. The discussion of groimdwater flow... 

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