Groundwater systems modelling

Johnson T. M. and DePaolo D. J. (1994) Interpretation of isotopic data in groundwater systems model development and application to Sr isotope data from Yucca Mountain. Water Resour. Res. 30, 1571-1587. 

Nelson, R.W. J.A. Schur. (1980). Assessment of effectiveness of geologic oscillation systems PATHS groundwater hydrologic model. Battelle, Pacific Northwest Laboratory, Richland, WA. 

Perez, A.I. et al. (1974). A water quality model for a conjunctive surface, groundwater system. Office of Water Research and Technology. Environmental Protection Agency, Washington, DC. 

Field information on a specific porous medium remains scarce compared to its complexity. Obviously, it is much simpler to take water samples in a river or in a lake than drilling holes that are spaced closely enough in order to depict the spatial variation of the groundwater system. Ironically, in many cases it is easier to invent complex models than to collect the field data that would be needed to validate the model for a given system. Therefore, mathematical models of aquifers are important additional tools to explore the potential behavior of aquifers under different conditions. 

Physical Approaches. Groundwater-exchange rates with lakes are traditionally estimated by careful measurements of hydraulic potentials within the groundwater system, followed by application of Darcy s law in the form of flow-net analysis or numerical modeling. However, these measurements can be time-consuming and costly, and can require monthly to weekly measurements at many piezometers to examine the three-dimensional nature of the hydraulic-potential field. In addition, characterization of the hydraulic conductivity of the aquifer is critical to physical approaches and typically leads to results with large uncertainties (I, 2). 

Massmann, J. W. (1989). Applying Groundwater Flow Models in Vapor Extraction System DesignJournal oJEnvironmental Engineering, 115(1), 129-149. 

Sorption and Desorption Isotherms. To model radionuclide transport in groundwater through geologic media, it is necessary to mathematically describe sorption and desorption in terms of isotherms. The Freundlich isotherm was found to accurately describe sorption and desorption of all radionuclides studied in the interbed-groundwater systems, except when precipitation of the radionuclide occurred. 

Effects of Groundwater Composition and Eh. Radionuclide sorption on geologic solids is dependent on the chemical composition of the groundwater solution and the redox potential (Eh) of the solid-groundwater system. Aquifers at various depths in the Columbia Plateau formation have -been observed to have significant differences in composition. To accurately model radionuclide migration, it is necessary to understand the effects of chemical components and Eh on sorption and solubility of key radionuclides. An additional benefit of this work is to better understand the mechanisms of sorption and desorption of the radionuclides. 

Figure 8.30. A model for the trace element and isotope characteristics of calcite cement zones 1,2 and 3 in Mississippian Lake Valley grainstones. Zones 1,2 and 3 calcites formed at different times during different stages in the evolution of the rock-groundwater system. (After Meyers and Lohmann, 1985.)...

Zheng C (1990) MT3D, A modular three-dimensional transport model for simulation of advection, dispersion, and chemical reactions of contaminants in groundwater systems. SS Papadopulos Associates, Rockville, MD... 

A basic outcome of the U-shape flow paths model and its many derivations was that all groundwater systems were discussed in terms of... 

This book provides the applied approach, incorporating maximum field observations, and parameters measured in field studies, enabling the reader to (a) understand the natural regimes of groundwater systems in specific case study areas, (b) understand the consequences of anthropogenic intervention, (c) reach conclusions and recommendations related to management of the water resource, and (d) establish boundary conditions that lead to conceptual models. 

Due to the difficulties of getting analytical solutions, many numerical methods were developed to simulate the solute transport and retention processes in the soil. Deane et al. (1999) analyzed the transport and fate of hydrophobic organic chemicals (HOCs) in consolidated sediments and saturated soils. Walter et al. (1994) developed a model for simulating transport of multiple thermodynamically reacting chemical substances in groundwater systems. Islam et al. (1999) presented a modeling... 

CLAASSEN AND WHITE Kinetic Data and Groundwater Systems 777 Chemical Kinetic Modeling Of The Rainier Mesa System... 

Kinetic modeling was used to estimate the effective surface area of aquifer in contact with a unit volume of ground water for a composite saturated-unsaturated groundwater system in southern Nevada. This aquifer property, not obtainable by other means, is necessary for realistic modeling of solute transport in ground-water systems. The results of the kinetic modeling indicate that... 

Plummer L. N., Parkhurst D. L., and Thorstenson D. C. (1983) Development of reaction models for groundwater systems. Geochim. Cosmochim. Acta 47, 665-685. 

As mentioned above, direct groundwater age estimation methods may not be well suited for all study areas or with all groundwater tracers. Often, groundwater age estimates are more easily and correctly achieved through incorporation data for natural tracers in analytical and/or numerical transport models. This is particularly true when multiple sources contribute to particular tracers, or when an accurate hydrogeological representation is needed for complex groundwater systems. 

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