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"Volume IVADOSE ZONE SCIENCE AND TECHNOLOGY SOLUTIONS Edited by Brian B. Looney, Ph.D. and Ronald W. Falta, Ph.D. 590 VADOSE ZONE SCIENCE AND TECHNOLOGY SOLUTIONS Chapter 5 Contents Introduction Physical Processes and Setting for Contaminant Flow and Transport in the Vadose Zone Introduction Physical Processes Transport Mathematical Models and Numerical Formulations Introduction Flow and Transport Equations Unsaturated Flow and Transport Equations Isothermal Multiphase Flow and Transport Equations Numerical Formulations Limitations and Research Directions Data Needs and Prioritization Introduction Different Types of Data Prioritization of Data Collection Methodology of Model Guidance in Data Collection Upscaling Issues Concluding Remarks Development of Site-Specific Models Introduction Objectives Conceptual Model Geometric Description Numerical Simulation Model Validation Using Geochemical and Isotopic Data Model Assessment: Predictions, Uncertainties, and Limitations Current Research Directions Model Calibration Introduction Methodology Error and Uncertainty Analysis Model Predictions and Their Uncertainties Examples Concluding Remarks Future Research Directions References Case Studies Modeling Fast Flow Paths in Unsaturated Fractured Rock TCE Contamination at the Savannah River Site Aqueous Diffusion in the Vadose Zone Measurement of Unsaturated-Zone Water Fluxes Adjacent to a Radioactive-Waste-Management Unit Integrated Geological Interpretation for Computational Modeling A Vadose Zone Injection Experiment for Testing Flow and Transport Models Inverse Estimation of Unsaturated Soil Hydraulic and Solute Transport Parameters Using the Hydrus 1-D Code 5 Flow and Transport Modeling of the Vadose Zone Gudmundur Bodvarsson, Stefan Finsterle, Hui Hai Liu, Curtis M. Oldenburg, Karsten Pruess, Eric Sonnenthal, and Yu-Shu Wu Introduction Over the last two decades tremendous advances have been made in flow and transport modeling of subsurface systems During the late 1970s and early 1980s simple analytical solutions or numerical analyses involving at most a few hundred gridblocks were the only available tools to address flow and transport problems Today it is common to use hundreds of thousands of gridblocks to solve flow and transport problems involving multiple processes and components These important advances in flow and transport modeling came about because of increased concern about environmental problems the need for efficient utilization of natural resources such as fossil energy and geothermal resources and the need for evaluation of geological disposal sites for radioactive waste products Figure 5-1 Various problems that are commonly addressed by flow and transport models Some of the complex geological features at multi-scale processes are shown However there are still significant uncertainties in flow and transport predictions for subsurface systems This chapter deals primarily with flow and transport modeling of the vadose zone using finite difference finite element and other conventional numerical methods These commonly used modeling approaches are based on macroscale continuum concepts that may not be applicable to certain problems and processes in the vadose zone Pruess et al 1999 Alternative approaches such as transfer functions Chestnut et al 1979 Jury 1982 weeps models Gauthier et al 1992 fracture network models see for example National Research Council 1996 and chaos models see for example Weeks and Sposito 1997 are not described here these are summarized in a recent article by Pruess et al 1999 In addition we discuss physical aspects of flow and transport modeling in the context of conventional hydrogeology which generally neglects complexities such as non-ideal waters and complex geochemical and biological reactions Nielsen et al 1986 In the hydrogeology and reservoir engineering literature the term model has different meanings This can be confusing because the specific meaning may become clear only from the context A conceptual model of a field site denotes a qualitative representation of major hydrogeologic features active constituents of the system fluid phases" Ключевые слова: clay, high, capillary, content, layer, porous, ij fk, mines golden, post-treatment land, environmental, science technology, matrix, air, iteratively updating, chapter, parameter, reaction, adsorptive force, chemical equilibria, rachford, numerical formulations, van genuchten, liquid, fluid, eds, concentration, science, field, depth, monitoring, hexavalent chromium, data, design, oxidant-demanding substance, medium, rate, nw se, flow transport, humic matter, wilson, study, application, function, monte carlo, hydrol, forested watershed, environmental aspects, extraction, organic chemicals, land farming, cubic yard, chemical, gallia member, seattle workshopsissues, modeling, highly soluble, vadose zone, site, equation, national, electrical conductivity, law governing, property, process, phase, diffuse-ion swarm, remediation, biogeochemical considerations, emerging technologies, atmospheric loading, clog pore, cost, sci, reductive dechlorination, civil engineers, flow, cone penetrometers, driving force, pu iv, heating, contamination, capillary force, mass, mn pb, sample, time, area, degrega eta, chemical oxidants, material, yucca mountain, mn ii, cr vi, micropore regime, wi, condition, table, kk, injection, water, wa mm, inverse problems, hydraulic conductivity, target zone, large, vadose buck, inoculated isolite, soc, barrier, performance, nc js, cap, kr, pressure, bgs, characterization, mn iv, hydraulic, soluble silicate, humid climate, picking eye, abd, surface, method, fracture, aq aq, raoults law, isotope, solution, percent, environ qual, ficks law, wa, ha, organic, dipole moment, distinct mobilities, site-specific models, technology, unsaturated, zz, underground facilities, situ, issue, temperature, zone science, measurement, pore, groundwater, result, component, contaminant, experiment, compound, strategic environmental, south carolina, neutron probe, west, based, chemical equilbrium, siegrist, siloxane cavity, problem, r s, permeability, higher-order differencing, metal, case, las vegas, vadose, san diego, mm, transport, cone penetrometer, darcys law, test, mm dl, microbial colonization, numerical, diffusion, vibratory cone, gas, press, subsurface, contaminated, waste, environmental restoration, environ, basic components, scale, henrys law, unsaturated regime, activated carbons, technology solutions, vapor, cr iv, pie chart, gas-napl two-phase, model, semi-arid climate, groutable, treatment, purely empirical, solutions, soil, analysis, conductivity, mm hg, reactive zone, chromium, steam, formation, laboratory, neutron logging, approach, zone, pore regime, smallest pore