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1. A Non-Local Richards Equation to Model Unsaturated Flow in Highly Heterogeneous Media under Nonequilibrium Pressure Conditions

Author:
Neuweiler, Insa; Erdal, Daniel; Dentz, Marco
Source:
Vadose zone journal 2012 v.11 no.3
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; equations; mass transfer; mathematical models; prediction; seeds; vadose zone; water content;     Show all 8 Subjects
Abstract:
... We study the impact of mass transfer between high and low conductivity zones on flow in unsaturated media. A dual continuum approach that assumes capillary-dominated flow in the slow continuum gives a system of coupled flow equations for the water saturations in the mobile and in the slow domain, whose coupling term is directly related to the evolution of the averaged water content in the slow dom ...
DOI:
10.2136/vzj2011.0132

2. Reactive Transport Modeling of Natural Carbon Sequestration in Ultramafic Mine Tailings

Author:
Bea, S.A.; Wilson, S.A.; Mayer, K.U.; Dipple, G.M.; Power, I.M.; Gamazo, P.
Source:
Vadose zone journal 2012 v.11 no.2 pp. 1976-1982
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; calcium carbonate; calcium sulfate; carbon dioxide; carbon sequestration; climate; dolomite; energy accounting; energy balance; epsomite; equations; gypsum; magnesite; magnesium; magnesium carbonate; magnesium hydroxide; mine tailings; mineralization; models; serpentine; sodium chloride; solutes; trapping; vadose zone; vapors; weathering; Australia;     Show all 27 Subjects
Abstract:
... Atmospheric CO2 is naturally sequestered in ultramafic mine tailings as a result of the weathering of serpentine minerals [Mg3Si2O5(OH)4] and brucite [Mg(OH)2], and subsequent mineralization of CO2 in hydrated magnesium carbonate minerals, such as hydromagnesite [Mg5(CO3)4(OH)2·4H2O]. Understanding the CO2 trapping mechanisms is key to evaluating the capacity of such tailings for carbon sequestrat ...
DOI:
10.2136/vzj2011.0053

3. Water Retention in a Coarse Soil Pocket under Wetting and Drainage Cycles

Author:
Sakaki, Toshihiro; Limsuwat, Anuchit; Cihan, Abdullah; Frippiat, Christophe C.; Illangasekare, Tissa H.
Source:
Vadose zone journal 2012 v.11 no.1 pp. 0
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; air; air flow; atmospheric pressure; drainage; engineering; equations; laboratory experimentation; models; remote sensing; sand; soil physics; soil water; vadose zone;     Show all 14 Subjects
Abstract:
... In conventional hydrologic, environmental, and engineering problems, soil moisture processes need to be understood at spatial scales ranging from the meter to several kilometers. However, new research issues in vadose zone hydrology have recently raised the need to focus on soil moisture processes at spatial resolutions that are significantly finer than those used in conventional soil physics and ...
DOI:
10.2136/vzj2011.0028

4. Can Continuum Extensions to Multiphase Flow Models Describe Preferential Flow?

Author:
DiCarlo, David A.
Source:
Vadose zone journal 2010 v.9 no.2 pp. 268-277
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; data collection; equations; models; porous media; preferential flow; space and time; vadose zone;     Show all 8 Subjects
Abstract:
... Gravity-driven preferential flow paths (fingers) have been shown to be the result of nonmonotonic saturation profiles observed during constant-flux, one-dimensional infiltration. These nonmonotonic profiles, also known as saturation overshoot, cannot be described by traditional unsaturated continuum flow models, such as the Richards equation. Instead, continuum models require additional extensions ...
DOI:
10.2136/vzj2009.0099

5. Theory for Source-Responsive and Free-Surface Film Modeling of Unsaturated Flow

Author:
Nimmo, John R.
Source:
Vadose zone journal 2010 v.9 no.2 pp. 295-306
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; equations; irrigation; laminar flow; models; prediction; preferential flow; rain; soil water; soil water content; vadose zone; water supply; water table;     Show all 13 Subjects
Abstract:
... A new model explicitly incorporates the possibility of rapid response, across significant distance, to substantial water input. It is useful for unsaturated flow processes that are not inherently diffusive, or that do not progress through a series of equilibrium states. The term source-responsive is used to mean that flow responds sensitively to changing conditions at the source of water input (e. ...
DOI:
10.2136/vzj2009.0085

6. A Quasilinear Model for Solute Transport under Unsaturated Flow

Author:
Houseworth, J. E.; Leem, J.
Source:
Vadose zone journal 2009 v.8 no.4 pp. 1031-1037
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; radionuclides; unsaturated conditions; equations; solutes; pollutants; soil transport processes;     Show all 8 Subjects
Abstract:
... We developed an analytical solution for solute transport under steady-state, two-dimensional, unsaturated flow and transport conditions for the investigation of high-level radioactive waste disposal. The two-dimensional, unsaturated flow problem is treated using the quasilinear flow method for a system with homogeneous material properties. Dispersion is modeled as isotropic and is proportional to ...
DOI:
10.2136/vzj2009.0022

7. Design Hydraulic Loading Rates for Onsite Wastewater Systems

Author:
Radcliffe, D. E.; West, L. T.
Source:
Vadose zone journal 2009 v.8 no.1 pp. 64-74
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; saturated hydraulic conductivity; textural soil types; simulation models; high water table; drainage systems; equations; wastewater treatment; sewage effluent; soil texture; septic systems; soil profiles; drainage; drainage water;     Show all 14 Subjects
Abstract:
... Design hydraulic loading rates (HLRD) are used in specifying the area of the bottom of drainfield trenches required for onsite wastewater systems (OWSs). Our objective was to develop a method for estimating the HLRD based on soil and biomat hydraulic properties. We used a two-dimensional computer model to determine the steady flux through the trench bottom for the 12 USDA soil textural classes wit ...
DOI:
10.2136/vzj2008.0045

8. MODFLOW SURFACT: A State-of-the-Art Use of Vadose Zone Flow and Transport Equations and Numerical Techniques for Environmental Evaluations

Author:
Panday, Sorab; Huyakorn, Peter S.
Source:
Vadose zone journal 2008 v.7 no.2 pp. 610-631
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; soil pollution; equations; soil transport processes; nonaqueous phase liquids; vadose zone; hydrologic models; saturated flow;     Show all 9 Subjects
Abstract:
... MODFLOW SURFACT is a state-of-the-art simulator that utilizes vadose zone flow and transport equations to provide practical solutions to the analysis of flow and contaminant transport at various levels of complexity and sophistication as needed for site evaluation and closure. The variably saturated flow equation can be solved with standard retention functions or with bimodal or multimodal relativ ...
DOI:
10.2136/vzj2007.0052

9. Time-Lapse GPR Tomography of Unsaturated Water Flow in an Ice-Contact Delta

Author:
Farmani, M. Bagher; Keers, Henk; Kitterød, Nils-Otto
Source:
Vadose zone journal 2008 v.7 no.1 pp. 272-283
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; ground-penetrating radar; tomography; vadose zone; ice; soil water content; soil heterogeneity; infiltration (hydrology); soil water balance; snow; equations; Norway;     Show all 12 Subjects
Abstract:
... Cross-well ground penetrating radar (GPR) data sets were collected in the vadose zone of an ice-contact delta near Oslo's Gardermoen Airport (Norway) before, during, and after snowmelt in 2005. The observed travel times were inverted using curved-ray travel time tomography. The tomograms are in good agreement with the local geologic structure of the delta. The tomographic results were confirmed in ...
DOI:
10.2136/vzj2006.0132

10. Dipole-Generated Unsaturated Flow in Gardner Soils

Author:
Kacimov, Anvar
Source:
Vadose zone journal 2007 v.6 no.1 pp. 168-174
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; mathematical models; soil water content; equations; soil heterogeneity; soil morphology; spatial variation;     Show all 7 Subjects
Abstract:
... The Bystrov explicit analytical solution for viscous, low-Reynolds number flow in layers of variable thickness is interpreted as infiltration in a Gardner homogeneous soil obstructed by a subterranean cavity, stone, or other obstacle. Mathematically, the two-dimensional advection–dispersion equation for the Kirchhoff potential is solved by combination of a term responsible for incident unidirectio ...
DOI:
10.2136/vzj2005.0141

11. Upscaling Schemes and Relationships for the Gardner and van Genuchten Hydraulic Functions for Heterogeneous Soils

Author:
Zhu, J.; Young, M.H.; Van Genuchten, M.T.
Source:
Vadose zone journal 2007 v.6 no.1 pp. 186
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; desert soils; soil heterogeneity; soil hydraulic properties; mathematical models; equations; soil water movement; soil water content; surface layers;     Show all 9 Subjects
Abstract:
... Upscaled soil hydraulic properties are needed for many large-scale hydrologic applications such as regional and global climate studies and investigations of land-atmosphere interactions. Many larger scale subsurface flow and contaminant transport studies also require upscaled hydraulic property estimates. The objectives of this study were to develop a methodology for upscaling hydraulic property f ...
Handle:
10113/3498
DOI:
10.2136/vzj2006.0041

12. Comments on "A Set of Analytical Benchmarks to Test Numerical Models of Flow and Transport in Soils"

Author:
Groenendijk, P.; Kroes, J.G.; Dam, J.C. van
Source:
Vadose zone journal 2006 v.5 no.1 pp. 126-127
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; vadose zone; soil water movement; mathematical models; hydrologic models; equations;     Show all 6 Subjects
DOI:
10.2136/vzj2005.0077L

13. Analytical solutions for vertical flow in unsaturated, rooted soils with variable surface fluxes

Author:
Yuan, F.; Lu, Z.
Source:
Vadose zone journal 2005 v.4 no.4 pp. 1743-1756
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; soil water content; unsaturated hydraulic conductivity; equations; algorithms; plant-water relations; water uptake; roots; soil water movement;     Show all 10 Subjects
Abstract:
... Analytical solutions to Richards' equation have been derived to describe the distribution of pressure head, water content, and fluid flow for rooted, homogeneous soils with varying surface fluxes. The solutions assume that (i) the constitutive relations for the hydraulic conductivity and water content as function of the pressure head are exponential, (ii) the initial water content distribution is ...

14. Simulation of unsaturated flow in complex fractures using smoothed particle hydrodynamics

Author:
Tartakovsky, A.M.; Meakin, P.
Source:
Vadose zone journal 2005 v.4 no.3
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; soil pore system; equations; soil water movement; vadose zone; hydrologic models;     Show all 7 Subjects
Abstract:
... Smoothed particle hydrodynamics (SPH) models were used to simulate unsaturated flow in fractures with complex geometries. The SPH is a fully Lagrangian particle-based method that allows the dynamics of interfaces separating fluids to be modeled without employing complex front tracking schemes. In SPH simulations, the fluid density field is represented by a superposition of weighting functions cent ...

15. A set of analytical benchmarks to test numerical models of flow and transport in soils

Author:
Vanderborght, J.; Kasteel, R.; Herbst, M.; Javaux, M.; Thiery, D.; Vanclooster, M.; Mouvet, C.; Vereecken, H.
Source:
Vadose zone journal 2005 v.4 no.1
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; vadose zone; soil water movement; mathematical models; hydrologic models; equations;     Show all 6 Subjects
Abstract:
... Accurate model predictions of water flow and solute transport in unsaturated soils require a correct representation of relevant mechanisms in a mathematical model, as well as correct solutions of the mathematical equations. Because of the complexity of boundary conditions and the nonlinearity of the processes considered, general solutions of the mathematical equations rely on numerical approximati ...

16. Darcy's Law and unsaturated flow

Author:
Narasimhan, T.N.
Source:
Vadose zone journal 2004 v.3 no.4
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; unsaturated conditions; equations; mathematical models; hydraulic conductivity;     Show all 5 Subjects

17. The relative connectivity-tortuosity tensor for conduction of water in anisotropic unsaturated soils

Author:
Raats, P.A.C.; Zhang, Z.F.; Ward, A.L.; Gee, G.W.
Source:
Vadose zone journal 2004 v.3 no.4
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; soil pore system; unsaturated hydraulic conductivity; unsaturated conditions; equations; vadose zone; soil water movement;     Show all 7 Subjects
Abstract:
... The hydraulic conductivity of unsaturated anisotropic soils has recently been described with a tensorial connectivity-tortuosity (TCT) concept. We present a mathematical formalization of the connectivity-tortuosity tensor, assuming that its principal axes coincide with those of the hydraulic conductivity tensor at saturation. The hydraulic conductivity tensor of such unsaturated anisotropic soils ...

18. Analytic Element Modeling of Cylindrical Drains and Cylindrical Inhomogeneities in Steady Two-Dimensional Unsaturated Flow

Author:
Bakker, Mark; Nieber, John L.
Source:
Vadose zone journal 2004 v.3 no.3 pp. 1038-1049
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; equations; hydraulic conductivity; models; porous media; steady flow; vadose zone;     Show all 7 Subjects
Abstract:
... The analytic element method, first developed for modeling flow in saturated porous media, is adapted to the solution of the governing equation for steady flow in unsaturated porous media. The governing equation for steady-state unsaturated flow is made amenable to analytic element solution through transformation with the Kirchhoff integral, representation of the hydraulic conductivity by an expone ...
DOI:
10.2136/vzj2004.1038

19. Inverse estimation of the unsaturated soil hydraulic properties from column outflow experiments using free-form parameterizations

Author:
Bitterlich, S.; Durner, W.; Iden, S.C.; Knabner, P.
Source:
Vadose zone journal 2004 v.3 no.3
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; estimation; unsaturated hydraulic conductivity; unsaturated conditions; equations; least squares; loam soils; vadose zone; soil water characteristic;     Show all 9 Subjects
Abstract:
... Inverse methods are increasingly used to estimate the hydraulic properties of unsaturated soils. The method generally uses a weighted least-squares approach in which numerically simulated data are fitted to measured data. In this study we used inverse methods to estimate the unsaturated soil hydraulic properties from continuous and multistep column outflow experiments. The method employs piecewise ...

20. Multiphase inverse modeling: review and iTOUGH2 applications

Author:
Finsterle, S.
Source:
Vadose zone journal 2004 v.3 no.3
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; soil pollution; equations; porous media; nonaqueous phase liquids; vadose zone; computer software; soil water movement;     Show all 9 Subjects
Abstract:
... Calibration of a numerical process model against laboratory or field data is often referred to as "inverse modeling." As the numerical simulation models become more complex, the number of parameters to be estimated generally increases, requiring new testing, modeling, and inversion strategies. The purpose of this survey is to review inverse modeling approaches for unsaturated and multiphase flow m ...

21. The TOUGH codes--a family of simulation tools for multiphase flow and transport processes in permeable media

Author:
Pruess, K.
Source:
Vadose zone journal 2004 v.3 no.3 pp. 179-192
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; simulation models; soil pollution; equations; pollutants; porous media; vadose zone; computer software; soil water movement;     Show all 9 Subjects
Abstract:
... Numerical simulation has become a widely practiced and accepted technique for studying flow and transport processes in the vadose zone and other subsurface flow systems. This article discusses a suite of codes, developed primarily at Lawrence Berkeley National Laboratory (LBNL), with the capability to model multiphase flows with phase change. We summarize history and goals in the development of th ...

22. Application of a Darcian approach to estimate liquid flux in a deep vadose zone

Author:
Hubbell, J.M.; Nicholl, M.J.; Sisson, J.B.; McElroy, D.L.
Source:
Vadose zone journal 2004 v.3 no.2
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; mathematical models; waste disposal; equations; tensiometers; basalt; vadose zone; soil water movement; Idaho;     Show all 9 Subjects
Abstract:
... Approaches for estimating liquid flux in the shallow (0-2 m) vadose zone are hindered by the high degree of spatial and temporal variability present near the land surface. It is hypothesized that high-frequency variations in flux will be damped with depth. This study was conducted to estimate deep liquid flux using the Darcian approach at a waste disposal site in south-central Idaho that is underl ...

23. Correspondence and upscaling of hydraulic functions for steady-state flow in heterogeneous soils

Author:
Zhu, J.; Mohanty, B.P.; Warrick, A.W.; Van Genuchten, M.T.
Source:
Vadose zone journal 2004 v.3 no.2
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; mathematical models; unsaturated hydraulic conductivity; equations; soil water movement;     Show all 5 Subjects
Abstract:
... Soil hydraulic parameters at relatively large scales (e.g., remote sensing footprints) are important for land-atmosphere interaction and general circulation models as well as other applications. Within this context, we investigated two major issues involving soil hydraulic properties: (i) hydraulic parameter correspondence among some of the more commonly used soil hydraulic conductivity functions ...

24. Evaluation of the conceptual flow model for a deep vadose zone system using advanced tensiometers

Author:
McElroy, D.L.; Hubbell, J.M.
Source:
Vadose zone journal 2004 v.3 no.1
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; mathematical models; waste disposal; radionuclides; hazardous waste; equations; tensiometers; basalt; vadose zone; soil water movement; Idaho;     Show all 11 Subjects
Abstract:
... Conceptual flow models provide a framework for predictive modeling of contaminant transport. This study tests the assumptions of steady-state flow and a unit hydraulic gradient in a 177-m-thick vadose zone beneath a mixed waste site, using a network of advanced tensiometers. The conceptual flow model at the waste site, located on the Idaho National Engineering Laboratory (INEEL), describes moistur ...

25. Unsaturated flow through a small fracture-matrix network. 2. Uncertainty in modeling flow processes

Author:
Fairley, J.P.; Podgorney, R.K.; Wood, T.R.
Source:
Vadose zone journal 2004 v.3 no.1
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; dolomite; simulation models; equations; limestone; porous media; diffusion; vadose zone; soil water movement;     Show all 9 Subjects
Abstract:
... Simulations of flow and transport in variably saturated fractured rock generally assume equilibrium conditions between the fractures and the porous matrix, leading to predictions that are dominated by a diffusive process. Contrary to these predictions, an increasing body of evidence suggests that fracture-dominated flow, under nonequilibrium conditions between the fractures and porous matrix, occu ...

26. Quantifying the effects of small-scale heterogeneities on flow and transport in undisturbed cores from the Hanford Formation

Author:
Pace, M.N.; Mayes, M.A.; Jardine, P.M.; Mehlhorn, T.L.; Zachara, J.M.; Bjornstad, B.N.
Source:
Vadose zone journal 2003 v.2 no.4
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; sediments; mathematical models; soil pollution; hazardous waste; unsaturated conditions; equations; pollutants; diffusion; preferential flow; vadose zone;     Show all 11 Subjects
Abstract:
... Accelerated migration of contaminants in the vadose zone has been observed beneath tank farms at the U.S. Department of Energy's Hanford Reservation, Richland, WA. This paper focuses on quantifying hydrologic processes that control the fate and transport of contaminants in the unsaturated sediments beneath the Hanford tank farms. The experimental approach involved the use of field relevant, long-t ...

27. Stochastic analysis of transient flow in heterogeneous, variably saturated porous media: the van Genuchten-Mualem constitutive model

Author:
Lu, Z.; Zhang, D.
Source:
Vadose zone journal 2002 v.1 no.1
ISSN:
1539-1663
Subject:
unsaturated flow,   etc   ; saturated flow; porous media; vadose zone; soil water movement; mathematical models; stochastic processes; equations; Monte Carlo method; temporal variation; spatial variation;     Show all 11 Subjects
Abstract:
... In this study, on the basis of the van Genuchten-Mualem constitutive relationship, we develop a general nonstationary stochastic model for transient, variably saturated flow in randomly heterogeneous media with the method of moment equations. We first derive partial differential equations governing the statistical moments of the flow quantities by perturbation expansions and then implement these e ...