LETTERS TO THE EDITOR:

T. N. Narasimhan

Darcy's Law and Unsaturated Flow
The author asserts that the equation of motion for water in an unsaturated soil deserves an identity that is distinct from Darcy's Law.
Vadose Zone J 2004 3: 1059. [Full Text] [PDF]  

SPECIAL SECTION: HYDROGEOPHYSICS:

H. Vereecken, S. Hubbard, A. Binley, and T. Ferré

Hydrogeophysics: An Introduction from the Guest Editors
The guest editors introduce the special section and the scope of the hydrogeophysics papers. The papers present methods for estimating hydrogeological parameters using GPR, TDR, and induced polarization for monitoring the dynamics of processes based on resistivity and EM-induction methods and for advanced characterization of the subsurface through improved instrumentation, inversion approaches, acquisition geometry, or data processing.
Vadose Zone J 2004 3: 1060-1062. [Full Text] [PDF]  

S. Lambot, J. Rhebergen, I. van den Bosch, E. C. Slob, and M. Vanclooster

Measuring the Soil Water Content Profile of a Sandy Soil with an Off-Ground Monostatic Ground Penetrating Radar
Ground penetrating radar (GPR) signal analyses were applied to synthetic GPR data and to GPR data measured for a large sand tank. The purpose was to assess the possibility of identifying a continuously variable soil moisture profile from a single measurement with a highly mobile off-ground monostatic antenna.
Vadose Zone J 2004 3: 1063-1071. [Abstract] [Full Text] [Figures Only] [PDF]  

S. Lambot, M. Antoine, I. van den Bosch, E. C. Slob, and M. Vanclooster

Electromagnetic Inversion of GPR Signals and Subsequent Hydrodynamic Inversion to Estimate Effective Vadose Zone Hydraulic Properties
Effective soil hydraulic parameters are estimated by hydrodynamic inversion of soil moisture time series obtained by full-wave electromagnetic inversion of ground penetrating radar data. The method offers great promise for the laboratory- and field-scale hydraulic characterization using remote sensing.
Vadose Zone J 2004 3: 1072-1081. [Abstract] [Full Text] [Figures Only] [PDF]  

Olivier Loeffler and Maksim Bano

Ground Penetrating Radar Measurements in a Controlled Vadose Zone: Influence of the Water Content
The water content of a soil can be estimated with relations using the relative dielectric permittivity, which can be determined by GPR measurements. The estimates in variations of the amount of water in a sand box, obtained by GPR data, are compared with the actual variations of water imposed on the sand box. The results are very similar.
Vadose Zone J 2004 3: 1082-1092. [Abstract] [Full Text] [Figures Only] [PDF]  

Giorgio Cassiani, Claudio Strobbia, and Laura Gallotti

Vertical Radar Profiles for the Characterization of Deep Vadose Zones
Vertical radar profiling (VRP) is a noninvasive technique for monitoring moisture content changes in the vadose zone. This paper illustrates the acquisition and use of VRP data to monitor infiltration and unsaturated flow above a quaternary alluvial aquifer, and the use of these data to calibrate a model of the flow.
Vadose Zone J 2004 3: 1093-1105. [Abstract] [Full Text] [Figures Only] [PDF]  

Jürgen Schmalholz, Heiner Stoffregen, Andreas Kemna, and Ugur Yaramanci

Imaging of Water Content Distributions inside a Lysimeter using GPR Tomography
Ground penetrating radar has growing applications for investigating the vadose zone. Undisturbed flow processes can be studied because of the noninvasive nature of this method. An irrigation experiment illustrates the potential of this method for small-scale experimental setups.
Vadose Zone J 2004 3: 1106-1115. [Abstract] [Full Text] [Figures Only] [PDF]  

T. W. Miller, J. M. H. Hendrickx, and B. Borchers

Radar Detection of Buried Landmines in Field Soils
A radar transmission model was developed to evaluate field conditions for the use of GPR instruments in landmine detection. Model predictions were validated with GPR profiles measured in field soils representing various soil textures and soil water contents. Results demonstrate the potential and pitfalls of using GPR-based landmine sensors.
Vadose Zone J 2004 3: 1116-1127. [Abstract] [Full Text] [Figures Only] [PDF]  

Timo J. Heimovaara, Johan A. Huisman, Jasper A. Vrugt, and Willem Bouten

Obtaining the Spatial Distribution of Water Content along a TDR Probe Using the SCEM-UA Bayesian Inverse Modeling Scheme
A TDR waveform analysis methodology is presented that gives a quantitative estimate of the dielectric permittivity and therefore the water content profile along the length of a TDR probe. The method is based on a deterministic model of the TDR waveform, which makes the method applicable to standard TDR instrumentation and TDR probes.
Vadose Zone J 2004 3: 1128-1145. [Abstract] [Full Text] [Figures Only] [PDF]  

Magnus Persson, David Bendz, and Peter Flyhammar

Time-Domain Reflectometry Probe for Water Content and Electrical Conductivity Measurements in Saline Porous Media
A new time-domain reflectometry probe design for use in highly saline media was developed and tested. The new design combines the advantages of uncoated probes (i.e., electrical conductivity can be measured) and coated probes (i.e., water content measurements can be made at high electrical conductivity).
Vadose Zone J 2004 3: 1146-1151. [Abstract] [Full Text] [Figures Only] [PDF]  

B. Oswald, H. R. Benedickter, W. Bächtold, and H. Flühler

A Single-Rod Probe for Time Domain Reflectometry Measurements of the Water Content
A time domain reflectometry probe based on one single metallic rod is investigated for water content measurements. The probe is analyzed both experimentally and theoretically, and the derived characteristics are compared with those of the standard two-wire probes.
Vadose Zone J 2004 3: 1152-1159. [Abstract] [Full Text] [Figures Only] [PDF]  

K. Titov, A. Kemna, A. Tarasov, and H. Vereecken

Induced Polarization of Unsaturated Sands Determined through Time Domain Measurements
The electrical induced polarization properties of multiphase porous media are demonstrated to possess a complex dependency on the volumetric water content for sands containing air and water, and for sands containing kerosene and water. A model explaining such a behavior is proposed.
Vadose Zone J 2004 3: 1160-1168. [Abstract] [Full Text] [Figures Only] [PDF]  

K. Schneeberger, M. Schwank, C. Stamm, P. de Rosnay, C. Mätzler, and H. Flühler

Topsoil Structure Influencing Soil Water Retrieval by Microwave Radiometry
Radiometry is known as a passive remote sensing technique for measuring water contents in environmental science. Models used to infer water content from radiometry data are discussed, and the comparability between remotely sensed water content predictions and ground truth water content data is investigated.
Vadose Zone J 2004 3: 1169-1179. [Abstract] [Full Text] [Figures Only] [PDF]  

Alexis Maineult, Yves Bernabé, and Philippe Ackerer

Electrical Response of Flow, Diffusion, and Advection in a Laboratory Sand Box
Laboratory experiments were performed in a sand box to measure the electrical signal generated by flow of a homogeneous fluid, by diffusion of salt, and by advective transport of salt. Each of these phenomena produces a characteristic spontaneous electrical potential, analysis of which provides information about the motion of the fluid or of the salt front through the porous medium.
Vadose Zone J 2004 3: 1180-1192. [Abstract] [Full Text] [Figures Only] [PDF]  

B. Suski, E. Rizzo, and A. Revil

A Sandbox Experiment of Self-Potential Signals Associated with a Pumping Test
An electrical field of electrokinetic nature is produced in response to groundwater flow. A sandbox experiment is presented to analyze the electrical field associated with a pumping test in a Plexiglas tank filled with a tapwater-infiltrated sand. The response is analyzed both in steady-state pumping conditions and in the relaxation phase following the shutdown of the pump.
Vadose Zone J 2004 3: 1193-1199. [Abstract] [Full Text] [Figures Only] [PDF]  

Pascal Sailhac, Mathieu Darnet, and Guy Marquis

Electrical Streaming Potential Measured at the Ground Surface: Forward Modeling and Inversion Issues for Monitoring Infiltration and Characterizing the Vadose Zone
Electrical streaming potential monitoring is presented as a viable method for characterizing subsurface flow processes and for estimating subsurface hydraulic parameters. A modeling approach is presented that facilitates this characterization and the parameter estimation. The procedures are demonstrated using steady-state infiltration numerical simulations.
Vadose Zone J 2004 3: 1200-1206. [Abstract] [Full Text] [Figures Only] [PDF]  

Laila M. Hall, James R. Brainard, Robert S. Bowman, and Jan M. H. Hendrickx

Determination of Solute Distributions in the Vadose Zone Using Downhole Electromagnetic Induction
Downhole electromagnetic induction was used to track the migration of a NaCl plume in the vadose zone under steady water flow conditions. The plume evolved in a manner consistent with site stratigraphy. The calculated mass of added NaCl was more dependent on the assumed immobile water content than on clay content or temperature.
Vadose Zone J 2004 3: 1207-1214. [Abstract] [Full Text] [Figures Only] [PDF]  

Daniel Cornacchiulo and Amvrossios C. Bagtzoglou

Geostatistical Reconstruction of Gaps in Near-Surface Electrical Resistivity Data
The impact of noise and data gaps (random or coherent) on the inversion of electrical resistivity is assessed. Results indicate that a geostatistical reconstruction of the data gaps prior to the inversion improved the interpretability of near-surface electrical resistivity profiles and the associated inference of geologic structure.
Vadose Zone J 2004 3: 1215-1229. [Abstract] [Full Text] [Figures Only] [PDF]  

Alex Furman, Ty P. A. Ferré, and Art W. Warrick

Optimization of ERT Surveys for Monitoring Transient Hydrological Events Using Perturbation Sensitivity and Genetic Algorithms
A genetic algorithm and perturbation sensitivity analysis are combined to optimize electrical resistivity tomography surveys. This optimization method opens the way for tailored, time evolving, monitoring of vadose zone flow and transport processes.
Vadose Zone J 2004 3: 1230-1239. [Abstract] [Full Text] [Figures Only] [PDF]  

REVIEWS AND ANALYSES:

David Werner, Peter Grathwohl, and Patrick Höhener

Review of Field Methods for the Determination of the Tortuosity and Effective Gas-Phase Diffusivity in the Vadose Zone
Different approaches have been described for the in situ measurement of the gas-phase diffusivity in the vadose zone. This review compares the experimental setups and compiles a database of measured field data, which is compared with the predictions of porosity-based empirical relationships.
Vadose Zone J 2004 3: 1240-1248. [Abstract] [Full Text] [Figures Only] [PDF]  

ORIGINAL RESEARCH:

Peter Engesgaard, Anker L. Højberg, Klaus Hinsby, Karsten H. Jensen, Troels Laier, Flemming Larsen, Eurybiades Busenberg, and L. Niel Plummer

Transport and Time Lag of Chlorofluorocarbon Gases in the Unsaturated Zone, Rabis Creek, Denmark
Numerical and analytical solution methods are presented for analyzing time lags of CFC gases in the unsaturated zone using data from a Danish field site. Results illustrate the effects of changes in water content, thickness of the unsaturated zone, and effective diffusion on calculated time lags.
Vadose Zone J 2004 3: 1249-1261. [Abstract] [Full Text] [Figures Only] [PDF]  

Petros Gaganis, Peter Kjeldsen, and Vasilis N. Burganos

Modeling Natural Attenuation of Multicomponent Fuel Mixtures in the Vadose Zone: Use of Field Data and Evaluation of Biodegradation Effects
A field experiment was used to explore the potential for predictive modeling of multicomponent VOC mixture transport in the vadose zone. Biodegradation rate constants obtained from column experiments, coupled with site-specific hydrological data, were used to simulate field-scale attenuation. The results were compared with field measurements.
Vadose Zone J 2004 3: 1262-1275. [Abstract] [Full Text] [Figures Only] [PDF]  

Patrick Höhener and Heinz Surbeck

Radon-222 as a Tracer for Nonaqueous Phase Liquid in the Vadose Zone: Experiments and Analytical Model
We hypothesized that anomalies in the depth distribution of the natural soil gas radon-222 at contaminated sites may be useful to indicate the presence and quantity of nonaqueous phase liquids. The hypothesis is tested using data from laboratory and lysimeter experiments in conjunction with transport modeling.
Vadose Zone J 2004 3: 1276-1285. [Abstract] [Full Text] [Figures Only] [PDF]  

David Russo, Jacob Zaidel, and Asher Laufer

Numerical Analysis of Transport of Interacting Solutes in a Three-Dimensional Unsaturated Heterogeneous Soil
Field-scale flow and transport in a three-dimensional, heterogeneous, variably saturated soil are analyzed for the case where the hydraulic conductivity and water retention depend on solute concentrations. Results of the analyses have practical implications regarding the use of sewage water for irrigation.
Vadose Zone J 2004 3: 1286-1299. [Abstract] [Full Text] [Figures Only] [PDF]  

Nathan W. Haws and P. Suresh C. Rao

The Effect of Vertically Decreasing Macropore Fractions on Simulations of Non-Equilibrium Solute Transport
A soil with a depth-decreasing macropore fraction is represented using a simple pore-network model and a dual-porosity domain. Numerical simulations are conducted for different saturation levels to demonstrate how the decreasing macropore fraction influences non-equilibrium transport.
Vadose Zone J 2004 3: 1300-1308. [Abstract] [Full Text] [Figures Only] [PDF]  

J. Maximilian Köhne, Sigrid Köhne, Binayak P. Mohanty, and Jirka Simunek

Inverse Mobile–Immobile Modeling of Transport During Transient Flow: Effects of Between-Domain Transfer and Initial Water Content
The hydraulic and transport parameters for two distinct mobile-immobile models were estimated through an inverse simulation procedure using water flow and bromide transport variables measured on columns of aggregated loamy soil. The effect of initial moisture content on reliability of parameter estimates was evaluated.
Vadose Zone J 2004 3: 1309-1321. [Abstract] [Full Text] [Figures Only] [PDF]  

M. Javaux and M. Vanclooster

In Situ Long-Term Chloride Transport through a Layered, Nonsaturated Subsoil. 1. Data Set, Interpolation Methodology, and Results
Data on chloride concentration in an artificial lake and at seven depths in the underlying vadose zone were used to estimate the transport parameters and their uncertainty for the unsaturated zone. The parameter uncertainty is partially related to the lack of temporal resolution in lake water chloride concentration measurements.
Vadose Zone J 2004 3: 1322-1330. [Abstract] [Full Text] [Figures Only] [PDF]  

M. Javaux and M. Vanclooster

In Situ Long-Term Chloride Transport through a Layered, Nonsaturated Subsoil. 2. Effect of Layering on Solute Transport Processes
Soil stratification, by inducing two- or three-dimensional transport processes, may considerably affect solute dispersion. The analysis of the chloride time series in the layered vadose zone between a lake and an underlying aquifer illustrates that flow variability is extremely high, probably due to an unstable front below clay-sand interfaces.
Vadose Zone J 2004 3: 1331-1339. [Abstract] [Full Text] [Figures Only] [PDF]  

K. C. Abbaspour, C. A. Johnson, and M. Th. van Genuchten

Estimating Uncertain Flow and Transport Parameters Using a Sequential Uncertainty Fitting Procedure
A procedure is presented for parameter estimation using inverse modeling. The SUFI-2 approach calculates parameter as well as prediction uncertainty for models with a large number of parameters. The procedure employs a global search; it is efficient and easy to implement.
Vadose Zone J 2004 3: 1340-1352. [Abstract] [Full Text] [Figures Only] [PDF]  

K. Nakamura, T. Harter, Y. Hirono, H. Horino, and T. Mitsuno

Assessment of Root Zone Nitrogen Leaching as Affected by Irrigation and Nutrient Management Practices
Split-application of nitrate fertilizer during a cropping period is generally known to reduce the leaching potential for nitrate-nitrogen. Combining experimental and simulation approaches we performed a long-term assessment of these practices for reducing nitrate-nitrogen leaching in cultivated Japanese upland soils.
Vadose Zone J 2004 3: 1353-1366. [Abstract] [Full Text] [Figures Only] [PDF]  

F. Hupet, J. C. van Dam, and M. Vanclooster

Impact of Within-Field Variability in Soil Hydraulic Properties on Transpiration Fluxes and Crop Yields: A Numerical Study
Combining field measurements and modeling, we show the importance of correctly specifying macroscopic water stress parameters for simulating water fluxes of a vegetated surface. A methodology is proposed to adjust water stress parameters according to variable within-field soil properties using reference unsaturated hydraulic conductivity values.
Vadose Zone J 2004 3: 1367-1379. [Abstract] [Full Text] [Figures Only] [PDF]  

David D. Bosch

Comparison of Capacitance-Based Soil Water Probes in Coastal Plain Soils
Results of testing two capacitance-based instruments that measure volumetric soil water under field conditions are described. Estimates of the accuracy of these instruments as well as relationships that can be used to improve their accuracy for Coastal Plain soils are presented.
Vadose Zone J 2004 3: 1380-1389. [Abstract] [Full Text] [Figures Only] [PDF]  

A. Fares, P. Buss, M. Dalton, A. I. El-Kadi, and L. R. Parsons

Dual Field Calibration of Capacitance and Neutron Soil Water Sensors in a Shrinking–Swelling Clay Soil
Soil moisture content was measured with a capacitance and a neutron probe for a duplex fine-textured soil, and the response of the soil dry bulk density to moisture content was quantified. Measurements from the two probes were compared and the need for site-specific calibration was evaluated.
Vadose Zone J 2004 3: 1390-1399. [Abstract] [Full Text] [Figures Only] [PDF]  

T. Yao, P. J. Wierenga, A. R. Graham, and S. P. Neuman

Neutron Probe Calibration in a Vertically Stratified Vadose Zone
Using field data it is shown that if neutron probes are used for determining water contents in deep vadose zones, layer-specific calibration equations are needed. A procedure to develop such calibration equations is presented.
Vadose Zone J 2004 3: 1400-1406. [Abstract] [Full Text] [Figures Only] [PDF]  

Alon Ben-Gal, Naftali Lazorovitch, and Uri Shani

Subsurface Drip Irrigation in Gravel-Filled Cavities
Subsurface drip irrigation within gravel-filled cavities is proposed to eliminate problems of backpressure and water surfacing. A theoretical solution relates the size of the cavity as a function of irrigation rate and soil properties. The method is tested with HYDRUS-2D and field data.
Vadose Zone J 2004 3: 1407-1413. [Abstract] [Full Text] [Figures Only] [PDF]  

Vicky L. Freedman, Diana H. Bacon, K. Prasad Saripalli, and Philip D. Meyer

A Film Depositional Model of Permeability for Mineral Reactions in Unsaturated Media
Permeability models are developed that describe mineral growth and reduction as a continuous film within the pore space. Changes in permeability and unsaturated hydraulic properties are determined based on changes in a discrete pore-size distribution and are described for a long-term low-level glassified waste facility.
Vadose Zone J 2004 3: 1414-1424. [Abstract] [Full Text] [Figures Only] [PDF]  

Qinhong Hu, Timothy J. Kneafsey, Jeffery J. Roberts, Liviu Tomutsa, and Joseph S. Y. Wang

Characterizing Unsaturated Diffusion in Porous Tuff Gravel
Chemical diffusion through unsaturated tuff gravels was measured using two approaches: electrical conductivity of bulk samples evaluated with the Nernst-Einstein equation, and microscale mapping of single grains using laser ablation. The results illustrate the very low diffusion potential in these gravels at low water content.
Vadose Zone J 2004 3: 1425-1438. [Abstract] [Full Text] [Figures Only] [PDF]  

Maria Inés Dragila and Noam Weisbrod

Flow in Menisci Corners of Capillary Rivulets
An analytical solution is developed to calculate the wetted contact area of a rivulet under capillarity tension in inclined unsaturated fractures as a function of contact angle and flow rate. Conditions under which matrix contact area can be approximated using a simpler rectangular rivulet cross section are also derived.
Vadose Zone J 2004 3: 1439-1442. [Abstract] [Full Text] [Figures Only] [PDF]  

T. P. Chan and R. S. Govindaraju

Estimating Soil Water Retention Curve from Particle-Size Distribution Data Based on Polydisperse Sphere Systems
New soil water retention models for coarse-textured soils are derived based on measured particle-size distribution and the theory of polydisperse sphere systems. Two distinct models are tested, the fully penetrable sphere model and the totally impenetrable sphere model, by comparing predicted retention curves to measured ones.
Vadose Zone J 2004 3: 1443-1454. [Abstract] [Full Text] [Figures Only] [PDF]  

Marcel G. Schaap, Attila Nemes, and Martinus Th. van Genuchten

Comparison of Models for Indirect Estimation of Water Retention and Available Water in Surface Soils
We used 47435 records from the NRCS soils database to evaluate 12 pedotransfer functions for estimating water retention parameters. Average root mean square errors ranged from 0.0687 cubic centimeters per cubic centimeter for a PTF that provided textural class average parameters to 0.0315 cubic centimeters per cubic centimeter for a model that also used two water retention points as predictors.
Vadose Zone J 2004 3: 1455-1463. [Abstract] [Full Text] [Figures Only] [PDF]  

Jianting Zhu and Binayak P. Mohanty

Soil Hydraulic Parameter Upscaling for Steady-State Flow with Root Water Uptake
The effective soil hydraulic parameters for steady-state flow across a heterogeneous landscape are derived by requiring that the effective medium discharge the ensemble mean flux across the soil surface. The effect of root water uptake on the effective medium parameters is assessed.
Vadose Zone J 2004 3: 1464-1470. [Abstract] [Full Text] [Figures Only] [PDF]  

Peter A. C. Raats, Z. Fred Zhang, Andy L. Ward, and Glendon W. Gee

The Relative Connectivity–Tortuosity Tensor for Conduction of Water in Anisotropic Unsaturated Soils
The hydraulic conductivity of an anisotropic unsaturated soil is described as the product of a water content-dependent scalar variable, a water content-dependent symmetric relative connectivity-tortuosity tensor, and a symmetric hydraulic conductivity tensor at saturation. The saturation dependence of the conductivity tensor is demonstrated.
Vadose Zone J 2004 3: 1471-1478. [Abstract] [Full Text] [Figures Only] [PDF]  

NOTES:

Grace W. Su, Joseph S. Y. Wang, and Kris Zacny

In Situ Freeze-Capturing of Fracture Water using Cryogenic Coring
Techniques for sampling in situ water from unsaturated fractures in low-moisture environments are lacking. Laboratory experiments demonstrate that cryogenic coring is a promising technique for freezing and collecting water in unsaturated fractures.
Vadose Zone J 2004 3: 1479-1482. [Abstract] [Full Text] [Figures Only] [PDF]  

A. G. Hunt

Comparing van Genuchten and Percolation Theoretical Formulations of the Hydraulic Properties of Unsaturated Media
The van Genuchten functions for hydraulic properties of unsaturated porous media are structurally similar to results obtained using percolation theory. The similarities allow an analysis of the van Genuchten phenomenology. Conditions under which the arguments of the functions are accurate are identified.
Vadose Zone J 2004 3: 1483-1488. [Abstract] [Full Text] [Figures Only] [PDF]  

BOOK REVIEWS:

Warren A. Dick

Landscape Agroecology
Vadose Zone J 2004 3: 1489. [Full Text] [PDF]  

Jon M. Wraith

Soil Water Dynamics.
Vadose Zone J 2004 3: 1490. [Full Text] [PDF]  

ERRATA:

James L. Starr and Dennis J. Timlin

Using High-Resolution Soil Moisture Data to Assess Soil Water Dynamics in the Vadose Zone
Vadose Zone J 2004 3: 1491. [Full Text] [PDF]  

Gerrit H. de Rooij, Roy T. A. Kasteel, Andreas Papritz, and Hannes Flühler

Joint Distributions of the Unsaturated Soil Hydraulic Parameters and their Effect on Other Variates
Vadose Zone J 2004 3: 1492. [Full Text] [PDF]  

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