Dept. of Soil Science and Geology
Czech University of Life Sciences, Pragueand

PC-Progress, Ltd.

The Second HYDRUS Workshop
March 28th 2008
Prague, Czech RepublicCzech University of Life Sciences, Prague
Faculty of Agrobiology, Food and Natural ResourcesKamýcká 129
165 21 Praha 6 – Suchdol
Czech Republic
http://www.af.czu.cz/en/

The Second HYDRUS Workshop
March 28, 2008
Prague, Czech Republic

ProgramTime
08:45-09:00
09:00-09:30

09:30-09:50

09:50-10:10

10:10-10:30
10:30-10:50

Speaker
Registration & Introduction
Jirka Šimůnek
University of California Riverside,
California, USA

Tiago Ramos
Estação Agronómica Nacional,
PortugalValerie Pot
Institut National de la Recherche
Agronomique, Grignon, France

Radka Kodesova
Czech University of Life Sciences,
Czech Republic

Yves Coquet

11:20-11:30

Tineke De Wilde

11:30-11:50

Karlien Cheyns

AgroParisTech, Grignon, France

Ghent University, Belgium

K.U. Leuven, Belgium

Krisztian Szegedi

12:10-12:30
12:30-14:00
14:00-14:20

New features and developments in
HYDRUS software packages.
Multicomponent solute transport intwo multifactorial experiments.
Is the dispersion coefficient ofsorbing tracers modified byretardation? Inverse modeling with
HYDRUS-1D.
Impact of soil micro-morphologicalfeatures on character of water flow
and solute transport.

Break

10:50-11:10

11:50-12:10

Title

UFZ – Helmholtz Centre forEnvironmental Research,Halle/Saale, Germany

Jirka Šimůnek
University of California Riverside,
California, USA

Lunch
Fairouz Slama
Ecole Nationale d’Engenieurs deTunis, Tunisia

2

Sensitivity analysis of HYDRUS-1D
to transient-MIM parameters: a casestudy related to pesticide fate insoils.
Evaluating sorption and degradation
characteristics of pesticides using
column displacement experiments.
Describing pesticide degradation
using Monod kinetics: information
content of batch and column data.
What comes before upscaling? Modeling transport and speciation in
the rhizosphere with the new tool
RhizoMath.
A HYDRUS based Approach for
Coupled Modeling of Vadose Zone
and Ground Water Flow at Different
Scales.
Field data and modeling of salt
transport in a coastal irrigated plain.

14:20-14:40

14:40-15:00

15:00-15:20

Ying Zhao
Christian-Albrechts-University zu
Kiel, Germany

J. Jiménez-Martínez
Technical University of Catalonia,
Barcelona, Spain

Gerrald Matisoff
Case Western Reserve University,
Cleveland, OH

Guenter Langergraber
15:20-15:40

University of Natural Resources andApplied Life Sciences (BOKU),
Vienna, Austria

15:40-16:00

Open

16:00-17:00

Modeling of coupled water and heat
fluxes in both unfrozen and frozen
soils.
HYDRUS-1D Modeling of an
Irrigated Agricultural Plot with
Application to Aquifer Recharge
Estimation.
Downward migration of Chernobylderived radionuclides in soils in
Poland and Sweden.
Overview of applications of the
HYDRUS constructed wetland
module.

Poster presentations, discussions, and

3

Beer!

Presentations: (presenter in bold)
1. Šimůnek, J., M. Šejna, and M. Th. van Genuchten, New features anddevelopments in HYDRUS software packages.
2. Ramos, T. B., M. C. Gonçalves, A. Prazeres, and J. C. Martins, N. L.
Castanheira, Multicomponent solute transport in two multifactorial experiments.
3. Pot, V., P. Benoit, M. Le Menn, O.M. Eklo, T. Sveistrup, J. Kværner, Is thedispersion coefficient of sorbing tracers modified by retardation? Inverse
modeling with HYDRUS-1D.
4. Kodešová, R., M. Kočárek, J. Kozák, V. Kodeš, J. Šimůnek, N. Vignozzi, and
M. Pagliai, Impact of soil micro-morphological features on character of waterflow and solute transport.
5. Cheviron B. and Y. Coquet, and, Sensitivity analysis of HYDRUS-1D totransient-MIM parameters: a case study related to pesticide fate in soils.
6. De Wilde, T., J. Mertens, J. Šimůnek, K. Sniegowksi, P. Spanoghe, J.
Ryckeboer, P. Jaeken, and D. Springael, Evaluating sorption and degradation
characteristics of pesticides using column displacement experiments.
7. Cheyns, K., J. Mertens, E. Smolders, and D. Springael, Describing pesticidedegradation using Monod kinetics: information content of batch and column
data.
8. Szegedi, K., D. Vetterlein, R. Jahn, H.-U. Neue, What comes before upscaling?
- Modeling transport and speciation in the rhizosphere with the new tool
RhizoMath.
9. Twarakavi, N. K. C., J. Šimůnek, and S. Seo, A HYDRUS based approach forcoupled modeling of vadose zone and ground water flow at different scales.
10. Slama, F., R. Bouhlila, and J. Tarhouni, Field data and modeling of salt
transport in a coastal irrigated plain.
11. Zhao, Y., S. Peth, and R. Horn, Modeling of coupled water and heat fluxes inboth unfrozen and frozen soils.
12. Jiménez-Martínez, J., T.H. Skaggs, M.Th. van Genuchten, L. Candela,
HYDRUS-1D Modeling of an Irrigated Agricultural Plot with Application to
Aquifer Recharge Estimation.
13. Matisoff, G., L. Vitko, P. Whiting, M. Ketterer, J. W. Mietelski, E. Lokas, K.
Rosen, H. Persson, Downward migration of Chernobyl-derived radionuclides insoils in Poland and Sweden.
14. Langergraber, G., Overview of applications of the HYDRUS constructedwetland module.

4

Posters:
15. Jakimavičiūtė-Maselienė, V., J. Mažeika, Ž. Skuratovič, Water flow in the
different types of unsaturated soils in Lithuania (poster).
16. Jacques, D., J. Šimůnek, D. Mallants, and M. Th. van Genuchten, Simulation of
the effect of time-variable water flow on the speciation and mobility of reactive
elements in soil (poster).
17. Barão, A. L. B., Pedro Chambel Leitão, Ramiro J.Neves, Maria Conceição
Gonçalves, Tiago B. Ramos, Nádia Castanheira, Simulation of water dynamics
in two irrigated soils.
Other contributions:18. Sakai, M., J. Šimůnek, and H. Saito, Evaluating Evapotranspiration from
Meteorological Data Using HYDRUS-1D.

5

New Features and New Developments in HYDRUS Software
PackagesJ. Šimůnek
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA

M. Šejna
PC-Progress, s.r.o., Anglicka 28, Prague 120 00, Czech Republic

M. Th. van Genuchten
U.S. Salinity Laboratory, USDA, ARS, Riverside, CA 92507, USA

ABSTRACT:The first HYDRUS workshop was held on October 19, 2005 at the Department of Earth
Sciences of the Utrecht University in Utrecht, the Netherlands. Two major
developments related to HYDRUS software packages have occurred since then. The
main development undoubtedly was the replacement of HYDRUS-2D with HYDRUS(2D/3D) in 2006. The HYDRUS (2D/3D) software package is an extension andreplacement of HYDRUS-2D and SWMS_3D. This software package is a complete
rewrite of HYDRUS-2D and its extensions for two- and three-dimensional geometries.
The second major development was the release of the new version (4.0) of HYDRUS1D in 2008. In addition to many new features, GUIs of HYDRUS-1D and HYDRUS(2D/3D) support also the biogeochemical flow and transport model HP1 and theconstructed wetland module CW2D, respectively. Both software packages represent
major upgrades of previous versions, with many new processes considered and withsignificantly improved graphical user interfaces and more detailed online helps.
Additionally, HYDRUS-1D was significantly simplified and incorporated as the
HYDRUS package into the groundwater flow model MODFLOW.

6

Multicomponent Solute Transport in Two Multifactorial
Experiments
T. B. Ramos, M. C. Gonçalves, A. Prazeres & J. C. Martins
Department of Soil Science, Estação Agronómica Nacional, Oeiras, Portugal

N. L. Castanheira
Department of Rural Engineering, University of Évora, Portugal

ABSTRACT:In this study we use HYDRUS-1D to analyze multicomponent solute transport in two
soils with medium and coarse textures, under field conditions, in a three year
experiment, at three depths (20, 40 and 60 cm). A triple emitter source irrigation system
was used for water, salt and nitrogen application. With this system it is intended toobtain two gradients, one for the fertilizer and the other for salinity, and to observe its
effects on soil and culture. HYDRUS-1D successfully predicted field measurements of
the water content (R2>0.96; b>0.86), overall salinity (R2>0.71; b<1.17), and theconcentration of soluble Na+ (R2>0.71; b>0.91). The correspondence between measured
and simulated values for soluble Ca2+ and Mg2+ was lower (R2>0.571; b<1.61),
affecting the predictions of the sodium adsorption ratio (R2>0.72; b>0.61). The
exchangeable sodium percentage presented the poorest relation between measured andsimulated values (R2>0.34; b<1.50). The simulations resulted in a closer
correspondence in the medium texture soil.

7

Is the dispersion coefficient of sorbing tracers modified bysorption? Inverse modeling with HYDRUS-1D.
V. Pot, P. Benoit, M. Le Menn,
UMR INRA AgroParisTech, Environment and Arable Crops, F-7885,Thiverval-Grignon, France

O.M. Eklo,
Bioforsk – Norwegian Institute for Agricultural and Environment Research, Plant health and Plant
Protection Division, Høgskoleveien 7, N-1432 Ås, Norway

T. Sveistrup, J. Kværner
Bioforsk – Norwegian Institute for Agricultural and Environment Research, Soil and Environment
Division, Frederic A. Dahls vei 20, N-1432 Ås, Norway

ABSTRACT:The mobility of pesticides in soils is mainly affected by the water flow patterns,
sorption and degradation. Prediction of pesticides dissipation in the field requires
reliable values of key transport parameters describing dispersion, sorption anddegradation. Dispersion is a key process describing spreading of solutes. Transport ofnon-sorbing tracer is usually correctly described by the convection dispersion equation(CDE), in the absence of physical non-equilibrium transport processes. Transport ofsorbing tracers is further described by an additional source/sink term to the CDE. In thecase of viscous Poiseuille flow in cylindrical tubes and parallel plates, Taylor and Aris
explained the hydrodynamic dispersion of non sorbing tracer in the longitudinal
direction as a combined effect of molecular diffusion in the liquid phase and velocity
variations with the radius (thickness) of the tube (parallel plate). Aris (1959) further
demonstrated that retardation (equilibrium sorption) does affect the value of thedispersion coefficient and increases it as compared to non-sorbing solute in the case of
cylindrical pores. This phenomenon is named Fickian sorption-enhanced dispersion.
However, in the framework of the convection dispersion equation (CDE), using aneffective dispersion coefficient is generally considered as the indication of nonequilibrium transport processes. In this work, we attempted to evaluate the presence of
Fickian sorption-enhanced dispersion in the complicated geometry of soil pore space as
opposed to effective dispersion. To do so, Fickian sorption-enhanced dispersion andnon-equilibrium two-site sorption were evaluated to describe metribuzin transport inundisturbed soil cores sampled in the A, B and C horizons of a sandy loam soil. Inverse
modelling of the water tracer (bromide) and metribuzin breakthrough curves (BTCs)
was performed in the framework of the CDE, with HYDRUS-1D. This study suggeststhat Fickian sorption-enhanced dispersion and non-equilibrium two-site sorption both
occurred during the transport of metribuzin in the A and B horizons of Grue soil.
Metribuzin fate during transport in the C horizon was correctly described only by
Fickian sorption-enhanced dispersion. However, other non-equilibrium processes (e.g.
intraparticle diffusion) not included in the models we used may also result in higher
effective dispersion. We emphasize that more theoretical and modelling studies areneeded to elucidate the potential dependency relation of a Fickian form between
dispersion and retardation in porous medium.

8

Impact of soil micro-morphological features on character of waterflow and solute transport
R. Kodešová, M. Kočárek, J. Kozák
Department of Soil Science and Geology, University of Life Sciences, Kamýcká 129, 16521 Prague 6,
Czech Republic

V. KodešDepartment of Water Quality, Czech Hydrometeorological Institute, Na Šabatce 17, 14306 Prague 6,
Czech Republic

J. Šimůnek
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA

N. Vignozzi, M. Pagliai
CRA-ABP, Piazza M Azeglio 30, I-50121 Florence, Italy

ABSTRACT:
Soil pore structure and water flow and chlorotoluron transport were studied in humic
horizons of various soil types: Haplic Luvisol, Greyic Phaeozem, Haplic Cambisol.
Single-porosity, and either dual-porosity or dual-permeability, flow and transportmodels in HYDRUS-1D were used to estimate the soil hydraulic parameters fromlaboratory multi-step outflow experiments, laboratory and field ponding infiltration
experiments via numerical inversion. Appropriate models were selected based on thesoil micromorphological study. Herbicide (chlorotoluronu) transport parameters were
measured using a standard laboratory procedure and some of them were estimated using
numerical inversion from to transient data obtained from laboratory ponding infiltration
experiments. Resulting parameters were used to simulate the herbicide transport
experimentally studied in the field.

9Sensitivity Analysis of HYDRUS-1D to transient-MIM
parameters: a case study related to pesticide fate in soil
B. Cheviron§, Y. Coquet
UMR 1091 INRA / AgroParisTech Environment and Arable Crops, BP 01, 78850 Thiverval-Grignon,
France§currently at UMR 1221 INRA/IRD/ Montpellier SupAgro LISAH, 2 place Viala, 34060 Montpellier cedex
1, France

ABSTRACT:The quality of groundwater resources in Europe is largely degraded due to contamination by
agricultural pesticides. France is no exception, and one of its main groundwater resources, theBeauce aquifer (20 billions m3 capacity) is contaminated by a variety of molecules (atrazine,
isoproturon, chlortoluron, bentazone, fluroxypyr). A research project supported by the French
Ministry for Ecology and Sustainable Development had for main objective the understanding of theprocesses at the origin of Beauce groundwater contamination by pesticides. Preliminary work on
solute transport in Beauce loamy soils had shown that preferential flow through macropores(earthworms, root channels) was ineffective due to the high hydraulic conductivity of the soil
matrix. However, flow rates of conservative inert tracers (bromide anion) were not consistent witha movement of all the water contained in the soil. Experiments demonstrated the existence of a“mobile/immobile water” (MIM)-type of transport in Beauce soils. These soils are characterized bya large immobile water fraction, of the order of 50 % of the soil water content when close tosaturation. This process may lead to a larger solute flow rate than if all the soil water wasparticipating to solute flow. In consequence, the MIM flow process has to be accounted for inmodelling the risk of pesticide leaching to groundwater in the Beauce region.
We evaluated version 3.0 of HYDRUS-1D for the capacity of simulating isoproturon transport insoil under transient MIM flow. We present a one-parameter-at-a-time sensitivity analysis of
HYDRUS-1D based on 3 base case scenarios corresponding to three soil profiles, for which acomprehensive set of pesticide fate parameters were available, including MIM parameters. Twoways of modelling transient MIM flow are proposed in HYDRUS-1D according to how waterexchange between the mobile and the immobile regions is modelled. This exchange may bedescribed as a function of the difference in effective saturation (Se) between the two regions, or as afunction of their difference in water potential (h). We chose to use to Se -based formulation, which
requires 9 parameters, instead of 11 for the h-base formulation: θm,r [-], θm,s [-], α [L-1], n [-],
Ks [L T-1], l [-], which are the Mualem-van Genuchten hydraulic parameters of the mobile
region, θim,r [-], θim,s [-], which are the parameters of the effective saturation in the immobile
region, and ω [T-1], which is the first-order water transfer rate between the mobile and theimmobile regions. Pesticide transport is described by the convection-dispersion equation,
including a first-order solute exchange term, β [T-1], accounting for solute diffusion between themobile and immobile regions. Pesticide sorption was considered to follow a linear isotherm, andpesticide degradation, first-order kinetics. The HYDRUS-1D code was specially modified to
implement temperature dependence of degradation rates according to Walker’s equation, whichstates that degradation rate is a power function of water content. For the 3 soil profiles, each soil
horizon was characterized by hydraulic, MIM and pesticide fate parameters that were estimatedby independent measurements, except parameter ω that was taken from Köhne et al. (2004).
The sensitivity analyses were performed using the SENSAN software and were based on the
maximum instantaneous and annually-averaged concentration in soil solution at 1 m depth.
The most sensitive parameters for the three soil profiles were MIM parameters θm,s and θim,s,the van Genuchten shape parameter n and, more classically, pesticide sorption coefficient anddegradation rate. The high sensitivity of pesticide concentration to MIM parameters pleads forthe inclusion of transient MIM processes in pesticide fate models.

10

Evaluating sorption and degradation characteristics of pesticides
using column displacement experiments
T. De Wilde1, J. Mertens2, J. Šimůnek3, K. Sniegowski2, P. Spanoghe1, J. Ryckeboer2,
D. Springael3
1

Laboratory of Crop Protection Chemistry, Ghent University, Coupure Links 653, B-9000 Ghent,
Belgium,
2

Division Soil and Water Management, K.U. Leuven, Kasteelpark Arenberg 20, B-3001 Heverlee,
Belgium and3

Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA

ABSTRACT:HYDRUS-1D was applied to analyze breakthrough curves (BTCs) generated in column
displacement experiments. These column displacement experiments represent small
scale biopurificiation systems to treat pesticide contaminated water. Pesticides wereretained and degraded inside the column. For certain pesticides (i.e. metalaxyl),
degradation was not a first-order process, therefore the convection-dispersion equation
was augmented with the Monod type kinetics.

11

Describing pesticide degradation using Monod kinetics:
information from batch and column data
Cheyns1, K., J. Mertens1, J. Šimunek2, E. Smolders1 and D. Springael1
1 Division soil- and water management, KULeuven, Arenbergpark 20, 3001 Heverlee, Belgium
2 Department of Environmental Sciences, University of California Riverside, Riverside, CA, USA

ABSTRACT
Degradation and sorption characteristics of pesticides are crucial to quantify theirtransport through the unsaturated zone towards the groundwater. The parameters needed
for the mathematical description of both processes are usually estimated fromlaboratory batch or column experiments and thereafter incorporated in larger scalemodels. This study evaluates the use of batch mineralization as well as pesticideleaching data through columns for the estimation of the parameters needed for thedescription of both pesticide sorption and degradation.
Pesticide degradation in field or catchment scale modelling is commonly describedusing a first-order approach. However, this first order approach is in contrast with what
is often seen in laboratory mineralization experiments where a lag phase (ie. period
during which no degradation occurs) is commonly observed. Since in both the batchmineralization experiment and the column experiment of this study, a lag phase isnoticed, a first order approximation of the Monod kinetics is used to describe thekinetics. With respect to the sorption kinetics of the pesticide to the soil matrix, linear
equilibrium sorption is assumed.
This study uses the Shuffled Complex Evolution Metropolis (SCEM) algorithm toidentify the model parameters and their associated uncertainty. The study’s objectives
are to compare the optimized model parameter distributions when optimized against (a)only batch mineralization data (b) only column leachate data and (c) to investigate thesuitability of the optimized batch parameters to predict the observed column leachatedata.
The model used in this experiment was able to describe the mineralization ofatrazine in batch well. Similarly, Hydrus-1D simulated the observed breakthrough ofatrazine through the soil columns well. Both use the Monod kinetics to describe thedegradation of atrazine. It is shown however that predicting atrazine breakthroughthrough columns using optimized batch parameter growth rate and initial biomass
concentration is not possible! The study demonstrates that care should be taken when
upscaling pesticide degradation kinetics measured in batch to larger scales (ie. columns
or field scale).

12What comes before upscaling? - Modeling transport andspeciation in the rhizosphere with the new tool RhizoMath
K. Szegedi, D. Vetterlein & H.-U. Neue
Department of Soil Physics, UFZ – Helmholtz Centre for Environmental Research, Halle/Saale, Germany
Institute of Agricultural and Nutritional Sciences, Martin Luther Univ. Halle-Wittenberg, Halle, Germany

R . Jahn
Institute of Agricultural and Nutritional Sciences, Martin Luther Univ. Halle-Wittenberg, Halle, Germany

ABSTRACT:
Plants are one of the "principal performers" in the vadose zone as their activity induces
or influences water flow and solute transport in the soil. The most striking feature of therhizosphere is the formation of solute gradients extending from the root surface into thesurrounding soil that occur as depletion and accumulation of solutes at the root surface,
as well as gradients in the soil pH-value. The root uptake rate of a given nutrient isprimarily a function of its concentration in the soil solution at the root surface that
depends on the combined effects of many plant and soil processes and differs from theconcentration in the bulk soil. Understanding the processes that occur in the vicinity ofroots is also essential for modeling transport at larger scales. The RhizoMath (Szegedi
et al, 2008) approach for modeling co-occurring processes in the rhizosphere, including
speciation in the soil solution, is based on coupling the mathematical package
MATLAB with the geochemical code PHREEQC (Parkhurst & Appelo, 1999).
Different geochemical models (with and without charge balance) and geometries(planar and radial) are included and a built-in initialization module performs calibration
against experimental data. RhizoMath was applied to describe a compartment system
experiment involving a complex speciation with a special emphasis on the interactionsof arsenate and phosphate with the soil substrate. RhizoMath is able to describe
concentration gradients found in experiments (Vetterlein et al. 2007). However, a moresophisticated plant response mode still has to be included.

REFERENCES
Szegedi, K., Vetterlein, D., Nietfeld, H., Jahn, R. & Neue, H.-U. 2008. The New Tool RhizoMath forModeling Coupled Transport and Speciation in the Rhizosphere, Vadose Zone Journal, Special Issue“Vadose Zone Modeling”. In press. DOI: 10.2136/vzj2007.0064.
Parkhurst, D.L. & Appelo, C. A. J. 1999. User's guide to PHREEQC (version 2) - A computer program forspeciation, batch-reaction, one-dimensional transport, and inverse geochemical calculations. USGS WaterResources Investigations Report 99-4259, Denver, Colorado.
Vetterlein, D., Szegedi, K., Ackermann, J., Mattusch, J., Neue, H.-U., Tanneberg H. & Jahn, R. 2007.
Competitive mobilisation of phosphate and arsenate associated with goethite by root activity. Journal ofEnvironmental Quality 36, 1811-1820.

13

A HYDRUS based Approach for Coupled Modeling of Vadose
Zone and Ground Water Flow at Different Scales
Navin K. C. Twarakavi & J. Šimůnek
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA

S. SeoColorado School of Mines, 1500 Illinois St., Golden, CO 80401

ABSTRACT:In the past, ground water flow modeling has been done with little or no consideration of
the effects of vadose zone processes. This dramatic simplification and neglect of theeffects of vadose zone processes have been utilized owing to constraints on
computational resources. Another reason for such a simplification is to work around therelatively high non-linearity of vadose zone flow compared to ground water. While such
simplified representation of vadose zone flow processes leads to faster modelingsimulations, it also leads to a poor characterization of groundwater fluxes in the area
under consideration. Ideally, one would prefer to strike a balance between the modelingefficiency and the computational demand of the adopted approach. In this paper, a onedimensional unsaturated flow package HYDRUS, recently developed for the threedimensional modular finite-difference ground water model MODFLOW, is evaluatedand compared to other modeling approaches accounting for fluxes through the vadosezone. The HYDRUS package for MODFLOW consists of two sub-models that interact
in space and time- (a) HYDRUS sub-model (vadose zone) and (b) MODFLOW submodel (ground water). The HYDRUS package is based on the HYDRUS-1D programthat solves the one-dimensional Richards equation simulating water movement in thevadose zone. The HYDRUS package considers the main processes and factors affecting
fluxes in the vadose zone, such as precipitation, infiltration, evaporation, redistribution,
capillary rise, plant water uptake, water accumulation at the ground surface, surface
runoff, and soil moisture storage Being fully incorporated into the MODFLOW program,the HYDRUS package provides MODFLOW with recharge fluxes into groundwater,while MODFLOW provides HYDRUS with the position of the groundwater table that isused as the bottom boundary condition in the package. The performance of the
HYDRUS package is analyzed for various case studies that involve different spatial andtemporal scales.

14Field data and modeling of salt transport in a coastal irrigatedplain.

F. SLAMA1,2, R. Bouhlila1 & J. Tarhouni3
1 Laboratoire de Modélisation en Hydraulique et Environnement, Ecole Nationale d’Ingénieurs de Tunis, BP 37 Le
Belvédère 1002, Tunis, Tunisia
fairouz.slama@unine.ch
2 Centre of Hydrogeology (CHY), University of Neuchâtel,. 11, rue Emile-Argand. CH – 2007, Neuchâtel, Switzerland
3 Institut National Agronomique de Tunisie (INAT), 43, Avenue Charles Nicolle 1082 -Tunis- Mahrajène Tunisia

ABSTRACT
Groundwater and soil resources are being threatened by important degradation due tosalinisation processes. This is truer in the case of regions lacking for water resources andcharacterized by arid and semi-arid climate with annual precipitation that does not exceed
500 mm and with important evapotranspiration reaching annual value of 1100 mm. Thissituation, also aggravated by irrigation expansion, leads to overexploiting water
resources. Earlier researches have been performed to study soil and groundwatersalinisation processes. However, in most studies, the unsaturated zone is assimilated to
the root zone not exceeding 2 meters. Moreover groundwater and soil are in most cases
treated separately. In this study, we propose to model both groundwater and soil salinity
in the purpose of understanding and predicting these processes.
Soil samples were taken from three drip irrigated plots in Korba coastal aquifer in
Tunisia at two periods of the year: summer (after irrigation has ended) and winterseasons. Irrigation water comes from groundwater pumping and presents a high electricalconductivity reaching 9 mS/cm in summer. Experiment involved soil sampling of
unsaturated zone reaching 15 m deep. Soil samples were used to determine vertical soil
salinity profiles on extractions from saturated soil paste. Electrical conductivity andmajor ions were also determined for groundwater samples.
HYDRUS1D was used to carry out preliminary simulations of vertical soil salinity andimpacts on groundwater salinisation. Simulations were first performed for a cycle
corresponding to the irrigation season and second for some years.
Experimental data showed salt accumulation in the surface reaching 16 mS/cm.
HYDRUS1D also simulated surface salinisation during the irrigation season. Impacts on
groundwater quality are rather visible after some years of simulation
Key words Irrigation, HYDRUS1D, salinity, evaporation; precipitation, unsaturated zone

15Modeling of Coupled Water and Heat Fluxes in both Unfrozen andFrozen Soils
Y. Zhao, S. Peth & R. Horn
Institute of Plant Nutrition and Soil Science, Christian-Albrechts-University zu Kiel, Olshausenstr. 40,
24118 Kiel, Germany.

ABSTRACT:
Accurate simulation of soil freezing and thawing behavior is critical to understandhydraulic processes in the vadose zone under cold and arid climatic conditions. Using an
extended freezing code incorporated in the HYDRUS-1D model, this study was
conducted 1) to verify the freezing model using field soil water and temperature datacollected in Inner Mongolia grassland, and 2) to investigate the contribution of snowmelt
or soil thawing to the seasonal water balance. The results showed that both the freezing
model and the snow routine matched well the measured soil water and temperature underunfrozen conditions. However, under frozen conditions, the freezing model reflected thephase change of soil water and substantially improved the simulation results than thesnow routine. The freezing model did obviously not produce surface runoff generated bysnowmelt or soil thawing from frozen soil layers. Instead, it overestimated water content
and thus underestimated surface runoff after spring snowmelt. We suggest that a detailed
knowledge of the soil-atmosphere processes is needed to improve the surface runoff
algorithm in the frozen soil module.

16

HYDRUS-1D Modeling of an Irrigated Agricultural Plot with
Application to Aquifer Recharge Estimation
J. Jiménez-Martínez
Department of Geotechnical Engineering and Geosciences, Technical University of Catalonia, UPC,
Barcelona, Spain

T.H. Skaggs
U.S. Salinity Laboratory, USDA-ARS, Riverside, CA, USA

M.Th. van Genuchten
U.S. Salinity Laboratory, USDA-ARS, Riverside, CA, USA

L. Candela
Department of Geotechnical Engineering and Geosciences, Technical University of Catalonia, UPC,
Barcelona, Spain

ABSTRACT:A variety of methods are available for estimating aquifer recharge in semi-arid regions,each with advantages and disadvantages. We are investigating a procedure for estimating
recharge in an irrigated basin. The method involves computing irrigation return flows
based on HYDRUS-1D modeling of root zone and surface boundary water dynamics. In
this paper, we demonstrate the modeling approach and the calibration of the model toexperimental data.

17

Water flow in the different types of unsaturated soils in Lithuania
Jakimavičiūtė-Maselienė V.1, 2, Mažeika J.1, Skuratovič Ž.1
1

Institute of Geology and Geography, T. Ševčenkos str. 13, LT-03223 Vilnius, Lithuania

2

Vilnius Gediminas Technical University, Saulėtekio al. 11, LT-10223 Vilnius, Lithuania

ABSTRACT:
Two in previous monitoring programs experimentally characterized sites were selected
for the water flow simulation in unsaturated zone in Lithuania. The simulations weredone with the finite element code HYDRUS-1D. Infiltration peculiarities in terms ofpressure head and water content versus depth were compared.

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Downward Migration of Chernobyl-derived Radionuclides in Soils
in Poland and Sweden
Gerald Matisoff, Lauren Vitko, Peter Whiting
Case Western Reserve University, Cleveland OH 44106-7216 USA

Michael Ketterer
Northern Arizona University, Flagstaff AZ 86011-5698 USA

Jerzy W. Mietelski, Edyta Lokas
The Henryk Niewodniczanski Institute of Nuclear Physics, Krakow Poland

Klas Rosen, Henning Persson
Swedish University of Agricultural Sciences, Uppsala, Sweden

ABSTRACTThe Chernobyl accident on April 26, 1986 resulted in significant fallout of radionuclides such as
137
Cs and 239,240Pu on surface soils throughout northern Europe. Knowledge of the dynamics andmechanisms of the migration of these radionuclides in soils is important for determining animaland human dose exposure rates, determining exposure from food-chain transfer, and in planningenvironmental remediation and clean-up. In addition, both natural (7Be, 210Pbxs) andanthropogenic (137Cs, 239,240Pu) fallout radionuclides have been extensively employed todetermine short-term soil erosion rates, to trace sediment source regions, to characterize andquantify erosion mechanisms, to constrain sediment budgets, and to better understand the delivery
ratios, transit distance and transit time of fine sediment and adsorbed pollutants. Despite the useof these radionuclides and their activity-depth profiles, little is known about how the profile
shapes develop or why they differ with location. Presented here are soil profiles of 137Cs, 210Pbxs
and 239,240Pu from the Lazy, Tulowice and Bor za Lasem sites in Poland and the Hille andSkogsvallen sites in Sweden so that the profiles of these nuclides may be compared with thoseobtained previously to better understand the downward migration.
Preliminary calculations using the model CHAIN to illustrate the nature of solute migration
in a soil profile and how model simulations can provide insight to the key processes governingtransport reveals three major differences between the observed data and the modeled profiles: 1)
the short-lived cosmogenic radionuclide 7Be is transported deeper than the model simulations
would suggest; 2) some of the 137Cs and 239,240Pu have been retained in the top portion of the core
whereas the model predicts that these radionuclides will be transported downcore as a pulse; and3) 210Pb activities decrease more rapidly near the surface than the model would predict. Future
work will involve additional modeling using the program HYDRUS-1D which should permit
exploring the causes for these differences to refine our ability to describe the transport ofradionuclides in soils, for example, by permitting the use of nonlinear adsorption or by defining
soil properties into multiple depth zones.
There is a substantial amount of information that is embedded in the distribution ofradionuclides with depth that may be extracted to refine our ability to understand significant
radiochemical behavior, to predict dose exposure rates, to better plan environmental remediation,
to use these and other radionuclides to understand soil erosion mechanisms, to identify sedimentsource areas and to calculate watershed inventories and residence times for better understandingof watershed retention and erosion processes. Moreover, ignoring this evidence may lead to a realrisk of drawing incorrect conclusions from an incomplete understanding of the radionuclide
profiles.

19Overview of applications of the HYDRUS constructed wetland
moduleG. LangergraberInstitute of Sanitary Engineering and Water Pollution Control, University of Natural Resources andApplied Life Sciences (BOKU), Muthgasse 18, A-1190 Vienna, Austria.

ABSTRACT:The multi-component reactive transport module CW2D was developed to model transportand reactions of the main constituents of municipal wastewater in subsurface flow
constructed wetlands and is incorporated into the HYDRUS variably-saturated water flow
and solute transport program. CW2D is able to describe the biochemical elimination andthe transformation processes for organic matter, nitrogen and phosphorus and considers
12 components (solutes) and 9 processes (reactions). This paper intends to give an
overview of applications of the CW2D module that differ in terms of the type of theconstructed wetland investigated, the size of the system as well as in the type ofwastewater treated.

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Simulation of the effect of time-variable water flow on thespeciation and mobility of reactive elements in the soil
D. Jacques & D. Mallants
Institute for Environment, Health and Safety, Belgian Nuclear Centre (SCK•CEN), Boeretang 200, B-2400
Mol, Belgium

J. Šimůnek
Department of Environmental Sciences, University of California Riverside, Riverside, CA 92521, USA

M. Th. van Genuchten
U.S. Salinity Laboratory, USDA, ARS, 450 W. Big Spring Rd., Riverside, CA 92507, USA

ABSTRACT:Speciation of elements determines their mobility. It depends on the geochemical
conditions in the soil. The latter is influenced by the water content and the water fluxes.
This is numerically investigated using the reactive coupled simulator HP1 resulting fromcoupling HYDRUS-1D to the geochemical code PHREEQC-2.15. Two examples
illustrate the effect of time variably water flow on the speciation and mobility of elements,
both on the short term (seasonal variations) as on the long term leaching to thegroundwater.

21

Evaluating Evapotranspiration from Meteorological Data Using
HYDRUS-1D
Masaru Sakai & Jirka Šimůnek
Department of Environmental Sciences, University of California Riverside, Riverside, CA

Hirotaka Saito
Department of Ecoregion Science, Tokyo University of Agriculture and Technology, Tokyo, Japan

ABSTRACT:
Evapotranspiration rates strongly affect movement of water and solute in the vadose zone.
We have implemented into the HYDRUS-1D code Penman-Monteith and Hargreaves
equations to estimate potential evapotranspiration rate. While Penman-Monteith equation
requires information about net radiation, wind speed, minimum and maximum
temperatures and relative humidity, Hargreaves equation requires only minimum andmaximum temperatures. The developed code provides users with a lot of flexibility byallowing an input of various combinations of meteorological information. The
performance of the code is demonstrated using meteorological data for Tokyo, Japan(humid climate) and Riverside, CA (semi-arid climate). Liquid water and water vapor
flow, heat transport, root water uptake, and evapotranspiration rates were quantitatively
evaluated using meteorological data publicly available from local weather stations.

22

Simulation of water dynamics in two irrigated soils
Lúcia Barão, Pedro Chambel Leitão, Ramiro J.Neves, Maria Conceição Gonçalves, Tiago
B. Ramos, Nádia Castanheira
Department of Soil Science, Estação Agronómica Nacional, Oeiras, Portugal

ABSTRACT:In this present work three models were used to simulate the water content distribution in
the several soil horizons during seven years (2001-2007): Hydrus, RZWQM (Root Zone
Water Quality Model) and MohidLand. The aim of the work is to show that different
models with different modelling approaches reach the same results and that thecomparisons with the data field also validate the results.
The Hydrus and the MohidLand model used the van Genuchten parameters for thehydraulic curves, while in the RZWQM model the parameters used were the modified
Brooks and Corey. The main difference between Hydrus and MohidLand is the use of
the finite elements instead of finite volumes, respectively. Potential evapotranspiration is
calculated by the RZWQM model through the atmospheric data and was used as an input
for Hydrus and MohidLand. To evaluate the partition between transpiration andevaporation during the simulation, the results of LAI (Leaf Area Index) from RZWQM
previously validated with data fields, were also used.
The simulations were done for two different soil types: Hortic Anthrosol and Eutric
Fluviosol which have different hydraulic properties and textures, in order to observe thedifferent behavior of water distribution in the soil. These soils are located in AlentejoPortugal where irrigation has a very important contribution for the water management inagriculture.

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