Czech University of Life Sciences Pragueand

PC-Progress, s.r.o., Prague

5th International Conference
HYDRUS Software Applications to Subsurface Flow
and Contaminant Transport Problems
March 30-31 2017
Prague, Czech RepublicCzech University of Life Sciences Prague
Faculty of Agrobiology, Food and Natural ResourcesKamýcká 129
165 00 Praha 6 – Suchdol
Czech Republic
http://www.af.czu.cz/en/
PC-Progress s.r.o.
Korunní 2569/108a
Prague, 101 00
Czech Republic
http://www.pc-progress.com/en/Default.aspx

ISBN: 978-80-213-2749-8

Preliminary Program
Thursday, March 30, Morning session:

Variably-Saturated Water Flow and Transport of ContaminantsTime

Authors and Title

8:20-8:50

Arrival, registration

8:50-9:00

Radka Kodešová and Rien van Genuchten (presiding): Opening remarks

9:00-9:30

Keynote Presentation: Jirka Šimůnek
Šimůnek, J., M. Th. van Genuchten, D. Jacques, and M. Šejna, Recent
developments and applications of the HYDRUS software packages.

9:30-9:50

Batalha, M. S., E. M. Pontedeiro, and M. Th. van Genuchten, Groundwater
recharge calculations as affected by temporal averaging of meteorological
data. (Brazil)

9:50-10:10

Szymkiewicz, A., J. Šimůnek, A. Gumuła-Kawęcka, S. Beegum, B.
Leterme, B. Jaworska-Szulc, M. Pruszkowska Caceres, W. GorczewskaLangner, R. Angulo-Jaramillo, and D. Jacques, Development and evaluationof the Hydrus package for Modflow. (Poland)

10:1010:30

Liang, J., S. A. Bradford, J. Šimůnek, and A. Hartmann, Modeling nonequilibrium overland flow and transport processes using HYDRUS-1D.
(USA)
Coffee Break

11:0011:30

Keynote Presentation: Giuseppe Brunetti
Brunetti, G., and J. Šimůnek, Selected Applications of HYDRUS Models forEngineering Problems. (Italy and USA)11:3011:50

Turco, M., G. Brunetti, A. Nikodem, M. Fér, R. Kodešová, and P. Piro,
Water flow modeling in the highly permeable pavement using Hydrus-2D.
(Italy and Czechia)

11:5012:10

Berger, K., Comparison and validation of SWMS_2D and HYDRUS(2D/3D) for capillary barriers using data of a 10-m tipping through.
(Germany)

12:1012:30

Suskin, V. V., I. V. Kapyrin, and A. V. Rastorguev, Modeling unsaturated
groundwater flow and transport in the vadose zone using GeRa code.
(Russia)Lunch

3

Thursday, March 30, Afternoon Session:

Irrigation Applications, Roots, and Miscellaneous Topics
Time

Authors and Title

2:00-2:30

Keynote Presentation: Naftali Lazarovitch
Raij, I., G. Bel, and Naftali Lazarovitch, Unveiling multi-dimensional waterflow and solute transport using HYDRUS codes. (Israel)

2:30-2:50

Hartmann, A., J. Šimůnek, M. K. Aidoo, S. J. Seidel, and N. Lazarovitch, A
new HYDRUS add-on module to model the interactions between plant roots,
soil properties, and water flow conditions in soils. (Germany, USA, andIsrael)2:50-3:10

Diamantopoulos, E., M. Walkinshaw, T. O’Geen, and T. Harter, Assessing
nitrate leaching potential in California’s agricultural soils through Hydrus1D simulations. (USA)

3:10-3:30

Glass, J., T. Fichtner, and C. Stefan, Stepwise calibration of hydraulicconductivity changes in a laboratory tank simulating managed aquifer
recharge operation. (Germany)

3:30-3:50

Fér, M., R. Kodešová, A. Nikodem, and A. Klement, Using HYDRUS-1Dfor estimating soil hydraulic parameters from capillary rise and evaporation
rates measured using a clay tank and soil respiration chamber, respectively,
and their correlation with a net CO2 exchange rate. (Czechia)
Coffee Break

4:10-4:40

Lightning Session(3 min presentations of the posters)

4:40-6:00

Poster Session

6:00 - ….

Mixer, Beer Session

4

Friday, March 31 Morning session:

Biogeochemical Transport and Reactions

Time

Authors and Title

9:00-9:30

Keynote Presentation: Günter Langergraber
Langergraber, G., Process-based models for subsurface flow treatment
wetlands: Recent developments and challenges. (Austria)

9:30-9:50

Hochfeldt, V., B. Pucher, and G. Langergraber, Simulating a full-scale twostage vertical flow wetland system using the HYDRUS Wetland Module.
(Austria)

9:50-10:10

Pucher, B., and G. Langergraber, Simulation results using the HYDRUS
Wetland Module for different sized filter medias in vertical flow treatment
wetlands. (Austria)

10:1010:30

Llorens, C., B. Pucher, and G. Langergraber, Determination of parametersdescribing the hydraulic behavior of filter materials for stormwater filters
using HYDRUS. (Austria)
Coffee Break

11:0011:30

Keynote Presentation: Diederik Jacques
Jacques, D., D. Zhou, J. Makselon, I. Engelhardt, and S. Thiele-Bruh,
Colloid and colloid-facilitated transport modeling using HPx. (Belgium andGermany)

11:3011:50

Filipović, V., Y. Coquet, V. Pot, P. Cambier, L. Filipović, S. Houot, and P.
Benoit, Modeling the effect of tillage and urban waste compost addition onwater flow and contaminant (Isoproturon, Cu, Cd) transport in agricultural
field using HYDRUS-2D. (Croatia and France)

11:5012:10

Hlaváčiková, H., V. Novák, J. Šimůnek, L. Holko, Z. Kostka, and M.
Danko, The effects of rock fragment shapes and positions on modeled
hydraulic conductivities of stone soils. (Slovakia)

12:1012:30

Arye, G., and J. Šimůnek, Surface-active root exudates induced flow
phenomena in the rhizosphere: A numerical study. (Israel and USA)
Lunch

5

Friday, March 31: Afternoon Session:

Inverse Problems, Nonequilibrium Flow
Time

Authors and Title

2:00-2:20

Keynote Presentation: Rien van Genuchten
Bezerra Coelho, C. R., L. Zhuang, and M. Th. van Genuchten, Hydrus-1D
tests of the Hyprop evaporation method for estimating the unsaturated soil
hydraulic functions. (Brazil)

2:20-2:40

Sittig, S. Coupling DREAM Suite and PEARL for parameter inference in a
Bayesian framework. (Germany)

2:40-3:00

Khaddam, I., S. Werisch, and N. Schuetze, A modeling-based optimization
framework for reclamation leaching practices. (Germany)

3:00-3:20

Iden, S. C., E. Diamantopoulos, and W. Durner, Capillary, film and vapour
flow during transient evaporation: Inverse simulation of lab experiments
using pressure head and humidity data. (Germany)

3:20-3:40

Šimůnek, J., M. Šejna, and M. Th. van Genuchten, Current developments andapplications of the HYDRUS software packages.
Coffee Break

4:00

Closing Remarks and Departure6

List of Abstracts
Invited Keynote Presentations:
1. Brunetti, G., and J. Šimůnek, Selected Applications of HYDRUS Models forEngineering
Problems.

2.

3.
4.
5.
6.

16
Bezerra Coelho, C. R., L. Zhuang, and M. Th. van Genuchten, Hydrus-1D tests ofthe Hyprop evaporation method for estimating the unsaturated soil hydraulicfunctions.
14
Jacques, D., D. Zhou, J. Makselon, I. Engelhardt, and S. Thiele-Bruh, Colloid andcolloid-facilitated transport modeling using HPx.
28
Langergraber G., Process-based models for subsurface flow treatment wetlands:
Recent developments and challenges.
32
Raij, I., G. Bel, and Naftali Lazarovitch, Unveiling multi-dimensional water flow
and solute transport using HYDRUS codes.
40Šimůnek, J., M. Th. van Genuchten, D. Jacques, and M. Šejna, Recent
developments and applications of the HYDRUS software packages.
41

Oral Presentations:
1. Arye, G., and J. Šimůnek, Surface-active root exudates induced flow phenomenain the rhizosphere: A numerical study.
11
2. Batalha, M. S., E. M. Pontedeiro, and M. Th. van Genuchten, Groundwater
recharge calculations as affected by temporal averaging of meteorological
data.

3.
4.

5.

6.

7.

8.

12
Berger, K., Comparison and validation of SWMS_2D and HYDRUS (2D/3D) for
capillary barriers using data of a 10-m tipping through.
13
Diamantopoulos, E., M. Walkinshaw, T. O’Geen, and T. Harter, Assessing nitrateleaching potential in California’s agricultural soils through Hydrus-1D
simulations.
18
Fér, M., R. Kodešová, A. Nikodem, and A. Klement, Using HYDRUS-1D for
estimating soil hydraulic parameters from capillary rise and evaporation rates
measured using a clay tank and soil respiration chamber, respectively, and theircorrelation with a net CO2 exchange rate.
19
Filipović, V., Y. Coquet, V. Pot, P. Cambier, L. Filipović, S. Houot, and P.
Benoit, Modeling the effect of tillage and urban waste compost addition on waterflow and contaminant (Isoproturon, Cu, Cd) transport in agricultural field using
HYDRUS-2D.
21
Glass, J., T. Fichtner, and C. Stefan, Stepwise calibration of hydraulicconductivity changes in a laboratory tank simulating managed aquifer recharge
operation.
22
Hartmann, A., J. Šimůnek, M. K. Aidoo, S. J. Seidel, and N. Lazarovitch, A new
HYDRUS add-on module to model the interactions between plant roots, soil
properties, and water flow conditions in soils.
247

9. Hlaváčiková, H., V. Novák, J. Šimůnek, L. Holko, Z. Kostka, and M. Danko, The
effects of rock fragment shapes and positions on modeled hydraulic conductivitiesof stone soils.
25
10. Hochfeldt, V., B. Pucher, and G. Langergraber, Simulating a full-scale two-stage
vertical flow wetland system using the HYDRUS Wetland Module.
26
11. Iden, S. C., E. Diamantopoulos, and W. Durner, Capillary, film and vapour flow
during transient evaporation: Inverse simulation of lab experiments using pressure
head and humidity data.
27
12. Khaddam, I., S. Werisch, and N. Schuetze, A modeling-based optimization
framework for reclamation leaching practices.
29
13. Liang, J., S. A. Bradford, J. Šimůnek, and A. Hartmann, Modeling nonequilibrium overland flow and transport processes using HYDRUS-1D.
33
14. Llorens, C., B. Pucher, and G. Langergraber, Determination of parametersdescribing the hydraulic behavior of filter materials for stormwater filters using
HYDRUS.
34
15. Pucher, B., and G. Langergraber, Simulation results using the HYDRUS Wetland
Module for different sized filter medias in vertical flow treatment wetlands.
39
16. Šimůnek, J., M. Th. van Genuchten, and M. Šejna, Current developments in the
HYDRUS software packages.
42
17. Sittig, S. Coupling DREAM Suite and PEARL for parameter inference in a
Bayesian framework.
43
18. Suskin, V. V., I. V. Kapyrin, and A. V. Rastorguev, Modeling unsaturated
groundwater flow and transport in the vadose zone using GeRa code.
44
19. Szymkiewicz, A., J. Šimůnek, A. Gumuła-Kawęcka, S. Beegum, B. Leterme, B.
Jaworska-Szulc, M. Pruszkowska Caceres, W. Gorczewska-Langner, R. AnguloJaramillo, and D. Jacques, Development and evaluation of the Hydrus package for
Modflow.

45

20. Turco, M., G. Brunetti, A. Nikodem, M. Fér, R. Kodešová, and P. Piro, Water
flow modeling in the highly permeable pavement using Hydrus-2D.
46

Poster Presentations:
1. Boas, T., D. Mallants, and J. Šimůnek, Episodic groundwater recharge in the arid
interior of Australia: Multi-model transfer function approach.
15
2. Brunetti,G., J. Šimůnek, T . Wöhling, M. Turco, and P. Piro, A computationallyefficient pseudo-2D model for the numerical analysis of permeable pavements. 17
3. Filipović, V., H. H. Gerke, L. Filipović, and M. Sommer, Simulating subsurface
lateral flow in eroded soils with contrasting horizon properties using HYDRUS20
2D.
4. Goddard, M., C. Mendoza, and M. Hassanizadeh, The movement of groundwaterand dissolved salts through an oil-sand tailings storage facility using Hydrus23
2D.
5. Klement, A., M. Fér, Š. Novotná, A. Nikodem, and R. Kodešová, Using
HYDRUS-1D and 2D for assessing the impact of different root distributions on
simulated root water uptake.
30
6. Kodešová, R., M. Fér, A. Klement, A. Nikodem, D. Teplá, P. Neuberger, and P.
Bureš, Using HYDRUS-1D for simulating water flow and heat transport undervarious surface covers.
31

8

7. Mallants, D., A. Buter, and J. Šimůnek, A coupled HYDRUS-1D - PHREEQC
analysis of major ion geochemistry and trace metal transport in soil leached withcoal seam gas produced water.
35
8. Mallants, D., and J. Šimůnek, Defining safe water quality requirements forsustainable irrigation with coal seam gas produced water.
36
9. Mallants, D., J. Šimůnek, A. Taylor, M. Williams, and R. Kookana, Natural soil
attenuation potential of hydraulic fracturing chemicals and their transformation
products.
37
10. Nikodem, A., R. Kodešová, M. Fér, and A. Klement, Using HYDRUS codes andscaling factors characterizing spatial and temporal variability of soil hydraulicproperties for assessing the impact of soil erosion on soil water hydrology.
38
11. Van den Eertwegh, G.A.P.H., R. P. Bartholomeus, D. G. Cirkel, and K. J. Raat,
Sub-irrigation by controlled drainage systems using treated wwtp water: Field test
and 2D modeling experiments.
47
12. Weiss, T., M. Slavík, and J. Bruthans, Model of near-surface flow in drying
sandstone.
48

9

10

Surface-Active Root Exudates Induced Flow Phenomena in the
Rhizosphere: A Numerical Study
Gilboa Arye1 and Jirka Šimůnek2
1

French Associates Institute for Agriculture and Biotechnology of Drylands, J. Blaustein Institutes for
Desert Research, Ben-Gurion University of the Negev.
2
Department of Environmental Sciences, University of California, Riverside, California, USA.

Plants can extract or alternatively exude water and solutes at their root surface. Therefore,
concentration gradients are expected from the root surface toward the rhizosphere and viceversa. Among root exudates, the mucilage exhibits surface-activity, expressed in considerable
reduction in the surface tension (ST) at the water-air interface. According to the Laplace
equation, for a given water content and a contact angle, a reduction in ST is associated with aproportional reduction in the capillary pressure. Consequently, the hydraulic characteristics ofthe rhizosphere will differ significantly from those of the bulk soil. Furthermore, the spatial
and/or temporal concentration gradient of surface-active root exudates will be expressed in ST
and/or contact angle gradients and, thus, capillary pressure gradients – a moving force forunsaturated water flow - can be induced. The small flow domain of the rhizosphere posed apractical difficulty in experimental studies. Therefore, our modeling effort with HYDRUS will
provide us with a tool to explore the role and a function of surface-active root exudates on
unsaturated water flow between the rhizosphere and the bulk soil.

11Groundwater Recharge Calculations as Affected by Temporal Averagingof Meteorological Data
M. S. Batalha1, E.M. Pontedeiro2,3, and M. Th. van Genuchten3,4
1

Department of Civil Engineering, Federal University of Rio de Janeiro, UFRJ
Rio de Janeiro, Brazil
2
Department of Nuclear Engineering, Federal University of Rio de Janeiro, UFRJ,
Rio de Janeiro, Brazil
3
Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
4
NIDES Interdisciplinary Center for Social Development, Federal University of Rio de Janeiro,
UFRJ, Rio de Janeiro, Brazil

Simulations of water flow rates into and through the near-surface vadose zone can provide
useful estimates of deep drainage and groundwater recharge. Past studies have shown that
results can be very sensitive to the temporal resolution of meteorological data used in thesimulations. In this study we used HYDRUS-1D to quantify the effects of using weatherrelated data of different resolutions (hourly, daily, weekly, monthly and yearly averaged
precipitation and potential evaporation rates) on predictions of groundwater recharge at threesites in Brazil having different climatological conditions: a tropical savanna (the Cerrado), a
humid subtropical area (the temperate south of Brazil), and a very wet tropical area
(Amazonia). Our current analysis was limited to evaporation processes and hence did notconsider any land use effects by ignoring root water uptake. Temporal averaging was found tolead to very different predictions of recharge, with the yearly averaged data always producing
by far the lowest recharge rates. Results were especially sensitive to averaging when applied
to the Cerrado site for which the daily averaged weather data produced up to 9 times therecharge rates obtained with yearly averaged data. The effects at the Cerrado site are due to thevery uneven rainfall distribution over the year involving distinct wet and dry seasons. Longterm averaging can lead to especially poor recharge estimates for coarse-textured soils since
averaging limits deep penetration of moisture in response to precipitation events. Infiltrated
water will then remain in the upper part of the vadose zone and become subject to possible
upward flow and evaporation. Accounting for short-term high-frequency precipitation eventsis also important when estimating surface runoff.

12Comparison and Validation of SWMS_2D and HYDRUS (2D/3D) for
Capillary Barriers Using Data of a 10-m Tipping ThroughKlaus Berger
University of Hamburg, Institute of Soil Science, Allende-Platz 2, 20146 Hamburg, Germany
Capillary barriers, i.e. a fine-grained/porous capillary layer on a coarse-grained/porous capillary block(e.g. made of sand and gravel, resp.) with a sharp, sloped boundary, are a curious soil hydrologicalphenomenon and an interesting alternative component for cover systems of landfills and contaminatedsites. However, little is known on how to dimension capillary barriers and on the effect of their design
parameters like soil-hydrologic parameters, slope and slope length, or inflow into the capillary layer.
Empirical investigations using large lysimeters or tipping troughs are close to reality, but limited to few
parameter values, time-consuming and expensive. Soil hydrologic models could be fast and powerfultools for dimensioning provided they are sufficiently validated for capillary barriers, especially by
output comparisons of model results with measured data.
Water flow and effectiveness of capillary barriers were empirically investigated at the Institute of Soil
Science of the University of Hamburg in a 50 m x 10 m large test field (lysimeter) at the landfill
Hamburg-Georgswerder and in a 10 m long tipping trough (tilt gutter). Measured data of the tipping
trough for one material combination and two slopes (20 % and 4 %, resp.) from periods with stationary
flow were compared to simulation results of SWMS_2D (Vs. 1.1) in 1996 and recently to results of
HYDRUS 2D/3D (Vs. 2.05). The measured data show a typical pattern with no outflow or very small
outflow rates of the capillary block at smaller inflow rates. Beyond a specific inflow rate (that indicatesthe maximum efficiency of the capillary barrier), the water is breaking through the boundary between
capillary layer and capillary block, and most to all of the additional inflow occurs as outflow in thecapillary block.
This measured flow pattern could not be reproduced with SWMS_2D. Four simulation series were runwith different parametrizations, three of them with calibrations considering the heterogeneity of theparameters ks and van-Genuchten α and n. SWMS_2D always showed a smooth increase of the outflow
rates of the capillary layer and the capillary block with increasing inflow rates. Thus, the validation
attempt failed. This failure may be caused by different reasons: measurement errors, errors of the model
including incompleteness and inappropriateness, or inappropriate application of the model. One reason
might be the assumption that the materials are homogeneous in the simulation, what they actually werenot (although they were well sorted). Due to the spatial heterogeneity, the breakthrough of the capillarybarrier may hypothetically occur in fingers. HYDRUS 2D/3D includes the feature ‘stochastic
distribution of scaling factors’ that can be used to consider spatial heterogeneity in simulation.
Therefore, the validation has been retried with HYDRUS 2D/3D with a 2D general geometry.
In a first simulation series to determine the impact of the FE mesh on the results of a particular steadystate (inflow rate), very different outflow rates occurred dependent on the FE mesh (FE size, stretching,refinements). A second series was performed for all steady state periods using that FE mesh from thefirst series with the best match of measured and simulated out flow rates; scaling was not applied. As
SWMS_2D, HYDRUS 2D/3D results show a smooth flow pattern that visually looks closer to themeasured values. However, a statistical deviation measure leads to higher values than for the
SWMS_2D results. A third simulation series was performed using stochastic distribution of scaling
factors with Miller-Miller similitude. The match of simulated and measured outflow rates, however, iseven worse than without scaling. First simulation results using stochastic distribution of independentscaling factors indicate a similar result. Thus, currently the validation attempt for HYDRUS 2D/3D
seems to fail too. Reasons for the mismatch of measured and simulated outflow rates as categorized
above will be discussed.

13Hydrus-1D Tests of the Hyprop Evaporation Method for Estimating theUnsaturated Soil Hydraulic Functions
C. R. Bezerra Coelho1, L. Zhuang2, and M. Th. van Genuchten2,3
1

Department of Civil Engineering, Federal University of Rio de Janeiro, UFRJ,
Rio de Janeiro, Brazil
2
Department of Earth Sciences, Utrecht University, Utrecht, Netherlands
3
NIDES Interdisciplinary Center for Social Development, Federal University of Rio de Janeiro,
UFRJ, Rio de Janeiro, Brazil

Many subsurface water flow and solute transport applications require information about theunsaturated soil hydraulic functions. The evaporation method has long been used to estimate
the drying branches of the hydraulic functions. An increasingly popular version of theevaporation method is the semi-automated Hyprop measurement system (HMS)commercialized by Decagon Devices (Pullman, WA, USA) and UMS AG (München,
Germany). We used Hydrus-1D to test the HMS methodology by generating synthetic
evaporation (sample weight loss) and soil tensiometric measurements assuming applicabilityof the traditional van-Genuchten-Mualem (VG) soil hydraulic functions. HMS analyses of thesynthetic data agreed closely with the original functions for a broad range of soil textures.
Accurate estimates were especially obtained for the water retention curve over the range ofavailable retention input data. We also successfully tested a dual-porosity soil, as well as a
medium with a relatively high VG n parameter value. The latter test gave excellent results forwater retention, but failed for the unsaturated hydraulic conductivity. Our results confirm thatindependent estimates of the saturated hydraulic conductivity should be obtained for very
coarse-textured soils. Overall, the HMS methodology was found to be a very useful addition
to current methods for measuring the unsaturated soil hydraulic properties.

14

Episodic Groundwater Recharge in the Arid Interior of Australia:
Multi-Model Transfer Function Approach
Theresa Boas1, Dirk Mallants2, and Jirka Šimůnek3
1

Steinmann-Institut für Geologie, Mineralogie und Paläologie, Rheinische Friedrich-WilhelmsUniversität Bonn, Germany
2
CSIRO, Adelaide, South Australia, Australia, dirk.mallants@csiro.au3
University of California Riverside, Riverside, California, USA

Recharge in arid and semiarid regions is hypothesized to be highly intermittent and related to
extreme precipitation and associated flooding events. Previous tracer-based studies haveindicated that precipitation events of at least 150 – 200 mm are required to generate significant
recharge throughout the arid environments of Central Australia. In this study, the vadose zone
simulator HYDRUS-1D was used to estimate groundwater recharge in the Northern Territory
Ti-Tree Basin based on a 130-year time series of daily meteorological data. Hydraulicproperties for deep unsaturated regolith were generated from a set of 10 pedotransfer functions(PTFs) that used grain size and bulk density data collected from an 11-m long core. Multiple
PTFs were used to account for conceptual model uncertainty in generating regolith hydraulicproperties. The multi-model transfer function approach consisted of running HYDRUS-1D
multiple times with different sets of hydraulic properties, assuming each PTF has an equal
likelihood. To test the effect of vegetation on recharge, simulations were performed for bothbare soil and for a savanna-type vegetation. In the current study, root water uptake for the
predominant Mulga (Acacia aneura) savanna vegetation was incorporated in the recharge
estimation. The analysis of the 130-year precipitation records revealed extreme events (linked
to monsoonal thunderstorms during the summer months) have an average return period of 3
years for a 100-mm rainfall event and 7 years for a 150-mm event. A total of eight major
recharge events were recorded at the bottom of an 11-m deep regolith over the whole timeseries (1889-2015). The analysis of simulated recharge for bare soil indicated that most of theextreme rainfall events yielded recharge events of 9 mm averaged across PTFs and extreme
events (ranging from 5 to 14 mm). Mean annual recharge events ranged from 0.18 mm to 27
mm, averaging at 5.49 mm. Long-term average recharge for Mulga vegetation ranged from 4.5
mm to 8.5 mm based on ten water balance models, each using a different pedotransfer function
to generate regolith hydraulic properties.

15

Selected Applications of HYDRUS Models for Engineering Problems
Giuseppe Brunetti1 and Jirka Šimůnek2
1

Department of Civil Engineering, University of Calabria, Rende, CS 87036, Italy
Department of Environmental Sciences, University of California, Riverside, CA 92521, USA

2

The HYDRUS models have been used extensively to address several scientific and engineering
problems. The ability to simulate coupled water, vapor and energy transport in both thesubsurface and at the soil-atmosphere interface guarantees a high modeling flexibility and abroad range of applicability. Moreover, the combination of HYDRUS with new numerical
techniques is increasingly commonly used, opening up new application fields. In this view,
recent studies have investigated the use of HYDRUS models for the numerical evaluation of
the hydrological behavior of Low Impact Development techniques, such as permeable
pavements, green roofs, and stormwater filters, which were because of their complexity
traditionally analyzed using empirical or conceptual models. One of the most widespread
criticism against mechanistic models, namely the computational cost, is challenged by the useof new numerical methods. A recent HYDRUS application evaluated the use of GaussianProcess Emulators, which mimic the original model while being computationally inexpensive,
for the inverse estimation and the global sensitivity analysis of soil hydraulic properties. In thisperspective, applications are not restricted to hydrological problems. The Lower-Fidelity
Physically-Based Surrogate models have been applied in both agricultural and geothermal
engineering problems. A pseudo-3D model, which couples HYDRUS-2D and a surface flow
model, has been used to simulate furrow irrigation. A similar approach has been adopted tointerpret and describe a thermal response test, used to investigate the thermal properties of theground. In this case, HYDRUS-2D has been coupled with a one-dimensional advection
equation to simulate the heat transfer between a carrier fluid in a pipe and the surrounding soil.
All these applications demonstrate the versatility of HYDRUS, and how the contribution ofmodern numerical techniques could increase its potential in a variety of scientific andengineering problems.

16

A Computationally Efficient Pseudo-2D Model for the Numerical
Analysis of Permeable Pavements
Giuseppe Brunetti1, Jirka Šimůnek2, Thomas Wöhling3, Michele Turco1, and Patrizia Piro1
1

Department of Civil Engineering, University of Calabria, Rende, CS 87036, Italy
Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
3
Department of Hydrology, Technische Universität Dresden, Dresden, Germany

2

Mechanistic models have proven to be accurate and reliable tools for simulating the hydraulicbehavior of permeable pavements. However, their widespread adoption is limited by theircomplexity and computational cost. Recent studies have tried to address this issue by
investigating the application of new techniques, such as surrogate-based modeling. One of suchapproaches includes the development of Lower-Fidelity Physically-Based Surrogates (LFS).
LFSs focus on reducing the computational complexity of a numerical problem by computing
an approximation of the original model. While this technique has been extensively used inwater-related problems, no studies have evaluated its use in LIDs modeling. Thus, the main
aim of this study is the development of the LFS model for the numerical analysis of thehydraulic behavior of permeable pavements. The proposed model decouples the subsurface
water dynamics of a permeable pavement into a) a one-dimensional (1D) vertical infiltration
process and b) one-dimensional saturated lateral flow along the impervious base. The pavement
is horizontally discretized in N elements. HYDRUS-1D is used to simulate the infiltration
process. Simulated outflow from the vertical domain is used as a recharge term for saturated
lateral flow, which is described using the kinematic wave approximation of the Boussinesq
equation. The proposed model has been compared with HYDRUS-2D, which numericallysolves the Richards equation for the entire two-dimensional domain. Results confirmed theaccuracy of the LFS model, which was able to reproduce both subsurface outflow and the
moisture distribution in the permeable pavement, while significantly reducing thecomputational cost.

17Assessing Nitrate Leaching Potential in California’s Agricultural Soils
Through Hydrus-1D Simulations
Efstathios Diamantopoulos1*, Mike Walkinshaw1, Toby O’Geen1, and Thomas Harter1
1

Department of Land, Air and Water Resources, University of California, Davis*corresponding author: ediamant@ucdavis.edu

Nitrate is considered one of California’s most widespread groundwater contaminants. It is asecondary product of nitrogen fertilization applied for agricultural purposes, mainly from nonpoint sources. The fate of nitrate in the soils and the risk of reaching groundwater is a functionof complex physical, chemical and biological processes which occur at different time andspatial scales. The objective of this study is the simulation of nitrate dynamics across the wide
diversity of agricultural soils in California. The parameterization of the Hydrus-based
assessment was based on the SoilWeb Database, taking into account the vertical heterogeneityof soil hydraulic properties in individual soil series. We conducted over 200-thousand Hydrus
simulations across different combinations of about 6000 different soil types, 7 climates and 58
crops. Water flow was simulated using the Richards equation and nitrate transport simulatedusing the advection-dispersion equation assuming that nitrate behaves as a conservative tracer.
Based on the spatial distribution of the soil types as described in SoilWeb database, we present
California-wide maps, helping identify agricultural regions in California that may need
improved irrigation and/or fertilization management. Moreover, this analysis allows us toestimate deep percolation rate under the root zone, annual nitrate mass leached under the rootzone and finally, the concentration of nitrate in the leaching water. All these parameters arevery important for assessing the risk of groundwater contamination. Finally, the results of thesimulations were validated against independent estimates of nitrate in harvest for 58 different
crops.

18

Using HYDRUS-1D for Estimating Soil Hydraulic Parameters from
Capillary Rise and Evaporation Rates Measured Using a Clay Tank andSoil Respiration Chamber, Respectively, and Their Correlation with a
net CO2 Exchange Rate
Miroslav Fér, Radka Kodešová, Antonín Nikodem, and Aleš Klement
Czech University of Life Sciences Prague, Kamýcká 129, 16500 Prague 6 - Suchdol, Czech Republic,
mfer@af.czu.cz

Study was performed on the soil samples from the morphologically diverse study site in loessregion of the Southern Moravia, Czech Republic. The original soil type within this area is a
Haplic Chernozem (remaining on top parts), which was due to erosion changed into a Regosol(steep parts) and colluvial soils (base slope and the tributary valley). Sampling locations wereselected to characterize diverse soil conditions within the area, i.e. soil samples were collected
in July 2014 after wheat harvest from topsoil at 5 points (summit, shoulder, backslope,footslope and toeslope) of the elevation transect and also from the parent material (loess). Grab
soil samples were used to measure basic soil properties and colony forming units (CFU). Soil
hydraulic properties (drying curves) were measured on 100-cm3 undisturbed soil samples
using the multistep outflow experiment and numerical inversion with HYDRUS-1D. Larger
soil samples (diameter of 11 cm and height of 7.5 cm) were taken to measure a net CO2
exchange rate and net H2O exchange rate under increasing soil water content under greenhouseconditions. Initially air-dried soil samples were placed at the top of a kaolin tank and samples
were wetted by a capillary rise up to almost full saturation. Soil respiration properties were
measured using the LCi-SD portable photosynthesis system with Soil Respiration Chamber.
During the experiment potential evaporation from water surface was recorded. Numericalinversion of the measured cumulative capillary rise and potential evaporation data using the
HYDRUS-1D program were again applied to simulate water regime in the columns and to
estimate some of the soil hydraulic parameters (wetting curves). In all cases, the net CO2
exchange rate rapidly increased in the beginning of wetting. Next the net CO2 exchange rate
decreased with increasing soil water content (samples collected at summit, shoulder, backslope
and in the parent material) or remained relatively stable (footslope and toeslope). Rapid decrees
in soil respiration rate associated with initial fast wetting rate (i.e. with parameters of hydraulicconductivity curve), which was the most evident for soil substrate, followed by samples fromsummit, shoulder and backslope. Maximal values of the net CO2 exchange rate were related tothe organic carbon content (R=0.87) and less closely to CFU (R=0.78). No relationship was
found between the net CO2 exchange rate and parameters obtained from the multistep outflow
experiment. On the other hand, close correlation was obtained between the net CO2 exchange
rate and α (R=0.86), n (R=-0.88) or slope at the inflection point (R=-0.90) of the retention curve
resulted from numerical inversion of cumulative capillary rise and potential evaporation data.

19

Modeling the Effect of Tillage and Urban Waste Compost Addition on
Water Flow and Contaminant (Isoproturon, Cu, Cd) Transport inAgricultural Field Using HYDRUS-2D
Vilim Filipović1, Yves Coquet2, Valérie Pot3, Philippe Cambier3, Lana Filipović1,
Sabine Houot3, and Pierre Benoit3
1

Department of Soil Amelioration, Faculty of Agriculture, University of Zagreb, Svetošimunska 25,
10000 Zagreb, Croatia;
2
UMR 7327 ISTO Univ. d’Orléans, CNRS-INSU, BRGM, 45071 Orléans, France;
3
UMR ECOSYS, INRA, AgroParisTech, Univ. Paris-Saclay, 78850 Thiverval-Grignon, France;

Tillage practices and compost amendments modify soil structure and can create heterogeneity
at the local scale within agricultural fields. Urban waste compost may contain certain
contaminants e.g. trace metals, and also affect sorption and degradation processes of othercontaminants (e.g. pesticides). Modeling was performed to evaluate how the presence ofheterogeneity due to soil tillage and repeated compost application affects water flow, pesticide
dynamics and trace metal mobility in soil in the long-term QualiAgro 1 field experiment. Twoexperimental plots amended with a co-compost of sewage sludge and green wastes (SGW) orwith a municipal solid waste compost (MSW) were compared with a control plot (CONT). In
each plot, wick lysimeters, TDR probes and tensiometers were installed to monitor water andsolute dynamics. In the ploughed layer, four zones differing in their structure were identified:compacted clods, non-compacted soil, interfurrows and the plow pan which were precisely
reproduced in the HYDRUS-2D. Metals (Cu and Cd) soil mobility was modeled using sorption
estimation based on equilibrium between CaCl2 and EDTA extractable metal concentrations orusing equations based on pedotransfer functions. From 2004 to 2010, the unamended control(CONT) plot had the largest cumulative water outflow (1388 mm) compared to the MSW plot
(962 mm) and SGW plot (979 mm). Continuous compost addition seems to limit downward
water flow by preventing preferential flow. HYDRUS was able to describe cumulative water
outflow with a model efficiency value of 0.99 for all three plots. The model was able to simulate
isoproturon leaching patterns except for the large preferential flow events which were observedin the MSW and CONT plots immediately after pesticide application. Modeling results indicatethat spatial and temporal variations in pesticide degradation rate due to tillage and compost
application play a major role in isoproturon dynamics. Trace metal mobility simulation showedvery limited metal mobility in the tilled layer even at high trace metal inputs rates due to highsorption to organic matter originating from compost addition.
References:

Filipović, V., Y. Coquet, V. Pot, S. Houot, and P. Benoit, Modeling the effect of soil structure on water flow andisoproturon dynamics in an agricultural field receiving repeated urban waste compost application, Science of
the Total Environment, 499:546–559, 2014.
Filipović, V., Y. Coquet, V. Pot, S. Houot, and P. Benoit, Modeling water and isoproturon dynamics in a soil
profile with different urban waste compost application considering local heterogeneities, Geoderma, 268, 29–
40, 2016.
Filipović, V., P. Cambier, L. Filipović, Y. Coquet, V. Pot, G. Bodineau, A. Jaulin, V. Mercier, S. Houot, and P.
Benoit, Modeling Copper and Cadmium Mobility in an Albeluvisol Amended with Urban Waste Composts,
Vadose zone journal, 15(12), 1-15, 2016.

1

QualiAgro is a field experiment conducted within a INRA-Veolia collaboration.

20

Simulating Subsurface Lateral Flow in Eroded Soils with Contrasting
Horizon Properties Using HYDRUS-2D
Vilim Filipović1, Horst H. Gerke2, Lana Filipović1, and Michael Sommer2,31

Department of Soil Amelioration, Faculty of Agriculture, University of Zagreb, Svetošimunska 25,
10000 Zagreb, Croatia
2
Institute of Soil Landscape Research, Leibniz-Centre for Agricultural Landscape Research (ZALF),
Müncheberg, Germany
3Institute of Earth and Environmental Science, University of Potsdam (UP), Potsdam, Germany

Subsurface lateral flow can be important pathway for water flow and consequently transport ofsolutes (e.g., nutrients, pesticides, trace metals, antibiotics) in soil. This type of preferential
flow is generally initiated when water percolates vertically through an unsaturated soil profile,meets an impeding layer of soil on hillslope, and is diverted laterally downslope whenapproaching saturated conditions. Such conditions can be found in the hummocky arable soil
landscape where tillage and water erosion has shaped the surface topography and modified thesoil horizons above a relatively dense glacial till. Objective of this work was to explore
subsurface lateral flow occurrence using explicit soil profile information in combination with
2D modeling performed using HYDRUS software. The field data was collected from
CarboZALF-D experimental trial. The soil profile was equipped with FDR probes andtensiometers at different depth (i.e., 10, 20, 40, 80, 130 and 200 cm) and additional climatic
data collected daily at the site. Modeling was performed for a period from October 2009 till
August 2014 for a 500 cm x 200 cm vertical cross-section using field morphological and profile
layering descriptions with crop rotation included. First forward simulations using laboratory
measured hydraulic parameters derived from 300 cm3 soil cores did not satisfactorily describe
the observed field water dynamics. Inverse modeling and optimization was then performed on
shorter periods to improve the model performance. With the improved parameter sets from thefitting, two daily rainfall events with same large intensity (74.6 mm/day) were evaluated for
reproducing lateral subsurface flow more closely. These events led to saturated conditions in
the profile above the C horizon, which had a sloping upper boundary and relatively low
hydraulic conductivity. Pressure head and velocity vectors distribution in the soil profile
efficiently captured the extent of subsurface lateral flow. After isolating these events withlateral flow occurrence, bromide tracer was inserted into the model just above the C horizon.
This modeling exercise showed effects of subsurface lateral flow on solute flow pathways,
which was evidently shifted in the sloping direction and distribution of tracer in the whole soil
profile. Although the sloping landscape was qualitatively known for the lateral subsurface flow,
the simulations still revealed relatively little tendency towards lateral flow during the longsimulation period. This indicates that processes such as non-equilibrium type of preferential
flow and the small scale layering with potential anisotropy of the hydraulic conductivity should
be explored more precisely.

21

Stepwise Calibration of Hydraulic Conductivity Changes in a
Laboratory Tank Simulating Managed Aquifer Recharge Operation
Jana Glass1, Thomas Fichtner1, and Catalin Stefan11

Department of Hydrosciences,Technische Universität Dresden, Dresden, Germany
jana.glass@tu-dresden.de

Clogging represents one key issue during the operation of managed aquifer recharge (MAR)schemes, especially relevant when recharging an aquifer with treated wastewater or surface
water. The accumulation of suspended solids and biomass in the soil pore space leads to adecrease in the soil hydraulic parameters and hence a performance reduction of infiltration
systems. Thus, restoration measures need to be applied to recover the infiltration capacity.
Minimizing clogging can therefore increase the overall performance and bring down theoperative costs of MAR facilities.
Four MAR operational scenarios with different combinations of hydraulic loading cycles(6h:18h, 24h:72h) and loading rates (146 m/a, 300 m/a) were simulated in a laboratory tank.
The set-up consists of a 3D, rectangular-shaped stainless steel lysimeter (1.5 x 1.0 x 1.0 m)
with an infiltration basin (0.45 x 0.3 x 0.06 m) installed in the center of its surface. River waterwith on average 25 mg/l dissolved organic carbon and 15 mg/l total suspended solids was
infiltrated in the basin. The spatial and temporal distribution of soil moisture was measured byan array of tensiometers and TDR probes in two different depths at 0.28 m and 0.68 m below
surface. Each of the scenarios resulted in clogging of the soil material at varying time andextent. The clogging rate was estimated taking into account tensiometer data and soil watercontent measurements. Furthermore, tracer tests using KBr were conducted to quantify the
reduction of travel time and relate it to hydraulic conductivity changes.
The specific objective of this paper was to setup a numerical variable-saturated flow model ofthe cross section of the laboratory tank using HYDRUS-2D and calibrate it at different times
during the infiltration period with the help of measured tensiometer and water content data to
represent clogging. The simulation time was chosen to be in accordance with the tracer test
dates to be able to compare the results and covered 3 - 4 days each. The model domain was
divided into three principal layers consistent with the laboratory setup including the main
loamy soil (from the surface down to 78 cm underneath infiltration basin), a 2-cm sand layer
followed by 12.5 cm of coarse gravel as filter layer. Different approaches to calibrate the
HYDRUS-2D model at the different time steps were followed: 1) only the saturated hydraulicconductivity was inversely optimized and 2) in addition to saturated hydraulic conductivity
also the van Genuchten parameters α and n were optimized. The saturated hydraulicconductivity changes received by the stepwise HYDRUS-2D simulations were compared tothose measured by tracer tests.

22

The Movement of Groundwater and Dissolved Salts Through an OilSand Tailings Storage Facility Using Hydrus-2D
Marie Goddard1, Carl Mendoza2, and Majid Hassanizadeh1
1Department of Earth Sciences, Utrecht University, Utrecht, 3508 TA, Netherlands(goddard.marie@gmail.com)
2
Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, AB,
T6G 2E3, Canada (Carl.Mendoza@UAlberta.ca)

We used Hydrus-2D to simulate groundwater flow and dissolved salt transport through a verylarge, partially covered, sand tailings dam. The project goal was to predict future discharge
rates and salt concentrations to aid in understanding the potential impacts on a vegetative coverand salt loadings to the surrounding environment. Transects of piezometers and other
instruments have been established across the dam, resulting in high frequency data sets forclimate, groundwater levels and groundwater quality. These data sets make it possible tocalibrate our 2D model with transient (seasonal) boundary conditions. The uniquecharacteristics of this project were: the extreme climate; the large size of the modeled area; theman-made stratigraphy; and the material properties of the tailings.
The dam is located in northern Canada (56° north) and is subject to five months of sub-zerotemperatures (winter), followed by a rapid spring melt (~95 mm of snow water equivalent),
followed by sparse summer rainfall (~280 mm). The spring melt results in a lengthening of theseepage faces over this brief period, which necessitates a compromise to the boundary
conditions (i.e., seepage vs. flux) at the toes of the slopes. Ideally, a temporal dual-boundary
condition would permit for a better calibration. Additionally, Hydrus-2D cannot simulated
frozen soils and groundwater. Consequently, simulated heads and discharge rates during thewinter months were not fully representative of site conditions.
Our 2D model was unusually large for a Hydrus simulation, with a cross-sectional area of
56,000 m2 with about 90 % of the section being fully saturated. The cross-section was
subdivided into man-made “depositional” cells representing either the dam (active earthworks)
or the beach (passive settlement).
The dam and storage facility are composed of oil-sand tailings (predominantly quartz sand withminor silt, clay and bitumen) which are unique and therefore not described by the standard soil
databases, specifically residual saturation, alpha and n. Our final material properties werechosen using a combination of previously reported results and by trial-and-error calibration.
Compared to values predicted by the UNSODA and Rosetta databases, the resulting parameter
sets are characterized by residual saturation values higher by a factor of three; alpha values
lower by a factor of three; and similar n values. The characterization of these oilsands tailings
aid not only the specific goals of this study, but the more general objective to understand theflushing behavior of this unique material.

23

A New HYDRUS Add-On Module to Model the Interactions Between Plant
Roots, Soil Properties, and Water Flow Conditions in Soils
Anne Hartmann1, Jiří Šimůnek2, Moses Kwame Aidoo3, Sabine J. Seidel4, Naftali
Lazarovitch5
1

UGT Environmental Measurement Devices GmbH, Research & Development, Germany
2
Department of Environmental Sciences, University of California Riverside, CA, USA
3
Wyler Department for Dryland Agriculture, The French Associates Institute for Agriculture andBiotechnology of Drylands, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of
the Negev, Sede Boqer Campus, Israel
4
Institute of Crop Science and Resource Conservation, University of Bonn, Germany

The standard versions of the HYDRUS software do not consider the feedback between the root
growth and conditions in the soil and the root growth is fully defined using input parameters.
A new root growth module was developed as an add-on for the HYDRUS software package(both HYDRUS-1D and HYDRUS (2D/3D)) to model the root growth as a function of different
environmental stresses. In this module, the root growth and the roots spatial distribution is
dynamically affected by various environmental factors such as soil water content or soil
temperature. The root growth model is based on the approach developed by Jones et al. (1991).
The model assumes that various environmental factors, including soil hydraulic properties(determining the availability of water and oxygen for plants) and various other physical,
chemical, and biological variables, can influence the root development under suboptimal
conditions. The environmental conditions are characterized by various growth stress factors.
To incorporate the modeling approach into the HYDRUS software the model of Jones et al.
(1991) was slightly modified. A time-dependent growth function is used to evaluate thepotential rooting depth that is reached when the root development is assumed to be independentof environmental conditions. The actual rooting depth is derived based on the potential rooting
depth by taking into account sub-optimal environmental conditions. The calculation of theactual root length density distribution is based on the use of shape functions. Such functions
represent the potential root length density distribution under optimal conditions. Due to suboptimal environmental conditions, the potential root distribution is altered to an actual root
distribution.
The modified root-growth stress-factor approach is only a first approximation of the effects ofenvironmental factors on root growth and thus still needs to be verified against experimental
data.
The temperature stress factor was the first part of the newly developed HYDRUS add-on
module to be validated by comparing modeling results with measured rooting depths of bell
peppers in an aeroponic experimental system, provided by the Jacob Blaustein Institutes for
Desert Research of the Ben-Gurion University of the Negev in Israel. The experiment was
conducted at three different root zone temperatures of 7, 17, and 27°C. Inverse optimization
was used to estimate a single set of parameters of the newly developed root growth module thatwas found to well reproduce measured time series of rooting depths for all temperature
treatments. It was also found that it is reasonable to approximate parameters representing
biological factors such as the maximum rooting depth and cardinal temperatures with values
from the literature to reduce the number of calibration parameters.

24

The Effects of Rock Fragment Shapes and Positions on Modeled
Hydraulic Conductivities of Stony Soils
Hana Hlaváčiková1, Viliam Novák1, Jirka Šimůnek2, Ladislav Holko1, Zdeněk Kostka1, andMichal Danko1
1Institute of Hydrology, Slovak Academy of Sciences, Bratislava, Slovakia (hlavacikova@uh.savba.sk)
2
Dept. of Environmental Sciences, Univ. of California Riverside, Riverside, CA 92521, USA

Mountain or forest soils usually contain a large number of rock fragments (RF). The amountof rock fragments, their size, shape, position, and spatial distribution in the soil influence
hydraulic properties of stony soils as well as various processes such as water infiltration, water
movement, or the occurrence of runoff. We present measured hydrophysical properties of stonysoils from a small mountain catchment, the methodology of evaluation of stony soil properties,
and a numerical assessment of the influence of rock fragments (stoniness), their shape,
positions, and distributions in a soil matrix on the saturated hydraulic conductivity of a stonysoil. Properties of stony soils were measured in the Jalovecký creek catchment, the Western
Tatra Mts., Slovakia. Hydrological research conducted in the catchment since the late 1980s
proved that subsurface flow often dominates in catchment runoff, the catchment response to
rainfall is very fast, and that the fast response may be enhanced by the high stoniness of thesoils (up to 40 – 70 %).
Despite a lot of field and laboratory data, it is still difficult to assess the influence of rockfragment properties on water flow in stony soils. Therefore, we used a numerical model toevaluate the effects of particular properties of stony soils on the saturated hydraulicconductivity. The assessment was based on a numerical version of the Darcy's classic
experiment that involved steady-state flow through a porous material under a unit hydraulicgradient using the HYDRUS model. Three different shapes of hypothetical rock fragments
were used: a sphere, an ellipsoid with two different positions, and a pyramid. We tried to findout how the shape, orientation, and distribution (regular and irregular) of RFs affect theeffective saturated hydraulic conductivity of the soil. Differences in the effective saturated
hydraulic conductivities of stony soils simulated by the model were also compared with those
calculated using existing empirical equations. The usefulness of the numerical model to assess
the influence of soil matrix texture on the effective saturated hydraulic conductivity of stonysoils was also evaluated. Finally, we have attempted to derive relationships between stoninessand the effective saturated hydraulic conductivity for different rock fragments properties. The
modeling also provided the spatial distributions of pressure heads, volumetric water contents,
and water fluxes in heterogeneous stony soil profiles which may be nearly impossible tomeasure in practice.

25

Simulating a Full-Scale Two-Stage Vertical Flow Wetland System Using
the HYDRUS Wetland Module
Vincent Hochfeldt, Bernhard Pucher, and Guenter Langergraber*
Institute for Sanitary Engineering and Water Pollution Control, University of Natural Resources andLife Sciences, Vienna (BOKU University), Austria, *guenter.langergraber@boku.ac.at

Treatment wetlands are natural treatment technologies that efficiently treat many different
types of polluted water. Treatment wetlands are engineered systems designed to optimize
processes found in natural environments and are therefore considered environmentally friendly
and sustainable options for wastewater treatment. In Austria, treatment wetlands with a singlestage vertical flow (VF) bed that is intermittently loaded are state-of-the-art because thisconfiguration can guarantee the legal requirements regarding effluent concentrations.
Currently, about 5'700 of this treatment systems are in operation. A two-stage VF wetland
system was developed to optimize the treatment performance of VF wetlands. In 2010, the firsttwo-stage VF wetland system was implemented in full-scale.
In this study, the full-scale two-stage VF wetland system is simulated using the HYDRUS
Wetland Module whereby the CW2D biokinetic model was used (Langergraber and Šimůnek,2012). The results of the study can be summarized as follows:•
The matrix flow model (Richard's equation) used provides a good description of thewater flow in both stages of the two-stage VF wetland.
•
When simulating the tracer experiment the results vary between the coarser sandfilter media used in the first stage and the finer sand media in the second stage
parameters.
•
Parameter adjustments of the CW2D biokinetic model were needed to fit measured
and simulated effluent concentrations in the first stage. For the second stage, the best
fit was achieved when using the standard parameter set. This can be explained by theassumed matrix flow model and its limits in describing water flow in coarse media
such as used in the 1st stage.
•
The implementation of the dual-porosity model within the HYDRUS Wetland
Module, also described by Morvannou et al. (2013) would most likely provide bettera better fit.
References

Langergraber, G., and J. Šimůnek, Reactive transport modeling of subsurface flow constructedwetlands, Vadose Zone Journal, 11(2), doi:10.2136/vzj2011.0104, 14 pp., 2012.
Morvannou, A., N. Forquet, M. Vanclooster, and P. Molle, Which Hydraulic Model to Use in Vertical
Flow Constructed Wetlands? In: Šimůnek, J., M.Th. van Genuchten, and R. Kodešová, (Eds.):
Proceedings of the 4th International Conference HYDRUS Software Applications to Subsurface
Flow and Contaminant Transport Problems, 21-22 March 2013, Prague, Czech Republic, pp.245255, ISBN 978-80-213-2380-3, 2013.

26

Capillary, Film and Vapour Flow During Transient Evaporation:
Inverse Simulation of Lab Experiments Using Pressure Head and
Humidity Data
Sascha C. Iden1, Efstathios Diamantopoulos1,2, and Wolfgang Durner1
1

Division of Soil Science and Soil Physics, Institute of Geoecology,
Technische Universität Braunschweig, Germany
2
Department of Land, Air and Water Resources, University of California Davis, CA, USA.

Evaporation from bare soil is an important component of the water cycle and the surface energybalance in arid and semi-arid regions. Actual evaporation from dry soil cannot be predictedwithout detailed knowledge of the complex interplay between liquid, vapor and heat flow. Soil
hydraulic properties exert a strong influence on evaporation rates during stage-two evaporation.
Recently, significant progress has been made in the experimental characterization of the soil
water retention curve in dry soils and the inclusion of vapor flow into flow models has become
more widespread. However, the determination of unsaturated hydraulic conductivity inmedium to dry soils remains a challenge and most model applications still predict the hydraulicconductivity curve from the water retention curve by capillary bundle models and thus ignore
the effect of water flowing in incompletely-filled pores, i.e. film and corner flow, on thehydraulic conductivity function. The objective of this study was to identify soil hydraulicproperties by inverse modeling, with a particular focus on the medium to dry moisture range.
We conducted evaporation experiments on large, packed soil columns under laboratory
conditions and used an extended instrumentation, consisting of minitensiometers and relative
humidity sensors, to measure the pressure head over a wide range from saturation to -100 MPa.
Evaporation rates and column-averaged water content were measured gravimetrically. The
resulting data were evaluated by inverse modeling using the isothermal Richards equation asprocess model and the Hydrus-1D code as numerical solver for the direct problem. Our results
clearly demonstrate that classic models of soil hydraulic conductivity which are based on theassumption that water flows exclusively in water-filled capillaries cannot describe the observed
time series of pressure head and relative humidity. Although the additional inclusion ofisothermal vapor flow improved the agreement between model and data, an adequate
description of the data was only possible by accounting for an additional flow of liquid water.
The physical cause of the latter could be film and corner flow as proposed before based on atheoretical analysis of water flow in angular porous media.

27Colloid and Colloid-Facilitated Transport Modeling using HPx
Diederik Jacques1, D. Zhou2, J. Makselon3, I. Engelhardt2, and S. Thiele-Bruh4
1

Engineered and Geosystems Analysis, Institute for Environment, Health and Safety, Belgian Nuclear
Research Centre (SCK•CEN), Mol, Belgium, djacques@sckcen.be2
Institute for Applied Geosciences, Hydrogeology Department, TU Berlin, Berlin, Germany
3
Agrosphere (IBG-3), Institute of Bio- and Geosciences, Forschungszentrum Jülich GmbH, Jülich,
Germany
4
Department of Soil Science, University of Trier, Trier, Germany

HPx is a reactive coupled transport model using HYDRUS-1D or HYDRUS (2D/3D) as thetransport solver (water flow, solute transport and heat transport) and PHREEQC-3 as thegeochemical solver. Coupling these two codes resulted in a flexible and extendible coupledmodel as a powerful tool to simulate complex processes in variably-saturated porous media.
Recently, two studies (Zhou et al., 2016; Makselon et al., 2017) used the model to calculatetransport of colloids and contaminated attached to colloids through the subsurface.
The first study (Zhou et al., 2016) simulated the transport of sulfonamides in the absence orpresence of manure colloids from different origin. The model consists of the transport ofdissolved organic matter including interaction of DOM with the solid phase (attachment anddetachment, decay and straining), transport of sulfonamides and their interaction with the solid
phase and the colloids. The model was successfully calibrated to experimental data. Model
results show that mobile colloids act as carriers for sulfomoxole, while immobile colloids block
sulfomoxole from sorbent on the soil. On the other hand, the high affinity of sulfadiazine andsulfamethoxypyridazine for sorbing on immobile colloids retarded their transport.
The second study (Makselon et al., 2016) investigated the effect of flow interruption and ionicstrength on the transport of surfactant-stabilized silver nanoparticles (AgNP). The model
combined the DLVO theory with an extended colloid filtration theory and a colloid releasemodel. The numerical model reproduced the measured AgNP and indicated that attachment tothe air-water interface occurring during flow interruption was the process for AgNP retention.
These two studies illustrate the versatility of the HPx code to study complex processes such as
colloid and colloid-facilitated transport in subsurface systems.
References:
Makselon, J., D. Zhou, I. Engelhardt, D. Jacques and E. Klumpp, Experimental and numericalinvestigations of silver nanoparticle transport under variable flow and ionic strength in soil,
Environmental Science & Technology, 51, 2096-2104, 2017.
Parkhurst, D. L. and C. A. J. Appelo, Description of Input and Examples for PHREEQC Version 3 - A
Computer Program for Speciation, Batch-Reaction, One-Dimensional Transport, and Inverse
Geochemical Calculations, Chapter 43 of Section A, Groundwater Book 6, Modeling Techniques,2013.
Zhou, D., S. Thiele-Bruhn, M. G. Arenz-Leufen, D. Jacques, P. Lichtner, and I. Engelhardt, Impact ofmanure-related DOM on sulfonamide transport in arable soils, Journal of Contaminant Hydrology,
192 118-128, 2016.

28

A Modeling-Based Optimization Framework for Reclamation Leaching
Practices
Issam Khaddam, Stefan Werisch, and Niels Schuetze
Institute of Hydrology and Meteorology, Technische Universität Dresden, Dresden, Germany

The aggravating worldwide water scarcity problems induce all users, especially agriculture, to
optimize their irrigation and leaching water usage. Leaching is considered the most efficientmeasure for managing soil salinity and thereby improving the yield productivity. Traditional
approaches estimate the leaching fraction in dependence of the salinity of the applied waterand the target salinity in the soil and only some additionally consider evapotranspiration.
However, these approaches ignore the two-dimensional distribution of salts in the soil profile,and the time required to apply the evaluated LF. Therefore, more attention should be paid tothe 2D soil salinity distribution in the root zone under leaching practices in order to improve
the salinity management. For this purpose, a 2D simulation-based optimizing framework forleaching was developed. The framework employs the Hydrus 2D model and focuses onreclamation practices under virtual field conditions. Subsequently, the leaching performanceof three different irrigation techniques, namely: (i) sprinkler irrigation, (ii) surface drip
irrigation and (iii) subsurface drip irrigation, was investigated. The framework investigates theleaching sensitivity to the typical management parameters of the irrigation systems, such as theoperation time, sprinkler intensity, drip line positioning and discharge rate. At the end,
numerous number of leaching scenarios that combine the individual techniques and their
management parameters were simulated in two soil types, which are loam and silt. Thereafter,
the simulation results were evaluated in a multi-objective optimization framework to identify
the most effective combinations and the optimal trade-offs between the applied water andremaining salt mass in the soil. Moreover, the framework allows a segment-based analysis bydividing the soil profile to many sub-regions. This division is used in the evaluation stage fortargeting (aggregation) a specific part of the soil profile such as the dense root zone. The
proposed framework is flexible to be modified or expanded to cover different soil types, water
application techniques and initial conditions. It can serve as a valuable tool for planning
reclamation or seasonal leaching measures.

29

Using HYDRUS-1D and 2D for Assessing the Impact of Different RootDistributions on Simulated Root Water Uptake
Aleš Klement, Miroslav Fér, Šárka Novotná, Antonín Nikodem, and Radka Kodešová
Czech University of Life Sciences Prague, Kamýcká 129, 16500 Prague 6 - Suchdol, Czech Republic,
klement@af.czu.cz

Knowledge of the distribution of plant roots in a soil profile (i.e. root density) is needed whensimulating root water uptake from soils using the HYDRUS programs. Barley and wheat wereplanted in a flat laboratory box under greenhouse conditions. Roots were excavated at the endof the experiment and root densities were assessed using root zone image processing and by
weighing. For this purpose, the entire area (width of 40 and height of 50 cm) of each scenario
was divided into 80 segments (area of 5x5 cm). Root density in each segment was expressed
as a root percentage of the entire root cluster. Vertical root distributions (i.e. root density withrespect to depth) were also calculated as a sum of root densities in each 5 cm layer. Resulting
root densities, measured evaporation from the water table (used as the potential root water
uptake), and the Feddes stress response function model were used for simulating substratewater regime and actual root water uptake for all scenarios using HYDRUS-1D and HYDRUS2D. The application of two root detecting techniques resulted in noticeably different root
density distributions. Differences were mainly attributed to the fact that fine roots of highdensity (located mostly at the deeper part of the box) had lower weights in comparison to theweight of few large roots (at the box top). Thus, at the deeper part, higher root density (withrespect to the entire root zone) was obtained using the image analysis in comparison to thatfrom the gravimetric analysis. Conversely, lower root density was obtained using the image
analysis at the upper part in comparison to that from the gravimetric analysis. On the other
hand, fine roots overlapped each other and therefore were not visible in the image, which
resulted in lower root density values from image analysis. Root water uptakes simulated with
HYDRUS-1D using diverse root densities obtained for each cereal declined differently fromthe potential root water uptake values depending on water scarcity at depths of higher root
density. Usually, an earlier downtrend associated with gradual root water uptake decreases andvice versa. Similar root water uptakes were simulated for the presented scenario using the
HYDRUS-1D and HYDRUS-2D models. The impact of the horizontal root density distribution
on root water uptake was, in this case, less important than the impact of the vertical root
distribution resulting from different techniques and sowing scenarios. For more details see
Klement et al. (2016).
Reference:
Klement, R., M. Fér, Š. Novotná, A. Nikodem, R. Kodešová, Root distributions in a laboratory box
evaluated using two different techniques (gravimetric and image processing) and their impact onroot water uptake simulated with HYDRUS, Journal of Hydrology and Hydromechanics, 64(2),196-208, 2016.

30

Using HYDRUS-1D for Simulating Water Flow and Heat Transport
under Various Surface Covers
Radka Kodešová1, Miroslav Fér1, Aleš Klement1, Antonín Nikodem1, Daniela Teplá1, Pavel
Neuberger1, and Petr Bureš2
1

Czech University of Life Sciences Prague, Kamýcká 129, 16500 Prague 6 - Suchdol, Czech Republic,
kodesova@af.czu.cz
2
VESKOM, Ltd, Dolnoměcholupská 522/12a, 102 00 Prague 10, Czech Republic

Different soil covers influence water and thermal regimes in soils within urban areas. Knowledge ofthese regimes is needed, particularly when assessing effectiveness of energy gathering from soils using
horizontal ground heat exchangers. The goal of this study was to calibrate the model HYDRUS-1D for
simulating coupled water and thermal regime in Technosol type soils with grass cover, and to use thismodel for predicting water and thermal regimes under different materials covering the soil surface. For
this purpose, soil water contents were measured at depths of 10, 20, 30, 40, 60 and 100 cm at 4 locations
and temperatures were measured at depths of 20, 40, 80, 120, 150 and 180 cm at three locations (allcovered by grass) from June 2011 to December 2012. In addition, sensors for simultaneous measuring
soil water contents and temperatures were installed under different soil covers (grass, bark chips, sand,basalt gravel and concrete paving) at a depth of 7. The parameters of soil hydraulic properties wereobtained on the 100-cm3 undisturbed soil samples using the multi-step outflow experiment andnumerical inversion of the measured transient flow data using HYDRUS-1D. HYDRUS-1D was thenused to simulated the water regime within the soil profile under the grass cover using climatic data from
June 2011 to December 2012 and some of the soil hydraulic parameters were additionally numerically
optimized using soil water contents measured at all depths. Water flow and heat transport were thensimulated using these parameters, measured thermal properties and temperatures measured close to thesurface applied as a top boundary condition. Simulated temperatures at all depths successfully
approximated the measured data.
Next, water and thermal regimes under another 4 different surface covers were simulated. Soil hydraulicproperties of different materials were partly measured and partly optimized when simulating soil water
regime from June 2011 to December 2012 using the soil water contents measured at the depth of 7 cm
(sand, bark chips, and concrete paving) or set (basalt gravel). The greatest soil water content variability
was obtained (measured at the depth of 7 cm and simulated at different depths) for grass and gradually
decreased for sand, basalt gravel, bark chips and concrete paving. However, in the case of concretepaving the measured soil water contents at the depth of 7 cm could not be successfully approximatedusing HYDRUS-1D due to the fact that measured soil water contents reflected 3D character of waterflow below the paving. The largest temperature oscillations during each day at the depth of 7 cm were
measured for concrete paving (due to this large daily data oscillation measured values could not be
influence by surrounding area) and decreased as follows: basalt gravel, sand, grass and bark chips. As
a result, also temperature oscillations simulated at different depths using measured temperatures as top
boundary conditions followed the same trends. The highest temperatures at different depths during thewarm periods were simulated for concrete paving and decreased as daily temperature oscillations. The
highest temperatures during the cold period were simulated for basalt gravel and decreased for grass,bark chips, sand and concrete paving. Thus, the basalt gravel scenario appeared to be the most efficientfor increasing heating systems effectiveness. For more details see Kodešová et al. (2014).
Reference:
Kodešová, R., M. Fér, A. Klement, A. Nikodem, D. Teplá, P. Neuberger, P. Bureš, Impact of various surface
covers on water and thermal regime of Technosol, Journal of Hydrology, 519, 2272–2288, 2014.

31

Process-Based Models for Subsurface Flow Treatment Wetlands: Recent
Developments and Challenges
Guenter LangergraberInstitute for Sanitary Engineering and Water Pollution Control, University of Natural Resources andLife Sciences, Vienna (BOKU University), Austria, guenter.langergraber@boku.ac.at

To date, only few process-based models for subsurface flow treatment wetlands have beendeveloped. For modeling a treatment wetland, these models have to comprise a number of submodels to describe water flow, pollutant transport, pollutant transformation and degradation,effects of wetland plants, and transport and deposition of suspended particulate matter. The
two most advanced models are the HYDRUS Wetland Module and BIO-PORE. These twomodels are briefly described. This paper shows typical simulation results for vertical flow
wetlands and discusses experiences and challenges using process-based wetland models in
relation to the sub-models describing the most important wetland processes. Experiences with
applying the HYDRUS Wetland Module and other existing simulation tools can be summarised
as follows:• Process-based models are a powerful tool for understanding the processes in treatment
wetlands in more detail.
• All sub-models required to describe the different processes in treatment wetlands areimportant.
− Good calibration of the water flow model is a pre-requisite for achieving a good match
between measured and simulated pollutant concentrations. Due to the intermittent
loading, more data are required for VF wetlands compared to HF wetlands. If the waterflow model is calibrated, good results can be obtained in most applications when using
the standard parameter sets of the biokinetic models.
− A good description of solute transport including adsorption and desorption is of equal
importance for good simulation results for pollutant degradation and removal.
− Influent fractionation (i.e., fractionation of influent COD and the N and P contents ofdifferent COD fractions) has a high impact on simulation results and thus is an essential
part of calibrating reactive transport models.
− Simulating the influence of wetland plants is possible by considering uptake and release
via the plant roots linked to evapotranspiration.
− Models describing clogging are important to describe the long-term behaviour oftreatment wetlands. Up to now, clogging models are the least established and tested
among the sub-models mentioned.
Reference:
Langergraber, G., Applying process-based models for subsurface flow treatment wetlands: Recent
developments and challenges, Water, 9(1), 5, doi:10.3390/w9010005, 2017.

32

Modeling Non-Equilibrium Overland Flow and Transport Processes
Using HYDRUS-1D
Jing Liang1, Scott A. Bradford2, Jiří Šimůnek1, and Anne Hartmann3
1

Department of Environmental Sciences, University of California, Riverside, CA
2
USDA, ARS, US Salinity Laboratory, Riverside, CA
3
Institute of Hydrology and Meteorology, TU Dresden, Germany

The HYDRUS-1D code is a popular numerical model for solving the Richards equation forvariably-saturated water flow and solute transport in porous media. This code was adapted tosolve rather than the Richards equation for subsurface flow the diffusion wave equation foroverland flow at the soil surface. The numerical results obtained by the new model produced
an excellent agreement with the analytical solution of the kinematic wave equation. Model tests
demonstrated its applicability to simulate the transport and fate of many different solutes, suchas non-adsorbing tracers, nutrients, pesticides, and microbes. However, the diffusion wave or
kinematic wave equations describe surface runoff as sheet flow with a uniform depth andvelocity across the slope. In reality, overland water flow and transport processes are rarely
uniform. Local soil topography, vegetation, and spatial soil heterogeneity control directions
and magnitudes of water fluxes, and strongly influence runoff characteristics. There isincreasing evidence that variations in soil surface characteristics influence the distribution of
overland flow and transport of pollutants. These spatially varying surface characteristics arelikely to generate non-equilibrium flow and transport processes. HYDRUS-1D includes ahierarchical series of models of increasing complexity to account for both physical equilibriumand non-equilibrium flow and transport in the subsurface, e.g., dual-porosity and dualpermeability models, up to a dual-permeability model with immobile water. The same
conceptualization as used for the subsurface was implemented to simulate non-equilibrium
overland flow and transport at the soil surface. The developed model improves our ability todescribe non-equilibrium overland flow and transport processes, and improves ourunderstanding of factors that cause this behavior.
Recently, the HYDRUS overland flow and transport model was extended to simulate soil
erosion. HYDRUS-1D soil erosion model has been validated by comparing its predictions withother soil erosion models (e.g., Kineros). The model performed well when the soil particle size
is relatively large. The performance of the soil erosion model will be further evaluated bycomparing its predictions with selected examples from the literature and experimental datasets.

33

Determination of Parameters Describing the Hydraulic Behavior ofFilter Materials for Stormwater Filters Using HYDRUS
Carlos Mir Llorens, Bernhard Pucher*, and Guenter LangergraberInstitute for Sanitary Engineering and Water Pollution Control, University of Natural Resources andLife Sciences, Vienna (BOKU University), Austria, *bernhard.pucher@boku.ac.at

With the increase of extreme events leading to floods, droughts, heat islands and also water
shortage, the demand for interdisciplinary solutions within the urban space is needed. The cityof Vienna is characterized for having several green zones within its city limits including a wide
variety of vegetation. Those green zones shall be used for the retention and treatment of street
runoff but also be able to provide a good environment for the vegetation such as trees. To copewith this demand a variety of filter materials are under investigation (Beinlich, 2016).
With the ability of the HYDRUS software package (Simůnek et al., 2011) to simulated waterflow and solute transport, adsorption behavoir as well as biokinetic reactions as included in the
HYDRUS Wetland Module (Langergraber and Šimůnek, 2012) the interest and need ofmodeling is constantly rising. The most important step to take advantage of this tools is todetermin the needed data for setting up a proper model while the main experiments are carriedout.
In this study the soil hydraulic parameters for the van Genuchten-Mualem soil hydraulic modelare determined of the filter materials under investigation including the following steps:• Column experiments dertmining the water flow behavoir of each filter material byapplying three different rainfall events.
• Determining the saturated hydraulic conductivity (by carrying out a constant head test
accoding to ÖNORM B2506-3, 2016) and the porosity for each filter material.
• Set up a water flow model using HYDRUS based on the measured data.
• Using the in HYDRUS implemented inverse solution, the unknown soild hydraulicparameters, namely the residual water content and the form parameters α and n aredetermined, while the tortuosity parameter in the conductivity function is set to 0.5(Mualem, 1976).
References:
Beinlich, L., Evaluation of Filter Materials for Urban Stormwater Management – GreenInfrastructure in the City of Vienna, Master thesis, University of Natural Resources and Life
Sciences, Vienna (BOKU University), Austria, 2016.
Langergraber, G., and J. Šimůnek, Reactive transport modeling of subsurface flow constructedwetlands using the HYDRUS Wetland module, Vadose Zone Journal, 11(2), 14 pp., 2012.
Mualem, Y., A new model for predicting the hydraulic conductivity of unsaturated porous media,
Water Resources Research, 12(3), 513–522, 1976.
ÖNORM B2506-3, Test criteria for technical filter materials, 2016.
Simůnek, J., M. Sejna, and M. Th. van Genuchten, The HYDRUS Software Package for Simulating
Two- and Three Dimensional Movement of Water, Heat, and Multiple Solutes in VariablySaturated Porous Media, Technical Manual, Version 2.0, PC Progress, Prague, Czech Republic,
pp. 258, 2011.

34

A Coupled HYDRUS-1D - PHREEQC Analysis of Major Ion
Geochemistry and Trace Metal Transport in Soil Leached with Coal
Seam Gas Produced Water
Dirk Mallants1, Anuschka Buter1, and Jirka Šimůnek2
1

CSIRO, Adelaide, South Australia, Australia, dirk.mallants@csiro.au
University of California Riverside, Riverside, California, USA, jiri.simunek@ucr.edu

2

Coal seam gas (CSG) production in Australia generates large volumes of produced water. Suchwater may contain elevated concentrations of naturally occurring inorganic and organic
compounds, and generally has a high salinity. Chemicals unintentionally released from storage
ponds may potentially enter soil, shallow groundwater, as well as receiving surface waters. We
here demonstrate how the reactive transport simulator for variably-saturated porous media HP1(coupled HYDRUS-1D - PHREEQC) was used to assess risks to soil and shallow groundwaterassociated with leaching of CSG produced water. We evaluate the fate of naturally occurring
inorganic chemicals, cadmium, lead and uranium, in soil as a result of unintentional releasefrom storage ponds. Our work reviews exposure pathways and relevant hydrogeochemical
processes, and collates physico-chemical properties of inorganic contaminants as input to a setof generic simulations of transport and attenuation in variably saturated soil profiles. In
addition to modeling the coupled processes of variably-saturated flow and transport of multiple
contaminants and major ions in soil, sensitivity analysis are undertaken to test the robustnessof chemical migration and attenuation with regards to hydraulic and chemical parameters andboundary conditions. The focus of the assessment is on the trace metals cadmium, lead, anduranium. Chemical attenuation processes in soil include adsorption of metals through cationexchange and surface complexation. The assessment is based on an analysis, in space and time,of adsorbed and aqueous phase metal concentrations and relative abundance of dissolved metal
species. Results show that the main process responsible for metal migration in soil iscomplexation of naturally present metals with inorganic ligands such as (bi)carbonate, chloride,and hydroxyl ions. These ligands enter the soil upon infiltration with alkaline produced water.
Metals naturally present in soil on the adsorption sites, albeit at low levels, will desorb due toformation of mobile metal-ligand compounds. These metal-ligand compounds travel relatively
unretarded through soil.

35

Defining Safe Water Quality Requirements for Sustainable Irrigation
with Coal Seam Gas Produced Water
Dirk Mallants1 and Jirka Šimůnek2
1

CSIRO, Adelaide, South Australia, Australia, dirk.mallants@csiro.au
University of California Riverside, Riverside, California, USA, jiri.simunek@ucr.edu

2

Coal seam gas produced water is generally high in total dissolved solids and has a high salinity
which may affect soil and plant health if used untreated for irrigation. Use of irrigation waters
with a high sodium absorption ratio (SAR) will result in salt accumulation in the soil profile,potentially impacting crop yield. Use of irrigation water with high SAR values may further
result in dispersion of soil clay minerals resulting in loss of soil structure, increasing erodibility,
restricting water entry and reducing infiltration capacity. This study considers coupledprocesses of variably-saturated water flow, plant water uptake and coupled transport ofmultiple major ions in soils irrigated with produced water featuring different water qualities.
By coupling major ion soil chemistry to unsaturated flow and plant water uptake, and by
explicitly incorporating effects of salt concentrations on soil hydraulic properties and on root
water uptake (the so-called salinity stress), critical soil processes required for salinity risk
assessment associated with coal seam gas produced water are included in the analysis.
Simulations with different irrigation water qualities provided detailed results regarding
chemical indicators of soil and plant health, i.e., SAR, EC, and sodium concentrations. By
comparing such indicators in the soil profile with permissible ANZECC values, an assessment
was made of the risk to soil and plant health. We also evaluated the effect of high salt
concentrations in the soil profile on plant salinity stress, a condition which reduces the capacity
for plants to uptake water causing yield reduction. Finally, the simulations also allowed to test
if soil hydraulic properties, in particular the hydraulic conductivity, are negatively impacted byhigh salt concentrations, especially by the accumulation of the monovalent cations sodium andpotassium.

36Natural Soil Attenuation Potential of Hydraulic Fracturing Chemicals
and Their Transformation Products
Dirk Mallants1, Jirka Šimůnek2, Andrew Taylor1, Mike Williams1, and Rai Kookana1
1

CSIRO, Adelaide, South Australia, Australia, dirk.mallants@csiro.au
University of California Riverside, Riverside, California, USA, jiri.simunek@ucr.edu

2

Coal seam gas produced water contains compounds originating from the use of hydraulicfracturing fluids together with naturally occurring organic chemicals (geogenics). If leakage of
produced water from storage ponds occurs as a result of flooding or containment failure,
contamination of surface waters and shallow groundwater may happen. This study was
conducted to evaluate the fate of such chemicals in soil as a result of unintentional releases.
We simulated coupled processes of flow, transport and first-order transformation of hydraulicfracturing chemicals (a biocide, a surfactant and a solvent) and geogenics (phenol, 2methylphenol and naphthalene) in a clay soil. A literature review of transformation pathways
for chemical additives found hydrolysis as the only degradation mechanism for bronopol (abiocide, half-life T1/2 = 1.5 years); limonene (a solvent, T1/2 = 2.3-18 days) was found to degrade
under aerobic conditions, while both aerobic and anaerobic biodegradation had been
considered for 2-butoxyethanol (a surfactant, T1/2 = 7 – 112 days). Hydrolysis was found theonly transformation pathway for phenol (T1/2 = 0.11-23 days), while aerobic and anaerobic
biodegradation had been reported for 2-methylphenol (T1/2 = 1.6-7 days) and naphthalene (T1/2= 80 days). Literature values for the organic carbon partition coefficient KOC were shown to be
medium (up to ~10 L/kg) for 2-butoxyethanol, large (up to ~ 103 L/kg) for 2-methylphenol,
bronopol and phenol, to very large (up to ~104 L/kg) for naphthalene and limonene. All of thechemical transformation products were found to have either T1/2 or KOC values supportive of
natural attenuation. Simulation with the variably saturated HYDRUS code showed that the
combined effect of generally strong sorption and fast degradation resulted in nearly complete
removal of all chemicals in the top 5 to 10 cm of the soil profile.

37

Using HYDRUS Codes and Scaling Factors Characterizing Spatial andTemporal Variability of Soil Hydraulic Properties for Assessing the
Impact of Soil Erosion on Soil Water Hydrology
Antonín Nikodem, Radka Kodešová, Miroslav Fér, and Aleš Klement
Czech University of Life Sciences Prague, Kamýcká 129, 16500 Prague 6 - Suchdol, Czech Republic,
nikodem@af.czu.cz

Study was performed on soil samples from the morphologically diverse study site in loessregion of the Southern Moravia, Czech Republic. The original soil type within this area is a
Haplic Chernozem (remaining on top parts), which was due to erosion changed into a Regosol(steep parts) and colluvial soils (base slope and the tributary valley). One representativetransect, with the most diverse terrain attributes (i.e. elevation, slope, curvature, expositionetc.), which caused the most variable soil properties of surface horizon, was delineated. Fivesampling points were selected assuming that soil at different points should be modified bydifferent stages of erosion-accumulation processes: summit, shoulder, backslope, footslope,and toeslope. Grab soil samples were used to measure basic soil properties. Soil hydraulicproperties, θ(h) a K(h), were measured on 100-cm3 undisturbed soil samples (taken before andafter the vegetation period) using the multistep outflow experiment and numerical inversion
with HYDRUS-1D. Next the reference soil hydraulic properties, θ*(h*) a K*(h*), and scaling
factors (αh, αK a αθ) were evaluated to describe spatial and temporal variability of the soil
hydraulic properties. In general, larger values of αh factor and lower values of αK a αθ factors
were obtained before vegetation period in comparison to those obtained after the vegetation
period. While no trends in scaling factors along the elevation transect were observed before
vegetation season, the evident trends were observed after the harvest. Finally, HYDRUS-1D
and 2D programs were used to evaluate variable conditions on a soil water regime.

38

Simulation Results Using the HYDRUS Wetland Module for Different
Sized Filter Medias in Vertical Flow Treatment Wetlands
Bernhard Pucher* and Guenter LangergraberInstitute for Sanitary Engineering and Water Pollution Control, University of Natural Resources andLife Sciences, Vienna (BOKU University), Austria, *bernhard.pucher@boku.ac.at

The field of treatment wetland (TW) simulation is constantly growing over the last decades
and has evolved from looking at such systems as a black box to describing the simultaneous
occurring physio-chemical and biological processes responsible for the degradation ofpollutants (Meyer et al., 2015). Named processes are described within the two biokinetic model
formulations implemented in the HYDRUS Wetland Module, namely CW2D (Langergraberand Šimůnek, 2005) and CWM1 (Langergraber et al., 2009).
In this study, three vertical flow TW systems (Table 1) with different filter media and grain
size are used in order to compare the simulation results of the HYDRUS Wetland Module using
the CW2D biokinetic model and its standard parameter set.
Table 1: General description of the TW systems simulated

System 1
System 2
System 3

Type
Wastewater Main filter media Depth
Austrian system pre-treated
Sand
50cm
Austrian system pre-treated
Sand
50cm
French systemraw
Pea gravel
40cm

Grain size
0.063-4 mm
1-4 mm
2-4mm

Area
Drainage
1 m²
free
1 m² impounded
2.3 m²free

The simulation of each system is carried out using the following steps:•••

Simulation of the water flow using the van Genuchten-Mualem soil hydraulic model withmeasured and literature values depending on the availability.
Fitting the hydraulic model using the inverse solution provided in HYDRUS.
Solute transport and degradation of the wastewater constituents, namely COD, NH4-N, NO2N, NO3-N and P using the Wetland module with the CW2D model.

For all three systems a good fit of the flow model can be achieved and hence should lead to agood fit of the biokinetic model. The results will show that this true for fine filter materials as
used in System 1 while for coarse materials represented by Systems 2 and 3 the simulated
results give better treatment performances than measured. For those system a good fit can only
be achieved when adjusting several parameters of the CW2D model.
References:
Langergraber, G., D. P. L. Rousseau, J. García, and J. Mena, CWM1: A general model to describe
biokinetic processes in subsurface flow constructed wetlands, Water Science and Technology,
59(9), 1687–1697, 2009.
Langergraber, G., and J. Šimůnek, Modeling variably saturated water flow and multicomponent
reactive transport in constructed wetlands, Vadose Zone Journal, 4(4), 924–938, 2005.
Meyer, D., F. Chazarenc, D. Claveau-Mallet, U. Dittmer, N. Forquet, P. Molle, A. Morvannou, T.
Pálfy, A. Petitjean, A. Rizzo, R. Samsó Campà, M. Scholz, A. Soric, and A., Langergraber,
Modelling constructed wetlands: Scopes and aims – a comparative review, EcologicalEngineering, 80, 205–213, 2015.

39

Unveiling Multi-Dimensional Water Flow and Solute Transport Using
HYDRUS Codes
Iael Raij, Golan Bel, and Naftali Lazarovitch
Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Israel
Numerical models are used as a research tool to understand, quantify and predict phenomena
and processes in the soil-plant-atmosphere continuum of the agricultural field. Despite theinherent complexity, their use is growing thanks to a better understanding of processes related
to water flow and solute transport in porous media, the development and improvement ofmathematical methods for solving equations and the rapid development of computers that areable to calculate different processes at finer time and space intervals.
Even though irrigation and fertigation in agriculture are usually addressed unidimensionally(e.g., irrigation depth in mm), plant growth, water and solute distribution are, in fact,
multidimensional. The use of one-dimensional models to represent three-dimensional patterns
may lead to erroneous conclusions.
While models are cost-effective tools for optimizing input regimes, as well as for estimating
and preventing environmental damage by agricultural activities, their value is highly dependent
on the accuracy of their parameterization, often determined by calibration. However, currently
with new personal computers, long computational times are required for multicomponent
multidimensional modeling.
Using numerical results from four different studies, we will present possibilities for facilitating
the optimal use of computational resources. These examples include: A. encapsulating waterflow from surface drip irrigation using an artificial neural network; B. describing infiltrationfrom surface sources by adding an edge effect into 1D simulations; C. inferring soil andirrigation heterogeneity effects on drainage amount and concentration in lysimeters using
sequential simulations; and D. determining first-order degradation in heterogeneous soil
using ParSWMS.
As of today, large domains, long simulation times and high heterogeneity exhaust both thecomputer and the user. Regrettably, optimization procedures such as inverse modeling remain
impractical for 3D simulations with the current average user’s computational resources.

40

Recent Developments and Applications of the HYDRUS Software
PackagesJiří Šimůnek1, Martinus Th. van Genuchten2,3, Diederik Jacques4, and Miroslav Šejna51

Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
Department of Mechanical Engineering, Federal University of Rio de Janeiro, UFRJ, Brazil
3
Department of Earth Sciences, Utrecht University, Netherlands
4
Institute for Environment, Health, and Safety, Belgian Nuclear Research Centre (SCK•CEN), Mol,
Belgium
5
PC-Progress, Ltd., Prague, Czech Republic
2

The HYDRUS-1D and HYDRUS (2D/3D) software packages are widely used finite element
models for simulating the one-, and two- or three-dimensional movement of water, heat, andmultiple solutes in variably saturated media, respectively. In 2013, at the previous Hydrus
conference (also in Šimůnek et al., 2008), we described the entire history of the developmentof the various HYDRUS programs and related models and tools, such as STANMOD, RETC,ROSETTA, UNSODA, UNSATCHEM, HP1, and others. The objective of this presentation(and also of Šimůnek et al., 2016) is to review selected capabilities of HYDRUS that have been
implemented since then. Our review is not limited to listing additional processes that were
implemented in the standard computational modules, but also describes many new standard
and non-standard specialized add-on modules that significantly expanded the capabilities of
the two software packages. We also review additional capabilities that have been incorporated
into the graphical user interface that supports the use of HYDRUS (2D/3D). Another objectiveof this manuscript is to review selected applications of the HYDRUS models, such as
evaluation of various irrigation schemes, evaluation of the effects of plant water uptake ongroundwater recharge, and/or assessing the transport of particle-like substances in thesubsurface.
Reference:Šimůnek, J., M. Th. van Genuchten, and M. Šejna, Development and applications of the HYDRUS andSTANMOD
softwarepackagesandrelatedcodes,
Vadose
Zone
Journal,doi:10.2136/VZJ2007.0077, Special Issue “Vadose Zone Modeling”, 7(2), 587-600, 2008.
Šimůnek, J., M. Th. van Genuchten, and M. Šejna, Recent developments and applications of the
HYDRUS computer software packages, Vadose Zone Journal, 15(7), pp. 25, doi:
10.2136/vzj2016.04.0033, 2016.

41

Current Developments in the HYDRUS Software PackagesJiří Šimůnek1, Martinus Th. van Genuchten2,3, and Miroslav Šejna41

Department of Environmental Sciences, University of California, Riverside, CA 92521, USA
Department of Mechanical Engineering, Federal University of Rio de Janeiro, UFRJ, Brazil
3
Department of Earth Sciences, Utrecht University, Netherlands
4
PC-Progress, Ltd., Prague, Czech Republic

2

In this presentation, we will review current developments of the latest versions of the HYDRUS
software packages. There developments include updates to both the graphical user interface(GUI) as well as the computational modules. The following improvements are made to GUI:
1. Overall review of the code and its update for a new MS Visual Studio, resulting in
better performance, parallelization of graphical operations, availability of morememory (32-bit/64-bit versions), Unicode, etc.
2. Improved 3D graphics: transparency, smoothing, clipping, slicing, 3D raster forvector fields, numbering of isolines, etc.
3. 3D particles (for transient flow) and 2D/3D streamlines (for steady flow), animationof particle movement.
4. Export of results to ParaView, which offers new visualization options including
custom post-processing based on scripting or plugin modules.
5. Resizable dialogs with tables and charts, new components for tables and charts.
6. Displaying results for multiple time layers in cross-section and boundary line charts.
7. About 100 other minor improvements in GUI.
8. Updated documentation (CHM help, online help, User’s manual).
The following new options are being implemented into the computational modules:
1. CO2 transport and production module.
2. Passive root growth.
3. Reservoir boundary condition.
4. Coupled water, vapor, and energy transport and the mass and energy balance at thesurface interface. Considering of the effects of slope inclination and azimuth, andplant shading
With respect to the last option, mass and energy fluxes in the subsurface are closely coupled
and cannot be evaluated without considering their mutual interactions. While hydrological andthermal processes in the subsurface are commonly implemented in existing models, which
often consider both isothermally and thermally induced water and vapor flow, the interactions
at the soil-atmosphere interface are often simplified, and the effects of slope inclination, slope
azimuth, variable surface albedo and plant shading on incoming radiation and spatially variablesurface mass and energy balance, and consequently on soil moisture and temperature
distributions, are rarely considered. In this presentation, we discuss these missing elements andour attempts to implement them into the HYDRUS model. We demonstrate implications ofsome of these interactions and their impact on the spatial distributions of soil temperature andwater content, and their effect on soil evaporation.

42

Coupling DREAM Suite and PEARL for Parameter Inference in a
Bayesian Framework
Stephan Sittig
Dr. Knoell Consult GmbH, Mannheim, Germany

Environmental fate risk assessment for plant protection products (PPP) is conducted partly withnumerical models. The required input parameters are usually derived from direct measurements
in laboratory or field studies or otherwise inferred with inverse modeling techniques.
In this study, the application of the DiffeRential Evolution Adaptive Metropolis algorithm(DREAM; Vrugt, 2016) to inversely estimate parameters on the basis of results from a forward
simulation using the PEARL model (van den Berg, 2016) is demonstrated. To this end,
DREAM Suite v1.02 was used to derive joint posterior parameter distributions of fourparameters describing the fate of an example PPP in the environment (FOCUS standard
substance C, incl. its metabolite): DegT50 (degradation half-life) for both substances, theformation fraction of the metabolite and the initially applied mass. A plug-in was developed toenable the coupling of DREAM Suite and PEARL. The FOCUS Hamburg scenario (FOCUS,
2014a) was applied, using a standard application of 1 kg ha-1, shortly before the emergence ofsummer cereals. Total mass dynamics in the uppermost 30 cm of a soil profile of parent
substance and its primary metabolite were produced in a forward simulation. After themeasurements´ corruption with a 5-% random error, the parameters were inferred.
Convergence was controlled with the Gelman-Rubin criterion, and the multivariate joint
posterior distribution functions were analyzed. Generally, this procedure allows for the
representation of all processes contributing to the dissipation of the species, i.e. microbial
degradation, plant uptake, leaching below the layer under investigation etc. We show acomparison with the standard procedure following FOCUS kinetics (FOCUS 2006, 2014b),
regarding the dissipation only (dissipation half-lives, DT50), after normalization of the timesteps to standard conditions (20°C and field capacity).
We observed an excellent recovery of the parameters used for the production of the synthetic
measurements. The comparison of the standard procedure and the inverse modeling procedureusing a numerical model leads to similar values describing the dissipation (DegT50 or DT50,
respectively) with a considerably reduced formation fraction in the standard approach. The
procedure presented herein can be used to derive true DegT50 values from legacy field studies,
especially for leaching compounds or compounds which were presumed to be uptaken byplants.
References:
FOCUS, Guidance Document on Estimating Persistence and Degradation Kinetics from Environmental Fate
Studies on Pesticides in EU Registration, Report of the FOCUS Work Group on Degradation Kinetics, 2006.
FOCUS, Generic Guidance for Tier 1 FOCUS Ground Water Assessments, Version 2.2, 2014a.
FOCUS, Generic guidance for Estimating Persistence and Degradation Kinetics from Environmental Fate Studies
on Pesticides in EU Registration, 2014b.
van den Berg, F., A. Tiktak, J. J. T. I. Boesten, and A. M. A. van der Linden, PEARL model for pesticide behaviour
and emissions in soil−plant systems; Description of processes, The Statutory Research Tasks Unit for Nature& the Environment (WOT Natuur & Milieu). WOt−technical report 61, 2016.
Vrugt, J. A., Markov chain Monte Carlo simulation using the DREAM software package: Theory, concepts, andMATLAB Implementation, Environmental Modeling & Software, vol. 75, 2016.

43

Modeling Unsaturated Groundwater Flow and Transport in the Vadose
Zone Using GeRa CodeViktor V. Suskin, I. V. Kapyrin, and A. V. Rastorguev
Nuclear Safety Institute of Russian Academy of Sciences, Russia, viksus@ibrae.ac.ru

In the present study we demonstrate the ability of unsaturated groundwater flow and transport
in the vadose zone modeling using GeRa code, which is jointly developed by Nuclear Safety
Institute and Institute of Numerical Mathematics. Also a comparative analysis of unsaturated
unconfined groundwater flow models is done. The code is designed for the safety assessmentof radioactive waste repositories and problems of groundwater protection from chemical
pollution. GeRa is a three-dimensional integral computational code, focused on providing afull sequence of hydrogeological modeling, starting from the generation of the geologicalmodel and meshing, and ending with the calculation of individual radiation doses, which canoccur with the transfer of radionuclide contamination. The features of the code are theavailability of geological modeling tools, the use of adaptive unstructured grids and the abilityof parallel calculations. The basic modeled processes are the following:
1. Groundwater flow (confined, unconfined, saturated-unsaturated).
2. Mass transport (advection, diffusion, dispersion).
3. Radioactive decay chains.
4. Density-driven flow.
5. Heat transport and thermal convection.
6. Geochemical Processes (isotherms and calculation of reactions).
This report presents the results of verification and cross-verification of unsaturated
groundwater flow models implemented in the GeRa code with codes FEFLOW, VS2DT and
HYDRUS on three test problems. The first is the capillary barrier problem, the second is a twodimensional problem of unsaturated flow and transport in heterogeneous vadose zone withradioactive decay, and the third is an experimental problem of groundwater flow and masstransport in the drained tray.
Unconfined model, implemented using pseudounsaturated approach, was cross-verified withthe unconfined MODFLOW model on a two-dimensional problem. The fourth test
demonstrates the fundamental difference between these two models and shows the capillaryeffect on the groundwater flow processes in the vadose zone.

44Development and Evaluation of the Hydrus Package for Modflow
Adam Szymkiewicz1, Jirka Šimůnek2, Anna Gumuła-Kawęcka1, Sahila Beegum2, Bertrand
Leterme3, Beata Jaworska-Szulc1, Małgorzata Pruszkowska Caceres1, Wioletta GorczewskaLangner1, Rafael Angulo-Jaramillo4, and Diederik Jacques3Gdańsk University of Technology, Faculty of Civil and Environmental Engineering, Gdańsk, Poland,
2
Department of Environmental Sciences, University of California, Riverside, CA, USA
3
Institute for Environment, Health and Safety, Belgian Nuclear Research Centre, Mol, Belgium
4
Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés (LEHNA) UMR 5023, France

1

The Hydrus package for Modflow (based on the Hydrus-1D code) allows to include verticalwater flow in the vadose zone, described by the Richards equation, in the modeling frameworkof the Modflow family of computer codes. Simulations of vadose zone flow are used to predictthe rate of recharge or capillary uptake occurring at the groundwater table, as a function of thesoil hydraulic properties, vegetative cover, and atmospheric conditions. A sequential coupling
scheme is used, in which vadose zone flow is solved in a number of soil profiles and resulting
values of the exchange flux are incorporated into the discretized equation describing saturated
groundwater flow in Modflow. The original package, developed by Seo et al. (2007) andTwarakavi et al. (2008), has been updated to be compatible with the Modflow-2005 standard.
Multiple new features are currently being implemented, including alternative models of soil
hydraulic functions and different methods for the evaluation of internodal permeabilities. In
this presentation we focus on: (i) the implementation of the coupling condition between 1Dvariably saturated flow in the soil profiles and 3D saturated groundwater flow, (ii) theinvestigation of the influence of time resolution of the weather data on calculated values of therecharge. Preliminary evaluation results will be presented for the case of a 2D strip aquifer,bounded by surface water bodies and recharged by infiltration.
Reference:

Seo, H.S., J. Šimůnek, and E. Poeter, Documentation of the Hydrus package for MODFLOW-2000, theU.S. Geological Survey Modular Ground-Water Model, GWMI 2007-01, International Ground
Water Modeling Center, Colorado School of Mines, Golden, Colorado, 96 pp., 2007.
Twarakavi, N. K. C., J. Šimůnek, and H. S. Seo, Evaluating interactions between groundwater andvadose zone using HYDRUS-based flow package for MODFLOW, Vadose Zone Journal,
doi:10.2136/VZJ2007.0082, 7(2), 757-768, 2008.

Acknowledgements
This work has been partly supported by National Science Centre, Poland, in the framework of the
project 2015/17/B/ST10/03233 "Groundwater recharge on outwash plain".

45

Water Flow Modeling in the Highly Permeable Pavement Using Hydrus2D
Michele Turco1, Giuseppe Brunetti1, Antonín Nikodem2, Miroslav Fér2, Radka Kodešová2,
and Patrizia Piro1
1

Department of Civil Engineering, University of Calabria, Rende, CS 87036, Italy
Faculty of Agrobiology, Food and Natural Resources, Dept. of Soil Science and Soil Protection,
Czech University of Life Sciences, Kamycká 129, CZ-16521 Prague 6, Czech Republic

2

The increase of urbanization in the last decades has caused, among others, the increase ofimpervious surfaces in spite of those permeable. This is one of the major aspects of theincreasing frequency of flooding events in urban catchments that highlighted all the criticalissues of the traditional urban drainage systems and oriented science and technical towards newstormwater management approaches such as Low Impact Development techniques (LID). LID
systems consist of a series of facilities whose purpose is to intercept stormwater runoff. Amongthe most common LID, permeable pavement (PP) is a facility constructed in layers that
represent a good solution to solve stormwater management problems.
Despite the benefits that it would adopt by using PP, these techniques are not yet widespreadprobably because modeling tools often used simplified methodologies, based on empirical andconceptual equations, that do not take into account hydrological processes in a physical way.
The aim of this work is to assess the suitability of the HYDRUS-2D model correctly describe
the hydraulic behavior of a lab-scale permeable pavement system. The hydraulic properties oftwo (porous concrete blocks and fine gravel used for bedding layers) of the three layers thatcomposed the system were measured using two experimental procedures (clay tank and themultistep outflow experiment, respectively). Soil water retention and hydraulic conductivity
curves were described by the van Genuchten functions. In addition some of the parameters
were optimized with the HYDRUS-2D model from observed water fluxes in the lab-scaleporous pavement system and soil water contents measured in bedding layer. The inverse
solution optimization, which implements a Marquardt-Levenberg type parameter estimation
technique for the estimation of the soil hydraulic parameters, was carried out to calibrate themodel. Measured and modeled hydrographs were compared using the Nash-Sutcliffe efficiency(NSE) index, while the coefficient of determination R2 was used to assess the measured watercontent versus modeled ones in the bedding layer. Obtained results have confirmed thesuitability of HYDRUS-2D to correctly interpret the hydraulic behavior of the lab-scalepermeable pavement system.

46

Sub-Irrigation by Controlled Drainage Systems Using Treated WWTP
Water: Field Test and 2D Modeling Experiments
G. A. P. H. Van den Eertwegh1, R. P. Bartholomeus2,3, D. G. Cirkel2, and K. J. Raat2
1

KnowH2O, Berg en Dal, The Netherlands
KWR Watercycle Research Institute, Nieuwegein, The Netherlands
3
Wageningen UR, Soil Physics and Land Management, Wageningen, The Netherlands
2Agricultural crop yields depend largely on soil moisture conditions in the root zone. Climatechange leads to more prolonged drought periods that alternate with more intensive rainfall
events. With unaltered water management practices, reduced crop yield due to drought stresswill increase. Therefore, both farmers and water management authorities search foropportunities to manage risks of decreasing crop yields. Available groundwater sources for
irrigation purposes are increasingly under pressure due to the regional coexistence of land use
functions that are critical to groundwater levels or compete for available water. At the sametime, treated wastewater from industries and domestic wastewater treatment plants (wwtp) are
discharged to surface waters. Re-use and exploitation of these freshwater sources may be aneffective strategy to balance regional water supply and agricultural water demand. We present
results from a pilot field study in a drought sensitive sandy region in the eastern Netherlands.
In this field pilot, agricultural water supply through reuse of domestic treated wastewater isdelivered to the plant root zone through sub-irrigation by controlled drainage systems. This
sub-irrigation method can be more efficient than classical, aboveground irrigation methods
using sprinkler installations.
Domestic wastewater treatment plants in the Netherlands produce annually 40 to 50 mm
freshwater. A pilot project has been setup in the eastern part of the Netherlands, in which treatedwastewater is applied to a corn field by sub-irrigation during the growing seasons of 2015 and2016, using a climate adaptive drainage system. The chemical composition of treated domestic
wastewater is different from rainfall excess water and agricultural drainage water. In the pilot
project, specific chemicals in the treated wastewater are used as a tracer to describe water andsolute transport in the soil system. Focus of this pilot study is on quantifying potential
contamination of both the root zone and the deeper groundwater with pharmaceutical residues.
We have installed a field monitoring network at several locations on the vadose zone and the
local groundwater system, which enables us to measure vertical solute profiles in the soil waterby taking samples. Based on field data obtained during the experiments, combined with SWAP
(1D) and Hydrus (2D) model simulations, flow and transport of the sub-irrigated treatedwastewater are quantified.

47

Model of Near-Surface Flow in Drying Sandstone
Tomáš Weiss1, Martin Slavík1, and Jiří Bruthans1
1Faculty of Science, Charles University, Albertov 6, 128 43 Prague 2, Czechia,
tomas.weiss@natur.cuni.cz

Porous coarse materials, after reaching a certain low value of water content, form a dry
subsurface layer. Through this layer, water migrates only as vapor, and its flux is governed bydiffusion from subsurface evaporation front to the surface. The goal of this study was todevelop a 1D model that would describe both the near-saturated and the virtually dry
evaporation from sandstone using the Richards equation with van Genuchten – Mualem
hydraulic functions. The model was calibrated to measured evaporation rate from 4 cm deep
initially fully saturated sandstone samples placed in a climate chamber with constant relative
humidity (50 %) and temperature. For the numerical modeling, we used the HYDRUS-1D
software with inverse solution to fit the alpha, n, and l parameters with predefined ranges infunctions for retention curves and unsaturated hydraulic conductivity. The study showed that
it is possible to use Richards equation for very low water content values in near surface withpartially altered hydraulic functions and it suggests to use this approach in combination withcoupled Richards-diffusion equations when solving problems of evaporation from nearly-dry
coarse materials. The study was supported by Czech Science Foundation (GA CR no. 1619459S).

48

49

5th International Conference HYDRUS Software Applications to Subsurface Flow andContaminant Transport Problems
Edited by Jirka Šimůnek, Martinus Th. van Genuchten, and Radka Kodešová
Czech University of Life Sciences Prague
Faculty of Agrobiology, Food and Natural Resources
Department of Soil Science and Soil Protection
Czech RepublicBook of Abstracts
70
50 pagesFirst Printing
2017
ISBN: 978-80-213-2749-8