Our approach has some limitations that need to be understood in order to perform a 522
correct interpretation of the results. One important aspect that the SiSPAT model does not 523
represent is fluid flow due to solute concentration effects (Barbour and Fredlund, 1989;
524
Nachshon et al., 2011). Indeed, as shown by Nassar et al. (1989), the osmotic gradient can be an 525
important driving force for water movement in unsaturated soils with high clay content. We used 526
the approach proposed by Barbour and Fredlund (1989) to determine the order of magnitude of 527
the liquid and water vapor fluxes due to solute concentration gradients. In this analysis, we 528
assumed that sodium chloride (NaCl) was the main component that contributes to the osmotic 529
27 pressure and that the maximum solute concentration occurred at saturated conditions (~25 wt%
530
for NaCl). Also, the observed experimental conditions were utilized to evaluate the temperature 531
in the Van’t Hoff equation (Barbour and Fredlund, 1989), and the experimental soil water content 532
was used to determine the osmotic flow of water within the soil. This analysis resulted in osmotic 533
fluid flows on the order of 10-11 m/s, which are at least one order of magnitude smaller than those 534
obtained using SiSPAT. Thus, in our experiments we expect a small contribution of the osmotic 535
flow of water in the liquid and the gaseous phase.
536
It is also important to discuss that discrepancy between experimental data and model 537
predictions has led to the development of vapor-flux enhancement factors, such as (Philip and 538
de Vries, 1957; Cass et al., 1984). The inclusion of these enhancement factors in numerical 539
models, such as that used in this work, is due to a lack of sufficiently accurate description of 540
vapor dynamics to represent correctly the soil physics processes that occur during evaporation 541
(Assouline et al., 2013). There are many processes that explain this vapor-flux enhancement 542
(Philip and de Vries, 1957; Cass et al., 1984; Bachmann et al., 2001; Grifoll et al., 2005; Shokri 543
et al., 2009; Shahraeeni and Or, 2012; Assouline et al., 2013; Trautz et al., 2015). For instance, 544
investigations have shown that with proper account of capillary flow, continuity and pathways, 545
no vapor-flux enhancement factors are required (Grifoll et al., 2005; Shokri et al., 2009).
546
Shahraeeni and Or (2012) demonstrated that water transport can be enhanced by ~10% when 547
isolated liquid-phase bridges are present due to a reduction in the gaseous diffusion path length, 548
and that thermal gradients can enhance water vapor diffusion. Also, vapor flux from within the 549
soil profile can be enhanced by thermally driven convective transport mechanisms (Bachmann et 550
28 al., 2001). Recently, Trautz et al. (2015) argued that non-equilibrium phase change is also 551
responsible for vapor-flux enhancement.
552
From the vapor-flux enhancement mechanisms that have been reported in the scientific 553
literature, we hypothesize that a combination between non-equilibrium phase change and cyclic 554
thermal conditions typically found between day and night, could be responsible for the vapor-flux 555
enhancement observed in our experiments. When cyclic thermal conditions are present, two 556
processes can drive soil evaporation: evaporation from the soil surface into the atmosphere during 557
early morning and subsurface evaporation limited by Fickian Diffusion until late afternoon. As 558
explained by Assouline et al. (2013), evaporation from the soil surface depletes the water 559
condensed and redistributed during nighttime. After the depletion of this water, Fickian diffusion 560
becomes the governing process and increases the thickness of the dry layer of soil observed at the 561
soil surface. In addition, as discussed by Trautz et al. (2015), non-equilibrium processes are 562
relevant when cyclic thermal conditions occur.
563
Many studies have used laboratory columns, but very few of them have focused on 564
understanding natural highly saline dry soils. Moreover, typical column experiments do not deal 565
with natural highly salty soils and low water content. Our results show that evaporation in 566
initially dry soils produce moisture content and conductivity distributions that are atypical. This 567
behavior has not been reported in the literature, which typically reports experiments in which an 568
initially saturated soil column is subsequently dried out.
569
5. Conclusions
570
29 To improve the understanding of bare soil evaporation, which is typically the main source 571
of aquifer depletion in zones such as those located in the Altiplano basins of northern Chile, we 572
conducted a modeling study to investigate evaporation processes under non-isothermal 573
conditions. A model that couples liquid water, water vapor, and heat transport was developed and 574
calibrated using laboratory observations performed in a homogeneous natural soil column that 575
was filled with soil from the Huasco salt flat, Chile. Modeled and experimental results only 576
agreed when the soil hydrodynamic properties (water retention and hydraulic conductivity curve) 577
were calibrated. The change in the soil hydrodynamic properties can be explained by 578
precipitation/dissolution reactions that are driven by evaporation and that yield a stratified soil 579
profile when quasi steady state conditions were achieved.
580
Model results showed a good agreement with the experimental observations of the soil 581
water content and thermal profiles, and also reproduced the experimental cumulative evaporation 582
with differences of 0.01 and 0.67 mm for the 0.75 and 0.40 m water table depths, respectively.
583
Model results permitted to distinguish three characteristic zones in the soil profile. The first zone 584
(region 1) is located near the surface, where the total flux is directed upwards and the water 585
movement is mainly due to vapor fluxes driven by pressure gradients. The second zone (region 2) 586
is located below region 1 and is where the liquid water flux dominates. The third zone (region 3) 587
is where the liquid water flux is very small. Model results indicate that evaporation occurs in the 588
upper soil profile and that the position of the evaporation front depends on the water table depth.
589
A sensitivity analysis allowed understanding the impact of the enhancement factor and the 590
tortuosity on the cumulative evaporation. The enhancement factor had the largest influence on 591
30 cumulative evaporation that can even result in condensation at the soil surface. This analysis also 592
allowed discarding different set of calibrated parameters that yield non-physical conditions, 593
which minimize the problem of equifinality. The results presented in this study are important as 594
they allow understanding the main evaporation processes that occur in bare soils from Altiplano 595
basins where these processes are not well understood.
596
Acknowledgments
597
The authors acknowledge funding from the Chilean National Commission for Scientific 598
and Technological Research (CONICYT/FONDECYT/1130522). F. Suárez and J. Gironás thank 599
the Centro de Desarrollo Urbano Sustentable for additional support (CEDEUS - 600
CONICYT/FONDAP/15110020), and J. Gironás also acknowledges the Centro de Investigación 601
para la Gestión Integrada de Desastres Naturales (CIGIDEN - CONICYT/FONDAP/15110017).
602
The modeling study presented in this paper was possible thanks to a grant for a stay of M.F.
603
Hernández-López at Irstea, funded by Pontificia Universidad Católica de Chile and Irstea. We 604
also thank the anonymous reviewers for the positive comments that improved this paper.
605
References
606
Abu-El-Sha’r WY, Abriola LM. 1997. Experimental assessment of gas transport mechanisms in 607
natural porous media: parameter evaluation. Water Resource Research, 33(4): 505-516.
608
Alazard M, Leduc C, Travi Y, Boulet G, Ben Salem A. 2015. Estimating evaporation in semi-arid 609
areas facing data scarcity: example of the El Haouareb dam (Merguellil catchment, Central 610
Tunisia). Journal of Hydrology: Regional Studies 3:265-284.
611
31 Assouline S, Tyler SW, Selker JS, Lunati I, Higgins CW, Parlange MB. 2013. Evaporation from 612
a shallow water table: diurnal dynamics of water and heat at the surface of drying sand.
613
Water Resources Research, 49:4022-4034.
614
Bachmann J, Horton R, van del Ploeg RR. 2001. Isothermal and nonisothermal evaporation from 615
four Sandy soils of different water repelency. Soil Sci. Soc. Am. J., 65, 1599-1607.
616
Barbour SL, Fredlund DG. 1989. Mechanisms of osmotic flow and volume change in clay soils.
617
Can. Geotech. J., 26, 551-562.
618
Benavente D, García del Cura MA, Fort R, Ordónez S. 1999. Thermodynamic modelling of 619
changes induced by salt pressure crystallisation in porous media of stone. Journal of Crystal 620
Growth, 204: 168-178.
621
Boulet G, Braud I, Vauclin M. 1997. Study of the mechanisms of evaporation under arid 622
conditions using a detailed model of the soil-atmosphere continuum. Application to the 623
EFEDA I experiment. Journal of Hydrology, 193(1-4): 114-141.
624
Boulet G, Chehbouni A, Braud I, Vauclin M, Haverkamp R, Zammit C. 2000. A simple water 625
and energy balance model designed for regionalization and remote sensing data utilization.
626
Agricultural and Forest Meteorology, 105: 117-132.
627
Braud I, Bariac T, Gaudet JP, Vauclin M. 2005a. SiSPAT-Isotope, a coupled heat, water and 628
stable isotope (HDO and H218O) transport model for bare soil. Part I: Model description 629
and first verification, J. Hydrology, 309(1-4), 277-300.
630
Braud I, Bariac T, Vauclin M, Boujamlaoui Z, Gaudet JP, Biron Ph, Richard P. 2005b. SiSPAT-631
Isotope, a coupled heat, water and stable isotope (HDO and H218O) transport model for 632
32 bare soil. Part II: Evaluation and sensitivity tests using two laboratory data sets, J.
633
Hydrology, 309(1-4), 301-320.
634
Braud I, Biron P, Bariac T, Richard P, Canale L, Gaudet JP, Vauclin M. 2009a. Isotopic 635
composition of bare soil evaporated water vapor. Part I: RUBIC IV experimental setup and 636
results. Journal of Hydrology, 369: 1-16.
637
Braud I, Bariac T, Biron P, Vauclin M. 2009b. Isotopic composition of bare soil evaporated water 638
flow. Part II: Modeling of RUBIC IV experimental results. Journal of Hydrology, 369: 17-639
29.
640
Braud I, Dantas-Antonino AC, Vauclin M, Thony JL, Ruelle P. 1995. A simple soil-plant-641
atmosphere transfer model (SiSPAT) development and field verification. Journal of 642
Hydrology, 166: 213-250.
643
Brooks RH, Corey AT, 1964. Hydraulic properties of porous media. Hydrology paper 3, 644
Colorado State University, Fort Collins, 27 pp.
645
Cahill AT, Parlange MB, 1998. On water vapor transport in field soils. Water Resources 646
Research, 34(4): 731-739.
647
Cass A, Campbell GS, Jones TL. 1984. Enhacement of thermal water vapor difussion in soil. Soil 648
Science Society of America Proceedings, 48: 25-32.
649
de la Fuente A, Niño Y. 2010. Temporal and spatial features of the thermohydrodynamics of 650
shallow salty lagoons in northern Chile. Limnology and Oceanography 55:279-288.
651
Fierro V. 2015. SAR effects on evaporation fluxes from shallow groundwater. M. Sc. Thesis, 652
Pontificia Universidad Católica de Chile, Santiago, Chile.
653
33 Gran M, Carrera J, Massana J, Saaltink MW, Olivella S, Ayora C, Lloret A. 2011. Dynamics of 654
water vapor flux and water separation processes during evaporation from a salty dry soil.
655
Journal of Hydrology, 396: 215-220.
656
Grifoll J, Gastó JM, Cohen Y. 2005. Non-isothermal soil water transport and evaporation.
657
Advances in Water Resources, 28: 1254-1266.
658
Hernández-López MF, Gironás J, Braud I, Suárez F, Muñoz JF. 2014. Assessment of evaporation 659
and water fluxes in a column of dry saline soil subject to different water table levels.
660
Hydrological Processes, 28(10): 3655-3669.
661
Johnson E, Yáñez J, Ortiz C, Muñoz J. 2010. Evaporation from shallow groundwater in closed 662
basins in the Chilean Altiplano. Hidrological Sciences Journal, 55(4): 624-635.
663
Kampf S, Tyler S, Ortiz C, Muñoz J, Adkins P. 2005. Evaporation and land surface energy 664
budget at the Salar de Atacama, northern Chile. Journal of Hydrology 310:236–252.
665
Konukcu F, Istanbulluoglu A, Kocaman I. 2004. Determination of water content in drying soils:
666
incorporating transition from liquid phase to vapour phase. Australian Journal of Soil 667
Research 42(1): 1-8.
668
Laurent JP, Guerre-Chaley C. 1995. Influence de la teneur en eau et de la température sur la 669
conductivité thermique du béton cellulaire autoclave. Materials and Structures, 28:464-472.
670
Lictevout E, Maass C, Córdoba D, Herrera V, Payano R. 2013. Recursos Hídricos Región de 671
Tarapacá – Diagnóstico y Sistematización de la Información. CIDERH. ISBN:978 956 302 672
081 – 6. Available at: http://www.ciderh.cl/documentos/recursos-hidricos-region-de-673
tarapaca/ (last accessed July 2016).
674
34 Liu S, Lu L, Mao D, Jia L. 2007. Evaluating parametrizations of aerodynamic resistance to heat 675
transfer using field measurements. Hydrology and Earth System Sciences, 11: 769-783.
676
Millington RJ, Quirk JM. 1961. Permeability of porous solids. 57. Transaction of the Faraday 677
Society, 57: 1200-1207.
678
Milly PCD. 1984. A simulation analysis of thermal effects on evaporation from soil. Water 679
Resources Research, 20(8): 1087-1098.
680
Nachshon U, Weisbroad N, Dragila MI, Grader A. 2011. Combined evaporation and salt 681
precipitation in homogeneous and heteregenous porous media. Water Resource Research, 682
47: W03513, doi:10.1029/2010WR009677.
683
Nachshon U, Weisbrod N. 2015. Beyond the Salt Crust: On Combined Evaporation and 684
Subflorescent Salt Precipitation in Porous Media. Transport in Porous Media, 110: 295-685
310. DOI: 10.1007/s11242-015-0514-9.
686
Nassar IN, Horton R. 1989. Water transport in unsaturated nonisothermal salty soil: II.
687
Theoretical development. Soil Science Society of America Proceedings, 53: 1330-1337.
688
Novak MD. 2010. Dynamics of the near-surface evaporation zone and corresponding effects on 689
the surface energy balance of a drying bare soil. Agricultural and Forest Meteorology, 690
1501358-1365.
691
Penman HL. 1940. Gas and vapor movement in the soil. I. The diffusion of vapors through 692
porous solids. The Journal of Agricultural Science, 30(4): 570-581.
693
Philip JR, de Vries DA. 1957. Moisture movement in porous materials under temperature 694
gradient. Transactions American Geophysical Union, 38: 222-232.
695
35 Saito H, Simunek J, Mohanty BP. 2006. Numerical Analysis of Coupled Water, Vapor, and Heat 696
Transport in the Vadose Zone. Vadose Zone Journal, 5: 784-800.
697
Schulz S, Horovitz M, Rausch R, Michelsen N, Mallast U, Köhne M, Siebert C, Shüth C, Al-698
Saud M, Merz R. 2015. Groundwater evaporation from salt pans: examples from the 699
eastern Arabian Peninsula. Journal of Hydrology. doi:10.1016/j.jhydrol.2015.10.048 700
Scotter DR. 1974. Salt and water movement in relatively dry soil. Australian Journal of Soil 701
Research, 12(1): 27-35.
702
Sghaier N, Geoffroy S, Prat M, Eloukabi H, Nasrallah SB. 2014. Evaporation-driven growth of 703
large crystallized salt structures in a porous medium. Phys. Rev. E 90, 042402 704
Shahraeeni E, Or D. 2012. Pore scale mechanisms for enhanced vapor transport through partially 705
saturated porous media. Water Resour. Res., 48, W05511, doi:10.1029/2011WR011036.
706
Shokri NP, Lehmann P, Or D. 2009. Critical evaluation of enhancement factors for vapor 707
transport through unsaturated porous media. Water Resour. Res., 45, W10433, 708
doi:10.1029/2009WR007769.
709
Shuttleworth WJ, Wallace JS. 1985. Evaporation from sparse crops an energy combination 710
theory. Quarterly Journal of the Royal Meteorological Society, 111: 839-855.
711
Tang J, Zhuang Q. 2008. Equifinality in parameterization of process-based biogeochemistry 712
models: A significant uncertainty source to the estimation of regional carbon dynamics, 713
Journal of Geophysical Research, 113, G04010, doi:10.1029/2008JG000757.
714
Tóth B, Makó A, Guadagnini A, Tóth G. 2012. Water retention of salt-affected soils: quantitative 715
estimation using soil survey information. Arid Land Research and Management 26:103-716
121.
717
36 Trautz AC, Smits KM, Cihan A. 2015. Continuum-scale investigation of evaporation from bare 718
soil under different boundary and initial conditions: An evaluation of nonequilibrium phase 719
change, Water Resour. Res., 51, 7630–7648, doi:10.1002/2014WR016504.
720
van Genuchten MT. 1980. A closed-form equation for predicting the hydraulic conductivity on 721
unsatured soils. Soil Science Society of America Proceedings, 44(5): 892-898.
722
Vásquez C, Ortiz C, Suárez F, Muñoz JF. 2013. Modeling flow and reactive transport to explain 723
mineral zoning in the Atacama salt flat aquifer, Chile. Journal of Hydrology, 490:114-125.
724
Weisbrod N, Nachshon U, Dragila M, Grader A. 2014. Micro-CT analysis to explore salt 725
precipitation impact on porous media permeability. Transport and Reactivity of Solutions in 726
Confined Hydrosystems. Part of the series NATO Science for Peace and Security Series C:
727
Environmental Security, 231-241.
728
Wissmeier L, Barry DA. 2008. Reactive transport in unsaturated soil: Comprehensive modeling 729
of the dynamic spatial and temporal mass balance of water and chemical components, 730
Advances in Water Resources, 31, 858–875.
731 732
37 Table captions
733
Table 1: Coefficients and variables used in the SiSPAT model to estimate liquid water and water 734
vapor flows.
735
Table 2: Model parameters, and initial and boundary conditions.
736
Table 3: Model parameters used for the three horizons.
737
Table 4: Model calibration efficiency for soil water content () and temperature (T), and 738
comparison of the experimental cumulative evaporation and the data obtained from the calibrated 739
model.
740 741
38 Figure captions
742
Figure 1: Observed and modeled soil water content () and temperature profiles, and observed 743
electrical conductivity () profile for different water table levels (WTL), after 20 days of fixing 744
the water table level. Model results assume a vertically homogeneous soil profile. (a) and (b) 745
show the soil water content profiles for WTL of 0.75 and 0.40 m, respectively; (c) and (d) show 746
the temperature profiles for WTL of 0.75 and 0.40 m, respectively; and (e) and (f) show the 747
electrical conductivity profiles for WTL of 0.75 and 0.40 m, respectively.
748
Figure 2: Observed and modeled soil water content () and temperature profiles for different 749
water table levels (WTL), after 20 days of fixing the water table level and assuming the soil 750
stratifies in three horizons (H1, H2, and H3) due to salt transport. (a) and (b) show the soil water 751
content profiles for WTL of 0.75 and 0.40 m, respectively; (c) and (d) show the temperature 752
profiles for WTL of 0.75 and 0.40 m, respectively.
753
Figure 3: Variation of liquid and water vapor flux along the soil profile for different water table 754
levels (WTL). (a) and (b) show the liquid flux (qL), the water vapor flux (qv) and the total water 755
flux (qtotal) for WTL of 0.75 and 0.40 m, respectively; (c) and (d) show the thermal vapor flux 756
(qvT), the isothermal (due to pressure) vapor flux (qvh), and the total vapor flux (qv) for WTL of 757
0.75 and 0.40 m, respectively. Negative (positive) fluxes correspond to upward (downward) 758
movement.
759 760
39 Figure 4: Comparison of cumulative evaporation (mm) for different tortuosity values (a) and 761
enhancement factors () for the 0.75 and 0.40-m water table levels. a* was calculated based on 762
equation (15) (Millington and Quirk, 1961), and equation (16) was used when = variable (Cass 763
et al., 1984).
764
Figure 5: Water retention curves fitted for each horizon (H1, H2, and H3) for the 0.75 m water 765
table level (a), and the 0.40 m water table level (b).
766
Figure 6. Comparison of the soil water content and temperature profiles for the 0.75-m (a and c) 767
and 0.40-m (b and d) water table levels (WTL), for the simulation presented in Figure 2 (black) 768
and after steady state was reached (red) when using the bottom boundary conditions equal to the 769
top evaporation flux.
770
Figure 7: Comparison of the water vapor fluxes profiles for the 0.75 and 0.40 m water table levels 771
(WTL). Results are shown for different tortuosity values, a, (a) and (c), and for different 772
enhancement factor values, (b) and (d). a* was calculated based on equation (15) (Millington 773
and Quirk, 1961), and equation (16) was used when = variable (Cass et al., 1984). Negative 774
(positive) fluxes correspond to upward (downward) movement.
775 776
40
Table 1: Coefficients and variables used in the SiSPAT model to estimate liquid water and water vapor flows.
777 778
Parameter Formula
Saturated vapor pressure
Diffusivity of water vapor in the air (Philip and De Vries, 1957)
88
Isothermal diffusivity of water vapor (Philip and De Vries, 1957)
h
Thermal diffusivity of water vapor (Philip and De Vries, 1957)
T
Apparent thermal conductivity (Laurent and Guerre-Chaley, 1995)
are empirical fitting parameters of the water retention curve; Ks: saturated hydraulic conductivity (m s-1);
781
41
Table 2: Model parameters and initial and boundary conditions.
787
Parameter Value Observations
Saturated moisture content s (m3 m-3) 0.3 Measured
Residual moisture content r (m3 m-3) 0.0 Parameter fitted from the water retention data Inverse of the air-entry pressure (m-1) 0.7160 Parameter fitted from the water retention data
n (-) 1.1859 Parameter fitted from the water retention data
Saturated hydraulic conductivity Ks (m s-1) 1.06 x 10-5 Measured
Porosity (-) 0.3 Assumed equal to the saturated moisture content
aLG 0.3
Parameters of the apparent thermal conductivity from the Laurent and Guerre-Chaley model (1995).
bLG 0.5
cLG 1.0
dLG 4.0
0 0.12
Initial soil temperature conditions T(z)
Linear interpolation of temperature measurements in the soil at 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40 and 0.45 m. The initial time corresponds to the 1st day after fixing the water table depth.
Initial soil pressure conditions h(z)
Determined from moisture content measurements at 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40 and 0.45 m depth using the water retention curve. The initial time corresponds to the 1st day after fixing the water table depth.
Boundary conditions at the bottom
Known flux A known water flux equal to the evaporation flux This boundary condition was then evaluated in a sensitivity analysis.
T(t) Extrapolated from the measurements of the thermal profile within the soil column.
Boundary condition on the surface T(t) Temperature measured at the soil column surface.
788 789
42
Table 3: Model parameters used for the three horizons.
790
Depth of the water table (m) 0.75 0.40
Horizon H1 H2 H3 H1 H2 H3
Horizon depth (m) 0.20 0.10 0.90 0.15 0.15 0.90
Saturated moisture content, s (m3 m-3) 0.300 0.300 0.300 0.300 0.300 0.300 Residual moisture content, r (m3 m-3) 0.033 0.000 0.000 0.033 0.000 0.000 Inverse of the air entry pressure, (cm-1) 0.6677 0.7163 0.6667 0.40 0.555 0.6667 Shape parameter of the water retention curve, n (-) 1.2370 1.16 1.2470 1.2370 1.1859 1.2470 Saturated hydraulic conductivity, Ks (m s-1) 1.5x10-5 5.0x10-5 1.0x10-5 1.0x10-8 1.5x10-8 1.0x10-5 Shape factor of the hydraulic conductivity curve,
(-) 18 18 18 25 30 30
aLG 0.300 0.734
bLG 0.9 0.3
cLG 35.0 35.0
dLG 5.00 3.82
0 0.12 0.50
791 792 793 794 795 796
43
Table 4: Model calibration efficiency for soil water content () and temperature (T), and comparison of the
797
experimental cumulative evaporation and the data obtained from the calibrated model.
798 799
Depth to groundwater table (m)
0.75 0.40
RMSE (m3 m-3) 0.0095 0.020
B (m3 m-3) 0.002 -0.0003
E (-) 0.985 0.50
RMSET (°C) 2.08 2.61
BT (°C) 0.40 -2.41
ET (-) 0.67 0.46
Experimental cumulative evaporation (mm) 0.85 5.78
Modeled cumulative evaporation (mm) 0.86 5.11
RMSE: root mean square error; B: bias; E: Nash-Sutcliffe efficiency
800 801 802
44 803
Figure 1: Observed and modeled soil water content () and temperature profiles, and observed electrical conductivity
804
() profile for different water table levels (WTL), after 20 days of fixing the water table level. Model results assume
805
a vertically homogeneous soil profile. (a) and (b) show the soil water content profiles for WTL of 0.75 and 0.40 m,
806
respectively; (c) and (d) show the temperature profiles for WTL of 0.75 and 0.40 m, respectively; and (e) and (f)
807
show the electrical conductivity profiles for WTL of 0.75 and 0.40 m, respectively.
808
45 809
Figure 2: Observed and modeled soil water content () and temperature profiles for different water table levels
810
(WTL), after 20 days of fixing the water table level and assuming the soil stratifies in three horizons (H1, H2, and
811
H3) due to salt transport. (a) and (b) show the soil water content profiles for WTL of 0.75 and 0.40 m, respectively;
812
(c) and (d) show the temperature profiles for WTL of 0.75 and 0.40 m, respectively.
813
46 814
Figure 3: Variation of liquid and water vapor flux along the soil profile for different water table levels (WTL). (a)
815
and (b) show the liquid flux (qL), the water vapor flux (qv) and the total water flux (qtotal) for WTL of 0.75 and 0.40
816
m, respectively; (c) and (d) show the thermal vapor flux (qvT), the isothermal (due to pressure) vapor flux (qvh), and
817
the total vapor flux (qv) for WTL of 0.75 and 0.40 m, respectively. Negative (positive) fluxes correspond to upward
818
(downward) movement.
819 820 821
47 822
Figure 4: Comparison of cumulative evaporation (mm) for different tortuosity values (a) and enhancement factors
823
() for the 0.75 and 0.40-m water table levels. a* was calculated based on equation (15) (Millington and Quirk,
824
1961), and equation (16) was used when = variable (Cass et al., 1984).
825 826 827
48 828
Figure 5: Water retention curves fitted for each horizon (H1, H2, and H3) for the 0.75 m water table level (a), and the
829
0.40 m water table level (b).
830 831 832
49 833
834
Figure 6. Comparison of the soil water content and temperature profiles for the 0.75-m (a and c) and 0.40-m (b and
835
d) water table levels (WTL), for the simulation presented in Figure 2 (black) and after steady state was reached (red)
836
when using the bottom boundary conditions equal to the top evaporation flux.
837 838
50 839
Figure 7: Comparison of the water vapor fluxes profiles for the 0.75 and 0.40 m water table levels (WTL). Results
840
are shown for different tortuosity values, a, (a) and (c), and for different enhancement factor values, (b) and (d).
are shown for different tortuosity values, a, (a) and (c), and for different enhancement factor values, (b) and (d).