SOIL PROPERTIES, INITIAL AND BOUNDARY CONDITIONS FOR USE WITHIN SVAT
MODELS IN THE FRAMEWORK OF THE ALPILLES-RESEDA INTERCOMPARISON
Isabelle BRAUD, LTHE and André CHANZY, INRA Avignon
Isabelle.Braud@hmg.inpg.fr Andre.Chanzy@avignon.inra.fr
11 July 2001
O. INTRODUCTION
A framework has been defined in order to compare various SVAT models within the ALPILLES-ReSeDA project. Three scenarios have
been defined:
i)
Scenario 1: Use of parameters and input variables (except meteorological data) measured in situ, without calibration.
ii)
Scenario 2a: Soil parameters are determined from textural data "pedo-transfer functions". Vegetation parameters are estimated
from the bibliography (but LAI is taken as the measured value). Meteorological data are taken from the central meteorological
station. No calibration is allowed. Initial conditions are set such that modelled initial moisture is equal to the measured value.
Scenario 2b: As scenario 2a, except that initial conditions are prescribed according to general knowledge of previous climatic
conditions.
iii)
Scenario 3: In a first step, calibration of parameters is allowed on calibration fields. In a second step, adjusted parameters (or ratio
between a measured and calibrated parameters) on calibration fields are used for the simulation on the validation fields.
This document provides the synthesis of soil parameters to be used for scenarios 1 and 2. "Measured values" were derived from all the
available data. Initial and boundary conditions are also provided for soil moisture (and/or soil water pressure) and soil temperature.
1
I.
HYDRODYNAMIC PROPERTIES
I.1. Retention curves
I.2. Hydraulic conductivity curves
I.3. Organic matter content
3
10
14
II.
THERMAL PROPERTIES
II.1. Volumetric heat capacity
II.2. Thermal conductivity
14
16
III.
INITIAL CONDITIONS
III.1. Simulation periods
III.2. Initial conditions
17
18
IV.
BOTTOM BOUNDARY CONDITIONS
IV.1. Soil moisture and soil water pressure
IV.2. Soil temperature
31
36
V.
38
MAXIMUM ROOTING DEPTH.
APPENDIX: Measured soil water pressure for initial or boundary conditions.
A1. Initial conditions
A.2. Boundary conditions
39
40
REFERENCES
43
2
I. HYDRODYNAMIC PROPERTIES
I.1. Retention curves
I.1.1. Scénario 1 (measured properties)
The retention curve was modelled using the Van Genuchten (1980) model (VG below).

n1   m1
   r   h  
 1
 s   r   hg1  
Van Genuchten:

(1)

m1  1 
with either
or
m1  1 
1
(Mualem hypothesis)
n1
2
(Burdine hypothesis)
n1
Zammit (1999) showed that the Burdine and Mualem parameters could be related by:
2mBurdine
mMualem 
(2)
1  mBurdine
Haverkamp et al. (1997) and Zammit (1999) showed that the shape parameters m and  can be determined from the particle size distribution.
The cumulative particle size distribution can be modelled with a function similar to the Van Genuchten (1980) model by:

 dg
F (d )  1  
d
 
2
1M






M
(3)
where d is the particle diameter, dg is the scale for the diameters.
3
Then the shape parameter of the Van Genuchten model (Burdine hypothesis) is obtained by:
m1  M
4
3
(4)
The model defined by (4) can be adjusted to the data or a simplified formulation function of the clay content C (%) and of the silt content Si (%)
can be used to derive M (Bouraoui et al., 1998)
 C 
log 

2M
C  Si 


1 M
 2
log  
 50 
(5)
The porosity Por can be deduced from dry bulk density d by:

Por  1  d
2.65
(6)
and the saturated water content from porosity and particle size distribution by the following empirical relationship, shown by Haverkamp et al.
(1997) to be a good approximation of the theoretical relationships proposed by Fuentes-Ruiz (1992):
(7)
 s  2m M  Por
When in situ measurements are available, it is of course advisable to use them for the definition of the saturated water content. This method has
been used in the present analysis (use of in situ neutron probe water content measurements).
Note that in all this work the residual water content was supposed to be zero. The hg1 parameter was adjusted on the combination of all
measured values (including laboratory pressure chamber measurements, in situ neutron probe and tensiometers readings and Wind laboratory
measurements (Tamari et al., 1993) when available).
4
Retention curve in the dry domain:
The validity of extrapolating the VG retention curve in the dry domain can be questioned, because the curve was in general calibrated
using wet to medium wet water contents. Physically it could be reasonable to think that the water content in the soil should tend towards zero
more rapidly than the Van Genuchten model (André Chanzy Ph D thesis showed some experimental results on soil close to the Alpilles ones
which could confirm this hypothesis).
It was tried to solve the problem using the approach proposed by Ross et al., 1991 (Soil Sci. Soc. A. J., 55: 923-927) for the Van
Genuchten model (Burdine hypothesis). In the paper they were only dealing with the Brooks and Corey model. The equations for the Van
Genuchten model were developed (see Isabelle BRAUD for more details). The modified model can be written:
2

n1  1 n1


 h 
 
h  hc
  1  




h
 s
g1  




(8)

2
2

1


1


n2
n2
n2
 
  n2
    h  
h
o
 
 1  
h  hc
  1   h  
 hg 2  

s
g
2
 
 

 
 
with ho=-60000m and hc=-100m. Ross et al. (1991) used hc=-1m, which was not relevant for the clay soil we were dealing with. A value of hc=100m enabled the curve to go through the measured values using the pressure chamber up to –100 m. The above model assumes that the water
content is 0 for a pressure equal to ho. (Note that in a first version of the tables distributed by Albert, a value of ho=-10000m was used. This value
was not satisfactory because the relative humidity was still about 0.5. This value was to high for assuming a zero evaporation when the limiting
value was reached. With ho=-60000m, the relative humidity was about a few percent, therefore the evaporation was almost zero at this value)
Assuming that the two parts of the curves were continuous and derivable for h=hc,, the parameters n2 et hg2 could be calculated, knowing
the values of n1 et hg1 estimated on the wettest part of the curve. Those two equations with two unknowns were highly non-linear, but the
convergence was quick using the Newton-Raphson method. The values of n2 et hg2, appear in the tables below.
Table 1 provides the parameters of the Van Genuchten model for the Mualem and Burdine hypotheses. The parameters of the extension in
the dry domain (Burdine hypothesis) are also given.
Field capacity is defined as the water content corresponding to a soil water pressure of –3.3 m and wilting point to a soil water pressure of
–150 m.
5
Table 1: Parameters of the retention curves for scénario 1.
Field
Depth
(cm)
%clay
%silt
% sand
Dry
Porosit Saturat Residu
m1
n1
bulk
y (-)
ed
al
Burdin Burdin
density
water
water
e
e (-)
(g cmcontent content
(-)
3
)
(m3 m- (m3 m3
3
)
)
Uniform soil properties (*) (**)
1.6
0.40
0.381
0
0.0604 2.1286
4
101
0-135
cm or
0-200
cm
41.8
53.9
4.3
101
0-10
38.9
55.8
5.3
1.3
0.509
Non homogeneous soil properties
0.43
0
0.0626 2.133
10-40
39.7
55.7
4.6
1.35
0.49
0.41
40-90
48.1
49.9
2.0
1.6
0.396
90-200
41.3
54.7
4.0
1.68
0.366
203
0-140
41.5
52.4
6.1
1.59
0.40
203
0-600
42.7
51.8
5.5
1.605
0.394
203
0-30
35.2
55.2
9.6
1.53
0.423
0.0637 2.136
3
0.383
0
0.0523 2.1103
1
0.366
0
0.0615 2.131
3
Uniform soil properties (*) (**)
0.36
0
0.0596 2.1268
3
0.36
0
0.0581 2.1234
1
Non homogeneous soil properties
0.405
0
0.0702 2.151
>30
43.2
51.6
5.2
1.61
0.392
0.35
0
0
0.0575
6
2.122
m2
Burdin
e (-)
n2
Burdin
e (-)
hg1
(m)
hg2
(m)
m
Muale
m (-)
n
Muale
m (-)
Wilting Field
point capacit
(m3 m- y (m3
3
)
m-3)
0.0902
2.1982
-4
-109.1
0.114
1.1286
0.239
0.362
0.0538
6
0.0604
8
0.0942
2.1138
-0.4
-84.5
0.1178
1.134
0.195
0.324
2.1287
-0.8
-86.4
0.1198
1.136
0.201
0.337
2.208
-3.0
-125.7
1.110
0.249
0.367
0.0759
1
2.164
-2.0
-99.3
0.0994
2
0.1159
1.131
0.208
0.336
0.091
2.200
-4
-110.9
0.1125
1.1268
0.227
0.349
0.0925
2.205
-4
-114.4
0.1098
1.1234
0.227
0.349
0.0631
7
0.0962
2.135
-1.5
-77.4
0.150
1.177
0.202
0.355
2.213
-4.5
-117.3
0.109
1.122
0.228
0.350
Field
Depth
(cm)
%clay
%silt
% sand
Dry
Porosit Saturat Residu
m1
n1
bulk
y (-)
ed
al
Burdin Burdin
density
water
water
e
e (-)
(g cmcontent content
(-)
3
)
(m3 m- (m3 m3
3
)
)
Uniform soil properties (*)
1.52
0.426
0.38
0
0.0668 2.143
7
Non homogeneous soil properties
1.18
0.555
0.45
0
0.0659 2.141
1.30
0.509
0.42
0
0.0673 2.144
1.59
0.40
0.36
0
0.0671 2.144
Uniform soil properties (*)
1.54
0.419
0.38
0
0.0601 2.128
102
0-140
37.6
57.0
5.4
102
0-10
10-30
30-140
38.4
37.5
37.45
56.9
57.4
57.05
4.7
5.1
5.5
120
(***)
0-140
42.0
53.8
4.2
121
0-140
41.9
54.1
4.0
1.47
0.445
Uniform soil properties (*)
0.40
0
0.0605 2.129
121
0-10
10-30
39.8
42.1
55.6
52.2
4.6
5.7
1.25
1.39
0.528
0.475
Non homogeneous soil properties
0.506
0
0.0636 2.136
0.40
0
0.0589 2.125
30-140
42.1
54.2
3.7
1.51
0.430
0.38
0
0.0604
7
2.128
M2
Burdin
e (-)
n2
Burdin
e (-)
hg1
(m)
hg2
(m)
m
Muale
m (-)
n
Muale
m (-)
Wilting Field
point capacit
(m3 m- y (m3
3
)
m-3)
0.0886
2.194
-5.0
-98.3
0.125
1.143
0.217
0.360
0.0388
0.0496
0.0895
2.08
2.104
2.197
-0.1
-0.4
-5.3
-68.32
-73.4
-98.2
0.124
0.126
0.126
1.141
1.144
1.144
0.187
0.178
0.222
0.321
0.309
0.353
0.0905
2.199
-4.0
-109.7
0.113
1.128
0.239
0.368
0.0768
5
2.166
-2.0
-101.5
0.114
1.129
0.229
0.368
0.0386
0.0618
6
0.0846
3
2.080
2.132
-0.075
-0.6
-72.0
-95.7
0.119
0.111
1.136
1.125
0.180
0.200
0.302
0.323
2.185
-3.0
-106.5
0.114
1.128
0.230
0.362
Field
Depth
(cm)
%clay
%silt
% sand
Dry
Porosit Saturat Residu
m1
n1
bulk
y (-)
ed
al
Burdin Burdin
density
water
water
e
e (-)
(g cmcontent content
(-)
3
)
(m3 m- (m3 m3
3
)
)
Uniform soil properties (*)
1.46
0.449
0.39
0
0.0555 2.117
Non homogeneous soil properties
1.13
0.573
0.554
0
0.0548 2.116
214
0-140
45.9
51.9
2.2
214
0-10
45.2
50.1
4.7
D599
10-30
46.0
50.4
3.6
1.25
1.39
0.528
0.475
0.50
0.40
0
0
0.0543
2.115
30-140
46.0
52.3
1.7
1.50
0.434
0.39
0
0.0557
2.118
M2
Burdin
e (-)
n2
Burdin
e (-)
hg1
(m)
hg2
(m)
m
Muale
m (-)
n
Muale
m (-)
Wilting Field
point capacit
(m3 m- y (m3
3
)
m-3)
0.0869
2.190
-2.5
-116.2
0.105
1.117
0.241
0.368
0.0365
0.0438
2
0.0073
4
0.0957
2
2.076
-0.015
-87.6
0.104
1.116
0.190
0.296
2.0916
2.158
-0.05
-1.0
-92.21
-110.5
0.103
1.115
0.197
0.225
0.307
0.347
2.2117
-4.0
-120.15
0.105
1.118
0.254
0.379
Uniform soil properties (*) (****)
0.442
0
0.0994 2.221
-1.0
0.181
1.222
0.146
0.337
Non homogeneous soil properties
501
0-10
17.0
48.6
34.4
1.24
0.532
0.508
0
0.0949 2.210
-0.1
0.173
1.210
0.109
0.244
10-40
17.0
53.8
29.2
1.28
0.517
0.488
0
0.0997 2.222
-0.25
0.181
1.222
0.118
0.275
5
40-160
17.0
53.8
29.2
1.46
0.449
0.424
0
0.0997 2.222
-1.5
0.181
1.222
0.162
0.369
5
(*) The average texture (clay, sand and silt content) and the dry bulk density were obtained by a weighted average of the values of the non—homogeneous case (the weights
being the corresponding depth of each measurement). The shape parameter and the saturated hydraulic water content were obtained as explained above. The shape parameter
hg was obtained by fitting the analytical curve to the measure of the pressure chamber, where the gravimetric measurements were converted to volumetric values using the
average dry bulk density.
(**) The estimation was performed for two possible choices of the soil column depth.
(***) For field 120, there is no clear difference in dry bulk density. Only a uniform soil profile was defined for the retention curve.
(****) For field 501, there was one of the pressure chamber curve (shieved 40-60cm) which was not collapsing with the other curves. The estimated hg given in the table
corresponds to an average passing in the middle of the two sets of curves.
501
0-160
17.0
53.4
29.6
1.41
0.468
8
I.1.2. Scenario 2.
The pedotransfer functions of Rawls and Brackensieck (1985) were used.
The retention curve was given by:
n

   r   h  
 1
 s   r   hg  


Van Genuchten:
m
(9)
1
(Mualem hypothesis)
n
A 1% organic matter content was assumed for the derivation of the dry bulk density. In this approach, soil were assumed to be vertically uniform.
with
m  1
Table 2. Parameters of the retention curves for scenario 2.
Field
Depth
(cm)
%clay
%silt
% sand
101
0-135 or
0-200
0-140
41.8
53.9
4.3
203
Dry bulk
density (g
cm-3)
(*)
1.45
Porosity
(-)
0.453
Saturated
water
content
(m3 m-3)
0.453
Residual
water
content
(m3 m-3)
0.0998
m
Mualem
(-)
n
Mualem
(-)
hg (m)
Wilting
point (m3
m-3)
Field
capacity
(m3 m-3)
0.151
1.178
-1.161
0.248
0.382
Saturated
hydraulic
conductiv
ity (m s-1)
2.558 108
41.5
52.4
6.1
1.45
0.453
0.453
0.1004
0.153
1.180
-1.120
0.246
0.380
2.842 108
0-600
42.7
51.8
5.5
1.45
0.453
0.453
0.1004
0.147
1.173
-1.164
0.252
0.384
2.414 108
102
120
121
214
0-140
0-140
0-140
0-140
37.6
42.0
41.9
45.9
57.0
53.8
54.1
51.9
5.4
4.2
4.0
2.2
1.38
1.40
1.40
1.40
0.478
0.473
0.473
0.473
0.478
0.473
0.473
0.473
0.101
0.103
0.103
0.103
0.179
0.160
0.160
0.144
1.217
1.190
1.191
1.168
-0.872
-1.01
-1.01
-1.13
0.224
0.246
0.246
0.265
0.374
0.388
0.388
0.401
7.97 10-8
4.4 10-8
4.41 10-8
2.735 108
501
0-160
17.0
53.4
29.6
1.24
0.532
0.532
0.070
0.249
(*) Calculated from Rawls and Brackensieck triangle assuming a 1% organic matter content
9
1.331
-0.251
0.125
0.265
2.74 10-6
I.2. Hydraulic conductivity curves.
I.2.1.Scenario 1
The hydraulic conductivity curves were modelled using the Brooks and Corey (BC below) model.

Brooks and Corey:
 
K  K sm at 
s 
(10)
Fuentes et al. (1992) (J. Hydrol., 134: 117-142) showed that the combination VG+ Burdine hypothesis for the retention curve and BC for
the hydraulic conductivity was the one which was better fullfilling mathematical criteria linked to static or dynamical constraints. Those results
were confirmed by Zammit (1999).
Haverkamp (personal communication, 1999) showed that the shape parameter of the Brooks and Corey model was linked to the shape
parameter of the Van Genuchten model with the following empirical relationship, fitted on the available GRIZZLY soil data base (Haverkamp et
al., 1997):

2
 2  2p
m1n1
(11)
where p is the tortuosity factor related to the shape parameter of the Van Genuchten retention model (Burdine hypothesis) and the particle size
distribution parameter M by:
M  m11  p 
(12)
The saturated hydraulic conductivity corresponding to the soil matrix Ksmat was fitted on the Wind samples measurements (fields 101,
203, 102 only). For the other fields, values were assigned according to the similarity in dry bulk density between measured and unmeasured sites.
10
In situ (simplified infiltration tests and infiltrometers) estimations of the saturated hydraulic conductivity Ks were leading to values several
order of magnitude higher than Ksmat. It was assumed that this discrepancy was linked to the existence of macroporosities and the following
model was proposed:


 
 K  K sm at 

s 

  s

log10( K s )  log10( K ( s  macro )  log10( K s )
 K  10 macro

   s   m acro
(13)
 s   m acro     s
where macro (m3 m-3) is the macropores content and K(s-macro) (m s-1) the hydraulic conductivity at water content (s-macro.)
Values of the parameters corresponding to the above model are provided in Table 3.
Table 3: Parameters of the hydraulic conductivity curves for scenario 1.
Field
Depth
Saturated hydraulic

conductivity of the BC
(-)
model Ksmat (m s-1)
Uniform soil properties
101
0-135 cm or 0-200 cm
5.0 10-9
19.57
Non homogeneous soil properties
101
0-10
5.0 10-9
18.97
10-40
1.8 10-9
18.67
-9
40-90
5.0 10
22.30
90-200
6.4 10-9
19.27
203
203
0-140 cm
0-600 cm
203
0-30
>30
Uniform soil properties
5.0 10-8
19.82
-8
5.0 10
20.28
Non homogeneous soil properties
1.0 10-8
17.13
1.0 10-9
20.47
11
Saturated hydraulic
conductivity Ks
(m s-1)
Macropores content
macro
(-) (*) (**)
2.4 10-6
0.0
7.0 10-6
2.4 10-6
2.0 10-6
2.75 10-6
0.013
0.013
0.013
0.0
1.5 10-6
1.5 10-6
0.0
0.0
1.8 10-6
1.0 10-6
0.03
0.0
Field
Depth
102
0-140 cm
102
0-10
10-30
30-140
120
0-140 cm
120
120
0-30 cm
30-140 cm
121
0-140 cm
121
0-10
10-30
30-140
Saturated hydraulic

conductivity of the BC
(-)
model Ksmat (m s-1)
Uniform soil properties
5.0 10-9
17.89
Non homogeneous soil properties
2.0 10-8
18.12
-9
5.0 10
17.79
1.0 10-9
17.83
Uniform soil properties
1.0 10-9
19.68
Non uniform soil properties (**)
5.0 10-9
19.68
1.0 10-9
19.68
Uniform soil properties
5.0 10-9
19.56
Non homogeneous soil properties
1.0 10-8
18.70
5.0 10-9
20.04
-9
1.0 10
19.59
12
Saturated hydraulic
conductivity Ks
(m s-1)
Macropores content
macro
(-) (*) (**)
5.0 10-6
0.0
1.0 10-5
8.0 10-6
1.0 10-6
0.05
0.03
0.0
2.4 10-6
0.0
2.4 10-6
2.4 10-6
0.013
0.0
2.0 10-6
0.0
2.2 10-6
2.9 10-6
1.0 10-6
0.05
0.03
0.0
Saturated hydraulic
Saturated hydraulic
Macropores content

conductivity of the BC
conductivity
K
(-)
s
macro
model Ksmat (m s-1)
(m s-1)
(-) (*) (**)
Uniform soil properties
214
0-140 cm
5.0 10-9
16.90
3.0 10-6
0.0
Non homogeneous soil properties
214
0-10
2.0 10-8
21.38
3.3 10-6
0.05
-9
-6
10-30
5.0 10
21.56
3.0 10
0.03
30-140
1.0 10-9
21.07
1.0 10-6
0.0
Uniform soil properties
501
0-160 cm
1.0 10-6
12.62
0.0
Non homogeneous soil properties
501
0-10
3.0 10-6
13.14
0.0
10-40
1.0 10-6
12.58
0.0
-7
40-160
1.0 10
12.58
0.0
(*) Proposed estimation from data analysis. Could be considered as a candidate for fitting.
(**) For homogeneous soils and for the lower horizon, macroporosities content is set to zero to avoid unrealistic large water movement (drainage
or capillary rises) at the bottom of the soil profile.
(***) For Field 120, only one retention curve was proposed given the relative homogeneity of soil texture and dry bulk density. However, given
the existence of two contrasted horizons: ploughed layer and underlying soil, a second horizon with a lower saturated hydraulic conductivity was
defined to represent this contrast.
Field
Depth
I.2.2. Scenario 2.
The pedotransfer functions proposed by Rawls and Brackensiek (1985) were also used for the hydraulic conductivity, modelled using the
Van Genuchten model:
1/ 2 
1/ m
    r        r  
 1  1  

K    K s 
Van Genuchten:

  s   r      s   r  

Values of the corresponding parameters appeared in Table 2.
13
m 2



(14)
I.3. Organic matter content
It is given in Table 4 below. Analysis was only performed in the 0-30 cm depth layer. A constant value of 1% was assumed for deeper layers.
Table 4: Organic matter content (%)
Depth
101
0-30 cm
2.5
>30 cm
102
2.5
203
2.2
120
2.2
1.0
121
2.3
214
2.6
501
1.5
II. THERMAL PROPERTIES
II.1. Heat capacity
II.1.1. Scenario 1.
The heat capacity of the solid matter was taken as 755 J kg-1. If a volumetric density of 2650 kg m-3 was assumed for the solid phase, the
volumetric heat capacity of the solid was 2. 106 J m-3 K-1.
The volumetric heat capacity of the soil Ch() (J m-3 K-1) could be derived using the De Vries (1963) model:
Ch    Cdry  4.18 106
(15)
where Cdry  2 106 (1  Por )
(16)
Values of Cdry for the various fields and horizons are given in Table 5 below.
14
Table 5: Values of volumetric heat capacity of the dry soil (106 J m-3 K-1)
Uniform soil
Non homogeneous soil (*)
Depth (cm)
0-140
Horizon 1
Horizon 2
Horizon 3
101
1.20
0.98
1.02
1.21
203
1.20
1.15
1.22
102
1.15
0.89
0.98
1.20
120
1.16
121
1.11
0.94
1.05
1.14
214
1.10
0.85
1.05
1.13
(0.94 after DoE 599)
501
1.06
0.94
0.97
1.10
(*) The depths corresponding to the various horizons can be found in Tables 1 or 3
Horizon 4
1.27
-
II.1.2. Scenario 2.
The De Vries (1963) model, as defined by Eq. (15) and (16) can still be used, provided the dry volumetric heat capacity is calculated
using the dry bulk density given by Rawls and Brackensiek (1985) method (see Table 2). This leads to the following values for Cdry( 106 J m-3 K1
):
Fields 101, 203:
Field 102:
Fields 120, 121, 214
Field 501
1.094
1.044
1.054
0.936
15
II.2. Thermal conductivity
II.2.1. Scenario 1.
A continuous model of the thermal conductivity () (W m-1 K-1), as a function of the volumetric water content  (m3 m-3) was fitted on
all in situ measurements performed using the line source method (Laurent, 1989). The same model was fitted for all the fields and depths. Note
that no measurements were performed on the 501 field. As the latter exhibited a much lower clay content, the corresponding relation ship may
not be adapted to this field.


  


    0.492  0.734
 0.3031  exp   34.54

 sat

  sat 

3.82 




(17)
II.2.2. Scenario 2.
The method proposed by Van De Griend and O'Neill (1986) can be used. The thermal inertia () is expressed as a function of the soil
water content :
     Ch   
1
 s  2300  1890
0.654
(18)
where s is a texture dependent coefficient, tabulated by Van de Griend and O'Neill (1986).
The thermal conductivity is therefore given by:
1
 1
 s  2300  1890
   
6 
Cdry  4.18 10   0.654

2
(19)
Fields 101, 120, 121, 214, 203 belong to the Silty Clay Loam class, leading to a value of s=2440 J m-2 K-1 s-1/2.
Field 102 belongs to the Silty Clay Loam class leading to a value of s=2245 J m-2 K-1 s-1/2.
Field 501 belongs to the Silt Loam class leading to a value of s=2635 J m-2 K-1 s-1/2.
16
III. INITIAL CONDITIONS
III.1. Simulation periods
They are given in Table 6 below. The general rule is that the simulation begins the second day with soil measurements, in order to be sure
that all the sensors were installed.
Table 6: Simulation periods for the various fields.
Field
Beginning DoE
Ending DoE
101 Wheat
387
542 (harvest)
101 Bare soil
626
700
102 Bare soil
387
432
102 Sunflower
519
649
203 Alfafa
389
634
485
526
120 Irrigated
402
458 ? or 461
wheat
464
537
121 Sunflower
509
635
214 Spring wheat
501 Sunflower
443
558
557
607
Depth of the soil column
200 cm(*)
140 cm
140 cm
200 cm (**)
600 cm
600 cm
140 cm
140 cm
140 cm
140 cm
160 cm
(*) An additional simulation must be done using a 140 cm soil depth until DoE 484
(**) An additional simulation must be done using a 140 cm soil depth until DoE 568
17
Remark
Simulation begins after a period with rain, snow, frost
Data before DoE 389 are not accurate due to soil
sursaturation
The simulation period is split in two subperidos, due
to an irrigation on DoE 458?
Tensiometers installed on DoE 509 and soil
temperature on DoE 514
Beginning the first measuring day because the period
is short and all the sensors were installed the same day
III.2. Initial conditions.
III.2.1. Scenario 1
For each beginning date, the soil moisture content and the soil temperature profiles are provided, as well as the average soil moisture
content and temperature other the whole soil column. Initial soil matric potential profiles are also provided. They were derived from the retention
curves presented in section I both for uniform or non-homogeneous soils. Measured soil matric potential were sometimes available and are
provided in Appendix. They were not used in the framework of the intercomparison. Due to uncertainty on adjusted retention curves, their use
could lead to differences between the measured and modelled initial moisture content. In order to make easier the intercomparison, it was decided
that all models should be initialised with the same average moisture content.
Table 7: Initial conditions on DoE 387 (field 101 wheat)
Depth
Volumetric moisture
Soil matric potentiel
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
for non-homogeneous
(m)
soils (m)
0-10
0.4047
0
-0.505
10-20
0.4025
0
-0.480
20-30
0.3987
0
-0.605
30-40
0.3813
0
-1.139
40-50
0.3596
-4.993
-4.489
50-60
0.3665
-3.808
-3.424
60-70
0.3679
-3.568
-3.217
70-80
0.3703
-3.152
-2.863
80-90
0.3713
-2.975
-2.716
90-100
0.3793
-1.198
0
100-110
0.3801
-0.881
0
110-120
0.3801
0
0
120-130
0.3802
-0.833
0
130-140
0.3842
0
0
Average 0-140 cm
0.3805
Average 0-200 cm
0.3816
(*) Data on DoE at 0h10 were missing. Data from DoE 388 at 0h10 were used instead
18
Depth
(cm)
Soil temperature
(°C) (*)
0.5
1
2.5
7.5
15.0
25.0
50.0
100.0
Average 0-140 cm
Average 0-200 cm
8.25
8.30
8.50
8.90
9.1
8.8
8.1
8.4
8.44
8.42
Table 8: Initial conditions on DoE 626 (field 101 bare soil)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.1934
0.2338
0.2351
0.2663
0.2587
0.2843
0.2949
0.2977
0.2981
0.2940
0.2961
0.2956
0.2980
0.3062
0.2751
Soil matric potentiel
for non-homogeneous
soils
(m)
-150.41
-49.73
-47.73
-49.08
-102.70
-43.79
-31.47
-28.88
-28.51
-10.49
-9.94
-10.05
-9.42
-7.59
-333.88
-156.74
-152.40
-64.68
-81.09
-38.78
-29.10
-27.01
-26.71
-29.79
-28.23
-28.54
-26.75
-21.58
19
Depth
(cm)
Soil temperature
(°C)
0.5
1
2.5
7.5
15.5
26.5
49.0
100.0
Average 0-140 cm
13.1
13.6
15.1
18.0
19.9
20.5
20.3
20.5
20.08
Table 9: Initial conditions on DoE 387 (field 102 bare soil)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.4491
0.4548
0.4089
0.4000
0.4000
0.4000
0.3896
0.3656
0.3608
0.3592
0.3544
0.3576
0.3576
0.3528
0.3865
Soil matric potentiel
for non-homogeneous
soils
(m)
-0.059
0
-0.29
0
0
0
0
0
0
-1.09
-2.84
-1.85
-1.85
-3.25
0
0
0
0
0
0
0
-2.68
-3.23
-3.42
-3.99
-3.61
-3.61
-4.19
20
Depth
(cm)
Soil temperature
(°C)
0.5
1
2.5
7.5
15.0
25.0
50.0
100.0
Average 0-140 cm
9.00
9.00
9.00
9.00
9.00
9.00
9.00
9.00
9.00
Table 10: Initial conditions on DoE 519 (field 102 sunflower)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
Average 0-200 cm
0.2352
0.2237
0.2421
0.3100
0.3085
0.3163
0.3261
0.3305
0.3307
0.3260
0.3311
0.3371
0.3412
0.3479
0.3076
0.3197
Soil matric potentiel
for non-homogeneous
soils
(m)
-29.90
-31.71
-18.36
-14.21
-14.73
-12.11
-9.33
-8.23
-8.19
-9.36
-8.08
-6.70
-5.82
-4.37
-85.91
-128.17
-70.23
-12.19
-12.61
-10.50
-8.32
-7.49
-7.45
-8.34
-7.37
-6.36
-5.74
-4.80
21
Depth
(cm)
Soil temperature
(°C)
1.2
1.8
3.5
4.9
7.5
20.4
55.0
95.0
Average 0-140 cm
Average 0-200 cm
14.4
15.0
16.5
16.1
16.7
19.4
18.8
17.3
17.95
17.75
Table 11: Initial conditions on DoE 389 (field 203 alfafa)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
Average 0-600 cm
0.4069
0.4000
0.3900
0.3792
0.3568
0.3474
0.3453
0.3436
0.3458
0.3476
0.3509
0.3528
0.3451
0.3441
0.3624
0.3479
Soil matric potentiel
for non-homogeneous
soils
(m)
0
-0.70
-0.70
0
0
-1.78
-2.39
-2.84
-2.27
-1.69
0
0
-2.45
-2.73
0
0
0
0
-1.71
-3.70
-4.08
-4.41
-4.00
-3.65
-3.02
-2.65
-4.12
-4.32
22
Depth
(cm)
Soil temperature
(°C)
0.5
1.0
2.5
9.0
15.0
30.0
58.0
95.0
Average 0-140 cm
Average 0-600 cm
7.85
8.4
8.5
9.0
9.2
9.0
8.3
8.4
8.55
8.43
Table 12: Initial conditions on DoE 485 (field 203 alfalfa)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
Average 0-600 cm
0.1919
0.1891
0.1919
0.1891
0.1997
0.2138
0.2273
0.2394
0.2529
0.2645
0.2744
0.2788
0.2647
0.2657
0.2317
0.2578
Soil matric potentiel
for non-homogeneous
soils
(m)
-184.53
-197.14
-184.39
-308.77
-252.71
-191.74
-142.48
-101.40
-64.37
-44.46
-32.86
-28.72
-44.31
-42.86
-304.09
-320.21
-303.93
-320.69
-262.57
-199.82
-149.80
-109.12
-69.80
-48.44
-35.9
-31.51
-48.28
-46.72
23
Depth
(cm)
Soil temperature
(°C)
0.5
1.0
2.5
9.0
15.0
30.0
58.0
95.0
Average 0-140 cm
Average 0-600 cm
9.35
9.8
9.75
10.2
10.6
11.0
11.1
11.5
11.12
11.41
Table 13: Initial conditions on DoE 402 (field 120 irrigated wheat)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.4058
0.3467
0.3780
0.3638
0.3670
0.3620
0.3625
0.3676
0.3703
0.3672
0.3675
0.3721
0.3738
0.3723
0.3697
Soil matric potentiel
for non-homogeneous
soils
(m)
0
-7.30
-1.29
-4.11
-3.56
-4.43
-4.33
-3.47
-2.99
-3.53
-3.48
-2.64
-2.33
-2.62
0
-7.30
-1.29
-4.11
-3.56
-4.43
-4.33
-3.47
-2.99
-3.53
-3.48
-2.64
-2.33
-2.62
24
Depth
(cm)
Soil temperature
(°C)
1.0
1.8
3.2
7.7
14.0
30.0
50.0
100.0
Average 0-140 cm
5.3
5.7
5.8
6.5
6.8
6.8
6.9
No data
6.82
Table 14: Initial conditions on DoE 464 (field 120 irrigated wheat)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.3731
0.3289
0.3637
0.3593
0.3600
0.3478
0.3490
0.3581
0.3658
0.3664
0.3689
0.3715
0.3731
0.3752
0.3615
Soil matric potentiel
for non-homogeneous
soils
(m)
-2.46
-11.81
-4.13
-4.89
-4.77
-7.06
-6.81
-5.11
-3.76
-3.67
-3.23
-2.76
-2.45
-2.01
-2.46
-11.81
-4.13
-4.89
-4.77
-7.06
-6.81
-5.11
-3.76
-3.67
-3.23
-2.76
-2.45
-2.01
25
Depth
(cm)
Soil temperature
(°C)
1.0
1.8
3.2
7.7
14.0
30.0
50.0
100.0
Average 0-140 cm
9.4
9.8
10.4
12.1
12.8
12.9
12.2
No data
12.24
Table 15: Initial conditions on DoE 509 (field 121 sunflower)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.0976
0.2277
0.3121
0.2904
0.3119
0.3263
0.3449
0.3436
0.3528
0.3672
0.3783
0.3755
0.3828
0.3830
0.3210
Soil matric potentiel
for non-homogeneous
soils
(m)
-1689.51
-54.36
-4.33
-24.37
-13.80
-9.48
-7.57
-5.98
-4.56
-2.64
-0.91
-1.47
0
0
-2417.19
-144.30
-13.57
-23.86
-13.66
-9.53
-7.73
-6.25
-4.97
-3.40
-2.43
-2.66
-2.06
-2.04
26
Depth
(cm)
Soil temperature
(°C)
0.5
3.2
4.0
6.0
9.2
17.0
27.5
47.0
102.0
Average 0-140 cm
16.35
18.2
19.6
19.1
20.2
20.9
20.2
19.0
15.8
17.63
Table 16: Initial conditions on DoE 443 (field 214 Spring wheat)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
Average 0-140 cm
0.1894
0.3487
0.3291
0.3714
0.3585
0.3609
0.3609
0.3639
0.3658
0.3645
0.3579
0.3621
0.3684
0.3650
0.3476
Soil matric potentiel
for non-homogeneous
soils
(m)
-148.10
-3.17
-5.38
-4.69
-7.27
-6.75
-6.75
-6.13
-5.75
-6.01
-7.40
-6.49
-5.25
-5.91
-387.07
-6.08
-10.43
-2.95
-4.58
-4.25
-4.25
-3.86
-3.62
-3.78
-4.66
-4.09
-3.30
-3.72
27
Depth
(cm)
Soil temperature
(°C)
0.1
1.0
2.3
9.0
15.0
25.0
38.0
100.0
Average 0-140 cm
11.1
12.3
12.0
No data
12.7
12.5
11.6
10.8
11.38
Table 17: Initial conditions on DoE 558 (field 501 Sunflower)
Depth
Volumetric moisture
Soil matric potentiel
3
-3
(cm)
content (m m )
for uniform soils
(m)
0-10
10-20
20-30
30-40
40-50
50-60
60-70
70-80
80-90
90-100
100-110
110-120
120-130
130-140
140-150
150-160
Average 0-160 cm
0.0977
0.0898
0.1034
0.1201
0.1245
0.1196
0.1164
0.1142
0.1250
0.1623
0.2183
0.2614
0.2895
0.3002
0.3109
No data
0.1702
Soil matric potentiel
for non-homogeneous
soils
(m)
-319.46
-512.53
-270.93
-138.37
-498.97
-598.78
-676.61
-736.77
-490.04
-151.32
-39.78
-17.60
-11.05
-9.33
-7.93
-1321.71
-1978.24
-1008.31
-495.56
-416.87
-505.50
-575.20
-629.40
-408.99
-118.10
-28.77
-12.17
-7.46
-6.26
-5.28
Depth
(cm)
Soil temperature
(°C)
0.5
1.0
2.5
7.5
15.0
25.0
50.0
100.0
Average 0-140 cm
Average 0-160 cm
20.1
No data
21.0
18.0
18.9
20.5
19.5
17.7
18.73
18.60
III.2.2. Scenario 2a:
Soil moisture :
For all fields, we assumed that the whole soil matric potential vertical profile was at the same value and that the initial moisture content is equal
to the average measured value. The following values should be used.
101 wheat:
101 bare soil:
DoE 387: h=-3.427 m =0.3805 m3 m-3
DoE 626: h=-59.10 m =0.2751 m3 m-3
28
DoE 387: h=-2.57 m =0.3865 m3 m-3
DoE 519: h=-13.40 m =0.3076 m3 m-3
DoE 389: h=-5.772 m =0.3624 m3 m-3
DoE 485: h=-359.32 m =0.2316 m3 m-3
120 irrigated wheat: DoE 402: h=-5.02 m =0.3697 m3 m-3
DoE 464: h=-6.034 m =0.3615 m3 m-3
121 sunflower:
DoE 509: h=-15.712 m =0.321 m3 m-3
214 spring wheat:
DoE 443: h=-12.59 m =0.3476 m3 m-3
501 sunflower:
DoE 558: h=-25.22 m =0.1702 m3 m-3
102 bare soil:
102 sunflower:
203 alfafa:
Soil temperature :
Soil temperature profiles are initialised at 0h10 . We assumed that the surface temperature was equal to the air temperature at the meteorological
site and that soil temperature was computed using equation (20) with the coefficients given in Table 21. Linear interpolation between the
temperature level given below can then be used.
DoE
387
389
402
443
464
485
509
519
558
626
Tsurf
6.2
7.7
0.5
15.0
5.1
16.6
11.7
14.8
16.2
12.9
T –50 cm
7.3
7.3
7.3
9.5
11.6
14.2
17.2
18.3
21.4
19.6
T –100 cm
8.9
8.8
8.6
9.6
11.2
13.2
15.6
16.6
19.7
19.4
29
T-140 cm
10.0
9.9
9.5
9.9
11.0
12.6
14.7
15.6
18.5
19.2
T-200 cm
11.1
11.0
10.6
10.7
11.5
12.7
14.4
15.1
17.5
18.3
III.2.2. Scenario 2b:
Soil moisture :
For all fields, we assumed that the whole soil matric potential vertical profile was at the same value.
For Fields 101 (Wheat period), 102 (bare period), 120, 203, 214 we start the simulation a few days after a long period of rain. We assumed that
fields are at field capacity (h=-3.3 m). If the soil moisture is needed, one must take the soil moisture given by pedotransfer functions for field
capacity (see Table 2).
For the other fields we made the following hypothesis:
101 bare soil : The soil was dried by the wheat. When the wheat was harvested we assumed that the soil moisture was at the wilting point. Then
after we assume the rain only rewetted the top 50 cm. The initial profile is then :
0-50 cm :
h=-10 m
>50 cm
h=-150 m
102 Sunflower period, 121 : the sowing occurred in dry conditions. We assumed that the drying processing only affected the top 30 cm and
below the soil remained at the field capacity.
0-30 cm
h=-10 m
>30 cm
h=-3.30 m
501 : Sunflower was well developed at the beginning. The water storage was about 200 mm. Most of it was likely used during the period of 80
days between sowing and the installation of the measurements. Consequently, we assumed that h=-100 m over the whole profile.
Soil temperature :
As in scenario 2a.
30
IV. BOTTOM BOUNDARY CONDITIONS
IV.1. Soil moisture and soil pressure
IV.2.1. Scenario 1
The soil moisture reported here were those given by the neutron probes within the 130-140 cm layer with the exception of the 501 fields
where we took the measurements made in the 140-150 cm layer. Measurements were generally made between 8 TU an 16 TU. Since the moisture
variations were slow, we recommend to make linear interpolation to retrieve the soil moisture at the lower boundary at the appropriate time step.
Soil matric potential derived using retention curves provided in Table 1 are also provided both for uniform and non-homogeneous soils.
Measured values of soil matric potential are provided in Appendix. They were not used in the framework of the intercomparison to avoid
discrepancies between models due to uncertainty on estimated retention curves.
The use of a larger soil column might be relevant only for fields where it can be assumed that the rooting depth went below 140 cm (i.e.
the fields where the tensiometers were out of range). Only field 101 (wheat), field 102 (sunflower) and field 203 (alfafa) might be concerned. In
this case, the following bottom boundary condition could be used:
- field 101 (wheat) 200 cm depth : zero flux
- field 102 (sunflower) 200 cm depth: zero flux
- field 203 (alfafa) 600 cm depth: depth of the water table, i.e. h=0 at the bottom of the soil column.
Table 18 : Fields 101, 102, 203. Time evolution of the soil volumetric water content (m3/m3) and estimated soil matric potential (m) for both
uniform and non-homogeneous soil. Void cells means that no measurements were made. For Field 203, only soil moisture at 130-140 cm depth is
provided as a larger soil column of 6 m was used.
DoE
101 (Wheat and 101 (Wheat and 101 (Wheat and 102 (Bare soil
102 (Bare soil
102 (Bare soil
203 (alfalfa)
Bare soil)
Bare soil)
Bare soil)
and Sunflower) and Sunflower) and Sunflower)
Soil moisture
Soil moisture
Soil matric
Soil matric
Soil moisture
Soil matric
Soil matric
potential
potential non
potential
potential non
Uniform soil
homogeneous
Uniform soil
homogeneous
soil
soil
387
.3842
0
-3.25
.3528
-4.19
-3.25
389
.3440
31
393
397
401
402
408
417
422
423
432
436
443
450
457
464
471
478
485
493
499
500
509
519
520
526
527
535
536
541
548
555
562
.3866
.3911
.3854
.3855
.3849
.3835
0
0
0
0
0
0
0
0
0
0
0
0
0
.3815
.3828
.3819
.3786
0
0
0
-1.42
0
0
0
0
.3707
.3610
.3428
.3277
.3135
.3140
-3.08
-4.75
-8.31
-12.40
-17.88
-17.65
0
-1.04
-2.70
-4.27
-6.26
-6.19
.3576
.3560
-3.61
-3.80
-1.49
-1.69
.3458
.3472
.3560
.3544
.3500
.3528
.3560
-3.80
-3.99
-3.80
-4.19
-3.80
-.169
-1.85
-2.14
-3.25
-1.69
.2790
-44.99
-15.79
.3479
-4.80
-4.37
.2831
-40.12
-14.10
.3473
-4.89
-4.50
.3460
-5.07
-4.80
.3471
.3451
.3435
.3337
-4.92
-5.19
-5.41
-6.92
-4.56
-4.99
-5.32
-7.48
.3314
.3454
.3459
.3466
.3441
.3428
.3427
.3351
.3197
.2967
.2778
.2657
.2620
.2576
.2453
.2268
.2281
.2886
.2859
-39.59
-37.16
-13.91
-1306
32
.2300
.2275
.2288
.2281
.2287
567
578
591
597
613
619
622
626
632
633
634
640
647
648
660
673
682
703
.2553
.2498
.2499
.2444
-48.31
-56.40
-56.12
-65.56
-57.42
-67.90
-66.65
-77.82
-65.73
-56.26
-78.02
-66.82
.3062
-21.59
-7.59
.2444
.2498
.3058
-21.80
-7.67
.2508
-54.86
-65.17
.3070
.3087
-21.15
-20.25
-7.43
-7.12
.2529
-51.66
-61.39
.2553
-48.43
-57.6
.2281
.2281
.2281
.2287
.2293
.2261
.2250
.2275
.2253
.3075
.3075
.3087
.3087
-20.89
-20.89
-20.25
-20.25
-7.35
-7.35
-7.12
-7.12
Table 19 : Fields 120, 214. Time evolution of the soil volumetric water content (m3/m3) and estimated soil matric potential (m) for both uniform
and non-homogeneous soil. Void cells means that no measurements were made.
DoE
120 (Irrigated
120 (Irrigated
120 (Irrigated
214 (Spring
214 (Spring
214 (Spring
wheat )
wheat)
wheat)
wheat)
wheat)
wheat)
Soil moisture
Soil matric
Soil matric
Soil moisture
Soil matric
Soil matric
potential
potential non
potential
potential non
Uniform soil
homogeneous
Uniform soil
homogeneous
soil
soil
402
.3723
-2.62
-2.62
408
.3749
-2.10
-2.10
417
.3738
-2.33
-2.33
422
.3735
-2.38
-2.38
33
423
432
436
443
450
452
457
464
465
471
478
485
493
499
500
509
519
520
526
527
535
536
541
548
555
.3774
.3738
.3756
-1.50
-2.33
-1.93
-1.50
-2.33
-1.93
.3717
-2.73
-2.73
.3650
.3696
-3.72
-3.16
-5.91
-5.03
.3665
-3.53
-5.62
.3705
.3714
.3650
.3675
.3664
.3596
-3.06
-2.95
-3.72
-3.41
-3.55
-4.43
-4.87
-4.70
-5.91
-5.43
-5.64
-7.03
.3419
.3303
-7.35
-10.10
-11.64
-15.96
.3753
-2.01
-2.01
.3753
.3746
.3735
.3735
.3741
-2.01
-2.15
-2.38
-2.38
-2.25
-2.01
-2.15
-2.38
-2.38
-2.25
.3729
-2.50
-2.50
.3714
-2.78
-2.78
.3728
-2.52
-2.52
.3245
-11.84
-18.68
.3729
.3700
-2.50
-3.05
-2.50
-3.05
.3261
.3275
.3329
.3336
-11.33
-10.90
-9.41
-9.23
-17.89
-17.22
-14.88
-14.60
34
Table 20 : Fields 121, 501. Time evolution of the soil volumetric water content (m3/m3) and estimated soil matric potential (m) for both uniform
and non-homogeneous soil. Void cells means that no measurements were made. Take care: for filed 501 the considered depth is 160 cm.
DoE
121 (Sunflower) 121 (Sunflower) 121 (Sunflower) 501 (Sunflower) 501 (Sunflower) 501 (Sunflower)
Soil moisture
Soil matric
Soil matric
Soil moisture
Soil matric
Soil matric
potential
potential non
potential
potential non
Uniform soil
homogeneous
Uniform soil
homogeneous
soil
soil
509
.3830
-2.04
0
520
.3875
-1.68
0
526
.3846
-1.92
0
536
.3868
-1.73
0
541
.3814
-2.17
0
548
.3789
-2.38
-0.72
555
.3848
-1.89
0
558
.3109
-4.86
-7.94
562
.3859
-1.81
0
567
.3798
-2.30
-0.29
.3064
-5.20
-8.51
578
.3684
-3.29
-2.49
.2874
-6.98
-11.45
591
.3643
-3.69
-3.02
.2852
-7.23
-11.87
597
.3635
-3.77
-3.13
.2878
-6.97
-11.38
606
.3509
-5.21
-4.84
.2278
-20.12
-32.96
611
.3458
-2.92
-4.71
613
.3526
-4.99
-4.59
619
.3529
-4.96
-4.55
626
.3525
-5.00
-4.60
635
.3488
-5.49
-5.15
IV.1.2. Scénario 2.
For Field 101 (bare soil) we assume a constant water potential in time: h=-150 m
For Field 501 we assume a constant water potential in time: h=-100 m
For the other fields, all fields we assume a constant soil water potential corresponding to the field capacity (h=-3.33 m)
35
IV.2. Soil temperature.
A sinusoidal function for the soil temperature at the bottom of the soil column given by (20) might be used for both scenarios 1 and 2.
The annual cycle of the temperature at depth z can be written:
  DoE  phase( z )  
T ( z )  Tm ean( z )  Tam p( z ) sin  2 
 
365.25

 
(20)
Then, the temperature at another depth z2 can be deduced by:
 z  z    DoY  phase( z )  z2  z 

(21)
T ( z2 )  Tm ean( z )  Tam p( z ) exp   2
 sin  2 

D   
365.25
D 


  
365.25 * 86400
where
is the soil damping depth (m) and  
is the soil diffusivity (m2 s-1).
D
Ch  

leading to the following relationships:
 z z
Tam p z2   Tam p z exp   2

D 

z  z 365.25
phase z2   phase z   2
D
2
(22)
(23)
Parameters Tmean(z) was calculated using non-linear optimisation on the daily soil temperature series measured at 1 m on the
meteorological site because the data were covering the whole year, leading to: Tmean(z =14.55 °C
for a depth z=1.0 m
Unfortunately the series of the meteorological site at 50 cm was exhibiting some inconsistencies and the analysis could not be performed
at the meteorological site. Field 101 was used instead and Tamp(z) and phase(z) were estimated using non-linear fitting using Tmean(z =14.55 °C
leading to:
Tamp(z )= 6.00°C
phase(z) = 133.24
36
The average error on field 101 was –0.51°C and the root mean square error was 0.92°C at 1m depth. The consistency of those values was
tested on 203 using daily soil temperature series measured at depth z=1.O m leading to an average error of 0.16 °C and a root mean square error
of 1.02 °C for field 203. These results were satisfactory.
Daily soil temperature at 0.5 m depth (field 101) were then used to infer the value of the average annual D parameter, using equations (22)
and (23). Equation (22) led to a value D=2.68 m and Equation (23) to a value of D=2.69 m. An average value D= 2.685 m was retained and is
associated with a diffusivity =1.46 10-6 m2 s-1. It led to the following parameters for depth 0.5 m:
Tmean(z) =14.55 °C
Tamp(z)= 7.32 °C
phase(z) = 122.42
for a depth z=0.5 m
Once again, the consistency of those values was tested on fields 101 and 203 using daily soil temperature series measured at depth z=0.5
m leading to an average error of -0.61 °C for field 101, -0.31°C for field 203 and a root mean square error of 1.20 °C for field 101 and 0.77 °C
for field 203. The agreement was therefore quite good. Given the similarity in thermal properties obtained for fields 101, 102, 203, 120, 121, 214,
it was assumed that the values of these parameters could also be used for these various fields.
It was therefore assumed that the value of D= 2.685 m estimated on field 101 data could be used for all the fields and Eqs (22) and (23)
used to estimate the parameters of Eqs (20) at various depths. Values are summarised in Table 21.
Table 21: Values of soil temperature average, amplitude and phase at various depths, to be used in a sinusoidal function, as a soil temperature
lower boundary condition.
Depth (m)
0.5
1.0
1.4
1.6
2.0
5.0
6.0
Tmean(z) (°C)
14.55
14.55
14.55
14.55
14.55
14.55
14.55
Tamp(z) (°C)
7.32
6.00
5.20
4.80
4.13
1.35
0.93
phase(z)
122.42
133.24
141.90
146.23
158.89
219.84
241.49
37
V.
MAXIMUM ROOTING DEPTH
It was observed that, for a given depth, soil moisture remained constant for a while and then began to decrease quite rapidly. It was
assumed that the change in moisture content was due to root extraction and the maximum rooting depth assigned to the depth corresponding to
this change. This led to the following rooting depth evolution for the various fields (Table 22)
Table 22: Time evolution of the maximum rooting depth for fields 101 (wheat), 102 (sunflower), 120 (irrigated wheat), 121 (sunflower) and 214
(Spring wheat).
Field 101 (Wheat)
Field 102 (Sunflower)
Field 120 (Irrigated wheat)
Field 121 (Sunflower)
Field 214 (Spring wheat)
DoE
Max rooting
DoE
Max rooting
DoE
Max rooting
DoE
Max rooting
DoE
Max rooting
depth (m)
depth (m)
depth (m)
depth (m)
depth (m)
387
0.10
519
0.15
402
0.15
509
0.10
443
0.10
408
0.15
548
0.30
422
0.25
541
0.35
450
0.30
417
0.25
555
0.70
432
0.40
548
0.70
457
0.60
422
0.35
562
1.10
436
0.65
555
0.95
465
0.75
432
0.40
578
1.35
443
0.75
597
1.15
471
0.85
436
0.65
600
1.50
493
0.85
606
130
478
0.95
443
0.75
499
1.00
635
1.30
485
1.10
450
0.85
509
1.15
493
1.25
460
1.10
537
1.15
499
1.35
464
1.35
557
1.35
527
1.65
Field 203: The alfafa was well established when the measurements began. It can be assumed that the rooting depth is constant and equal
to 4.9 m
Field 501: The sunflower was already well established when the measurements began (80 days after sowing). It can be assumed that the
maximum rooting depth is constant throughout the simulation period and equal to 1.4 m depth.
38
APPENDIX: Measured values of soil matric potential for initial and boundary conditions
AI: Initial conditions.
Table A1.1. Initial values of measured soil matric potential (m). No data were available for field 101 bare soil (DoE 626), field 203 (DoE 485)
because tensiometers were out of range. No tensiometers were installed on field 102 bare soil (DoE 387) and field 501 (DoE 558).
Depth (cm)
Field 101
Field 102
Field 203
Field 120
Field 120
Field 121
Field 214
Wheat
Sunflower
Alfafa
Irrigated wheat Irrigated wheat
Sunflower
Spring wheat
DoE 387
DoE 519
DoE 389
DoE 402
DoE 464
DoE 509
DoE 443
10
0.03
Out of range
-0.02
No data
No data
No data
No data
20
0.13
-5.41
-0.04
-0.10
-0.13
-4.64
-2.38
30
0.23
-3.76
-0.04
No data
No data
No data
No data
50
0.43
-1.39
0.38
0.21
0.01
-1.46
-0.28
80
0.57
-0.42
0.68
0.52
0.27
0.00
-0.01
110
0.90
-0.27
1.04
0.78
0.63
0.14
0.04
130
0.86
-0.12
1.24
0.99
0.83
0.34
-0.04
A2. Boundary conditions
The following tables provides the time evolution of the soil water pressure at 130 cm.
39
Table A1.2: Time evolution of the soil matrix potential at 130 cm depth for fields 101, 102, 214 and 120
Field 101 (Wheat)
Field 102 (Sunflower)
Field 214 (Spring wheat)
DoE
Soil water
DoE
Soil water
DoE
Soil water
pressure (m)
pressure (m)
pressure (m)
345
0.08
507
-0.02
439
-0.19
346
0.40
509
-0.10
443
-0.04
351
0.39
511
-0.19
446
-0.14
358
0.11
516
-0.13
449
-0.14
365
0.06
519
-0.12
450
-0.10
372
0.68
526
-0.14
451
-0.10
378
0.58
528
-0.11
42
-0.08
380
0.37
529
-0.09
457
0.00
387
0.86
530
-0.09
465
-0.08
388
0.40
533
-0.17
471
-0.10
390
0.26
535
-0.11
472
-0.49
391
0.52
537
-0.09
484
-0.75
393
0.30
541
-0.15
485
-0.54
394
0.24
547
-0.17
488
-0.75
395
0.26
548
-0.15
493
-0.94
396
0.18
549
-0.17
497
-0.54
397
0.14
551
-0.17
498
-0.63
402
0.22
554
-0.19
499
-0.72
403
-0.34
555
-0.22
500
-0.58
408
0.36
556
-0.25
501
-0.49
409
0.48
562
-0.59
502
-0.79
416
0.14
567
-5.32
507
-0.98
418
0.26
568
-6.10
509
-0.69
420
0.00
->649
Out of range
516
-1.59
422
0.08
519
-2.09
429
0.34
526
-2.22
432
0.26
527
-2.28
436
0.08
530
-2.42
40
Field 120 (Irrigated wheat)
DoE
Soil water
pressure (m)
403
0.99
408
0.93
409
1.07
416
0.87
417
0.85
422
0.87
429
0.81
432
0.77
436
0.65
439
0.53
443
0.44
446
0.51
449
0.53
451
0.39
452
0.41
457
0.06
461
1.12
464
0.83
471
0.77
472
0.68
473
0.51
477
0.65
478
0.44
484
0.51
485
0.44
487
0.31
488
0.20
493
0.26
439
443
446
449
450
451
453
457
464
470
471
477
478
484
->542
0.02
0.37
-0.07
0.12
-0.42
0.08
0.16
-0.51
0.02
-0.88
-1.52
-4.74
-5.22
-6.58
Out of range
533
535
536
537
541
547
549
554
555
Table A1.3: Time evolution of the soil matrix potential at 130 cm depth for fields 121 and 203.
Field 121 (Sunflower)
Field 203 (Alfafa)
DoE
Soil water
DoE
Soil water
pressure (m)
pressure (m)
509
0.34
378
0.98
511
0.07
380
1.00
516
0.01
390
1.24
520
0.22
391
1.19
526
0.11
393
1.16
530
0.15
394
1.02
533
0.13
397
1.02
536
0.17
401
0.97
537
0.11
408
0.98
541
0.07
409
0.98
547
0.09
416
0.45
41
-2.78
-2.82
-2.99
-2.89
-2.93
-3.05
-3.33
-3.56
-3.68
497
498
499
501
502
507
509
511
516
520
526
530
533
535
536
0.17
0.06
0.03
0.25
0.14
0.32
0.16
-0.14
0.04
0.28
0.16
-0.04
0.06
0.00
-0.21
548
554
555
556
562
567
568
569
572
575
578
582
590
603
606
610
613
626
633
-0.03
-0.01
0.06
0.13
-0.17
-0.09
-0.21
-0.12
-0.15
-0.27
-0.13
-0.48
-1.73
-3.72
-4.19
-5.13
-5.43
-5.06
-5.07
417
422
429
432
436
439
443
446
449
450
451
452
457
464
-> 634
0.41
0.34
0.42
0.21
0.41
-0.09
-0.02
-0.34
-0.42
-0.40
-0.70
-0.64
-1.99
-6.41
Out of range
42
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43