Figure 7. C
volume Co
4.3 Soil wa Figure 8 sho
P
n
. The time with a decre
Time depend
In Eq. 11, t Comparison o
mparaison d
ater storage ows the tem
e gradient of ease in |
P
n
|. dency of
m
f
the co-efficie
of observed
des valeurs o du volu
poral variatio
m
, d
m
dt , i
for each P
n
c
ents, s
and u
s
. 4
u
and calculat
observées et ume de sol m
ons in the vo
s very small can be expre
m
u
are given in
08 .
n
P s
1 .
35 .
2
n
P
ted temporal calculées de
mouillé
olumetric wa for
t 72 ho
essed by for
s
ut
terms of P
n
09 .
07 .
1
n
P
variations in es variations
ater content, ours but tend
r 24 ≤ t
≤ 72 h
as follows: n wetted soil
s temporelles
m
, for every
ds to increase hours:
11
12
13 s
y e
Figure 8. Temporal variations in volumetric water content
Les variations temporelles de la teneur en eau volumétrique Finally,
M
soil
is calculated by the following equation:
wet m
w soil
V M
14
where
w
is the density of water.
Figure 9 shows the observed
M
soil
obtained from the electric balance reading and M
soil
calculated by substistuting Eqs. 4 and 11 into Eq. 14. Initially, M
soil
increased remarkably with
t and then the time increment of
M
soil
gradually became small. Both the observed and calculated
M
soil
are in good agreement with each other.
0.02 0.04
0.06 0.08
0.1 0.12
10 20
30 40
50 60
70 80
Elapsed time, t
hour Volum
etric w ater
conte nt
for w ett
ed soil
volum e,
Ѳ
m
P
n
m -0.02 -0.07 -0.10 Symbol
Figure 9. C
storage Co
4.4 Evapor
Figure 10 sh porous pipe
variation in A
hours:
where c
1
= 1
Figure 11 sh linear relatio
dM
heva
dA
we
small with th
When the s following eq
Comparison omparaison d
ration
hows the rel and
t. A
wet
i A
wet
is descri
10
-6
and
hows the re on to
A
wet
a
et
means the he increase in
oil surface i uation:
of observed des valeurs o
de stock lation betwee
ncreased wit bed by the fo
0003 .
d
lation betwe approximatel
e evaporation n |
P
n
| and is
m
s wet, the e
M and calcula
observées et kage de leau
en the wette th a decreas
ollowing linea
t c
A
wet
1
0005 .
3
n
P
en evaporat y, regardles
n mass flux, given by the
58 .
4
heva
P m
evaporation r
hev heva
m M
ted tempora
t calculées le u du sol
ed soil surfac se in |
P
n
| at t ar equation f
d
0167 .
n n
P
tion rate, M
h
ss of P
n
. Th ,
m
heva
. The e following eq
58 .
n
P
rate, M
heva
, c
wet va
A l variations in
es variations
ce area, A
we
the same t
. T for every
P
n
f
2
heva
and A
wet
. he gradient
value of m
h
quation:
can be calcu n soil water
temporelles
et
, around th The tempora
for 24 ≤ t
≤ 72
15
16 .
M
heva
has a of
M
heva
, i.e
heva
becomes
17
ulated by the
18 e
al 2
5
6 a
e. s
e
8
In order t made in t
1. a
2. T c
The values o respectively
Figure 10. T
Figure 12 illu wetted soil s
Figure 12 c
respectively these three
the calculati the critical S
Figure 11.
to calculate t this study.
Evaporation appearance
The appear commencem
of t
i
observed .
Temporal var ustrates the
surface, i.e. correspond t
. Since the d values [=
M on of
M
eva
w SWS in this p
Relation betw entre le t
the temporal from the
of the wetted ance time o
ment time of e d were 4, 8
riations in we dans le
decision pro M
c
according
to
M
c
at ob deviations be
M
c1
+ M
c2
+ M
c3
was started a paper.
ween evapo aux d’évapo
variation in soil surfac
d soil surface of the wette
evaporation, and 16
hour
etted soil sur e sol mouillé s
ocedure of M
g to the abo served
t
i
fo etween
M
c1
, 3] was ado
at time t
= t
ic
ration rate a ration et la s
M
eva
, the foll e begins s
e. ed soil surfa
t
i
. rs for
P
n
= - 0
rface area L surface
M
soil
required f ove assumpt
r P
n
= - 0.0 M
c2
and M
c3
opted as M
c c
when M
soil
nd wetted so surface de so
lowing assum simultaneous
ace is the s 0.02, - 0.07a
es variations for the appea
ions. M
c1
, M
02, - 0.07 a
3
were small, = 0.014 kg
l
reached M
c
oil surface ar
ol humide
mptions were sly with the
same as the and - 0.10 m
s temporelles arance of the
M
c2
and M
c3
in and - 0.1 m
the mean o . As a result
c
. M
c
is called
rea Relation e
e e
m,
s e
n m,
of t,
d
Figure 12. Decision procedure of critical soil water storage Procédure de décision de
stockage en eau du sol critiques
Figure 13 shows the comparision of the observed
M
eva
and calculated one. After substituting Eqs. 15 and 17 into Eq. 18,
M
eva
was calculated by the following equation:
t t
heva eva
ic
dt M
M
19
It is seen that there is little discrepancy between the calculated M
eva
and the observed one for every
P
n
even though the maximum difference between t
i
and t
ic
was about 5 hours see Figure 12.
Figure 13. Comparison of observed and calculated temporal variations in evaporation
Comparaison des valeurs observées et calculées les variations temporelles de lévaporation
4.5 Supplie
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