Nepalese society is cast based discriminatory and patriarchal where women are subjugated both economically and physically. Poverty is rampant among lower cast
but not limited to them.
1.1 Overall Irrigation Status
Total cultivatable land in Nepal is about 2640 thousand hectares, out of which only 1766 thousand hectares is categorized as irrigable. Remaining 874 thousands
hectare are non irrigable as conventional irrigation schemes are unfeasible for these areas.
Inclusive of irrigation systems for 636 thousand hectares developed by farmers themselves irrigation infrastructures are already built for total 1252 thousand hectares
which is 47 of total agriculture land and 71 of total irrigable land. Almost 50 of theses irrigation systems built by farmers have received government assistance for
upgrading and maintenance. Only 46 of irrigated land or 22 of total agricultural land has year round irrigation facility.
2.1 Non Conventional Irrigation System: Nepalese Context
2.1.1 Objective of the NITP
Objective of the NITP is to implement the micro-irrigation program for disadvantaged group, marginal land and farmers, severely water deficit areas and provide an
effective micro-irrigation service delivery mechanism with high value crop production support for poverty alleviation.
2.1.2 Non conventional irrigation system
Water acquisition and its application, if both of them or any one of them, is not conventional in nature than it is non conventional irrigation system. Hence, irrigation
system which includes one or more than one of the following components is non conventional irrigation system.
1. Drip 2. Sprinkler
3. Treadle Pump Manually by feet operated ground water extracting machine 4. Low cost water storage Thai jars, soil-cement or plastic lined tanks
5. Rain water harvesting
2.2 Project Area, Priority, Budget and Present Status
The sub projects are scattered throughout Nepal. Based on experiences gained so far it has been observed that non conventional irrigation schemes are most useful and
necessary for mid hill and inner terai area between mid mountains and Chure. But developments of non conventional irrigation sub projects are not restricted to these
areas only. While treadle pumps are used in terai, schemes with drip and sprinkler technologies are being promoted mainly in mid mountain and hills.
Positive discrimination is accepted in selection criteria of NITP. Priority is given to the areas inhabited by marginalized poor community with no potential for future
development of conventional irrigation. Similarly access to market or potential for future market development in nearby areas is assessed.
Total budget allocated to NITP has gradually increased from US 0.54 million for the FY 200708 to US 1.46 million for the FY 2010011. While total estimated cost of 223
ongoing projects is US 6.2 million only US 1.46 million is allocated in this fiscal year. Nearly 94 of the allocated budget is used for civil works of project.
At present 223 sub projects in 74 districts
2
A. Simple Drip
with total command area 3300 ha are under construction. It is expected that 40 of these projects will complete by the end of
fiscal year 201011 providing irrigation to additional 501 hectare of land. About 90 of the sub projects have command area less than 20 ha.
Already completed 135 projects, with total expenditure of US4.2 million, in 44 districts can irrigate about 2558 ha. if utilized properly as most of the projects are
intended for drip irrigation schemes and designed accordingly.
Simple drip system is very simplified form of modern drip technology. Holes are punched in 8mm lateral pipes to act as emitters. Pressure is generated by placing
tank capacity 60 ltrs about 1 meter above the ground.
B. Micro Sprinkler
Micro sprinkler have very small coverage of about 4 meters in diameter. They can be operated under 7 to 10 meter head. Small area of coverage is specially suited for
small terraces in mountains.
Table 1: Cost of Simple Drip and Micro Sprinkler System
System Size
Irrigation Capacity
Retail Price WithoutWith tank
3
Remarks US
Simple Drip System Very small
90 sqm 10.76-14.13
4 Drip lines Simple Drip System
Small 125 sqm 15.45-18.98
6 Drip lines Simple Drip System
Medium 250 sqm 27.74-31.34
8 Drip lines Micro Sprinkler
System Small
250 sqm 11 4 risers
Mini Sprinkler System
Small 250 sqm 9.63
2 risers
Apart from NITP different INGOs are also involved in micro irrigation development Table 2. Some of these organizations which were active even before government
started its initiative are still active in micro irrigation development in Nepal.
2- There are 75 districts in Nepal. 3- HDP tank of size 50 ltrs
Table 2 :
Different Organizations Involved in Micro Irrigation Development and their contribution
S. No. Organization
Hectare House Holds
Hectare per HH 1
ADBN
4
28987 29035
0.998
2
IDE
5
9815 119406
0.082
3
SISP
6
2280 7800
0.292
4
NITP
7
2558 6800
0.376
5
DEPROSC
3
1211 4139
0.293
6
SAPROS
3
335 3852
0.087
7
MDI
3
168 1001
0.168
8
CEAPRED
3
129 741
0.174
9
VDRC
3
21 229
0.092
10
HELVETAS
2
5 27
0.185 45509
173030 0.262
Comparatively larger average landholding per household in ADBN invested areas is clear indication of undue influence by comparatively wealthy farmers to government
agency. Contrary to this in the projects developed by INGOs majority are small farmers as indicated by average land holding size. This is one of the reasons behind
the success of their initiative.
3. Beliefs and Achievements of NITP
NITP firmly believes that development is a right not a generosity. For NITP Development is not only a matter exclusively of economic growth and increase in
gross domestic product. Projects of this size do not have substantial impact in GDP. NITP firmly believes that genuine change is most often rooted in small communities of
poor people and NITP can play very important role in this change. Hence, all neglected areas and communities are primary target of NITP development.
NITP believes in positive discrimination and attention to vulnerable group. Affirmative action is needed to correct, offer remorse and compensate for neglect and seclusion
of disadvantaged group since historical times. Obviously positive discrimination is their right, not plead for sympathy. For NITP all those who cannot claim their rights or
are voiceless are potential beneficiaries as it is not a matter of cast but it is state of being powerlessness resulting from poverty and lack of education which are proving
to be more detrimental for the cause of social justice.
Social inclusion and women empowerment are other two areas of major achievements of NITP’s micro irrigation schemes. Objective of social inclusion is
being achieved through overall participatory process. Through this process decisive participation of all irrespective of their cast, race, religion, gender and economical
status is ensured in each stages of development. Mandatory provision of 35 percent women in WUAs Water Users Association executive committee is helping in
womens empowerment by installing confidence in them and providing opportunity for leadership. At the same time this process is successfully creating awareness among
the disadvantaged group poor, women, lower cast and ethnic group in the community, helping them to organize, empowering them for decision-making so that
4- ADBN: Agriculture Development Bank Nepal semi government organization 5- International Non Governmental Organizations
6- Local Non Governmental Organizations 7- Non Conventional Irrigation Technology Project
they can identify and prioritize their needs. It is also building up users capacity for preparation, implementation, operation and management of subprojects in other
areas as well to enhance their livelihoods. Users committee is providing platform to disadvantaged group to mingle with others,
which is invaluably instrumental in raising their level of self confidence. In addition to this the democratic process adopted in electing executive members of WUA is
another important feature helping in social inclusion. Leadership ability and sense of economic independence are very important in
womens empowerment as these two factors have direct impact on individual identity, dignity, self respect and social standing. Leadership ability comes from knowledge
and capability to demonstrate and implement such knowledge. NITP is instrumental in increasing womens confidence level by giving them leadership opportunity through
WUA, improving their leadership quality by involving them in various micro irrigation and agriculture related trainings, participation in user’s committee activities,
interaction programs and introducing sense of freedom in them by including them in away from home farmers tour program. Economic independence is achieved
through control over resources i.e. by selling agro products and controlling the returns. In small micro enterprises such as small micro irrigation supported
agricultural activities women benefit in particular, because their say over the output of homestead based activities tends to be stronger than for other sites of agricultural
production.
4. Scope for non conventional irrigation schemes
The potential agricultural land area for non conventional irrigation development in Nepal is around 1000 thousand hectare which is summation of non irrigable and
under irrigated land. Further, it is possible to increase irrigation capacity of present irrigation infrastructures drastically with adoption of efficient drips and sprinklers for
water application. Nepal being a mountainous country with fragile geology poses tremendous challenge
from stability point of view. Landslides, slope failure, rock fall or any other form of soil mass movement is common along the canal alignment both due to natural cause and
due to human intervention. As pipe is used for water conveyance in Non conventional systems it requires very little excavation works hence induces less disturbance to
natural geomorphology. This makes such schemes more appropriate in Nepalese context.
Areas under cultivation in hill and mountain region are either terraced or sloppy land. Soil erosion rate is high from such areas which is further aggravated by conventional
surface irrigation. Irrigation technologies which use small quantity of water such as drip and sprinkler are helpful to mitigate soil erosion from such land.
Seepage and deep percolation loss is high because of high porosity and shallow depth of soil in mountainous region. Drip and sprinkler are most appropriate
application technologies to minimize the loss of water as well as nutrients. The economical status of majority of people and average land holding per family has
further made micro irrigation more relevant.
5. Problems in Micro Irrigation Development in Nepal
The problems associated with micro irrigation development are of varied nature as technologies are new for Nepalese farmers. Capacity of the drip and sprinkler sets, its
coverage, prior knowledge about these technologies, farmers capacity to invest in these technologies etc are major hurdles in micro irrigation development. Farmers are
unaware of effectiveness of these technologies. Moreover farmers who are
accustomed with flooding methods of irrigation have doubts about these systems meeting crop water requirement.
Drip sets developed in Nepal are of very small capacity as largest set can cover 1000 sq.m. Only Hence big farmers who have capacity to lead small farmers in vegetable
farming and marketing are not attracted towards it. These poor small farmers would have followed big farmers had they used these technologies.
Changing present cropping pattern which is being practiced since centuries is another major problem. Paddy cultivation has attained status of religion or culture. Hence
switching over to high value crops like vegetables is not taking place at desired pace? NITP is also facing serious problem of lack of budget. Budget allocated is minimal
compared to the coverage of NITP and large number of projects under construction. Due to unavailability of sufficient budget; even for such small projects; it is taking
more than anticipated time 1 to 2 years to complete. This is totally against most strong argument in its favor that is being small it can be completed in very short
period and benefit can be ripped immediately. Unwanted interventions by political leaders in project selection and compelling
executing agencies to implement unfeasible projects is also harming the progress of NITP.
6. Conclusion
Topography of the country, poverty level, land fragmentation etc makes it imperative to promote micro irrigation in Nepal.
The achievements of NITP in Socio-Economic sectors are indeed remarkable. Economic independence, leadership quality, self-identity and confidence, which are
key ingredients in achieving womens empowerment, are major moral boosting achievements. Similarly, NITP is playing very important and effective role in lessening
social discrimination, exclusion and seclusion of deprived and destitute populace. Development induced by NITP kind of projects are in real sense development with
human face where most deprived, marginalized and excluded sect of people are benefited and experience positive changes brought by it. These achievements in
Socio-Economic sectors are indeed remarkable. More training and motivational programs are needed to convince more farmers to
adopt these technologies and switch over to high value crop farming. Either by government or through INGOs with government support this initiative must continue.
References
1. Bhattarai, K. 2010. Non conventional Irrigation Technology Project: An Introduction. Irrigation News Letter. 58: 4-5.
2. Bhattarai, K, 2011, Climate Change and Non Conventional Irrigation Technologies, Irrigation News Letter, 60:4-7
3. Pandey, N. and Adhikari,D,L.,2007. Non conventional Irrigation Technology NIT An encouraging effort for Economic and Social Inclusion of the
Disadvantaged Poor, National Seminar Proceeding, PP 14-19
1- PhD Scholar, Environmental Heat and Hydraulics Laboratory, Department of Architecture and Civil
Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan; Telephone: 81-776278595, Fax: 81-776278746, E-mail: monir92usyahoo.com
2- Dr. of Eng., Professor, Environmental Heat and Hydraulics Laboratory, Department of Architecture and Civil Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan; Telephone: 81-
776278595, Fax: 81-776278746, E-mail: fukuharau-fukui.ac.jp 3- Dr. of Eng., Associate Professor, Dept. of Civil Engineering and Urban Design, Hiroshima Institute of
Technology, 2 -1-1 Miyake, Saeki-ku, Hiroshima 731-5193, Japan;
E-mail: ishiiycc.it.hiroshima.ac.jp 4- PhD Student, Environmental Heat and Hydraulics Laboratory, Department of Architecture and Civil
Engineering, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan
EFFECT OF NEGATIVE PRESSURE DIFFERENCE IRRIGATION ON SOIL WETTING PATTERN
EFFET DUNE IRRIGATION SOUS DIFFÉRENCE DE PRESSION NÉGATIVE SUR LE SOL MOUILLANT MOTIF
S. M. Moniruzzaman
1
, Teruyuki Fukuhara
2
, Yoshihiro ISHII
3
and Hiroaki Terasaki
4
ABSTRACT
Negative pressure difference irrigation NPDI is considered to be a highly efficient water saving method, which consists of a porous pipe and a water reservoir. The
water use efficiency of the NPDI is higher than that of other irrigation methods such as surface irrigation, sprinkler irrigation and drip irrigation. In order to investigate the
effect of negative pressure difference on the soil wetting pattern and water balance of the NPDI, laboratory experiments were carried out using a soil column in a
temperature and humidity controlled room. The supplied water M
sup
, soil water storage
M
soil
, evaporation M
eva
, wetted soil surface area and configuration of wetted soil around the porous pipe were measured for three different negative
pressures. Empirical equations were proposed for the calculation of wetted soil volume,
M
soil
, M
eva
and M
sup
. The proposed simple methodology could well reproduce the temporal variations in the
wetted soil volume, water use efficiency, M
soil
, M
eva
and M
sup
.
RÉSUMÉ ET CONCLUSIONS
Le manque d’eau est une contrainte majeure dans le domaine de l’agriculture en milieux arides et semi-arides. Le système d’irrigation sous différence de pression
négative NPDI pourrait être un des meilleurs moyens pour économiser cette eau étant donner qu’il dirige l’eau directement vers la racine de la zone visée. Le système
NPDI est composé dun tuyau poreux enterré verticalement dans un sol, un conduit dalimentation en eau et un réservoir deau. Le réservoir est placé à une hauteur
inférieure à celle du tuyau poreux de manière à obtenir une différence de pression négative, notée
P
n
, dans le tuyau poreux. Lorsque le potentiel matriciel, noté ψ, du
sol environnant est inférieur à la pression P
n
, l’eau va alors se déplacer du réservoir vers le tuyau poreux et s’écouler dans le sol environnant. Au contraire, lorsque
ψ est supérieur à
P
n
, l’écoulement s’arrête automatiquement sans aucune opération manuelle. La différence de pression entre
ψ et P
n
est le moteur de l’eau conduite par
le système NPDI. La présence d’un sol humide autour du tuyau poreux affecte l’efficacité de l’eau utilisée dans le domaine agricole. Cest pourquoi, il est important
de comprendre la relation entre la configuration du sol mouillé et P
n
au fil du temps lapprovisionnement en eau.
Ce document vise, dans un premier temps, à décrire l’influence d’une différence de pression négative sur un sol humide autour d’un tuyau poreux, et, dans un second
temps, à prédire une méthode simple d’équilibre de l’eau au sein du système NPDI. En vue datteindre lobjectif ci-dessus, un test déquilibre de leau du système NPDI a
été réalisée à une température et humidité ambiante contrôlée 25°C et 30, respectivement pour trois différents
P
n
-0,02 m, -0,07 m et - 0,10 m H
2
O.Une colonne de terre diamètre = 0,20 m et hauteur = 0,21 m a été remplie avec du sable
Kawanishi, celui-ci ayant une densité à sec de 1410 kgm3. Un tuyau poreux longueur = 0,1 m, rayon extérieur = 12,5 mm et épaisseur = 6 mm a été enterré
verticalement au centre de la colonne de terre. P
n
représente la différence de hauteur entre la surface de l’eau dans le réservoir et le milieu du tuyau poreux, comme le
montre la Figure 2. Deux balances électriques pesée minimum = 100 mg ont été utilisées pour mesurer simultanément la masse d’eau cumulée dans le réservoir,
notée M
sup
et la masse d’eau cumulée dans le sol, notée M
soil
. Par différence M
sup
– M
soil
, l’évaporation cumulée peut alors être déterminée, celle-ci étant noté M
eva
. Enfin, la terre sèche a été séparée de la colonne de terre dans le but d’évaluer la
configuration de la terre humide à t
= 24 h, t
= 48 h et t
= 72 h. Les principales conclusions tirées de cette étude sont les suivantes :
1 Précision de mesure des M
sup
et M
soil
a été assurée par le résultat, M
sup
= M
soil
, obtenu à partir dun test déquilibre de leau. Dans cet essai, léquilibre
de leau, lévaporation na pas été autorisée à partir de la surface du sol. 2 L’équation empirique pourrait concorder avec les résultats expérimentaux
concernant la variation du temps au sein de M
sup
, M
soil
et M
eva
, ainsi qu’avec l’expansion du temps d’humidité du sol.
3 L’efficacité de l’utilisation de l’eau = M
soil
M
sup
est comprise entre 1 et 0,92. De plus, l’efficacité accroit lorsque
P
n
diminue. 4 Cette méthode est efficace pour l’évaluation de l’équilibre de l’eau du
système NPDI.
1. INTRODUCTION
Water loss due to evaporation, deep percolation below the root zone and conveyance of water from the source to the agricultural field cannot be avoided in irrigation
systems. In a sprinkler irrigation system, spray losses can become as high as 45 under extreme weather conditions such as bright sunlight, high temperature and low
humidity Frost and Schwalen, 1955. Irrigation techniques that help save water are indispensable to regions and countries with limited water resources and severe
external evaporation conditions. The water wasted in the NPDI is less than that of the drip irrigation Yabe et al., 1986. NPDI system is a kind of subsurface irrigation and is
composed of a water reservoir and a porous pipe installed in soil. The water reservoir is placed at a lower elevation than the porous pipe to generate negative pressure,
P
n
. NPDI system may be divided into two categories according to the installation direction
of the porous pipe, i.e. horizontal and vertical installation. Most of the past studies on NPDI For example, Kato et al., 1982, Tanigawa et al.,
1988, Ashrafi et al., 2002 and Siyal et al., 2009 were dealt with soil wetting pattern around a porous pipe installed horizontally in soil. On the other hand, the soil wetting
pattern around a vertically installed porous pipe has been hardly investigated except two groups of researchers Peifu et al., 2004 and Akhoond et al., 2008. It can be
easily expected that the soil wetting pattern will be different for vertically installed porous pipe from that of horizontally installed porous pipe. Since the configuration of
the wetting front affects evaporation from the soil surface, it is important to examine the effects of the negative pressure on the temporal expansion of the wetting front.
Besides tha technique, i
system and discussed i
develop a s balance in a
In the NPD reservoir an
the soil wate than the neg
reservoir to surrounding
stops autom supplied wa
P
n
|. Saving which is in
wetting proc
Figure 1. M
Figure 2 s
temperature chloride pipe
with a heigh with Kawani
porous pipe was installe
Marriott tube the differenc
intermediate at, intelligent
including NP the water
n the past simple meth
a NPDI syste
2.
DI system, w d a porous p
er matric pot gative press
the porous soil. On the
matically with ater rate is
water can b proportion t
cess of the so
Mechanism of du système
3
hows a sc
e and humidi e diameter =
ht of 0.03 m ishi sand wit
length, l
= ed vertically
e in a water s ce in elevat
e elevation of t operation
PDI, would use efficienc
studies. Th hodology for
m with a vert
MECHAN
water moves pipe installed
tential herea sure in the p
pipe and th e contrary, w
hout any ar in proportion
be enhanced to the NPD,
oil progresse
f a negative p
e d’irrigation
. EXPERI
chematic dia ty controlled
= 0.20 m and each and u
th a bulk den 0.1 m, outer
in the cente supply tank w
tion between f the porous
and manag depend on
cy. The wat erefore, an
r predicting tically installe
NISM OF A
s in a wate d vertically in
after referred porous pipe,
hen percolat when
ψ is eq rtificial work
n to the neg d by the
NP lessens or
es.
pressure diff par différenc
IMENTAL
agram of th d room 25
°
C d height = 0
sed as a so nsity of 1410
r radius, R
p
= er of the so
was used to n the water
pipe b-b s gement of a
the water b ter balance
experiment soil wetting
ed porous pi
A NPDI SYS
r supply co n the soil as s
d to as matric P
n
, water m es through t
ual to or larg . The suppl
gative pressu PD because
becomes z
ference irriga ce de pressio
PROCEDU
he experime C and 30, r
.21 m was c il column. T
0 kgm
3
for a = 12.5 mm a
oil column a keep
P
n
con r surface in
see Figure 2 any subsurfa
balance in t has been, h
tal study is g pattern an
pe.
STEM
nduit that li shown in Fig
c potential, moves up fro
the porous ger than
P
n
, lied water p
ure differenc the
supplied ero automat
ation system on négative
URE
ental arrang respectively
composed o he soil colum
all experimen and thickness
as shown in nstant.
P
n
wa the reservo
. ace irrigation
the irrigation however, no
essential to nd the wate
nks a wate gure 1. When
ψ, is smalle om the wate
pipe into the the seepage
per unit time ce NPD, |
ψ d water rate
tically as the
Mécanisme
gement in a . A Polyviny
f seven rings mn was filled
ntal cases. A s,
t
p
= 6 mm Figure 2. A
as defined as oir a-a and
n n
ot o
r
er n
r r
e e
e ψ-
e, e
e
a yl
s d
A A
s d
Water was pump to rem
reading of 0 supply tank,
to measure t the other b
reservoir su intervals. Ev
M
sup
:
For easy ev was wrappe
accuracy te simple wate
the water ba 0.02, - 0.07
After measur removed fro
photograph visualized an
was collected was obtained
measured at
4.1 Measure Figure 3 sh
measureme i.e. the mea
during the co circulated be
move air bubb .1 g were pla
respectively the amount o
alance was upplied wate
vaporation fro
valuation of t ed so that ev
est. Conseq r balance of
alance test w and - 0.1m H
Figur
ring M
sup
and om the soil
in Figure 4 nd measured
d in a heat -p d by the grav
t three elapse
4
ement accu
hows the te nt accuracy
asurement e ourse of the
etween the bles in the si
aced under t y. The electri
of water stor used to me
er, M
sup
, sim
om the soil s
the measure aporation fro
quently, the f
M
sup
= M
soil
was carried H
2
0.
re 2. A Sche
Schéma d
M
soil
at the column whil
. Subseque with a came
proof tray and vimetric soil sa
ed time, t
= 24
4. RESUL
racy
emporal var test for
P
n
= error = |
M
sup
experiment. porous pipe
ilicon tube. T the soil colum
c balance pl red in the soi
easure the ultaneously.
surface, M
eva
su eva
M M
ement accura om the soil s
measureme
l
. After this m out for three
matic diagra a du test d’éq
end of the te e taking off
ently, the co era and a sca
d the volumet ampling meth
4, 48 and 72
TS AND D
riations in M
- 0.02 m. T
p
- M
soil
| M
sup
e and the re Two electric b
mn and unde aced under t
il, M
soil
soil w amount of w
All data we
a
, was given
soil up
M
acy of M
sup
a surface was p
ent accuracy measuremen
e different ne
am of a water quilibre de l’e
est, dry soil a f seven rings
onfiguration o ale, respective
tric water con hod. All data
hours.
DISCUSSIO
M
sup
he difference was negligi
servoir by u balances wit
er the reservo the soil colum
water storage water suppl
re recorded by subtracti
and M
soil
, the prevented m
y was evalu nt accuracy w
egative pres
r balance tes eau
around the we s one at a
of the wettin
ely. Finally, th
ntent of the w except
M
sup
a
ONS
and M
soil
e between M
bly small 1 using a smal
th a minimum oir and wate
mn was used e, SWS, and
ied from the at 60-minute
ing M
soil
from
1 e soil column
measuremen uated for the
was secured sures
P
n
=
st etted soil was
time see a ng front was
he wetted so wetted soil,
θ
m
and M
soil
were
0 for the M
sup
and M
soil
.4 or less ll
m er
d d
e e
m
n nt
e d,
-
s a
s il
m
, e
e
l
, s
4.2 Soil wet Figure 4 sho
0.10 m, resp A small pho
P
n
= - 0.02 horizontal pl
assumed to proposed fo
The volume
where r
is th R
m
is the correspondin
the wetting f wetting front
parameters. integration:
After substit porous pipe
tting pattern
ows the obse pectively.
otograph in m at
t = 24
lane. Howev be similar t
r calculating of a truncate
Figure 3.
Léquilibr
he radial coo maximum ra
ng to R
m
an front and the
t H
, R
m
and The trunc
uting Eq. 2 from
V
t
and
n
erved wetting
Figure 4 sho
hours. The ver, in the ve
to a truncate the wetted s
ed ellipsoid is
. Water balan
re de leau da
R r
ordinate, z
is adial spread
nd B
is the d e vertical coo
B are defin
ated ellipso
V
t
into Eq. 3, d is given by
g front at t
= ows the wet
configuratio rtical plane,
ed ellipsoid. soil volume,
V s given acco
nce in meas ans lessai d
2 2
2
B H
z R
r
m
s the vertical d of the we
istance betw ordinate of
R ned in Figure
oid volume,
r
H B
2
, V
wet
is obta the following
=24 hours for tted soil aro
n of the wet the configur
Consequent V
wet
. ording to Aca
urement acc exactitude d
1
2
H
coordinate etting front
ween the ma R
m
. The repr
e 4.
H ,
R
m
an V
t
, is deri
dz z
ained by subt g equation:
r P
n
= - 0.02, ound the por
tted soil is c ation of the w
tly, a simple ar et al., 2009
curacy test de mesure
z = 0 : the
, H
is the aximum vertic
resentative le nd
B are calle
ived from t
tracting the v , - 0.07 and
rous pipe fo circular in the
wetted soil is e approach is
9:
2
soil surface e value of
z cal spread o
engths of the ed geometric
the following
3 volume of the
- or
e s
s
, z
of e
c g
e
Figure 4.
mo
Figure 5 sho
The former w was obtaine
photographs truncated el
expanded w relation of
P Figure 6 sho
geometric pa 0.10 m. Sol
Wetting fron uillage dans
V V
t wet
ows the com was obtained
ed from the s and with a
llipsoid as lo with the decr
P
n
to the temp ows the exp
arameters a id lines in Fig
w nt in vertical p
le plan verti
B R
l R
m p
2
3
mparison bet d
by substitu e configurat
ruler. It is s
ong as Kaw rease in |
P
n
| poral variatio
pansion of th ssociated wi
gure 6 expre
where q
= 0.0 plane for diff
cal pour diffé
H B
B
m 2
2
tween the ca uting
B ,
H an
tion of the seen that the
wanishi sand at the same
ons in H
, R
m
a he wetting fro
ith the chang ess Eqs. 5,
q
pt H
j m
it R
n
mt B
05,
j = 0.14,
ferent negativ érentes press
H B
2
2
alculated V
we
nd R
m
measu wetting fro
e wetted soil is used. S
e t
see Figu and
B .
ont, i.e. the ge in
P
n
for 6 and 7 f
n = 0.14 an
ve pressures sions négativ
l R
H
p 2
et
and the ob ured in Eq. 4
ont, measure
can be con ince the we
ure 4, we e temporal inc
P
n
= - 0.02,
for 24 ≤
t ≤ 72
nd s Front de
ves 4
bserved one 4. The latte
ed from the nsidered as a
etting front is examined the
crease in the - 0.07 and
2 hours. 5
6
7 e.
r e
a s
e e
- 5
Figure 5
The relation
regardless o
Figure 7 sh
observed V
w
is seen that
Figure 6. T 5. Accuracy o
n between e of
P
n
as long
hows the co
wet
. V
wet
was Eq. 4 is ap
Temporal var temporel
p
of wetted soi
i
m each of the
as Kawanish omparison of
calculated b pplicable to p
riations in ge les des para
07 .
n
P p
il volume Pr
10 .
n
P i
06 .
n
P m
geometric hi sand is us
f the tempo y substituting
redict the va
ometric para amètres géom
08 .
récision du vo
04 .
04 .
parameters sed.
oral variation g Eqs. 5 th
alue of V
wet
.
ameters, H
, R
métriques, H
olume de so
and t
has ns in the ca
hrough 10 in
R
m
and B
Le H
, R
m
et B
8
l mouillé 9
10 a similarity
alculated and nto Eq. 4. I
es variations y,
d It
Figure 7. C
volume Co
4.3 Soil wa Figure 8 sho