Modeling 3D Spatially Distributed
Water Fluxes in an Andisol under Banana Plants
J. Sansoulet,
Y.-M. Cabidoche, P. Cattan, S. Ruy, and J. Šim ů nek
S o il S o il
Interface Interface
Humid tropical climate : 2.5 à 4.5 m water.year -1 with intensities > 70 mm.h -1
Main stemflow around the pseudo-stem
Stemflow x 10 to 35 the incident rainfall + throughfall
P la n t P la n t A tm o sp h ere A tm o sp h ere
Interface Interface
KNO 3 supply:
massive and localized around the stem
(400 kg N/ha/y 800 kg K/ha/y)
slope> 10%
NO 3 - K +
Leaching in depth
Godefroy and Dormoy., 1988 Bassette and Bussière, 2004
Introduction
Objectives
Evaluate distributed subsurface water fluxes under banana plants and to use the collected data to evaluate and numerically simulate these distributed water fluxes using the HYDRUS software package.
Hence, the study had several phases:
(i) laboratory experiments to obtain soil hydraulic parameters characterizing the unsaturated hydraulic conductivity function, K(h), and the soil water retention curve, θ (h);
(ii) field experiments to measure surface water fluxes (stemflow and throughfall) and subsurface pressure heads and drainage fluxes;
(iii) numerical modeling using the HYDRUS model to predict distributed water
fluxes and compare them to the in situ drainage measurements.
Schematic representation of the flow domain
Lysimètres Tuyaux Collerette
Partiteur de stemflow Tôles
Bac de ruissellement
-0.5 0 0.5 1
X (m)
2.5 3 3.5 4 4.5 5 5.5 6 6.5
Y (m)
4
3 2 1
vers les bidons munis de capteurs de pression
Faux-tronc du bananier Tensiomètres de surface
Tensiomètres à 25 cm de profondeur Tensiomètres à 55 cm de profondeur
Material and methods
Schematic representation of the flow domain
Material and methods
z S K h
z y
K h y
x K h
x
t −
−
∂ + ∂
∂
∂
∂
∂
∂ + ∂
∂
∂
∂
= ∂
∂
∂ θ 1
Water retention curve (Wind measurements)
Hydraulic conductivity curve (Double ring Infiltrometers)
( ) = 1 − ( 1 − e m 1 ) m 2 l
e
s S S
K h
K
( )
s nr mh h
) 1
( α
θ θ θ
+
= −
HYDRUS 3D model simulate Darcian water flow in a three-dimensional flow domain in the unsatured-saturated flow system
Richards Equation of water transfer
Run-off, soil evaporation, plant
nutrition
Mualem -Van Genuchten
(1980)
Modeling 3D Spatially Distributed Water Fluxes
Material and methods
-1.752 -1.666 -1.579 -1.493 -1.406 -1.319 -1.233 -1.146 -1.060 -0.973 -0.887 -0.800
Pressure Head - h[m], Min=-1.752, Max=-0.800
-1.752 -1.666 -1.579 -1.493 -1.406 -1.319 -1.233 -1.146 -1.060 -0.973 -0.887 -0.800
Pressure Head - h[m], Min=-1.752, Max=-0.800
(c)
(d)
(b)
Banana stem
Seepage Free drainage Lysimeter 4
(a)
Stemflow Throughfall
A horizon B horizon
Lysimeter 1 Lysimeter 2
Lysimeter 3
Results : Soil properties
Results
Effective soil hydraulic parameters
0.5 280
3.61 0.06
0.63 0
Wick
0.5 1.06
1.05 23.3
0.75 0.11
B horizon
0.5 3
1.07 19.0
0.75 0.13
A horizon
m d −1 m −1
———— m 3 m −3 ——
——
l K s
α n θ s
θ r
Material
0.5 280
3.61 0.06
0.63 0
Wick
0.5 1.06
1.05 23.3
0.75 0.11
B horizon
0.5 3
1.07 19.0
0.75 0.13
A horizon
m d −1 m −1
———— m 3 m −3 ——
——
l K s
α n θ s
θ r
Material
Physical properties of the Andisol
0.665 3.73
0.49 63.1
B
0.673 6.69
0.71 58.6
A
m 3 m −3
% g cm −3
%
Total porosity Organic C
Bulk density Clay†
Horizon
0.665 3.73
0.49 63.1
B
0.673 6.69
0.71 58.6
A
m 3 m −3
% g cm −3
%
Total porosity Organic C
Bulk density Clay†
Horizon
Mean pressure heads measured with tensiometers
Under the banana stem
-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0
0 20 40 60 80 100 120 140 160
Time, d
Pressure Head, m
0 50 100 150
Rainfall, mm Between the rows
-3.5 -3 -2.5 -2 -1.5 -1 -0.5 0
0 20 40 60 80 100 120 140 160
Time, d
Pressure Head, m
0 50 100 150
Rainfall, mm
Rainfall 6 cm - Observed
25 cm - Observed 55 cm - Observed
Simulating
period
Modeling 3D Spatially Distributed Water Fluxes
t = 0 day
t = 0 day t = 1 day t = 2
days
t = 6
days t = 14 days t = 16 dayst = 16 days
