Transcript Effect of the ACN on agricultural field water balance in Mali

Effect of the ACN on agricultural field
water balance in Mali
K. Brannan, R. Kablan, R.S. Yost, M.D. Doumbia,
A. Yoroté, Y. Toloba, S. Sissoko, and
M. Vaksman
Overview
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Background
Hypothesis
Calculation Methods
Results
Future Plans (This was 1st year)
Background
(Problems)
Deforestation
Runoff
Management
$Revenue Sources$
Farming on Steep Slopes
Reduced Groundwater Recharge
Reduced Soil Fertility
Background
(Runoff Management, Mali)
Practice: Amenagement en
courbes de niveau (ACN)
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Field Water management practice
Series of ridges contour
Permanent Ridge (Ado)
Temporary Ridges (cropped areas)
Water management of whole area
Socio-economic factors
Impact of Practice
No ACN
with ACN
Hypothesis
• ACN improves field water balance
• More water available for crop use
• More potential local groundwater recharge
(drainage)
• Reduces surface runoff
Approach
• Two Locations
(Konkgougou and Fransirokoro)
• Treatments: Field with ACN and without
• Measure Soil Water at multiple locations
and depths
• Rainfall and potential evaporation data
• Calculate field water balance
Soil Water Probe
Diviner 2000®, Sentek
Study Site: Konkgougou
Permanent Ridges
Tubes
Field Water Balance
Field Water Balance
S = R – ET – Esoil – GWR – RO
where,
S - change in soil water storage
R - rainfall
ET - crop evapotranspiration
Esoil - evaporation from the soil
GWR - local groundwater recharge
RO - surface runoff
Measured
Estimated
Calculated
Field Water Balance: Runoff
RO = R – ET – Esoil – GWR – S
Rainfall and Evaporation
• Rainfall data collected at site
• Potential Evaporation data from Bamako
Station
• Soil evaporation constant proportion of
potential evaporation
ET Calculation
ETc  Kc  ETo
ETc- Crop evapotranspiration
Kc - crop coefficient
ETo- observed (reference crop) ET
(Kc temporally distributed based on LAI)
ET Calculation
1.4
1.2
Crop Coefficient (Kc)
1.0
0.8
0.6
0.4
0.2
0.0
Corn
Sorghum
Millet
Soil Moisture Storage
Integrate Readings
0-70 cm
70-90 cm
Root Zone
Transition Zone
Drainage
Soil Moisture Storage
200
40
180
30
20
140
120
10
100
0
80
60
-10
40
-20
20
0
18-Jun
28-Jun
8-Jul
18-Jul
28-Jul
7-Aug
17-Aug
27-Aug
6-Sep
16-Sep
-30
26-Sep
S (mm)
Cummulative Soil Moisture in Root Zone (mm)
160
Local Groundwater Recharge
(Drainage)
• Pedo-transfer function
• Van Genutchen’s Equation
– Hydraulic potential
– Hydraulic conductivity
• Darcy’s Equation
Local Groundwater Recharge
0-70 cm
70-90 cm
Root Zone
Transition Zone
Drainage
Aggregate
Local Groundwater Recharge
Cumulative Local
Groundwater Recharge
Unsaturated Hyd Cond.
1.4
200
1.2
150
1
100
0.8
0.6
50
0.4
0
0.2
0
18-Jun
28-Jun
8-Jul
18-Jul
28-Jul
7-Aug
17-Aug
27-Aug
6-Sep
16-Sep
26-Sep
-50
8-Jul
18-Jul
28-Jul
7-Aug
17-Aug
27-Aug
6-Sep
16-Sep
26-Sep
Runoff
RO = R – ET – Esoil – GWR – S
Results
• Comparisons tubes with and without ACN
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–
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Tubes 03 to 10
Tubes 05 to 10
Tubes 15 to 21
Tubes 17 to 22
Results: Tubes 03 to 10
70%
60%
% of Total Rainfall
50%
40%
30%
20%
10%
Control (Tube 10)
0%
ACN (Tube 03)
Drainage
Runoff
ACN (Tube 03)
Control (Tube 10)
Results: Tubes 05 to 10
70%
60%
% of Total Rainfall
50%
40%
30%
20%
10%
Control (Tube 10)
0%
ACN (Tube 05)
Drainage
Runoff
ACN (Tube 05)
Control (Tube 10)
Results: Tubes 15 to 21
70%
60%
% of Total Rainfall
50%
40%
30%
20%
10%
Control (Tube 21)
0%
ACN (Tube 15)
Drainage
Runoff
ACN (Tube 15)
Control (Tube 21)
Results: Tubes 17 to 22
70%
60%
% of Total Rainfall
50%
40%
30%
20%
10%
Control (Tube 22)
0%
ACN (Tube 17)
Drainage
Runoff
ACN (Tube 17)
Control (Tube 22)
Location Effect
Tube 05
Tube 17
Ados
Future Plans
• Continue data collection
(several more years)
• Relate balance to crop yields
• Improve instrument calibration
• Improve calculation methods
• Quantify impact on village wells
• Improve/Modify ACN design
Merci