DEVELOPMENTOF IRRIGATION WATER DISTRIBUTION DECISION
SUPPORT TOOL FOR MWEA IRRIGATION SCHEME
Mohammed Abdullahi (PhD)-Technical University of Kenya
Benedict P.O Owilla-MIAD Dennis Okinyi -MIAD
Content
• Background• Objectives• Research Methodology• Reconnaissance Survey Results• Irrigated Area Mapping Using LANDSAT• Water Demand Calculation Module• Remaining work
Background
• In an effort to increase food production and create employment, the government has embarked on a programme to – develop new irrigation scheme,– expand and/or rehabilitate the old ones.
Scarcity of Water Resources
• There is increasing competition for the scarce water resources by various sectors in the country notably between agriculture, industrial and municipal.
• With the expansion of irrigation schemes competition within the agriculture sector has intensified hence the need to improve water productivity
• Large scale irrigation schemes typically suffer from unequal distribution of irrigation water
– unreliable deliveries of water due to either lack of a distribution plan or
– difficulties in implementing one where available.
• In 2007, the Water Resources Management Authority introduced charges for water use in the agricultural sector,
• this meant that each scheme will pay for the amount abstracted/pumped irrespective of the irrigation efficiencies. – Thus there is great incentive to improve the water
use efficiencies since this will translate to lower charges and hence savings for the farmers.
• Irrigation infrastructure in Mwea Irrigation Scheme has been rehabilitated by the National Irrigation Board in the last few years– improved conveyance efficiencies
• the next critical step in improving the overall scheme efficiency is to improve the decision making process in water distribution management – this tool goes a long in aiding the achievement of this
goal
• The Irrigation Water Distribution Support tool will enable staff and farmers to understand– the scheme water requirement at various stages in
the growing season,– the available water resources – and the best way to distribute it.
OBJECTIVES
• Determine the irrigated area for the Mwea Irrigation Scheme using Remote Sensing
• Determine the seasonal irrigation water requirement for the
Mwea Scheme
• Develop a simple yet versatile irrigation water distribution support tool for each scheme that links demand to supply
• Select and calibrate water measurement facilities to be used together with the tool developed above.
MethodologyData Collection and reconnaissance survey
Remote Sensing data analysis (Irrigated area)
Irrigation Typology Module
Water Demand Calculation Module
Water Resources Assessment Module
Irrigation Water Distribution Module
Reporting Module
Flowchart of Development of Irrigation Water Distribution Support Tool
Legend
Main Module
Progress so far
Scheme Reconnaissance Survey
• Meteorological and River Discharge Data collected
• Scheme Main, Branch canals, intake points mapped
• Lined and unlined canal distance quantified• Number and condition of water measuring
facilities assessed
XX
X
XX
X
XXXX
X
X
XX
XX
X
X
X
X
X XXX
XX
XX
XX
X
XX
X
X
XXXX
X
X
X
XX
X
X
X
X
X
XXXX
X
XX
X
X
XX
X XXX
XXX
X
X
XXX
X
X
X X
XX
XX
XX
XXX
XX
XX
X
X
TBC2
TBC3
T8T7
T5
H2
H6
w4
W7W7
T25
T23T22
T11T19
T18T16
T20
CP4
H20
M17
M11
TBC1
TBC4
TBC2
W6-W5
M12 B
M12 C
TBC1A
T2- T3
Ndekia
w7-K10
M9-M10
TBC1AB
Kianugu
T20-Dam
T9-Keriko
T16 LowerT17 lower
TBC4-TBD1
Marura A
Ndekia TwoNdekia Two
K4 OfftakeK5 Offtake
K6 Offtake
KI Offtake
H5-Gitumbi
End of LC1Head Works
K9-K6-K7-K8
M14-M15-M16
K2,K3Offtake
TBC3-TBC4-H2
H18-Ciumbiri
Women Project
T4 offtke 1
Kandongu/Ngothi
MIAD-Pilot farm
T16 Lower part
T13 offtake # 1
T23-T25 Extension
Possible Rec Weir
T12-Kari-Jua Kali
Nyamindi headwork
Rubble weir intake
Ndekia One-Offtake 2Ndekia One-Offtake 1
H4-Gitumbi Extension
M9-M10 suppl offtake
Ndekia four-Offtake 1
T16, T14 Jua Kali ext
Ndekia four-offtake -3
Ndekia Three-Offtake 2
H3-Mbui Njeru jua kali
M13/M12A/Muga Kandongu
H19-Ciumbiri 2-Kiandegwa
T16, T13 offtake Junction
T4 Offtake 2 (+ Kari Pipe)
Ndekia four-Offtake with spring
T5
T22T20
CP5
CP6
CP4
H6-8
Marura A
4DA10 G.P
CP 1 & CP 2
K2,K3Offtake
W6-W5 Cippoleti
Possible Rec Weir
H20-Parshall Flume
Ndekia One-Offtake 1
NBC2 Rectangular Weir
MIS Canal and Offtake Network Map
±
Legend
X Off_takes_Locations_MIS
Canal_Network
<all other values>
Id
Lined Headrace
Lined Link Canal
Unlined Main canal
Lined Main Canal
Lined Brach Canal
Unlined Branch canal
River
<all other values>
Measuring Structure
Existing
Potential Site
0 0.8 1.6 2.4 3.20.4Kilometers
Note: This map is based on Field Survey done on Nov. 18-22, 2013 by Mohammed Abdullahi
Number of Water Measuring Facilities
Type Number
1 Rectangular Weir/Cippoletti/Drop Structure
13
2 Parshal Flume 2
3 Broad Crested Weir 5
4 Canal locations with good gradient 4
Total 24
ConditionCondition Number
1 In working Condition 5
2 Requires gauge and calibration (head to discharge)
12
3 Require repair, gauge and calibration 7
Total 24
Main, Link and Branch Canals
CanalTotal
Length Lined Unlined
Name Abbreviation km km % km %Nyamindi Headrace NHR 0.85 0.85 100.00 0.00 0.00Link Canal 1 LC1 7.18Nyamindi Main Canal NMC 4.61 4.61 100.00 0.00 0.00Nyamindi Branch Canal 1 NBC1 7.40 5.11 69.05 2.29 30.95Nyamindi Branch Canal 2 NBC2 4.41 1.30 29.48 3.11 70.52Nyamindi Branch Canal 3 NBC3 3.40 0.00 0.00 3.40 100.00Thiba Main Canal TMC 11.41 8.21 71.95 3.20 28.05Thiba Branch Canal 1 A TBC1 A 2.08 Thiba Branch Canal 2 TBC2 7.24 0.00 0.00 7.24 100.00Thiba Branch Canal 3 TBC3 4.86 0.00 0.00 4.86 100.00
Thiba Branch Canal 4 TBC4 12.91 2.40 18.59 10.51 81.41
Remote Sensing data analysis (Irrigated area)
The Irrigation command area is critical to calculating Scheme diversion requirement– The Mwea Irrigation Scheme has undergone
expansion since late 1990’s – Irrigated area keeps fluctuating seasonaly due to
availability of irrigation water among other factors
Determination of Irrigated Area
-The LANDSAT offers an inexpensive and relatively accurate method for determining the irrigated area.• It has a spatial resolution of 30m and
temporal resolution of about a month
– Visual analysis of LANDSAT scenes between 2000 and 2013 showed that 2013 had the biggest irrigated area.
METHODOLOGY•Two LANDSAT 8 Scenes for 2013 Short Rain Season were available just before the rainy season started, Late September and Late October. •Late October (30th October) was selected since
Most of the scheme were cropped and easily identifiable
•There are up to 11 bands in each scene, but of importance to this exercise is Band 4 (Red), and Band 5 (Near Infra red) .
•In order to bring out a good contrast in the vegetative index the division of band 5 over four is used(Konduris et al, 1998).
•Next since the Landsat scene is wide the area of interest (Mwea) and its environ is clipped
•Using an colour enhanced scene for October 30th, manual digitization of the irrigated units boundary was done since the automatic digitization didn’t produce clear boundaries.
•Manually produced units were named
•Area of each unit calculated using GIS software
CALCULATION OF IRRIGATED AREAS
Gross AreasUsing GIS software the areas the digitized polygons were calculated to give the gross areas (includes on farm infrastructure such as roads and canalsNet Irrigated areasThe roads & Canals were estimated at 6% as explained in the next slides. This was deducted from the gross areas to give net area
Calculation of Net Irrigated area
FIELD MEASUREMENTS
NB: 1. Length is an average of at least four measurements at different places. 2. Middle (bare section) of road, AV = 6.2 m
Unit Description Length (m)
M9 Entire road from drain to drain 9.73
M10 Entire road from drain to drain 9.7
M9 Feeder bunds 0.85
M10 Feeder bunds 1.1
M9 Drain bunds 0.83
M10 Drain bunds 0.72
Scheme Irrigated Area (2013 Short Rain Season)
Gross Area (ha) Net Area (ha) Net Area (acres)LANDSAT DELINEATED AREA
11,149.00 10,703.04 26,757.60 OFFICIAL DOCUMENTED AREA
_
7,673.20 19,183.00 DIFFERENCE _
3,029.84 7,574.60
Comparison of Irrigated Area (At Section Level)
Section (Check Point) Landsat Delineated Area (ha)
Official Area (ha) Difference (ha)
Tebere (CP.1) 1818.24 1316.4 501.84Kainugu (CP.1) 136.32 160 -23.68Ndekia (CP.2) 1296.96 434 862.96Mwea (CP 3, CP.4) 1534.08 1270.8 263.28Ciurukia, Kandongu (CP.3,CP4) 1101.12 858.8 242.32Thiba (CP. 3, CP. 4, CP.5) 1706.88 1315.4 391.48Wamumu (CP. 5, CP.6) 1230 1007 222.56Karaba (CP.7, CP. 8, CP.9) 1477.44 1118.4 359.04T20, Kiamanyeki (Rubble Weir) 387.84 367 20.64
This differences may be as a result of:-Wrong unit boundary,-Underestimation of official area: New
extensions not accounted for.To be confirmed during “ground truthing”
Causes of Area Differences
Water Demand Calculation Module
Data Needs for this Module
• Irrigated area under at each water measuring structure (Check points)
• Water requirement components Puddling/rotavation water requirement ET Field Losses Canal/Section losses
• Other parameters (no of tractors & rotavation rate…)
Irrigated area
• The water distribution calculation sheet picks up the irrigated area under each point from the cropping plan using lookup function =IF('Cropping Plan'!
$D$4<Water_Requirement_Check_Points!$A8, IF('CroppingPlan'!$F$4>Water_Requirement_Check_Points!$A8, 'Cropping Plan'!$C$4,0),0)
Water requirement components
• ET-Calculated using PENMAN Montheith and historical meteorology data
• Rotavation requirement 250mm (Mohammed & Tanaka 1995)
• Field Losses 2mm (Van Gessel 1980, Mohammed & Tanaka 1997)
• Section/canal losses 0.4mm (Mohammed & Tanaka 1995)
Remaining Work
• Ground truthing of Landsat irrigated area maps
• Development of Remaining modules and documentation
• Testing, Training and Deployment
Thank you
Top Related