UNIVERSITY OF NAIROBI
DEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERING
FEB 540: DESIGN PROJECT
2013/2014 ACADEMIC YEAR
DESIGN OF AN INTEGRATED CENTRE PIVOT IRRIGATION SYSTEM
A case study of 100ha in Hola area in Tana River county
MUCHIRI JOSPHINE MUTHONI
F21/2528/2009
Supervisor : Dr. J.P. Obiero
BACKGROUND
Did you know that irrigation would help utilize the potentials of arid and semi arid areas in
Kenya
 development of irrigated agriculture became inevitable due to rapid increase of
the country’s population since the 1950s
 80% of Kenya’s land area is arid or semi-arid
 Government has further stressed the importance of promoting irrigation
development in the Vision 2030 for the period 2008 – 2030 so as to stabilize and
improve food supply through optimum utilization of available land and water
resources
 conception of Bura Irrigation and Hola Settlement Project in production of cotton
and maize from 1982 to 1990 with an area of 2,500 hectares being irrigated.
 Tana River is considered as the major surface water source of irrigation which is
considered as the important means to increase agricultural production and
population intensity in the area.
background
 Need to intensify land use in the high and medium potential areas and bring to use arid
and semi-arid lands. Irrigation offers one of the best strategies in realizing these
objectives
 Kenya has an irrigation potential of 1.3 million hectares.-Out of this, 540,000 hectares
can be developed with the available water resource, while the remaining 800,000
hectares will require water harvesting and storage equivalent to about 25 billion m³.
 Currently, 114,600 hectares and 30,000 hectares are under irrigation and drainage. This
translates into 21% and 5% of the existing irrigation and drainage potential respectively.
However, the area under irrigation is a mere 9% of the total irrigation potential of 1.3
million hectares.
 irrigation expansion may be predicted to go up as a measure to adapt to climate change,
achieve food security and save for investments
 irrigation expansion may be predicted to go up as a measure to adapt to climate change,
achieve food security and save for investments
 zones known for coffee production, bananas, maize, and many types of vegetables,
legumes and fruits. Tana and Athi River, Ewaso Ngiro and Kerio Valley basins are in
these locations
PROBLEM STATEMENT AND PROBEM ANALYSIS
 weather patterns -erratic with no rain fed production
being realized with rains falling below averageincreased household poverty and lack of livelihood
and income.
 Flooding, soil erosion, high runoff, the need for an
improved irrigation technologies that will enhance
efficient use and application of water due to the high
evaporation rate and runoff. Reduce social comfits
between the nomadic and agricultural farmers
 huge potential to exploit in terms of coverage and
expansion for large scale. The land is generally very
flat, thus suited for canals, sprinkler, drip, Centre
pivot ,this project is expected to actualize this
potential and boost food productivity in the area
 Need to exploit the potential of the arid and semi
arid areas of Kenya inline with the vision 2030 of
Kenya.
SITE ANALYSIS
Hola Area
Tana river
county
Site analysis
 Hola is a small town in Kenya on the Tana River at 40.030E and 1.50 0S
 The county has a population of 240,075,Hola with a population of 6932 ,
Nomadic and agricultural farmers
 The terrain is mainly undulating with few hills and the land slopes gently
south-eastwards from 200m in the highest hills to the coastal line
 Unreliable rainfall<750mm, Precipitation is low, bimodal and quite erratic,
fluctuating between 300mm to 500mm annually.
 Temperatures are warm and exceed 28.80C throughout the year, with an
average of 27.9°C
 The area is mainly covered with open bush and rather dense shrub
vegetation, Mathenge”. Currently, this is the dominant vegetation in the
OBJECTIVES
The overall objective is to design an automated Centre Pivot irrigation system
1.SPECIFIC OBJECTIVES
 The specific objectives of the project are:
1. To identify the crop water requirements and irrigation parameters
2. Use the parameters in (1) above in design the system components of
the Centre pivot irrigation system which are the pumping system, pipe
work, water sump, pump houses, Hydrants, and pivot.
3. Analyze the cost benefit effectiveness of the various energy sources
SCOPE OF WORK
 The scope of this project was on the design of Centre pivot irrigation system located
in Hola Tana River County.
 The design involved the determination of the field layout,
 estimation of the crop water requirements to schedule the system,
 conveyance of the water to the field,
 determination of the power requirements cost estimates of the system.
 Carry out design process showing the components of the Centre pivot irrigation
system
 Do accost benefit analysis of the system comparing solar system to a diesel engine
system.
 Limitation of my scope is large scale farmers of about 50ha to 100 ha of land or
groups of farmers with large schemes.
LITERATURE REVIEW
 Irrigation is an artificial application of water to the soil
 Appropriate Technology: Technology that is socially acceptable (SA), economically viable (EV)
and technically feasible (TF)
 Factors considered: water , soil, topography, climate, energy cost, crop, labour, capital cost,
personal considerations
 Irrigation systems: drip, furrow, travelling gun system
 History of centre pivot system, justification, advantages
 Components of the irrigation system: The water source, The intake facility, The conveyance
system, The piping system
Literature
 Purpose for irrigation: Increase area under the crop to enable crop to be grow
where natural rainfall is too low to grow normal crops, Provide additional water to
optimize crop production, Weed control and Enable crops out of season production
 Factors considered in the selection of irrigation methods: Natural conditions, type of
crop, type of technology, previous experience with irrigation, required labour inputs, costs
and benefits
 Potential of the area
Basin
Tana
Athi
Lake Victoria
Kerio Valley
Ewaso Ngiro
Total
Irrigation Potential(Ha)
205,000
40,000
200,000
64,000
30,000
539,000
Literature review cont’d
Advantages of center pivot
 Well suited for irrigating larger and small areas,
 Precise application of water,
 Low maintenance and labor costs,
 Financially viable even on such small areas.
 Easily automated,
 Accurate water distribution at low pressure,
 No blockages as compared to drip irrigation.
 Pests are washed out hence low use of chemicals.
 20 years lifespan with low maintenance, basically requiring routine checks
 Centre pivot increases water efficiency by some 85-95 percent, according to The
Groundwater Foundation.
METHODOLOGY
Collection of agro-climatic data, included.
Preliminary site visit and survey work was
done
Identification of irrigation land
 Inspection of Hola site
Collection of meteorological data, i.e. temperature and
rainfall
 Study of the vegetation
 Study of suitable crops in the area
 Assessment of the infrastructure
 Soil and water sampling and testing was
done
Identification of water resource
Collection of agricultural data, i.e. crop varieties, seeds,
diseases and pests, post-harvest practices, cropping
patterns and cultivation practices
Methodology cont'd
 Primary data was collected by the use of formal and informal survey methods.
 Formal surveys with the help of direct interviewing of relevant local members.
 Discussion was with key informants
 The current situation on the ground was assessed through Observation
 The design was carried out showing: Centre pivot system , the mainline size and outlet
spacing, length, including the number of towers, drive mechanisms, application rate of the
pivot.
 The market survey was done showing the cost effectiveness, durability and reliable
materials/ equipment’s appropriate for the energy source mainly solar, diesel and
electricity.
 Analyze demerits of each of the options and make recommendations on the most suitable
option: cost benefit analysis of the energy system was compared.
METHODOLOGY
Data collection
Primary &secondary
Flow requirements
of the system
Selecting pump,
requirements and
performance chart
Determine system
parameters
Speed and working
hours of pivot
Power rating
Analysis of Soil
infiltration rates
Pipe sizing
Sizing solar panel
PRODUCT DESIGN
Design process cont'd
 Crops selected were maize, sorghum, cotton and groundnuts
Product Design
 CROP WATER REQUIREMENT ETC: ETcrop = kc x Eto x Kr
ETC
= 5.53 x 1.2 x 1.0 = 6.636mm/day
 DEPTH OF APPLICATION : dnet = (FC-PWP) x RZD x P
dnet = (140mm/m) x 0.53x 0.5=37.1mm
 VOLUME OF WATER TO BE APPLIED (m3) = 10 x A x d
Volume of water to be applied (m3) = 10 x 100ha x 37.1mm=37100m3
 IRRIGATION FREQUENCY (IF) = 37.1mm/6.00mm/day=6.183days,
Irrigation frequency(IF)=6days
 DEPTH OF APPLICATION: dgross =dnet /E
dgross = 37.1/0.70 = 53mm
design
 SYSTEM CAPACITY: Q = 10 x A x dgross/ (I x Ns x T)
CP2:
CP7 :
Q = 10 x 60.77 x 53mm/ (7 x 2 x 10) =230.05m3/hr
Q = 10 x 38.79 x 53mm/(7 x 2 x 10)=146.85m3/hr
 NET IRRIGATION REQUIREMENT: NIR = ETC – Pe- Ge- Wb (mm/day)
NIR = 6.0 -0=6.0 m/day
 IRRIGATION EFFICIENCIES: Ep = Ec x Ea x Ed
0.95 x 0.95x 0.90 =0.81225%
 GROSS IRRIGATION REQUIREMENT: GIR = NIR/E
GIR = 6.0/0.81225=7.387mm/day
 ACTUAL SCHEME WATER REQUIREMENTS: Qwr= 10 x A x GIR x () x () (m3/day)
=10 x 7.387x 100x 24/20x7/6
= 10341.644m3/day
design
 Field Irrigation rate: Etc. = 6.0 mm, Number of days = 7 days, Number of shifts per week = 6
irrigation application rate will be; = 6.0 x 7/6 = 7mm
 Factoring in the irrigation efficiency of 0.81225%, then the gross application rate will be;
=7.0/0.81225 = 8.6180mm
 CP2, Considering the efficiency of the system of 81.225%
0.37709m3/hr X 0.7695=0.3063 m3/hr since 1 hr=0.3063 m3/hr. To get 6.0m3/day then
==19.59hrs=20hrs
 CP7, Considering the efficiency of the system of 81.225%
0.377645m3/hr X 0.7695=0.3067m3/hr since 1 hr=0.3067 m3/hr
To get 6.0 m3/day then ==19.56=20hrs
 The system will operate for 20 hours for 6 days. This is to allow for one day servicing of the
system.
COMPONENTS DESIGN
 POWER REQUIREMENTS IN KW =Q x H/360 x e
CP7: 146.85*28/(360*.75)=15.23kW
CP2: 230.05*35/(360*0.75)=29.82kW
 Choosing from lowara pumps we get
A pump of FHE-FHS-FHF SERIES OF 80-160/150 with 15kW and 20 HP
A pump of FHE-FHS-FHF SERIES OF 100-200/370 with 37kW and 50 HP
SELECTION OF NOZZLES
Precipitation =Dischrge/area of coverage
Area irrigated 254.469-78.54=175.929m2
Precipitation=8.6180mm in 20hrs
8.6180 =discharge/175.929=676.856/20hrs=1.516m3 /hr
DESIGN OF THE MAINLINE
 The size of mainline is determined by: Required flow rate through the pipe, Overall length of
line, Static height, Flow velocity, Factor of safety
 the following factors should be kept in mind: Maximum permissible velocity should be 1.8 m per
second not exceeding 2.5m per second based on hydrocalc software.
 Maximum friction losses should be limited to 50 m per 1000 meters of pipe
 Elevation and pipe pressure rating: minimize high pressure rated pipes on elevated grounds
and vice versa.
 Mainlines should follow the shortest possible route
 Provide air release, vacuum valves, non-return valves, pressure reducing and pressure
sustaining valves at the correct positions.
 The size determines the initial cost
 The length of the mainline = 900m, The total flow = 228 m3, The pipe size = 200mm PVC Class
PN6, The pipe loss = 6.36m (0.74%)
 The length of the mainline = 1000m, The total flow = 146 m3/hr, The pipe size = 200mm PVC
Class PN6, The pipe loss = 5.16m
Summary of the Centre Pivot Details
 The system was designed to deliver a gross application of 8mm/day
 the other crop require less water applications hence the speed is adjusted to provide that
requirements.
 The irrigation schedule is to irrigate three days a week, if you irrigate on Monday with
8mm/day then on Tuesday the Etc of the crop is 5mm/day hence a reminder of 3mm/day,
then irrigate on Wednesday 8mm/day having a total of 11mm/day, the Etc on Thursday and
Friday will be 10mm, hence the need to irrigate again on Saturday with 8mm/day and no
irrigation on Sunday
Cps
CP2
CP7
Operatin
Length Area
g angle
degrees m
ha.
360
360
439.2
350.8
Irr.
Time
hrs
Pipe size CWR
Pipe length,
net
CWR Gross
m
mm
(mm/day (mm/day)
)
61
38
900
1096
200
200
6
6
8.3
8.3
System
Flow
m3/hr
20
20
228
146
Pump
Power
Head
m
Rating
kw
35
25
30
15
CONCLUSION
 The irrigation design is successful if managed to meet the crop water requirements
since the system is installed on soils having infiltration rates matching or exceeding the
system application rate
 The design of the centre pivot irrigation system meets the general design criteria for
irrigation systems.
 The site so selected for its location is ideal as it offers suitable area for expanding large
scale irrigation system.
 The operation of the centre pivot has less expenditure in terms of cost since it only
require greasing and repair unlike other systems the operators has to be ever present.
 This system consumes a lot of power and the best source selected properly to cover
the economies of scale. Solar energy has a high initial capital cost but long life time
hence the maintenance cost are therefore less. The diesel engine has lost capital cost
and maybe preferred but the maintenance cost is very high as shown in the
calculations.
 The operation is fairly trouble free on level lands and uniform sloping lands with slopes
up to 10%.Undulating topography usually produce more difficulties with more potential
runoff.
RECOMMENDATON
 The construction of the proposed reservoir for constant water supply to the field
 The construction of another gravity canal from Tana river this will give more room for
additional projects
 More research on the incorporation of solar energy on large scale irrigation components
and equipment’s.
 On soft or erosive soils, tracks should be lined with sand where excessively deep tracks are
made in the field by the drive wheels
 In undulating topography to reduce surface runoff, small holes or depressions should be
dug to hold water on the application points.
 This center pivot moves in a circular motion thus in case of irregular shapes of land the
whole area is not irrigated, some patches are left at the ends. Recommend that the
structure should be designed with corner catchers that folds out to irrigate these area, thus
this areas should be included in the irrigated area.
REFERENCES
 Simiyu JN, Mwongera CN, Gohole LS and RM Muasya. (2003)Farmers’ knowledge and practices in spider plant (Cleome
gynandra L.) seed production: Case study of Kakamega and Vihiga districts. Proceedings of the third workshop on
sustainable horticultural production in the tropics, Maseno, Kenya 2003.
 Bhattarai, M.; Sakthivadivel, R.; Hussain, I. (2002). Irrigation impacts on income inequality and poverty alleviation: Policy
issues and options for improved management of irrigation systems. Colombo, Sri Lanka: IWMI. vi, 29p. (IWMIworking paper
39).
 Barron, J., Rockström, J. Gichuki, N. Hatibu. (2003). Dry spell analysis and maize yields for two semi-arid locations in
East-Africa. Agriculture and Forest Meteorology 177: 23-27
 Cai, X.,and M. Rosegrant. (2003). World water productivity. In Kijne, J. W.; Barker, R.; Molden. D. (Eds.), Water
productivity in agriculture: Limits and opportunities for improvement. Wallingford, UK; Colombo, Sri Lanka: CABI; IWMI.
 Matsuno, Y, H. S. Ko; C. H. Tan; R. Barrer; G. Levine.( 2002). Accounting of Agricultural and Nonagricultural Impacts of
irrigation and drainage Systems. Working paper 43. . International Water Management Institute: Colombo, Sri Lanka.
 Garg, H.P. (1987). Advances in solar energy technology, Volume 3. Reidel Publishing, Boston, MA. Halcrow, S.W. and
Partners. 1981. Small-scale solar- powered irrigation pumping systems: technical and economic review
 Lemma Dinku. Smallholders’ Irrigation Practices and Issues of Community. Management: The Case of Two Irrigation
Systems in Eastern Oromia,Ethiopia. Faculty of Centre Pivot Irrigation System - Hortfresh Journal
drawings
Pivot drawing
ENGINEERING DESIGN
DESIGN Cont’d
BILL OF QUANTITIES
AREA (HA.) 100HACTARES
PRICED BILLS OF QUANTITIES
CENTRE PIVOT IRRIGATION SYSTEM
DESCRIPTION OF GOODS
U.O.M.
SALE
PRICE
KSHS
QTY
SUB-TOTAL
B
KES
-
IRRIGATION PIVOT UNITS
1 CENTRE PIVOT UNITS, VARYING SPANS; PIERCE CP 600; STD PROFILE
PCS
2
KES
6,000,000.00
SUB-TOTAL
C
KES
KES
12,000,000.00
12,000,000.00
PIPING AND HYDRANTS
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
8" HYDRANT CONTROL VALVE ASSEMBLY
8" WATER METER ASSEMBLY
3" AIR RELEASE VALVE ASSEMBLY
3" BALL VALVE
3" X 1 M RISER THREADED BOTH SIDES
200 MM PVC PIPE PN6
200 MM PVC FLANGE AND STUB
200 MM PVC BEND
8" X5" PVC REDUCER
8" GEAR TYPE BUTTERFLY VALVE
8" SPRING TYPE NON RETURN VALVE
8" PRESSURE REGULATING VALVE
PVC GLUE 1 KG
⅝“ x 8” steel bo lts and nuts
Hemp
Bo sswhite 0.25 kg
PCS
PCS
PCS
PCS
PCS
MTS
PCS
PCS
PCS
PCS
PCS
PCS
KGS
PCS
MTS
PCS
2
2
10
10
10
1950
8
4
2
3
3
3
125
164
125
125
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
50,000.00
100,000.00
25,458.13
10,910.63
6,982.80
1,703.27
10,910.63
17,457.00
11,638.00
34,477.58
30,113.33
153,476.13
2,182.13
363.69
2,182.13
2,182.13
SUB-TOTAL
D
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
KES
100,000.00
200,000.00
254,581.25
109,106.25
69,828.00
3,321,376.09
87,285.00
69,828.00
23,276.00
103,432.73
90,339.98
460,428.38
272,765.63
59,644.75
272,765.63
272,765.63
5,767,423.29
ELECTRO-MECHANICAL WORKS
1
2
3
4
5
6
7
8
CENTRIFUGAL ELECTRIC PUMP; 228 M³/ HR AT 68M HEAD; 75KW
SET
CENTRIFUGAL ELECTRIC PUMP; 146 M³/ HR AT 50M HEAD; 30KW
SET
ELECTRIC CONTROL PANEL 15KW
SET
ELECTRIC CONTROL PANEL 30 KW
SET
80 KVA POWER GENERATING UNITS
SET
8" SUCTION ASSEMBLY C/W FOOTVALVE
SET
8" DELIVERY ASSEMBLY
SET
5,000 LITER SEPARATE FUEL TANK
SET
1
1
1
1
1
2
2
1
KES
KES
KES
KES
KES
KES
KES
KES
701,916.88
545,531.25
185,000.00
235,000.00
3,200,000.00
427,332.81
463,701.56
1,883,901.25
SUB-TOTAL
E
SALE
AMOUNT
KSHS
KES
KES
KES
KES
KES
KES
KES
KES
KES
701,916.88
545,531.25
185,000.00
235,000.00
3,200,000.00
854,665.62
927,403.13
1,883,901.25
8,533,418.12
GENERATOR SETS
1 10-15 KVA GENERATOR SET COMPLETE WITH ACCESSORIES
SET
2
KES
690,000.00
KES
1,380,000.00
SUB-TOTAL
KES
1,380,000.00
SUB-TOTAL
KES
TOTAL FOR PIVOT SYSTEM
KES
ADD CONTIGENCIES
KES
8,763,500.02
GRAND TOTAL
KES
36,444,341.43
-
27,680,841.41
THANK
YOU