DESIGN OF AN INTEGRATED CENTRE PIVOT IRRIGATION SYSTEM

A case study of 100ha in Hola area in Tana River county

MUCHIRI JOSPHINE MUTHONIMUCHIRI JOSPHINE MUTHONI F21/2528/2009F21/2528/2009

Supervisor : Dr. J.P. ObieroSupervisor : Dr. J.P. Obiero

UNIVERSITY OF NAIROBIUNIVERSITY OF NAIROBI

DEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERINGDEPARTMENT OF ENVIRONMENTAL AND BIOSYSTEMS ENGINEERING

FEB 540: DESIGN PROJECTFEB 540: DESIGN PROJECT

2013/2014 ACADEMIC YEAR2013/2014 ACADEMIC YEAR

BACKGROUND

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.

Did you know that irrigation would help utilize the potentials of arid and semi arid areas in Kenya

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 average-increased 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 Irrigation Potential(Ha)Tana 205,000Athi 40,000Lake Victoria 200,000Kerio Valley 64,000Ewaso Ngiro 30,000Total 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.

METHODOLOGYMETHODOLOGY

Preliminary site visit and survey work was done

Inspection of Hola site

Study of the vegetation

Study of suitable crops in the area

Assessment of the infrastructure

Soil and water sampling and testing was done

Collection of agro-climatic data, included.

Identification of irrigation land

Collection of meteorological data, i.e. temperature and rainfall

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'dcont'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 collectionPrimary &secondary Determine system

parametersAnalysis of Soil infiltration rates

Pipe sizingSpeed and working hours of pivot

Flow requirementsof the system

Selecting pump, requirements and performance chart

Power rating 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: Q = 10 x 60.77 x 53mm/ (7 x 2 x 10) =230.05m3/hr

CP7 : 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

Operating angle

Length Area Pipe sizeIrr.Time

SystemFlow

Pump Power

degrees m ha. mm hrs m3/hr Head Rating

m kwCP2 360 439.2 61 900 200 6 8.3 20 228 35 30CP7 360 350.8 38 1096 200 6 8.3 20 146 25 15

CpsPipe length,m

CWRnet(mm/day)

CWR Gross(mm/day)

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 QUANTITIESAREA (HA.) 100HACTARES

PRICED BILLS OF QUANTITIES

CENTRE PIVOT IRRIGATION SYSTEM

SALE SALEDESCRIPTION OF GOODS U.O.M. QTY PRICE AMOUNT

KSHS KSHS

SUB-TOTAL -KES

B IRRIGATION PIVOT UNITS

1 CENTRE PIVOT UNITS, VARYING SPANS; PIERCE CP 600; STD PROFILEPCS 2 6,000,000.00KES 12,000,000.00KES

SUB-TOTAL 12,000,000.00KES

C PIPING AND HYDRANTS

1 8" HYDRANT CONTROL VALVE ASSEMBLY PCS 2 50,000.00KES 100,000.00KES 2 8" WATER METER ASSEMBLY PCS 2 100,000.00KES 200,000.00KES 3 3" AIR RELEASE VALVE ASSEMBLY PCS 10 25,458.13KES 254,581.25KES 4 3" BALL VALVE PCS 10 10,910.63KES 109,106.25KES 5 3" X 1 M RISER THREADED BOTH SIDES PCS 10 6,982.80KES 69,828.00KES 6 200 MM PVC PIPE PN6 MTS 1950 1,703.27KES 3,321,376.09KES 7 200 MM PVC FLANGE AND STUB PCS 8 10,910.63KES 87,285.00KES 8 200 MM PVC BEND PCS 4 17,457.00KES 69,828.00KES 9 8" X5" PVC REDUCER PCS 2 11,638.00KES 23,276.00KES

10 8" GEAR TYPE BUTTERFLY VALVE PCS 3 34,477.58KES 103,432.73KES 11 8" SPRING TYPE NON RETURN VALVE PCS 3 30,113.33KES 90,339.98KES 12 8" PRESSURE REGULATING VALVE PCS 3 153,476.13KES 460,428.38KES 13 PVC GLUE 1 KG KGS 125 2,182.13KES 272,765.63KES 14 ⅝“ x 8” steel bolts and nuts PCS 164 363.69KES 59,644.75KES 15 Hemp MTS 125 2,182.13KES 272,765.63KES 16 Bosswhite 0.25 kg PCS 125 2,182.13KES 272,765.63KES

SUB-TOTAL 5,767,423.29KES

D ELECTRO-MECHANICAL WORKS

1 CENTRIFUGAL ELECTRIC PUMP; 228 M³/ HR AT 68M HEAD; 75KWSET 1 701,916.88KES 701,916.88KES 2 CENTRIFUGAL ELECTRIC PUMP; 146 M³/ HR AT 50M HEAD; 30KWSET 1 545,531.25KES 545,531.25KES 3 ELECTRIC CONTROL PANEL 15KW SET 1 185,000.00KES 185,000.00KES 4 ELECTRIC CONTROL PANEL 30 KW SET 1 235,000.00KES 235,000.00KES 5 80 KVA POWER GENERATING UNITS SET 1 3,200,000.00KES 3,200,000.00KES 6 8" SUCTION ASSEMBLY C/W FOOTVALVE SET 2 427,332.81KES 854,665.62KES 7 8" DELIVERY ASSEMBLY SET 2 463,701.56KES 927,403.13KES 8 5,000 LITER SEPARATE FUEL TANK SET 1 1,883,901.25KES 1,883,901.25KES

SUB-TOTAL 8,533,418.12KES

E GENERATOR SETS

1 10-15 KVA GENERATOR SET COMPLETE WITH ACCESSORIES SET 2 690,000.00KES 1,380,000.00KES

SUB-TOTAL 1,380,000.00KES

SUB-TOTAL -KES

TOTAL FOR PIVOT SYSTEM 27,680,841.41KES

ADD CONTIGENCIES 8,763,500.02KES

GRAND TOTAL 36,444,341.43KES

THANK YOU