Service Contract No 2007 / 147-446 Mavela Farmers ... - Swaziland

Restructuring and Diversification 

Management Unit (RDMU) 

to coordinate the implementation of 

the National Adaptation Strategy to 

the EU Sugar Reform, Swaziland 

Service Contract No 2007 / 147-446 

EuropeAid/125214/C/SER/SZ: Restructuring and 

Diversification Management Unit to coordinate the 

implementation of the National Adaptation Strategy to the 

EU Sugar Reform, SWAZILAND 

EC General Budget – SU-21-0603 

SWAZILAND Technical Audit of Farmers Association 

M a v e l a F a r m e r s A s s o c i a t i o n 

Submitted to: 

The Delegation of the European Commission to Swaziland 

4 th Floor Lilunga House, Somhlolo Road, Mbabane, Swaziland 

Ministry of Economic Planning and Development 

P.O. Box 602 

Mbabane H100, Swaziland

Your contact persons 

with GFA Consulting Group GmbH are 

Dr. Susanne Pecher 

Anke Schnoor 

Restructuring and Diversification Management Unit 

(RDMU) 

to coordinate the implementation of the National Adaptation 

Strategy to the EU Sugar Reform, Swaziland 

Technical Audit of Farmers Association 

Authors: Tiekie de Beer 

& 

Bongani Bhembe 

Mission Report 

Address 

GFA Consulting Group GmbH 

Eulenkrugstraße 82 

D-22359 Hamburg 

Germany 

Phone +49 (40) 6 03 06 – 111 

Fax +49 (40) 6 03 06 - 119 

Email: afrika@gfa-group.de 

Mavela Farmer Association Report - 2009 

Page ii

DISCLAIMER 

The contents of this report are the sole responsibility of the RDMU and can in no way 

be taken to reflect the view of the European Union. 


Page iii

TABLE OF CONTENTS 

TABLE OF CONTENTS ................................................................................................................................. iv 

LIST OF TABLES ............................................................................................................................................ vi 

LIST OF FIGURES ......................................................................................................................................... vii 

LIST OF APPENDICES ................................................................................................................................ viii 

ABBREVIATIONS ........................................................................................................................................... ix 

1 INTRODUCTION ............................................................................................... - 1 - 

2 BACKGROUND ON IRRIGATION DEVELOPMENT ....................................... - 2 - 

3 TECHNICAL AUDIT REPORT ..........................................................................- 3 - 

3.1.1 REVIEW OF THE IRRIGATION DESIGN CRITERIA AND SPECIFICATIONS .........................- 3 - 

3.1.1.1 Irrigation Design and Specifications by the contractor ..............................................................- 3 - 

3.1.1.1.1 DESIGN CRITERIA ............................................................... Error! Bookmark not defined. 

3.1.1.1.2 LAYOUT ................................................................................. Error! Bookmark not defined. 

3.1.1.1.3 PUMP UNIT ............................................................................ Error! Bookmark not defined. 

3.1.1.1.4 STARTER AND ELECTRICAL CONNECTION .................. Error! Bookmark not defined. 

3.1.1.1.5 SUCTION AND DELIVERY FITTINGS ............................... Error! Bookmark not defined. 

3.1.1.1.6 MAINLINE .............................................................................. Error! Bookmark not defined. 

3.1.1.1.7 HYDRANTS ............................................................................ Error! Bookmark not defined. 

3.1.1.1.8 PORTABLE SPRINKLER EQUIPMENT .............................. Error! Bookmark not defined. 

3.1.1.1.9 IRRIGATION LATERALS ..................................................... Error! Bookmark not defined. 

3.1.1.2 Review of Contractor Irrigation Design Criteria and Specifications .........................................- 3 - 

3.1.1.2.1 Planning ................................................................................................................................- 3 - 

4 FIELD EVALUATION OF IRRIGATION SYSTEM ..........................................- 12 - 

4.1.1 Pumps And Pump Stations ...............................................................................................................- 12 - 

4.1.1.1 Pump Suction Side ...................................................................................................................- 12 - 

4.1.1.1.1 Suction Pipe Flow Rate .......................................................................................................- 12 - 

4.1.1.1.2 Requirements for Fittings ...................................................................................................- 13 - 

4.1.1.1.3 Suction Pipe Inlets ..............................................................................................................- 16 - 

4.1.1.1.4 Suction side losses ..............................................................................................................- 19 - 

4.1.1.1.5 Suction height .....................................................................................................................- 19 - 

4.1.1.2 Pump evaluation .......................................................................................................................- 21 - 

4.1.1.2.1 Power required on the pump shaft ......................................................................................- 21 - 

4.1.1.2.2 Pump Operation ..................................................................................................................- 22 - 

4.1.1.2.3 General ................................................................................................................................- 24 - 

4.1.2 Power Supply And Consumption .....................................................................................................- 26 - 

4.1.3 Supply System ..................................................................................................................................- 29 - 

4.1.3.1 Mainline size ............................................................................................................................- 29 - 

4.1.3.2 Mainline class ..........................................................................................................................- 30 - 

5 FIELD EVALUATION OF SPRINKLER IRRIGATION SYSTEM .................... - 31 - 

5.1 Pressure readings ................................................................................................................................- 32 - 

5.1.1 Pressure at hydrant ............................................................................................................................- 32 - 

5.1.2 Sprinkler pressure .............................................................................................................................- 33 - 

5.2 Delivery tests ........................................................................................................................................- 38 - 

5.2.1 Sprinkler discharge ...........................................................................................................................- 38 - 


Page iv

5.3 Distribution tests .................................................................................................................................- 41 - 

5.3.1 Importance of CU and DU ..................................................................... Error! Bookmark not defined. 

5.3.2 Christiansen’s uniformity coefficient (CU): .......................................... Error! Bookmark not defined. 

5.3.3 Distribution uniformity (DU): ............................................................... Error! Bookmark not defined. 

5.3.4 Application efficiency (AE): ................................................................. Error! Bookmark not defined. 

6 ASSESSMENT OF OPERATION, MANAGEMENT AND MAINTENANCE OF 

THE IRRIGATION SYSTEM .................................................................................. - 42 - 

6.1 Operation .............................................................................................................................................- 42 - 

6.2 Management Practices ........................................................................................................................- 45 - 

6.3 Maintenance Survey ...........................................................................................................................- 45 - 

6.4 Observations ................................................................................................. Error! Bookmark not defined. 

7 CONSTRAINTS TO EFFICIENT SYSTEM PERFORMANCE ........................- 47 - 

8 RECOMMENDATIONS ...................................................................................- 51 - 

9 CONCLUSION ................................................................................................- 54 - 

10 LITERATURE REFERENCES .....................................................................- 55 - 

11 PRODUCT INFORMATION .........................................................................- 59 - 

12 APPENDICES .............................................................................................- 65 - 


Page v

LIST OF TABLES 

TABLE 1. PUMP AND MOTOR SPECIFICATIONS AND MEASUREMENTS CONDUCTED ON ALL PUMPS .............. - 21 - 

TABLE 2. RIVER PUMPS EVALUATION ................................................................................................................ - 23 - 

TABLE 3. OPTIMAL OPERATING PRESSURE VS NOZZLE DIAMETER FOR SPRINKLERS ........................................ - 33 - 

TABLE 4. PRESSURE AND NOZZLE SIZE MEASUREMENTS RESULTS .................................................................... - 36 - 

TABLE 5. DISCHARGE VARIATION CALCULATED FROM FIELD MEASUREMENTS ................................................ - 39 - 

TABLE 6.TECHNICAL PROPERTIES OF SPRINKLERS FOUND ON SITE AT 35M OPERATING PRESSURE ................ - 40 - 

TABLE 7. MAINTENANCE SCHEDULE FOR SPRINKLER IRRIGATION SYSTEMS ..................................................... - 45 - 

TABLE 8. MAINTENANCE PRACTICES IMPLEMENTED BY MAVELA FA ................................................................ - 46 - 


Page vi

LIST OF FIGURES 

FIGURE 1. MAVELA INTAKE SUMP ALONG THE MBULUZI RIVER ......................................................................... - 2 - 

FIGURE 2. SAPWAT SCREEN INDICATING WATER REQUIREMENT FOR SPRINKLER IRRIGATION WITH RAINFALL 

TAKEN INTO ACCOUNT ................................................................................................................................ - 7 - 

FIGURE 3. REQUIRED RADIUS OF 90 BENDS (SOURCE: ARC (2007)) .................................................................. - 13 - 

FIGURE 4. 45° AND 90° BENDS ON RIVER PUMP SUCTION MANIFOLD ............................................................. - 14 - 

FIGURE 5. CONCENTRIC AND ECCENTRIC REDUCERS ......................................................................................... - 14 - 

FIGURE 6. CORRECT INSTALLATION OF ECCENTRIC REDUCERS ......................................................................... - 15 - 

FIGURE 7. CORRECT INSTALLATION OF ECCENTRIC REDUCERS ON ONE OF THE PUMPS .................................. - 16 - 

FIGURE 8. SPACING AND PLACING OF SUCTION PIPE INLETS............................................................................. - 17 - 

FIGURE 9. MAVELA INTAKE SUMP ALONG THE MBULUZI RIVER ....................................................................... - 17 - 

FIGURE 10. CLEANING OF THE INTAKE SUMP ALONG A HIGH FLOWING MBULUZI RIVER ................................ - 18 - 

FIGURE 11. MINIMUM WATER DEPTH ABOVE SUCTION PIPE INLET ................................................................. - 18 - 

FIGURE 12. ATMOSPHERIC PRESSURE VS. HEIGHT ABOVE SEA LEVEL ............................................................... - 20 - 

FIGURE 13. INSIDE MAVELA PUMP STATION ..................................................................................................... - 24 - 

FIGURE 14. MALFUNCTIONING DRAINAGE PUMP ............................................................................................. - 25 - 

FIGURE 15. LATERAL HYDRANT VALVE ............................................................................................................... - 32 - 

FIGURE 16. PRESSURE MEASUREMENT WITH A PITOT TUBE END PRESSURE GAUGE ............ - 34 - 

FIGURE 17. POSITIONS OF COMPLETE SPRINKLER PRESSURE MEASURES IN AN IRRIGATION BLOCK ............... - 35 - 

FIGURE 18. MEASURING APPARATUS FOR SPRINKLER NOZZLE SIZE ................................................................. - 37 - 

FIGURE 19. MAVELA FA SUGARCANE ABOVE RECOMMENDED TESTING HEIGHT ............................................. - 41 - 

FIGURE 20. MAVELA WEED INFESTED SUGARCANE ........................................................................................... - 43 - 


Page vii

LIST OF APPENDICES 

Appendix 1: SEB usage for river pump station phase 2 

Appendix 2: capital recovery factors (CRF) 

Appendix 3: soil map and block layout 


Page viii

ABBREVIATIONS 

Abbreviation 

AE 

ARC 

ASAE 

CU 

CV 

DU 

EAC 

EU 

FA 

GAR 

HDPE 

MCC 

NAR 

NPSH 

PVC 

RSSC 

SABI 

SE 

SSA 

SWADE 

Us 

Description 

Application Efficiency 

Agricultural Research Council 

American Society of Agricultural Engineers 

Christiansen’s uniformity coefficient 

Coefficient of Variation 

Distribution Uniformity coefficient 

Equivalent Annual Cost 

Emitter Uniformity 

Farmers Association 

Gross Application Rate 

High Density Polyethylene 

Motor Control Centre 

Net Application Rate 

Net Positive Suction Head 

Polyvinyl Chloride 

Royal Swaziland Sugar Corporation 

South African Irrigation Institute 

System Efficiency 

Swaziland Sugar Association 

Swaziland Water & Agricultural Development Enterprise 

Statistical Uniformity 


Page ix

1 I N T R O D U C T I O N 

Association general information 

1. Farm name: Swazi Nation Land 

2. Name of Association: Mavela Farmers Association 

3. Location: 

Latitude 61 000.00 

Longitude 2 895 200.00 

Altitude 310 

Maximum Temperature 36 

Minimum Temperature 8 

4. Postal address: 86 Tshaneni 

5. Contact Details: 

Chairman – Mr. E. Ndzimandze 605 8957 

Farm Supervisor- Mr. Magagula 611 8110 

6. Area of farm (ha) 62.4 

7. Crops irrigated: Sugarcane 

8. Designers name and details: G4 Farm and Estate Development 

9. Date of evaluation: 16 February 2009 

10. Evaluators: Tiekie de Beer and Bongani Bhembe 

Mavela Farmer Association Report - 2009 Page - 1 -

2 B A C K G R O U N D O N I R R I G A T I O N 

D E V E L O P M E N T 

Mavela Farmers Association’s irrigation system of 62.4 ha was designed and installed by G4 

Farm and Estate Development in two phases. The first phase was 50.2 ha and was 

commissioned in 1998; the second phase was completed in 2000 and was 12.4 ha. The 

designer was Mr. Kennedy Dlamini. 

2 . 1 T h e p r o j e c t 

‣ The entire project is a dragline irrigation system with a 54m lateral spacing and 18m 

draglines. 

‣ The project consists of one intake sump and one pump station housing two KSB pumps 

along the Mbuluzi River. 

Figure 1. Mavela intake sump along the Mbuluzi River 

‣ Phase two was an extension of phase 1 and an extra pumping unit was installed 

‣ Each lateral is isolated by a Bermad hydraulic valve with a mechanical choke for pressure 

regulation. 

‣ The sprinklers are not equipped with sprinkler pressure regulators which are necessary 

with the type of topography of this project. 

‣ The Motor Control Centres (MCC) of all pump stations are well designed and installed. 

‣ The project is developed on two soil sets the L and B sets 


3 T E C H N I C A L A U D I T R E P O RT 

3.1.1 R E V I E W O F T H E I R R I G A T I O N D E S I G N C R I T E R I A 

A N D S P E C I F I C A T I O N S 

3.1.1.1 Irrigation Design and Specifications by the contractor 

Design information from the designer and from the client’s representative during construction, 

Ubombo sugar, could not be obtained. The design was therefore checked against Swaziland 

Sugar Industry Standard and SABI norms shown below. 

3.1.1.1.1 DESIGN CRITERIA 

Crop 

Area under irrigation 

Gross Application 

Net Application 

Irrigated Cycle 

Sprinkler discharge 

Sprinkler Spacing 

Precipitation Rate 

Stand time 

Annual Irrigation hours 

Sugar Cane 

62.4Ha 

52mm 

39 mm per cycle (6.5 mm/day) 

6/7 days (depending on soil type) 

0.39 l/s 

18m x 18m 

4.3mm/hr 

12 hours (depending on soil type) 

3 300 hours 

3.1.1.2 Review of Contractor Irrigation Design Criteria and Specifications 

3.1.1.2.1 Planning 

Of the four major input of planning namely crop, climate, soil and irrigation system, the study 

revealed that crop and climate information used as supplied by the SSA (Swaziland Sugar 

Ass) Soil types were not taken into consideration during design and or implementation of the 

project. 


Attached in annexes is field Map 1, a soil map of Mavela FA indicating the two major soil 

types on which the project was developed. The contractor’s tender document where it states 

what drawings were issued to the contractor makes it is clear that the soil map was not given 

to the contractor but a schematic field layout and bulk water supply. 

The purpose of this study was to determine the quantity of water required by the crops per 

cycle during peak demand periods and how often it was to be applied taking practical 

operating practice into account. 

Taking soils into account the following planning schedule was developed: 

Peak Design-Norm For Sprinkler Irrigation At Mavela F A 

1 GENERAL INFORMATION 

1,1 Owner Mavela F A 

1,2 Farm Name - Number - Co-ordinates Swazi nation land 

1,3 Telephone number 

1,4 Area developed 

1,5 Water Allocation 

2 CLIMATE 

2,1 Month state Jan 

2,2 Weather station state Ubombo 

2,3 Evaporation mm/day 7mm A-Pan or 5mm Grass Factor 

3 MANAGEMENT 

3,1 Available working days per week days 7 

3,2 Available working Hours per day hours 24 

4 CROP BLOCK NO Lesibovu 

4,1 Type state Sugar 

4,2 Area Ha 20 

4,3 Plant spacing m NA 

4,4 Row spacing m 1.8 

4,5 Effective root depth m 0.45 

4,6 Plant time date August 

5 SOIL Lesibovu 

5,1 Effective soil depth m 1 

5,2 Water holding capacity mm/m 180 

5,3 Easy available water (10-50 kPa) 50% mm/m 90 

5,4 Easy available water in root zone mm 40.5 

6 WATER 


6,1 C en S Classification of water C+S Usuto River 

7 EMITTER 

7,1 Type type Vyrsa 70 Vyrsa 70 

7,2 Nozzle size mm 11/64 11/64 

7,3 Discharge l/h 1390 1390 

7,4 Working pressure kPa 350 350 

7,5 Application efficiency % 70 70 

7,6 Emitter spacing m 18 18 

7,7 Lateral spacing m 18 18 

7,8 Wetted diameter m 36 36 

7,9 Gross Application rate on wetted area mm/h 4.29 4.29 

7,10 Nett Application rate on wetted area mm/h 3.33 3.33 

8 SCHEDULING 

8,1 Crop factor (max) max 1.15 1.15 

8,2 Evaporation mm/day 5 5 

8,3 Evapotranspiration mm/day 5.75 5.75 

8,4 Net Irrigation requirement mm/day 5.75 5.75 

8,5 Gross Irrigation requirements mm/day 6.04 6.04 

8,6 Theoretical cycle length day 7.04 3.13 

8,7 Theoretical Stand time hour 12.16 5.40 

8,8 Practical Cycle length day 6 3 

8,9 Practical Stand time hours 12 6 

8,10 Working days per week days 7 7 

8,11 Irrigation hours per day hours 24 24 

8,12 

Gross application rate per practical 

cycle mm 51.48 25.74 

8,13 Gross application per month mm 220.62 257.40 

9 SCHEDULE OF BLOCKS THAT IRRIGATE TOGETHER 

10 HYDRAULICS 

10,1 Pressure difference over block m 40 40 

10,2 

Pressure at beginning of sub main or 

lateral m 40 40 

10,3 Velocity in mainline (max) m/s 1 1 

PRACTICAL STAND TIME / START TIME 

11 for 6 Day Cycle length 

Start End 

11,1 Position 1 

Day 1 

06,00 Day 1 18,00 


Day 1 

18,00 Day 2 06,00 


Day 2 

06,00 Day 2 18,00 


Day 2 

18,00 Day 3 06,00 


Day 3 

06,00 

Day 3 

18,00 









11,13 Position 1 start at beginning again 

Day 3 Day 4 

18,00 06,00 

Day 4 

06,00 Day 4 18,00 

Day4 

18,00 Day 5 06,00 

Day 5 

06,00 Day 5 18,00 

Day 5 

18,00 Day 6 06,00 

Day 6 Day06 

06,00 18,00 

Day 6 Day 7 

18,00 06,00 

Day 8 

06,00 

12 FILTER 

12,1 Type State 

12,2 Total total 

12,3 Filtration size micron 

12,4 Pressure loss over filter (clean) m 

12,5 Pressure lose over filter (dirty) m 

13 DESIGNER 

13,1 Name Tiekie de Beer 

13,2 Company Tiekie de Beer Consulting 

13,3 SABI Membership Designer Fellow 

Climatic information: 

Climatic information used when compiling the above schedule was obtained from SAPWAT 

and a summary of which is shown by the figures below. 


Figure 2. SAPWAT screen indicating water requirement for sprinkler irrigation with 

rainfall taken into account 

Soil information 

Soil properties used when compiling the aforementioned schedule was obtained from the 

below charts. These are the two major soils found within the farm, an outline of which is 

shown on a soil map attached in annexes. 






4 F I E L D E V A L U A T I O N O F I R R I G A T I O N 

S Y S T E M 

4.1.1 P u m p s a n d P u m p S t a t i o n s 

4.1.1.1 Pump Suction Side 

The majority of problems occurring with pumps are usually the result of poor suction side 

design and installation. The installation and design of the suction side must ensure that 

turbulence occurring in the suction pipe and collection of air in high places in the suction pipe, 

is prevented. In view of the above, the different suction side components were evaluated. 

4.1.1.1.1 Suction Pipe Flow Rate 

The suction pipe flow velocity of river and booster pumps was calculated as follows: 

353,68 Q 

V m / s 

2 

d 

……………………….… (1) 

Where: V = flow velocity in pipe (m/s) 

Q = flow rate (m³/h) 

d = inner diameter of suction pipe (mm). 

The design duty point both pumps is not known and for the purposes of the evaluation pump 

discharge was estimated by the multiplying of the total irrigated area (62.4 ha), industry 

norms of 2.57 sprinklers per hectare (for a 6 day cycle), 1.4m³/hr sprinkler discharge and 10% 

safety factor for pump discharge. The two pumps in this pump station must therefore 

generate 247m³/hr of flow to meet irrigation requirements. 

Based on equation one above the flow velocity at this pump discharge through the 250mm 

main suction manifold is duty point through the suction manifold is 1.46 m/s. From the main 

manifold a Y piece was constructed to the inlets of the two pumps. One leg of this one piece 

is 250mm and the other leg 200mm. The ETA 125-50/2 pump was installed with the first 

phase of 50.2 ha and flow through this section is 198.7m³/hr. Theoretically, these two legs 


have a flow velocity of 1.17 and 0.4 m/s respectively and there is not much deviation from 

these figures when half the total system flow is assumed to be generated by each pump. 

Flow velocities through the suction manifold are below the recommended maximum. 

According to the Agricultural Research Council, ARC (2007) the ideal suction pipe flow 

velocity must be 1.0 m/s, but suction pipe flow velocities up to 1.5 m/s are acceptable. A 

conclusion was therefore drawn that this pump house was designed correctly and the 

evaluated pump is operating optimally. 

4.1.1.1.2 Requirements for Fittings 

90º Bends 

The radius (mm) of a 90º bend must be, at least, as shown in Figure3 

r 

d 

Figure 3. Required radius of 90 bends (source: ARC (2007)) 

r 2d 

100 

mm 

…………………………………... (2) 

Where: r = radius of bend (mm) 

d = inner diameter of suction pipe (mm). 

Two 250mm 90° bends and one 250mm 45° bend was installed on the main suction manifold. 

The delivery manifolds from the two pumps has a total of two bends, a 45° and a 90° 150mm 

bend, inside the pump station. The radius of 250mm and 150mm bends are 275mm and 

190mm respectively. According to figure 4 and equation 2 above the required minimum are 


500 and 400mm respectively. There is more than five time the suction and delivery pipe size 

diameter pipe further on from these bends, hence the effects of the incorrect sizes were 

insignificant. 

Figure 4. 45° and 90° bends on river pump suction manifold 

Reducers 

The inlet on the pump suction side must be eccentric with the straight side towards the top, to 

prevent air collecting in the suction pipe and causing cavitation (ARC, 2006). The length of 

both eccentric and concentric reducers were evaluated against equation 3 (figure 5) below, 

adopted from the ARC. 

Figure 5. Concentric and eccentric reducers 


( d ) ………………………... (3) 

5 

2 

d1 

Where: = length of the reducer (mm) 

d1 = smaller inner diameter (mm) 

d2 = larger inner diameter (mm) 

A 125-200 eccentric reducer was installed on the suction side of pump ETA 100-50/2 and a 

150-250 eccentric reducer installed on the second pump, ETA 125-50/2. The delivery 

manifolds of these two pumps are of different sizes. Pump 1 manifold is attached to a 100- 

150mm concentric reducer and pump 2 is attached to a 125-200 concentric reducer. These 

reducers are installed as per the requirement but are of unacceptable dimensions. The 

eccentric reducer was installed with the straight side towards the top, to prevent air collecting 

in the pipe and concentric reducers on the delivery pipe (figure 6). 

The unacceptable dimensions of the concentric reducer had negligible effects on the 

performance of the pump and the entire system. The concentric reducer on the other hand is 

directly attached to the pump and the sudden restriction in size increases turbulence 

occurrences and cause irregular feeding of the pump hence cavitation. With such an 

installation wearing and maintenance cost of the pump would increase. 

Figure 6. Correct installation of eccentric reducers 


Figure 7. Correct installation of eccentric reducers on one of the pumps 

4.1.1.1.3 Suction Pipe Inlets 

Spacing and placing of suction pipe inlets 

The inlet of the suction pipe was not installed in accordance to the requirements of at least 

0,5d (d = inner diameter of the suction pipe) from the bottom of the pump sump (figure 8). 

The requirement that the suction pipe must be of at least 1,5d away from the side of the 

pump sump was not met here. 


d 

1.5d 

0.5d 

d 

3d 3d 1.5d 

Figure 8. Spacing and placing of suction pipe inlets 

An intake sump was constructed in 2002 after experiencing recurrent mechanical problems 

with their pumps. Measurements taken from this sump reflected that the requirements as 

shown in figure 8 above were not met. The foot valve is at least 100mm from the bottom of 

the sump, instead of 125mm and the suction pipe is about 500 and 600mm from the walls of 

the sump, instead of 750mm. The suction pipe is not permanently anchored onto the sump 

and can be adjusted to these requirements. 

Figure 9. Mavela intake sump along the Mbuluzi River 

The alignment of this sump in relation to the stream flow enables sand to be deposited inside 

the sump. In fact, when the river level is high Mavela loses irrigation time while cleaning the 


sand out of the sump. This can take up to a week and has to be corrected. During the dry 

season sand bags are used to divert water from almost the centre of the river. 

Figure 10. Cleaning of the intake sump along a high flowing Mbuluzi river 

The minimum water depth above suction pipe inlet depends on the suction pipe velocity and 

was evaluated using the graph shown in figure 11 below. Site investigation revealed a water 

depth of approximately 1.2m and with a maximum velocity of 1.46m/s the depth should be at 

least 0.8m. With the recommended velocities this depth is acceptable. At the minimum river 

level water depth decrease substantially. 

Figure 11. Minimum water depth above suction pipe inlet 


Foot valves 

The area around the foot valves was clean and the total area of the openings from the suction 

sieve was more than the minimum ARC requirement of 1.5 times larger than the crosssectional 

area of the suction pipe to prevent partial blockages of the suction sieve. 

Occasionally sand deposits inside the sump becomes too much so that pumping has to stop 

for cleaning purposes. 

4.1.1.1.4 Suction side losses 

During the evaluation of the pump station, attention was also given to the length of the 

suction pipe and fittings that were used. Friction losses for pipes were calculated as for any 

other pipe (using Hazen-Williams equation) and secondary losses for fittings were calculated 

with the aid of the following formula: 

h 

f 

 

6375kQ 

4 

d 

2 

………………………………….. (4) 

Where: hf = secondary friction loss in fitting (m) 

k = friction loss factor (annexure 1) 

Q = flow rate in the fitting (m³/h) 

d = inner diameter of the fitting (mm). 

A summation of friction loss across the foot valve, the suction pipe, and the 

eccentric/concentric reducers gave a total hf of 0.6 meters when both pumps are running. 

Friction in the suction pipe had a direct effect of maximum suction height and consequently 

the available net positive suction head (NPSH) and is discussed below. 

4.1.1.1.5 Suction height 

The essence of this evaluation was to determine the actual static suction head of the installed 

pumps and then compare it to the designers suction height assumption. The maximum 

suction height was calculated using equation 5 below; 


h 

s(max) 

hd 

hf 

hvp 

NPSH 

required ………………. (5) 

Where: hs (max) = maximum suction height (m) 

hd = atmospheric pressure on terrain (m) 

hf = suction side losses (friction losses, as well as secondary losses in fittings, m 

hvp = vapour pressure of water (m) 

NPSH required = net positive suction head from the pump curve (m). 

Figure 12. Atmospheric pressure vs. height above sea level 

The suction height was measured to be approximately 3 meters. The NPSH required of the 

100-50/2 (from a pump curve) is 1.6m and is 1m for the 125-50/2 pump. From the above 

formula the maximum allowable suction height is 7.2m and 8.32m for the two pumps 

respectively. This calculation confirms that river pumps were installed at the correct height 

above sea level. 

Further analysis compared NPSH available to NPSH required. NPSH requirements of 1.6 and 

1 meter are well within the available NPSH of 6.32 meters. A safety factor of 0.5 is not 

factored in this calculation as per manufacture’s requirement. 


4.1.1.2 Pump evaluation 

Table 1 below indicates Mavela irrigation pump specifications as observed from the 

information plate and tender document. 

Table 1. Pump and motor specifications and measurements conducted on all pumps 

PUMP SPECIFICATIONS FROM INFORMATION PLATE AND MEASUREMENTS 

Model KSB ETA 125 – 50/2 KSB ETA 100 – 50/2 

Number of units 1 1 

Estimated design duty point 198.7m³/h @ 66m 48.3m³/hr @ 66m 

Pump efficiency, % 78% 53% 

Impellor diameter mm 360 370/300 mm 

MOTOR SPECIFICATIONS FROM INFORMATION PLATE AND MEASUREMENTS 

Motor size, kW 55 30 

Revolution speed rpm 1475 1465 

Motor efficiency, % 93.6 92.9 

Power factor, cos Q 0.87 0.89 

Current (measured) V 380 380 

Voltage (measured) A 90 53 

4.1.1.2.1 Power required on the pump shaft 

The power required on the pump shaft was calculated as soon as the total pump head and 

delivery was measured. The pump efficiency was obtained from the pump curve. 

Power required on the pump shaft was calculated with the following formula and establishes 

whether motors were sized accurately. 

P 

g H Q 

36,000 

………………………………………. (6) 


Where: P = power required on the pump shaft (kW) 

ρ = density of water (1000 kg/m³) 

g = gravity acceleration (9.81 m²/s) 

H = pump pressure at service point (m) 

Q = pump delivery at service point (m³/h) 

η = pump efficiency at service point (%). 

With an operational duty points and pump efficiency shown in table 1 above, the required 

power on the pump shaft is a theoretical value of 45.8 kW and 16.4kW for the two pumps 

respectively. According the ARC, 2007, the power output of the motor must be 10-15% 

greater than the power required on the pump shaft and corresponds respectively to 52.7 and 

18.8kW. Under this consideration, the 55kW motor is correctly sized and 30kW motor was 

over-sized. 

This required power is calculated based on the assumption that the 125-50/2 pump was 

designed for phase 1 (50.2ha) and the 100-50/2 for phase two (12.2ha). If total system 

capacity requirements (247m³/hr) are divided equally between these two pumps (123.5m³/hr) 

their duty points change to 123.5m³/hr@73m and 69% efficiency for pump no.1 and 

123.5m³/hr@52m and 68% efficiency for pump no. 2. The power requirement will, change to 

40.9kW and 29.6kW respectively, inclusive of 15% safety for motor selection. Under this 

consideration the 55kW motor is over-specified and the 30kW is of the acceptable size. 

A conclusion was therefore drawn that in view of the above scenarios the total kW required in 

this project is about 71kW and the two motors generate a total of 85kW. This is not 

acceptable, especially from a financial point of view as it, unnecessarily, escalates electricity 

costs. 

4.1.1.2.2 Pump Operation 

Pump curves of all the pumps were to be used to evaluate whether these pumps function as 

indicated by the pump curve. Measurements of the operating pressure and discharge from 

these pumps were to be used to determine the required power by these pumps. But because 

no flow meters were installed in this project this exercise could not be carried out. 


The require power 

P 

required of all the pumps was then compared with the output power (Pu) of 

the electric motor obtained from measurements of voltage and current. The output power of 

the motor was calculated using equation 7 below 

3IV cos 

P u 

 

……………………………………….. (7) 

1000 

Where: Pu = output power of the motor (input power of the pump) (kW) 

I = average measured current (A) 

V = average measured voltage (V) 

η = motor efficiency (fraction) 

cos ø = power factor (factor). 

The output power of both motors is indicated in table 2 below, 

Table 2. River pumps evaluation 

KSB ETA 125 – 50/2 KSB ETA 100 – 50/2 

P motor (information plate) kW 55 30 

P required kW 52.7 / 40.9 18.8 / 29.6 

Pu (motor output power) kW 48.2 28.8 

Classification Acceptable Over-sized 

In view of the fact that the 125-50/2 pump was designed for phase 1 correctly, the 100-50/2 

motor is therefore over sized. According to the ARC the configuration of the different power 

units must conform to the expression Pu = P < Pmotor. A smaller motor could have been 

used in this development. 


4.1.1.2.3 Pump Station General Evaluation 

‣ The pump house is cramped with very little working space. 

Figure 13. Inside Mavela pump station 

‣ The entire floor of this pump house and the access ladder is slippery. This is caused by oil 

that is spilt during pump maintenance. Walking here has become a safety hazard. 

‣ The access ladder to this pump house is too steep and is not properly anchored. 

‣ The drainage pump is not working and water is removed from the pump house using 

buckets. The floor was initially draining to a small sump inside the pump house in which a 

small electric drainage pump was installed. This used to pump the drainage water out of 

the pump house via a network of pipes. 


Figure 14. Malfunctioning drainage pump 

‣ During heavy rains or when a sprinkler is run close to the pump house water seeps into 

the pump house from the floor. 

‣ Pumps and motors do not have any safety mechanism, i.e. no flow switches etc 

Pump Alignment 

The alignment of the pump and the motor was also evaluated. This was done by placing the 

edge of a straight steel ruler over the coupling flanges at four points, 90º apart. This straight 

edge rested equally on all points on the flanges to ensure parallel alignment. The distance 

between the coupling levels at 90º intervals was also measured. A Vernier calliper was used. 

Measurements were the same on all the points, and on all pumps and that meant the unit 

was squarely aligned. 


4.1.2 P o w e r S u p p l y a n d C o n s u m p t i o n 

Power consumption 

A basic economic analysis was undertaken to ascertain the trade-off between capital and 

energy costs. For this economic analysis the Equivalent Annual Cost method (EAC) was 

used. The EAC adjusts the costs of items to a stream of equal amounts of payment over 

specified periods (equivalent annual costs) in order to enable comparison. 

Items costed were: 

‣ Infield irrigation (tape and fittings including flusher lines and valves - considered as 

polythene). Including installation costs. 

‣ Distribution system - pipelines (main lines and submains - considered as PVC). 

Including installation costs. 

‣ Pumping plant (including pump control valves, flow meters, electrical components, 

motors etc). Included installation costs. Where no new pumps were included, all and 

any supplementary equipment/operations connected with pumping e.g. upgrades, 

new impellors, new switchgear, new valves were included 

‣ Primary filter station (only filters and associated pipe work, valves etc). 

Excluded were: 

‣ All existing infrastructure (e.g. AC pipe, balancing dam, MCC housing, etc) 

‣ Buildings (e.g. cluster houses, pump stations, filter station structure) 

‣ Valves external to pump stations and filter stations. 

‣ Irrigation controller systems 

‣ Fertigation systems 

The operational costs for the schemes were confined to energy costs and maintenance 

(excluded labour. Admin etc). 

Interest rate: 10% 

Useful life (this analysis) 

Infield irrigation (Tape etc): 

10 years 

PVC/Poly pipe: 

Filters: 

Pumping equipment and electrics 

20 years 

15 years 

15 years 


Maintenance 

Infield irrigation: 3% 

Distribution - pipelines: 2% 

Pumping plant: 1% 

Filters: 3% 

Capital Recovery Rate (CRF) 

factors: 

Volume water applied per hectare: 

SEB tariff – Consumption: 

Maximum demand: 

Efficiency of pumping plant 

(See attached table) 

14000m3/ha/annum 

0.22 E/kWh 

69.42 E/kVa 

Calculate at design duty point 

For sprinkler irrigation a 40% EAC value is accepted. A higher and a lower figure indicates 

over design and under design respectively 


ITEM COST ITEM Main Bid 

1 Infield irrigation 

Capital cost (E) 

Useful life (years) 10 

Annual maintenance (%) 3 

EAC of infield irrigation (E) 

2 Distribution system 




EAC of Distribution system (E) 

3 Pumping plant 




EAC of Pumping plant (E) 

4 Filters 

Capital cost (E) - 



EAC of Filters (E) - 

5 Annual Energy Cost (E) 78,825.46 

Total EAC (E) 

Energy cost as a % of total EAC 


4.1.3 S u p p l y S y s t e m 

The evaluation of the supply system is discussed under the following headings: 

4.1.3.1 Mainline size 

SABI norm suggests that for raising main lines with a diameter of 200mm or smaller a 

maximum of 1.5m friction fore ach 100 m pipe length (1.5%) is allowed (ARC, 2003). 

Mainlines with pipe sizes greater than 200mm are evaluated by determining the most 

economical pipe diameter; capital and annual cost for different pipe diameters were 

compared and the following equation is used; 

d 

kQ 

0.37 

i 

…..……………………….……… (8) 

Where: di = inside diameter of pipe, mm 

K= constant derived from annual irrigation hours 

Q= flow rate (m 3 /h) 

No information was available on mainline pipe sizes, lengths and class and because there 

are no pressure measuring points on hydrants, friction loss through the mainline could not be 

calculated. So an undisputed conclusion on whether the supply system was correctly 

designed or not cannot be drawn until details on pipe size, pipe classes, and distances 

occupied by the different sizes are obtained. 

For annual irrigation hours of 3300, adopted by the sugar industry, the most economical pipe 

size diameter from the pump station was calculated for 247 m³/hr maximum design flow to be 

217.3mm inside diameter. This corresponds to a 250mm nominal pipe size. The actual size 

installed could not be ascertained but a pipe size smaller would mean the system is underdesigned 

and vice versa. The total mainline length is approximately 1600m and based on the 

above norm friction head losses should not exceed 25m. 


4.1.3.2 Mainline class 

For the same reason as above, this evaluation could not identify whether the mainline classes 

were over specified or not. Pipe bursts are one major indicator of under specification in pipe 

classes and none were experienced in the mainlines. Recurrent pipe burst were observed 

only on T-off takes to sub mains. This could be caused by either water hammer or airlocks in 

the system. 

4.1.4 S y s t e m c a p a c i t y e v a l u a t i o n 

The required total head of pumps was calculated by summing the following; 

Friction loss in the mainline (25) 

The sprinkler operating head (35) + riser height (3m) 

The pump suction head (3m) 

Secondary head losses 

Elevation change from pump house to critical sprinkler (5m) 

The two pumps in this pump station irrigated a total of 62.4 ha and system capacity is 

therefore calculated to be 247m3/hr inclusive of 10% safety for pump discharge. The 

summation of the above components reflects that each pump must generate at least 71m. 

Assuming a motor efficiency at least 70% the required power for this project is 68.3kW, which 

is a 75kW motor. The total motor size was evaluated to be 85kW. This section is, therefore, 

over-designed. 

The 125-50/2 pump equipped with a 398mm impellor and coupled to a 75kW motor can meet 

the entire projects irrigation and pressure requirements. The current installation requires two 

pumps to be operated in order to meet irrigation and pressure requirements. Upon rectifying 

this design error the second pump will not be required, except for back-up purposes and 

power will be reduced by 10kW. 


5 F I E L D E V A L U A T I O N O F S P R I N K L E R I R R I G A T I O N 

S Y S T E M 

Block Area (ha) 62.4 

Type of sprinkler system 

Dragline 

Name of Designer 

G4 Farm and Estate Development 

Name of contractor 

G4 Farm and Estate Development 

Design 

Measured 

Hydrant pressure (m) Na No pressure measuring point 

Sprinkler spacing (m x m) 18 18 

Lateral spacing (m) 72 54 

Stand pipe height (m) 3 3 

Pressure regulator No No 

Dragline diameter (mm) 20 20 

Dragline length (m) Varies 20 


5 . 1 P r e s s u r e r e a d i n g s 

The following pressure readings were taken: 

5.1.1 P r e s s u r e a t h y d r a n t 

Hydrant valves were installed on every lateral and were equipped with mechanical valves. 

Pressure at the hydrant could not be measured due to malfunctioning pressure measuring 

point. Instead pressure was measured on the first hydromatic from the hydrant valve 

assembly. This was measured with a hand made pressure measuring apparatus, where by a 

pressure gauge, was connected to a hydromatic and pipelet, was used. Hydromatics on the 

delivery side of the hydrant were used as pressure measuring points. 

Figure 15. Lateral hydrant valve 

All mechanical hydrant valves must be replaced with hydraulic valves, i.e. Bermad valve with 

a pressure-regulating pilot to accommodate the variation in block required pressure. The 

installation of this unit would reduce a higher inlet pressure to a lower constant outlet 

pressure, regardless of fluctuating flow rates and or varying inlet pressure. The pilot would 

sense down-stream pressure and modulates open or close, causing the main valve to 

throttle, thus maintaining constant delivery pressure. 


When down–stream pressure falls below the pilot setting, the pilot and main valve would 

modulate open to increase pressure and maintain pilot setting. When downstream pressure 

rises above the pilot setting, the pilot and main valve would throttle close to decrease 

pressure and maintains pilot setting. The pilot has an adjusting screw to preset the desired 

pressure. 

5.1.2 S p r i n k l e r p r e s s u r e 

The optimal operating pressure (kPa) of the sprinkler should be between 60 and 70 times the 

nozzle diameter (mm). This is applicable to nozzles of 3 to 7 mm diameter (ARC, 2006). 

Table 3. Optimal Operating Pressure Vs Nozzle Diameter for Sprinklers 

Nozzle diameter 

Operating pressure (kPa) 

Mm inches x 60 x 70 

1,59 

1 / 16 " 

1,98 

5 / 64 " 

2,38 

3 / 32 " 

2,78 

7 / 64 " 

3,18 

1 / 8 " 191 222 

3,57 

9 / 64 " 214 250 

3,97 

5 / 32 " 238 278 

4,37 

11 / 64 " 262 306 

4,76 

3 / 16 " 286 333 

5,16 

13 / 64 " 310 361 

5,56 

15 / 64 " 333 389 

5,95 

15 / 64 " 357 427 

6,35 

1 / 4 " 381 445 

Pressure at sprinklers was measured with a pressure gauge, fitted with a pitot tube (Figure 

16). The point of the pitot tube was held about 2 mm in front of the nozzle opening in the path 

of the jet of water to measure the “vena contracta”. Therefore, the velocity pressure, which 

indicates the pressure head and is equivalent to the total pressure, was measured. 


Figure 16. Pressure measurement with a pitot tube end pressure gauge 

The standpipes were three metres high and the pressure of the sprinklers was measured at a 

height of one metre above the ground, then 2 m (or 20 kPa) was subtracted from the 

pressure registered on the pressure gauge, in order to determine the sprinkler pressure at 

normal operating height. 

The choice of the sprinklers at which measurements were to be taken, was influenced by the 

different pressure zones in a specific irrigation block. In view of the undulating terrain (many 

height differences) in this project the total system was in operation as for normal irrigation 

before the evaluation. According to the ARC (2006) the number of measuring points must be 

representative of the block and the choice depended on the topography of the block, as well 

as the distance from the pump station. As per these recommendations complete 

measurements were taken at distances 0, L/4, L/2, 3L/4 and L on the lateral and at the same 

distance on the sprinkler lines (Figure 17). 


0 L/4 L/2 3L/4 L 

L 

3L/4 

L 

L/2 

Test block 

L/4 

Test emitter 

0 

Hydrant 

Figure 17. Positions of complete sprinkler pressure measures in an irrigation block 

Pressure variation was calculated using equation 9 below and a summary of the results is 

outlined in table 8. 

Pmax 

P 

P 

P 

ave 

min 

………………………………………….. (9) 

According to the SABI norms, pressures in the block may not vary more than 20% of the 

average pressure. Pressure measurement results as indicated by the table below reflect an 

unacceptable pressure variation of 86.9%. The lowest pressure measurements were 

recorded from block 1, the first block from the pump house. When these are excluded 

pressure variation reduces to 32%, which is also unacceptable. The reason block 1 recorded 

the least pressure could not be confirmed but was attributed to the incorrect sub main and/or 

lateral design, leakages, and hydrant valve malfunctioning. 


Table 4. Pressure and nozzle size measurements results 

Measuring point Type of sprinkler/nozzle Measured 

nozzle 

diameter 

Measured 

nozzle pressure 

Block 1 Rain bird 14070 11/64" nozzle 4.5 165 



Block 2 VYRSA 70 11/64'' nozzle 4.37 480 



Block 4 RC 130 11/64'' nozzle 4.37 440 




Averages 4.412 4.464 362.5 

The installed pumps can meet the pressure requirements of this scheme; the operating 

average pressure of the system is above the recommended sprinkler operating pressure. The 

high system operating pressure and the unacceptable pressure variation was attributed to: 

Hydraulic Valves 

In essence hydraulic valves maintain the design lateral/block pressure ensuring uniform 

pressure thoughout the system. This irrigation system was installed in such a way that all 

laterals have individual isolation valves. Mechanical valves, instead of hydraulic valves are 

used in this installation hence the unacceptable variation in pressure. Sprinkler pressure 

ranges from 165kPa – 480kPa, with the installation of hydraulic valve sprinkler pressure will 

be maintained at the recommended sprinkler operating pressure of 350kPa in all blocks. 

Sprinkler pressure regulators 

Sprinkler pressure regulators were not installed. 350kPa sprinkler pressure regulators are 

required because these ensure that all nozzles operate at a maximum pressure of 350kPa, 

which is the recommended sprinkler operating pressure. Most blocks are fairly flat, when 

considering the quantity of the pressure regulators, this fact must be kept in mind. 

Nozzle wearing 

The amount of sprinkler nozzle wear (mm) is on average 2.2% in all phases. An increase of 

5% in nozzle area means a 10% increase in flow and power demand, which means additional 

operating costs and over-irrigation. The ARC therefore recommends sprinkler replacement if 


wear is greater than 5%. This irrigation system has been operated for almost 10 years but 

nozzle wearing is still low. The amount of sand particles sucked by booster pumps and pass 

through the nozzles is minimised as most of the sand carried from the river is deposited in the 

reservoir. Scour valves for facilitate cleaning of the pipe work are well installed in all submains. 

Sprinkler nozzles were measured after the system was switched off with a specially machined 

apparatus (Figure 18) 

Figure 18. Measuring apparatus for sprinkler nozzle size 

Number of sprinklers operated concurrently per lateral 

The lateral design is based on the number of sprinklers operating simultaneously on that 

lateral. Generally, the greater the number of sprinklers operating simultaneously, the bigger is 

the size of that lateral. When the farmers are irrigating they tend to connect sprinklers on all 

available hydromatics in that lateral and this severely increases friction loss within that lateral 

and mainline section thus reducing sprinkler pressure. The exact number of sprinklers per 

lateral must be indicated in the operation and maintenance manual. 

Leaks 

There are a lot of leaks in the system and this drastically reduces pressure. These leaks are 

observed mainly in sprinklers, sprinkler stand-dragline connections, broken dragline, pipelets, 

hydromatics, mainline, etc. 


Old Age 

The irrigation system was installed in 1998 and 200, over 10 years ago and as years elapsed, 

system efficiency reduces due to equipment wearing out. As a matter of urgency some 

equipment must be replaced and the rest maintained for optimal performance. Apart from 

nozzles, sprinklers, due to old age, are underperforming. Some draglines have more than the 

allowed tolerance of three joints and hydrant valves are faulty. These and other equipment 

has to be replaced. 

5 . 2 D e l i v e r y t e s t s 

The following delivery tests were conducted: 

5.2.1 S p r i n k l e r d i s c h a r g e 

According to the ARC the difference in discharge in a specific irrigation block may not vary by 

more than 10% from the average discharge, hence this evaluation. The discharge of the 

sprinklers was tested by collecting water into a container of known volume with a hose pipe 

connected to the sprinkler nozzle. A minimum container size of 20 litres is recommended and 

together with a stopwatch the time it took to fill the container was recorded. The open end of 

the hose pipe was not held under water in the container, but also not so high that the water 

splashed out of the container. 

Measurements were again taken at distances 0, L/4, L/2, 3L/4 and L on the lateral and the 

sprinkler line. The same points where pressure measurements were done were used and by 

taking the time it took to fill the container, the discharge was calculated with the following 

formula and results are shown in table 4. 

q 

e 

= 

average volume water measured incontainer 

average duration to fill container (sec) 

(litres) 

 

3600 

1000 

…………… (10) 

 

m 

3 

/hour 

Where q e = sprinkler discharge [m 3 /h] 


Table 5. Discharge variation calculated from field measurements 

Type of sprinkler/nozzle size 

Measured nozzle discharge (m3/hr) 

Rain bird 14070 11/64" nozzle 1.00 



VYRSA 70 11/64'' nozzle 1.45 



RC 130 11/64'' nozzle 1.19 




Minimum Discharge (m 3 /hr) 1.00 

Maximum Discharge (m 3 /hr) 1.73 

Average Discharge (m 3 /hr) 1.32 

Flow variation (%) 55.18 

Flow variation in this irrigation development was above the recommended maximum of 10% 

averaging a high of 55.18%. The average sprinkler application was found to be 1.32m³/hr 

instead of 1.4m³/hr stipulated in the Swaziland sugar industry standards. Again, when block 1 

sprinklers are eliminated the average sprinkler application improves to 1.38m³/hr. Sprinkler 

operating pressure and sprinkler discharge is directly proportional. When pressure 

decreases, sprinkler nozzle discharge also decreases and vice versa. This therefore, means 

all factors contributing to the low system pressure also contribute to the sprinkler nozzle 

discharge. The sprinklers that recorded a high operating pressure but low application rate had 

leaking draglines, tripods, and/or hydromatic-pipelet connection. 

The high nozzle/emitters variation observed in this project is one of the major reasons for the 

unacceptable flow variation. Different emitters respond differently to the same amount of 

pressure and table 6 below indicates the properties of the different sprinkler packages found 

on site. 


Table 6.Technical properties of sprinklers found on site at 35m operating pressure 

Sprinkler Package Nozzle size Discharge (m3/hr Wetted Radius (m) 

VYRSA 70 11/64’’ 1.36 15.9 

Rain bird 14070 11/64’’ 1.39 14.8 

Rain bird 14070 3/16’’ 1.65 15.8 

RC 130 11/64’’ 1.36 15.9 

Three sprinkler packages with four different sprinkler–nozzle combinations were identified as 

shown in table 6 above. Flow variation due to the different sprinkler – nozzle combinations is 

20.14%, that is, emitter variation contributes more than 20% to the high flow variation 

observed in this project. This figure indicates that even on highly efficient pumping and supply 

system, irrigation efficiency will not improve, at least not until uniformity in this regard is 

obtained. The different combinations have an effect on the wetting diameter due to their 

different body trajectory angles. Farm management is using Somlo 46c plastic sprinklers with 

a 3/16’’ nozzle as replacement stock. In fact, since commissioning this development have 

fewer sprinklers than required. They are currently using 130 sprinklers instead of 161 

sprinklers. 

Gross application rate (GAR) 

The gross application rate (GAR) of the sprinkler was thereafter calculated, by means of the 

following formula; 

GAR 

qe 

1000 

A ....…………………………………. (11) 

mm/h 

Where; GAR = Gross Application Rate 

A = wetted area (m 2 ) 

The recommended GAR according to industry norms is 4.33mm/hr and above calculation 

revealed an average of 4.1mm/hr and 4.2mm/hr without block 1 measurements. The GAR is 

a fraction of emitter discharge and sprinkler spacing. This low GAR is mainly caused by low 

sprinkler application rates. 


5 . 3 D i s t r i b u t i o n t e s t s 

This test could not be conducted because of the crop height (figure 19). The top of the rain 

gauge must not be more than 300mm above the ground surface or above the crop (ARC, 

2007). The test would be erroneous if carried out under these conditions because the 

vegetation would intercept the water distributed by the sprinklers and rain gauge readings 

would be incorrect. 

Figure 19. Mavela FA sugarcane above recommended testing height 


6 A S S E S S M E N T O F O P E R A T I O N , M A N A G E M E N T 

A N D M A I N T E N A N C E O F T H E I R R I G A T I O N 

S Y S T E M 

6 . 1 O p e r a t i o n 

As-built drawings and design information not available 

The fact that no design or installation information is available consigns a huge constraint on 

management. Forward planning on aspects related to the irrigation infrastructure cannot be 

done, i.e. replacement stock purchase; item like pipes, fittings, etc are procured after 

breakages because the details of that particular pipe, fitting, etc is obtained from the broken 

part. This increases their down time and negatively impacts on crop production. 

Operation and maintenance manual not available 

The different components forming the irrigation system require different operating procedures 

and these are obtained from an operation and maintenance manual. This document, like all 

other documents, is not available and for efficient performance of these components, it must 

be compiled. The consequence of not having this document is seen during this evaluation in 

that incorrect sequences are followed in opening and closing the pump. Also, this document 

helps in the formulation of a maintenance plan and provides guidelines to be followed during 

maintenance. 

Financial viability for smallholder grower 

The late conclusion of loan agreements (seasonal loans) results in the late delivery of inputs 

and late application of fertilizers and chemicals, which reduces yields and sucrose content, 

resulting in reduced financial returns per hectare and inability to recoup invested capital. In 

addition, the absence of any dividends for distribution to farming association members at the 

end of each season can lead to a decline in the cohesion of farmers’ associations/cooperatives, 

a cohesion which is essential to increasing on-farm efficiency. 


Figure 20. Mavela weed infested sugarcane 

Interest Rates 

It can be argued that even relatively large reductions in interest rates have not had any 

significant impact on the sustainability of this sector. The sector appears to have deteriorated 

to one of a sustained financial crisis. This calls for an integrated programme of action, to look 

at: 

‣ Discounted tariffs with regards to bank charges, including administration fees. 

‣ A re-look at the repayment period with regard to capital loans, with a view to having it 

extended from the current 7 years to at least 10 years 

Considering the reduction of interest rates on all loans to a level not exceeding 12% per 

annum, such measures would allow smallholder growers to realize some return on their 

investment and to be able to eventually pay dividends to the investing members. Alternatively 

other financial arrangements can be put in place without any prejudice to the commercial 

operations of the financial institutions currently engaged with the sector (SSA, 2008). 

Electricity 

Energy costs are too high. During dry periods this FA shifts to a 24 hours day with three 8 

hour shifts. This means the pumps run continuously for 24 hours per day. There is a need to 


have the tariffs looked at and, maybe have the tariff rate discounted for sugar cane growers 

to enable them to be sustainable in the business. It is imperative to train the farm manager 

and/or pump attendants on when and how many pumps to start at a time as this affects 

electricity maximum demand. Appendix three shows a calculation of the amount of energy 

used by this FA and compares it to what should have been used per season. This maximum 

demand calculation gives an indication of the amount small growers spend on electricity and 

how much could have been saved when pumps are operated correctly. 

Production Costs 

Sugar prices are on a continual downward spiral whereas production costs have taken the 

opposite direction, so that if no immediate plan of action is formulated to address the 

problem, most smallholder growers will slowly but surely perish. Fertilizers, herbicides, farm 

inputs, labour costs are making it difficult for the farmers to use the best farming practices. 

Maybe a solution to the problem could also be a consortium that can be formed for the 

sugarcane growing industry to have a muscle where buying of farm inputs is concerned 

(SSA, 2008). 

Transport costs 

Smallholder growers feel transporters have established a gold mine at the expense of 

growers. A large chunk of sugarcane revenue goes to the transporters and growers feel that 

there is a need to address this issue and look at ways to improve the current situation. The 

non performance of transport operators leads to a heavy loss in cane quality which also leads 

to a serious financial loss to the growers. The issue of mill distance from the farm is, in a 

number of instances, of major concern. The mere construction of a bridge (s) across a 

stream(s) would go a long way towards reducing these distances and, consequently, the 

attaching costs. 

Millers 

Smallholder cane growers feel that millers also have a significant role to play in assisting 

smallholder growers technically, financially and otherwise. Bulk purchasing comes to mind 

here as the millers are endowed with the financial muscle (economies of scale) which could 

result in discounted input prices for growers (SSA, 2008). 


6 . 2 M a n a g e m e n t P r a c t i c e s 

Scheduling 

Effective scheduling ensures that the correct amount of water is applied at the right time and 

the correct place. As a scheduling method Mavela FA uses the give and take method. This 

method utilizes long term evaporation means and rainfall is accounted through rain gauge 

readings. An 8 hr stand time, and a 7 day cycle is adopted. Two shifts starting at 0600hrs – 

1400hrs – 1700hrs (finishing the next day) are implemented. The shortage of sprinklers 

complicates this exercise in that some blocks that have an irrigation cycle of more than 7 

days. During dry periods a 24 hour working day is implemented and this means sprinklers are 

moved at night, around 2200hrs. 

6 . 3 M a i n t e n a n c e S u r v e y 

When the impact of maintenance practices was evaluated, it was decided to classify the 

existing maintenance practices followed by the producer, according to existing literature 

sources as acceptable if it will not influence the performance of the system adversely and 

unacceptable/ineligible if it will impair the performance. The acceptable values are viewed as 

the absolute minimum values for the sustaining of an acceptable Us value in the system 

Table 7. Maintenance schedule for sprinkler irrigation systems 

Inspect the system for leakages 

Monitor With each cycle Annually 

Check system pressure and system flow 

Service air valves and hydrants 

Check sprinklers for wear and replace springs, 

washers and nozzles where necessary 

Flush mainlines 

X 

X 

X 

X 

X 


Table 8. Maintenance practices implemented by Mavela FA 

Monitor Results Classification 

Inspect the system for leakages Attend to leaks only Unacceptable 

Check system pressure and system flow Never Unacceptable 

Service air valves and hydrants Never Unacceptable 

Check sprinklers for wear and replace springs, 

washers and nozzles where necessary 

Never 

Unacceptable 

Flush mainlines Annually Acceptable 


7 C O N S T R A I N T S T O E F F I C I E N T S Y S T E M 

P E R F O R M A N C E 

PUMPS 

‣ The alignment of this sump in relation to the stream flow enables sand carried with the 

river water to be deposited inside the sump. In fact, when the Mbuluzi River is high 

Mavela loses irrigation time cleaning the sand out of the sump. This can take weeks. 

Also, during the dry season, due to river recession, sand bags are used to re-direct water 

from almost the centre of the river into the sump. 

‣ The suction pipe is not constructed to the correct dimensions in relation to the intake sump 

walls. The foot valve is installed too close to the bottom and the suction pipe is too close 

to the walls of the sump. These are not permanently anchored onto the sump and can be 

adjusted to meet the requirements. 

‣ The main suction manifold has a flow velocity of 1.46m/s, this is on the limits of the 

recommended velocity range and pump performance is negatively affected. 

‣ Incorrectly sized fittings in suction and delivery manifolds affect system performance. The 

effects of these are severe on the eccentric reducer because it is directly attached to the 

pump and the sudden restriction in size increases turbulence occurrences and cause 

irregular feeding of the pump hence cavitation. With such an installation wearing and 

maintenance cost of the pump will increase. 

‣ The power rating of both motors on site (85kW) is more than the expected 75kW. This is 

an indication of over-design hence more energy than required is used. 

‣ The pumps specified and installed in this project can supply much more than the required 

247m³/hr. The 125-50/2 pump equipped with a 398mm impellor and coupled to a 75kW 

motor can meet the entire projects irrigation and pressure requirements. The 100-50/2 

pump is not required, unless for backup purposes. Again, this is an indication of overdesign. 

‣ The absence of pressure and flow measuring devices in pump number 2 delivery manifold 

makes it impossible to measure and/or monitor pump performance. 

‣ The river pump house is characterised by poor floor drainage, steep access ladder, 

unavailability of working space, etc. 


MAIN LINE 

‣ An undisputed conclusion on whether the supply system was correctly designed or not 

cannot be drawn until details on pipe size, pipe classes, and distances occupied by the 

different sizes are obtained. 

‣ Pipe bursts are one major indicator of under specification in pipe classes and none were 

experienced in mainlines. Recurrent pipe burst were observed only on T-off takes to sub 

mains. This could be caused by either water hammer or airlocks in the system. 

‣ Some Air valves were leaking – overall system efficiency compromised 

SPRINKLER INFIELD IRRIGATION 

‣ On average irrigation blocks in this development received pressure above the 

recommended sprinkler operating pressure but the average sprinkler application rate is 

lower than required. 

‣ This dragline irrigation development has a design lateral spacing of 54m and 20m 

draglines. Site measurements revealed a lateral spacing of at most 55m and 25m 

draglines. 

‣ Sprinklers are not equipped with pressure regulators and were running on different 

pressures and deliveries. 

‣ Lateral hydrants are equipped with mechanical instead of hydraulic valves. Hydraulic 

valves maintain the recommended sprinkler operating pressure, throughout the block, 

ensuring uniform application throughout the system. 

‣ There is a huge variation in sprinkler packages and nozzle sizes. This variation means that 

even on highly efficient pumping, conveyance and distribution system irrigation efficiency 

will not improve, at least not until uniformity in this regard is obtained. The different 

sprinkler packages have an effect mainly on the wetting diameter due to the different 

body trajectory angles and the nozzle sizes have an effect on flow rate. 

‣ When the farmers are irrigating they tend to connect sprinklers on all available 

hydromatics in that lateral and this severely increases friction loss within that lateral and 

mainline section thus reducing sprinkler pressure. 

‣ There are a lot of leaks in the system and this drastically reduces pressure. These leaks 

are observed mainly in the sprinklers, sprinkler stands and dragline connections, and 

broken draglines. 


‣ The first phase of the irrigation system was installed over 10 years ago, and as years 

elapsed, the system efficiency reduces due to equipment wearing out. As a matter of 

urgency some equipment must be replaced and the rest maintained for optimal 

performance. 

‣ The distribution test could not be carried out because the sugarcane crop is almost 

reaching full canopy. There is no place for placing the gauges within the block without 

inference from the crop. 

‣ The whole irrigation development has no drainage and subsurface and surface drains are 

required. 

‣ Sprinkler nozzle wear is up to 2.2% 

‣ Pressure and flow measurement results as indicated an unacceptable pressure and flow 

variation of 86.9% and 55.18% respectively. 

OVERALL MANAGEMENT AND MAINTENANCE 

Operations 

‣ Financial viability for smallholder grower 

‣ High Interest Rates 

‣ Electricity cost high 

‣ High Transport costs 

‣ High Production Costs 

Management and maintenance 

‣ No scheduling measurements were followed 

‣ Areas that require drainage are difficult to manage 

‣ Without an operation and maintenance manual, management have difficulty in operating 

and maintaining the system. Incorrect operation procedures are followed and improper 

maintenance schedules adopted. 

‣ The fact that no design or installation information is available consigns a huge constraint 

on management. Forward planning on aspects related to the irrigation infrastructure 

cannot be done, i.e. replacement stock purchase; item like pipes, fittings, etc are procured 


after breakages because the details of that particular pipe, fitting, etc is obtained from the 

broken part. 

‣ Old equipment reduces efficiency of system. This equipment includes hydromatics, 

draglines, tripod stands, sprinkler and nozzles. The most economic decision would be to 

replace this equipment instead of maintenance. 

‣ The different soil series on which the project is developed has different water holding 

properties and require different irrigation patterns. These are difficult to manage. 


8 R E C O M M E N D A T I O N S 

To evaluate the constraints of the project properly we have decided to categorised the 

recommendations in four categories namely 

A. Immediately: This has to been done direct after harvesting. 

B. Short term: This has to been done this season 

C. Medium term: This has to been done before replant 

D. Long term: This has to be rectified with replant. 

PUMPS 

Immediately: 

‣ Modify design of intake sump to minimise amount of sand carried with the river water and 

deposited inside the sump E 50 000.00 

‣ Upgrade 125-50/2 pump to run on full capacity e.g. install full size impellor and 75kW 

motor then disconnect the 100-50/2 pump E 80 000.00 

‣ Rehabilitate pump house, i.e. fix drainage pump, attend to seepage problem, etc 

E 10 000.00 

Medium term: 

‣ Reposition suction manifold on the sump ensuring that the required dimensions from the 

sump walls are met E 15 000.00 

‣ Replace all incorrectly dimensioned fittings on the suction and delivery manifold with the 

correct size E 5 000.00 

‣ Install flow meter, pressure gauges, pump and motor safety, etc E 50 000.00 

‣ Do routine maintenance on all equipment. E 5 000.00 

Long term: 

‣ Replace the suction pipe with a bigger size. E 35 000.00 


MAIN DISTRIBUTION LINE 

Immediately: 

‣ Fix all leaking air valves and control valves. E 2 500.00 

‣ Identify pipe sizes, lengths, classes and orientation of mainline 

‣ Install additional air valves E 7 500.00 

Short term: 

‣ Do routine maintenance on all equipment. E 2 500.00 

SPRINKLER INFIELD IRRIGATION 

Immediately: 

‣ Install hydraulic valves in place of mechanical vales E 35 000.00 

‣ Install identical sprinklers with identical nozzle sizes and of the acceptable quantity 

(2.57sprinklers/ha) E 25 000.00 

‣ Fix all damaged sprinkler stands and replace leaking draglines and other malfunctioning 

equipment E 25 000.00 

Long term: 

‣ Replant the areas that perform badly. 

‣ Equip all sprinklers with pressure regulators ` E 20 000.00 

‣ Install proper sub-surface and open drainage where possible E 80 000.00 

‣ Abandon soils with a poor potential, and plant alternative crops 

OVERALL MANAGEMENT AND MAINTENANCE 

Operations 

‣ Considering the reduction or termination of interest rates on all loans, such measures 

would allow smallholder growers to realize some return on their investment and to be able 

to eventually pay dividends to the investing members. Alternatively other financial 


arrangements can be put in place without any prejudice to the commercial operations of 

the financial institutions currently engaged with the sector. 

‣ There is a need to have the electricity tariffs looked at and, maybe have the tariff rate 

discounted for sugar cane growers to enable them to be sustainable in the business. 

Pump attendance must be trained on economic ways of operating pumps. 

‣ A consortium could be formed for the sugarcane growing industry to have a muscle where 

buying of farm inputs is concerned. This could reduce production costs 

Management 

‣ A proper scheduling tool must be adopted and, where possible, blocks scheduled 

according to soil type. 

‣ Compilation of an operation and maintenance manual to assist in the implementation of a 

proper maintenance strategy for the association. 

‣ Establish arrangement with a reliable establishment to assist with the maintenance of all 

equipment. 

‣ Replace all old equipment 


9 C O N C L U S I O N 

This 62.6ha dragline irrigation development was designed and constructed by G4 Farm and 

Estate Development in two phases. The first phase of 50.2ha was constructed in 1998 and in 

2000 the second phase of 12.4 ha was completed. Mavela is an association of 15 members 

and is situated in Dvokolwako, supplied by Mbuluzi River. 

Pump Station 

An intake sump was constructed in 2002 after experiencing recurrent mechanical problems 

with their pumps. The alignment of this sump in relation to the stream flow enables sand 

carried with the river water to be deposited inside the sump. In fact, when the Mbuluzi River is 

high Mavela loses irrigation time cleaning the sand out of the sump. This can take weeks. 

Also, during the dry season, due to river recession, sand bags are used to re-direct water 

from almost the centre of the river into the sump. To eradicate this problem E 50 000.00 will 

be sufficient. 

The suction pipe is not constructed to the correct dimensions in relation to the intake sump 

walls. The foot valve is installed too close to the bottom and the suction pipe is too close to 

the walls of the sump. These are not permanently anchored onto the sump and can be 

adjusted to meet the requirements. 

The electricity cost of this scheme is magnified by the fact that the power rating of both 

motors on site (85kW) is more than the expected motor rating 75kW. The 10kW difference in 

energy is power not required and the farmers are paying for it. The pumps installed in this 

project are also over designed; they can supply much more than the required 247m³/hr. The 

125-50/2 pump equipped with a 398mm impellor and coupled to a 75kW motor can meet the 

entire projects irrigation requirements. The 100-50/2 pump is not required, unless for backup 

purposes. Various alternatives are available to solving this design error but E80 000.00 is 

sufficient to upgrade the 125-50/2. 

The incorrectly dimensioned eccentric reducer installed on the suction manifold of the pump 

could cause damage to the pump on the long term. To refurbish this and all other fittings will 

cost approximately E5 000.00 


Main Distribution Line 

An undisputed conclusion on whether the supply system was correctly designed or not 

cannot be drawn until details on pipe size, pipe classes, and distances occupied by the 

different sizes are obtained. Pipe bursts are one major indicator of under specification in pipe 

classes and none were experienced in mainlines. Recurrent pipe burst were observed only 

on T-off takes to sub mains. This could be caused by either water hammer or airlocks in the 

system. 

Additional air valves must be installed and the mainline pipe sizes, lengths, classes and 

orientation be confirmed. This will cost just under E10 000.00 

Infield Sprinkler Irrigation 

All laterals are equipped with mechanical control valves instead of hydraulic valves. Sprinkler 

pressure measurements revealed an average operating pressure above the recommended 

sprinkler operating pressure. Pressure and flow variation is, however, above the 

recommended values at 86.9% and 55.18% respectively. This is caused, amongst others, by 

the wide variation in sprinkler packages and nozzle sizes. This variation means that even on 

highly efficient pumping, conveyance and distribution system irrigation efficiency will not 

improve, at least not until uniformity in this regard is obtained. The different sprinkler 

packages have an effect mainly on the wetting diameter due to the different body trajectory 

angles and the nozzle sizes have an effect on flow rate. 

Apart from this, Mavela irrigation scheme is characterised by no sprinkler pressure regulators, 

less than 2.57sprinklers/ha are operated simultaneously, nozzle wear of up to 2.2%, old and 

leaking equipment, etc. An immediate solution to these problems will cost E85 000.00 only. 

Management: 

The lack of design or installation information consigns a huge constraint on management. 

Forward planning on aspects related to the irrigation infrastructure cannot be done, i.e. 

replacement stock purchase; item like pipes, fittings, etc are procured after breakages 

because the details of that particular pipe, fitting, etc is obtained from the broken part. 


Irrigation scheduling is not practised and a proper irrigation scheduling tool will have to be 

introduced to the industry, especially for small holder farmers association. Various scheduling 

tools are widely used in the industry and these include tensiomentry, neutron probes etc. 

Performance of this irrigation scheme is affected, to some extend, by a lack or late application 

for fertilisers, herbicides, etc, high interest rates, high electricity cost, and the ever increasing 

production cost. 

Apart from these problems, operation, management and maintenance of this scheme is 

complicated by the lack of an operation and maintenance manual, insufficient pressure on 

some blocks, old and worn-out equipment, and frequent breakages of pumps, laterals and 

draglines. 


10 L I T E R A T U R E R E F E R E N C E S 

1. ARC- Institute for Agricultural Engineering,1998. In-field Evaluations of the 

Performance of two Types of Irrigation Emitters executed on behalf of the water 

Research Commission. Water Research Commission, Republic of South Africa. 

2. ASAE Standards. 1997. Field evaluation of micro-irrigation systems, ASAE EP458. 

3. ASAE Standards. 1998. Design and installation of micro-irrigation systems, ASAE EP 

405.1 

4. Burt, C.M. & Styles S.W. 1994. Drip and micro-irrigation for Trees, Vines, and Row 

Crops. Irrigation Training and Research Centre (ITRC). USA. 

5. Keller, J, and Bliesner, RD. 1990. Set Sprinkler Uniformity and Efficiency Sprinkle and 

Trickle Irrigation. Chapman and Hall, New York. 

6. Koegelenberg, F. H. & others. 1996. Irrigation Design Manual. Agricultural Research 

Council - Institute for Agricultural Engineering. RSA. 

7. Koegelenberg, F. H. 2002. Norms for the design of irrigation systems. Agricultural 

Research Council - Institute for Agricultural Engineering. RSA. 

8. Reinders, F.B. 1986. Evaluation of irrigation systems. Directorate of Agricultural 

Engineering and Water provision. RSA. 

9. Reinders, F.B. 1996. Irrigation Systems: Evaluation and Maintenance. SA Irrigation, 

Vol. 5-7. 

10. Scott, K. 1997. Designing with Sprinklers. Unpublished literature. ARC- institute For 

Agricultural Engineering. Silverton, Republic of South Africa. 

11. Scott, K. 1998. The effects of wind in sprinkler irrigation. ARC- Institute for Agricultural 

Engineering. Republic of South Africa. 


12. Solomon K.H. 1988a, Irrigation Systems and Water Application Efficiencies. Centre 

for Irrigation Technology, California State University, Fresno, California. 

13. Solomon K.H. 1988b.A new way to view Sprinkler pattern, Center for irrigation 

Technology, California State University, Fresno, California. 

14. Solomon, K.H. 1990. Sprinkler Irrigation Uniformity, center for irrigation Technology, 

California State University, Fresno,California. 

15. Solomon, KH Zoldoske, DF and Oliphant, JC. 1996. Laser Optical Measurement of 

Sprinkler Droplet Sizes. Center for irrigation Technology, California State University, 

Fresno, California. 

16. SSA.2001. Sugar Production Manual. Swaziland Sugar Association. Mbabane 

17. SSA.2008. www.ssa.co.sz 

18. Zoldoske, D.F. and Solomon, K.H. 1988. Coefficient of Uniformity- What it tells us. 

Center for irrigation Technology, California State University, Fresno, California. 


11 P R O D U C T I N F O R M A T I O N 

River pumps technical details; 

Sprinkler equipment 




Block hydrant valve specifications from the manufacture 

Soils classification according to SSA 




12 A P P E N D I C E S 

Attached are the following documents 

Appendix 1: SEB usage for pumps 

Appendix 2: capital recovery factors (CRF) 

Appendix 3: soil map and block layout 


CAPITAL RECOVERY FACTORS (CRF) 

Interest Rates 

Years 

% 2 3 4 5 6 7 8 9 10 15 20 

5 0.538 0.367 0.282 0.231 0.197 0.173 0.155 0.141 0.130 0.096 0.080 

6 0.545 0.374 0.289 0.237 0.203 0.179 0.161 0.147 0.136 0.103 0.087 

7 0.553 0.381 0.295 0.244 0.210 0.186 0.167 0.153 0.142 0.110 0.094 

8 0.561 0.388 0.302 0.250 0.216 0.192 0.174 0.160 0.149 0.117 0.102 

9 0.568 0.395 0.309 0.257 0.223 0.199 0.181 0.167 0.156 0.124 0.110 

10 0.576 0.402 0.315 0.264 0.230 0.205 0.187 0.174 0.163 0.131 0.117 

11 0.584 0.409 0.322 0.271 0.236 0.212 0.194 0.181 0.170 0.139 0.126 

12 0.592 0.416 0.329 0.277 0.243 0.219 0.201 0.188 0.177 0.147 0.134 

13 0.599 0.424 0.336 0.284 0.250 0.226 0.208 0.195 0.184 0.155 0.142 

14 0.607 0.431 0.343 0.291 0.257 0.233 0.216 0.202 0.192 0.163 0.151 

15 0.615 0.438 0.350 0.298 0.264 0.240 0.223 0.210 0.199 0.171 0.160

Service Contract No 2007 / 147-446 Mavela Farmers ... - Swaziland

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