Low head drip irrigation kits and treadle pumps for smallholder
farmers in Zimbabwe: a technical evaluation based on laboratory tests
Jeskia Chigerwe,a Norbert Manjengwa,b Pieter van der Zaag,c ** W. Zhakata d
and Johan Rockström e
a
Irrigation Department, Ministry of Rural Resources and Water Development, Harare; e-mail:
jchigerwe@yahoo.co.uk
b
c
Dore and Pitt (Pvt) Ltd., Harare; e-mail: norbertm@dorepitt.co.zw
UNESCO-IHE Institute for Water Education, Po Box 3015, Delft, The Netherlands; e-mail:
p.vanderzaag@unesco-ihe.org
d
Zimbabwe Irrigation Technology Centre, Zimbabwe Institute of Agricultural Engineering, Harare
e
WaterNet, PO Box MP 600, Harare, Zimbabwe, email: rockstrom@eng.uz.ac.zw
Abstract
Most smallholder farmers in Southern Africa rely on rainfed agriculture and frequently face
dry spells and droughts that affect agricultural productivity. Low head – low cost drip
irrigation may be a viable alternative for smallholder farmers, who often lack sufficient water
and energy resources to enable irrigation with more conventional irrigation technologies, as
these require more water (lower efficiencies) and/or more energy inputs (e.g. sprinkler
irrigation).
* Corresponding author
Email address: p.vanderzaag@unesco-ihe.org (P. van der Zaag)
1
This paper reports results from laboratory tests of four treadle pumps and eight drip kits
currently available in Zimbabwe. The results show that it is viable to irrigate drip irrigation
gardens up to a size of 1,000 m2, if the treadle pump and drip kit are well chosen. Such a
garden will not only ensure food security of the farmers, but may also generate significant
income.
It is concluded that farmers can opt to invest in two distinctly different types of low-head drip
systems; (i) systems with in-line emitters generating low emitter flow rates (< 0.3 l/hr at low
heads) and (ii) systems with micro-tubes generating high emitter flow rates (in this test
generally exceeding 1 l/hr). Well designed micro-tube systems with high flow rates such as
the Forster system generate high uniformity, even at extremely low head (0.1 m), and present
lower clogging problems and higher placement flexibility than the low flowing systems. Even
though this may indicate that micro-tube systems are more appropriate for smallholder
farmers, this study did not assess impacts on crop growth of different emitter rates and the
relationship between emitter discharge and non-productive soil evaporation.
Keywords: drip irrigation, distribution uniformity, efficiency, food security, treadle pump
1. Introduction
Most smallholder farmers in Southern Africa rely on rainfed agriculture and frequently face
dry spells and droughts that affect agricultural productivity. Low head - low cost drip
irrigation technologies are being introduced to bridge dry spells, mitigate against droughts and
ensure food security. Drip irrigation can be defined as a precise, slow application of water in
2
the form of discrete drops, tiny streams or miniature sprays through pressure reducing water
paths and emitters (Ngigi et al., 2000). In low head drip irrigation kits, water flows into driplines from a 100 to 500-litre drum placed at a height above the ground to provide the required
water pressure (Sijali, 2001). Water from the drum is then directed into 10-30 m long driplines with emitters placed at regular intervals to irrigate plants spaced along the line. The area
irrigated by these systems ranges from 10 to 1,000 m2.
Low head-low cost drip irrigation kits can be used in conjunction with treadle pumps. A
treadle pump is a manually operated twin cylinder reciprocating pump that uses leg muscle
force exerted on treadles to push water through the piston out via a discharge spout.
Compared to other manual lift devices, treadle pumps use human power relatively efficiently.
Low cost drip kits combined with treadle pumps have the potential to increase crop yields of
smallholder farmers (Kay & Brabben, 2000).
Although the drip kits and treadle pumps are increasingly being distributed in Zimbabwe,
their performance has not been evaluated (see Senzanje, 1997; 1998). Performance evaluation
is important not only for design engineers but also for farmers. Evaluations form the basis for
comparing commercial products (Bralts et al., 1985) and protect the user from false claims by
manufacturers (Egan, 1997).
This paper reports of tests of four treadle pumps and eight drip kits currently available in
Zimbabwe. The tests were undertaken at the Zimbabwe Irrigation Technology Centre (pumps)
and at the Department of Civil Engineering of the University of Zimbabwe (drip kits), with
support from the Organization for Linkages for the Economic Advancement of the
Disadvantaged (LEAD), an NGO distributing drip kits in Zimbabwe, and the International
3
Development Enterprises (IDE), which has developed drip technologies (see IDE, 1998;
Polak et al., 1997).
The paper first reports on the treadle pump tests, after which the performance of the drip kits
is reviewed. The subsequent section proposes an ideal combination of treadle pump and drip
kit, and indicates how such a system could be operated by smallholder farmers.
2. Performance of four treadle pumps
2.1 Methodology
Manjengwa (2003) tested under laboratory conditions four treadle pumps that are widely used
in Zimbabwe. These were the Money Saver pump, the ITDG pump, the Masvingo pump and
the Super Money Maker (Super MM) pump. Some typical characteristics of the pumps are
presented in Table 1. Figure 1 explains some of the terms used.
The technical evaluation of the treadle pumps was based on a combination of methods used
by Kedge (2001), Lambert & Faulkner (1991) and Thomas (1993). Four persons operated the
four pumps (Table 2). The flow rate of the pumps was measured at five different suction lifts
(0.5m, 1m, 2m, 3m and 4m) and at four different delivery heads (0.5m, 1m, 2m and 3m). A
submersible pump in the sump was used to change the suction levels. During each test the
suction level was kept constant by allowing a flow-back of pumped and measured water from
the drum back into the sump. The following parameters were computed: cadence, discharge
4
rate, total dynamic head, pump input power, pump output power, mechanical advantage and
efficiency.
2.2 Results
Table 3 shows results of treadle pump testing in the laboratory as averages of a number of
replicated records. The different treadle pumps manufactured in Zimbabwe range in their
average discharge rates from 1.4 to 4.2 m3/hr at average total dynamic head of 5.3 m. Table 4
gives the ranking by the four pump operators in terms of ease of pumping. Curves of the
discharge rate versus the total dynamic head (Figure 2) show that pump discharge is inversely
related with total dynamic head, following a logarithmic relationship (Table 5).
2.3 Comparison of test results
In order to identify the best pump, the pumps were compared using four criteria: maximum
power output, the output discharge at the maximum power point, the price, and the discharge
at suction lift of 3 m and delivery head of 2 m (a common condition) (Table 6).
The table shows that the Money Saver pump performs best on three out of four criteria, while
it scores the same as the other pumps for one criteria (namely price). The Money Saver pump
also exhibited the best average discharge, cadence, and mechanical advantage and power
output characteristics (Table 3), and was ranked best by operators in terms of ease of pumping
(Table 4). Finally, the Money Saver exemplifies a relatively high and flat head-discharge
curve (Figure 2), which means that it performs well even at high suction and delivery heads.
5
Despite its higher energy input requirement, the current assessment suggests that the Money
Saver pump would be most suitable to the average farmer. Its performance may be explained
by the relatively long treadle length, high ratio of leverage (the distance from the treadle to the
pivot point over that of the piston to the pivot point), and relatively high cylinder volume.
3. Performance of eight drip kits
3.1 Methodology
Chigerwe (2003) tested in the laboratory eight drip irrigation kits (Tables 7 and 8). The
objective was to assess their technical performance at the lowest possible water pressure. This
was considered important because the lower the water pressure required, the lower the energy
input for lifting the water from source into the drum. Apart from water, energy is another
scarce resource for many smallholder farmers. The performance indicators that were
measured were (a) emitter flow rate, (b) distribution uniformity and (c) sensitivity to clogging.
Average emitter flow rate
Low flows allow conditions of steady infiltration to be achieved for a relatively long time
(Bresler, 1978). An acceptable range of 0.2 –3.0 l/hr was calculated based on average soil
types. The lower value was determined using the Zimbabwean maximum evapotranspiration
of 8 mm/day (Savva et al., 1991) applied on an average drip wetted area of 0.5 m2 over 21
hours. The higher value was determined using the same wetted area and the average
infiltration rate of 6 mm/hr for average Zimbabwean soils (Savva et al., 1991).
6
Distribution uniformity (DU)
According to Bralts et al. (1981; 1985), the uniformity of water application is the most
important evaluation parameter in assessing drip irrigation systems. If the root zone can be
irrigated fully by the low quarter emitter discharge, potential application efficiency Ep of a
drip system can be equated with the distribution uniformity (Bucks & Nakayama, 1986). The
distribution uniformity DU is then defined by the following equation (ASAE, 1998):
Ep  DU  100 *
Low quarter mean emitter discharge
Average emitter discharge
(1)
Systems that have DU values exceeding 90 % are considered excellent and acceptable to
farmers (Bralts et al., 1985).
Clogging and de-clogging
Clogging of drip-lines results in a significant decrease in both the average emitter discharge
and the distribution uniformity, such that these fall below the acceptable ranges identified
earlier (Marcu et al., 1992). An indicator for de-clogging is the recovery, after flushing with
clean water, of average emitter discharge and distribution uniformity to acceptable values.
Laboratory set-up
The laboratory layout was similar to field conditions in which a 100-litre tank on an
adjustable stand was connected to one drip-line attached to supports and running horizontally
along its length. A wooden adjustable stand was fabricated for varying the minimum
operating head of 0.1, 0.3, 0.5m, 1.0m, 1.5m, 2.0m, 2.5m and 3.0m. The drip-line was
attached to horizontal support structures (Figure 3). To collect the discharge from the emitters
catch cans were arranged along the drip-line adjacent to each emitter. Data collection
7
involved recording the time interval between the first drop and the last drop of water
discharged from the emitters and then recording the volume of water discharged by each can.
With these data average emitter discharge (Qavg) and distribution uniformity (DU) of the
various drip systems were computed.
Clogging test
The two kits that showed the highest distribution uniformity were selected and tested for their
sensitivity to clogging and ease of de-clogging. The minimum possible head for each system
was used for the clog test as suggested by Decroix and Malaval (1985) because the lower the
discharge (minimum operating head) the higher the risk of clogging. A sediment mixture was
prepared for mixing with clean water. A fresh soil sample was picked at random from a red
clay soil field; the soil was sieved through 150, 125, 75 and 53 micron sieves (Table 9). The
total sediment of 25 grams was then thoroughly mixed with 100 litre of clean water. Test runs
were done as described earlier. Runs were repeated for six times and flushing with clean
water was done during the seventh run, in line with the current farming practice in the small
scale irrigation sector where irrigation is normally done for six days with the seventh day left
being for rest and repairs (Manzungu, 1999). The flushing water was allowed to pass through
the drip-line with the end open, until the discharging water was clear. The 100-litre container
was then re-filled with clean water, and the discharge through each emitter measured as
previously explained. Subsequently, six new runs with water mixed with soil particles were
carried out. The procedure was repeated until the system performed outside the set criteria
ranges.
8
3.2 Results
Quality
The imported kits (Netafim, Plastro, IDE and EIN-TAL) proved superior in quality and
workmanship on all the components. These kits are however more expensive than the local
kits with the exception of the IDE kit. The quality of the locally produced kits is not so good
with most showing poor workmanship resulting in leakages.
Emitter flow rate
All tested kits were first subjected to test runs with pressure heads of 0.5m to 3.0m with 0.5m
intervals. The average flow regime ranged from 0.2 to 1.0 l/hr for imported drip kits (except
IDE), which have so-called pressure compensating emitters, i.e. inline emitters with small
spiral passageways to cause turbulent flow. The other kits, which are mainly locally
manufactured, showed very high flow rates of up to 6.4 l/hr including the IDE kit (Figure 4a).
These kits have micro tubes as emitters, which allow relatively large water flows to pass
through.
Distribution uniformity
Over the range of pressure heads from 0.5m to 3.0m, the imported kits (except IDE) proved to
be superior in terms of distribution uniformity (> 90%). The other kits obtained low
uniformity (69 – 89 %), except the Forster kit (Figure 4b). This difference can be attributed to
the type of emitter used: systems equipped with microtubes (all locally manufactured kits, as
well as IDE) tend to perform inferior to the inline emitters used in the imported kits. The great
exception to this rule is the Forster kit. Despite it having microtubes similar to the other
locally manufactured kits, it achieved an excellent and stable uniformity (averaging 91 %).
9
This may be explained by the excellent connections between drip-line and the microtubes,
probably due to high-precision drilling of holes in the drip-line. All other systems equipped
with microtubes suffered from leaking connections, which directly affected the uniformity of
emitter discharge.
Performance at very low heads
The best kits that were equipped with microtubes, and hence had relatively high flow rates,
were further tested at very low operating heads of 0.3 m and 0.1 m to see if the uniformity
would remain stable at a lower flow rate. Although the flow rate was acceptable, only the
Forster kit maintained a stable uniformity (Figure 4).
Clogging
The kits that performed best in terms of emitter flow and distribution uniformity, namely the
Plastro (Ronfleur) and Forster kits, were tested for clogging. Figure 5 shows that the Plastro
kit performed poorly, as the emitter flow rate and distribution uniformity decreased to
unacceptable levels after only 10 runs (flows as low as 0.08 l/hr, DU dropping to 79%). The
Forster kit, on the other hand, maintained acceptable emitter flow rates and distribution
uniformity (at 1.0 l/hr and 90 % respectively). The Plastro kit proved quite sensitive to
clogging because of its small pressure compensation emitters which restrict flow conditions
encouraging blocking by suspended solids. The Forster kit has micro tubes with a diameter
wide enough to allow suspended solids to pass.
10
3.3 Comparison of test results
Low head drip irrigation technologies in Zimbabwe can be classified into two categories. The
first category consists of kits with very low flow rates, which apply water over relatively long
period of time. These kits, mainly imported from Israel, generally have stable and excellent
uniformities, at relatively low emitter flow rates. These systems do not achieve acceptable
distribution uniformities at operating heads less than 1.0 m.
The second category consists of high flow rate kits, which mainly use locally manufactured
materials except the IDE kit, which is imported from the USA. The kits have emitter flows in
the range of 1.1 to 6.4 l/hr. The distribution uniformities are less than 90 % for the tested
heads, with the exception of the Forster kit, which achieved excellent and stable uniformities
even at operating heads as low as 0.1 m. This particular kit also behaved remarkably well in
the clogging test. The Forster kit is very tolerant to dirty water and responds well to flushing.
4. Up-scaling of drip kits
The tested drip kits can irrigate gardens with an area in the order of 50-100 m2 (crop rows of
between 50-100 m and 0.8-1.2 m width). The harvestable yield may be insufficient to merit
investment in a drip kit cum treadle pump. Moreover, the irrigation requirements of such a
garden may be met simply by irrigating by hand with ordinary watering cans (the irrigation
requirement of a 100 m2 garden being in the order of 300 to 600 litres per day).
This situation changes when an intensively cultivated garden of 1,000 m2 is considered from
which three consecutive crops may be harvested annually. If, for instance cabbage, maize and
11
tomatoes are grown, yields may be as high as 4, 1 and 4 tons respectively. Such a garden
clearly has commercial potential; its production value meriting investment in drip irrigation.
Figure 6 shows a lay-out of a 1,000 m2 garden equipped with a treadle pump and a drip
system with 10 m drip-lines at 2 m spacing. Box 1 provides quantified design parameters
which indicate that such a garden would be technically feasible if equipped with the treadle
pump and the drip-line that came tops from the above tests (Money Saver treadle pump and
Forster drip kit, respectively).
12
Box 1: Design parameters of a 1,000 m3 drip-irrigated garden
Irrigation requirement: maximum 5 mm/day; off-peak: 2.5 mm/day
Drip irrigation (Forster kit): Q emitter (at 0.3 m water pressure): 1.5 l/hr
Q drip-line (64 emitters; 95% efficiency): 101 l/hr
Q main system (50 drip-lines; 95% efficiency): 5,300 l/hr or 1.5 l/s
Net irrigation application of 2.5 mm: 0.52 hour or 32 minutes (2.5 mm / ((1.5 l/hr * 64 * 50)
/1,000)))
Capacity tank: such that off-peak requirement (2.5 mm per day net irrigation) can be applied; i.e. 2.8
m3
Irrigation turns: during off-peak season: every day with 1 full tank, i.e. 0.5 hr irrigation
during peak period: every day with two full tanks ; 1 hr irrigation per day (e.g. 0.5 hr in the
morning and 0.5 hr in the afternoon).
Capacity pump (Money Saver at 3m suction head and 2m delivery head): 4.1 m3/hr
Pumping time to fill tank (2.8 m3): 0.70 hr or 42 minutes pumping
therefore: during off-peak season: 40 minutes pumping per day
during peak period: two times 40 minutes pumping per day
Dimension of the storage tank:
Consider a brick or ferro-cement tank, the floor 0.20 m above ground level; internal radius of 1.6 m
(internal diameter 3.2 m), the wall 0.75 m above ground, with a tap at 0.10 m above tank floor. The
effective storage depth above the tap is 0.35 meter, with a 0.10 m safety allowance.
Location of the storage tank:
Where the storage tank is placed depends on (a) the location of the water source, and (b) the natural
slope of the irrigation garden. It is advisable to place the tank at the highest position of the garden,
13
so that any friction losses in the main line are off-set by topography. If possible, the tank should be
at the centre of the garden, which will reduce the diameter of the main line (capacity of the line will
halve to 0.75 l/s).
Dimension main line:
In order to minimise friction losses and stabilise water pressure the main line should have a
sufficiently large diameter. If 10% of operation pressure is accepted as friction loss, then friction
loss may not exceed 0.03 m (10% of 0.30 m).
If the garden has a level slope, the internal diameter of the main line should be 90 mm at maximum
discharge of 5.3 m3/hr or 1.5 l/s. Halfway the irrigation garden discharge will be half (0.75 l/s) and
the diameter may reduce to 70 mm.
If the garden has a gentle slope, and the storage stank is placed at the highest point, then a much
smaller main line may be chosen. For example, if the garden has a slope of 1 meter over its 50 m
length, a pipe with an internal diameter of 46 mm would suffice at 1.5 l/s (and 36 mm at 0.75 l/s),
while at a slope of 3 m over 50 m, a 37 mm pipe would suffice at 1.5 l/s (and 30 mm at 0.75 l/s).
Steeper slopes are not recommended for a drip irrigation garden. The slope of the garden should
therefore be used as a resource in the design. It saves money.
5. Conclusion
Low head – low cost drip irrigation may be a viable alternative for smallholder farmers, who
often lack sufficient water and energy resources to enable irrigation with more conventional
irrigation technologies, as these require more water (lower efficiencies) and/or more energy
inputs (e.g. sprinkler irrigation).
14
This paper reported results from laboratory tests of treadle pumps and drip kits. The results
show that it is viable to irrigate drip irrigation gardens up to a size of 1,000 m2, if the treadle
pump and drip kit are well-chosen. Such a garden will not only ensure food security of the
farmers, but may also generate significant income, provided, of course, that markets exist that
are not too distant.
As shown in this study, farmers can opt to invest in two distinctly different types of low-head
drip systems; (i) systems with in-line emitters generating low emitter flow rates (< 0.3 l/hr at
low heads) and (ii) systems with micro-tubes generating high emitter flow rates (in this test
generally exceeding 1 l/hr). Well designed micro-tube systems with high flow rates such as
the Forster system generate high uniformity, even at extremely low head (0.1 m), and present
lower clogging problems and higher placement flexibility than the low flowing systems. Even
though this may indicate that micro-tube systems are more appropriate for smallholder
farmers, it is important to note that this study did not assess impacts on crop growth of
different emitter rates, nor the relationship between emitter discharge and non-productive soil
evaporation.
Testing under laboratory conditions has limitations, since the conditions under which the
equipment will be operated in the farmers fields differ significantly from those under lab
conditions. One clear point is the issue of slope: the drip-lines have been tested at level slope,
whereas in the field they will more often than not operate at a certain slope, which will effect
distribution uniformity.
15
Another limitation of the tests reported in this paper is that, due to time limitations, the
equipment was not evaluated with respect to the wear and tear. Given the many accounts of
broken down treadle pumps, this is indeed a severe limitation.
We therefore hope that research under field conditions will complement the findings
presented in this paper; see for instance the work by Moyo (2003) and Nkala (2003).
References
ASAE, 1998. ASAE standards. American Society of Agricultural Engineers, USA.
Bralts, V.F., Wu, I.P., Gitlin, H.M., 1981. Manufacturing variation and drip irrigation
uniformity. Trans. ASAE 24 (6); 113-119.
Bralts, V.F., Edwards, D. M., Kesner, C.D., 1985. Field evaluation of drip/trickle irrigation
submain units. In: Drip/Trickle Irrigation in Action: Proceedings of the Third
International Drip/Trickle Irrigation Congress. November 18-21 Center Plaza Holiday
Inn Fresno, California USA pp 274-280.
Bresler, E.,, 1978. Analysis of Trickle Irrigation with Application to Design Problems.
Irrigation Science 1(1): 3-17.
Bucks, A.D., Nakayama, F.S., 1986. Trickle Irrigation for Crop Production. Elsevier.
Amsterdam.
Chigerwe, J., 2003. Technical evaluation of low head – low cost drip irrigation kits for
smallholder farmers in Zimbabwe. Unpublished MSc WREM dissertation. University of
Zimbabwe, Harare.
16
Chigerwe. J, Fox, P., Rockström, J., Van der Zaag, P., 2003. Rapid laboratory performance
test of low pressure small-scale drip irrigation systems. Unpublished report. WaterNet &
Dept. of Civil Engineering, University of Zimbabwe, Harare.
Decroix, M., Malaval, A., 1985. Laboratory evaluation of trickle irrigation equipment for field
system design. In: Drip/Trickle Irrigation In Action. Proceedings of the third
International Drip/Trickle Irrigation Congress. November 18 - 21, 1985 Centre Plaza
Holiday Inn Fresno, California USA. ASAE Publication Vol. 1 pp 325 - 330. American
Society of Agricultural Engineers, Michigan.
Egan, L.A., 1997. The mass marketing of affordable irrigation devices. In: Irrigation
Technology Transfer in Support of Food Security. Proceedings of the subregional
workshop. Harare, 14-17 April.
IDE, 1998. Affordable Micro Irrigation Systems (AMIS): Providing appropriate solutions to
small farmers. International development Enterprises. New Delhi, India.
Kay, M.G., Brabben, T., 2000. Treadle pumps for irrigation in Africa. Knowledge Synthesis
Report No. 1. IPTRID, Food and Agriculture Organisation, Rome.
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– Scale Farmers. Unpublished MSc Thesis. School of Bioresources Engineering and
Environmental Hydrology, University of Natal, Pietermaritzburg.
Lambert, R.A., Faulkner, R.D., 1991. The efficient use of human energy for micro-scale
irrigation. Journal of Agricultural Engineering Research 48: 171-183.
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Unpublished MSc WREM dissertation. University of Zimbabwe, Harare
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In: E. Manzungu, A. Senzanje and P. van der Zaag (eds.):Water for Agriculture in
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Zimbabwe: Policy and Management Options for the Smallholder Sector. University of
Zimbabwe Publications, Harare. 92-119.
Marcu A., Paz, E., Ravina, I., Sagi, G., Shisha, A., Sofer, Z., 1992. Control of emitter
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province in terms of water use, technical suitability, and social and economic aspects.
Unpublished MSc WREM dissertation. University of Zimbabwe, Harare.
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the smallholder irrigation sub-sector in Zimbabwe. Unpublished MSc WREM
dissertation. University of Zimbabwe, Harare.
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Volume 1. Agritex/FAO/UNDP, Harare.
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Engineering: Engineering Challenges in Agriculture in Developing Countries in the 21st
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19
Tables
Table 1
Dimensions of the four treadle pumps tested
Dimension (mm)
Height above ground
Handle height
Treadle to pivot
Piston to pivot
Stroke
Cylinder diameter
Pulley diameter
Money Saver
120
1080
750
335
135
112
150
ITDG
120
900
720
330
120
107
145
Masvingo
124
1090
1260
1180
200
100
153
Super MM
25
970
680
190
95
115
185
Age (years)
23
25
26
22
Height (m)
1.57
1.52
1.67
1.83
Table 2
Pump operators by gender, weight, age and height
Name of operator
Ms. Tsitsi
Ms. Muchaneta
Mr. Batanai
Mr. Amos
Gender
Female
Female
Male
Male
Weight (kg)
48
62
55
74
Table 3:
Average results of comparative treadle pump testing
Pump
Lift
Head
Money Saver
Masvingo
ITDG
Super MM
m
2.1
2.1
2.1
2.1
m
2.6
2.6
2.6
2.6
Cadence Discharge
stroke/min
69.8
40.8
62.9
46.6
m3/hr
4.2
3.0
3.4
1.4
Total
dynamic
head
m
5.4
5.3
5.3
5.4
20
Power
input
Watt
166.8
77.2
129.7
119.1
Power Mechanical Efficiency
output advantage
Watt
48.2
29.6
37.7
15.8
2.9
2.1
2.4
1.0
%
31.9
45.3
31.0
14.1
Table 4
Treadle pumps ranked and scored in order of ease of pumping as perceived by operators. Scores between 1 to 4
were assigned to each pump, where 1 = lowest ease and 4 = highest ease of pumping
Pump
Money Saver
ITDG
Super MM
Masvingo
n
4
4
4
4
Average score
4
2.25
2.25
1.5
Range
4–4
1–3
2–3
1–3
Table 5
Regression equations of head H (m) and discharge Q (m3/hr) for the treadle pumps
Pump
Money Saver
ITDG
Masvingo
Super MM
Regression Equation
Q = -2.01 Ln(H) + 7.40
Q = -1.96 Ln(H) + 6.47
Q = -3.60 Ln(H) + 8.74
Q = -0.59 Ln(H) + 2.32
Table 6
Scorecard for the four pumps
Criterion
unit
Maximum power output
Watt
Money
Saver
60
Discharge at maximum power output
m3/hr
4.4
ITDG
Masvingo
45
35
Super
MM
20
3.2
2.5
1.3
a
Price
US$
187.50
187.50
187.50
187.50
Discharge at suction lift = 3 m and
m3/hr
4.1
3.1
2.5
1.3
delivery head = 2m
a
These prices were quoted in May 2003 and were, surprisingly, identical; they have since changed.
Table 7
Characteristics of the eight drip kits tested
Country of
Emitter type
manufacture
IDE
USA
microtubes ø 1.2 mm L=0.6m
Forster
Zimbabwe
microtubes ø 1.5 mm L=1.0m
Automated (small diameter)
Zimbabwe
microtubes ø 1.5 mm L=1.0m
Automated (large diameter)
Zimbabwe
microtubes ø 1.5 mm L=1.0m
Netafim
Israel
in-line emitters
Plastro (Water Wise)
Israel
in-line emitters
Plastro (Ronfleur)
Israel
in-line emitters
EIN-TAL
Israel
in-line emitters
a
Exchange rate used: 1 US Dollar = 824 Zimbabwe dollars.
Drip kit
21
Unit cost
Z$
US$ a
31,500
38.22
32,400
39.32
37,978
46.09
37,978
46.09
42,380
51.43
42,885
52.04
48,900
59.34
48,900
59.34
Table 8
Drip-lines and emitters supplied per drip kit
Drip kit
No. of driplines per kit
IDE
Forster
Automated (small diameter)
Automated (large diameter)
Netafim
Plastro (Water Wise)
Plastro (Ronfleur)
EIN-TAL
5
5
5
5
5
6
6
14
Length of
each dripline (m)
10
10
10
10
10
10
10
5
Table 9
Sediment mixture for clogging tests
particle size (10-6 m) concentration (grams per 100 litre)
0-53
6.25
53-75
6.25
75-125
6.25
125-150
6.25
sum
25.00 grams per 100 litre or 250 ppm
22
No. of
emitters per
drip-line
64
64
64
64
32
72
50
15
Total length of
crop rows irrigated
per kit (m)
100
100
100
100
50
60
60
70
Figures and figure labels
Fig 1. Basic components of a treadle pump
23
8
7
6
Discharge 5
(m3/hr)
4
3
Money Saver
2
ITDG
1
Super MM
Masvingo
0
0
2
4
6
Total Dynamic Head (m)
Fig 2. Pump curves for different pumps
24
8
10
water tank
catch cans
drip line
Fig 3. Laboratory set-up of the drip kit tests
25
Average emitter flow rates
4.5
Emitter flow rate (L/hr)
4
3.5
3
2.5
2
1.5
1
0.5
0
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
3
2.8
3
Minimum operating head (m)
Automatic large dia.
Netafim
Automatic small dia.
EIN-TAL
Forster
Plastro (Ronfluer)
IDE
Plastro (Water Wise)
Max. recommended flow
Min. recommended flow
Emitter distribution Uniformity (DU)
100
95
90
DU (%)
85
80
75
70
DU Auto.large
DU Auto. small dia.
DU forster
DU IDE
Recommended DU cut off(%)
65
60
55
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
DU Netafim
DU EIN-TAL
DU Plastro (Ron.)
DU Plastro (W.W.)
2
2.2
2.4
2.6
Minimum operating head (m)
Fig 4. Relationships between minimum operating head and (a) emitter flow (top) and (b) distribution uniformity
DU (bottom) of the 8 drip kits tested
26
CloggingAverage emitter discharge (L/hr) (Forster &Plastro)
1.2
Averageemmiter discharge(L/hr)
1
0.8
0.6
0.4
0.2
0
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Forster Irrigation(Minimumhead 0.1m)
Number of runs
Minimumacceptable Flowrate (L/hr)
Plastro kit (Minimumoperating head 1.0 m)
Clogging Distribution uniformity(DU%) (Forster &Plastro)
100
95
DU (%)
90
85
80
75
70
65
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50
Forster Irrigation(Minimumhead 0.1m)
Number of runs
Minimumacceptable Flowrate (L/hr)
Plastro kit (Minimumoperating head 1.0 m)
Fig 5. Results of the clogging tests on two kits
27
drip line
micro-tube
2m
filter
storage
tank
1,000 m2 drip irrigation garden
10 m
main line
10 m
pump
50 m
Fig 6. Lay-out of a 1,000 m2 drip irrigation garden
28