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2.1.5 Groundwater Abstraction Using Handpump-equipped Wells
Handpumps tap groundwater from shallow or medium depth aquifers and from
deep aquifers if the at rest water level is high enough. Handpumps are
water conveyance systems used to bring groundwater to the surface. There
are a number of such pumps in operation in Africa and numerous textbooks
provide specific descriptions of these devices (Figure 31).
Model "B" bushpump
Figure 31. Some commonly used handpumps.
In normal circumstances, handpumps are installed in wide diameter wells,
which can be constructed by hand to depths of up to about 15 m, or drilled
by rigs to much greater depths. The type of well most widely used is the
hand-dug well, which is one of the cheapest means for providing a small
supply of water in rural areas. A depth of about 10 to 20 m is usually
considered the limit of practical manual sinking. The diameter of the well
should not be less than 1.2 m, allowing two persons to work together in
the well. A lining, that serves several purposes, should be used as the
well is sunk. The lining is a protection during construction against
caving and collapse, and retains the well wall after completion. There are
many materials suitable for linings; e.g., masonry, brickwork, and plain
or reinforced concrete. On the bottom of the well, it is usual to place a
filter of graded layers of gravel to prevent the ground material from
being drawn upwards into the well with the water. At the surface, the
lining of the well should be raised at least 0.6 m above ground level and
provided with a protection platform to channel drainage away form the
Small diameter wells may also be constructed by means of an auger. The
auger, which is usually about 100 mm across, may be rotated by hand.
Mechanised augers, or power augers, are also available. Once the
water-bearing layer has been penetrated, the necessary length of piping,
tipped with a screened wellpoint, or strainer, is lowered into the hole; a
pump attached to its upper end, and the well "cleared" by
pumping. Tube wells consist of a perforated or screened pipe which is
jetted or driven into the groundwater-bearing aquifer. Tube wells can
yield large quantities of water, but the depth to which they can be driven
is limited and the ground formation must be appropriate for their use.
Their most common application is in the extraction of groundwater from
water-bearing sands, especially those forming the beds of ephemeral
Tube wells can also be installed in perennial rivers, making use of the
natural filtering properties of sandy beds of the rivers by drawing water
through the river beds instead of from the rivers themselves. The pipes
are usually 25 to 100 mm in diameter. The wells constitute a good means of
obtaining water from areas with relatively coarse sand.
Extent of Use
Wells using handpumps are extensively used throughout Africa.
Operation and Maintenance
The operation and maintenance of handpumps varies depending on the type
and complexity of the pump. Attempts at designing a reliable pump which
can be maintained at the village level continue. Experimentation with
these village level operation and maintenance (VLOM) schemes are shifting
gradually to focus on institutional-level operation and maintenance.
Preventative maintenance operations carried out by villages and
institutions include greasing moving parts (taking care not to contaminate
the water supply with oils and greases), tightening bolts, replacing seals
(for some pumps), and cleaning the surroundings.
Level of Involvement
Local inputs to implementation of this technology are generally in terms
of skilled labour and materials. Technical advice may be necessary in the
conduct of hydrogeological investigations and well drilling.
While hand dug wells are quite inexpensive, boreholes drilled by rigs
are fairly expensive in terms of initial capital costs. Dug shallow wells
and augured tube wells have a per capita construction cost of $6 to $20,
with an operation and maintenance cost of $0.02 to $0.14 per capita per
year. Machine-drilled boreholes, equipped with a hand pump and serving a
population of about 200 to 300 people, will have an estimated per capita
construction cost of $19 to $23, and an operation and maintenance cost of
$0.26 to $0.52 per capita per year.
Effectiveness of the Technology
The delivery rate of most handpumps is around 20 l/min, and their ease
of operation makes them ideal for rural operations.
Dug wells are an appropriate option in areas where groundwater is less
than 20 m below ground level. Augured tube wells, dug using motorised
and/or manual rigs and augers of limited penetration, are appropriate in
areas in which groundwater occurs at depths between 20 and 35 m.
Motorised, conventional drilling rigs are an ideal means of developing
water supply sources in areas where groundwater occurs at depths greater
than 35 m below ground level, or in hard rock between 20 and 25 m depth,
where the weathered material is thin.
The existence of a well may lead to increased erosion in its immediate
vicinity. However, wells are focal points for other development such as
the planting etc.
Well water is relatively safe without treatment. Hand dug wells are
inexpensive and can be constructed using local skills and materials;
community participation is easy to organize. Further, the operation of
handpumps requires no external power and few skills, and the pumps may be
maintained by local technicians. The use of spare parts is small.
The capacity of a well is limited, and service supply levels are lower
than in piped schemes supplied from conventional sources. Hand dug wells
are reliable only in areas where good quality groundwater is available at
shallow depth. The hygienic quality of the wells, especially shallow
wells, is not always satisfactory as a result of surface water intrusions
leaking through the slab and superstructure, and around the pump casing.
There are no cultural problems in utilizing groundwater for domestic
purposes. However, communities do not like wells to be developed too close
to sacred places such as shrines.
Further Development of the Technology
There is need to improve on the methods of digging the shallow wells.
Also, the handpump needs further developmental work to make it more
suitable for village level operation and maintenance. Maintenance systems
require further development to ensure sustainability.
Further information can readily be obtained from the Departments of
Water in the various countries, and also from organisations such as
UNICEF, World Vision, CARE, and Save the Children, among others.