Groundwater augmentation for semi-arid rural areas of zimbabwe
E. Mangore* and T. Kandenga
Department of Civil and Water Engineering
National University of Science and Technology
P O Box AC 939, Ascot, Bulawayo, Zimbabwe
*Corresponding author email: enmangore@nust.ac.zw or enmangore@yahoo.com
Groundwater is the most most widely source for domestic and watering gardens in many rural
semi-arid regions of Zimbabwe. However, during the dry hot months of the year this resource
can be undependable. To argument this important resource, a simple method of recharging
the aquifers was devised so that this source could be sustainable throughout the year. As a
study case, an area measuring 500m by 300m was chosen at a homestead in rural Chivi
district of Zimbabwe. For recharging purposes two rows of pits and trenches were constructed
at some points they could have the greatest chance of intercepting runoff. Each pit was 1.5 m
by 1.5 m by1.2 m deep and lateral spacing of about 10 m. For monitoring, the extent of
recharging process, existing boreholes and wells within and outside the study area were used.
Due to financial constraint new boreholes were not drilled. The period of study extended from
one dry season to another, September 2004 to September 2006
The results obtained showed a general increase in the water table of up to 20% compared to
the baseline levels (taken as those of the September 2004) though they were to some certain
extent affected by the lower than average rainfall received during the season of 2004/2005.
Monitored wells outside the study area did not show significant increase in levels and in some
cases the wells actually dried up.
As households are frequently very poor and in view of reduced public funding because of the
economic situation currently prevailing in Zimbabwe, recharge facilities were designed to be
low cost and requiring low skill. On overall evaluation of the recharge techniques, the system
proved to be sustainable (affordable, environmentally compatible and efficient). The study
was carried out at household level thus ensuring the participation of women and children who
are usually responsible for collecting water for household use. Having a readily accessible
water supply meant that more time can be spend on other activities other than just fetching
water.
Keywords: groundwater augmentation, household, rainfall, recharge
1. Introduction
The environment and many people in semi-arid regions of Zimbabwe face a bleak future due
to the dwindling water availability. Rejuvenating these dry areas hinges on community
involvement. A typical example is the case of Madhya Pradesh, India in which community
based movement was set up to carry out water conservation activities which resulted in the
overall improvement of the water situation in an area of 50 districts and a population of about
60 million people.
Rainwater harvesting techniques have in existence for a long time, eg as shown by Evagari
(1971), but there is need to develop methods that are suited for a particular set of conditions
(appropriate technology) and community.
Keller et al., (2000) point out that there are four main ways of storing rainwater, viz, in the
soil aquifers (unsaturated zone), in aquifers, in small-medium dams and in large dams. In this
work the main thrust is on the storage of the water in shallow unconfined aquifers. These
types of aquifer in prevalent in basement complex which underlies extensive areas in
Africa.This is especially important because a number of rural communities in the semi-arid
region of Zimbabwe already depend on groundwater. Ways in which rainwater harvesting is
implemented worldwide is based generally on the cost, skill, hydrogeological/hydrological
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characteristics and geographical location. Methods include: Rainwater collection from roof
tops and courtyards; recharge weir/dam, channel/canal, basin/ponds and trench; gravity fed
vadose well; gravity fed injection well; dug well for artificial recharge (Pacey and Cullis,
1986)
This report presents results of the initial phase of the work carried out in South-eastern
Zimbabwe in Chivi district on groundwater augmentation by rainwater recharge. The
appropriateness of the recharge method was assessed by investigating the cost, level of skill
required for implementation, environmental compatibility and acceptance by rural
communities. Techniques that can be used immediately have proved to be more effective in
improving livelihood as opposed to situations where technical assistance is always required
which many times is many hundreds of kilometres away.
1.1 Background
In Zimbabwe, dam construction is the usual method of rainwater harvesting and the
government encourages that more dams be constructed in resettled areas. While this is a noble
idea, in most cases dams are not always located near the new farmers. Hence farmers are
digging their own wells in the hope of obtaining water for domestic use and to some extend
for agricultural purposes. These productive water points (wells) however cause high intensity
of groundwater use. This then raise concern that groundwater use and the livelihoods it
supports may not be sustainable since consequences of over exploitation will cause falling
water table levels and land subsidence.
In light of the above, this study sought to find ways in which other means can be incoorprated in augmentation of water supplies in an effort to assist. As most livelihoods of the
rural communities are dependent on water availability, existence of a reliable and adequate
source of water is important. For agricultural purposes, earth recharge seems to be the best
option (potential large subsurface reservoir) while collection from rooftops will be
appropriate for domestic purposes. The work is more of adaptive research and efforts were
made to narrow the gap between researchers/scientists and user of technologies. As pointed
out by Mitchell (1980) R & D institutions have not been very good in providing suitable
technical options that communities in particular the poor can adopt.
1.2 Aims and Objectives
The work endeavours to find ways of improving sustainable groundwater supplies for
recently resettled farmers by means of recharging aquifers using rainwater-harvesting
techniques.
The main objective is to maintain or augment natural groundwater, realising that it is an
economic, finite, social resource. Specific objectives are:
 conserve excess surface water underground
 compact progressive depletion of groundwater levels
 conserve or improve the ecosystem (groundwater dependent ecosystem)
1.3 Study Site
The study area is located in Ward 11, Chivi district. Chivi is the south eastern side of
Zimbabwe in the Masvingo Province. The district lies in region IV of the natural farming
regions of Zimbabwe. Rainfall is limited, poorly distributed in space and time, average annual
rainfall between 1914 and 1992 was 548 mm (Waughray and Rodriguez, 199), and of great
temporal and spatial variability. The region is classified as semi-arid according to Beekman
and Xu (2003) where aridity is defined on the basis of average annual rainfall: hyper-arid: 050 mm/yr; arid: 50-200 mm/yr and semi-arid: 200-500 mm/yr. The rainy season is from
around November to March.
The crystalline basement underlies and groundwater occurs in the upper fractured weathered
rock. Aquifers are usually shallow ( the deepest monitoring well was about 20 m) Lovell et
al. (1996) estimated, on a regional long term basis, that groundwater use in communal areas
of south-east Zimbabwe is only around 4 per cent of average annual recharge.
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2. Materials and Methods
2.1 Study Outline
The study has so far extended over a period of 11 months, stretching from one dry season to
next dry season. Activities include:
- Initial site characterisation and establishment of monitoring stations monitoring
- Construction of infiltration pits, trenches water supply mini reservoir
- Continuous water level monitoring
As expected in most areas of public consultation were done at various level of the
community. A top-down approach was adopted in which consultation were begin at the office
of the district Chief Executive Officer (to gain entrance into the district) down to the village
level. This was necessary to minimize resistance to new initiatives which can occur in cases
where consultation is not carried out adequately. Being part of consultation process thus
enabled the community to find out what is going on around them. Advantage was taken of the
existence of village and ward committees that are part of the rural communities’ set up in
Zimbabwe. Although Participatory Rural Appraisals (PRA) is particularly effective in
providing detailed qualitative information, cost and time were major constraints in
implementing them. The community was trained by means of demonstration on a pilot study
plot on the positioning and dimensions of the runoff intercepting structures and maintenance
of the same.
A study site in ward was selected with the help of staff from Agriculture Research Extension
(AREX), a government department which is responsible for the supervision of agricultural
activities in the district. As part of the project outline, it was insisted on making community
organisations the primary players and refusing limit external funding (to ensure sustainability
of the project) and not make the communitys dependent on outsiders. It was intended to the
community organisations direct the projects using local labour and materials.
2.2 Recharge structures set up
Due to financial constraints no extra boreholes could be drilled at strategic points and
therefore dug wells were used for the monitoring of the water levels. The greatest limitation
of dugwell is that they can easily dry up.
A number of infiltration pits and trenches were constructed at such points such that they could
the greatest chance of intercepting surface runoff. For a plot of roughly 100 m by 500 m, 2
rows of pits and trenches were constructed. Each pit was of 1.5 m by 1.5 m and 1.2 m deep.
The work employed a number of techniques to aid in groundwater recharge which included:
-project was community based (advantages) – participation of the community and local
institutions was ensured.
-infiltration pits and trenches constructed in catchments and recharge area of groundwater
systems.
-determining of groundwater levels (baseline) and periodically on a quarterly basis
-determination of physical properties of study areas such as geology and hydrogeology, river
systems, wetlands
A list of the monitoring wells and their locations is shown on table 1
Table 1: List of wells and their locations
Well No.
Location
Main use
W1
W1a
W1b
W1c
W2
Tagwireyi
Tagwireyi
Tagwireyi
Tagwireyi
Muganhu
Drinking
Watering garden
Watering garden
Watering garden
Drinking
3
W3
W4
W5
Chaka
Njovo
Maripa
Watering garden
Watering garden
Watering Garden
Baseline water levels were measured in October 2004. Subsequent water levels were
measured in January 2005, March 2005, June 2005 beginning and end of July 2005.
3.
Results and Discussion
3.1 Results
The water levels (depth to water table) measured in the monitoring wells are shown in Table 2
Table 2: Depth to water levels for the period October 2004 to 2006
Well
10/2004 01/2005 06/2005 Early
End
Number/Month07/2005 07/2005
year
W1
5.24
0.75
5.02
5,10
5,14
W1a
nm
0.2
nm
nm
nm
W1b
nm
0.2
nm
nm
nm
W1c
nm
0.1
nm
nm
nm
W2
3.2
0.45
2.59
2,70
nm
W3
1.54
nm
nm
nm
nm
W4a
3.4
1.18
1.48
1,50
1,53
W4b
2.8
0.85
1.32
1,72
1,75
W5
2.62
1.21
1.89
nm
nm
10/2005 03/2006
5.21
Dry
Dry
Dry
nm
nm
2.28
1.98
nm
1.78
0.51
0.46
0.00
0.00
nm
0.98
0.93
0.00 (nm –
not
measured)
The water levels for the month of October 2004 are taken as the initial conditions. W1a, W1b,
W1c are very shallow large diameter wells and were dry for most of the time. Measurements
for these wells were only recorded in January 2005. W3 had collapsed in January 2005,
probably because of the sandy area location.
The results for January show increase in water level (compare 5.24 and 0.75 for October and
January respectively for W1). This is expected after the rainfall events of December and
January. The increase in water level is usually used as an indicator of the success of a
rainwater harvesting system. Since there is no history for the water levels of the monitored
wells no comparison can be made to determine the level of success of the work. Other factors
such as quality water and quality of crops can also be used. However, it is difficult to use
quality of water as a yard stick because no baseline water quality data exists.
Percentage reduction in ground water levels in well W1 versus well 4a and 4b …..
3.2 Effect on community
Relative to the surrounding areas, there was an improvement on water security for both
domestic and agricultural purposes on the study area. This was attributed to the fact that the
cach pits managed to capture the run off water which then slowly percolated into the ground
water, resulting in lots of water being retained and consequently bringing a rise in the level of
the water table.
The water security as a result, brought with it food and income security in terms of a
relatively higher agricultural produce as compared to the previous yields, availability of water
for vegetable cultivation and for domestic and livestock purposes. This had an overall effect
of bringing a great relief to the beneficiaries as they managed to sustain themselves against
the devastating effect of the year drought ( 2005 ).
The work fostered improvement in the livelihoods of the rural poor, especially women and
children. Usually the women run market gardens which success depends to a large extent on
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the availability on water. They are responsible for the hygiene of the family. Greater
availability will also improve family hygiene. Having a readily accessible water supply will
mean that more time can be spend on other activities other than just fetching water, which is
often the case in most of the semiarid rural areas of Zimbabwe. Males generally spend 18%
less time on productive work than females. Women have less time for leisure and almost none
of their time is devoted to academic activities. Household in the neighbourhood, who
observed the marked difference between the crop quality of the plot under study and the
surrounding were eager to set up recharge facilities in their plot, with mostly women in the
forefront. A higher chance of water distributive equity resulted by virtue of the increased
groundwater level which greater chance of accessibility.
3.3 Groundwater dependent ecosystem
For the environment, the results of the study were very favourable. The catch pits proved to
be another way among others of reducing soil erosion. Up to June 2005, water retained in the
catch pits provided water to the non domestic animals including birds. The surrounding bush
and grass areas was observed to be thriving very well due to the availability of the ground
water that was raised closer to the ground surface. Erosion was observed to have decreased;
this was mainly due to the decrease in flow velocities.
Groundwater use and dependents by crops was not obvious. However comparison of the
quality of crops at the study site and nearby plots showed a great difference. The other
farmers harvesting close to nothing (2004/2005 was another dry year and only two major
storms were experienced), where as close to a bumper harvest occurred at the study siteA
monitoring system for groundwater dependent vegetation is to be designed. (Colvin et al.,
2003).
4. Conclusions and Recommendations
4.1 Conclusion
This paper examines the claim that simple groundwater recharge structures can contribute to
water availability and thereby contribute to improved rural livelihoods in semi–arid rural
areas. A number of factors determine the success of the techniques. These include the
occurrence of rainfall, physical characteristics and community acceptance. The rainy season
2004/2005 was a drought which had negative impacts on the work as some wells might for
groundwater levelling actually went dry and therefore making it difficult to draw firm
inferences.
Water harvesting technology is especially relevant to semi-arid and arid areas where the
problems of environmental degradation, high temporal variability of rainfall and droughts
pressures are most evident. It is an important component of the package of remedies for these
problem zones, and that implementation of rainwater harvesting will go a long way in
assisting the communal farmers in semi-arid regions.
4.2 Recommendations and future work
Though the results of this research were quite encouraging, 2004 to 2005 drought had a
negative impact on what was expected. Only two major rainfalls events occurred during the
period. As a result the ground water level (water table) was not raised to the expected level
and moreover the surrounding area outside but adjacent to the study area had an even lower
groundwater level prompting water to quickly move out of the study area than expected.
Because of lack of water elsewhere, the beneficiaries started using water earlier than before
especially for domestic animals. This brought about a critical issue which many ground water
aquifers face today in that the volume of water withdrawn exceeds long term recharge
resulting in declining of ground water table at a faster rate. Therefore long term monitoring is
encouraged.
5. References
Lovell et al. (1996)
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Beekman and Xu (2003)
Critchley, W. and Siegert, K., (1991), A manual for the design and construction of Water
Harvesting Schemes for Plant Production www.fao.org/docrep/u3160E/u3160E00.htm
Desert Margins Program, Zimbabwe, (2004), Baseline Report for Chivi, Matobo and
Tsholotsho Districts
FAO, (****), Water harvesting Techniques, Texas guide to Rainwater Harvesting
www.fao.org/docrep/u3160E/u3160eo7.htm
Gale, I., (2005), Augmenting Groundwater Resources by Artificial Recharge (AGRAR),
BGS, www.ian.org/recharge/projec
Houston,
Mitchell, R. J., (Ed.), (1980), Experiences in Appropriate Technology, The Canadian Hunger
Foundation, Ottawa
Ngoni N. and Moyo B., (****), Gender Mainstreaming in IWRM for poverty reduction,
Institute of water and sanitation development, Harare, Zimbabwe
Priscoli, J.D., (1991), What is Public Participation in Water Resources Management and Why
is it important?
(Waughray and Rodriguez, 199)
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