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close this bookSourcebook of Alternative Technologies for Freshwater Augmentation in Africa (UNEP-IETC, 1998, 182 p.)
close this folderPart C - Case studies
View the document4.1 Tied ridging - Domboshawa, Zimbabwe
View the document4.2 Freshwater augmentation - cloud seeding, Zimbabwe
View the document4.3 Tidal irrigation, the Gambia
View the document4.4 Spring protection - Mukono district, Uganda
View the document4.5 Water augmentation - Laikipia district, Kenya
View the document4.6 Recycled water - Achimota Brewery, Ghana
View the document4.7 Water recycling - Tarkwa gold fields, Ghana

4.1 Tied ridging - Domboshawa, Zimbabwe


Zimbabwe has experienced low and erratic rainfall for the decade prior to 1995. To offset agricultural losses related to low rainfalls and variations in rainfall related to these vagaries of nature, researchers investigated tillage methods that conserve soil moisture. The major objective in moisture conservation tillage methods is to conserve moisture in the soil in order to increase germination and yields. Runoff is greatly reduced and infiltration rates are increased. Moisture conservation tillage technologies include tied-ridging, mulching, contour ploughing and minimum tillage, described in Part B, Chapter 1, "Agriculture".

This case study looks at ridging and tied-ridging in Domboshawa, an area about 30 km north of Harare, the capital city of Zimbabwe. It is located in the Highveld of Zimbabwe at an altitude of about 1200 m above sea level. The average annual rainfall ranges from 800 mm to 1 000 mm per annum. The rainfall is seasonal with approximately 90% falling in the months of October to March.

Technical Description

Ridging and tied-ridging as carried out in Zimbabwe is widely documented (FAO, 1966). Most of the equipment used for ridging and tied-ridging was locally manufactured, and designed to be animal-drawn. A typical, ox-drawn disc ridger, developed by the Department of Agricultural and Technical Extension Services (AGRITEX) in conjunction with GTZ, is illustrated in Figure 42.

The high wing ridger body is used for making the ridges, and is an accessory to the mouldboard plough. When making ridges, the ridger body is attached to the plough instead of the mould board. The ridger produces ridges which are 250 mm high. The high wing ridger is of French design but is manufactured locally. The ridger has two adjustable discs angled to form a wide 'V' shape. Although the unit looks heavy, the draft requirement is actually less than that required for the conventional mouldboard ploughs. Depending on the ridge requirements, the disc sizes and shapes can be varied.

Ridges made using this technology can be tied using hand hoes. In Zimbabwe, simple ox-drawn tie-makers have been produced locally. As illustrated, these can be made from old mouldboard plough shares or discs fitted on to metal or wooden uprights. In order to avoid having too many operations, ties can be coupled to the ox-drawn disc ridger (Figure 43). They can also be fitted onto cultivators (Figure 44). Ties are made by scraping the tie-maker along the furrows between the ridges until enough soil has been collected. The collected soil should be about ½ to 2/3 height of the ridges.

Extent of Use

Through AGRITEX and the Department of Research and Specialist Services (DR&SS), was responsible for the research and extension of the technology. The programme started with field trials. During trials a few farmers were selected to participate. Results from the trials proved that the tied-ridging method of tillage produced better yields than the conventional methods of tillage traditionally used by farmers in this area. The fact that farmers saw the benefits of the system made it easy for the extension personnel to convince the rest of the communities to adopt the method.

Figure 42. Ox-drawn disc ridger with tie-maker attached.

Source: Makoholi Research Station

Nevertheless, there has been some measure of resistance to changes in the traditional methods of cultivation. This resistance was compounded by shortages of labour and draft power. Shortages of labour resulted from male migration to urban areas in search of employment, while the shortage of draft power resulted from reduced animal stocks due to the drought. All of these obstacles have not yet been overcome, and, although the method is acceptable to the farmers, it is not widely practised. Only 1% of the farmers in the area use the method (Elwell, 1993)

Operation and Maintenance

Ridgers and tie-makers do not require any special skills to operate or maintain. There are few components that need replacement, and, hence, the technology is very suitable for communal operations. Disc-ridgers and ridger bodies wear out with time, but replacement is not a problem since the equipment is locally manufactured.

Level of Involvement

The government, local communities and non-governmental organizations were all involved in the project. The government provided the personnel for the research and extension while GTZ provided some of the funding.

Figure 44. Light Cultivator with tie-maker mounted.

Source: Institute of Agricultural Engineering, Harare, Zimbabwe

Figure 43. Ox-drawn disc-plough tie-maker.

Source: Institute of Agricultural Engineering, Harare, Zimbabwe


The major cost is the purchase of the ridgers and the tie-makers. Where the farmers already have mouldboard ploughs or cultivators, the cost will be low because the ridger body and the tie-maker can be fitted easily. A new ox-drawn ridger costs $300 and a new mouldboard plough costs $30. If the farmers do not have their own implements, the cost of hiring the equipment to have one hectare ploughed and tie-ridged will be $250.

Effectiveness of the Technology

As shown in the following table, the results of the field trials showed that there was a reduction in runoff from fields with tied-ridges compared to those with conventional tillage.


The advantages of tied-ridges include reduced erosion and conservation of soil moisture. The equipment used is simple and easy to use, and capable of being locally manufactured and maintained. The field trials clearly showed improved crop yields.


Tied-ridgers require new or additional equipment, and substantial time and effort required to prepare the lands each year. This increases farmers' costs. In areas with highly variable rainfall, ridges can fail due to overtopping. When this occurs, greater soil losses may result.


Tillage Treatment

Rainy Seasons

Surface Runoff

Soil Loss




Conventional Tillage

















Tied Ridging

















Further Development of the Technology

The technology has great potential for use in arid and semi arid regions. However, in order for the technology to be accepted and adopted, much effort has to be put in the research and extension services. The government has to be strongly involved in the exercise. The technology is easy to adopt if the farmers are mechanized and they have enough draft power. Availability of draft power is essential because substantial time and effort is required for the land preparations. For countries wishing to adopt this technology, it is very important to make sure that an effective extension service, adequately financed, is in place.

Sources of Information


D. Dube, ARDA, Post Office Box CY 1420, Causeway, Harare, Zimbabwe.

Institute of Agricultural Engineering, Post Office Box BW 330, Borrowdale, Harare, Zimbabwe, tel. 263-4-860119 or 263-4-860055.

I. Nagambie, Conservation Specialist, Institute of Agricultural Engineering, Post Office Box BW 330, Borrowdale, Harare, Zimbabwe, tel. 263-4-860119 or 263-4-860055.

G. Nehanda, Chief Planning Officer, Head of Station, Institute of Agricultural Engineering, Post Office Box BW 330, Borrowdale, Harare, Zimbabwe, tel. 263-4-860119 or 263-4-860055.

A. Senzanje, Department of Soil Science and Agricultural Engineering, University of Zimbabwe, Post Office Box MP 167, Mount Pleasant, Harare, Zimbabwe.


Elwell, H.A. 1993. "Development and Adoption of Conservation Tillage Practices in Zimbabwe." FAO Soils Bulletin 69, Soil Needs in Africa Needs and Challenges. FAO, Rome.

FAO (Food and Agriculture Organization of the United Nations) 1966. Equipment of Tied Ridge Cultivation from Power and Machinery. Informal Working Bulletin No. 28, Rome.

Vogel, H. 1992. Conservation Tillage for Sustainable Crop Production Systems. Project Research Report 5, Institute of Agricultural Engineering (IAE), Harare.

4.2 Freshwater augmentation - cloud seeding, Zimbabwe


Zimbabwe covers 390 000 km2 in area, and has a population of 10.4 million people (CSO, 1992), of whom 74.3% (or 7.73 million) are rural (CSO, 1989). The country is situated in southern central Africa between latitudes 15° 30' and 22° 30' South and between longitudes 25° 00' and 33° 10' East. The country falls into various land use (agro-ecological) zones determined by rainfall, temperature and soil types as shown below. The country has a seasonal rainfall pattern, which varies across the country, with the highest rainfalls of over 2 000 mm falling in the Eastern Highlands and the lowest rainfalls of around 400 mm falling in the low areas, particularly along the area bordering South Africa. In the middelveld, the rainfall varies from 700 to 1200 mm. Runoff is generally 8% of the mean annual rainfall (DWD, 1980). The majority of rivers are non-perennial. An attempt to fully utilize this runoff has led to an extensive dam construction programme. While these reservoirs are used as sources of water for mainly urban centres, some supply water for irrigation and mining purposes.


% of Land Area




Very high rainfall, above 1000 mm; low temperatures, below 15 °C.
Forestry, wattle, tea, coffee, deciduous fruit, barley and potatoes.
Intensive beef and dairy fanning.



High rainfall, 700 to 1000 mm; warm summers, cool winters.
Maize, tobacco, cotton, winter wheat and market gardening - intensive farming. Intensive beef and dairy farming.



Moderate rainfall, 550 to 700 mm; high temperatures and dry spells.
Drought resistant cotton, soya and sorghum. Beef farming and breeding.



Low rainfall, 450 to 600 mm; seasonal droughts.
Irrigation of drought resistant crops.
Semi-extensive controlled grazing.



Very low rainfall, below 500 mm; very hot
Sugar, citrus, cotton and wheat irrigation schemes of lowveld.



Not suitable for agricultural activity without irrigation.
Some beef production and wild life.

Source: (School Atlas for Zimbabwe)

The majority of Zimbabweans live in the communal and resettlement areas where they rely on agriculture for a living. Commercial agriculture is a major contributor to the country's economy.

The country, therefore, is heavily dependent on agriculture, and, as a result of recent droughts, precipitation augmentation has become a vital component of this economic sector.

Rainfall augmentation operations are carried out during all seasons which do not have sufficient natural rainfall.

Technical Description

This technique involves the beneficial modification of summer convective rainfall to increase rainfall production efficiency. Only about 30% of the atmospheric water vapour entering the region's storms naturally reaches the ground as precipitation (McNaughton, 1980). The approach encourages efficient rainfall formation through a collision - coalescence process which is enhanced or accelerated by the addition of hygroscopic nuclei into a storm updraft at cloud base. Augmentation provides additional water to crops when weather conditions are favourable and is required during periods when little or no rainfall would otherwise occur.

In Zimbabwe two methods of cloud seeding are used:

(a) The high level seeding method which has been used since cloud seeding was first practised, and which involves flying into the top of a suitable cloud and injecting it with silver iodide.

(b) The low level seeding method which is experimental and involves burning flares which emit hygroscopic smoke material into the base of a cloud.

This technology is described in Part B, Chapter 1, "Agriculture."

Operation and Maintenance

Major equipment requirements are aircraft, radar, materials and skilled personnel. In this instance, the aircraft were supplied mainly by the farming community, with the government paying for their use, with some additional aircraft supplied by the government. One problem was the shortage of aircraft. The numbers of aircraft were hardly enough for a comprehensive aerial coverage.

Aircraft and personnel are on standby during the rainy season, waiting for the right clouds/conditions. The main rainy season in Zimbabwe is from November to March. Rain sometimes falls in other months, mainly September, October, April and May, and, during the rainy season, there are spells of completely dry weather. Therefore, an operational cloud seeding organisation would normally be inactive on about half of the days in the rainy season, including occasions which are too wet for additional rainfall to be required.

Level of Involvement

The private sector, in particular the fanning community, assisted governmental implementation of this technology, mainly with aircraft. Thus, in this application, there was a high degree of community involvement, but this could vary in other applications.


Average annual cost of Zimbabwe's national cloud-seeding operation between 1973 and 1979 was about $10 000. The highest annual cost was $13700 in 1978/79, which was the busiest season ever, during which chartered aircraft were used. For the 1995/96 season, $12500 has been set aside for cloud seeding operations.

Effectiveness of the Technology

It was observed in Zimbabwe that the cost of cloud seeding was significantly less than the resulting benefit from the maize yield alone. This analysis did not take into account other crops or non-agricultural benefits. Hence, cloud seeding is considered to more than pay for itself (McNaughton, 1980).


In Zimbabwe, the extra maize yield from the national cloud seeding programmes in the late 1970s was estimated at between 0.5% and 1% of the national total (McNaughton, 1980). Pastures and grasslands also benefited. Further, seeded rainwater was determined to be cheaper than piped water with respect to irrigation ($0.12/km3 versus $1.76/km3; McNaughton, 1980). Extra benefits accruing from the cloud seeding programmes included: (i) fog and stratus disposal around airports; (ii) hail suppression; and, (iii) cyclone (hurricane) modification.


Experimental operations are costly, often requiring the simultaneous use of three aircraft - one for seeding, a second to monitor weather conditions (such as cloud top temperatures during the five to ten minutes after seeding), and a third to measure precipitation at the cloud base in a rain collector. Cloud-seeding operations/aircraft have to select suitable clouds as they arise. This selection cannot be controlled or easily predicted in the long term. Therefore, it is difficult to supply water when and where it is required. Also, chartered aircraft are expensive to operate from the point of view of standing charges.

Further Development of the Technology

Currently the Zimbabwe cloud seeding fleet has aircraft based in Harare and the Lowveld. Depending on the occurrence of potentially suitable clouds during the height of the wet season, additional aircraft should be made available during January or February. If maize is planted in December, it is recommended that at least one aircraft should be on standby until late April. While jet aircraft can cope with larger numbers of clouds, and, therefore, reduce the number of cloud seeding aircraft required, these aircraft are more expensive to operate. There is also a need for a daily radiosonde data in areas with a high suitability for cloud seeding during this period, and a need to carry out further experiments with reference to the atmospheric conditions which permit cumulus development.

Information Sources


W. Marume, Department of Meteorological Services, Post Office Box BE150, Belvedere, Zimbabwe.

Kamanzira, Department of Meteorological Services, Post Office Box BE150, Belvedere, Zimbabwe.


McNaughton, D.L. 1980. Cloud Seeding in Zimbabwe and Some of its Effects on SR52 Maize Growth. PhD Thesis, Faculty of Agriculture, University of Zimbabwe, Harare.

Meteorological Department 1993. Reports on National Cloud Seeding Operations. Department of Meteorological Services Reference File - National Cloud Seeding Season 1992/93, Ministry of Transport and National Supplies, Belvedere, Zimbabwe.

4.3 Tidal irrigation, the Gambia


The Gambia is one of the smallest countries in the Sahel region of West Africa, surrounded on all sides by Senegal, except on the western side of the country which borders the Atlantic Ocean. The Gambia is bisected by Gambia River and lies in the east-west direction between the longitudes 16° 50' and 13° 45' W and latitudes 13° 00' and 13° 50' N. The country is approximately 480 km long and nowhere is it more than 50 km wide. Its total surface area is about 11 000 km2, with about one third of its surface area covered by the Gambia River and the marsh lands along its banks. The main topographic feature is the low lying basin of the Gambia River. The river runs through the whole length of the country with only a few points above 50 m in elevation. Its capital is Banjul.

The Gambia has savanna vegetation and lies in the Sahel of West Africa. The climate is uniform across the country due to its small size and relatively flat features. The country has a single rainfall season annually, which starts in June and ends in October. The rainfall in the country varies evenly from 1 100 mm in the south-west to 700 mm in the north and east. The rainfall is highly seasonal with all but 1% or 2% falling in the raining season.

The Gambia River rises in Guinea and passes through Senegal before finally entering The Gambia for an approximately 500 km journey to the sea. The flow in the river is highly seasonal. The maximum flow occurs at the end of the rainy season in late September or October with a flow of about 1500 m3/s. The minimum dry season flow is less than 4.5 m3/s, both measurements taken at Gouloumbo in Senegal. Due to the large variation in river flow and the flat nature of the country's terrain, the Gambia River is tidal, and thus saline, for much of its length.

The position of the interface between the freshwater and saltwater varies with river flow. During the low flow period, the freshwater-saltwater interface, defined as the point at which the salinity is 10 ppt, is 250 km from the sea. Under high flow conditions, this interface is located 150 km from the sea. Due to the perpetually saline conditions which exist in the Gambia River and its tributaries for 150 km from its mouth, where the population centres and tourism facilities are located, surface water is rarely used as a source of potable water in The Gambia. The potable water demand for urban areas, tourism, industry, and irrigation and livestock watering comes from groundwater sources.

Groundwater is available in all parts of The Gambia. The country is located on one of the major sedimentary basins in Africa often referred to as the Mauritania/Senegal Basin. It is characterised by two main aquifer systems with water table depths varying from 10 m to 450 m.

Technical Description

This technology is intended to supplement rain fed agriculture. The availability of tidal water at high tide was used as source of irrigation water supply. Due to the use of this technology, a double cropping of rice is achieved annually in a country with seven months of dry season.

The land along the Gambia River is relatively flat, and, since the river is tidal all through its length in The Gambia, tidal irrigation schemes become feasible. Tide heights vary from 3.5 m at the mouth of the river to 0.9 m at Basang, 310 km upstream. Special intake structures were constructed with gates which, when opened at high tide, allowed tidal waters to enter irrigation channels leading to the farms. During high tide, the gates were opened from 3 to 24 hours, depending on the size of the area to be irrigated. In two rice growing areas, at Jahally and Pacharr, tidal and pump irrigation are coordinated. Tidal heights of 1.3 and 1.0 exist in the Gambia River at Jahally and Pucharr, respectively (Figure 45). Tidal water is utilized to irrigate low lands nearer the banks of the river while water is pumped from the river to irrigate large areas of land at higher elevations. The project began operations in 1983 and 1984 at Jahally and Pacharr, respectively.

This technology is described in Part B, Chapter 1, "Agriculture."

Figure 45. Jahally irrigation pumping units.

Effectiveness of the Technology

The technology has been successful in paddy rice cultivation as a rural development project. Using tidal irrigation, double cropping of 167 ha and 850 ha was achieved annually at Jahally and Pacharr. Similarly irrigation of 440 ha and 125 ha is achieved annually at Jahally and Pacharr, respectively using pump irrigation (Figure 46).

Figure 46. Jahally irrigation field.


The projects were financed by the Gambian Government, the International Fund for Agricultural Development (IFAD), the African Development Bank (ADB), and the German Government. During the design and construction stages, the project management was in the hands of the financier and exact capital cost figures were not available from the current local project management. Nevertheless, the estimated cost of the project, in 1983/84 dollars, was approximately $7.5 million. Assuming a 7% inflation rate, a 25-year life, and 7% discount rate, the annual cost of project may be estimated at $643 583, or $40/ha. Current operation and maintenance costs are $220/ha/yr. The resultant yield per hectare is 9 tons/yr, incurring an annual cost per unit of output of $70/ton.


The technology is appropriate in areas where there is a river with a relatively flat basin and high tide intrusion. Arable land must be available near the banks of the river. The rainfall in the area must be sufficient to encourage constant and high river flows. The technology is also good for use in areas with fairly large rivers and sufficient rainfall to keep the water level high. The rivers must also be tidal.

Operation and Maintenance

Trained local staff must be available to perform the farming operations and management. Additional manpower needed to implement this technology include: (a) one power tiller operator for each 15 ha cultivated per month; (b) two tractor operators; and, (c) two experienced mechanics. There should be about 20% local community control or management.


This technology is good because, once the intake structures and irrigation channels have been constructed, the operation is relatively cost free. Maintenance work on the irrigation channels and clearing of weeds and brush from the channels and irrigated area can be done by the local farmers.


There is a difficulty being experienced in the availability of spare parts locally.

Environmental Benefits

The breeding of mosquitoes and snails is enhanced by water ponding on the farms, which could lead to public health concerns if control measures are not imposed.

Cultural Acceptability

No cultural inhibitions have been experienced. This technology provides for viable commercial farming in a poor rural area.

Further Development of the Technology

No further development appears to be required at this time.

Information Sources

Director, Department of Water Resources, 7 Marina Parade, Banjul, The Gambia.

4.4 Spring protection - Mukono district, Uganda


This study outlines the experiences gained during the implementation of spring protection programmes in the Mukono District of Uganda during the RUWASA project. Mukono is one of eight RUWASA project districts. The project aimed at improving the quality of life of the rural people through provision of water supply and promotion of sanitation and good hygiene. The project was identified in 1989, after the area was found to have harsh socio-economic and health conditions related to poorly developed water supplies and poor sanitation.

The Mukono District lies between 32° 30' 30" and 33° 25' E, and latitudes 1° S and 1° 30' 30" N. The district is bounded by rivers on the east and west, Lake Victoria on the south, and Lake Kyoga on the north. The northern and central parts of the Mukono District are underlain by undifferentiated gneiss of the basement complex. Recent sediments cover the contour boundary along the Nile. The southern parts are underlain by the Buganda Toro system (granitic and partly metamorphosed rocks) with basement complex (granite gneiss) exposures running in a northeasterly and southwesterly direction. From a monotonous flat topography in the north, the land changes to an undulating topography in the central parts, becoming hilly in the southern parts. The central parts have intermediate to thick overburden while the southern parts have very thick overburden in the Buganda Toro system areas. Rainfall varies from an average of 1 010 mm/year of rain in the northern half to 1625 mm/year in the south.

In 1991, the population was 750000 people. The population was largely rural, with over 90% residing in the countryside. The majority of the people are self-employed in agriculture, growing food crops for domestic consumption with the surplus, if any, being sold to urban centres.

The water and sanitation coverage in 1991 was about 10% and 30% of the population, respectively. It was estimated that water sources in the District were distributed as follows: 21% spring sourced, 43% shallow well sourced, and 36% borehole sourced. An inventory carried out in 1990, however, indicated a great number of protectable springs were located primarily in the south. Bacteriological tests showed that most of the springs were contaminated with faecal coliform bacteria.

Technical Description

The RUWASA spring protection project started in 1990. To date, about 800 springs have been protected in the Mukono District, benefiting an estimated 120000 people. Protection activities start with source identification carried out by technical officers and the community. The criteria used to recommend a spring for protection include the following:

(i) There should be at least 50 users, or about 10 households for the protection project to be economically-viable.

(ii) The spring should be perennial (confirmed by the users).

(iii) The spring should have a flow greater than or equal to 10 l/min.

(iv) There should be an adequate ground slope to provide ample drainage after construction of the retaining wall.

The structure or retaining wall placed around the spring to be protected was originally constructed using stones and/or hard core. However, this was changed to concrete blocks, except in the case of the wing walls. This was because stone-masonry work was slower since the stones provided by most communities were small, and greater skills are needed by the mason to fit the stones into the wall. The skill of the masons may be a problem in the application of this technology elsewhere, especially with new masons. A 2½ inch galvanised iron pipe, used to protect the PVC outlet pipe, is cast into the retaining wall flush with the back and extended 50 mm at the front. At the back it is sealed off with cement mortar in order to avoid contact with the spring water. The 50 mm extension offers a good outlet, making the water easy to draw with the water buckets, but too small to make it an attraction for children to stand or sit on. It is important not to block off any spring eye.

The work of clearing and digging the drain, with an appropriate notch shape and slope, that protects the spring from surface runoff and from back flows into the spring from the surrounding land surface, tends to be rather hard, and the communities tend to leave it uncompleted. Thus, they have been encouraged to complete work on the drains in one operation before any of the other work takes place.

Extent of Use

Natural springs have traditionally been used as a source of water, especially for domestic purposes. This project has improved the protection of such springs from pollution and improved the method of collecting and distributing the spring water. The technology, therefore, is acceptable, especially since the water acquired from the springs is softer than most deep borehole water.

In a few cases, people have tried to resist the implementation of spring protection measures for fear that the eyes of the springs would disappear. These fears have been minimised by informing people about the causes of such disappearances, and by demonstrating examples of protected springs in neighbouring villages.

The speed with which protection is implemented is affected during the rainy season because, during the planting season, people are busy in the fields. The rains also make some roads impassable, and the delivery of materials difficult.

Operation and Maintenance

The operation and maintenance of spring protection systems is well within the capacity of the local communities. Apart from keeping the area surrounding the spring tidy, maintenance consists of fencing sensitive areas, especially the area behind the retaining wall, and maintaining the storm water and runoff drains.

Level of Involvement

The responsibilities of the communities in each of the spring protection projects undertaken during the RUWASA project included: (a) selection of at least six members of the community to create the Water User Committee (WUC); (b) selection of two caretakers, one of whom must be a woman; (c) provision of manual labour and locally available materials for use in the protection project; and, (d) assisting in construction work on a self-help basis.

Prior to the construction of the protection works, the community is responsible for clearing the drain and providing hard core, plaster-sand, and clay, where available.

The responsibilities of the WUC include: (a) ensuring that individual members actively participate in the construction activities; (b) ensuring that the water sources are well looked after; (c) assisting and supervising the caretakers in carrying out their assigned duties; (d) proposing and enforcing by-laws, approved by the water users, regarding the use and up-keep of the village water supply; and, mobilising the community through the promotion of sanitation and hygiene education activities.

The government or project manager produces guidelines for community based operations and maintenance activities; facilitates the training of caretakers and the WUC; and, pays for the skilled labour (masons and supervision), the transportation of materials to the site, and the acquisition of locally unavailable materials. Such materials may include cement, pipes, and lake sand.

A further pilot project, using the private sector operators, started in 1995. The private contractors carry out the physical construction under government/district supervision, and with coordinating input from the village.


Protection of a spring is estimated to cost about $1 000. The value of the in kind community contribution (unskilled labour and locally available materials) is also estimated to average $1 000. Materials provided by the community are mainly sand, hard core and clay.

Effectiveness of the Technology

In general, the spring protection project was considered successful, although a high proportion of the springs continued to fall above the bacterial water standard. Unfortunately, during the 1993/94 drought, a large proportion of the protected springs were reported to have dried up. Notwithstanding, a study in May 1994 showed that, of 743 springs checked, 52% passed the minimum design yield criterion of 5 l/min, 42% were over 7.5 l/min criterion (the theoretical minimum to supply 20 litres per capita per day to 150 people over 8 hours, with 20% spillage), 34% were over the criterion of 10 l/min required for a spring to be protected, and 26% were completely dry. Over-night storage tanks are being constructed for low yielding springs.

Given the community concerns regarding the drying of springs, additional investigations were made of the 26% of springs that have become dry. Some reasons for drying were found to include:

(i) Poor construction due to the contractors not following the specifications (e.g., the wall not being carried down deep enough, or the spout placed too close to the top of the water table so that even a small drop in the water table results in the spring drying up).

(ii) Blockages of the spout, usually with a banana, in order to "save" the water which can result in a build up of a water pressure and the groundwater finding an alternative route to the surface at another location.

The studies showed that there was no difference in the protection provided to the springs in which polyethylene materials were used instead of clay as a seal.

Because of the early concerns regarding the contamination of the springs, investigations into the water quality of the protected springs were also conducted. Water quality in the protected springs was generally satisfactory from a toxicological point of view as shown below. However, a survey carried out in the wet season showed that 3% exceeded the 50 Escherichia coli counts per 100 ml (EC/100 ml) criterion, 12% exceeded the 25 EC/100 ml criterion, and 52% exceeded the 3 EC/100 ml criterion. (Faecal coliform measurements were not made.) In 65% of cases investigated, there were higher levels of contamination at the household level than at source level, indicating that contamination occurred within the distribution system.


Percentage Exceeding: Criterion


0.5%: 300 mg CaCO3/l

Total Iron

0.5%: 1 mg/l


4.8%: 0.1 mg/l

Chloride, Sulphate and Nitrate


Total Dissolved Solids

0.2%: 1500 mg/l


1.3%: 1 mg/l


95.7%: 5 units

Other studies have suggested that springs located within less steep countryside had a higher percentage of better quality, in terms of both coliform counts and turbidities, than springs located in steeply sloped areas. It was also found that better the maintenance of the spring, such as maintaining the storm drainage, resulted in better the bacteriological water quality.

Some communities have started growing vegetables to take advantage of the continually flowing spring water.


The advantages offered through the use of spring protection technologies include:

(i) Ease of construction and maintenance, as a high level of technical knowledge is not required.
(ii) Improvement of a community water supply already used and accepted by the community.
(iii) Low cost of construction and maintenance.
(iv) A potential to up-grade the system by collecting the water in a tank and pumping it up a storage tank and distributing it through a pipe system as economic conditions permit.


The disadvantages of spring protection technologies include:

(i) No improvement in the service level associated with the community water supply, since protecting the water source has not effect on walking distance to the source.

(ii) Interference with the flora and fauna down stream if a storage facility is provided in case of low yielding springs, since spring water is retained at the source.

(iii) Poor accessibility if the spring is located at the bottom of a hill and most households are located on the hilltop.

(iv) Limited improvement in the bacteriological quality of water and continued difficulty in improving the quality to a higher standard.

Further Development of the Technology

Although the village inventory indicated a great number of protectable springs (3 200), only 40% met the project criteria for protection. Many reported springs were traditionally dug water holes in valley bottoms that could not be protected through this programme. Spring identification should be carried out during the dry season to minimise risk of protecting seasonally drying springs. Declines in the water table due to drops in rainfall were a major cause of drying springs. More detailed water resources studies are required to document the relationship between rainfall (seasonal and annual variations) and spring yields. In the meantime, the minimum yield criterion for a spring to be considered for protection was revised from 10 l/min to 15 l/min, and, in the case of low yielding springs, construction of a storage tank to collect water overnight is being explored and should be considered. The work plan for construction of spring should take into account the seasons (e.g., the demand for labour during the planting season).

Human activity in the catchment area of a spring has a big affect, especially on the bacteriological quality of the water. Preferably, 30 m around and upgradient of a spring should be kept free of human activity to minimise the potential for contamination from this source. By-laws to this effect should be encouraged where possible. There is a need for improved and recorded observations on spring site features which might correlate with the vulnerability of the spring to pollution. Similarly, monitoring and record-keeping relative to the sensitivity of a spring to seasonal discharge changes would be desirable. Some general monitoring of subsequent performance of the spring would also provide valuable information with which to measure project success. Rural water quality guidelines should take into account the resources available and the coverage of public water supplies. In this case, if the project guidelines were strictly followed, 52% of the water sources which provide water to over 60 000 people would be condemned on the basis of excessive E. coli counts. Notwithstanding, hygiene education, especially the safe water chain, is important as the contamination level at the point of drinking in household is much higher than at the source.

Information Sources

DANIDA (Danish International Aid Agency) 1995. Project Document: RUWASA Phase II. DANIDA, Copenhagen.

Geria, I. and UNICEF (United Nations International Childrens Emergency Fund) 1993. The Potential for Different Abstraction Technologies for Rural Water Supply in Uganda. Ministry of Natural Resources.

Kruger, I. 1990. National Rural Water Supply Programme: Republic of Uganda. Nordic Consultancy Group.

RUWASA East Uganda Project 1993. 1991-1992 Data And Experiences. Directorate of Water Development, Uganda.

RUWASA East Uganda Project 1994a. Phase II Strategy Report. Directorate of Water Development, Uganda.

RUWASA East Uganda Project 1994b. Status Report. Directorate of Water Development, Uganda.

4.5 Water augmentation - Laikipia district, Kenya


This case study describes the experiences gained during the planning and implementation of a rainwater harvesting project at three locations in Laikipia District of Kenya (Sipilili, Olmoran and Machunguru Locations). The project demonstrated that a well-planned rainwater harvesting initiative can bring about sustainable development in communities in an isolated and marginal area, far from riverine water sources.

The Laikipia District lies on the leeward side of Mount Kenya and has an annual average rainfall of approximately 700 mm. Rain falls in two distinct seasons, known as the long rains and short rains. The area is categorized as semi-arid. The communities in the three locations comprise subsistence farmers growing crops (mainly maize and beans) and keeping livestock (cattle, sheep and goats). There are frequent droughts, resulting in frequent crop failures and decimation of the livestock herd.

Prior to the initiation of the rainwater harvesting project, most of the people living in the three locations did not have access to clean water. The only source of domestic water was from earth dams situated far away. The dams were also used for livestock watering. There was considerable soil erosion arising from inappropriate farming practices, resulting in heavy sedimentation in the dams. These factors rendered the water unsafe for human consumption. The heavy sedimentation also reduced the volume of water in the dams to such an extent that there were times when water was not available, even for domestic use. The dams had to be desilted, manually, every third year, which placed a tiresome burden on the communities.

Further, many households had no pit latrines and the level of basic hygiene was low. The lack of availability of safe water, low levels of nutrition and poor health status resulted in an overall situation at the homesteads of dependency, desperation and insecurity. Many of the subsistence farmers abandoned their plots and went to urban centres in search of employment.

In the light of these circumstances, the Laikipia West communities in 1985 requested the Church of the Province of Kenya to initiate a community-based resource mobilization project. The project is still operating, and, apart from its own activities, has worked in partnership with the Ministry of Health's environmental hygiene programme, the Ministry of Agriculture's soil conservation activities, and the United Nations Development Programme (UNDP) - supported Pastoral Water Programme, as well as with other, similar initiatives.

Participatory rural appraisal (PRA) was used as the means of initially identifying the major problems. The exercise involved the villagers, and pointed to the need for a human-centred approach in which peace, security, improved quality of life, preservation of the environment, justice and democracy were important elements of development. From the PRA, it became evident that the type of land use and farming practices in the area were unsuitable as they resulted in serious soil erosion, gully formation, general land degradation and inadequate agricultural production to sustain the families. Water was identified as the top priority among the communities, the traditional sources being too distant from the homesteads.

Women were spending considerable time in fetching small quantities of water, which had been rendered inadequate through drought and unsafe through pollution. Assessments showed that other sources of water such as groundwater were inaccessible at great depth and often saline. It therefore was necessary to design an alternative intervention that was based on both social and technical considerations.

In this regard, rainwater harvesting was considered a feasible option which addressed not only water supply issues but also other areas of social and economic development, such as the improvement of health and agriculture. The concept of rainwater harvesting was not new to the communities as many homesteads were already using household utensils to collect drinking water from rooftop catchments, and a few had developed techniques for collecting runoff water for use in irrigating their home gardens. However, only 25% of homesteads had corrugated iron roofs essential for roof catchment water harvesting. It therefore became necessary to gradually develop additional techniques to provide water for households.

Technical Description

The water augmentation programme began by introducing 2001 drums and 2 5001 water tanks for collection of roof catchment water. Based upon the demonstration of the potential of these small containers for rainwater harvesting, the communities decided to venture into large systems, and, by the end of the project, they had constructed several 10 0001 ferrocement tanks to capture and store rainwater.

The extension strategy adopted involved provision of technical advice which included, for example, advice on the calculation of the correct volume of tank in relation to the roof area and the amount of expected rainfall. Training was also provided in construction techniques such as determining the proper material mix, the slope of the gutter and the provision of splash-guards. Thereafter, the villagers did the actual construction. Both men and women participated in the programme. Women built the tanks on site while men were more interested in being trained in the techniques of tank building. One outcome of the project was that it promoted gender-balanced participation in the planning, as well as in the construction and maintenance, of the water facilities.

This technology is described in Part B, Chapter 2, "Domestic Water Supply."

As previously noted, other measures were also implemented during this programme. Laikipia is a semi-arid district, and soil moisture is the most limiting factor in crop production. Supplemental moisture, therefore, is necessary to ensure a harvest. Farmers were encouraged to practice runoff farming. The technique involved directing runoff from roads and upper slopes into groundwater tanks or directly onto the gardens for macro-irrigation using bunds made of soil and stones. Farmers were also encouraged to practice soil conservation, to establish tree seedling nurseries, and to plant trees around the boundaries of their farms, along the contours, and around their homesteads. They were also encouraged to plant communal and individual woodlots. Planting vegetative cover along soil conservation bunds was also promoted. These practices are reported to have increased food production on a sustainable basis.

These technologies are described in Part B, Chapter 1, "Agriculture."

Extent of Use

Maize production was increased as a result of improved land use and runoff farming techniques. In the Machunguru area, for example, yields were 8 bags of 90 kg each (720 kg) per acre prior to the initiation of the project, while, today, good farmers can attain yields of 20 bags (1 800 kg) per acre. The additional maize stover produced is fed to livestock during dry periods.

Prior to the water augmentation programme, vegetables were not grown in the area, but were obtained from Nyahururu and Nyandarua some 100 km away. Improved land use and runoff farming techniques have enabled vegetable production to meet household requirements and provide surpluses for sale to augment household incomes. In addition, farmers have diversified their crops from the traditional maize and beans to include potatoes, carrots, onions, soya beans, millet, bananas and fruit. This diversity has contributed greatly to food security and balanced diets.

Likewise, prior to the water augmentation project, the semi-arid area had very few trees, the original trees having been cut down for building, charcoal burning and for fuel wood. As part of the development package, the project encouraged production of tree seedlings and planting of trees within homesteads, along farm boundaries and contours, and in fanned woodlot, as well as afforestation on communal hilltops. Enterprising farmers derived considerable income from the sale of seedlings.

Operation and Maintenance

A number of in-ground storage tanks were built by the community to take advantage of, and maximise, the efforts made toward, and the benefits from, soil and water conservation in the District. Runoff water from roads, the upper reaches of slopes, and rooftop catchments was directed towards these tanks. The water so harvested had various end uses, including vegetable production and livestock watering.

Although the programme was centred on the provision of water, the project had some spin-offs and positive effects on other sectors of community development. This is attributed to the fact that members of the community were interacting continuously in a participatory manner, exchanging ideas and learning from each other. In addition the existence of an organized community made it easier for extension services from other agencies to deliver advice.

Effectiveness of the Technology

The use of contaminated water resulted in an high incidence of water-borne diseases. Stomach and other gastro-intestinal ailments were prevalent. Costs for medical treatment for a family were as high as Ksh 700 per annum ($15, or one month's wages for an average Kenyan). Availability of clean drinking water from the rooftop catchments reduced the incidences of these diseases, resulting in fewer sick days, increased economic activity of members of household, and savings in medical expenses which could be redirected to other household expenses.

It was also observed that increased levels of food production, accompanied by crop diversification, reduced the once prevalent high levels of malnutrition. Households had improved calorie intakes and more varied diets than was the case before the project was initiated.

Further, the number of households with corrugated iron roofs increased from 25% of homes to 70% of homes during the 10 year period. At the same time, the number of houses with sufficient rooms to accommodate family members, and those showing other improvements, increased from 40% to 70% of housing units.

As in the case of water supplies, the availability of toilet facilities is essential to maintaining the public health. The numbers and types of latrines built were continuously monitored during the project period. Within the project area, the percentage of simple pit latrines doubled, improved latrines tripled, and VIP latrines rose from zero to 24% of household units.


The performance of this project can be measured by its outputs and the benefits it brought to the communities. In all cases, the approaches taken and technologies used during this project were not only suitable for the area in which they were applied but they were also successful in achieving the broadly-based goals of the programme under which they were carried out. The key achievements can be summarised as follows:

· Approximately 1 000 tanks of various types and sizes were built by the communities, with technical advice and essential material assistance provided by the project, providing approximately 9 600 people with access to water.

· A significant number of households became involved in various rural development activities that did not exist in the area prior to the project.

· The percentage of households involved in vegetable growing, tree planting and seedling production, and home improvement activities increased from zero to 100% (vegetable growing); 90% (tree planting); 50% (tree seedling production); and 70% (home improvements).


No. of tanks built

No. of people served













Further Development of the Technology

Several independent evaluation teams state that, after 10 years of implementation, the program has considerably improved the living standards of the communities, with regard to water availability, public health improvement, farm management, and overall socio-economic status of the people. The project was planned and implemented in such a manner that the activities initiated should be self-sustaining, replicable and sustainable.

Information Sources

Rolf Winberg, Swedish International Development Authority, Post Office Box 30600, Nairobi, Kenya.

4.6 Recycled water - Achimota Brewery, Ghana

Technical Description

The process involves the use of recycled water to blend with incoming cold water as feed water for boilers. Hot water obtained in the process is used in the brewing process or as a boiler feed water and filling pasteurizer. This technology is described in Part B, Chapter 3, "Mining and Industry."

Extent of Use

This technology is used in the brewing and bottling industry in Ghana, and specifically at the Achimota Brewery.

Operation and Maintenance

The regular maintenance of the mechanical systems is done by trained artisans employed by the Brewery.

Level of Involvement

The level of involvement is primarily within each factory and is, therefore, industry specific. Generally, the availability of trained artisans is the principal requirement for implementing this technology.


Initial capital costs may be high if plant operations need to be restructured and new equipment installed. However, these costs are usually offset by the long-term savings in water costs. No information on operating and maintenance costs is available, but the costs may be assumed to be reasonably low and similar to the cost of using conventional technologies.


This technology is suitable in any industry that demands a large volume of boiler water. The application used within the Brewery is similar to that applied to thermal power generation cooling systems (described in Part B, Chapter 3, "Mining and Industry").


Use of this technology, which can be easily integrated into the industrial process, results in a significant savings in both water demand and water costs in the industry. The technology also can be easily modified to include other sources of blending water such as groundwater.


Use of this technology is limited in application to situations where there are heat exchangers. Also, impurities within the blended water stream may result in boiler scale.

Further Development of the Technology

This is a fairly old technology. Current research is focusing more on improving the efficiency of the boilers rather than on the degree of recycling.

Information Sources

Achimota Brewery Limited, Achimota, Accra, Ghana.

4.7 Water recycling - Tarkwa gold fields, Ghana

Technical Description

In this process, groundwater and wastewater from drilling operations are pumped into an underground sump. The sump water is raised in stages into a surface reservoir where it is mixed with raw water pumped from streams. The water in the reservoir is allowed to settle.

Through this process of dilution and sedimentation, water quality is improved, and the water is then recycled for use in underground mining operations.

This technology is described in Part B, Chapter 3, "Mining and Industry."

Extent of Use

This technology is used by mining operations in the Tarkwa gold fields in Ghana.

Operation and Maintenance

This is a very flexible system, quick to install and designed to provide only a limited supply of process water to any location where water is needed. The pumps normally operate 10 hours per day.

Level of Involvement

This technology is industry-specific and is generally operated as part of the production process within the specific industry. Trained personnel are needed to maintain the pumping systems.


Costs are difficult to determine, but capital costs can be assumed to be high given the need for pumps, pipelines and related equipment. Operating costs, however, are probably similar or somewhat less than the costs of using raw water for the same operations.

Effectiveness of the Technology

And water supply. It has proven to be very effective in conserving water resources, while meeting the production demands of the industry.


Water re-use systems can be installed in any sub-surface mining operation. The possibility of including a water treatment system within the pumping network, to upgrade water quality if necessary, is high.

Environmental Benefits

By containing the contaminated water generated in sub-surface mining activities, direct pollution of surface water resources is minimized. Contaminants are typically sediments and other dissolved chemicals which are amenable to removal using conventional treatment methods. However, the disposal of waste products should be monitored to limit negative inputs on the environment.


Use of this technology limits the pollutant load to surface and ground waters.


The technology, which is based on pumping, has a high energy demand.

Further Development of the Technology

The advantages to be gained from using this system depends on the quality of ore purification to be achieved, and the chemical processes used. Therefore, any future development of the technology has to be in the area of in-line water quality improvement.

Information Sources

Goldfields Corporation, Tarkwa and Ashanti Goldfields Corporation, Ghana.