River diversion schemes
Smallholders traditionally use water as a common property. Water is used according to customary laws of each area and proximity guides the rights to use water. Two main sources are common in the smallholder irrigation: (a) direct river diversion, where the gravity method of irrigation is practised, in regions such as Arusha, Iringa, Kigoma, Kilimanjaro, Lindi, Mara, Mbeya, Morogoro, Mtwara, Rukwa, Ruvuma and Tanga. This method accounts for about 60 percent of the total area under smallholder irrigation; (b) water harvesting, where flood waters from seasonal streams/rivers are captured and stored for future use, in regions like Dodoma, Tabora, Singida, Mwanza and Shinyanga. This source accounts for about 30 percent of the irrigated area.
Average size of irrigation plots varies from 0.1 to 0.5 ha with farmers owning two to three plots. The size and location of the plots are not uniform. In some of the rehabilitated schemes like Majengo, Lower Moshi, Ndungu and Mwamapuli, plots are consolidated and contiguous.
Groundwater is extracted by open/dug wells or boreholes with a 12 to 20 cm diameter. Pumping accounts for a comparatively lesser proportion of the irrigated area as pumping groundwater for irrigation is very limited. Only about 480 ha are irrigated from lakes and about 200 ha from groundwater using both diesel and electric powered pumps. Hand pumps are used to irrigate vegetables in small plots in the towns. Municipal water is also used to irrigate kitchen gardens and vegetable plots.
Currently, only hand pumps for domestic water supply are manufactured locally by companies such as Tanira. The import and use of a particular type of equipment is also related to the donor country funding the rehabilitation works. In general much of the mechanical pumps are used for domestic and industrial purposes.
The recently completed National Irrigation Development Plan (NIDP) document by the Ministry of Agriculture has also mentioned the cost of development of shallow well to be about US$ 3000/ha (MOA, 1994). Hence there is a need to examine how the technology could be introduced at a cost which smallholders can afford.
Small earth dams
Runoff and rainwater are stored behind bunds and used for irrigation in Ifakara-Mangula in the Morogoro region. These bunds resemble the traditional water harvesting structures in India known as 'tanks'.
Rainfall is mainly concentrated during the wet season. Given the vast terrain and gentle slope, it is possible to construct small to medium earthen structures called tanks to collect and store the run-off during heavy rains for supplemental irrigation in the wet season and full irrigation in the dry season. These tank irrigation systems are very common in southern India, Sri Lanka and Northeast Thailand. The tanks also meet the village water needs in the dry season. Discussions with irrigation experts indicated that a few tanks are already available in the country, but the potential will be about 20 000 ha whereas the technology is not explored on a large scale. The average cost of a tank to store about 30 000 m3 of water is $ 4 000 which will irrigate about 2.5 ha of paddy or 5 ha of other crops.
Shallow wells (open/borewells)
Although shallow wells are not commonly used for irrigation, farmers are aware of the pumping technologies, as a few private farmers are using pumps for commercial crops like coffee and sugarcane. Hydrogeological studies have indicated that the water table is shallow in several locations. Therefore, it will be economical to invest in small pumps such as hand and manually operated treadle pumps. Regions such as Dodoma, Singida, Shinyanga, Tobora, Morogoro, Arusha, Coast region, Dar-es-Salaam and Mara, offer scope for groundwater exploitation through shallow wells.
Open wells can be constructed by providing wall or rings to a suitable depth in the case of alluvial strata or clay soils. Boreholes of 12 to 15 cm diameter can be drilled to a depth of 6-10 metres by providing suitable casing or strainer pipes. Hand or treadle pumps can be fitted in the wells. Pumps based on human power could only cover a small area. Hence pumps using either diesel or electrical power may also be installed wherever farmers show interest. A group of 3-4 farmers can jointly install a diesel engine operated pump, as electricity is not available in rural areas in several regions. Farmers are responsible for the operation and maintenance of their pumps. The 3 HP diesel pump costs US $ 300 to 400.
In dambo or dimba irrigation, farmers use mainly open hand-dug wells and watering cans. Recently, demonstrations of rope and washer hand pumps were introduced at 25 sites. The DOI is planning to initially introduce 200 treadle pumps with a possible expansion to 1 600.
According to DOI staff, current prices for rope and washer pumps are approximately US$ 25. The cost of a hand drilled well including the concrete slab and the pump installation is US$ 35. The cost for the first demonstration was shared between the DIS, which provided the equipment and material and the farmer who provided unskilled labour for the well drilling and the pump installation. During the expansion phase of this programme DOI expects farmers to bear the total cost of US$ 60.
There is much scope for the local manufacturing and use of these technologies, since out of a total area of 600 000 ha of dambos and flood plains, only about 119 000 ha are used. However, the area of dambos which can be developed for irrigation is the focus of an IFAD study.
Small earth dams
Another irrigation technology involves storing rainwater behind an earth bund and using it for supplementary irrigation in the rainy season and full irrigation in the dry season. Additionally the dam can help recharge the groundwater which can be used for irrigation. The potential for this technology is very high due to the undulating terrain within the country. The DOI, through the IFAD programme, is surveying the existing earth dams and plans to use the data for the development of appropriate models.
Surface irrigation schemes
Government policy encourages the expansion of self-help small-scale smallholder irrigation schemes. The management of existing government operated schemes, mostly for rice production, will gradually be transferred to the beneficiaries. Improvement in the water diversion structures of the rice schemes, to reduce siltation, combined with canal lining and the introduction of other water control structures within the distribution network, is expected to substantially improve water management.
There are three smallholder sprinkler schemes. The Kambwiri irrigation scheme was constructed two years ago, at a cost of about US$ 6 000/ha. This cost however included the technical assistance cost. The semi-portable sprinkler system with light galvanized handmoved laterals was adopted. The Diamphwe sprinkler scheme, was constructed in 1992 also at a cost of US$ 6 000/ha, including the technical assistance cost. In both cases the designed systems are based on imported light galvanized steel laterals and sprinklers. However the costs would have been reduced substantially by adopting the drag-hose system, which in addition to the lower cost, is less taxing to the women and repairs can be done by the farmers in the field. This system is successfully used in Zimbabwe. The cost of this sprinkler system is estimated at US$ 1 500 to US$ 2 000/ha. Existing PVC factories are already producing the PVC pipes needed for this system. The factories can also manufacture the reinforced hose.
In view of the above it may be concluded that design and specifications of sprinkler systems should aim at reducing costs. This can be achieved through the adoption of appropriate design procedures and systems which utilize locally produced components as much as possible. Additionally the import of sprinkler kits for local assembly would provide the added advantage of improved service on repairs in addition to cost reduction.
In the dambo irrigation at Choma, farmers are using open, hand-dug wells and watering the crops with cans and buckets. In another dambo irrigation at Kanchele in the Kaloma district, farmers installed a treadle pump to lift water from the 2.5 m diameter open dug wells.
The Kasisi Mission just outside Lusaka produces locally, a "treadle" pump which costs about US $ 153 and the cost is one of the reasons that the sale may be limited. There are individual treadles at Kafue, Nanga, Kalomo and other areas. FAO under its Food for Security programme is in the process of installing 20-30 of the Asian version of the treadle pump in Kafue, Kalomo, Chibombo and Mkushi.
Rope and washer
Kasisi made 15 rope and washer pumps for FAO. These pumps were distributed but the performance is not known.
First, the technology for various types of pumps exists within limited circles. Secondly, the prices are excessively high and unaffordable by almost all poor farmers individually. Thirdly, there seems to be little coordination or sharing of information by interested groups. No one is disseminating information nationally or regionally. Lastly, at the moment no one has a programme or even seems to understand that the marketing of the pumps is just as important as manufacturing them. All interested parties see pumps as part of a larger agricultural, health or irrigation scheme and hence have a very limited view. Pumps are only of interest in as much as they fit into overall and wider plans.
Small earthen dams/tanks
In the Nkandabwe irrigation scheme in Choma district, water is stored in a reservoir which is an abandoned coal mine. The water is released through a sluice and conveyed through a lined canal. Eighty-eight farmers each with an area of 0.2 ha share the water. Major crops grown are vegetables and maize.
It is estimated that dambos comprise 1.3 million ha of land in the country, of which 0.26 million ha are in communal areas. It is also estimated that about 20 000 ha of these dambo lands are cultivated with food crops such as maize and vegetables being the major crops. Many dambos have dried up over years due to degradation of the upper catchments. The water table is comparatively deep and in locations such as the periphery of the dambos where the water table is shallow, community based irrigation is practised using manual pumps.
Various types of manual pumps exist. The most common is the locally developed "bush pump" which is a deep-set pump. Treadle pumps are known, but they are not being marketed or manufactured on a continuous basis. Despite this there may be a place for deep-set pumps and probably a real possibility of drip irrigation. The bush pump costs US$ 1 000-1 500 according to local people in the field. The Asian deep-set could be considerably cheaper and provide the same capacity. To raise the groundwater table in the dambos and to prevent soil erosion, small earthen dams or tanks can be constructed across the streams to store the runoff water. This will help sustain smallholder irrigation.
Communal surface irrigation scheme
There are about 178 Government-developed communal and resettlement smallholder schemes. The Mushandike resettlement irrigation scheme has been operating since 1986-87. The scheme is managed both by Agritex and the community. Lined main canals are used to deliver water to the fields by surface methods. As the distance between the dam and irrigated area is 32 km, the cost of the canals is high. About 417 farmers irrigate about 620 ha. Each farmer owns 1.5 ha of land distributed in three blocks at the rate of 0.5 ha/person in each block. Major crops grown are maize, cotton, wheat and beans. Farmers pay operation and maintenance charges of $14.5/ha/year to the Government.
Sprinkler irrigation scheme
The Hema Mavhaire community sprinkler irrigation scheme in the Midlands has been in operation since 1992 and is managed by the community. Water is pumped from the nearby dam using electric pumpsets. About 90 farmers own 90 ha at the rate of 1 ha/person. The drag hose sprinkler method is used to irrigate the crops. Groundnuts, maize and beans were grown during 1995-96. Farmers reported that they are paying about $ 14.5/ha/year as operation and maintenance charges to the Government. Even though, the electricity charges were not paid for earlier crop periods, they have since expressed their willingness to pay the charges.
Farmers reported that siltation is occurring in the dam due to catchment degradation, as soil erosion is the major problem. Farmers expressed fear that the storage may be reduced in due course. They are ready to invest in catchment management activities as such measures will ensure a sustainable water supply in the dam.
Irrigation by collector wells
The concept of collector wells has only been recently introduced in the country. Initially, the ODA made efforts to construct a few collector wells. For example, the collector wells in Muzondidya village and Chiredzi research station are about 2 m in diameter and about 18 m deep in both cases. Two horizontal boreholes at a length of 20 m are made at the bottom of the well. In one well, two hand pumps are fitted to lift the water which is used both for drinking and garden irrigation by the rural community. About 34 farmers irrigate approximately 0.3 ha using buckets. The other well is used to irrigate about 1 ha on the research station. The cost of the collector well will be about $ 8 000 - 9 000 per well including pumps. Since the wells are used also for rural drinking water supply, the water use for irrigation will be enhanced if low-cost drip or sprinkler methods are adopted.
Small earth dam/tanks
Another irrigation technology is to store rainwater behind an earthen dam/bund and use it for irrigation at appropriate locations. This dam can also help recharge the groundwater which can be used for irrigation. The potential for this technology is high due to the presence of undulating terrain in the country.