The overall government policy in these African countries is to promote social and economic development through irrigated agriculture which is sustainable over time, economically justified, financially viable, socially acceptable and technically sound, without causing unacceptable impacts on the environment. Irrigation development programmes must also benefit as many households as possible and in particular those that belong to the most vulnerable groups of the rural community. Irrigation development, particularly small-scale irrigation, will be an important component of a diversification and expansion strategy to strengthen food security for the future. There is a need to identify crops and irrigation techniques which will give higher returns to irrigation water and overall investment. The best and most economical uses of water for irrigation are essential to any strategy of irrigation development. The following are the conclusions and the recommendations which may be relevant to the four countries covered.
Diversion schemes demand more area but the efficiency is less. Hence, there is an urgent need to rehabilitate the schemes by restructuring weirs and lining the canals with prefabricated slabs. Treadle pumps can be introduced where the water table is within 6-7 m in several locations and particularly where the diversion schemes are not benefiting the smallholders. Low-pressure and low-cost sprinklers perform well in the hill areas. Therefore, these systems can be introduced in the hill diversion schemes. The country's undulating terrain is very suitable for small earth dams (tanks) to provide supplemental irrigation in the wet season and direct irrigation in the dry season. Since the duration of the water supply in many schemes is not adequate to cover the entire season, shallow tube wells or open wells can be constructed to raise nurseries before the rains and to irrigate the crops when the canals dry.
The extent of dambos with potential for irrigation development warrants the introduction of a number of manual irrigation pumps and their local manufacture. The combination of low-cost drip systems with manual pumps, should be tried and demonstrated. The current practice of hand dug shallow open wells should be encouraged. Alternative low-cost drilling techniques such as slurry sludge, and hand auger drilling should be promoted. The country's undulating terrain is very suitable for small earth dams both for direct irrigation and the recharge of the groundwater to be used for irrigation. As such this technology should be promoted. The transfer of government schemes to community management after improvement should incorporate the feasibility of introducing the lining of the field canals. The encouraging results from the first few sprinkler systems introduced in community operated and managed irrigation schemes should be continuously monitored. Minor changes in the design of future sprinkler schemes should be introduced to reduce costs and provide individual plots for every family. While it is appreciated that the current small market for sprinklers does not justify the manufacturing of this equipment, local assembly of sprinklers is recommended, as it would reduce their cost and improve the availability of spares and service for their maintenance. Technical assistance for on-the-job training of the DOI staff in planning, designing and supervision of small-scale irrigation schemes is also recommended.
The extent of dambos with potential for irrigation development warrants the introduction of locally manufactured manual irrigation pumps. Low cost well drilling technologies should be introduced and a combination of low-cost drip system with manual pumps and pitcher irrigation should be tried and demonstrated. The undulating terrain of the country is suitable for small earthen dams both for direct irrigation and for recharging the groundwater for irrigation. This technology should be promoted and implemented.
Transfer of government schemes to the community after improvement should incorporate the feasibility of introducing the lining of the field canals, water control and regulating structures.
Technical assistance for on-the-job training of the staff of the irrigation section in planning, designing and supervision of the small-scale structures is also recommended. Certain regions have access to electricity, thus electric powered pumps can be introduced, as groundwater is easily available. The pumps could be imported at a comparatively low cost from Asian countries.
As a result of the encouraging results from the few smallholder drag-hose sprinkler irrigation systems in the community operated and managed projects, the introduction of many such schemes in the future mainly to save water and increase crop production, is recommended. On individual smallholder farms, introduction of low-cost drip irrigation and low-cost low-pressure sprinkler irrigation systems will improve water use efficiency and crop productivity.
Since shallow alluvial aquifers are found only in selected provinces, manual pumps can be introduced to exploit them.
Since collector wells were recently introduced and serve both rural water supply and community garden water requirements, the expansion of such a high-cost investment for irrigation should be carefully analysed. Small check dams or percolation ponds should be constructed in the catchment areas mainly to reduce soil erosion and siltation in the downstream dams. Small earth dams or irrigation tanks should be constructed to store the rainfall run-off for irrigation and for recharging the groundwater. The inadequate rainfall and undulating terrain in the country will facilitate such structures.
The cost of the locally manufactured and imported pumps and equipment in the country is comparatively high. It is recommended that the equipment be imported from Asian countries initially and subsequently to encourage joint ventures to manufacture them. Technical assistance for on-the-job training for the staff of the AGRITEX in planning, design, implementation and supervision of the small-scale systems should be provided.
Regarding the economics of irrigation, break-even crop yields indicate the safety margin in irrigated agriculture. Even with price or yield fluctuations (risks) farmers are able to manage the crop production. Viability of different irrigation schemes based on the gross margin justifies the need for irrigation technology transfer in all these countries. In the case of smallholder schemes, besides financial viability, other benefits such as employment generation, improved nutritional standards of people and improved market activities associated with forward and backward linkages are also common. These factors further justify the rationale for smallholder irrigation investment.
A country action programme aimed at various irrigation technologies and the establishment of a national irrigation technology demonstration center is recommended for all the countries.