Thirty years ago, extensive use of fertilizer and expansion of irrigation together with high-yielding food crops were the critical factors in preventing global famine. The drop in rate of yield increase of many grains may be an indication that these instruments have reached their effective limits. Most analysts believe future increases in food supplies will come mainly from improved production, since the natural resource base will not support either significant expansion of farmlands or more extensive irrigation (Shah and Strong, 2000). One option for improving the productivity of irrigated agriculture - and maybe the most important one - is to improve the water distribution service to individual or groups of farmers.
"The most important of all functions of irrigation projects is to ensure that water is efficiently and fairly distributed. It is only if the main water distribution system is well operated that many other important objectives can be satisfactorily realized; and it is only then that high returns can be obtained from agricultural extension advice and the increased application of other complementary inputs" (Bottrall, 1981)."
Although expressed 20 years ago, the donors and government agencies have not yet translated this statement into effective action for many surface irrigation systems. By contrast, some entrepreneurial farmers have taken the matter in hand, where feasible, by tapping groundwater, building small terminal reservoirs and capturing drained water. Where water supply becomes reliable, farmers invest in water saving techniques which have influenced the choice of crop, amount of fertilizer applied and a host of other agronomic practices depending on market conditions. However, a large majority of farmers cannot do so because of too deep or poor quality groundwater, or because of lack of land for building farm reservoirs. The most important option to increase productivity is to improve the service from delivery systems, which in turn will encourage improved water use at farm level. Improved management at both levels if necessary to achieve the higher water productivity from canal systems. Achieving that objective would require a number of changes.
First, the irrigation community at large, including agencies, consulting firms and research institutes would have to be convinced that both deficiencies in technology and management are the causes of poor performance of irrigation.
Second, donors may have to change their criteria for the economic feasibility of irrigation projects, by using shadow commodity prices. At todays low prices it does not pay to invest in improvements in irrigation infrastructure. Because of the long gestation period, failure to invest now could exacerbate the problem of water scarcity, threaten food security, and push prices of agricultural commodities up to unacceptable levels.
Third, engineers and planners need robust information on the links between design, maintenance, spending, performance, whole life cost and sustainability. They would have to better understand the process of modernization of large surface systems.
Fourth, a massive effort is needed to increase awareness of the deficiencies of outdated designs and the potential of modern technologies for water control and sustainable agriculture.
As stressed above, improving the quality of service in large-scale systems is a prerequisite to the adoption of on-farm modern techniques. However, it is not the only limiting factor. Improving water productivity in large-scale systems through the adoption of water-saving techniques at farm level could be a nearly inextricable task because of financial, operational and technical constraints (box 9).
Box 8: The intricate issue of on-farm modern irrigation in large scale systems
Canal irrigation systems with some elements of modernization are better performing than conventional design systems, such as the manually-operated under-shot gated systems. However, these modern systems may be far from reaching their potential agricultural performance if on-farm management is left behind. For example, water delivery from the irrigation systems in Morocco is organized on a bi-weekly rotational basis, a method that excludes the adoption of water-saving techniques and the cultivation of high value vegetable crops in the absence of farm reservoirs. Furthermore, the land consolidation model adopted in that country since the 1960s is now a serious constraint to the adoption of water-saving techniques since the agricultural policy has shifted from an interventionist to a liberal economy. A land-consolidated block of 30 hectares designed for irrigation on a crop-strip basis is poorly adapted to a rotation between farm plots arranged across the crop strips. Changes in both land management and system operation are needed.
Productivity of the modern large-scale granary systems in Malaysia is limited by the low density of canals (about 12 meters/ha), compelling most farmers to practice field-to-field irrigation. Construction of the missing tertiary and quaternary canals as well as farm roads required for farming mechanization is not economically justified under the present depressed rice prices unless crop yields could nearly double.
The conversion from canal to pipe delivery in existing systems leads to serious operational problems if all the users do not shift from surface to pressurized application. The low flow-high frequency is not compatible with the high flow requirement of surface irrigation. In the Jordan Valley the farmers using basin irrigation are unhappy about the low flow delivery and those using drip irrigation are unhappy about the pressure drop when the first group tamper with the flow-controllers. The water fees are presently far too low to convince all farmers to invest in water-saving techniques.
The increased participation of users in the management of irrigation systems offers a unique opportunity to improve system operation. However, the design of user associations, their size, their level of financial autonomy and responsibilities vis-à-vis government agencies determine the type of activities they can undertake. Partial turnover to farmers will not address problems of operation and maintenance of main canals of most large systems. Farmers have little reason to make turnover work unless they get an improved service from the main system.