New FAO publication aims to bring small-scale irrigation to farmers in sub-Saharan Africa
Irrigation is a key tool for agricultural intensification. Although only 16 percent of the world's fields are irrigated, they yield 36 percent of global harvests. In developing countries, irrigation increases yields of most crops by 100 to 400 percent. Despite this, some of the world's most needy farmers are still unable to water their land effectively.
"Small-scale irrigation for arid zones: Principles and options" promotes HELPFUL (High-frequency, Efficient, Low-volume, Partial-area, Farm-Unit, Low-cost) irrigation techniques. Hillel, who has a lifetime's experience of irrigation, points out that "Elaborate and expensive systems ... imported and installed in the grand hope of achieving instant modernization, typically fail for lack of expert maintenance and spare parts. Such installations can quickly become white elephants - idle monuments to hasty 'progress' relying on ill-adapted technology."
When they do work, poorly managed irrigation systems cause a range of environmental problems. Rising water tables, caused by excessive applications, leakage from drainage channels and inadequate drainage, lead to salinization and waterlogging, which reduces crop yields. Conversely, overpumping of groundwater depletes supplies and threatens long-term viability of the irrigation schemes and the crop yields they support.
"It is the universal fallacy of humans to assume that if a little of something is good, then more must be better. In irrigation (as indeed in many other activities), just enough is best." says Hillel.
The irrigation techniques described in Hillel's paper are the result of combining revolutionary developments that have taken place in recent decades in the science of irrigation with traditional technologies used successfully for centuries. It is now possible to maintain nearly optimal soil moisture conditions - thus eliminating problems of waterlogging and salinization, as well as saving water - throughout the growing season, responding continually to varying weather and developing stages of crop growth.
Although these methods are applied on a large scale in industrial countries, they need not depend on expensive manufactured equipment and high-energy inputs. Hillel explains how simple jars of porous clay, perforated plastic pipes and other low-cost equipment can be used to regulate water flow to crops (see Box below).
Hillel's paper advocates development "based on the best principles of efficient irrigation, insofar as possible using indigenous skills and materials. The best principles of efficient irrigation should be disseminated, not necessarily the most elaborate machinery." It is written for decision-makers and the general public. Believing that "ready-made prescriptions tend to be specific and inflexible, and hence rarely apply as new problems arise in changing circumstances", Hillel's aim has been to explain the principles of modern irrigation so that farmers and their advisors will be able to modify their approaches and actions when new conditions arise.
15 July 1997
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