In the mid 1970s, the world's stock of irrigated land was being increased by about 2.5 percent each year. By 1989, there were some 233 million hectares of irrigated land in the world; 73 percent is in developing countries, representing 21 percent of all the cropped land in these countries. East and South Asia, with some 131 million ha, have by far the largest area under irrigation. About 22 million ha of irrigated land are located in West Asia and North Africa, 16 million ha in Latin America and about 3.5 million ha in sub-Saharan Africa.
A few countries dominate in irrigation. China and India together possess about half of the developing world's irrigated land. There are others, notably Egypt and Pakistan, whose aridity makes it impossible to support more than a small fraction of their existing populations without irrigation.
In the arid regions of West Asia and North Africa, new irrigation development has been very limited in recent years, essentially because the accessible water sources have already been tapped and the remaining sources are expensive to develop. In subSaharan Africa, a contrary situation exists: the irrigated agriculture sector is modest, with a focus on commercial nonfood crops such as cotton and tobacco, because in many countries rainfed production potential is still abundant.
The impact of irrigation upon rural poverty is a complex and difficult subject as the distribution of gains from irrigation development depends on a host of factors which go far beyond the primary cropproduction activity: crop processing industries are stimulated; higher farm incomes mean more household expenditure, which stimulate retail trade; service industries like transportation get more business; and so on. Further, irrigation development affects almost all sectors of the economy. Some studies have quantified these secondary benefits as roughly equal to the primary benefits of crop output.
At the local level, gains from irrigation for the rural poor include increased employment opportunities and incomes, security against impoverishment and improvements in the quality of life. There is a considerable amount of empirical evidence which shows that, when wellmanaged, irrigated agriculture generates employment and higher wages for marginal farmers and landless laborers.
An important contribution of irrigation to the quality of rural life results from improvements to rural water supply and sanitation. The provision of irrigation facilities allows rural people to have easy access to water for domestic needs. This particularly benefits women who, with few exceptions, carry out the arduous task of fetching and transporting household water, often over long distances.
The benefits of irrigation extend beyond the rural poor to the urban poor, by reducing the pressure on urban employment and infrastructure and by increasing the real wages of urban laborers who spend the greatest proportion of their incomes on food. Thus, the best indicators of overall impact may be those which also take such urban benefits into account.
That the spread of irrigation has been a major contributor to the remarkable increases in agricultural output in the tropics is indisputable. And yet there is widespread dissatisfaction with the performance of irrigation projects. This is true whether performance is measured in terms of achieving planned targets or in terms of the production potential created by physical works. Sub-optimal performance can be observed in irrigation systems of all types and sizes, from the small farmermanaged systems in the hills of Nepal to the giant canal systems of India and Pakistan.
In most schemes around the developing world, more water is delivered per unit area than is required, leading to low irrigation efficiencies. According to a recent report, irrigation efficiencies are as low as 2025 percent in Java, the Philippines and Thailand, and in Pakistan it is about 50 percent (Asian Development Bank, 1991). In many irrigation systems, the actual irrigated area is much less than the area commanded. Water deliveries rarely correspond in quantity and timing to crop requirements, resulting in low cropping intensities and low productivity.
Sharp inequities in water supplies to farmers in the head reaches of the irrigation system and those located downstream are another manifestation of poor performance in many irrigation systems.
Lack of maintenance has caused many systems to fall into disrepair, further inhibiting performance. Over time, distribution channels fill up with silt, increasing the likelihood of breaching, damaging outlets and leading to salt buildup in the soil. In China, for example, more than 930,000 ha of irrigated farmland have become unproductive since 1980, an average loss of some 116,000 ha per year. Worldwide, an estimated 150 million ha-about 65 percent of the world's total irrigated area-need some form of upgrading to remain productive. These trends underlay major concerns about the sustainability of irrigation.
Fresh water available for irrigation is decreasing in many parts of the world. The future will be characterized by growing scarcities of water. With rapid population growth and urbanization, the demand for water for domestic needs, industry, and other uses is rapidly increasing, setting the stage for intense competition between cities and farms.
Irrigation can have negative effects on the physical environment. The principal environmental risks associated with irrigation come from weaknesses in the control of the quality and quantity of effluent water. Excessive irrigation and poor drainage raise the water table, bring soluble salts to the surface and may adversely affect yields on irrigated land. Data on land degradation due to salinization and water logging are limited. It has been estimated that about 24 percent of the irrigated area worldwide is affected by salinization, though many observers regard this estimate as too high. Most of this area is in the top five irrigators of the world: India, Pakistan, China, the United States and the states of the former Soviet Union.
Most irrigation systems are created for a primary public health objective: to improve human nutrition. Their success in attaining this objective is sometimes reduced by negative impacts on health. These are of two main types. Diseases borne by waterrelated vectors, especially mosquitoes and snails, may increase because the irrigated environment supports much greater populations of these vectors. Secondly, water provided for irrigation is often used for many other purposes: drinking, cooking, washing, and recreation. Gastroenteric and other diseases are often transmitted among human populations through these uses.
The need for irrigation management research and outreach to find solutions to these problems at the international level is far greater now than it was when IIMI was founded in 1984. Managementoriented research institutes always find it harder to demonstrate impact than technologyoriented ones. Often institutional in nature - such as a change in the views of directors and policy-makers - IIMI's achievements are difficult to quantify. Nevertheless, the evidence of identifiable changes in operations and policies is being produced each year. IIMI's impact on national policies is most evident in the countries where it has its largest and longest established programs Pakistan and Sri Lanka.
In Pakistan, the Institute's pioneering research on the problem of salinization has led to action at the highest levels of government. Following an exchange of letters with IIMI, the Prime Minister established an interministerial committee to decide what should be done to combat salinization and ensure action by relevant agencies. In Sri Lanka, the country is now firmly committed to a participatory approach to irrigation management and IIMI is continuing its longterm assistance in developing, evaluating and refining this policy. On a major new irrigation scheme, IIMI has helped create a framework for deciding on the sharing of water under conditions of scarcity fraught with the risk of conflict.
In other countries, IIMI's approach to irrigation management is receiving attention from managers and policy-makers. In Nepal, the Government has invited IIMI to participate in formulating a 25year National Agricultural Perspective Plan.
In Sudan, IIMI recently completed important studies on the Gezira Scheme, where a major overhaul of tertiary level management is now under way. In Nigeria, the successful development of water users' associations in a large irrigation system has led to rapid and tangible improvements in the physical condition of water courses and to the more widespread adoption of the approach used to develop the associations.
Following are four examples of project activities that IIMI will be implementing in the coming year, one of which is already under way. These projects, based in Middle East/North Africa, subSaharan Africa, Latin America and Asia, illustrate IIMI's interest in enhancing the capacity of public and private groups to manage irrigation, jointly and in the context of privatization; mitigating negative impacts of irrigation on the environment; and encouraging participatory management of land and water resources.
IIMI will be working with the Ministry of Public Works and Water Resources of the Government of Egypt on a study aimed at increasing the productivity of water use for agriculture. This study is linked to an ongoing USAID Irrigation Management Systems (IMS) Project. IMS activities have been designed to provide a package of physical, technological and managerial infrastructure. Important research has also been carried out on the issue of cost recovery for operation and maintenance (O&M) and rehabilitation, with special reference to agricultural water users and their capacity and willingness to pay for O&M and capital improvement. IIMI's proposed study will focus on two main areas: potential for improved irrigation operations, and possible alternative cost-recovery mechanisms. Project outputs will be: (1) an implementation plan for overcoming irrigation operations constraints; and (2) a broad framework for the management of water and a cost-recovery program for users.
Through a twoyear collaborative activity in the Andean region of Latin America, IIMI will study the irrigation management transfer phenomenon from both the public and private perspectives, tracing its interrelationship with the environmental degradation of the watershed sources of irrigation water. The study will help test two assumptions: that privatization leads to improved management and increased productivity, and that improved resource management can help to overcome watershed degradation, thus reversing the decline in irrigation investment. Outputs of the proposed program will include guidelines for the creation of better managed minidistricts so as to minimize degradation of watershed areas and adverse impacts on downstream water quality and quantity.
Over the next five years, IIMI will assist Pakistani organizations in adopting management changes to mitigate the negative effects of salinity and associated waterlogging, which include reduced food availability and income at the household level and depressed agricultural productivity at the national level. Pakistan has traditionally focused on technological solutions at the expense of expanding institutional capacity. The project seeks to redress this balance through a series of province-level studies designed to yield specific management recommendations. Disadvantaged irrigators-such as tailend farmers-who not only get less water less frequently than their crops require, but also have lower incomes, fewer benefits in relation to labor costs, weaker influence in their communities and less access to services in general than farmers at the head end - are a special project target.
The first phase of a sixyear project to increase the share of users' control over land and water resources in selected watersheds was recently begun in Sri Lanka. The project facilitates stateuser partnerships that contribute to intensified and sustainable agricultural production while conserving the physical, biological and social environments. With IIMI facilitation, the inhabitants of two watersheds are working with the government to prepare a detailed improved land and water management plan. Using known technologies, the plan will augment the resource base while improving production through management changes. It will also strengthen user groups so that they can experiment with innovative "production and protection" methods of natural resource management.
The current global population of 5.5 billion will nearly double to 10 billion by the year 2050; the demand for food is expected to increase by 150 percent over the next 30 years. Where will the additional food come from? And where will people find the additional income to buy it? An important answer to both questions must come from irrigated agriculture. To meet the world's future food demands, output from this sector will need to increase by 3.5 to 4 percent per year over the next quarter century. In many countries, where the extent of irrigation is substantially greater than 20 percent, more than half of the total food output depends on irrigation. At present about 60 percent of rice and 40 percent of wheat production in developing countries is on irrigated land.
Asia alone accounts for about 90 percent of global production and consumption of rice. This is likely to continue into the next century. With the total amount of land devoted to rice, cultivation is unlikely to increase over the next several decades. Most of the additional demand for rice (at the rate of 2.4 percent per year) must therefore be met from intensified irrigated agriculture. In the Middle East and North Africa it is expected that imports will meet some of the additional demand, but most of the requirement will have to come from irrigated lands. In subSaharan Africa, irrigation is now a small sector, but there is much potential for extension of irrigated agriculture. Because of chronic food shortages in the region, increasing production is vital.
Over the next several years, it is imperative that irrigated agriculture achieve dramatic improvements in management performance. Successful irrigation of the future will: (a) permit much higher levels of agricultural productivity, (b) be responsive to more diversified and dynamic crop markets, (c) stimulate more profitable irrigated agriculture for many rural poor,(d) substantially improve water use efficiency, and (e) support the sustainable use of scarce land, biomass and water resources.
These ambitious but necessary improvements in the performance of irrigated agriculture can be achieved during the 1990s through a combination of applying known technologies and management principles within a supportive policy environment, research to identify and adapt new solutions, and dissemination and application of these research results. The most important requirements are, therefore, appropriate and effective policies, organizations, human resources, and technologies. These requirements apply to the broader agriculture and water resources sectors, with special requirements to address problems and issues unique to irrigated agriculture.