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1. Introduction

Although enough food is being produced to feed the world’s population, there are still some 840 million undernourished people in the world, 799 million of whom live in developing countries (FAO, 2002a). This situation led the World Food Summit in 1996 to set a goal of halving the number of hungry people by 2015. The recent FAO State of Food Insecurity in the World Report concludes that progress towards this goal has slowed to almost zero (Figure 1). The data indicate that the number of hungry people has decreased by 2.5 million/year since 1992. If this trend continues at the current pace, the World Summit’s goal will be achieved more than 100 years late. To reach the goal by 2015, the annual decrease in the number of hungry people would have rise tenfold to 24 million. As Jacques Diouf, FAO Director General, says in the foreword to the 2002 State of Food Insecurity in the World Report, the cost of inaction is prohibitive; the cost of progress is both calculable and affordable.

Figure 1 The undernourished in the developing world: comparisons with the World Food Summit target

Source: FAO, 2002a

Closer examination of the data reveals that the small global gains are the result of rapid progress in a few large countries. China has reduced the number of undernourished people by 74 million people since the benchmark period of 1990-92. Indonesia, Viet Nam, Thailand, Nigeria, Ghana and Peru have all achieved reductions of more than 3 million, helping to offset an increase of 96 million in 47 countries where progress has stalled. If China and the other six countries are set aside, the number of hungry people in the rest of the developing world has increased by more than 80 million since the benchmark period. Although in many countries the proportion of hungry people has decreased, the actual numbers have increased because of population growth. For example, the number of undernourished people has increased by 18 million in India although the proportion has fallen from 25 to 24 percent.

Sub-Saharan Africa continues to have the highest prevalence of undernourishment and it also has the largest increase in the number of hungry people. However, there are large differences between African countries. The Central Africa subregion is in the most critical situation: the number of hungry people in the Democratic Republic of the Congo has tripled following the country’s collapse into warfare. On the other hand, the percentages and the numbers of undernourished people have declined most in West Africa. There have also been improvements in the situations in Southeast Asia and South America. The situation in Central America, the Near East and East Asia (excluding China) gives reason for concern as both the percentages and the numbers of undernourished people are increasing (FAO, 2002a).

For some time, experts have debated the capacity of the world’s agricultural systems to produce enough food for an ever-larger population. FAO has maintained consistently that, on the basis of availability of suitable land for rainfed and irrigated agriculture, enough food could be produced for the much larger human population predicted for 30 years from now. It appears that in an increasing number of regions, land and water could be the main factors limiting food production. The objective of this paper is to examine present and future water availability for food production at a time of increasing demands for water from other users, e.g. for sanitation and drinking-water in mega-cities and for industry. Farmers not only have to compete for water with urban residents and industries, but increasingly also with the environment as its services in sustaining good-quality water supplies through wetlands and groundwater aquifers become more widely recognized. The latter demand has not yet been quantified accurately.

Any attempt to determine whether there will be enough water to grow food for the almost 8 000 million people expected to inhabit the Earth by 2025 requires an understanding of the link between water availability and food production. Once this relationship is understood, decision-makers can perceive more clearly the consequences of the choices they make in order to balance water supply and demand. There have been more than 20 estimates of future world food security in the past 50 years, based on various, increasingly complex, computer models. FAO and the United States Department of Agriculture (USDA) have produced regular forecasts, but others, such as the Organisation for Economic Co-operation and Development (OECD), the International Food Policy Research Institute (IFPRI), and the International Institute of Applied Systems Analysis (IIASA) have also published their own forecasts. Others, such as the International Water Management Institute (IWMI), have made projections of future water-use scenarios. Whatever model one may adopt, it is clear that agricultural water use will still increase, albeit at a diminushing rate, if the growing world population needs are to be met.

Plane 1 Irrigation of a potato fields (Cape Verde)


During the last half of the 20th century, significant productivity gains in rainfed and irrigated agriculture have kept world hunger at bay. Improved water management and conservation in rainfed and irrigated agriculture have been instrumental in achieving these gains. Agricultural water management has underpinned the intensification attributable to fertilizer application and the use of high yield varieties. In this sense, water productivity alone is estimated to have increased 100 percent over the past 40 years.

In the future, agriculture will have to respond to changing patterns of demand for food and combat food insecurity and poverty amongst marginalized communities. In so doing, it will have to compete for scarce water with other users and reduce pressure on the water environment. Water will be the key agent in this drive to raise and sustain agricultural production to meet these multiple demands. Agriculture policies and investments will therefore need to become much more strategic. They will have to unlock the potential of agricultural water management practices to raise productivity, spread equitable access to water, and conserve the natural productivity of the water resource base. Some of the key issues related to these new challenges are discussed in details in this report.

Chapter 2 discusses the present and future availability of water resources. It draws on the outcomes of several of the computer models that predict future water use in agriculture. Rainwater, canal water and pumped groundwater are all essential for food production. Chapter 2 discusses their differing roles in poverty alleviation and rural development. They also differ from one another in the challenges they present when they are used in efforts to increase water productivity in agriculture, defined as crop yield per unit of water consumed.

Chapter 3 addresses the issues arising from the desire to enhance water productivity in agriculture. It explains that water productivity values depend on the scale at which they are assessed. It is widely assumed that reductions in seepage and percolation losses from fields can increase water productivity in many irrigation systems. However, where these so-called losses are pumped up from the groundwater and used for irrigation somewhere else, what is lost at one location is a water source elsewhere. This is illustrated by the difference between the perceived field irrigation efficiency (i.e. the fraction of water extracted for irrigation that reaches the fields) in Egypt’s irrigation systems of about 40 percent and the calculated irrigation efficiency for the entire Nile Basin of almost 90 percent. The difference results from the widespread reuse of drainage water (Keller and Keller, 1995).

Chapter 4 examines risk management in agriculture. It discusses why farmers prefer low-input farming practices that result in low but stable production. It examines the incentives, especially with respect to water management, that can be provided to make them accept more risk but also produce more. It finds that part of the answer for irrigated agriculture lies in the provision of better management services leading to greater reliability of the water supply. In rainfed agriculture, part of the solution may come from the introduction of techniques that result in a more favourable partition between the amount of rain stored in the rootzone and that which runs off into drains.

Chapter 5 discusses approaches to reduce the adverse environmental impacts of water resource development. There used to be more than 1.6 million ha of wetlands in California, the United States of America, but more than 90 percent of these have now been drained and converted to others uses (Van Schilfgaarde, 1990). Similar statistics could probably be found for other countries and regions that are irrigated intensively. The development of water resources has considerably reduced the abundance of streams, riparian vegetation and wetlands suited for wildlife habitat. It is only recently that the world has realized that wetlands provide valuable ‘ecosystem services’, such as recharging groundwater, attenuating floods, and buffering sediment and pollution.

Chapter 6 focuses on the modernization of irrigation water management. In the past 30-40 years, many irrigation systems in developing countries have been rehabilitated. This rehabilitation was usually necessitated by years of neglect (often caused by lack of funds) and intended to restore the irrigation system to its original design. The impact of such rehabilitation work was often short lived. Where the management is incapable of operating and maintaining a system to high standards, restoring its physical infrastructure will not lead to production improvements. The converse is also true: good management cannot obtain good results from a poorly designed or maintained system. Moreover, what may have been appropriate in the past may not be suitable for today’s water service demands and expectations. Thus, modernization encompasses improving the physical infrastructure and institutional setup so that the modernized system can function in a more service-oriented manner that is suitable for current and future cropping patterns and irrigation practices.

FAO (1997) defines irrigation modernization as a process of technical and managerial upgrading (as opposed to mere rehabilitation) of irrigation systems combined with institutional reforms, with the objective to improve resource utilization (labour, water, economic, environmental) and water delivery service to farmers.

The final chapter of this paper highlights the choices that governments and funding agents face in trying to ensure that water scarcity will not curtail the world’s capability to produce enough food for the future global population.

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