Water scarcity in the twenty-first century

Based on a recent study by the International Water Management Institute (IWMI), it is estimated that nearly 1.4 billion people, amounting to a quarter of the world"s population, or a third of the population in developing countries, live in regions that will experience severe water scarcity within the first quarter of the next century. Slightly more than one billion people live in arid regions that will face absolute water scarcity by 2025. These regions do not have sufficient water resources to maintain 1990 levels of per capita food production from irrigated agriculture, even at high levels of irrigation efficiency, and also meet reasonable water needs for domestic, industrial, and environmental purposes by 2025. People in these regions will accordingly have to reduce water use in agriculture and transfer it to other sectors, reducing domestic food production and importing more food. About 348 million more people face severe economic water scarcity. They live in regions where the potential water resources are sufficient to meet reasonable water needs by 2025, but they will have to embark on massive water development projects, at enormous cost and possibly severe environmental damage, to achieve this objective. This paper briefly reviews and interprets these estimates and examines the kinds of research and information needs necessary to manage water resources more efficiently and productively in the 21st century. The paper is divided into two parts. Part I describes the IWMI study, which projected water supply and demand for 118 countries over the period 1990 to 2025. Part II shows how all the issues of water scarcity are concentrated in what appears to be the single greatest problem of water resources in the next century, the problem of groundwater depletion and pollution. Of particular concern is the overlooked problem of an alarming decline in the groundwater table in the semi-arid regions of Asia and the Middle East. These regions contain some of the major bread baskets of the world such as the Punjab and the North China Plane.