As we approach the next century, more than 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. This paper reports on a study to project water supply and demand for 118 countries over the 1990-2025 period. The nature and geographic focus of growing water scarcity are identified. In the semi-arid regions of Asia and the Middle East, which include some of the major breadbaskets of the world, the ground water table is falling at an alarming rate. There is an urgent need to focus the attention of both professionals and policy makers on the problems of ground water depletion, which must be seen as the major threat to food security in the coming century.