The total amount of water withdrawn globally from rivers, underground aquifers and other sources has increased ninefold since 1900 (chart). Water use per person has only doubled in that time, however, and it has even declined slightly in recent years. Despite this positive trend, some experts worry that improvements in water-use efficiency will fail to keep pace with projected population growth. Estimated annual water availability per person in 2025 (map) reveals that at least 40 percent of the world's 7.2 billion people may face serious problems with agriculture, industry or human health if they must rely solely on natural endowments of freshwater. Severe water shortages could also strike particular regions of water-rich countries, such as the U.S. and China.

People's access to water also depends on factors not reflected here, such as political and economic conditions, changing climate patterns and available technology. ---P.H.G.

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