Water is, literally, the source of life on earth. The human body is 70% water. People begin to feel thirst after a loss of only 1% of bodily fluids and risk death if fluid loss nears 10% (73). Human beings can survive for only a few days without freshwater. Yet, in a growing number of places people are withdrawing water from rivers, lakes, and underground sources faster than they can be recharged—"unsustainably mining what was once a renewable resource," as one researcher puts it (1). Currently, 31 countries—mostly in Africa and the Near East face—water stress or water scarcity (65, 69). (For definitions, see glossary.)

Population growth alone will push an estimated 17 more countries, with a projected population of 2.1 billion, into these water-short categories within the next 30 years. By the year 2025, 48 countries, with more than 2.8 billion people—35% of the projected global population in 2025—will be affected by water stress or scarcity (see Chapter 3.2, The Coming Era of Water Stress and Scarcity) (69, 135, 181). Another nine countries, including China and Pakistan, will be approaching water stress.

Beyond the impact of population growth itself, the demand for freshwater has been rising in response to industrial development, increased reliance on irrigated agriculture, massive urbanization, and rising living standards. In this century, while world population has tripled, water withdrawals have increased by over six times (98). Since 1940 annual global water withdrawals have increased by an average of 2.5% to 3% a year compared with annual population growth of 1.5% to 2% (38, 176). In developing countries over the past decade water withdrawals have been increasing by 4% to 8% a year (111).

Moreover, the supply of freshwater available to humanity is shrinking, in effect, because many freshwater resources have become increasingly polluted. In some countries lakes and rivers have become receptacles for a vile assortment of wastes, including untreated or partially treated municipal sewage, toxic industrial effluents, and harmful chemicals leached into surface and ground waters from agricultural activities (114).

Caught between finite and increasingly polluted water supplies on one hand and rapidly rising demand from population growth and development on the other, many developing countries face uneasy choices (33, 85, 114, 215). The lack of freshwater is likely to be one of the major factors limiting economic development in the decades to come, warns the World Bank (165, 164).