What Goes Down the Drain Must Come Up.

• Position: Brief Article

Cities do not exist without water. People have known this since the world's earliest civilizations arose in the valleys of great rivers several thousand years ago. The Roman architect Vitruvius wrote in the first century B.C., for instance, that finding water was the first step in planning a new city.

Yet many cities are hastening the demise of their water supplies by failing to protect local sources of fresh water. This is particularly shortsighted because the urban population is expanding rapidly. In just five years, between 1990 and 1995, cities of the developing world grew by 263 million people--the equivalent of another Los Angeles or Shanghai forming every three months. The United Nations projects that half of the world will be living in cities by 2006.

People have long dumped household and industrial wastes into the very rivers and streams that supply their drinking water. At the end of an 1828 poem on Cologne, Samuel Taylor Coleridge wrote:

The River Rhine it is well known, Doth wash your city of Cologne; But tell me, Nymphes, what power divine Shall henceforth wash the River Rhine?

Today, an estimated 90 percent of the developing world's sewage is still released directly into surface water courses, where it is joined by industrial waste. Thus, cities have looked to tap groundwater where they can, because it is protected from surface pollutants by layers of soil and rock. In fact, the World Health Organization now advises local authorities that water from rivers and streams should "be used only when underground water is inadequate or not available."

But, as Payal Sampat reveals in this issue (see "Groundwater Shock," page 10), pollution and...