According to the World Water Assessment Program, today, half the world’s population lives in urban centers, compared to less than 15 percent in 1900. The world’s urban areas present unique water management challenges, but they also provide some opportunities.
When millions of people live in close proximity, localized sources are not always able to match high-volume water demand. Good management of regional watersheds to provide an adequate water supply can be quite difficult—technically and politically—in rapidly urbanizing areas.
Many of the world cities are growing exponentially and unchecked development is spawning slum neighborhoods that lack water infrastructures. Where proper sanitation is lacking, untreated human waste is disposed of in open ditches, streams, and rivers. These waste products are a serious health hazard, and they dramatically increase the spread of waterborne and sanitation-related diseases like diarrhea and parasitic infections.
The poor bear the brunt of these burdens. Some 180 million slum dwellers worldwide lack access to clean drinking water. In areas poorly served with water and sanitation, the child mortality rate is many times higher than in areas with adequate water and sanitation services.
Municipal efforts are often focused on developing community toilet facilities and setting up waste treatment infrastructure, as well as making provisions for clean water supply in neighborhoods where it is lacking. In the meantime, those without clean water must still drink. Typically they turn to unsafe water, which creates a host of health problems, or pay fees to bottled, trucked, or other private water sellers—at costs many times higher than those of city residents who benefit from piped-water infrastructure.
Yet, many urban piped-water systems present their own problems. Aging or ill-maintained pipes often result in water loss—more than 25 percent in Mexico City, for example—an unacceptable waste of an often-scarce resource. And, if pressures in these leaky pipes are low enough, they may be contaminated by inflow of sewage or other untreated water.
These high population concentrations provide more than just challenges. They also offer an opportunity to more efficiently provide clean, treated water to many millions of people who might otherwise be located in difficult-to-serve locations. Proper sanitation systems, likewise, may be easier to create and maintain when the distances involved are not prohibitive. For these reasons, urban dwellers in much of the developing world are often more likely to have access to clean water and proper sanitation services than their rural counterparts.