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Nature Gallery (Global Trends)

Freshwater Contamination

Scarce Drinking Water
Worldwide, more than one billion people lack access to safe drinking water. By the turn of the century an estimated 80 per cent of the Earth’s urban residents may not have adequate potable-water supplies. Only a very small quantity of the Earth’s fresh water—around 0.008 per cent—is currently available for human use. Seventy per cent of that goes to agriculture, 23 per cent to industry, and only 8 per cent to domestic consumption.

At the same time, demand for fresh water is rapidly rising. Agricultural use is expected to increase 17 per cent and industrial demand 60 per cent by the end of the decade. As fresh water becomes more scarce, it is likely to be a source of regional conflict, a situation already occurring in the Middle East.
Freshwater supplies are in decline because of the regular, severe droughts experienced by half of the nations of the world. As a result, growing populations draw down aquifers faster than nature can replenish them, even in temperate countries such as the United States. In coastal cities such as Jakarta, Indonesia, or Lima, Peru, sea water rushes into aquifers to fill the void, contaminating the fresh water that remains. Many underground aquifers are also polluted by agricultural chemicals; clean-up procedures are expensive.

Agricultural irrigation, a boon to many countries that would otherwise not be able to grow adequate food crops, can also contaminate water supplies if used excessively. By leaching salts from the soil into surface water, excessive irrigation renders surface water—that in rivers, streams, and lakes—useless for further agricultural or domestic use.

Pollution
Industrial pollution of groundwater remains a serious problem in most developed nations. Toxins leach into soil and groundwater from petrol storage tanks, landfills, and industrial waste sites around the world. In the United States, one in six residents drinks water that contains high levels of lead, a major industrial toxin. Even though the general quality of river water has improved over the past 20 years in most industrialized nations, concentrations of heavy metals such as lead remain unacceptably high.

Another major cause of freshwater pollution is sewage dumping. In developing countries, 95 per cent of human waste water is discharged untreated into nearby rivers that are frequently also sources of drinking water. People who drink such water are more likely to contract water-borne infectious diseases, the foremost health problem in the developing world. Sewage pollution also kills freshwater fish, an important food source, and leads to deleterious algae blooms in coastal areas.

Freshwater resource management raises several political and economic dilemmas. For example, rivers and watersheds often cut across national, provincial, and state boundaries, and upriver polluters have little incentive to spend money on protection that may only benefit their downstream neighbours. Developing nations often cannot afford to build expensive sewage-treatment plants like those found in most developed nations. Less expensive systems are being tried, however, including some that use wetlands and marshes to purify waste water naturally. Other possible responses to the increasing global demand for fresh water are under study by environmental organizations and governments around the world.