Rapidly growing cities, burgeoning industries, and rapidly rising use of chemicals in agriculture have undermined the quality of many rivers, lakes and aquifers. The industrial revolution turned the Thames into a stinking, black health hazard as it ran through London in the late 19th century. Major investments in wastewater treatment and cleaner production have gradually restored its recreational and environmental value.
Most large cities in newly industrialising and developing countries have rivers in the same condition as the Thames in the 19th century. They are a health hazard. They threaten downstream irrigation areas. And they destroy ecosystems. Because of inadequate management, water quality is deteriorating at an increasing rate throughout a large part of the world. Much is unknown about the impacts of water resource development on ecosystems, and even basic data on water quality are not available on a global scale. But we can still draw some conclusions:
- There is a critical need to integrate water and environmental management, as provided for under the concept of integrated water resource management.
- Investments are lagging behind urban needs for the collection, treatment, and disposal of municipal and industrial wastewater-and behind rural needs for more efficient irrigation, drainage of surplus irrigation water, and control of agricultural runoff.
- Water quality may be the biggest emerging water problem in the industrial world, with the traces of chemicals and pharmaceuticals not removed by conventional drinking water treatment processes now being recognised as carcinogens and endocrine disrupters.
- Leaks of nuclear waste into aquifers and surface water have not been brought under control, especially in the transition economies of Central and Eastern Europe. A long-term solution for the safe disposal of nuclear waste, to prevent contamination of water resources, has not been implemented anywhere.
- Half the rivers and lakes in Europe and North America are seriously polluted, though their condition has improved in the past 30 years. The situation is worse in developing countries that lack sewerage and industrial waste treatment.
The impacts of agriculture on water quality are less visible but over time as least as dangerous, because many of the fertilisers, pesticides, and herbicides used to boost agricultural productivity slowly accumulate in groundwater aquifers and natural ecosystems. Their impact on health may become clear only decades after their use, but their more immediate impact, through eutrophication, is on ecosystems. These problems accumulate in fresh and saltwater bodies, such as the Baltic and Black Seas.
Groundwater, the preferred source of drinking water for most people in the world, is also being polluted, particularly through industrial activities in urban areas and agricultural chemicals and fertilisers in rural areas. In Western Europe so many nutrients are spread over croplands that excess nitrate finds its way into groundwater, ruining drinking water sources in Denmark, France, and the Netherlands. The difficulty and cost of cleaning up groundwater resources, once polluted, make the accumulation of pollutants in aquifers particularly hazardous.
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