Degraded rivers worldwide

Posted: 14 July 2003

More than half of the world's major rivers are either heavily polluted and/or drying up in their lower reaches because of over-use, according to the World Water Council. Of the world's 500 major rivers, 250 are seriously polluted and depleted from overuse. Contamination and overuse of river basins displaced some 25 million environmental refugees in 1998/99.

Click here for maps showing major river basins of the world

However, two of the world's largest river systems - the Amazon that drains a vast area of South America and the Congo River in sub-Saharan Africa - remain relatively healthy. The main reason: both have few industrial or population centres in their watersheds.

Among the world's most troubled rivers include:

  • The Nile River in Egypt. Only 10 per cent of the Nile's waters ever reach the Mediterranean Sea. And this small amount is heavily polluted with agricultural, industrial and municipal wastes. The result: Delta fisheries have been decimated. Of 47 varieties of commercial fish caught in the Delta 30 years ago, only 17 remain. The rest have become extinct or are on the verge of disappearing.

  • China's Yellow River. Over the past decade, the Yellow River has not reached the Bo Hai Sea on average for three to four months every year. In 1997, the river ran dry in its lower reaches for two-thirds of the year, a record-breaking 226 days. Throughout the 1990s its waters, once a torrent to be revered and feared, have trickled out as far as 600 kms inland.

  • The Amu Darya and Syr Darya Rivers in Central Asia. The flow of these two major rivers that once fed the Aral Sea which borders Kazakhstan and Uzbekistan in Central Asia have been reduced by three-quarters since the late 1960s. As a consequence, the sea has receded by up to 100 kms. Two-thirds of its volume has been lost.

  • The Colorado River, USA. Since so much of the river's life giving waters have been siphoned off for irrigation agriculture, little is left by the time the river reaches Gulf of California in Mexico. Its once rich delta is now a desiccated wasteland where no riverine life survives.
Riverine ecosystems are endangered virtually everywhere by non-sustainable development and the over-use and misuse of limited freshwater resources. According to the International Water Management Institute, 20 per cent of freswater fish species are considered vulnerable, endangered of already extinct.

In the past 30 years there has been a 50 per cent decline in populations of freshwater species, the fastest rate of decline as compared with species living in marine and forest ecosystems. (WWF International)