WARMING THREATENS WORLD'S MAJOR RIVERS

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22 april 2009

Climate change threatens Ganges, Niger and other mighty rivers

Suzanne Goldenberg, US environment correspondent The Guardian , Wednesday 22 April 2009

Some of the mightiest rivers on the planet, including the Ganges, the Niger, and the Yellow river in China, are drying up because of climate change, a study of global waterways warned yesterday.

The study by the National Centre for Atmospheric Research in Colorado found that global warming has had a far more damaging impact on rivers than had been realised and that, overwhelmingly, those rivers in highly populated areas were the most severely affected. That could threaten food and water supply to millions of people living in some of the world's poorest regions, the study warned.

"In the subtropics this [decrease] is devastating, but the continent affected most is Africa," said NCAR's Kevin Trenberth. "The prospects generally are for rainfalls, when they do occur, to be heavier and with greater risk of flooding and with longer dry spells in between, so water management becomes much more difficult."

The scientists examined recorded data and computer models of flow in 925 rivers, constituting about 73% of the world's supply of running water, from 1948-2004. It found that climate change had had an impact on about a third of the major rivers. More than twice as many rivers experienced diminished flow as a result of climate change than those that saw a rise in water levels.

In addition, those rivers that did see a rise were in sparsely populated, high latitude areas near the Arctic Ocean where there is rapid melting of ice and snow.

The authors said their study brought new clarity to an understanding of the long-term effects of climate change on waterways. "I think our study settles the question regarding long-term trends in global streamflow," said Aiguo Dai, the lead author of the report.

The greatest danger was posed to those dependent on the Niger in West Africa, the Ganges in South Asia and the Yellow river in China. The Colorado river in the US was also experiencing a drop in water levels.

Other big rivers in Asia, such as the Brahmaputra in India and the Yangtze in China, remained stable or registered an increase in flow. But the scientists said they too could begin shrinking because of the gradual disappearance of the Himalayan glaciers.




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