Thursday, April 23, 2009

CRITICAL WORLD RIVERS LOSING WATER

Reuters - Rivers in some of the world's most populated regions are losing water, many because of climate change, researchers reported. Affected rivers include the Yellow River in northern China, the Ganges in India, the Niger in West Africa, and the Colorado in the southwestern United States.

When added to the effects from damming, irrigation and other water use, these changes could add up to a threat to future supplies of food and water, the researchers reported in the American Meteorological Society's Journal of Climate.

Aiguo Dai of the National Center for Atmospheric Research in Boulder, Colorado, who led the study, said in a statement: "Freshwater being a vital resource, the downward trends are a great concern."

Dai's team looked at records of river flow in 925 big rivers from 1948 to 2004, finding significant changes in about a third of the world's largest rivers.

Rivers with decreased flow outnumbered those with increased flow by 2.5 to 1, they said. . .

The Columbia River in the U.S. Northwest lost about 14 percent of its volume from 1948 to 2004, largely because of reduced precipitation and higher water usage in the West, Dai's team said.

But the Mississippi River drains 22 percent more water because of increased precipitation across the U.S. Midwest since 1948, they said.

Annual discharge from melting ice into the Arctic Ocean also rose about 10 percent, or 460 cubic kilometers.