Rivers shrinking: Flow of many rivers in decline

WASHINGTON The flow of water in the world's largest rivers has declined over the past half-century, with significant changes found in about a third of the big rivers. An analysis of 925 major rivers from 1948 to 2004 showed an overall decline in total discharge. The reduction in inflow to the Pacific Ocean alone was about equal to shutting off the Mississippi River, according to the new study appearing in the May 15 edition of the American Meteorological Society's Journal of Climate.

The only area showing a significant increase in flow was the Arctic, where warming conditions are increasing the snow and ice melt, said researchers led by Aiguo Dai of the National Center for Atmospheric Research in Boulder, Colo. "Freshwater resources will likely decline in the coming decades over many densely populated areas at mid- to low latitudes, largely due to climate changes, Dai said. "Rapid disappearing mountain glaciers in the Tibetan plateau and other places will make matters worse." Added co-author Kevin Trenberth, "As climate change inevitably continues in coming decades, we are likely to see greater impacts on many rivers and water resources that society has come to rely on."

While Dai cited climate change as a major factor in the changes, the paper noted that other factors are also involved, including dams and the diversion of water for agriculture and industry. Nonetheless, he said, "long-term changes in streamflow should be a major concern under global warming."

http://news.yahoo.com/s/ap/20090421/...rinking_rivers