From: Water & Wastewater News
Published April 27, 2009 09:49 AM

NCAR Study Blames Climate for River Water Loss

Rivers in some of the world's most populous regions are losing water, according to a comprehensive study of global stream flows. The research, led by scientists at the National Center for Atmospheric Research (NCAR) in Boulder, Colo., suggests that the reduced flows in many cases are associated with climate change and could potentially threaten future supplies of food and water.

The results will be published May 15 in the American Meteorological Society's Journal of Climate. The research was supported by the National Science Foundation (NSF), NCAR's sponsor.

"The distribution of the world's fresh water, already an important topic," says Cliff Jacobs of NSF's Division of Atmospheric Sciences, "will occupy front and center stage for years to come in developing adaptation strategies to a changing climate."

The scientists, who examined stream flows from 1948 to 2004, found significant changes in about one-third of the world's largest rivers. Of those, rivers with decreased flow outnumbered those with increased flow by a ratio of about 2.5 to 1.Several of the rivers channeling less water serve large populations, including the Yellow River in northern China, the Ganges in India, the Niger in West Africa, and the Colorado in the southwestern United States.

In contrast, the scientists reported greater stream flows over sparsely populated areas near the Arctic Ocean, where snow and ice are rapidly melting.

"Reduced runoff is increasing the pressure on freshwater resources in much of the world, especially with more demand for water as population increases," said NCAR scientist Aiguo Dai, the lead author of the journal paper. "Freshwater being a vital resource, the downward trends are a great concern."

Many factors may affect river discharge, including dams and the diversion of water for agriculture and industry. The researchers found, however, that the reduced flows in many cases appear to be related to global climate change, which is altering precipitation patterns and increasing the rate of evaporation.

The results are consistent with previous research by Dai and others showing widespread drying and increased drought over many land areas.

The study raises wider ecological and climate concerns.