'Peak water' and glacier melt pose thorny problems downstream
Dec. 7, 2011
A Peruvian watershed has likely passed 'peak water,' dropping river flows 30 percent. New lakes are draining the Himalaya, and say good-bye to Rocky Mountains' glaciers.
More coverage from the 2011 American Geophysical Union fall meeting
By Douglas Fischer
Daily Climate editor
SAN FRANCISCO – New data underscores the bleak prospects facing glaciers across the world as emissions continue to rise. In many instances, particularly the tropics, researchers expect the ice serving as key mountain reservoirs will disappear or severely degrade, leaving downstream communities to cope with scarce and unreliable supplies.
Exhibit A is the Andes, where the glacial runoff provides water for hundreds of thousands throughout Peru and Ecuador. Where scientists once thought the region had 10 years to 40 years to adapt to reduced runoff, that time is now up, said Michel Baraër of McGill University in Montreal.
"We have passed peak water," he said on Wednesday at the American Geophysical Union meeting in San Francisco. "As a consequence, (during) the dry season, we will get lower discharge and increased variability in flow."
Meanwhile, accelerated melting rates suggest North American glaciers will not survive the century, said Garry Clarke, emeritus professor at the University of British Columbia.
And in the Himalaya, the increasing emergence of mid-glacier lakes has become a rising concern for researchers who say the lakes fill, drain and refill at surprising rates.
The drop in the Rio Santo, in northern Peru, could leave river flows during the dry season 30 percent below current levels.
Considering that 80 percent of the water in the Rio Santo is diverted near its mouth for agriculture, that spells trouble. "Instead of having 10, 20, 40 years to find water to use, or some sort of adaptation, in fact this time does not exist," Baraër said.
Similar upheaval could come to the Canadian Rockies, Clarke said.
Human emission are exceeding even the worst-case scenario painted by the Intergovernmental Panel on Climate Change. But even if emissions dropped to meet the IPCC's "middle-of-the-road" projections by 2100, glaciers in the Rockies will be toast by 2100, Clarke said. That will lead to a host of ecological and social changes, from stream flows to tourism.
"We are going to be witness, over the next century, to the disappearance of glaciers in western North America," he said.
Photo of the Cordillera Blanca in Peru courtesy Nick Leonard/flickr.
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