Busted Lakes
Last year WWF released a report warning that Himalayan glaciers are currently receding at an average rate of 33 to 50 feet (10 to 15 meters) per year.
In India (see map) the Gangotri Glacier, the source of the Ganges (or Ganga) River, is retreating at a rate of 75 feet (23 meters) annually.
The report also noted that air temperatures in the region have risen by 1.8°F (1°C) since the 1970s—twice as much as average warming in other northern hemisphere countries over the same time period.
WWF says environmental impacts associated with faster melting glaciers include an increased risk of flooding and landslides.
At least 20 glacier lakes in Nepal have grown to the point where they could potentially burst, according to a 2001 survey by the United Nations Environment Program.
Formed by accumulated meltwater, the overfilled lakes could suddenly discharge massive volumes of water, known as glacial lake outburst flooding (GLOF).
Such flooding can cause loss of life and widespread damage to villages, roads, bridges, and farmland.
"GLOF is a major threat in Nepal as a result of climate change," Rai, of the WWF Nepal Program, said.
"We have been seeing this quite often, and we feel that there will be more in the near future. Lots of glacier lakes are expanding in size."
From Flood to Drought
Jennifer Morgan, director of WWF's Global Climate Change Program, says glacial melting will also increase the volume of water in rivers, causing widespread flooding.
"But in a few decades this situation will change, and the water level in rivers will decline," she added.
Over time, as the glaciers become smaller, seasonal melt will decrease and contribute less water to annual river flows.
For example, researchers at the National Institute of Hydrology in Roorkee, India, estimate that reduced glacier meltwater would cut July-through-September river flow of the Ganges by two-thirds.
This decline would leave 500 million people and 37 percent of India's irrigated land short of water.
Himalayan glaciers also feed six other of Asia's great rivers—Indus, Brahmaputra, Salween, Mekong, Yangtze, and Huang Ho—putting communities across this region at risk of water shortages.
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