Melting Himalayan Glaciers May Doom Towns

Pallava Bagla in New Delhi
for National Geographic News
May 7, 2002
Dozens of mountain lakes in Nepal and Bhutan are so swollen from melting
glaciers that they could burst their seams in the next five years and
devastate many Himalayan villages, warns a new report from the United

It's hardly news that the world's glaciers are
melting—a phenomenon widely attributed to gradually rising global
temperatures. But the possible consequences in terms of human deaths and
loss of property have reached greater urgency in light of the findings
of the new study.

It was conducted by scientists from the United Nations Environment Program (UNEP), headquartered in Nairobi, Kenya, along with remote-sensing experts from the International Center for Integrated Mountain Development (ICIMOD) in Katmandu, Nepal.

They predict that in the next half a decade or so, the Himalayas could experience intense flooding as mountain lakes overflow with water from melting glaciers and snowfields.

The lives of tens of thousands of people who live high in the mountains and in downstream communities could be at severe risk as the mud walls of the lakes collapse under the pressure of the extra water. Major loss of land and other property would aggravate poverty and hardship in the region.

The new flood warning is based on three years of research involving site visits and studies of topographical maps, satellite images, and aerial photography. The scientists assessed the conditions of about 4,000 glaciers and 5,000 glacial lakes in Nepal and Bhutan.

"Our findings indicate that 20 glacial lakes in Nepal and 24 in Bhutan have become potentially dangerous as a result of climate change," said Surendra Shrestha, Asian regional coordinator of the UNEP's Division of Early Warning and Assessment, which is based in Bangkok, Thailand.

Bigger Threat Unknown

The researchers say that the 44 lakes they identified as potentially dangerous in the near future is a conservative estimate of the number of sites that may pose a serious threat.

"These are the ones we know about," said Shrestha. "Who knows how many others, elsewhere in the Himalayas and across the world, are in a similar critical state?"

The UNEP-ICIMOD study focused only on the two small land-locked countries of Nepal and Bhutan. The team says it looked at these countries earlier than others since the governments of Bhutan and Nepal requested them to do so. In the second phase, the work is being expanded to include Pakistan, China, and countries in central Asia.

Negotiations begin this month to extend the study to India. The largest part of the Himalayas lies within India, although "almost nothing is known about glacial lake outburst floods from India," said Sarfaraz Ahmed, a glacier expert at the School of Environmental Sciences at Jawaharlal Nehru University in New Delhi.

Studies done by the Geological Survey of India have revealed that, on average, glaciers in India have been receding at the rate of about 15 meters (about 50 feet) every year.

More revealing and detailed findings are expected to be published by the UNEP group this year, which the United Nations has designated the "International Year of the Mountains."

Global warming is among a number of environmental threats facing mountains, whose ecosystems are much more vulnerable than suggested by the hardy terrain. Throughout the year, the UN also plans to draw attention to risks posed to mountains by the effects of unsustainable tourism and pollution.

Sprawling Lakes

Those who follow patterns of global warming are not likely to be surprised by some of the findings of the UNEP-ICIMOD study. Data from 49 meteorological monitoring centers in Nepal indicate that temperatures have been rising about 0.06 degrees Celsius each year since the mid-1970s, with the average temperature now a degree higher.

Glacial melting associated with the temperature warming has expanded the size of many lakes in the region.

The UNEP study found, for example, that in less than a decade, from 1986 to 1996, the Raphstreng Tsho glacial lake in the Pho Chu River sub-basin of Bhutan swelled from 1.6 kilometers (about one mile) to 1.94 kilometers (1.2 miles) in length, from 0.96 kilometers (0.6 miles) to 1.13 kilometers (0.7 miles) in width, and from 80 meters (262 feet) to 107 meters (351 feet) in depth.

Another lake deemed at critical risk of bursting is Tsho Rolpa in the Dolakha district of Nepal. Half a century ago the lake, which supplies water to the Rolwaling and Tama Koshi Valleys, extended 0.23 square kilometers (0.1 square miles). Today its expanse is 1.4 square kilometers (0.5 square miles).

Pradeep Mool, a remote sensing expert with ICIMOD, said ground and aerial surveys revealed the imminent risk of flooding by Tsho Rolpa, and efforts are now under way to reduce the lake's water level by 30 meters (about 100 feet). At stake are 10,000 human lives, as well as livestock, land, bridges, and other infrastructure, in the village of Tribeni, located 108 kilometers (67 miles) downstream.

Growing Problem

Flooding from glacial lake outbursts is not new, but evidence points to increased frequency of such events over the past three decades.

In one such incident, the Dig Tsho glacial lake in Nepal overflowed in August 1985, destroying 14 bridges and causing $1.5 million worth of damage to the uncompleted Namche small hydropower plant in the region.

Klaus Toepfer, executive director of UNEP in Nairobi, Kenya, said the findings of the new study illustrate the threat that many of the world's mountains—the "water towers of the world that feed the rivers and lakes upon which all life depends"—face as a result of the impacts of climate change.

"We now have another compelling reason to act to reduce emissions of carbon dioxide and other greenhouse gases," he said.

UNEP is using the findings of the survey to implement programs to mitigate the potential disaster. There is no timetable as yet, but the agency is hoping to start as soon as possible.

One project, for example, is working to install warning systems to alert people in the region about impending glacial flooding. A communication network of sensors and sirens now links Tsho Rolpa in Nepal with villages at risk from floodwaters.

At the same time, engineering works are being put in place to reduce the threat, as in the project to reduce water levels in Tsho Rolpa.

Yet obtaining the funding to support these and other anti-disaster initiatives is a constant challenge.

"Some donor country governments are backing our efforts, but much more aid is needed," said Shrestha. Millions of dollars will be required.

With many lakes at risk of glacial flooding still not identified, the concern about the need for funding is even more urgent.

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