International Year of Mountains
Global Warming Triggers Glacial Lakes Flood Threat
 | | UN Photo |
We are halfway through the International Year of Mountains and the International Year of Ecotourism, intended to highlight the fragility and threats to these vital ecosystems from global warming, unsustainable tourism, pollution and other impacts, and to galvanize Governments, industry, non-governmental organizations and the public to act and protect.
The observances of the Year come as scientists with the United Nations Environment Programme (UNEP) and the International Centre for Integrated Mountain Development (ICIMOD) have reported the finding of at least 44 glacial lakes in the Himalayas that are filling so rapidly they could burst their banks in as little as five years’ time, sending millions of gallons of deadly floodwaters swirling down valleys and putting tens of thousands of lives at risk. The lakes are rapidly filling with icy water as rising temperatures in the region accelerate the melting of glaciers and snowfields that feed them.
In Nepal, for example, data from 49 monitoring stations reveal a clear increase in temperature since the mid-1970s, with highest temperatures found at higher altitudes. On average, air temperatures here are one degree Celsius higher than in the 1970s, rising by 0.06 degrees per year. It is not just people who are at risk but many millions of dollars’ worth of property, tourism facilities, trekking trails, roads, bridges and hydroelectric plants, which are the economic lifeblood of many countries in the region. Surendra Shrestha, Regional Coordinator in Asia for the UNEP Division of Early Warning and Assessment, observed that any one of twenty potentially dangerous glacial lakes in Nepal and 24 in Bhutan could burst its banks in five to ten years’ time with catastrophic results for people and property hundreds of kilometres downstream. “These are the ones we know about. Who knows how many others elsewhere in the Himalayas and across the world are in a similar critical state?”
 | The boundaries and delineations on this map do not imply official endorsement or acceptance by the United Nations. |
Pradeep Mool, a remote sensing expert with ICIMOD, said work is under way to lower the water levels of one critical glacial lake pinpointed by on-the-ground surveys and new satellite images. This is the Tsho Rolpa Lake that feeds the Rolwaling and Tama Koshi valleys in the Dolakha District of Nepal. Researchers have found that, as a result of the melting of a nearby glacier, the lake has grown sixfold, from an area of 0.23 square kilometres in the late 1950s to one of 1.4 square kilometres now. “A flood from this lake could cause serious damage down to the village of Tribeni, which is 108 km downstream, threatening about 10,000 human lives, thousands of livestock, agricultural land, bridges and other infrastructure”, said Mr. Mool.
A high-tech communications network of sensors and sirens has been linked from the lake to the villages at risk from floodwaters. Engineering work is under way to lower the water levels at Tsho Rolpa by 30 metres. But experts say money is needed urgently for similar work on scores of other glacial lakes. Some donor Governments are helping, but much more aid is needed. "It is a costly problem because glacial lakes are situated in remote areas which are difficult to reach", said Mr. Shrestha.
 | The boundaries and delineations on this map do not imply official endorsement or acceptance by the United Nations. |
“Part of our work is to help the Governments of Nepal and Bhutan find and focus on potentially dangerous lakes, develop early warning systems, be able to warn communities of an impending Glacial Lake Outburst Flood (GLOF), and to carry out engineering works to reduce the threats”, he added.
GLOFs are not a new phenomenon, but there is evidence that the frequency of such events has risen over the past three decades. In August 1985, a sudden outburst flood from the Dig Tsho glacial lake in Nepal destroyed fourteen bridges and caused $1.5 million in damage to the nearly completed Namche Small Hydropower Plant.
The new research, announced in April 2002, began in 1999 and based on topographic maps, aerial photographs and satellite images from Landsat, Spot and IRS craft, has identified 3,252 glaciers and 2,323 glacial lakes in Nepal, and 677 glaciers and 2,674 glacial lakes in Bhutan. Of the 44 high-risk lakes identified, Bhutan’s Raphstreng Tsho glacial lake in the Pho Chu River sub-basin measured 1.6 km long, 0.96 km wide and was 80 metres deep in 1986. The latest figures (1995) show the lake has swollen to be 1.94 km long, 1.13 km wide and has a depth of 107 metres. Its neighbouring glacier could generate a GLOF up to two-and-a-half times that which caused major devastation in October 1994.
The 43 others show similar patterns. Filling of the lakes, and the threat of their mud and debris walls being breached, are a result of rising temperatures melting the glaciers. Glaciers in Bhutan are retreating at a rate of 30 to 40 metres a year, even faster in some areas . The Tradkarding glacier, which feeds the Tsho Rolpa glacial lake in Nepal’s Rolwaling Valley, is retreating at a rate of over 20 metres a year and in some years within the last decade reached 100 metres per year.
 | In this Indian mountain village, the inhabitants must walk down over one half mile to carry up water. (Photo/Bob Sherman) |
“Mountains were once considered indomitable, unchanging and impregnable. But we are learning that they are as vulnerable as the world’s oceans, grasslands and forests to environmental threats and insensitive, unfettered, development”, said Klaus Töpfer, Executive Director of UNEP. “The findings from our joint studies in the Himalayas, the roof of the world, reveals the extent of a new and alarming threat. It is not just the risk to human lives, agriculture and property that should worry us. Mountains are the world’s water towers feeding the rivers and lakes upon which all life depends. If the glaciers continue to retreat at the rates being seen in places like the Himalayas, then many rivers and freshwater systems could run dry, threatening drinking water supplies, as well as fisheries and wildlife. We now have another compelling reason to act to reduce emissions of carbon dioxide and other greenhouse gases.”
Climate change and other environment and development issues, including those affecting mountains, are a special focus of the World Summit on Sustainable Development.
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