Glacial lakes threaten Himalayan floods

Posted: 24 May 2002

Nearly 50 lakes, high in the Himalayas, could burst their banks sending millions of gallons of deadly floodwaters swirling down valleys, putting at risk tens of thousands of lives scientists are warning.

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 reveals a clear increase in temperature since the mid-1970s with highest temperatures found at higher altitudes. On average, air temperatures here are one degree C higher than in the 1970s rising by 0.06 degrees C 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 hydro-electric plants which are the economic life-blood of many countries in the region.

Scientists with the United Nations Environment Programme (UNEP) and the International Centre for Integrated Mountain Development (ICIMOD) have found at least 44 glacial lakes that are filling so rapidly they could burst their banks in as little as five years' time.

Surendra Shrestha, Regional Coordinator in Asia for UNEP's Division of Early Warning and Assessment, said: "Our findings indicate that 20 glacial lakes in Nepal and 24 in Bhutan have become potentially dangerous as a result of climate change. We have evidence that anyone of these could, unless urgent action is taken, burst its banks in five to 10 years time with potentially 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?"

Pradeep Mool, a remote sensing expert with ICIMOD, said work is underway 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.

The researchers have found that, as a result of the melting of a nearby glacier, the lake has grown six-fold, 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 108km 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 villages at risk from floodwaters. Engineering work is underway to lower the water levels at Tsho Rolpa by 30 metres.

Nevertheless, experts say money is needed urgently to carry out similar work on scores of other glacial lakes if catastrophes are to be averted.

"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. Some donor country governments are backing our efforts but much more aid is needed. Solving this problem is going to be costly because glacial lakes are situated in remote areas which are difficult to reach," said Mr Shrestha.

The findings come in the International Year of the Mountains. The United Nations hopes the year will highlight the fragility and threats to these vital ecosystems from global warming, unsustainable tourism, pollution and other impacts. It is also hoped that the year will galvanize governments, industry, non-governmental organizations and the public to act to protect the world's precious mountain ranges for future generations.

Related links:

  • For full report on Nepal, including video clips and photographs.

  • For a report on Bhutan, including video clips and photographs.

  • Maps pin pointing those glacial lakes assessed as dangerous can be found at: http://www.grida.no/inf/news/news02/news30.htm

  • Background information on UNEP's glacial lake outburst flood monitoring and early warning word can be found on the web at: http://www.rrcap.unep.org/issues/glof/