Kathmandu, 5 June 2007 – The rapid shrinking of Himalayan glaciers, which has accelerated at a considerable rate over the past decade, could have catastrophic consequences for communities living downstream and the millions who rely on glacial melt water, a new report says. The report, with detailed case studies on the impact of warming temperatures on glaciers and glacial lakes in two glacial hot-spot areas in the Himalayan region, warns of the increasing likelihood of glacial lake outburst floods (GLOFs) – when rising waters from glacial melt breach the dam holding back a glacial lake – and calls for early warning and mitigation measures to avert disaster.
The extended Himalayan mountain range feeds nine perennial river systems in the region which constitute a lifeline for nearly 1.3 billion people downstream. Nearly 15,000 glaciers and 9,000 glacial lakes have been identified across five countries in the region – Bhutan, Nepal, Pakistan and selected basins of India and China. Of these, some 200 lakes have been identified as potentially dangerous.
Observations of individual glaciers indicate that, in some cases, rates of retreat have doubled since the early 1970s, though they vary from basin to basin. The Dudh Koshi is the largest sub-basin and most densely glaciated region in Nepal and contains 12 of the 20 potentially dangerous glacial lakes identified in the country. The glaciers in this basin are retreating at an average of 10 to 60 m annually; the Imja glacier by as much as 74 m a year. Melting glaciers are also leading to some of the fastest-growing glacial lakes in the region; the lakes form in the gap left between the retreating glacier terminus and the end moraine.
In Bhutan, the Luggye Glacier retreated by 160 m between 1988 and 1993 resulting in rapid growth of the lake Luggye Tso. The Raphstreng Glacier retreated 35 m per year on average between 1984 and 1988; the retreat rate almost doubled to 60 m per year between 1988 and 1993.
Glacial lake outburst floods can have varying degrees of socioeconomic impact. Their impact can be quite extensive since they can destroy villages, agricultural land, roads, bridges, hydropower plants, and trekking trails, as well as causing loss of life. The Tibetan Zhangzhangbo GLOF in 1981 caused extensive infrastructural damage and nearly US$3 million in losses. The Dig Tsho GLOF in Nepal in 1985 destroyed a power plant with a loss of US$1.3 million, destroyed homes and land, and caused considerable loss of life. The Luggye Tso GLOF in Bhutan in 1994 damaged the sacred Dzong and cultivated land, and also caused loss of life.
The Hindu Kush-Himalaya glaciers are also an important source of freshwater for hundreds of millions of people living downstream. Glacial retreat is also causing long term loss of natural fresh water storage.
"The significance of these glaciers and glacial lakes to downstream communities is of particular importance. Changes in glacier ice or snowmelt affects water yield to downstream regions heightening the risk of water shortages, impacts irrigation water for crops, and may disrupt industry and power generation," said Dr. Andreas Schild, Director General of the International Centre for Integrated Mountain Development.
"We have to continue monitoring glaciers and glacial lakes to ensure sound management of these valuable water resources. In addition, the use of early warning systems like satellite-based techniques, dam breach, and hydrodynamic modelling are important for implementing mitigation measures to reduce risks to vulnerable mountain populations,” said Surendra Shrestha, Regional Director of the UNEP Regional Office for Asia and the Pacific.
The report, The Impact of Climate Change on Himalayan Glaciers and Glacial Lakes, was produced by the International Centre for Integrated Mountain Development (ICIMOD) with the United Nations Environment Programme (UNEP) and launched during the World Environment Day regional celebrations held in Kathmandu, Nepal on 5 June 2007.
World Environment Day, commemorated each year on 5 June, is one of the principal vehicles through which the United Nations stimulates worldwide awareness of the environment and enhances political attention and action. The World Environment Day slogan for 2007 is ‘Melting Ice – a Hot Topic?’ In support of International Polar Year, the WED theme selected for 2007 focuses on the effects that climate change is having on polar ecosystems and communities, and the ensuing consequences around the world.
