Saturday, October 15, 2011

Glacier Lakes: Growing danger in the Himalayas.

The Guardian published an article on 11 October 2001 entitled “Deadlier by the day. The Himalayan lakes that are threatening a disaster.” This article is about the hazard of Glacial Lake Outburst Floods (GLOFs), and the increased hazard with more glacier front lakes developing as glaciers retreat due to climate warming. The article PLUS A VIDEO ON THIS TOPIC can be reached via the link above, or via:
An example given in the article is Glacial Lake Imja which did not exist in 1953 when Everest was first climbed. In 1992 the lake was about 1.3km long ( see ) Teije Watanabe has been studying this lake since the 1990s and returned in September this year and found the lake much larger (about 2.4km long). Like many of these ice front glacier lakes, this lake is dammed by moraine deposited by the glacier as it retreated. Some moraine barriers are even more hazardous because they are ice cored (ice buried in glacial sediment), and the moraine may subside as the ice melts. Now there is a risk of the moraine barrier on Lake Imja being eroded by a meltwater flood (possibly aided by collapse of buried ice, if present). This could release the large volume of water held behind the moraine barrier and a mega flood would surge down the valley destroying villages, drowning people, damaging agricultural land etc. There are a range of possible counter measures: reducing lake volume by siphoning water or by diversion tunnels , strengthening the natural spillway over the moraine dam, etc. However the remote location of many of these glacial lakes makes all engineering work difficult and more expensive.
John Reynolds, a British engineering geologist with much experience of this topic, cautions that Lake Imja is not the most hazardous, but it has had more attention because it is close to the main route to Mount Everest. There are many potentially hazardous glacial lakes. He advises that a Himalaya wide evaluation of GLOF risk is needed and an action plan needs to be drawn up to tackle this hazard in the Himalaya on an international scale.

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