Glacial lakes and associated floods in the Hindu Kush-Himalayas

It is now generally accepted that climate warming is having a significant impact on the Himalayas. One of its effects is that glaciers are thinning and retreating throughout much of the region. This is accompanied by formation of melt-water lakes, both on the glacier surface and in front of them. Already several, like Imja Lake and Tsho Rolpa, are more than two kilometres long and about 100 metres deep. Glacial lakes are usually dammed by end moraines; these are mounds of rubble carried down the valley by glaciers and deposited as ridges when the glaciers were much larger than today. Because the moraines are not well consolidated and frequently contain an ice core that is also melting they are often unstable. This means that glacial lakes are in danger of bursting their moraine dams to cause a catastrophic flood (GLOF) in the valley below. Several outbursts have already occurred with attendant loss of life and property, although it should be noted that the actual threat is often exaggerated.

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