Thursday, December 06, 2007

Tsho Rolpa outburst threatened

The Tsho Rolpa glacial lake in the high Nepalese Himalayas, has been carefully monitored for a number of years. The lake is constrained by a moraine dam which is vulnerable to ground movements (from landslides, glacier falls and seismic activity) and from melting of ice blocks contained within it. The glacial outburst flood that could potentially result from a breach of the moraine dam would reach villages as far as 100km downvalley. Subsequent water shortages would have severe effects on the Ganges as well as Nepal. The glacier which feeds Tsho Rolpa has receded rapidly over the last 10 years - a function of global warming - and the lake grows in length by 100m each year. Controlled lake drainage via an artificial outlet channel ensures that water levels are gradually being reduced, but not at a sufficient rate to reduce pressure on the moraine. Nepal has 17 similar glacial lakes which have no control measures in place. Further information can be found at: http://tinyurl.com/ytkkpm. The image shows a small ice-marginal lake at Hoffelsjokull in Iceland.

1 comment:

Brot said...

Hi Dawn --

I recently wrote an article on GLOFS in Khumbu and Rolwaling for OnEarth magazine (I lived in te Himals for 20 years). I don't have figures at hand, but would question the 100m/year glacial retreat rate (a bit less than this?) and I wonder if a GLOF there would have (after the surge) any long term measurable affect on the flow of the Ganges. Also, the lake was lowered by 3+ meters over a period of a few weeks some years ago, and has remained right at that level -- the level of the weir installed in the terminal moraine. Regards, Brot Coburn
bcoburn@wyoming.com