Tuesday, August 11, 2009

Dangerous Swiss Glacial Lake to be Drained.

A glacial lake has formed above the town of Grindelwald in the Swiss canton, Bern. Since the lake has no overground drainage, it poses a risk of bursting through the weakest point and flooding the valley below. The formation of the lake is attributed to global warming over the Alps and melting of the lower Grindelwald glacier (Unterer Grindelwaldgletscher, in German) leaving a huge basin filled with meltwater. I have noted before that I am convinced by the recession of this glacier, that I have witnessed personally over the past 25 years that there is a redistribution of heat over the earth, and the Alps are indeed warming, whether the planet as a whole is or not. In 1984, my wife and I actually sat on the edge of the glacier, so close was it to the alpine path; now it has receded tens of metres back.

I became aware of this glacial lake only last week, while visiting the Bernese Oberland, and finding the Glacial gorge (Gletscherschluct) was closed beyond the first 150 meters. The reason for this is that a serious engineering project is now underway to help the lake to drain. A tunnel is to be dug by drilling and blasting some 2 km diagonally in the flank of the Maettenberg mountain to the glacial lake, allowing a giant "plug-hole" through which the lakewaters can drain into the gorge. It is proposed that the working 700 metre "hole" will be ready by september (the lower 1.3 km being only to provide an access channel), and allowing that 3 metres of rock are advanced by each blast, this must amount to say three blasts per day (over 60 or so days), removing around 11,000 tonnes of rock altogether, in 15 tonne segments, the detritis from which will be cleared out by a large scooping-machine that can traverse the incipient tunnel, and dumped into the gorge. Interestingly, enormous quantities of rock are discharged into the gorge and Luetchine river system there naturally, and further downstream there is a cement factory, which uses this bestowal of rock (converted to a pulverised form) as a useful raw material, so nothing goes to waste. A good example of Swiss pragmatism.

The lake is 700 metres long, 300 metres wide and 35 metres deep and is estimated to hold currently 1.7 million cubic metres (tonnes) of water. It is feared that an avalanche or heavy rainfall could trigger severe flooding of the areas below, even as far as Interlaken. Since this is a central region for tourism in Switzerland, if it did flood it would be very bad for business.

It is planned that the drain will be in full operation by spring 2010.

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