Swiss glacier drainage tunnel in full flow
Swiss glacier drainage tunnel in full flow Apr 2010
News release by Swiss Canton of Bern

Water flow towards the outlet...

Melt water from the Grindelwald Glacier high in the Swiss Alps is being successfully drained away and prevented from posing a threat to communities further down the valley.
Early on Tuesday morning this week (27 April, 2010) water started flowing from the outlet window and into the gorge below forming a spectacular new, man-made waterfall.
Melt water into the artificial glacial lake, created by a landslide several years ago, had increased in recent early Spring days, and, with a volume of about 250,000m3, had reached the inlet level of the purpose built drainage tunnel, bringing it into successful operation. Since early Tuesday an estimated 3m3/sec of water flow, or about 3,000 liters/sec has flowed from the lake. The 800m tunnel carries melt water through the mountain, around the artificial dam that creates the threatening lake, and via the impressive water fall of some 140m from the tunnel outlet, back into the Lütschine River below.

...creates a spectacular waterfall

The tunnel was excavated last year as an urgent, emergency project to limit the danger of a sudden failure of the landslide dam by the increasing size of the glacial melt water lake. Seeing water flowing from the high cliff window was proof that the tunnel is performing its protective function as intended.
Now, thanks to the tunnel and its low level overflow intake, the volume of the lake is controlled. 1 million m3 and so removes the danger of flash floods in the Grindelwald Valley down to Lake Brienz.
Glacier tunnel protects Swiss communities - TunnelTalk, Nov 2009
Gletschersee Grindelwald


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