Engineers drain water trapped in French Alps glacier

Workers have begun draining an immense lake that has built up under the Alpine glacier on Mont Blanc, an attempt to prevent a repeat of a flood that killed 175 people more than 100 years ago. Authorities have warned this lake, which has no outlet, could burst at any time, carrying ice, mud and rock with it into the valley’s 900 homes and endangering the lives of more than 3,000 residents in the French Alpine valley.

The 65,000 cubic meters of water -- enough to fill 20 Olympic pools -- was discovered in the Tete-Rousse glacier last month by researchers of the National Center for Scientific Research (CNRS).

Warmer temperatures may have played a role in creating the lake, melting the surface snow, but it was a cold snap that was thought to have frozen the natural drainage routes.

The process of draining the lake is expected to take until October. The engineers, working around the clock, will drill a 22cm diameter hole in the ice on top of the glacier to begin pumping a third of the water from a pocket 200m below the surface. The pumping will drain 150 cubic meters of water per hour which will be released on another glacier at very low speed.

"With the start of pumping, the water pressure will be much smaller and therefore the risk of it bursting and flooding would be greatly diminished," said Nicolas Carre, the site supervisor.

The glacier is at 3,200 meters altitude. Given the uncertainty of the drilling results the town has set up a glacier alert system, with sirens to warn the population of problems. However, many locals fear the water would come down the mountain so quickly that no real evacuation could take place in time.

Authorities said it was not excluded that water could be trapped inside the glacier again in the months or years to come.

Source:
Reuters,"Engineers drain water trapped in French Alps glacier", accessed August 26, 2010
Geneva Lunch,"French engineers drain glacier’s lake to save Saint Gervais", accessed August 26, 2010