Built at the same time as the hydroelectric power station, the EDF green cable car flies over Chamonix (Haute-Savoie), its skiers and its chamois on the slopes of the Mer de Glace. “It’s not trivial to be able to go to work by cable car”concedes Loïc Trehiou, head of the plant. “Access is exclusively by this means and, possibly, by helicopter when necessary.” The Alps power plant, which produces electricity from water from the Mer de Glace, will however have to review its copy. EDF, which manages it, announces that it will be necessary to modify one of its most spectacular installations, located under the immense glacier to exploit the torrents of water which it carries in the basement. Indeed, global warming is accelerating the retreat of the glacier, which is disrupting production.
Loïc Trehiou turns on the headlamp of his helmet. “To work here, you must not be claustrophobic, not be dizzy and be in fairly good physical condition for walking”, he warns, before opening the door to a two-kilometre-long gallery dug into the mountain. At the end of this gallery, an iron staircase so vertical that it already takes your breath away. “We have 314 steps to climb. We pass 70 meters above sea level, which is the equivalent of a 25-storey building”he explains, before slipping: “Usually the climb is remembered.”
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The climb is indeed intense. After a short rest, we arrive at the level of the three water intakes which alone sum up the race between the operator of the plant and the melting of the glacier. “Ten years ago the glacier and the water intake to capture the water below was much lower”remembers Yves Giraud, the director of the hydroelectric department of EDF, which takes care of all the dams and works activated by water.
“Given the global warming, we had to dig a new gallery of about a kilometer to fetch water higher up, but this one caught up with us again. We will again have to fetch water differently.”
yves giraudat franceinfo
This new work will cost 3 million euros, to be added to the 25 million that had to be devoted to the search for the current water catchment point.
This collection point, similar to a waterfall, leads to an underground room. Workers work there to reinforce the walls, on metal and plank scaffolding. In the bursts of fire from the soldering irons, you have to act quickly: the room is only accessible three months a year. In the center, a basin collects the water of the glacial torrent and the ceiling of this room which does not resemble anything known. “It’s the ice of the Mer de Glace glacier”describes Loïc Trehiou. “That means there are several tens of meters of ice above us.” But this monster with its skin of transparent ice spikes and bluish hollows will continue to disappear at the rate of 40 to 50 meters per year.
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Outside, in a white of snow and silence, Yves Giraud shows the deep valley into which a tunnel covered with ice emerges. “15 years ago, where we are, there was 40 meters of ice above us. You see that 40 meters has disappearedhe explains. The front of the glacier itself has retreated several hundred meters. We have before our eyes the impact of climate change.”
If global warming continues at the same rate, future generations will only see the Mer de Glace as a lake and a mountain stream. The power station may still be there, but it will capture water at the mouth of the torrent, in the open air, like many others. The eight kilometers of galleries dug in the heart of the Mont Blanc massif will only tell an old story.
Report by Grégoire Lecalot in the hydroelectric power station of the Mer de Glace
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