Nature knows no mercy

The Lac de Mauvoisin in the Valais Alps is located at about 2,000 metres above seal level. The reservoir with a capacity of 212 million m3 is one of the largest in Switzerland. The lake is surrounded by high, glacier-covered mountain peaks that rise to 4,313 metres above sea level with the Grand Combin. In the winter the area attracts off-piste skiers, and in the summer hikers pass by the dam. A great deal of work stands behind this idyllic scene. The reservoir and the power plants down in the valley are at the mercy of nature: Avalanches and landslides are not uncommon.

At the end of March 2018, the town of Fionnay in the Val de Bagnes still had a snow cover of nearly 6 metres. For obsessive skiers who want to stay on the slopes until April/May such conditions are a dream. For the Mauvoisin power plants and the 36 employees, weather changes such as those in the winter of 2017/2018 have a direct impact on work. As a rule: The more snow, the more snow removal work around the power plants. "This amount of snow at this time of year is unusual - normally there’s an accumulation of about 4 metres at the end of March," reports Johan Savioz, Head of Operations at Kraftwerke Mauvoisin.

Safety first

The road to the valley that passes by the four power plants - Fionnay, Chanrion, Champsec and Riddes - must be accessible at all times. "We have to be physically present at the plant four days per month to carry out manual measurements. We have to ensure access to the power plant regardless of the amount of snow," explains Johan Savioz. Safety always comes first when clearing the access road: "In the winter months we work with a retired power plant employee who is a trained mountain guide and lives year round in Fionnay. He knows the mountains well. He is good at assessing the weather conditions in the area." Avalanches are not uncommon. Depending on the avalanche size and how much debris has landed on the road, two people need about one to two days to clear the road to the power plant. Nature sometimes knows no mercy: No sooner has an avalanche been cleared, the next one buries the road again - and the power plant employees have to expect these scenarios during winters with high precipitation.

Visible climate change

Johan Savioz has been working for the power plant in the Valais for 23 years. The contrast between the past and the present is enormous: "The glaciers get smaller every year and have shrunk by up to 50 metres. In place of the glacier tip that once reached the water catchment in the past is a stream running several hundred metres toward the valley before it reaches the plant," explains the power plant expert.
The outlook for glaciers with a southern exposure and located below 3,700 metres above sea level is less than rosy: ETH researchers predict that by the year 2100 glaciers will have disappeared completely. The natural inflows to the power plants, including glacier melt water, would then decrease from 270 million m3 today to 200 million m3. Johan Savioz also comes to this conclusion: ”Today we can benefit from the volumes from the Giétroz, Brenay, Otemmag, Corassière and Mont-Durand glaciers. But the outlook for the future is very different."

Landslides - difficult to predict

Avalanches and their risks can be relatively accurately predicted. The local mountain guides are trained and equipped to assess these situations. Landslides are different: Even experts have difficulty determining where a landslide might occur after heavy precipitation. The Mauvoisin power plants have a safety concept to ensure that workers arrive safely at the plant. "We work closely with the local mountain guides in the summer as well. We assess the risks in the area together," explains Johan Savioz, "and sometimes we can't clear a landslide until temperatures drop again and the inflows decrease - meaning in October/November. To make these assessments, our expert is often en route by helicopter to inspect an area. Safety also comes first when it comes to landslides."