Why are there plans to raise some of our Alpine dams?

Raising some dams will increase their storage capacity, allowing them to play a greater role in regulating our electrical system. Above all, it would contribute to the seasonal storage of electricity at a rate of 2 to 3 TWh, reducing our winter imports and substantially increasing our energy independence.

Of the 200 or so existing dams in Switzerland, around 20 of the largest are technically predestined for raising. Some of them (Mauvoisin, Vieux Emosson) have already been raised from 10 to 40 metres, each resulting in an increase in reservoir volume of 15 to 30 million cubic metres and additional production of 45 to 100 GWh.

Consequently, a modest increase of 10 to 15% of their initial height would increase their water holding capacity by approximately 700 million cubic metres.

With global warming, the melting of our glaciers is accelerating, releasing an increasing volume of water into our alpine storage lakes. Instead of being able to store it for later use in turbines, many of our dams have to let this blue gold flow in the summer because their reservoirs are too small. Raising the dams will also capture this additional water.

When a dam is full, it must be turbined or it will overflow. However, in summer, the amount of electricity that our dams must produce in order not to overflow often exceeds our consumption, and must be exported, often at low prices and outside peak hours. The advent of wind and especially solar energy will further increase the amount of electricity produced in summer, thus increasing the differential between consumption and production. By increasing the storage capacity of our alpine lakes, it would be possible to better modulate hydropower production according to wind and sun conditions. All the water that was not turbined when solar production was at its maximum could be stored for later use. And if too much solar and wind power is generated, then it will still be possible to store it through pumped storage [→ Q73].

Finally, all this water that we did not need to be turbined in the summer can be stored until the following winter when our energy demand is at its peak. This is the principle of seasonal storage [→ Q75]. This seasonal storage could increase our winter hydroelectric production by 5 to 8% (2 to 3 TWh), further reducing our import requirements [→ Q66]. This increase corresponds to approximately half of our annual electricity deficit.

By all accounts, raising our alpine dams is an option to be considered with great interest as it would significantly increase the flexibility of our hydropower production in a highly volatile electricity market, and would contribute to increasing our degree of energy self-sufficiency through seasonal storage. Unfortunately, the current very low electricity prices do not allow such work to be profitable [→ Q70].