About Wallis Dam

The Wallis region — known in French as Valais — is the hydropower capital of Switzerland and one of the most significant Alpine energy-producing territories in Europe. Occupying the upper Rhône valley between the Pennine Alps to the south and the Bernese Alps to the north, Wallis concentrates the highest density of major dams anywhere in the Alps. The canton alone accounts for roughly half of Switzerland's total hydropower storage capacity, which is approximately 4,300 GWh or around 3,655 hm³ when expressed as stored volume. The Grand Dixence dam, the tallest gravity dam in the world at 285 metres, stores water from 35 glaciers collected by an extraordinary network of underground tunnels stretching more than 100 kilometres through the mountain massif. The Lac des Dix, its reservoir, holds 401 million cubic metres at full supply level — making it the largest reservoir in Switzerland by volume. Other landmark structures include the Mauvoisin arch dam (250 m, one of the highest arch dams globally) impounding the Lac de Mauvoisin, and the Mattmark dam, an embankment dam holding the Mattmarksee at the head of the Saas valley. Glacier retreat is the central long-term concern for Wallis hydropower: as glaciers shrink they initially release more meltwater, temporarily boosting reservoir inflows, but the long-term trajectory is towards reduced summer flows. Swiss federal agencies monitor this transition carefully, and Wallis reservoirs are managed with increasing seasonal precision to balance immediate supply with multi-year resource sustainability. The Rhône river, originating from the Rhône Glacier at the Furka Pass, drains the region westward through Martigny before flowing into Lake Geneva.