Forces Motrices de la Gougra SA has launched a consultation on constructing a new headrace tunnel between Vissoie and Niouc in the Val d’Anniviers. The proposed tunnel would replace the existing one to improve water flow efficiency and fully utilize the production capacity of the Navizence power plant.
The company has submitted a construction permit application to the canton of Valais for the project. The new tunnel would replace the current conduit connecting the Vissoie compensation reservoir to the pressure line that supplies the Navizence plant in the Rhône plain.
The existing non-pressure tunnel, built in 1908 and renovated in 1950, is a bottleneck in the system, limiting water flow to 10.8m³/sec. Other components of the hydropower network are designed for a higher capacity of 15m³/sec. The Navizence plant, which was fully renovated in 2013, was also built for this increased capacity. The new pressure tunnel would align with this standard, allowing for greater efficiency. It would increase the Navizence plant’s capacity from 50MW to 70MW and generate an additional 20 GWh of electricity annually –enough to power nearly 4,500 households. This would bring the total annual production of the system to approximately 660 GWh.
The new pressure tunnel will be built east of the current tunnel and excavated using a tunnel boring machine. It will stretch 8,200m and is expected to cost around CHF 100 million. Under the Federal Energy Act, the project qualifies for investment contributions from the Swiss Confederation, which supports major hydropower renovations.
The shareholders of Forces Motrices de la Gougra SA – Alpiq (54%), Rhonewerke (27.5%), and the municipalities of Anniviers (7.71%), Sierre (7.5%), Chippis (1.79%), Chalais (0.5%), and Oiken (1.0%) – will decide on proceeding with the project based on investment aid approval and profitability assessments. If approved, work is expected to begin in 2027 and take approximately five years to complete. The facilities are licensed for hydropower generation until 2084.
To offset environmental impact, Forces Motrices de la Gougra has agreed to support a forest revitalization project between Pramin and Soussillon in the Bois de Finges. This area is listed in the Federal Inventory of Landscapes and Natural Monuments of National Importance. The initiative has already received approval from the Federal Office for the Environment and cantonal authorities.
The Vissoie–Niouc project is part of broader upgrades to Forces Motrices de la Gougra’s infrastructure. Built in the 1950s, the main facilities have undergone renovations to ensure long-term production of renewable energy. The Navizence power plant was modernized in 2013, and the Mottec plant’s refurbishment was completed last year. Work is also ongoing to replace machinery at the Vissoie plant.
In addition to these upgrades, studies on raising the Moiry dam – a project under the Swiss Confederation’s Hydropower Round Table – will continue through 2025.
