PROJECT OVERVIEW

The Swiss Confederation’s Energy Strategy 2050 provides, in particular, for the development of renewable energies. Against this backdrop, from August 2020, representatives of key players in the hydropower sector responded to Simonetta Somaruga’s invitation to form a round table to discuss the challenges of hydropower, the Swiss Confederation’s net-zero climate objective, security of electricity supply and the preservation of biodiversity. This round table brought together politicians, representatives of power producers and the main environmental protection associations. Its aim was to identify projects with the smallest possible environmental impact compared to the expected output. A final declaration made it possible to select 16 projects of national interest and to provide for the principle of project-specific compensation measures and general recommendations for the protection of biodiversity and the landscape. The most important project on this list is the Gornerli multi-purpose reservoir, which alone could provide about one-third of the additional winter power electricity of all of this round table’s hydropower projects.

As part of the plan to expand winter energy in Switzerland, Grande Dixence is also studying the project to raise the Grande Dixence dam (project Dix+, providing up to a maximum of 100 GWh of additional winter energy). The feasibility of this project is currently being studied. This project is neither an alternative to nor a rival of the Gornerli project, but could be an suitable addition in the overall context of the Grande Dixence facilities.

Today, the water from the Gornera is conveyed to the Z’Mutt pumping station to be pumped back into the collector to transport it to Lake Dix. With the Gornerli project, the water will in the future be stored in the new reservoir, transferred to the existing tunnel system via a new underground pumping station located higher up and then turbined in the existing Grande Dixence facilities. The Gornerli reservoir will increase winter electricity production by storing summer flows. It will save almost half of the pumping energy thanks to a reduced delivery head, while better use will be made of the summer peak flows.

One of the challenges lies in determining the future useful volume of the reservoir, which depends on various factors including the speed at which the glaciers are retreating, from future inflows and statutory minimum water releases. These factors are currently still being studied in collaboration with external experts, including ETH Zurich, and depend on knowledge of climate scenarios. The latest knowledge in this field is taken into account in the development of the project.

The work mainly involves the construction of the dam and the underground pumping station. The client currently expects the dam height to measure around 85 metres. Once the ongoing studies into the future useful volume have been completed, the definitive dimensions will be finalised.

The work will be planned in such a way as to minimise disruption to the Municipality of Zermatt and the impact on the environment. The remote location of the dam and the constraints linked to the tourism in Zermatt make the construction site logistics particularly complex. The project relies mainly on the use of the existing railway facilities (MGB/GGB) up to the Findelbach station and then on a temporary cableway up to Schweigmatten (Furi). From Schweigmatten, a new access tunnel will be built leading to the dam site and the pumping station. The routing of heavy vehicles through the village will be kept to a minimum and limited to special transport subject to local authority approval. A worker accommodation and transhipment site is planned in the vicinity of Schweigmatten. Negotiations with landowners are currently underway.

• 2021 : Inclusion of the project in the Hydropower Round Table
• 2023 : Technical preliminary project and preliminary environmental survey
• 2023 : Inclusion of the project in the cantonal master plan by the State Council of the Canton of Valais
• 2024 : Validation of the inclusion of the project in the cantonal master plan by the Confederation
• Since 2024 : Anchoring in law of additional compensation measures provided for by the Round Table
• Since 2024 : Preparation of concession amendments and compensation for residual value with licensors
• Since 2024 : Participatory approach with interest groups within the framework of the Gornerli Dialog and the different specific working groups
• Since 2024 : Project development and Environmental Impact Assessment (EIA)
• Since 2025 : Analysis of the useful volume and height of the dam based on conclusions drawn from current climate scenarios
• Since 2025 : Logistics concept development
• Since November 2025 : Start of negotiation of concession amendments and compensation for the residual value with the Association des communes concédantes de Grande Dixence (Association of Grande Dixence licensing municipalities – ACC GD)
• Winter 2026/27 : Decision to grant concession amendments by the licensors. The submission of the building permit application will follow this decision.
  Completion of the licensing application, including the concession amendments and residual value agreement

The finalisation of the preliminary procedure pursuant to Art. 13 of the Cantonal Act on the Use of Hydropower, the submission of the project file and the granting of concession amendments by the licensing authorities depend on the ongoing procedure (see above). The above steps, the cantonal authorisation procedure, potential appeals or objections, agreement on the residual value, the award of subsidies and the client’s decision to build will determine the date on which work will start. After that, it will take approximately 6 years before the installation is commissioned. Although the progress of the project depends heavily on external factors, commissioning around 2035 currently seems realistic.

As part of the pre-project studies, Grande Dixence drilled extensive test boreholes that confirmed the results of the preliminary geological studies, showing that the geology is generally favourable to the construction of an arch dam.

Further studies are under way to optimise project planning and achieve the objectives, focussing in particular on the fields of geology, hydrology, glacial lakes, lake formation, the dam, the pumping station, logistics and environmental and landscape protection. The findings will be taken into account and incorporated into the Environmental Impact Assessment (EIA) and the construction project and will help define the necessary compensation measures.

The client and investor in the Gornerli project is Grande Dixence SA. The current project study is being carried out in collaboration with the main shareholder Alpiq, various external specialist companies and leading research institutes such as ETH Zurich, EPF Lausanne and the Institute for Snow and Avalanche Research (SLF).

The Municipality of Zermatt is kept abreast of project progress and asserts its interests as necessary. The 19 other licensing municipalities of Grande Dixence, as well as the State of Valais, are kept regularly informed about the project. Grande Dixence is owned by Alpiq Suisse SA (60%), Axpo Power AG, BKW Energie SA and IWB (13.3% each).

• Catchment area: Monte Rosa massif with the Gorner and Grenz glaciers
• Rivers: Gornera catchment already partially exploited
• Protection zone: object IFP 1707 Dent Blanche – Matterhorn – Monte Rosa
• Dam: arch dam, height approx. 85 m, length approx. 275 m
• Location of the dam: blocking point between the Gorner Glacier and Furi (below the Gagenhaupt), 1 km upstream of the existing Gornera water intake
• Useful volume of the reservoir: max. 150,000,000 m³
• Volume of concrete: approx. 220,000 m³
• Underground pumping station: Three pumps, delivery head from 200 to 265 m
• Power plant: integration into the existing Grande Dixence power plant network
• Additional winter electricity: max. 650 million kWh per year
• Additional electricity production: approx. 200 million kWh per year
• Investment costs: at least CHF 300 million
• Commissioning: around 2035, depending on various external factors

(Project status: 2025)