Through the existing Grande Dixence power plants, the new Gornerli reservoir will enable 650 million kWh of power production to be transferred from summer to winter, contributing to secure the national electricity supply. The annual power production of Grande Dixence will also increase by 200 GWh net as a result of increased water volume and reduced pumping costs.
The natural hazards for the city of Zermatt and all the municipalities downstream of Zermatt significantly increase with the melting glaciers and climate change. The planned Gornerli reservoir provides a retention volume that will substantially reduce the flood hazards.
Glaciers are an important water reservoir, but they continue to melt. As a result, securing the regional drinking and irrigation water supply is becoming increasingly important. The Gornerli reservoir will help to counteract this issue in the future.
GORNERLI MULTI-PURPOSE RESERVOIR PROJECT
The project consists in erecting a new concrete dam with an underground pumping station downstream of the Gorner glacier, in a geologically suitable gorge. There is no need for any equipment, since the new reservoir will be fully integrated into the existing Grande Dixence hydroelectric scheme.
Gornerli is the largest of the 15 round table projects that representatives of the federal government, cantons, environmental organisations and power plant operators decided to pursue in 2021. The Council of State of Valais included the project in the cantonal structure plan. The next steps involve the federal government incorporating the project into the cantonal structure plan, the preliminary cantonal procedure based on the preliminary environmental study, the subsequent permit and planning approval process and the regulation of the residual value at the end of the permit.
The glaciers in the Gornera catchment area are melting as a result of climate change, and the water inflows are changing drastically. The amount of meltwater from the glaciers will remain above average and will decrease towards the end of the century. Due to these changes caused by climate change, the planned Gornerli reservoir will act as a water reservoir in the long term (reduction of flood peaks, securing drinking and irrigation water supply, sediment transport).
ENVIRONMENTAL AND LANDSCAPE PROTECTION
The environmental impact report is drafted and the replacement and offsetting measures are defined as part of a participatory process together with the Federal Office for the Environment, various cantonal offices, environmental organisations, representatives from the fishing branch, the Swiss Alpine Club, the Zermatt mountain guides and the town of Zermatt. The only visible and long-lasting impact of the project in nature is the dam itself. No new paths, roads or high-voltage power lines are required. The Owner is aiming to produce as little CO2 as possible from the construction of the dam. The fact that the project is located in a BLN (Bundesinventar der Landschaften und Naturdenkmäler [Federal Inventory of Landscapes and Natural Monuments]) area is clearly taken into account.
The cantonal structure plan will be adopted by the federal government in January 2024. The preliminary technical project and the preliminary environmental study have now been completed, and the corresponding dossier will be submitted as part of the preliminary cantonal procedure in winter 2023/24. The next step involves drawing up the final project and the environmental impact assessment (EIA). This lays the foundation for the subsequent concession and planning approval process, which is scheduled to be submitted in 2025.
Grande Dixence SA is the Owner of the planned project. Grande Dixence is owned by Alpiq Suisse SA (60%), Axpo Power AG, BKW Energie AG and IWB (13.3% each).
The project will be developed and carried out together with the town of Zermatt, while the towns of Mattertals and all other concession municipalities of Grande Dixence will be closely involved in the project.
The Gornera water is currently diverted directly to the Z’Mutt pumping station and pumped up (pumping height 470 m) into the main collecting system of Grande Dixence to be transported to the Lac des Dix. The Gornera water will now be stored behind the Gornerli dam and collected into the existing tunnel system via an underground pumping station at a higher level (pumping height 232 metres). It will then be routed and turbined via the existing Grande Dixence scheme.
FACTS & FIGURES
As of December 2023
- Catchment area: Monte Rosa area with the Gorner and Grenz glaciers
- River: Utilisation of the already captured Gornera
- Protection zone: BLN site 1707 Dent Blanche – Matterhorn – Monte-Rosa
- Dam: Arch dam, height 85 m, length 245 m
- Dam location: Gorge between the Gorner and Gletschergarten/Furi glaciers
- Maximum altitude: 2,254 m.a.s.l.
- Active storage volume: 150,000,000 m3
- Concrete volume: 180,000 m3
- Underground pumping station: 2 pumps, pump height from 200 to 265 m
- Power plant: Integration in the existing Grande Dixence power plant system
- Additional winter energy: 650 million kWh per year
- Additional net electricity production: 200 million kWh per year
- Investment costs: CHF 300 million
- Commissioning: 2030 at the earliest, depending on the permit process