Lac des Dix

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Lac des Dix
Grande-Dixence dam with Lac des Dix reservoir
Grande-Dixence dam with Lac des Dix reservoir
Location: SwitzerlandSwitzerland Switzerland
Canton of ValaisCanton of Valais Valais
Tributaries: various mountain streams
Drain: Dixence
Lac des Dix (Canton of Valais)
Lac des Dix
Coordinates 597010  /  102054
Data on the structure
Lock type: Gravity dam
Construction time: 1950–1961, 1995 *)
*) additional water intake for Cleuson-Dixence
Height of the barrier structure : 285 m
Building volume: 5 960 000  m³
Crown length: 695 m
Data on the reservoir
Water surface 3.65 km²
Maximum depth 227 m
Total storage space : 400 000 000  m³
Catchment area 340 km²
  • Largest reservoir in terms of volume in Switzerland
  • The world's highest gravity dam
  • World record highest working pressure of a hydropower turbine (> 180 bar)
Map Lac des Dix.png
Installations hydroélectriques de la Grande Dixence de.svg
Grande Dixence
Coordinates 585330  /  114558
country SwitzerlandSwitzerland Switzerland
Canton of ValaisCanton of Valais Valais
Waters Lac des Dix, Lac de Cleuson
Type two-stage storage power plant group with several pumping stations
Primary energy water
power turbine:
834 MW (shut down in 2016)
321 MW
owner Alpiq Suisse : 60%
Axpo Power : 13 13  %
BKW Energie : 13 13  %
IWB : 13 13  %
operator Hydro Exploitation SA
Project start 1926
Start of operations 1934
Shutdown Central:
Chandoline: 2013
Fionnay: 2016
Nendaz: 2016
turbine 17 Pelton twin turbines:
Chandoline: 5
Fionnay: 6
Nendaz: 6
Energy fed in 2011 Total:
940 GWh
Chandoline: 115 GWh
Fionnay: 370 GWh
Nendaz: 455 GWh
was standing 2013 (from 2017 all centers shut down, water is used by Bieudron)
Coordinates 585632  /  114713
country SwitzerlandSwitzerland Switzerland
Canton of ValaisCanton of Valais Valais
Waters Lac des Dix
(owned by Grande Dixence)
Type Storage power plant
Primary energy water
power Bieudron: 1260 MW
owner Alpiq Suisse : 722
Grand Dixence: 1522
operator Hydro Exploitation SA
Project start 1993
Start of operations 1999
(2009 after repair of the pressure line)
Shutdown Dec. 2000 to Jan. 2010 for repairs to the pressure line
turbine 3 vertical Pelton turbines
Energy fed in 2019 2201 GWh
was standing January 1, 2020

The Lac des Dix [ ˌlakdeˈdis ] is a reservoir that lies in the upper part of the Val d'Hérémence in the canton of Valais in Switzerland . The Grande Dixence dam on the Dixence dams the lake to the target of 2364  m above sea level. M. on. It is located 17 km south of the canton capital Sion , was the fourth highest dam in the world in 2015 and at 285 meters the tallest structure in Switzerland. The lake and dam are part of the Grande Dixence power plant , but are also used by the Cleuson-Dixence power plant .


The old dam wall from 1934 that remained in the new lake

First Dixence dam

From 1926 to 1934 Energie de l'Ouest Suisse SA (EOS) built the first Dixence dam. This pier dam with a crown height of 85 m was designed by engineers Alfred Stucky and Jean Landry . Electricity was generated in the Chandoline power station from 1934.

Between 1947 and 1951, an inlet tunnel from Lac de Cleuson to Lac des Dix was built to increase electricity generation.

Grande Dixence power plant

In 1950, Grande Dixence SA was founded as a subsidiary of EOS with the aim of using the water from all tributaries of the Rhone between the Vispa and Dranse de Bagnes . A new dam was to be built and an over 100 km long network of inlet tunnels to fill the lake. Contrary to expectations, the water rights on the Dranse de Bagnes were not given to Grande Dixence SA, but to Forces Motrices de Mauvoisin SA, which built Lac de Mauvoisin with the associated power plants. The planning of the system was carried out by the company's own office with the support of Alfred Stucky.

In order to finance the large-scale project and to use the energy generated by the system, EOS looked for other partners that were found in German-speaking Switzerland. These were BKW , NOK and the city ​​of Basel . However, EOS remained the main shareholder in Grande Dixence SA with a 60% stake in the company.

The construction of the new Grande Dixence dam lasted from 1951 to 1965. Over 3000 workers were involved in the construction project.

The flooding was initiated on July 17, 1957 by opening the old dam wall. The other parts of the plant were put into operation in stages between 1961 and 1965. In addition to the dam, these were the 24 km long main tunnel at an altitude of 2,400 meters, which is fed with water from four pumping stations, and two new power plants, which together with the existing Chandoline power plant convert the lake water into electrical energy. The pumping stations are located in Zmutt and Stafel above Zermatt and in Ferpècle and Arolla in the Val d'Hérens , the power stations in Fionnay in the Val de Bagnes and near Nendaz in the Rhone Valley.

Closure of the Chandoline headquarters

The Chandoline headquarters was shut down on May 1, 2013 because it was no longer economical to operate. In 2015, the dismantling of the technical systems was in progress.

Micro cracks in the pressure pipe

In the summer of 2016, microcracks were found in the weld seams of the pressure pipe from the Nendaz headquarters during the overhaul . Only the above-ground section of the line between Péroua and Condémines is affected by the damage. The Nendaz and Fionnay centers were therefore no longer in operation and the affected part of the pressure line was emptied. The damage is said to cost CHF 48.5 million . The preparatory work began in the summer of 2019. A restart is planned for 2023.

Cleuson-Dixence power plant

Between 1993 and 1998, the existing facilities were supplemented with the Cleuson-Dixence project , which enables better use of the reservoir contents by connecting an additional power station to the reservoir. For the new Bieudron power plant with an output of 1269 MW, a water intake had to be drilled into the dam wall and a 15.8 km long supply tunnel and a 4.3 km long pressure tunnel with a surge tank had to be built. The facility cost CHF 1.3 billion and is completely underground. It was able to increase the total output of the power plants supplied by the Lac des Dix by a factor of 2.5, making it possible to process the contents of the reservoir in just 1000 hours. The output of the Bieudron power plant corresponds roughly to that of a nuclear power plant and can be made available to the grid within just three minutes.

Rupture of the pressure tunnel

On 12 December 2000 against 20:10 in 1999 put into operation, tight running under the slope surface burst pressure pipe with a nominal diameter of 3.2 m, the water from the water tower Tracouet ( 2250  m above sea level. M. ) to the power plant in Bieudron ( 540  m above sea level ) leads. The line was torn open between Condémines and Fey ( 1234  m above sea level ) over a length of 9 m and a gap width of 60 cm. A 3 m long longitudinal seam of the steel cladding burst, and the crack propagated through two more sections of the pipe. The head slide on the water lock was automatically closed immediately. Nevertheless, about 27,000 m³ of water leaked out, which was located above the break point up to this slide in the pipe.

This killed three people and seven mountain huts and four barns were destroyed by the water, rock and earth, 17 other mountain and garden huts and three farms were damaged, and around 100 hectares of forest, pastures and orchards were devastated by mud. The road between Sion and Riddes and the Rhone itself were buried.

The Bieudron power plant, which was designed to cover peak loads and has an output of 1269 MW, then failed for several years. After the repairs had been carried out, the plant was put back into operation in January 2010. The operations manager and a person in charge of the tunnel manufacturer were sentenced in August 2008 to a fine on probation for negligent homicide.

The economic loss due to the failure of the generators in Bieudron is of a special kind: it was a loss of power, but not a loss of (energy) production, as the water from the Lac des Dix is ​​still in the existing power plants in Fionnay, Nendaz and Chandoline could be used.


The ownership structure of the power plants that use the water of Lac des Dix is ​​somewhat complex: the Fionnay and Nendaz power plants are operated by Grand Dixence SA , and the Bieudron power plant by Cleuson-Dixence SA . The decommissioned Chandoline power plant and the rights to the old dam from 1934 are managed by Alpiq Suisse AG and the municipalities that granted the concession for this first power plant.

Grand Dixence SA

The Grand Dixence SA is one of 60% of Alpiq Suisse SA and each 13 1 / 3  % of the Axpo Power AG , the BKW Energie AG and the Industrielle Werke Basel (IWB). The company in turn holds 45% stakes in Elektrizitätswerk Zermatt AG (EWZ) so that the use of the Zmuttbach can be optimized, 35% in Hydro Exploitation SA , which maintains and operates the power plants of the Lac des Dix, and 68.2% in the Cleuson-Dixence SA and 29% in Force Motrice de la Borgne SA (FMdB), which operates power plants down the valley from the dam.

Cleuson-Dixence SA

The Cleuson- Dixence SA is among 31.8% of Alpiq and 68.2% of the Grand Dixence SA. All plants have been operated by Hydro Exploitation SA since 2003 , in which Grand Dixence SA has a 35% stake.

Dam wall

Grande Dixence dam

The Grande Dixence gravity dam was with a height of 285 meters until 1980 the highest dam in the world. In 1980 the Nurek Dam , the highest wall in the USSR (now Tajikistan ), which was 300 meters high, exceeded it. Two walls in China were completed in 2010 and 2014; the 292 m high Xiaowan Dam and Jinping I at 305 meters. Two of these barrier structures are stone embankments , one an arched wall, which means that the Grande Dixence will continue to be the highest gravity dam in the world. A list of the tallest dams can be found in the list of the largest dams in the world .

At the base, the Grande Dixence is 200 meters thick and the crown is 695 meters long. More than 6 million m³ of concrete were used during construction  , the weight of the wall is around 15 million tons. Over 30 km of tunnels have been created inside the wall for maintenance and inspection.

A cable car runs from the foot of the dam to the Krone . The 640 m long run from 1964 is designed as an aerial tramway with cabins for 15 people.


The Lac des Dix is ​​about 5.3 km long, an average of about 600 meters wide and a maximum of 227 m deep. Its area, which varies with the fill level, is approximately 4 km².

The capacity is around 400 million m³. The reservoir is filled with water through a network of inlet tunnels and pumping stations, which comes from the 75 water catchments in the 375 km² catchment area, in which there are 35 glaciers . The annual amount of water collected is an average of 500 million m³, the majority of which occurs in summer. The lake contains around a fifth of the electrical energy that can be stored in Switzerland .

Situation map

Grand Dixence hydropower plants

Pumping stations

The main tunnel is supplied with water by the following pumping stations.

Pumping stations location Municipal area Installation Nacelle
(m. Above sea level. M.)
El. Power
( MW )
pump Delivery head
Design flow
(m³ / s)
Z'Mutt 620952  /  95010 Zermatt 1965 1972 86.4 4th 370 17.4 Most powerful station in the facility
Stafel 618550  /  94827 Zermatt 1964 2180 26.5 3 212 09.9
Ferpècle 608505  /  100856 Evolène 1962 1896 21.3 3 212 08.4
Arolla 603500  /  95772 Evolène 1963 2009 48.6 3 312 12.6
Cleuson 590970/106810 Conthey 1950 2110 04.1 4th 162 02.5


Chandoline power station, 1934–1935. Machine room with the original three generators, the remaining generators were installed between 1942 and 1944.

The potential energy from the water stored in the lake is converted into electrical energy in three central units. The Chandoline power plant, which is also part of the system, has been shut down for an indefinite period of time since July 2013 for economic reasons. The Fionnay and Nendaz headquarters have been out of operation since the beginning of summer 2016 because microcracks were found in the pressure pipe above the Nendaz headquarters. All of the water in the reservoir is now only processed in the Bieudron headquarters. All processed water flows into the Rhone .

Headquarters location Municipal area Installation Nacelle
(m. Above sea level. M.)
El. Power
( MW )
Pelton turbines Maximum raw height of fall
Design flow
(m³ / s)
Fionnay 589518  /  98254 Bagnes 1957 1490 300 6 twin turbines 0878, 0 45.0 Not to be confused with the Lac de Mauvoisin power station of the same name . Shut down since summer 2016. Recommissioning planned for 2023.
Chandoline 595099  /  119038 Sion 1934 0493 150 5 twin turbines 1878, 0 10.0 Shut down since July 2013
Bieudron 585632  /  114713 Nendaz 1999 0481 1260, 0 3 vertical turbines 1883, 0 75.0 Was out of operation for nine years from December 12, 2000 due to the pressure tunnel breaking. Most powerful power plant center in Switzerland and at the same time the water scraper center that feeds the most energy into the grid in Switzerland.
Nendaz 585330  /  114558 Riddes 1960 0478 384 6 twin turbines 1013.5 45.0 Despite its name, Nendaz , the power plant is located in the municipality of Riddes. Shut down since summer 2016. Recommissioning planned for 2023.

The standard work capacity of the Bieudron headquarters was 2.2 TWh (2 billion  kWh ) in 2019, making it the Swiss hydropower plant with the largest electricity production. The combined output of Grande Dixence and Cleuson-Dixence is 2.1 GW. To classify these figures, the following information: the Gösgen nuclear power plant has an output of one gigawatt and produced 7.8 TWh in 2019, the total electricity consumption in Switzerland was 57.2 TWh in 2019.


Jean-Luc Godard made his first own film, Opération Béton , in 1954 , which reported on the construction of the Grande Dixence dam. Godard himself worked there as a construction worker to supplement his finances.

After the tower restaurant of the Ostankino TV tower in Moscow, the crown of the dam is the highest area of ​​a structure accessible to tourists in Europe.


180 ° panoramic image photographed in the axis of the main dam. General viewing direction: west

See also


  • Grand Dixence SA (Ed.): Grand Dixence - recharge your batteries in the middle of the Alps . 2015 ( [PDF]).
  • Grand Dixence SA (Ed.): Grand Dixence - Technical Documentation . 2015 ( [PDF]).

Web links

Commons : Lac des Dix  - collection of images, videos and audio files

Individual evidence

  1. GO Dixence . In: Hydroscope . June 24, 2015, p. 13 ( ).
  2. a b c Nendaz: une conduite forcée aérienne sera remplacée. In: Le Nouvelliste. April 27, 2020, accessed on May 7, 2020 (French).
  3. Cleuson-Dixence. Alpiq Switzerland, archived from the original on March 22, 2016 ; accessed on May 13, 2015 .
  4. ^ Cleuson-Dixence en Valais: une catastrophe absolue. on, December 14, 2000
  5. ^ Dossier "Rupture du puits blindé Cleuson-Dixence". (PDF) April 2002, accessed on August 23, 2009 (French, link broken, document can no longer be found on the Internet).
  6. Opening address. (PDF; 96 kB) (No longer available online.) Archived from the original on November 8, 2011 ; Retrieved June 8, 2010 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  7. Comité Française de Méchanique des Roches (ed.): Rupture et réparation de la conduite en charge de Cleuson- Dixence .
  8. ^ Swiss television: SF Videoportal - Tagesschau - verdict made. (Video) (No longer available online.) August 6, 2007, formerly in the original ; Retrieved August 23, 2009 .  ( Page no longer available , search in web archivesInfo: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link /  
  9. Tribunal fédéral, 6B_337 / 2008 / rod, Arrêt du 7 janvier 2009
  10. ^ A b N. Rouge: Gérer les installations hydrauliques à court terme pour assurer le long terme: le défi du gestionnaire d'actifs . Ed .: Alpiq . May 18, 2017 ( [PDF]).
  11. Hydropower: Grande Dixence is celebrating three birthdays in Valais. In: look. August 28, 2015 .;
  12. ^ Cleuson-Dixence (Canton of Valais). In: RAOnline EDU. Retrieved December 9, 2018 .
  13. Grand Dixence SA, Technical Documentation, p. 49
  14. Cable car database - 15-PB Dixence-Lac des Dix (Hérémence). In: . Retrieved May 13, 2015 .
  15. Technical documentation, p. 32
  16. Federal Office for Water Management (Ed.): Statistics of the hydropower plants in Switzerland . Bern August 1947, p. 213 .
  17. a b Chandoline hydropower plant. Alpiq Switzerland, accessed on May 13, 2015 .
  18. a b c Grande Dixence SA (Ed.): Decommissioning of the Fionnay and Nendaz power stations . Press release. November 17, 2016 ( [PDF]).
  19. Données de la centrale Fionnay (Dixence) . In: Office fédéral de l'energie OFEN (ed.): Statistique des aménagements hydroélectriques de la Suisse . January 1, 2019 ( ).
  20. Données de la centrale Nendaz . In: Office fédéral de l'energie OFEN (ed.): Statistique des aménagements hydroélectriques de la Suisse . January 1, 2019 ( ).
  21. Federal Office for Water Management (Ed.): Statistics of hydropower plants in Switzerland . 1st January 1973.
  22. Federal Office for Energy SFOE (Ed.): Statistics of the hydropower plants in Switzerland . January 1, 2018 ( [accessed October 31, 2019]). Statistics of the hydropower plants in Switzerland ( Memento of the original from December 9, 2018 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot /
  23. a b The most important hydropower plants in Switzerland. Federal Office of Energy SFOE, accessed on May 5, 2020 (2019 electricity production: 2201 GWh).
  24. Kernkraftwerk Gösgen-Däniken AG publishes annual report 2019. Kernkraftwerk Gösgen-Däniken AG, accessed on May 5, 2020 (Swiss Standard German).
  25. Switzerland: Electricity consumption will fall by 0.8% in 2019 despite positive economic and population growth. In: Retrieved May 5, 2020 .