The Grande Dixence Dam is a concrete gravity dam on the Dixence River at the head of the Val d'Hérens in the canton of Valais in Switzerland. At 285 m (935 ft) high, it is the tallest gravity dam in the world and is part of the Cleuson-Dixence Complex. With the primary purpose of hydroelectric power generation, the dam fuels four power stations, totaling the installed capacity to 2,069 MW, generating approximately 2,000 GWh annually, enough to power 400,000 Swiss households.

The dam withholds Lac des Dix (Lake Dix), its pumped-storage reservoir. The reservoir receives its water from four different pumping stations; the Z’Mutt, Stafel, Ferpècle and Arolla. At peak capacity, it contains approximately 400,000,000 m3 (1.4×1010 cu ft) of water, with depths reaching up to 284 m (932 ft). Construction on the dam began in 1950 and was completed in 1964, before officially commissioning in 1965.

Chandoline Hydroelectric Power Station

The Chandoline Hydroelectric Power Station was the power station for the original Dixence Dam. The Grande Dixence Dam submerged the original dam but the power station still operates with water received from the reservoir of the Grande Dixence Dam, Lac des Dix. The power station is the smallest of the four, producing 120 MW from five pelton turbines with a gross head of 1,748 m (5,735 ft).

Fionnay Hydroelectric Power Station

The Fionnay Hydroelectric Power Station receives water from the Grande Dixence Dam by a 9 km (6 mi) long tunnel with an average gradient of 10%. Once the tunnel reaches a surge chamber at Louvie in Bagnes, it turns into a penstock which descends at a gradient of 73% for 800 m (2,625 ft) until it reaches the power station. The water, now flowing at a maximum rate of 45 m3/s (1,589 cu ft/s) spins six pelton turbines, generating a combined maximum capacity of 290 MW.

Nendaz Power Station

After arriving at the Fionnay Power Station from the Grande Dixence Dam, water then travels through a 16 km (10 mi) pressure tunnel which eventually leads into the Péroua surge chamber, 1,000 m (3,281 ft) above the Nendaz Power Station. The water, which remains at a maximum rate of 45 m3/s (1,589 cu ft/s) spins six pelton turbines, generating a combined maximum capacity of 390 MW.

The Nendaz power station is located within mountains between Aproz and Riddes and is the second-largest hydroelectric power station in Switzerland after the Bieudron Power Station.

Bieudron Hydroelectric Power Station

The water travels down a long penstock from the Grande Dixence Dam before reaching the Bieudron Hydroelectric Power Station 1,883 m (6,178 ft) down. The water spins three pelton turbines, generating a combined capacity of 1,269 MW. The power station was constructed after the Nendaz and Fionnay power stations. The power station was built by both Grande Dixence SA and Energie Ouest Suisse between 1993 and 1998 at a cost of US$1.2 billion.

The Bieudron Power Station alone holds three world records, for the height of its head (1,883 m (6,178 ft)), the output of each Pelton turbine (3 × 423 MW) and the output per pole of the generators (35.7 MVA). It was taken out of service in December 2000 after the rupture of a penstock. The power station became partially operational in December 2009 and should be fully operational in 2010.

Grande Dixence Dam
Locale Hérémence, Switzerland
Coordinates 46°04′50″N 07°24′14″E / 46.08056°N 7.40389°E / 46.08056; 7.40389 / 46.08056; 7.40389
Construction began 1953
Opening date 1964
Dam and spillways
Type of dam Gravity dam
Height 285 m (935 ft)
Length 700 m (2,297 ft)
Base width 200 m (656 ft)
Volume 6,000,000 m3 (210,000,000 cu ft)
Impounds Dixence River
Creates Lac des Dix
Capacity 400,000,000 m3 (1.4×1010 cu ft)
Catchment area 46 km2 (18 sq mi)
Surface area 4 km2 (2 sq mi)
Max. water depth 284 m (932 ft)
Power station
Commission date 1965
Type Yes
Installed capacity 2,069 MW
Annual generation 2,000 GWh