Kölnbrein Dam

Kölnbrein Dam
Location of Kölnbrein Dam in Austria
Official name	Kölnbreinsperre
Location	Malta, Carinthia, Austria
Coordinates	47°04′45″N 13°20′21″E / 47.07917°N 13.33917°E / 47.07917; 13.33917Coordinates: 47°04′45″N 13°20′21″E / 47.07917°N 13.33917°E / 47.07917; 13.33917
Status	In use
Construction began	1971
Opening date	1977
Dam and spillways
Type of dam	Concrete arch
Impounds	Malta River
Height	200 m (660 ft)
Length	626 m (2,054 ft)
Width (crest)	7.6 m (25 ft)
Width (base)	41 m (135 ft)
Dam volume	1,580,000 m3 (2,070,000 cu yd)
Reservoir
Total capacity	205,000,000 m3 (166,000 acre·ft)
Catchment area	129 km2 (50 sq mi)
Surface area	2.55 km2 (0.98 sq mi)
Power station
Operator(s)	Verbund AG
Commission date	1948-1979
Installed capacity	Upper stage: 120 MW (160,000 hp) Main stage: 730 MW (980,000 hp) Lower stage: 41 MW (55,000 hp) Reisseck plants: 137.5 MW (184,400 hp) Total: 1,028.5 MW (1,379,200 hp)
Annual generation	1,216 GWh (4,380 TJ)

The Kölnbrein Dam is an arch dam in the Hohe Tauern range within Carinthia, Austria. It was constructed between 1971 and 1979 and at 200 metres (660 ft) high, it is the tallest dam in Austria. The dam's reservoir serves as the primary storage in a three-stage pumped-storage power system that consists of nine dams, four hydroelectric power plants and a series of pipeline and . The complex is owned by Verbund power company and is referred to as the Malta-Reisseck Power Plant Group. The installed capacity of the group is 1,028.5 MW and its annual generation is 1,216 gigawatt-hours (4,380 TJ).

While the dam's reservoir was filling, several cracks appeared in the dam and it took more than a decade of repairs before the reservoir could operate at maximum levels. Currently, the Reisseck II pumped-storage power plant is under construction and will effectively connect both the Malta and Reisseck groups and add an additional 430 MW of production capacity.

Plans for the dam were already drafted in the late 1930s by the German AEG engineering company, when the Kaprun power plant was built north of the Alpine divide. The project was resumed by the Austrian authorities after World War II with extended exploratory drilling from 1957 onwards, nevertheless the construction of the Kölnbrein Dam did not begin until 1971.

Before cement and other construction materials could be moved on site, an access road had to be constructed. This proved difficult as the steep Malta Valley rises over 300 metres (980 ft) along a 14 kilometres (8.7 mi) stretch and at times has 13 percent gradients. To complete the road, six tunnels were excavated. In 1973, as superstructure construction progressed, cement was transported on site and mixed with aggregate from local sources. To reduce thermal expansion, concrete was poured 30 cubic metres (39 cu yd) at a time and pipes with circulating water were placed throughout the mass. The structure consisted of 30 columns with each joint grouted. Construction conditions high in the valley were not ideal as workers coped with snow and rain along with wind speeds of 80 kilometres per hour (50 mph; 43 kn).