Karahnjúkar Hydroelectric Power Station

The Kárahnjúkar Hydroelectric Power Station is located in eastern Iceland. The plant produces electricity for Alcoa’s aluminum smelter in Reydarfjordur. Kárahnjúkar is the largest power plant in Iceland with a capacity of 690 MW. The plant harnesses two glacial rivers, and the complex comprises a rockfill dam as well as several smaller dams, an underground power station and two 400 kV transmission lines, each approximately 50 km long.

Technical data:

  • Installed capacity: 690 MW
  • Turbines: 6 Francis units, vertical axis
  • Rated capacity: Discharge of 144 m/s at a power of 690 MW
  • Gross head: Max gross head of 599 m
  • Karahnjukar dam: Length 700 m; height 198 m
  • Water reservoir: Halslon reservoir; 625 - 575 m.a.s.l.; storage
  • capacity of 2100 million m³
  • Headrace tunnel: 40 km, ø7.2-7.6 m
  • Other tunnels: 11 tunnels totaling 32 km in length, ø6.5-9.0 m
  • Pressure shafts: 2 vertical pressure shafts; ø3.4 m; length 400 m
  • Generating capacity: Approximately 4600 GWh/year

Rolle

  • Site investigation
  • EIA report
  • Civil works design of diversions (dams and tunnels)
  • Structural and mechanical design for diversions
  • Cost estimates
  • Tender documents and evaluation of tenders
  • Project planning
  • Testing and start-up
  • Commissioning
  • Site supervision of power station 
  • Pre-design and site supervision of the 400 kV transmission lines
599
Gross head
2100 million/m³ 
Reservoir capacity
4600 GWh 
Generation capacity

The plant is owned and operated by Landsvirkjun. Construction work at Kárahnjúkar began in 2003 until the Fljótsdalur Power Station reached full operational capacity in 2007. The River Jökulsá á Dal is dammed at Fremri Kárahnjúkar with the largest of the Kárahnjúkar dams. Two smaller saddle dams were built at Kárahnjúkar, Desjará dam to the east and Saudárdalur dam to the west. Together, the three dams form the Hálslón Reservoir which covers an area of 57 km². Kárahnjúkar dam is the tallest concrete-faced rockfill dam in Europe and among the largest of its kind in the world. In the powerhouse, which is located underground, the water drives six Francis turbines and then flows through a tailrace tunnel and canal into the river Jökulsá in Fljótsdalur.