The Sigalda Station is located just above the Hrauneyjafoss Station, south of Lake Thórisvatn. The station came on-line in early 1978. A short tailrace canal links Sigalda Station with Hrauneyjafoss Station. Sigalda Station was built following the development at Búrfell. Its construction was a race against time as there was great demand for more hydropower stations to satisfy energy requirements in Iceland following the powerintensive industrial growth in Straumsvík and Hvalfjördur.
The Sigalda Dam dams the Tungnaá River at the top of the canyon above Sigalda Hill, where it forms Krókslón, a 14 km2 reservoir. The rock-fill dam is 925 m long, clad with asphalt, and 40 m tall at its highest point. The water is carried 1 km through an intake canal from Krókslón Reservoir to the western edge of Sigalda Hill. Three pressure shafts, 216 m long and 4.3 m in diameter, run to the powerhouse north of the old riverbed, in part buried inside the Sigalda hillside. The harnessed head is 74 m. A 550 m tailrace canal leads from the powerhouse into the Hrauneyjafoss Reservoir.
There are six hydropower stations in the catchment area of Rivers Thjórsá and Tungnaá: Búrfell, Sultartangi, Hrauneyjafoss, Vatnsfell, Sigalda and Búdarháls, with combined energy of 935 MW. Water for all the power stations is provided by three main reservoirs, Thórisvatn, Hágöngulón and Kvíslarveita, along with smaller reservoirs connected with each station.
Lake Thórisvatn, Iceland’s largest lake, is the largest reservoir and an important part of Landsvirkjun’s utility system. All water accumulated in Kvíslarveita and Hágöngulón reservoirs runs through Lake Thórisvatn.
Lake Thórisvatn became a reservoir with the harnessing of River Thjórsá at Búrfell Mountain in 1970-1972. River Kaldakvísl was diverted into the lake at the northern edge of the lake and a controlled outflow constructed at the southern edge.
A canal was dug from the lake and a concrete gate structure built in the canal to manage the flow rate. The canal is named the Vatnsfell Canal, and carries water from Lake Thórisvatn through the Vatnsfell Station into the Krókslón Reservoir above the Sigalda Station, and from there to other stations further down in the catchment area.
Work on the Kvíslaveita Reservoir began in 1980 and was completed in 1997. Kvíslaveita is the collective name for the dams, canals, bottom outlets and gate structures that manage the flow rate from the River Thjórsá and its tributaries into Lake Thórisvatn.
The Háganga Reservoir was constructed in 1997–1999 and covers an area of 27 km2. Its purpose is to increase the efficiency of the catchment area of River Kaldakvísl. During the summer months, water accumulates in the Hágöngulón Reservoir, with very little water flowing down the Kaldakvísl riverbed.
|Fyrsta vél gangsett:||1977|
|Vatnasvið virkjunar:||4.210 km2|
|Meðalrennsli til virkjunar:||154 m3/s|
|Virkjað rennsli:||240 m3/s|
|Afl hverfla af Francis gerð::||3 x 50 MW|
|Árleg orkuvinnsla:||650 GWst|
|Við lónhæð:||498 m y.s.|
|Hönnun:||Virkir hf og Electro-Watt Engineering Services Ltd., Sviss|
|Arkitekt:||Guðmundur Kr. Kristinsson|
|Vélar og rafbúnaður:||Brown Boveri & Cie, V-Þýskalandi, Energomachexport, Sovétríkjunum|
|Lokur og þrýstivatnspípur:||Sorefame, Portúgal|
|Helsti byggingaverktaki:||Energoprojekt, Júgóslavíu|