The Hrauneyjafoss Station is Iceland’s third largest power plant, producing 210 MW. It is located near the Sprengisandur Route on the edge of the highlands; southwest of the Sigalda Station, and utilises the same water as Sigalda Station. Hrauneyjafoss Station came on-line in 1981.
The Tungnaá River is dammed on rather flat land approximately 1.5 km above the Hrauneyjafoss Waterfall and 7 km below the Sigalda Station. The difference in altitude is approximately 15 m. Hrauneyjalón, an 8.8 km² reservoir, was formed by the dam. A low soil wall dam stretches along the lava flatlands on the south bank of the river. A headrace channel runs 1 km northwards from the reservoir through a dip in the Fossalda Hill to an intake point at its northern edge. Three steel penstocks (4.8 m in diameter) run 272 m down the hill to the powerhouse. The tailrace canal, just over one kilometre in length, enters the Spordöldukvísl waterway, which runs into the Tungnaá River.
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:||1981|
|Vatnasvið virkjunar:||4.272 km2|
|Meðalrennsli til virkjunar:||155 m3/s|
|Virkjað rennsli:||280 m3/s|
|Afl Francis hverfla:||3 x 70 MW|
|Við lónhæð:||425 m y.s.|
|Hönnun:||Verkfræðistofa Sigurðar Thoroddsen hf. og Harza Engineering Company International, Bandaríkjunum|
|Arkitektar:||Guðmundur Kr. Kristinsson og Gunnlaugur Halldórsson|
|Vélar og rafbúnaður:||ASEA, Svíþjóð|
|Lokur og þrýstivatnspípur:||Magrini Galileo, Ítalíu.|