Sultartangi Power Station

The Sultartangi Station, located 15 km northeast of the Búrfell Station, was built at the end of the last century and came on-line in 1999. The Station utilises water from the River Tungnaá which has already driven the turbines of the Hrauneyjafoss and Sigalda stations on its way down from the highlands. It also utilises the River Thjórsá’s flow rate, as the two rivers are joined in the Sultartangalón Reservoir above the station. As a result, it is not as sensitive to fluctuations in water supply as many other stations are. In this regard it resembles the Búrfell Station.

The Sultartangi Dam is the longest in Iceland, 6.1 km in length. In conjunction with the construction of the power station, the dam crest was raised by 1 meter, increasing the reservoir’s surface area from 18 to 20 km². A headrace tunnel (3.4 km) moves water from the reservoir through Sandafell Mountain to a surge basin on its southwestern side. At the end of the surge basin is the station intake, where two penstocks lead to the powerhouse. A tailrace canal, just over 7 km long, lies from the powerhouse at the foot of Sandafell Mountain and follows Thjórsá River almost all the way to the Búrfell Station Reservoir dam where it enters the Thjórsá riverbed.

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 1040 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 37 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.