Hálslón Reservoir, Kárahnjúkastífla Dam left
|Primary inflows||Jökulsá á Dal River - 107 m3/s (3,800 cu ft/s)|
|Primary outflows||Jökulsá á Dal River & Jökulsá í Fljótsdal River|
|Catchment area||1,806 square kilometres (446,000 acres)|
|Max. length||25 km (16 mi)|
|Water volume||2,100×106 m3 (74×109 cu ft) (live)|
|Surface elevation||575–625 m (1,886–2,051 ft)|
The Hálslón Reservoir is a storage reservoir in Eastern Iceland on the Jökulsá á Dal River. The reservoir stores water for use in hydroelectricity production with the Kárahnjúkar Hydropower Project. The reservoir was formed by three different concrete-face, rock-fill embankment dam dams; Kárahnjúkastífla Dam, the Desjarárstífla Dam and the Sauðárdalsstífla Dam.
The Kárahnjúkastífla Dam is 193m tall, 730m long and straddles the river. It is made of 8.5 million cubic meters of material making it the largest dam of its type in Europe. Construction on the dam began in April 2003 and was completed in November 2006. The Kárahnjúkastífla Dam does not create the reservoir alone as the dam is higher in elevation than two valleys that flank the river valley. To create the desired level, axillary or saddle dams were built. The 60m tall and 1,000m long Desjarárstífla Dam is adjacent and to the east of the Kárahnjúkastífla Dam. The Sauðárdalsstífla Dam is 4 km to the southwest, 25m tall and 1,100m long. Both auxiliary dams were built between April 2004 and October 2006. The reservoir began to fill in September 2006.
Water used for hydroelectricity production in the reservoir is discharged in the Jökulsá í Fljótsdal River to the northeast.