Kárahnjúkar Power Plant is by far the largest power plant in Iceland and the largest construction project ever undertaken in the nation's history. The plant has a power output of 690 MW, which is similar to the combined output of all the power plants in the rivers Þjórsá and Tungnaá.
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Kárahnjúkar Dam

River Jökulsá in Dalur
- Kárahnjúkar Dam
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- Harnessed
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Kárahnjúkar and the "Grandest Plan"
Hafrahvammagljúfur canyon was among the natural phenomena that disappeared with the construction of the Kárahnjúkar Dam and now lies submerged at the northern end of the Hálslón reservoir. The Kárahnjúkar Power Plant is by far the largest construction project in Icelandic history. With a power output of 690 MW, the plant generates as much energy as all the power plants in the rivers Þjórsá and Tungnaá combined.
The plant harnesses the flow of two glacial rivers at the same time. Water from the rivers Jökulsá á Dal and Jökulsá í Fljótsdal is diverted into a tunnel at Valþjófsstaðafjall mountain in Fljótsdalur. The tunnel runs 70 km at 500 m above sea level before reaching a shaft where the water plummets into station facilities at 30 m above sea level.
Dams east of Snæfell mountain are used to divert the water of the river Jökulsá í Fljótsdal to the station facilities, whence they are rediverted back to the river course.
Three large dams at Kárahnjúkar divert the water of the river Jökulsá á Dal along with that of its powerful tributary, the river Kringilsá, 40 km to the river Jökulsá í Fljótsdal and the 57 km2 Hálslón reservoir.
In its initial conception, the Kárahnjúkar Power Plant formed part of an even bigger plan that involved harnessing the flow of the river Jökulsá á Fjöllum by diverting its flow, too, into the Hálslón reservoir. This plan was nicknamed the "Grandest Plan" (Lang-Stærsti Draumurinn in Icelandic, abbreviated LSD). A similar plan was being considered for the Norway Highlands, but came to nothing due to environmental impact, which would nevertheless have fallen short of that in the northern Iceland Highlands.
Both of these grandiose schemes aimed to harness the immense energy potential of rivers at high altitudes.
Shortly after construction started at Kárahnjúkar, it was revealed in the 1st phase of the Master Plan for Hydro and Geothermal Energy Resources that the Kárahnjúkar Power Proposal was one of the two proposals with the most environmental impact, the other being the damming of the river Jökulsá á Fjöllum.
Despite this, there is pressure from hydroelectricity enthusiasts for the construction of the so-called Helmingur Power Plant which would entail the exploitation of the river Jökulsá á Fjöllum in a similar way to that outlined in the "Grandest Plan".
The Kárahnjúkar Power Plant is an excellent example of the high-risk speculative mentality that dominated the Icelandic economy in the period 2002-2008. A lawyer at Landsvirkjun let it drop that the proposal was "a difficult and risky endeavor geographically, technologically, environmentally and economically,... an isolated case in the energy sector…".
It was not immediately apparent whether it would be viable to dig a waterproof tunnel through an intervening 6-7 km stretch of fault lines. However, research on the feasibility of the tunnel was purposefully not carried out, as this part of the construction was only to be carried out towards the end of the project.
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The Power Plant and its impact
Everything about the Kárahnjúkavirkjun Power Plant is large in scale.
It provides energy for Iceland‘s largest aluminum processing plant.
Iceland‘s four largest dams form part of the complex, and the largest, the Kárahnjúkar Dam, is the largest dam of its kind in Europe, 185 m in height and weighing 10 million tons.
The water level in the Hálslón reservoir varies more, and also more rapidly, than in any other known reservoir. The difference can be up to 70 m, as waterflow into the reservoir is one hundred times greater in August than it is in February.
Ten million tons of fine clay is carried into the reservoir every year. Its waters are so muddy that visibility is only 2 cm, and they cannot sustain life.
Judging from observations of sedimentation in the last few decades, the reservoir is estimated to fill up with sand and clay in 400 years. However, signs at the outflow of the river Kringilsá suggest that, due to global warming and the increased rate of melting ice in the Brúarjökull glacier, the reservoir might fill up much more rapidly than previously thought, thus rendering the reservoir useless and creating a terrain of mudflats instead of the deep valley of Hjalladalur.
In early summer, much of the Hálslón reservoir consists of dry mudflats of new clay. In windy weather, the resulting silt storms make the area uninhabitable, just when the weather is at its warmest and most pleasant.
So much clay is carried over from the reservoir to the river Lagarfljót that the river has cooled considerably and lost its distinctive blue for a new brownish hue. Fish populations in the river and its tributaries have dwindled.
Approximately 40 km² of terrain supporting vegetation was submerged when the Hálslón and Kelduárlón reservoirs were created. Most of this land consisted of a layer of soil several meters thick. Its submersion destroyed more soil in one go than any other human activity in Iceland‘s history.
The Hálslón reservoir gets its name from Hálsinn, a 15 km arched ridge considered one of the gems of the Iceland Highlands, with some excellent land for pasture, that disappeared under the waters of the reservoir.
The reservoir also drowned Hjalladalur, the deepest and most sheltered valley in the northern highlands, and therefore an important breeding ground for reindeer in spring. The valley also contained some of the most spectacular sedimentary rock formations in Iceland.
Due to the great quantities of clay and sand it carried out to sea, the river Jökla was Iceland‘s most efficient glacial river when it came to creating new land formations and natural wonders.
The river carved out the greater part of Iceland‘s greatest river canyon system, Hafrahvammagljúfur, in only 700-800 years, and was already working on forming colorful new canyons full of rock formations and river rapids at the bottom of Hjalladalur valley in under a century, when the whole valley was submerged.
The river Jökla kept the Hafrahvammagljúfur canyons clean due to constant sand abrasion, but now that the river‘s course has been diverted away from the canyons, they will gradually fill with rock falling into them. Claims that the canyons have become more accessible now that they have been dried up are therefore groundless. It has besides always been possible to access the canyons via the so-called Niðurgöngugil (literally "descent canyon").
Dozens of waterfalls dried up as a consequence of the Kárahnjúkar project, three of which were among Iceland‘s "eleven great waterfalls". Two of the three were adjacent waterfalls in the river Jökulsá í Fljótsdal, and their height equalled that of the famous Gullfoss waterfall.
Töfrafoss waterfall, also named Kringilsárfoss waterfall, was the largest waterfall in the Iceland Highlands west of Snæfell mountain.
Adequate research into whether the Kárahnjúkar project may affect the area‘s volcanic system does not seem to have been carried out before construction began.
Grímur Björnsson, geophysicist at Iceland GeoSurvey, early on pointed out the lack of research carried out by the authorities concerning environmental issues before starting construction of the power plant. Neglected areas included research into the plant‘s effect on scenery, geological subsidence, volcanic activity and the ocean. He expressed concerns that such a large power plant constructed in a volcanically active area could hardly meet adequate security standards and thus posed a significant danger.
The visual impact is considerable. The power plant facilities are visible from all major scenic spots in Iceland‘s northeastern Highlands.
Photo © Sóley Stefánsdóttir
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The Power Plant Debate – For and Against
The Kárahnjúkar Power Plant was the focus of a heated and bitter debate that split the Icelandic nation into two opposing factions.
As part of the plant‘s construction, Folavatn lake east of Snæfell mountain was submerged to create the muddy Kelduárlón reservoir for the Hraunveita diversion. Swans nested in great numbers around the lake. Many proponents of the power plant argued that the area to be submerged was not well known, and that therefore its value was low and needed not be taken into account.
Proponents of the plant considered its construction the only viable option to breathe new life into the communities and economy of East Iceland, which were in decline and had waited for this opportunity for too long already.
The project was considered likely to create a lot of jobs, revenue and infrastructure for the region, and that the population of central East Iceland would permanently increase by 1500. An estimated 80% of the workforce needed for the plant‘s construction would be Icelanders and 20% foreigners, and so unemployment in the region would be eliminated.
The nation‘s export revenues were expected to rise significantly with the advent of the power plant.
New roads were meant to make the area more accessible and so render it suitable for development as a tourist spot. Attractions were to include sailing on the reservoirs and other outdoor activities in the vicinity of the dams.
Erosion and silt storms from the reservoir‘s dry bed in early summer were to be prevented with methods such as the use of dust binding chemicals dropped by airplanes.
Opponents of the proposal argued that it would entail unprecedented and irreversible defilement of nature and irremediable damage to the environment to the detriment of future generations.
They argued that such a megalomanic project would drain capital from other sectors of the economy, resulting in an orgy of investment and construction, which would in turn result in a slump once construction was finished.
Unemployment would not be reduced when all the jobs on offer were in the same sector.
Promoting the area as a national park of unique natural treasures and developing it systematically for tourism would result in greater, more widespread and more permanent community growth in the region than power projects, they claimed. It was wrong not to place any value on the natural scenery being sacrificed, many examples from abroad could demonstrate that.
Gross domestic product would only rise by 2%, and tax revenues generated would be but a third of those in the fishing and tourism industries.
Profits from the project would be too low, and a large portion thereof would go abroad.
Tourists would not find the dam area attractive for outdoor recreation, due to the blighted landscape and unceasing silt storms in early summer.
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Economy and Society
The silt storms that rise from the dry bed of the Hálslón reservoir in early summer have proven uncontrollable, rendering the area utterly inhospitable whenever winds pick up, in the very season when weather conditions are ideal, sunny and dry.
Predictions about boat sailing on the reservoir and other outdoor activities after the construction of the power plant have not become reality.
It has also become clear that domestic profits from heavy industry construction projects have been insignificant, even if the value of natural wonders destroyed in the process is not taken into consideration.
The CEO of Landsvirkjun has revealed in the media that the profitability of the Kárahnjúkar Power Plant is not satisfactory, and that the Icelandic nation has not benefited adequately from the project and its operation.
Some population growth has been witnessed in the local community of Fjarðabyggð, as well as in the vicinity of the new aluminum processing plant in Reyðarfjörður. Nevertheless, empty houses and apartment buildings – built in more optimistic times – are commonplace in the area.