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All construction work carried out by Landsvirkjun is accompanied by unavoidable disruption to the environment as the construction of power stations, transport of water and necessary manmade structures will have an effect on the ecosystem and the natural environment. Landsvirkjun operates 16 power stations in five areas of operation, all around the country. The Company carries out extensive monitoring and detailed research within the areas affected by its operations. The objective is to assess if and how operations affect the environment and to find solutions to reduce any effects.

The most extensive monitoring is carried out on aquatic ecosystems and birdlife alongside reindeer monitoring. The research is carried out in cooperation with the various universities, research institutes and independent specialists.

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Monitoring aquatic biota

Landsvirkjun extensively monitors the biota in lakes, reservoirs and rivers in the affected areas of all its power stations. The objective is to monitor any changes to the biota, in particular fish stocks. Extensive monitoring can facilitate the timely implementation of mitigation measures to reduce any environmental impact.

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Research on river biota in Þjórsá

Extensive baseline information is required at the initial stages of exploring any potential power project. This enables us to compare different project alternatives and mitigation measures thus minimising the environmental impact. Landsvirkjun has been responsible for research and preparation measures for the lower region of Þjórsá, below the Búrfell Hydropower Station, for years. Three power projects are being explored: Hvammur, Holt and Urriðafoss. All these potential projects have been categorised as “under consideration” by the Master Plan for Energy Resources in Iceland.

Landsvirkjun has monitored the biota of the Þjórsá River for years and extensive research has been carried out on fish stocks in the river since 1973. The Company has also been responsible for the release of fry and the construction of a fish ladder which has doubled the salmon migration area in the river.

Information on the migration and population of salmon in the lower region of Þjórsá must be collected before any potential power project is developed within the area. This information is an important factor in assessing the need for any mitigation measures required to minimise the environmental impact to the area. Design features include a juvenile fish bypass system, a fish ladder and fish-friendly turbines.

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    The juvenile fish bypass system is located above the intake structure of the power station, preventing juveniles from entering the turbines and being injured.
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    Water flows from the reservoir towards the intake and the top layer of incoming water (where juveniles are mostly found) floats into the juvenile fish bypass system. The juveniles are steered past the station and into the natural channel of the Þjórsa River.
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Research on aquatic biota

The preparation process for new power projects can take decades and includes extensive research on the potential environmental impact. Hydraulic modelling is a part of the process.

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Monitoring the salmon population

The Institute of Freshwater Fisheries has verified the correlation between angling numbers and the fish stock population in salmon fishing rivers used for angling. However, the Þjórsá River is mostly used for net fishing and there is no available data that shows the correlation between net fishing and fish stock population. The salmon population in the Þjórsá River is therefore unknown.

670 juveniles were tagged in the Kálfá River in an attempt to assess the total salmon population in the Þjórsá River.

Automatic fish counters are the most effective tool to assess the fish stock population in downward flowing water. The counter would be located a short distance from the estuary where all fish pass through on their migration up-river. However, the Þjórsa River has a high discharge and a long distance between the banks of the river which makes it difficult to install a conventional automatic fish counter. Landsvirkjun constructed a fish ladder by the Búðir Waterfall in 1991 which has an automatic counter. However, the fish ladder is located in an area far from the estuary and it is unclear what percentage of salmon pass through the fish ladder. Data from the counter can therefore not be utilised to assess the salmon population in the river.

The Institute of Freshwater Fisheries proposed that the salmon stock population in Þjórsá could be measured by tagging a certain number of juveniles as they migrate to the sea. The number of adult fish returning to the area would then be assessed a year later and the percentage of tagged and untagged fish caught or counted in the automatic fish counter in Kálfa would then be compared.

Tagging began in the Kálfá River in 2012 when 670 juveniles were tagged by inserting a steel marker into the snout of the fish and their adipose fin was clipped. Research has shown that the tags do not affect the juveniles and fin clipping does not affect their chances for survival.

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    A barrier and automatic fish counter were set up in Kálfá which is a tributary of Þjórsá. Tagging began in 2012.
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    Fish that pass through the counter are categorised as tagged or untagged via photograph.
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The barrier for the automatic fish counter covers the entire area between the river banks and fish are therefore directed to pass through the counter. Fish that pass through the counter are categorised as tagged or untagged via photograph. The salmon population in Þjórsá can be estimated once the total number of tagged and untagged fish swimming upstream in Kálfá has been assessed and total numbers for Þjórsá have been established.

Research on migration and the salmon stock population in Þjórsa is ongoing and is carried out under the auspices of the Institute of Freshwater Fisheries. A valid assessment of the salmon population is expected within a few years. There is hope that the relationship between net fishing and the fish stock population will become established enough to monitor any changes to the fish stock by analysing fishing figures from Þjórsá.

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Effects on habitat below the dam

Landsvirkjun has conducted extensive research on possible changes to natural water flow as a result of proposed power projects in the lower region of Þjórsá. Detailed knowledge of the flow regime below utilised areas is important as power station operations can affect both animal life and human life.

The water flow in the lower region of the river has changed extensively since power stations were constructed in the upper region of the river. Sediment deposition has decreased and better conditions have supported the growth of the salmon population, increasing fishing in the river.

The construction of proposed power stations in the lower region of Þjórsá would substantially decrease the water flow from the dam and until the water returns to its natural river channel.

If nothing is done then this would result in the contraction (narrowing) of the river and the river biota would suffer. Minimum water flow levels can be ensured by constructing levees on the river bed, spreading the water over a larger area of the river channel and therefore sustaining river biota.

River biota is diverse including everything from the primary production of bacteria and plants to benthic species, fish and birds. The entire ecosystem should be considered during the design and development of power stations as the food chain is sensitive. Landsvirkjun is considering options for water flow management in the river channel below the dams for the proposed power stations and through important salmon habitat areas in the lower region of Þjórsá. The objective is to sustain production in the area and to support a rich biota in an altered environment.