Landsvirkjun operates 14 hydropower stations all over the country. Electricity generation is managed by steering the water supply from the reservoirs and into the power stations and by maximising the utilisation of the water in Company reservoirs.

Steering water resources in an isolated water system

The energy generation sector in Iceland is an isolated one and is not connected to any other systems. It is therefore of utmost importance that the water reserve in the reservoirs is substantial enough to ensure a secure supply of electricity. The water supply is, on average, 10% more than energy generation. Subsequently, 10% of the water supply to the reservoirs flows past the power stations and is not utilised for power generation. This has been the case for 15 years of the 17 years that have passed.

About 10% of the water supply to the reservoirs flows past the power stations in an average year.

The natural water cycle is utilised to generate electricity and the entire process is therefore heavily reliant upon weather conditions at any given time. Meltwater from the glaciers accumulates in the reservoirs during the summer months and the water is then utilised during the winter months. Electricity generation is managed by steering the water supply from the reservoirs and into the power stations. This maximises the utilisation of the water resource and prevents abnormal fluctuations in river channels and rapid changes to water levels in the reservoirs which can negatively affect the soil, ecosystem and society.

Steering the water resource prevents abnormal fluctuations in river channels and rapid changes to water levels in the reservoirs which can negatively affect the soil, ecosystem and society.

Landsvirkjun cooperates with specialists and local communities, in Landsvirkjun’s operational areas, to minimise water level fluctuations. Water steering measures within all of Landsvirkjun’s hydropower stations are carried out in accordance with Company procedures for established restrictions on the flow. There are also short-term restrictions on water flow with regard to salmon fishing and waterfalls.


The water resource in 2013

Landsvirkjun’s water budget was poor this year. Water reservoir levels were low by the end of winter and spring and the summer saw low temperatures and a dry climate. Approximately 600 Gl were needed in the reservoirs at the beginning of the winter period. The weather for the remainder of the year was unfavourable. As a result, almost no water went through the spillway.

The water inflow to Landsvirkjun’s reservoirs in 2013 was unlike that of previous years. There was high ‘snow melt’ in the water catchment areas in Þjórsá, Tungnaá and Blanda in February, most of the snow in the area thawed and the inflow rate was tenfold. Precipitation levels were low for the rest of the winter and there was no snow accumulation within the area. The spring floods were minimal as a result of these weather conditions and the meltwater was below average. Reservoirs did not fill in the Þjórsá, Tungnaá and Blanda water catchment areas.

There was a great deal of snow accumulation in the east of Iceland during the winter months and the spring period was initially cold. The lowest water level on record was recorded on the 28th of May at Hálslón; 570 m.a.s.l (55 metres below the highest operating water level). Temperatures rose at the beginning of June and the water flow increased in rivers and lakes in the eastern part of the country. The Hálslón Reservoir filled up towards the end of August and remained full for three weeks.


The estimated water yield for the operational year 2013 alongside real values for the year

The black line shows the estimated mean value and the red line shows the measured real values for the year. The shaded area shows the highest and lowest values. 


Cooperation with the tourism industry

The spring period was unusually cold in the east of Iceland in 2013. The operating permit for the Fljótsdalur Hydropower Station stipulates that Landsvirkjun must use the spillover from Ufsarlón in an efficient manner throughout the tourism period. The objective is to minimise the effect on a row of waterfalls in the area and to achieve the average water flow in the river channels of Jökulsár í Fljótsdal and Kelduá throughout July and August (during good water years). When the water budget is low then Landsvirkjun must place an emphasis on ensuring the water flow in the Jökulsár í Fljótsdal river channel and then in Kelduá (according to the available spillover water).

The low water level in the Hálslón Storage Reservoir meant that nearly all the available water from the Ufsarlón Reservoir was utilised and there was almost no spillover. This meant that there was only the natural inflow of water from rivers and springs in the Jökulsár í Fljótsdal river channel (below Ufsarlón). Water levels rose in the water catchment area in the beginning of June. The water flow went above average but then decreased again to below average levels.

This summer, Landsvirkjun cooperated with stakeholders in the tourism industry with regard to the water flow in the waterfalls in Fljótsdalur.

Water was sourced from the Ufsarlón Reservoir due to the unusually low water level at the Hálslón Storage Reservoir. This measure required cooperation with stakeholders in the tourism industry with regard to the water flow in the waterfalls in Fljótsdalur. Organised tours of the waterfalls took place for the first time and cooperative efforts were successful.

Annual sediment flushing measures were carried out in Ufsarlón at the end of August. The estimated amount of flushed sediment on an annual basis is 120,000 m3. The Hálslón Storage Reservoir filled on the 16th of September and the Jökulsár resource was utilised for electricity generation from that point onwards.


Water flow in Jökulsá í Fljótsdalur measured by the Hrakstrandarfoss Waterfall and Hól during the summers of 2012 and 2013

Hrakstrandarfoss is the highest waterfall in the row of waterfalls in Fljótsdalur.


Water flow in Jökulsá in Fljótsdalur; measured by Hrakstrandarfoss and Hóll


Glacier research carried out by Landsvirkjun

Landsvirkjun operates an extensive research and monitoring program for glaciers which provide runoff to the Company’s hydropower stations. The programme is run in cooperation with the Institute of Earth Sciences at the University of Iceland and has been active since 1981. Landsvirkjun has also worked in cooperation with the Glacier Research Society of Iceland (JÖRFÍ) since the mid-eighties.

The mass balance of the glaciers is measured on an annual basis, in order to assess surface accumulation and surface ablation. The results show that the glaciers, providing the water resources for Landsvirkjun, have in fact diminished in the last two decades and this is believed to be a direct result of climate change. The increase in glacial melt results in increased runoff to hydro power stations and therefore creates opportunities for increased and improved energy generation. Landsvirkjun is already accounting for ‘climate change impact’ in the development and design of potential power projects.

Measurements are carried out at the Vatnajökull and Langjökull Glaciers on an annual basis. The data is collected for further analysis. Measurements and research is focused on the basic properties of glaciers:

  • An assessment on the water resource/ice volume of the glacier
  • Measurements on summer, winter and annual mass balance, melt water runoff and surface ice flow
  • Measurements on surface features (topography measurements) and surface distribution
  • Measurements on long-term changes to ice volume and meltwater runoff
  • An assessment on the relationship between ablation, weather conditions and energy factors
  • Modelling of the movement and morphology of glaciers and past, present and future ablation from the glacier
  • An assessment of the flow pattern of water at the glacier margin and the transit time of meltwater to the glacier terminus
  • The development and improvement of ice flow models alongside research on unstable ice flow (e.g. glacier surges) causes and effects
  • Short-term predictions on glacier ablation levels

Extensive monitoring

Winter and summer ablation levels are measured at 23 monitoring stations on the Langjökull Glacier and at 50-60 stations on the Vatnajökull Glacier. Accurate elevation profile data is collected via driving expedition (on the glaciers) using a GPS navigation system. A 200-300 km distance is driven across Langjökull and a 1,000 km distance is driven across Vatnajökull, on an annual basis. The data is utilised to correct the elevation model (DEM) of the glacier and to assess the changes in elevation distribution. Probes have been set up to measure the horizontal and vertical movement at Tungnaárjökull and on the eastern side of Bruarjökull. This data is important for developing models for glacial ice flow.

Glacial ablation has been monitored for over twenty years and the data shows substantial variability between years (measurements can double). The greatest variable can be seen at Hálslón where snowfall during summer can substantially reduce ablation levels. Ash from volcanic eruptions and sand encroachment from highland areas can also affect ablation.


Landsvirkjun’s power stations: Main reservoirs and glaciers


Measured average water flow to the main reservoirs as a result of glacial ablation

The average water flow is shown since ablation monitoring began but summer precipitation levels; precipitation levels and ablation outside the glacier and contributions from the groundwater reservoir are not included.


Weather stations at Langjökull and Vatnajökull collect data on temperature, humidity, precipitation, wind velocity, wind direction and solar and temperature radiation to and from the surface. The weather stations provide important real-time data which increases the validity of assessments on ablation levels.

Ablation monitoring is carried out on an annual basis, as well as various research projects and modelling development, mostly based on data collected during glacier-measuring trips. These trips increase knowledge on glacier behaviour, the changes over time and help to predict future behaviour.


Measurements on air temperature, the total radiation leading to ablation and snow levels by the weather monitoring station at the Tungnaá Glacier in the summer of 2013

The temperature was below freezing in May and there was no ablation. The temperature increased in May/June and radiation providing melt energy increased. Winter snow and glacial ice also began to melt and these levels remained stable until the middle of August. The average temperature and total radiation decreased after this. The summer of 2013 was rather cold and ablation levels were low.


Surges at the Brúarjökull Glacier

Surge at the Brúarjökull Glacier. The last surge was approx. 9 km between 1963 and 1964.

Brúarjökull is a surge-type glacier, like most of the larger outlet glaciers of Vatnajökull. Brúarjökull has surged every eighty years or so, the last surge was approx. 9 km between 1963 and 1964, and it is therefore likely to surge again before the middle of this century. The elevation distribution of the glacier is altered dramatically by a surge; it can decrease by 50 metres in accumulation areas (upper section of the glacier) and the ablation area (lower section of the glacier) can surge forward by anything from a couple of hundred metres and up to ten kilometres. This lowers the average height of the glacier, its total surface area increases and ablation increases (ablation can increase by many tens of percent in the first few years after a surge).

Knowledge on the nature of surges (such as their timing) is limited and this is one of the most significant problems in developing calculation models for glacier movement. If Brúarjökull surges in the near future it could enter the innermost area of Hálslón and could temporarily affect the storage capacity of the reservoir.

Older data is being analysed in an attempt to further increase knowledge on glacial surges, as well as the collection of new data. Elevation measurements and ice flow measurements have been conducted during the spring and autumn period in Brúarjökull since 1992. Ice flow measurements have been carried out continuously in some areas for the last few years. This data provides important information on the movement area of the glacier and its connection to the variable flow rate at the bottom of the glacier. Ablation measurement data from monitoring stations alongside elevation measurements supports the analysis of the vertical velocity of the ice sheet in order to assess mass accumulation in the upper section of the glacier.