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 28^th 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.

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 16^th of September and the Jökulsár resource was utilised for electricity generation from that point onwards.

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.

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.