Landsvirkjun is committed to utilising natural resources in the most efficient manner and to reduce the emission of pollutants into the environment. Landsvirkjun operates two geothermal power stations at Krafla and Bjarnarflag and monitoring on the effects of run-off water from the stations is carried out on an annual basis.
Run-off water from geothermal stations
Run-off water (condensate and separated water) contains heavy metals and nutrients which mostly originate from geothermal fluid. They are also present as a result of the corrosion of equipment. The natural concentration of these chemicals varies between areas and is, amongst other things, reliant on the chemical composition of groundwater and volcanic activity. If concentration levels are too high then they can affect the ecosystem. These environmental effects can be reduced by re-injecting run-off water into the geothermal reservoir. However, surface disposal is sometimes essential.
Re-injection keeps up the pressure levels in the geothermal system, therefore reducing environmental impact.
Separated water at the Krafla Geothermal Station is partly re-injected back into the geothermal reservoir. The objective of re-injection is to keep up the pressure levels in the geothermal system, therefore reducing the environmental impact. Separated water from the Bjarnarflag Geothermal Station is disposed of at the surface into the Bjarnarflag Reservoir and is channelled into the groundwater via a fissure in the western end of the reservoir. The chemical composition of the geothermal fluid is measured annually in all boreholes and in certain processing areas. More information on surface disposal from geothermal stations in the last five years can be found in the numerical data section.
According to the operating permit, the run- off water at Krafla and Bjarnarflag can be disposed of at the surface if the resulting concentration of pollutants in the groundwater flow is under Environmental Limit 1 once it reaches Mývatn. The limits are outlined in regulation no. 796/1999 for the prevention of water pollution. Measurements are carried out annually on the groundwater in Mývatn to monitor the effects of run-off water from Krafla and Bjarnarflag. Monitoring of the groundwater in the Kelduhverfi area and at Þeistareykir began in 2007 with the purpose of accumulating basic data for potential geothermal projects in the area. The data can be used to identify the chemical composition of groundwater under natural conditions, before utilisation.
Measurements are carried out annually on the groundwater in Mývatn to monitor the effects of run-off water from Krafla and Bjarnarflag.
Monitoring the groundwater system requires the collection of samples at designated collection sites. The concentration of chemicals normally found in geothermal fluid, such as arsenic, is measured. Conditions within geothermal areas are volatile by nature, due to volcanic and seismic activity and the utilisation of the geothermal system. Measurements are therefore conducted alongside mapping and research on geothermal activity. A report on these results is sent annually to the Public Health Authority in the northeast of Iceland and to the Icelandic Environment Agency. If any deviations or unexpected results are recorded then monitoring measures are reviewed.
Groundwater flow and sampling stations monitoring the chemical composition of excess water from the Krafla and Bjarnarflag Stations
Main results of monitoring on geothermal areas and groundwater in high temperature fields in Mývatn and the Kelduhverfi area between 2012 and 2013:
- Monitoring in 2012 and 2013 showed no extensive changes to geothermal activity when compared with previous years.
- Results on the monitoring of solutes in groundwater between 1997 and 2013 show that water in the springs by Mývatn and in the groundwater to the west of the Námafjall Mountain has not been affected by the geothermal water from the Bjarnarflag or Krafla Stations with regard to the concentration of arsenic and aluminium.
- The concentration of mercury is under or at the detection limit and well within environmental limits at all monitoring stations.
- The concentration of arsenic was below environmental limits at the monitoring stations in Langivogur and Vogaflói in 2012 and 2013.
Concentration of arsenic in groundwater samples by Vogaflóa and Langavogur 1997-2013
The figure shows that arsenic concentration levels are below environmental limits every year.
Effects of geothermal utilisation on groundwater at Bjarnarflag
The inflow at Mývatn is mostly groundwater which flows from all directions until it reaches the lake. The flow is mostly from the southern end and part of the groundwater is heated up by the geothermal system in the Námafjall Mountain, mixing with geothermal water from this source and from Krafla.
Simplified model of the groundwater system at the eastern end of Mývatn. Source: ÍSOR.
Monitoring on the effects of geothermal utilisation in Bjarnarflag has been ongoing in one form or another for over 40 years or since drilling began in 1963. An extensive report was released on the effect of geothermal utilisation at Bjarnarflag on the warm groundwater flow to Mývatn in 2013. The main results were as follows:
- Model calculations show that the warm groundwater flowing to Ytriflói amounts to approximately 11 m3/s, whereas the cold groundwater entering Syðriflói is approx. 17m3/s.
- Extensive changes took place within the groundwater system in Lake Mývatn as a result of volcanic activity and movements in fissure swarms during the Krafla Fires 1975 to 1984 and the Mývatn Fires 1724 to 1729. The temperature of the groundwater increased and the chemistry changed accordingly.
- Based on the chemistry and the isotopic composition of the cold and warm groundwater it is proposed that the warm groundwater is only partly derived by steam heating but mainly derived by mixing with geothermal water from the Krafla geothermal system.
- The percentage of deuterium, chlorine (Cl) and boron (B) in groundwater indicates that geothermal fluid that has mixed with groundwater originates from the Krafla Geothermal System.
Decades of monitoring have not shown any negative effects on Mývatn from current power operations in the area or from the run-off water from the potential power project in Bjarnarflag which will be re-injected.