Hydrology

Hjartdøla river will freeze more often during the winter than is currently the case. The water downstream of the power plant outlet will have greater temperature variations throughout the day than is currently the case, in summertime as well as winter. The average daily temperature downstream of the power plant will change somewhat: it will be slightly higher in winter and slightly lower in summer.
Between the power plant outlet and Heddalsvatn lake, variable freezing conditions will occur. The river will therefore mainly run freely, except for in still, deep sections closest to Heddalsvatn lake.
In Skogsåa river, no significant changes in temperature conditions are expected. However, the river could freeze a few days earlier as a result of lower water volume.
Small changes are expected in the temperature and freezing conditions of Hjartsjåvatn, Sønderlandsvatn and their side streams.

Reduced flow in Hjartdøla and Heddøla rivers will reduce the ground water level closest to the rivers. The changes will be most obvious in the area where the ground water level increased following the establishment of Hjartdøla Power Plant and the occurrence of ‘water-sick soil’.
During the construction phase, it is inevitable that the municipal waterworks and a few private wells will be temporarily affected. Necessary measures will be implemented to secure the water supply.

Recipient conditions downstream of the municipal treatment plant’s outlet will change after Sauland Power Plant is built. The water quality and recipient conditions are expected to remain good/satisfactory following the potential construction of Sauland Power Plant. It is unlikely that the development of Sauland Power Plant will affect the potential for utilising geothermal energy.

The environmental impact assessments were carried out by Norconsult, the Norwegian Meteorological Institute and the Norwegian Water Resources and Energy Directorate.

The construction of Hjartdøla Power Plant resulted in several days of sea smoke along Hjartdøla river. After the construction phase of Sauland Power Plant, it is expected that sea smoke will be a rare occurrence. Otherwise, the development will have very little affect on the climate.

Lower flow reduces the potential for erosion of the rivers. Erosion processes will continue to occur in the future, but on a smaller scale than today.