Fiskeløysen is the uppermost reservoir in the Gjuva and Vrengja watercourse system. The reservoir has three small dams – one main dam and two retaining dams. The main dam consists of three sections: a mid-section and two sections connecting the dam and the shore. The mid-section is a special steel and timber construction called a steel trestle dam. The southern connecting section is a rock-fill dam and the northern connecting section is a concrete dam. The two retaining dams are rock-fill dams. The dams were built in the 1960s, but needed to be reinforced to comply with new official requirements.

What work was done

The rock-fill dams were reinforced with rock. The main dam’s steel trestle construction was removed and replaced by a new concrete dam. The retaining dams were reinforced. The overfall weir was of the same length and contour height as the previous dam (788.00 metres above sea level).

Unchanged regulation

The highest and lowest regulated water level (HRV and LRV) in the reservoir will remain the same as before the modification work.