The Sima Power Station, located south-west in the Sima Valley, utilizes water from two geographically separated areas and is in reality two power stations, Lang-Sima and Sy-Sima, which share the same machinery hall.
Lang Sima Power Plant
uses water which is stored in Rundavatn and Langavatn. Langavatn has 48m. of working storage. Both dams are retained by rockfill dams, gathering water from the rivers on the west side of the big glacier Hardangerjokulen. Langavatn gave rise to the name Lang-Sima.
Sy-Sima Power Plant
Water from Bjoreio and the south side of Hardanger jokulen is diverted to the main storage in Sysenvatn, where you now stand. Sysenvatn has 66 meters of working storage and a top water level 940m. above sea level. The water is retained by a rockfill dam and is among Norway’s biggest. A tunnel leads the water to the forebay Rembedaisval Sysenvatn gave rise to the name Sy-Sima
This drawing clear ly shows what is meant by „gathering water by the roof guttet principle. Highlying
water, in part behind dams, is network of natural river basins or artificial conduits tunnelled through the rock. The most important sluices and valves may be opened and shut by remote control either from the Station control room at Sima or the operating centre in Sauda. In this way it is possible to „store“ water until it is needed before releasing it down into the pover station turbines.
The Sysenvatn lake is retained by a rockfilI dam with an impervious, moraine core. The enormous weight of the rockfill keeps the reservoir water in place. Both sides of the watertight core are provided with filter zones of sand and gravel thus preventing the core from being washed away The huge quantities of stone used in the backfill on both sides we e collected in part from the tunnel operations nearby, and in part from reservoir areas now under water. The backfill is faced with large, placed stones.
Source: Information board on site