USGS Home
Contact USGS
Search USGS

Search fish passage bibliography

Grande, R. and D. Matzow (1998). A new type of fishway in Norway: how a regulated and acidified river was restored. Pages 236-245 in M. Jungwirth, S. Schmutz and S. Weiss, eds. Fish Migration and Fish Bypasses, Fishing News Books, Vienna (Austria).

To reduce the negative effects of a hydroelectric plant, a fish pass Facility was constructed at Rygenefossen, a 23 m-high waterfall on the Nidelva River at Arendal. The power plant, with a 6 m-high dam, is located on the upper portion of the waterhall. The fishway consists of a pool-and-weir pass in the lower part of the waterfall, linked to a pressure-chamber fishway (a kind of fish lock) in the dam. Between the dam and the powerhouse downstream, there is a 2 km-long residual flow stretch. Fishways were also built at three weirs within this residual flow stretch. The pressure-chamber fishway is new for Norway. Fish swim into a chamber at the base of the dam and when a sufficient number have entered, a diffuser closes and the pressure is increased to equal that found upstream of the dam. Another diffuser opens giving the fish access to a duct leading to the river above the waterfall. The system was constructed to take Atlantic salmon Salmo salar and sea-run brown trout S. trutta past the dam. Four years of trials have given positive results. This chapter describes the construction of this pressure-chamber fishway, how it works and our operating experience so far.