Varegrinder foran turbininntak ved elvekraftverk; barrierer eller inngangsport for fisk?

Abstract

Trash racks at hydropower turbine intakes; barriers or entry gates for fish? At all run-ofriver hydro power plants, water is diverted through turbines for power generation. Trash racks protect the turbines from harmful debris. The spacing between the trash rack elements usually reflects operational considerations, and rarely fish protection. The mortality inflicted on fish passing the turbines varies between 5 % and 100 %, depending on turbine design. Trash racks will protect migrating fish if the element spacing is no more than 7 % -10 % of the fish length. If the spacing is greater than this, alternative downstream migration routes should be established alongside the trash racks. Trash racks should be angled 20-45 degrees in the vertical as well as the horizontal plane, and thereby increase the retention period of fish and increase the probability of locating an alternative migration route. Installation of an angular fish deflector reaching at least 3-5 m deep in the forebay basin will divert the fish towards alternative downstream routes for fish.