Planning and construction of compensative reproduction channels for salmonid fish (#75)
3 Constructing of new artificial reproduction habitats is one, though neglected, measure to compensate the adverse impacts of hydro power. The planning and construction of reproduction channels require an application of the preference conditions of the species in concern. In this paper the phases of constructing and evaluation of hydraulic circumstances of the totally new 1 km long reproduction channel in Imatra, Finland, constructed in 2014-2015, will be described. The artificial brook will be a habitat mainly for brown trout (Salmo trutta L.).
In the planning process the overall gradients of the channel were defined according to terrain, aiming for the maximum habitat area and quality within the area which was available. Sections with different gradients were chosen to enable construction of spawning sites and habitats for rearing and overwintering. 2D flow and habitat modeling was used to test what can be achieved by the plan with discharges 0,15 and 0,3 m3/s.
During the construction the plan was first accomplished roughly and then finalized by specialists of river restoration. The real gradients and hydraulic parameters of the channel, like velocities and water depths will be measured in 2015, to compare the channel with the ideas of the plan and the results of the modeling. The measurements will show the need for detailed guidelines for construction of similar channels.
Colonization of fish, invertebrates and plants will be monitored. The abundance of juveniles will be a criterion for promoting compensative habitats in further schemes.
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