Effects of modifications on the hydraulics of Denil fishways

From the biological point of view, fishways are structures that enable fish to continue their migration past obstructions. In terms of hydraulics, fishways are energy dissipating structures. One of the most effective fishways in energy dissipation is a Denil fishway. This paper presents the most important results of the studies on Denil fishways carried out at the Hydraulics and Water Resources Engineering Laboratory at the University of Oulu. The studies were focused on Denil fishways with wide relative baffle width (B/b = 2). Dimensionless discharges for Denil fishways with B/b = 2 are higher for the same water depth than for the standard Denil reflecting higher water velocities in the cross section. The dimensionless discharge curves for the standard Denil and for designs with different baffle angles are quite close to each other. The experiments show, however, clear trends in using different baffle angles to the bed.