3.3. Studies at the water outlet of fish passage models

Studies on the hydraulic conditions at the water outlet of a fish passage facility were carried out in the experimental hall of the Water Resources and Environmental Engineering Laboratory, University of Oulu, Finland in 1999. These studies were performed in a flume with one wall made of transparent polycarbonate plates. The other walls and the studied designs were made of plywood. The fishway model was applied as a separate element inside the 600 mm-wide flume (Fig. 12). In all the experiments, the total flume width was 600 mm (Fig. 13). The width of the fishway model flume was 240 mm for all the designs, the slope for pool-and-weir and vertical slot fishways was 1:10 and for the Denil fishway 1:5. The studies were made with different discharges.

Water was pumped from the collection tank into the equalizing flume and conducted from there into the model and back into the collection tank. Discharges were controlled by valves and determined by a Thompson weir with an electric head meter. Upper and lower water levels were set in such a way that the drop at every weir was the same and there was no backwater or drawdown effect. The fishway discharged into standing water.

Water depths and velocities were measured in the centerline of the flume, except for the vertical slot entrance. Water depths were measured from the bottom of the flume by using a ruler. Time averaged velocities were measured vertically by using a current meter with a propeller of 8 mm, surrounded by an external ring with a diameter of 11 mm.