Studies in the Fishway Models

In order to conduct field experiments of fishways, scale models were constructed in Keminmaa and at the Kirakkakongas hydropower plant. The models were made for a fishway with vertical slots. The Kirakkakongas model was 30 m long with a vertical ascent of 2 m. The Keminmaa model was made on a scale of 1:4. The ascent behavior of fish was studied at discharges of 30-100 L/s. The depth of the basins was 30-60 m. The Keminmaa model allowed evaluation of different experimental designs, measuring equipment, and the methodology of fish behavior experiments. The Kirakkakongas model made it possible to carry out parallel and more detailed experiments. At Karakkakongas most fish swam up to the lower basin from the entrance downstream, in which the flow was strengthened by the flow from the lower channel. The flow velocity was 0.3-1.5 m/s, depending on the magnitude of the discharge used in the mouth of the fishway. In the Kirakkakongas fishway, fish swimming behavior was significantly affected by the temperature of the water and the flows in the basins and openings. At the lowest discharge (33 l/s), most fish swam up and at the highest (100 L/s) only a few swam up. At the lowest discharge it was possible to obtain flow conditions in the model in which whitefish of different sizes were able to swim without difficulty. The suitable flow rate greatly depends on the species for which the fishway has been designed. For trout and salmon the flow can be very strong but whitefish require a calmer flow. In the Keminmaa models the greatest proportion of the fish swam up the fishway when the water temperature was 16-19 C. The origin of the fish did not affect their rising activity. The best discharge for whitefish in this fishway model was 25-35 L/s. At lower discharges the whitefish also rose well. At discharges over 35 L/s, the swimming was uncontrolled and only a few whitefish were able to swim up. The rising activity of whitefish increased towards autumn, although the water was still warm. Fish swam up most actively in the mornin