Image Number 3 for United States Patent #6273639.
Method and apparatus for fish migration past dams and other water barriers. A preferred embodiment 100 comprises a conduit 101 passing from downstream side 22 of water barrier 10 to upstream side 21 of the barrier, flow-controlling valves 102 and 105 disposed in series within conduit 101, and actuators 103 for opening valves 102 and 105 in the presence of fish. Fish 30 are attracted by flow 130 passing through conduit 101 at controlled rates by means of flow-through devices in valves 102 and 105. On entering forechamber 104 and swimming upstream the fish pass actuators 103, which cause first valve 102 to open. As first valve 102 opens, water flow through conduit 101 remains controlled and substantially uniformly turbulent under action of second valve 105. With valve 102 open fish 30 may swim to mid-span section 140 of the conduit. When no further fish are present in forechamber 104 or passing actuators 103, or enough fish are present in section 140, the first valve closes. With valve 102 closed and fish passing actuators 103 in the direction of valve 105 in mid-span section 140, valve 105 opens. As valve 105 opens flow 130 through the conduit is controlled by now closed valve 102. Upon opening of valve 105 fish 31 are free to swim past valve 105 and exit conduit 101 through sally port 141, and to swim away from barrier 10 into upstream side 21 of waterway 20. Expanded sections 180 of conduit 101 are provided as rest stations for long transits against strong currents.