Introduction to Downstream Fish Passage at High Head Dams

High-head dams present immense challenges for fishery managers, engineering design teams, and stakeholders when considering downstream fish passage. The height of these dams, changes in river flows, and seasonal changes in reservoir elevations (sometimes greater than 35 m) are some of the most common challenges.  Downstream migrants must pass these high-head dams volitionally by way of turbines, where injury and mortality rates are usually high, or by regulating outlets and spillways.  Injury and mortality rates could also be an issue for fish passage through regulating outlets and spillways due to design and operations of the passage route and reservoir elevations.  Some high-head dams have surface collectors that utilize either transport or a system of bypass pipes as a means of passing fish safely, while others have none.  This presentation will introduce the audience of this symposium to the challenges and uncertainties of fish passage at high-head dams and the success of general solutions implemented or are in consideration.