Fish Deterrence at Hydropower Draft Tubes: Some Design Examples Using Electric Guidance Technology to Prevent Fish Entry and Reduce Removal Labor

The global hydropower community faces constant challenges to prevent fish from entering tailraces and draft tubes.  When water emerges from turbines and exits through tailrace draft tubes before rejoining rivers, anadromous and resident fishes are attracted.  They often enter turbine chambers in large numbers before preventative, stop-log deployments during turbine shutdown.  Upon restart, significant mortalities occur.  The ability to prevent fish entry is thus a necessity for conservation.  Different deterrence technologies have been attempted with varying success.  Electric barrier technology is under-utilized and somewhat undiscovered in the hydropower management community.  Although used extensively and successfully in resource management applications to block invasive species, fewer examples exist of electric guidance technology use at hydropower facilities.  Fish entrapment in draft tubes and turbine chambers is documented, but often unreported.  Our presentation notes some reported instances and suggests solutions via electric deterrence fields within or at the downstream ends of draft tubes.  We describe retrofit schematics under consideration for application in Brazil and ways in which these designs can be incorporated into new hydropower construction.  We conclude with specific examples of how this electric deterrence technology can exclude fish from hydropower draft tubes, promote conservation, and reduce laborious fish removal efforts.