Offshore Water Intakes Designed to Protect Fish

The engineering design and biological effectiveness of five design concepts for fish protection at offshore intakes are examined. Velocity cap intakes entrap large quantities of fish at some locations and are not effective in preventing the entrainment of fish larvae. Hydrodynamic model studies and tests indicated poor fish diversion and the need for further development. Wedge-wire screen intakes are effective and practical for makeup intakes; however, since proven methods for preventing icing and clogging problems have not been developed, further developmental work is needed for application to once-through cooling intakes. Behavioral barriers, such as an air bubble curtain, a water jet curtain, and hanging chains, have only limited effectiveness in reducing fish entrapment. For makeup water intakes, infiltration systems, such as the radial well intake, are effective, given that a suitable aquifer exists.