Fish screen

4–19 Positive barriers are often effective at keeping aquatic organisms from entering a cooling system, but may also kill them by impinging them on the screens.

For some low volume, non-industrial water diversion applications, there are screens available that have no moving parts, do not require electricity, and have very little need for maintenance.

For example, the cooling system at the Indian Point Energy Center in New York was claimed to kill over a billion fish eggs and larvae annually.

[8] In the United States, the National Marine Fisheries Service, a division of NOAA, mandates positive-barrier fishscreens in most new diversions from waterways where endangered or threatened fish species occur.

Some existing unscreened diversions whose construction pre-dates fish-screen mandates are allowed to continue operating by grandfather rule.

Fish screen at Redlands Canal, near Grand Junction, Colorado
Diagram of typical vertical traveling screens used with industrial cooling water intake structures
The Indian Point Energy Center in New York. Over a billion fish eggs and larvae were claimed to be killed in its cooling system each year while it was still operating.