- Fish screen
A fish screen is a barrier designed to prevent
fish from swimming or being drawn into anaqueduct , cooling water intake,dam , or other diversion on ariver ,lake , or other waterway where water is taken for human use. Fish screens are typically installed to protectendangered species of fishes that would otherwise be harmed when passing through industrial facilities such as hydroelectric generators, petroleum refineries,chemical plant s and municipal drinking water treatment plants.Design
Fish screens may be positive barriers (devices such as a perforated metal plate that physically prevents fishes from passing) or behavioral barriers (devices that encourage fishes to swim away). Most behavioral barriers are experimental and of unproven effectiveness. Positive barriers are effective and widely used. Besides simply preventing fishes from passing, fish screens are designed to minimized stress and injury that occur when fishes impact the screen or are subjected to changes in water velocity and direction caused by the diversion.
Most fish screens are designed to protect a single species of fish (for example,
salmon ) and are not necessarily effective at protecting other fish species.The cost of a fish screen varies from thousands of US dollars for small, low-flow-rate screens to millions of US dollars in the case of very large custom-designed systems that filter a large flow of water. Maintenance costs can be significant, including repairs, removing trash, and adjusting the equipment for changes in stream conditions.
Legal requirements
In the
United States , theNational Marine Fisheries Service , a division ofNOAA , 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.The U.S.
Clean Water Act requires theEnvironmental Protection Agency (EPA) to issueregulation s on industrial cooling water intake structures. [Clean Water Act, Section 316(b), USC|33|1316.] EPA has published several regulations, which are underlitigation as of 2008. [U.S. EPA, Washington, DC. [http://epa.gov/waterscience/316b/ "Cooling Water Intake Structures."] Accessed 2008-08-23.] [Citation
last=Greenhouse
first=Linda
author-link=
title=Court Sets Fall Debate on Standards of Water Act
newspaper=New York Times
volume=
issue=
pages=
year=2008
date=April 15, 2008
url=http://www.nytimes.com/2008/04/15/washington/15scotus.html?scp=1&sq=riverkeeper%20epa%20cooling&st=cse]Geographic spread
Fish screens are common at large water diversions in
California , where they protect endangered and threatened runs ofsalmon and other fishes.ee also
*
Fish ladder References
External links
* [http://epa.gov/waterscience/316b/phase2/devdoc/final/ch4attacha.pdf Cooling Water Intake Structure Technology Fact Sheets] - U.S. EPA
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