dam /weir / barrage

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New Member
Here is the context:
"structures, such as dams, weirs or barrages may seriously interfere with migration in a water body"

Could someone explain what is the difference between a dam, a weir and a barrage. The only transation I found (in french) for all three is: < the same word >

Thank you.
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  • valou59

    New Member
    Thank you for your answer.
    By looking at the photos, I realise that some weirs can be
    - sometimes translated in french by a "<French word deleted>": a structure within dike (meaning not acrros but along the river) that is intended to break down to allow the flooding of an area (then preventing the flooding of other dowstream more vulnerable areas)
    - but they are not only that... apparently some weirs are delimit ponds within water bodies ? For fish culture ?

    Here are some additional definitions I found:
    What is a weir?
    A low dam that is built across a river to raise the water level, divert the water, or control its flow.
    What is a lock?
    A section of a canal or river that may be closed off by gates to control the water level and the raising and lowering of vessels that pass through it.
    What is a barrage?
    A barrage is a construction across a watercourse to increase the depth of water to assist navigation or irrigation.
    What is a dam?
    A barrier of concrete or earth built across a river to create a body of water as for domestic water supply, or a reservoir of water created by such a barrier.

    Definitions sourced from: The Australian concise Oxford dictionary of current English / edited by Bruce Moore, Melbourne, Vic.: Oxford University Press, c1997 3rd ed
    and wordref
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    New Member
    some more:
    "Dam" is the general word for blocking the flow of a river. A dam usually creates a lake and the larger projects have built-in turbines generating elecricity, may also have sluice gates to control the level of the lake, upto 335 meters deep.
    Example: ww.usbr.gov/mp/ncao/images/shasta_dam_fullsize.jpg

    A "barrage" or "weir" is a smaller type of dam creating a pond behind it not more than a few meters deep. Barrages may serve to control tides also. Excess water in the pond usually flows over the top of a spill-line. Example:htp://civil.iisc.ernet.in/~wree/photos/Bheem_Gowda_Barrage1.jpg


    Senior Member
    British English
    Dams and barrages contain the flow of water. Weirs do not: water flows over a weir. I suggest you look for some images of weirs.
    Not entirely true though. Weirs do restrict water flow. The difference is that when the water reaches a certain height it is allowed to spill over the top of the weir, whereas a dam does not allow overspill, rather the water must pass through special structures such as spillways in order to escape. Weirs are used primarily to regulate flow in rivers. Dams are used to retain water for human consumption or for electricity generation.
    John Scott (Dictionary of Civil Engineering) defines a barrage as a low dam ... placed across a river to raise its level ...
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