Weir - Revision history

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energy>Jmdonev at 21:36, 17 February 2020

2020-02-17T21:36:22Z

← Older revision		Revision as of 21:36, 17 February 2020
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	[[Category:Done ~~2017~~-07-01]]		[[Category:Done 2020-02-29]]
	[[File:076949_9bd456c6.jpg\|360px\|thumb\|right\|Figure 1. The Radyr Weir in Great Britain.<ref>Geograph. (December 29, 2015). ''Radyr Weir and Taff valley railway line'' [Online]. Available: http://www.geograph.org.uk/photo/76949</ref>]]		[[File:076949_9bd456c6.jpg\|360px\|thumb\|right\|Figure 1. The Radyr Weir in Great Britain.<ref>Geograph. (December 29, 2015). ''Radyr Weir and Taff valley railway line'' [Online]. Available: http://www.geograph.org.uk/photo/76949</ref>]]
	<onlyinclude>A '''weir''' is a small barrier ~~that is~~ built across a stream or river to raise the [[water]] level slightly on the upstream side~~, and is~~ essentially a small-scale dam. Weirs allow ~~for~~ water to pool behind them, while ~~still~~ allowing water to flow steadily over top of the weir ~~itself~~.</onlyinclude><ref name="RE1">~~Green Bug Energy~~. ~~(December 29~~, ~~2015). ''~~What is ~~the difference between a dam~~, ~~a weir~~, ~~and a barrage?''~~ [Online]. Available: ~~http~~://~~greenbugenergy~~.com/~~sp_faq/what~~-~~is-the-difference-between-a~~-dam-a-~~weir-and-a-barrage~~</ref> Additionally, the term '''weir''' can be used to refer to the crest of a [[spillway]] on a large [[hydroelectric dam\|embankment dam]].		<onlyinclude>A '''weir''' is a small barrier built across a stream or river to raise the [[water]] level slightly on the upstream side; essentially a small-scale dam. Weirs allow water to pool behind them, while allowing water to flow steadily over top of the weir.</onlyinclude><ref name="RE1">[4]W. Fowler, "What is A Weir \| Weir Structure \| Weir Design \| SANI-TRED", Sanitred.com, 2015. [Online]. Available: https://sanitred.com/waterproofing-weir-dam/. [Accessed: 09- Feb- 2020].</ref> Additionally, the term '''weir''' can be used to refer to the crest of a [[spillway]] on a large [[hydroelectric dam\|embankment dam]].

	Weirs can be constructed out of several different materials, depending on their age and purpose. Wood, concrete, or a mixture of rocks, gravel, and boulders can all be used to construct a weir.<ref ~~name="RE1"~~/>		Weirs can be constructed out of several different materials, depending on their age and purpose. Wood, concrete,<ref>"Weir Plate Materials", Openchannelflow.com, 2020. [Online]. Available: https://www.openchannelflow.com/blog/weir-plate-materials. [Accessed: 09- Feb- 2020].</ref> or a mixture of rocks, gravel, and boulders can all be used to construct a weir.<ref>Rock Weir Design Guidance - Reclamation: Managing Water in the West. Denver, Colorado: U.S. Department of Interior, Bureau of Reclamation, 2016, pp. 13-14.</ref>

	In a weir, the surface over which the water flows is known as the '''[[crest]]'''. The flow of water that moves overtop of this crest is known as the '''nappe''', which is simply the water that makes it overtop the weir. This nappe does not exist with dams, as dams permit no flow of water over the structure. If this nappe falls a significant distance through the air - meaning that the weir increases the elevation of the water prior to the weir - the weir is said to have free discharge. However, if water flows partially underwater as a result of little elevation increase from the weir it is said to be submerged or drowned.<ref name="RE2">Civil Engineering Portal. (December 29, 2015). ''Weirs'' [Online]. Available: http://www.engineeringcivil.com/weirs.html</ref>		In a weir, the surface over which the water flows is known as the '''[[crest]]'''. The flow of water that moves overtop of this crest is known as the '''nappe''', which is simply the water that makes it overtop the weir. This nappe does not exist with dams, as dams permit no flow of water over the structure. If this nappe falls a significant distance through the air - meaning that the weir increases the elevation of the water prior to the weir - the weir is said to have free discharge. However, if water flows partially underwater as a result of little elevation increase from the weir it is said to be submerged or drowned.<ref name="RE2">Civil Engineering Portal. (December 29, 2015). ''Weirs'' [Online]. Available: http://www.engineeringcivil.com/weirs.html</ref>
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	Weirs do have drawbacks, as they can increase [[sediment]]ation and pose potential migration barriers to fish. To aid in migration, [[fish passage\|fish ladder]]s are sometimes incorporated into weirs to aid in fish passage. Sedimentation can occur as the water slows as it goes over the weir, dropping [[sediment]] as it slows.<ref>Minnesota Rural Water Association. (December 29, 2015). ''Sedimentation and Weirs'' [Online]. Available: http://www.mrwa.com/WaterWorksMnl/Chapter%2013%20Sedmentation.pdf</ref> As well, as water passes over the top of the weir, the motion can alter the dissolved [[oxygen]] levels. If the water is over or under-oxygenated (called [[hypoxia]] or [[anoxia]]), this can harm the local [[ecosystem]].		Weirs do have drawbacks, as they can increase [[sediment]]ation and pose potential migration barriers to fish. To aid in migration, [[fish passage\|fish ladder]]s are sometimes incorporated into weirs to aid in fish passage. Sedimentation can occur as the water slows as it goes over the weir, dropping [[sediment]] as it slows.<ref>Minnesota Rural Water Association. (December 29, 2015). ''Sedimentation and Weirs'' [Online]. Available: http://www.mrwa.com/WaterWorksMnl/Chapter%2013%20Sedmentation.pdf</ref> As well, as water passes over the top of the weir, the motion can alter the dissolved [[oxygen]] levels. If the water is over or under-oxygenated (called [[hypoxia]] or [[anoxia]]), this can harm the local [[ecosystem]].

	Weirs are particularly dangerous to humans - and are thus commonly called "drowning machines". Particularly, the circulating "backwash" of water behind the weir is easy to get trapped within, and if a swimmer or boater is caught within this cycle escape and rescue is incredibly difficult. Additionally, debris that can be trapped within this cycle of water can pose harm to anyone trapped behind the weir.<ref>Pennsylvania Fish and Boat Commission. (December 29, 2015). ''Low Head Dams'' [Online]. Available: http://fishandboat.com/damlow_info.htm</ref>		Weirs are particularly dangerous to humans - and are thus commonly called "drowning machines".<ref>"Weir safety: fact sheet", Seqwater.com.au, 2020. [Online]. Available: https://www.seqwater.com.au/sites/default/files/2019-09/Seqwater%20fact%20sheet%20-%20What%20is%20a%20weir.pdf. [Accessed: 09- Feb- 2020].</ref> Particularly, the circulating "backwash" of water behind the weir is easy to get trapped within, and if a swimmer or boater is caught within this cycle escape and rescue is incredibly difficult. Additionally, debris that can be trapped within this cycle of water can pose harm to anyone trapped behind the weir.<ref>Pennsylvania Fish and Boat Commission. (December 29, 2015). ''Low Head Dams'' [Online]. Available: http://fishandboat.com/damlow_info.htm</ref>

			In the video below Grady Hillhouse<ref>His web page is here: https://practical.engineering/about accessed February 17th, 2020.</ref> discusses how weirs work. He's built a small scale model of a weir (skip ahead to 5:24 to see the scale model), as well as other versions of weirs that exist.

			<html>
			<iframe width="816" height="459" src="//www.youtube.com/embed/YkR79oDAgOg;" frameborder="0" allowfullscreen></iframe>
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			== For Further Reading ==
			For further information please see the related pages below:
			*[[Hydroelectric facility]]
			*[[Hydropower]]
			*[[Hydrologic cycle]]
			*[[Hydroelectric dam]]
			*[[Environmental impacts of hydropower]]
			* Or explore a [[Special:Random\| random page]]

	==References==		==References==
	{{reflist}}		{{reflist}}
	[[Category:Uploaded]]		[[Category:Uploaded]]

Jmdonev: 1 revision imported

2017-08-29T01:46:53Z

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Jmdonev at 17:36, 28 July 2017

2017-07-28T17:36:55Z

← Older revision		Revision as of 17:36, 28 July 2017
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	[[Category:Done ~~2016~~-01~~-15~~]]		[[Category:Done 2017-07-01]]
	[[File:076949_9bd456c6.jpg\|360px\|thumb\|right\|Figure 1. The Radyr Weir in Great Britain.<ref>Geograph. (December 29, 2015). ''Radyr Weir and Taff valley railway line'' [Online]. Available: http://www.geograph.org.uk/photo/76949</ref>]]		[[File:076949_9bd456c6.jpg\|360px\|thumb\|right\|Figure 1. The Radyr Weir in Great Britain.<ref>Geograph. (December 29, 2015). ''Radyr Weir and Taff valley railway line'' [Online]. Available: http://www.geograph.org.uk/photo/76949</ref>]]
	<onlyinclude>A '''weir''' is a small barrier that is built across a stream or river to raise the [[water]] level slightly on the upstream side, and is essentially a small-scale dam. Weirs allow for water to pool behind them, while still allowing water to flow steadily over top of the weir itself.</onlyinclude><ref name="RE1">Green Bug Energy. (December 29, 2015). ''What is the difference between a dam, a weir, and a barrage?'' [Online]. Available: http://greenbugenergy.com/sp_faq/what-is-the-difference-between-a-dam-a-weir-and-a-barrage</ref> Additionally, the term '''weir''' can be used to refer to the crest of a [[spillway]] on a large [[hydroelectric dam\|embankment dam]].		<onlyinclude>A '''weir''' is a small barrier that is built across a stream or river to raise the [[water]] level slightly on the upstream side, and is essentially a small-scale dam. Weirs allow for water to pool behind them, while still allowing water to flow steadily over top of the weir itself.</onlyinclude><ref name="RE1">Green Bug Energy. (December 29, 2015). ''What is the difference between a dam, a weir, and a barrage?'' [Online]. Available: http://greenbugenergy.com/sp_faq/what-is-the-difference-between-a-dam-a-weir-and-a-barrage</ref> Additionally, the term '''weir''' can be used to refer to the crest of a [[spillway]] on a large [[hydroelectric dam\|embankment dam]].
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	Weirs can be built to measure water [[flow rate]], to alter the flow of rivers, or to prevent flooding. Additionally, small-size weirs can be used in large [[hydropower]] developments as a way to mitigate potential harm that may come about as a result of dam development. Small weirs can help improve fish numbers, stabilize water levels, and stabilize effects of river alteration.<ref name="RE1"/>		Weirs can be built to measure water [[flow rate]], to alter the flow of rivers, or to prevent flooding. Additionally, small-size weirs can be used in large [[hydropower]] developments as a way to mitigate potential harm that may come about as a result of dam development. Small weirs can help improve fish numbers, stabilize water levels, and stabilize effects of river alteration.<ref name="RE1"/>

	Weirs do have drawbacks, as they can increase [[~~sedimentation~~]] and pose potential migration barriers to fish. To aid in migration, [[fish passage\|fish ladder]]s are sometimes incorporated into weirs to aid in fish passage. Sedimentation can occur as the water slows as it goes over the weir, dropping [[sediment]] as it slows.<ref>Minnesota Rural Water Association. (December 29, 2015). ''Sedimentation and Weirs'' [Online]. Available: http://www.mrwa.com/WaterWorksMnl/Chapter%2013%20Sedmentation.pdf</ref> As well, as water passes over the top of the weir, the motion can alter the dissolved [[oxygen]] levels. If the water is over or under-oxygenated (called [[hypoxia]] or [[anoxia]]), this can harm the local [[~~ecology~~]].		Weirs do have drawbacks, as they can increase [[sediment]]ation and pose potential migration barriers to fish. To aid in migration, [[fish passage\|fish ladder]]s are sometimes incorporated into weirs to aid in fish passage. Sedimentation can occur as the water slows as it goes over the weir, dropping [[sediment]] as it slows.<ref>Minnesota Rural Water Association. (December 29, 2015). ''Sedimentation and Weirs'' [Online]. Available: http://www.mrwa.com/WaterWorksMnl/Chapter%2013%20Sedmentation.pdf</ref> As well, as water passes over the top of the weir, the motion can alter the dissolved [[oxygen]] levels. If the water is over or under-oxygenated (called [[hypoxia]] or [[anoxia]]), this can harm the local [[ecosystem]].

	Weirs are particularly dangerous to humans - and are thus commonly called "drowning machines". Particularly, the circulating "backwash" of water behind the weir is easy to get trapped within, and if a swimmer or boater is caught within this cycle escape and rescue is incredibly difficult. Additionally, debris that can be trapped within this cycle of water can pose harm to anyone trapped behind the weir.<ref>Pennsylvania Fish and Boat Commission. (December 29, 2015). ''Low Head Dams'' [Online]. Available: http://fishandboat.com/damlow_info.htm</ref>		Weirs are particularly dangerous to humans - and are thus commonly called "drowning machines". Particularly, the circulating "backwash" of water behind the weir is easy to get trapped within, and if a swimmer or boater is caught within this cycle escape and rescue is incredibly difficult. Additionally, debris that can be trapped within this cycle of water can pose harm to anyone trapped behind the weir.<ref>Pennsylvania Fish and Boat Commission. (December 29, 2015). ''Low Head Dams'' [Online]. Available: http://fishandboat.com/damlow_info.htm</ref>
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	==References==		==References==
	{{reflist}}		{{reflist}}
			[[Category:Uploaded]]

Jmdonev: 1 revision imported

2016-02-18T04:31:18Z

1 revision imported

← Older revision	Revision as of 04:31, 18 February 2016
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Jmdonev at 02:22, 10 January 2016

2016-01-10T02:22:35Z

New page

[[Category:Done 2016-01-15]]
[[File:076949_9bd456c6.jpg|360px|thumb|right|Figure 1. The Radyr Weir in Great Britain.<ref>Geograph. (December 29, 2015). ''Radyr Weir and Taff valley railway line'' [Online]. Available: http://www.geograph.org.uk/photo/76949</ref>]]
<onlyinclude>A '''weir''' is a small barrier that is built across a stream or river to raise the [[water]] level slightly on the upstream side, and is essentially a small-scale dam. Weirs allow for water to pool behind them, while still allowing water to flow steadily over top of the weir itself.</onlyinclude><ref name="RE1">Green Bug Energy. (December 29, 2015). ''What is the difference between a dam, a weir, and a barrage?'' [Online]. Available: http://greenbugenergy.com/sp_faq/what-is-the-difference-between-a-dam-a-weir-and-a-barrage</ref> Additionally, the term '''weir''' can be used to refer to the crest of a [[spillway]] on a large [[hydroelectric dam|embankment dam]].

Weirs can be constructed out of several different materials, depending on their age and purpose. Wood, concrete, or a mixture of rocks, gravel, and boulders can all be used to construct a weir.<ref name="RE1"/>

In a weir, the surface over which the water flows is known as the '''[[crest]]'''. The flow of water that moves overtop of this crest is known as the '''nappe''', which is simply the water that makes it overtop the weir. This nappe does not exist with dams, as dams permit no flow of water over the structure. If this nappe falls a significant distance through the air - meaning that the weir increases the elevation of the water prior to the weir - the weir is said to have free discharge. However, if water flows partially underwater as a result of little elevation increase from the weir it is said to be submerged or drowned.<ref name="RE2">Civil Engineering Portal. (December 29, 2015). ''Weirs'' [Online]. Available: http://www.engineeringcivil.com/weirs.html</ref>

[[File:weirfix.jpg|780px|thumb|center|Figure 2. Diagram of two weirs, depicting both free discharge and drowned versions.<ref>''Created internally by a member of the Energy Education team''</ref>]]

==Weir vs. Dam==
Weirs differ from dams in one major way. First and foremost, in a weir the water from upstream runs over top of the weir itself, constantly overflowing.<ref name="RE1"/> In a dam, water flows through [[spillway]]s and [[penstock]]s instead of over top of the dam, which could actually cause damage and is known as overtopping.

==Benefits and Drawbacks==
Weirs can be built to measure water [[flow rate]], to alter the flow of rivers, or to prevent flooding. Additionally, small-size weirs can be used in large [[hydropower]] developments as a way to mitigate potential harm that may come about as a result of dam development. Small weirs can help improve fish numbers, stabilize water levels, and stabilize effects of river alteration.<ref name="RE1"/>

Weirs do have drawbacks, as they can increase [[sedimentation]] and pose potential migration barriers to fish. To aid in migration, [[fish passage|fish ladder]]s are sometimes incorporated into weirs to aid in fish passage. Sedimentation can occur as the water slows as it goes over the weir, dropping [[sediment]] as it slows.<ref>Minnesota Rural Water Association. (December 29, 2015). ''Sedimentation and Weirs'' [Online]. Available: http://www.mrwa.com/WaterWorksMnl/Chapter%2013%20Sedmentation.pdf</ref> As well, as water passes over the top of the weir, the motion can alter the dissolved [[oxygen]] levels. If the water is over or under-oxygenated (called [[hypoxia]] or [[anoxia]]), this can harm the local [[ecology]].

Weirs are particularly dangerous to humans - and are thus commonly called "drowning machines". Particularly, the circulating "backwash" of water behind the weir is easy to get trapped within, and if a swimmer or boater is caught within this cycle escape and rescue is incredibly difficult. Additionally, debris that can be trapped within this cycle of water can pose harm to anyone trapped behind the weir.<ref>Pennsylvania Fish and Boat Commission. (December 29, 2015). ''Low Head Dams'' [Online]. Available: http://fishandboat.com/damlow_info.htm</ref>

==References==
{{reflist}}