{{Short description|River section with little or no current}} A '''backwater''' is a part of a river in which there is little or no current. It can refer to a branch of a main river, which lies alongside it and then rejoins it, or to a body of water in a main river, backed up by the sea tide or by an obstruction such as a dam.<ref>[https://www.merriam-webster.com/dictionary/backwater Merriam Webster Dictionary]</ref> Manmade restrictions to natural stream flow or temporary natural obstructions such as ice jams, vegetation blockage, or flooding of a lower stream can create backwater.<ref>{{cite web |url=https://pubs.usgs.gov/wsp/1541a/report.pdf#page=8 |title=General Introduction and Hydrologic Definitions, Manual of Hydrology: Part 1. General Surface-Water Techniques |last1=Langbein |first=W. B. |last2=Iseri|first2=Kathleen T. |date=1960 |website=pubs.usgs.gov |series=Geological Survey Water Supply Paper 1542-F |publisher=U.S. Geological Survey |access-date=February 10, 2019}}</ref>
== Alternative channel == [[File:Alappuzha Boat Beauty W.jpg|thumb|A Kerala houseboat in Kumarakom, India]] If a river has developed one or more alternative courses in its evolution, one channel is usually designated the main course, and secondary channels may be termed backwaters.<ref>[http://www.wargrave.net/history/nov03.html Wargrave Local History Society Latest News - November 2003 Hennerton and the Backwater] {{webarchive|url=https://web.archive.org/web/20110724125729/http://www.wargrave.net/history/nov03.html |date=2011-07-24 }}</ref> The main river course will usually have the fastest stream and will likely be the main navigation route; backwaters may be shallower and flow more slowly, if at all. Some backwaters are rich in mangrove forest.<ref>{{Cite news|url=https://travel.manoramaonline.com/travel/getting-about-kerala/thrissur/2018/07/31/chettuva-in-thrissur-flaunting-kerala-mangrove-forest.html|title=Chettuva in Thrissur: Flaunting Kerala's biggest mangrove forest|work=OnManorama|access-date=2018-08-28}}</ref> This results in a more diverse environment of scientific interest and worthy of preservation.<ref>{{Cite web |url=http://www.ivb.cz/fish/pdf/pj57%20restoration.pdf |title=E. HOHAUSOVÁ, P. JURAJDA ''Restoration of a river backwater and its influence on fish assemblage'' Czech J. Anim. Sci., 50, 2005 (10): 473–482 |access-date=2010-07-29 |archive-url=https://web.archive.org/web/20170705121847/http://www.ivb.cz/fish/pdf/pj57%20restoration.pdf |archive-date=2017-07-05 |url-status=dead }}</ref><ref>{{Cite web |url=http://www.istc.illinois.edu/special_projects/il_river/backwtr_restoration_marlin.pdf |title=John C. Marlin ''BACKWATER RESTORATION OPPORTUNITIES: ILLINOIS RIVER'' Waste Management and Research Center, Illinois Department of Natural Resources One |access-date=2010-07-29 |archive-url=https://web.archive.org/web/20160303211352/http://www.istc.illinois.edu/special_projects/il_river/backwtr_restoration_marlin.pdf |archive-date=2016-03-03 |url-status=dead }}</ref> Backwaters also provide opportunities for leisure activities such as canoeing and fishing.<ref>{{Cite web |url=http://www.visitthames.co.uk/text/1611/free_family_fun.html |title=Vistt Thames Free Family Fun |access-date=2010-07-29 |archive-date=2012-01-25 |archive-url=https://web.archive.org/web/20120125230932/http://visitthames.co.uk/text/1611/free_family_fun.html |url-status=dead }}</ref><ref>{{Cite web |url=http://www.canoefocus.demon.co.uk/accesscliveden.html |title=Suggested paddles Cliveden Reach on the Thames |access-date=2010-07-29 |archive-url=https://web.archive.org/web/20100723192158/http://www.canoefocus.demon.co.uk/accesscliveden.html |archive-date=2010-07-23 |url-status=dead }}</ref> The term has been applied as a metaphor to physical and social areas that have been bypassed. It may apply to places that have been neglected in economic development,<ref>[https://books.google.com/books?id=7YUDP-H3R4AC&q=backwater The Cambridge Economic History of Modern Britain]</ref> or in the expression a "cultural backwater".<ref>{{Cite news|url=https://www.wsj.com/articles/SB102098548645519960|title=A Cultural Backwater No Longer|last=Yee|first=Amy|date=2002-05-10|work=Wall Street Journal|access-date=2018-10-07|language=en-US|issn=0099-9660}}</ref>
==Water backed up by an obstruction== [[Image:KumarakomHouseBoat.jpg|thumbnail|right|Kumarakom lake in Kerala backwaters]] When a section of a river is near the coast or another feature that sets its base level, the section influenced by the conditions at its mouth is termed a backwater. If a river flows into a lake or sea, it is the region in which the slope of the river decreases because the lower water flux permitted at the mouth causes the water to back up. Where the river outlet is strongly affected by tides, the cyclic change in base level changes the portion of the river that is a backwater. As a result, fresh and salt water may become mixed to form an estuarine environment.<ref>{{cite web|url=http://ocw.mit.edu/courses/earth-atmospheric-and-planetary-sciences/12-090-special-topics-an-introduction-to-fluid-motions-sediment-transport-and-current-generated-sedimentary-structures-fall-2006/lecture-notes/ch5.pdf|title=Chapter 5: Open-Channel Flow|last=Southard|first=John B.|year=2006|work=An Introduction to Fluid Motions, Sediment Transport, and Current-generated Sedimentary Structures|publisher=MIT OpenCourseWare|access-date=16 March 2010}}</ref>
==See also== *Distributary *Lagoon *Kerala backwaters
==References== {{Reflist}}
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Category:Rivers