water stagnation

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File:Mosquito larvae.jpge in stagnant water]]

Water stagnation or still water occurs when water stops flowing for a long period of time. Stagnant water can be a significant environmental hazard.{{cite web |author= |date=2010 |title=General Article: Yellow Fever and Malaria in the Canal |url=https://www.pbs.org/wgbh/americanexperience/features/general-article/panama-fever/ |archive-url=https://web.archive.org/web/20161129070452/https://www.pbs.org/wgbh/americanexperience/features/general-article/panama-fever/ |archive-date=Nov 29, 2016 |website=Panama Canal (film) |series=American Experience |publisher=WGBH Educational Foundation |location=Boston, MA}}

Dangers

File:Chad 2019 man drinking dirty water from Batha river reservoir in Oum-Hadjer DSC4381-2.jpg]]

Malaria and dengue are among the main dangers of still water, which can become a breeding ground for the mosquitoes that transmit these diseases.{{cite report |date=2013 |title=Health Risks Associated with Stagnant Water |series=Recommendations for Occupational Health and Safety Following Disasters |url=http://www.wpro.who.int/philippines/typhoon_haiyan/media/health_risks_associated_with_stagnant_water.pdf |archive-url=https://web.archive.org/web/20141127003256/http://www.wpro.who.int/philippines/typhoon_haiyan/media/health_risks_associated_with_stagnant_water.pdf |url-status=dead |archive-date=November 27, 2014 |publisher=World Health Organization}}

Stagnant water can be dangerous because it provides a better incubator than running water for many kinds of infectious pathogens. Stagnant water can be contaminated with human and animal feces, particularly in deserts or other areas of low rainfall. Water stagnation for as little as six days can completely change bacterial community composition and increase cell count.{{Cite journal |last1=Ling |first1=Fangqiong |last2=Whitaker |first2=Rachel |author-link2=Rachel J Whitaker |last3=LeChevallier |first3=Mark W. |last4=Liu |first4=Wen-Tso |date=1 June 2018 |title=Drinking water microbiome assembly induced by water stagnation |journal=The ISME Journal |language=en |volume=12 |issue=6 |pages=1520–1531 |doi=10.1038/s41396-018-0101-5 |issn=1751-7362 |pmc=5955952 |pmid=29588495 |doi-access=free|bibcode=2018ISMEJ..12.1520L }}

Stagnant water may be classified into the following basic, although overlapping, types:

Water body stagnation (stagnation in swamp, lake, lagoon, river, etc.)
Surface and ground water stagnation
Trapped water stagnation. The water may be trapped in human artifacts (discarded cans, plant pots, tires, dug-outs, roofs, etc.), as well as in natural containers, such as hollow tree trunks, leaf sheaths, etc.

To avoid ground and surface water stagnation, the drainage of surface and subsoil is advised. Areas with a shallow water table are more susceptible to ground water stagnation due to the lower availability of natural soil drainage.

Life that may thrive in stagnant water

Some plants prefer flowing water, while others, such as lotuses, prefer stagnant water.

Various anaerobic bacteria are commonly found in stagnant water.{{cite journal|last1=Cabral|first1=João|title=Water Microbiology. Bacterial Pathogens and Water|journal=International Journal of Environmental Research and Public Health|date=October 10, 2010|pmc=2996186|pmid=21139855|doi=10.3390/ijerph7103657|volume=7|issue=10|pages=3657–703|doi-access=free}} For this reason, pools of stagnant water have historically been used in processing hemp and some other fiber crops, as well as linden bark used for making bast shoes. Several weeks of soaking makes bast fibers easily separable due to bacterial and fermentative processes known as retting.