Editing Water (section)

==Effects on human civilization==
{{More citations needed section|date=May 2018}}
[[File:Longwood Gardens-Italian Garden.jpg|thumb|right|Water [[fountain]]]]

Civilization has historically flourished around rivers and major waterways; [[Mesopotamia]], one of the so-called [[cradles of civilization]], was situated between the major rivers [[Tigris]] and [[Euphrates]]; the ancient society of the [[Egyptians]] depended entirely upon the [[Nile]]. The early [[Indus Valley civilization]] ({{Circa|3300 BCE|1300 BCE}}) developed along the Indus River and tributaries that flowed out of the [[Himalayas]]. [[Rome]] was also founded on the banks of the Italian river [[Tiber]]. Large [[metropolis]]es like [[Rotterdam]], [[London]], [[Montreal]], [[Paris]], [[New York City]], [[Buenos Aires]], [[Shanghai]], [[Tokyo]], [[Chicago]], and [[Hong Kong]] owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like [[Singapore]], have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development.

===Health and pollution===
[[File: Field Trip- water sampling.jpg|thumb|An environmental science program – a student from [[Iowa State University]] sampling water]]
Water fit for human consumption is called [[drinking water]] or potable water. Water that is not potable may be made potable by filtration or [[distillation]], or by a range of [[Water treatment|other methods]]. More than 660 million people do not have access to safe drinking water.<ref>{{Cite web|title=On Water|url=https://www.eib.org/en/essays/on-water|access-date=13 October 2020|website=European Investment Bank|language=en|archive-date=14 October 2020|archive-url=https://web.archive.org/web/20201014022119/https://www.eib.org/en/essays/on-water|url-status=live}}</ref><ref>{{Cite web|title=2.4 billion Without Adequate Sanitation. 600 million Without Safe Water. Can We Fix it by 2030?|url=https://ieg.worldbankgroup.org/blog/over-24-billion-without-adequate-sanitation-600-million-without-safe-water-how-do-we-bridge|access-date=13 October 2020|publisher=World Bank Group|first=Ramachandra |last=Jammi|date=13 March 2018 |language=en|archive-date=14 October 2020|archive-url=https://web.archive.org/web/20201014022128/https://ieg.worldbankgroup.org/blog/over-24-billion-without-adequate-sanitation-600-million-without-safe-water-how-do-we-bridge|url-status=live}}</ref>

Water that is not fit for drinking but is not harmful to humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called [[safe water]], or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1–2 ppm of chlorine not yet reacted with impurities for bathing water). Water for bathing may be maintained in satisfactory microbiological condition using chemical disinfectants such as [[chlorine]] or [[ozone]] or by the use of [[ultraviolet]] light.

[[Reclaimed water|Water reclamation]] is the process of converting wastewater (most commonly [[sewage]], also called municipal wastewater) into water that can be [[reuse]]d for other purposes. There are 2.3 billion people who reside in nations with water scarcities, which means that each individual receives less than {{convert|1,700|m3}} of water annually. {{convert|380|e9m3}} of municipal wastewater are produced globally each year.<ref name="EIB-2022">{{Cite web |title=Wastewater resource recovery can fix water insecurity and cut carbon emissions |url=https://www.eib.org/en/essays/wastewater-resource-recovery |access-date=29 August 2022 |website=European Investment Bank |language=en |archive-date=29 August 2022 |archive-url=https://web.archive.org/web/20220829150040/https://www.eib.org/en/essays/wastewater-resource-recovery |url-status=live }}</ref><ref>{{Cite web |title=International Decade for Action 'Water for Life' 2005–2015. Focus Areas: Water scarcity |url=https://www.un.org/waterforlifedecade/scarcity.shtml |access-date=29 August 2022 |publisher=United Nations |archive-date=23 May 2020 |archive-url=https://web.archive.org/web/20200523125706/https://www.un.org/waterforlifedecade/scarcity.shtml |url-status=live }}</ref><ref>{{Cite web |title=The State of the World's Land and Water Resources for Food and Agriculture |url=https://www.fao.org/3/i1688e/i1688e.pdf |access-date=30 August 2022 |archive-date=31 August 2022 |archive-url=https://web.archive.org/web/20220831234648/http://www.fao.org/3/i1688e/i1688e.pdf |url-status=live }}</ref>

Freshwater is a renewable resource, recirculated by the natural [[hydrologic cycle]], but pressures over access to it result from the naturally uneven distribution in space and time, growing economic demands by agriculture and industry, and rising populations. Currently, nearly a billion people around the world lack access to safe, affordable water. In 2000, the [[United Nations]] established the [[Millennium Development Goals]] for water to halve by 2015 the proportion of people worldwide without access to safe water and [[sanitation]]. Progress toward that goal was uneven, and in 2015 the UN committed to the [[Sustainable Development Goals]] of achieving universal access to safe and affordable water and sanitation by 2030. Poor [[water quality]] and bad sanitation are deadly; some five million deaths a year are caused by water-related diseases. The [[World Health Organization]] estimates that [[safe water]] could prevent 1.4 million child deaths from [[diarrhea]] each year.<ref>{{cite web |url=https://www.who.int/features/QA/70/en/ |title=World Health Organization. Safe Water and Global Health |publisher=World Health Organization |date=25 June 2008 |access-date=25 July 2010 |archive-url=https://web.archive.org/web/20101224174349/http://www.who.int/features/qa/70/en/ |archive-date=24 December 2010 |url-status=live }}</ref>

In developing countries, 90% of all [[Sewage|municipal wastewater]] still goes untreated into local rivers and streams.<ref>{{cite book |title=Environmentally Sound Technology for Wastewater and Stormwater Management: An International Source Book |author=UNEP International Environment |year=2002 |publisher=IWA |isbn=978-1-84339-008-4 |oclc=49204666}}</ref> Some 50 countries, with roughly a third of the world's population, also suffer from medium or high [[water scarcity]] and 17 of these extract more water annually than is recharged through their natural water cycles.<ref>{{cite book |title=Climate Change and Developing Countries |last1=Ravindranath |first1=Nijavalli H. |first2=Jayant A. |last2=Sathaye |year=2002 |publisher=Springer |isbn=978-1-4020-0104-8 |oclc=231965991}}</ref> The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

===Human uses===
{{Further|Water supply}}
[[File:Water withdrawals per capita, OWID.svg|thumb|upright=1.6|Total water withdrawals for agricultural, industrial and municipal purposes per capita, measured in cubic metres (m{{sup|3}}) per year in 2010<ref>{{cite web |title=Water withdrawals per capita |url=https://ourworldindata.org/grapher/water-withdrawals-per-capita |website=Our World in Data |access-date=6 March 2020 |archive-date=12 March 2020 |archive-url=https://web.archive.org/web/20200312112519/https://ourworldindata.org/grapher/water-withdrawals-per-capita |url-status=live }}</ref>]]

====Agriculture====
The most substantial human use of water is for agriculture, including irrigated agriculture, which accounts for as much as 80 to 90 percent of total human water consumption.<ref>{{cite web |url=http://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTYyNTA|archive-url=https://web.archive.org/web/20120301011840/http://www.wbcsd.org/includes/getTarget.asp?type=d&id=MTYyNTA|url-status=dead|archive-date=1 March 2012 |title=WBCSD Water Facts & Trends |access-date=25 July 2010}}</ref> In the United States, 42% of freshwater withdrawn for use is for irrigation, but the vast majority of water "consumed" (used and not returned to the environment) goes to agriculture.<ref name="Estimated use of water in the United States in 2015">{{cite book |chapter-url=https://pubs.er.usgs.gov/publication/cir1441 |chapter=Estimated use of water in the United States in 2015 |publisher=U.S. Geological Survey |doi=10.3133/cir1441 |title=Circular |year=2018 |last1=Dieter |first1=Cheryl A. |last2=Maupin |first2=Molly A. |last3=Caldwell |first3=Rodney R. |last4=Harris |first4=Melissa A. |last5=Ivahnenko |first5=Tamara I. |last6=Lovelace |first6=John K. |last7=Barber |first7=Nancy L. |last8=Linsey |first8=Kristin S. |page=76 |access-date=21 May 2019 |archive-date=28 April 2019 |archive-url=https://web.archive.org/web/20190428190636/https://pubs.er.usgs.gov/publication/cir1441 |url-status=live }}</ref>

Access to fresh water is often taken for granted, especially in developed countries that have built sophisticated water systems for collecting, purifying, and delivering water, and removing wastewater. But growing economic, demographic, and climatic pressures are increasing concerns about water issues, leading to increasing competition for fixed water resources, giving rise to the concept of [[peak water]].<ref>{{Cite journal |last1=Gleick |first1=P. H. |title=Peak Water |url=http://www.pacinst.org/press_center/press_releases/peak_water_pnas.pdf |access-date=11 October 2011 |year=2010 |doi=10.1073/pnas.1004812107 |pmid=20498082 |journal=Proceedings of the National Academy of Sciences |volume=107 |issue=125 |pages=11155–11162 |last2=Palaniappan |first2=M. |bibcode=2010PNAS..10711155G |pmc=2895062 |archive-url=https://web.archive.org/web/20111108224340/http://www.pacinst.org/press_center/press_releases/peak_water_pnas.pdf |archive-date=8 November 2011 |url-status=live |doi-access=free }}</ref> As populations and economies continue to grow, consumption of water-thirsty meat expands, and new demands rise for biofuels or new water-intensive industries, new water challenges are likely.<ref>United Nations Press Release POP/952 (13 March 2007). [https://www.un.org/News/Press/docs/2007/pop952.doc.htm "World population will increase by 2.5 billion by 2050"]. {{Webarchive|url=https://web.archive.org/web/20140727030018/http://www.un.org/News/Press/docs/2007/pop952.doc.htm |date=27 July 2014 }}</ref>

An assessment of water management in agriculture was conducted in 2007 by the [[International Water Management Institute]] in Sri Lanka to see if the world had sufficient water to provide food for its growing population.<ref>, Molden, D. (Ed). ''Water for food, Water for life: [[A Comprehensive Assessment of Water Management in Agriculture]].'' Earthscan/IWMI, 2007.</ref> It assessed the current availability of water for agriculture on a global scale and mapped out locations suffering from water scarcity. It found that a fifth of the world's people, more than 1.2 billion, live in areas of [[physical water scarcity]], where there is not enough water to meet all demands. A further 1.6 billion people live in areas experiencing [[economic water scarcity]], where the lack of investment in water or insufficient human capacity make it impossible for authorities to satisfy the demand for water. The report found that it would be possible to produce the food required in the future, but that continuation of today's food production and environmental trends would lead to crises in many parts of the world. To avoid a global water crisis, farmers will have to strive to increase productivity to meet growing demands for food, while industries and cities find ways to use water more efficiently.<ref>Chartres, C. and Varma, S. (2010) ''Out of water. From Abundance to Scarcity and How to Solve the World's Water Problems''. FT Press (US).</ref>

Water scarcity is also caused by production of water intensive products. For example, [[cotton]]: 1&nbsp;kg of cotton—equivalent of a pair of jeans—requires {{convert|10.9|m3}} water to produce. While cotton accounts for 2.4% of world water use, the water is consumed in regions that are already at a risk of water shortage. Significant environmental damage has been caused: for example, the diversion of water by the former [[Soviet Union]] from the [[Amu Darya]] and [[Syr Darya]] rivers to produce cotton was largely responsible for the disappearance of the [[Aral Sea]].<ref>{{cite web |first1=A. K. |last1=Chapagain |first2=A. Y. |last2=Hoekstra |first3=H. H. G. |last3=Savenije |first4=R. |last4=Guatam |title=The Water Footprint of Cotton Consumption |url=http://waterfootprint.org/media/downloads/Report18.pdf |publisher=[[IHE Delft Institute for Water Education]] |date=September 2005 |access-date=24 October 2019 |archive-url=https://web.archive.org/web/20190326141524/https://waterfootprint.org/media/downloads/Report18.pdf |archive-date=26 March 2019 |url-status=live }}</ref>

<gallery width="280px" height="200px">
File:Water requirement per tonne of food product, OWID.svg|Water requirement per tonne of food product
File:Subsurface drip emission on loamy soil.ogv|Water distribution in subsurface [[drip irrigation]]
File:SiphonTubes.JPG|[[Irrigation]] of field crops
</gallery>

====As a scientific standard====
On 7 April 1795, the gram was defined in France to be equal to "the absolute weight of a volume of pure water equal to a cube of one-hundredth of a meter, and at the temperature of melting ice".<ref>[http://smdsi.quartier-rural.org/histoire/18germ_3.htm "Décret relatif aux poids et aux mesures"] [Decree relating to weights and measures] (in French). 18 [[French revolutionary calendar|germinal]] an 3 (7 April 1795). {{Webarchive|url=https://web.archive.org/web/20130225163152/http://smdsi.quartier-rural.org/histoire/18germ_3.htm |date=25 February 2013 }}. quartier-rural.org</ref> For practical purposes though, a metallic reference standard was required, one thousand times more massive, the kilogram. Work was therefore commissioned to determine precisely the mass of one liter of water. In spite of the fact that the decreed definition of the gram specified water at {{convert|0|C}}—a highly reproducible ''temperature''—the scientists chose to redefine the standard and to perform their measurements at the temperature of highest water ''density'', which was measured at the time as {{convert|4|C}}.<ref>[http://histoire.du.metre.free.fr/fr/index.htm here "L'Histoire Du Mètre, La Détermination De L'Unité De Poids"] {{Webarchive|url=https://web.archive.org/web/20130725163108/http://histoire.du.metre.free.fr/fr/index.htm |date=25 July 2013 }}. histoire.du.metre.free.fr</ref>

The [[Kelvin temperature scale]] of the [[International System of Units|SI]] system was based on the [[triple point]] of water, defined as exactly {{convert|273.16|K|C F}}, but as of May 2019 is based on the [[Boltzmann constant]] instead. The scale is an [[absolute temperature]] scale with the same increment as the Celsius temperature scale, which was originally defined according to the [[boiling point]] (set to {{convert|100|C}}) and [[melting point]] (set to {{convert|0|C}}) of water.

Natural water consists mainly of the isotopes hydrogen-1 and oxygen-16, but there is also a small quantity of heavier isotopes oxygen-18, oxygen-17, and hydrogen-2 ([[deuterium]]). The percentage of the heavier isotopes is very small, but it still affects the properties of water. Water from rivers and lakes tends to contain less heavy isotopes than seawater. Therefore, standard water is defined in the [[Vienna Standard Mean Ocean Water]] specification.

====For drinking====
{{Main|Drinking water}}
[[File:Humanitarian aid OCPA-2005-10-28-090517a.jpg|thumb|A young girl drinking [[bottled water]]]]
[[File:2006 Global Water Availability.svg|thumb|right|Water availability: the fraction of the population using improved water sources by country]]
[[File:Roadside fresh water outlet from glacier, Nubra, Ladakh.jpg|thumb|Roadside fresh water outlet from glacier, [[Nubra]]]]
The [[human body]] contains from 55% to 78% water, depending on body size.<ref>[http://www.madsci.org/posts/archives/2000-05/958588306.An.r.html "Re: What percentage of the human body is composed of water?"] {{Webarchive|url=https://web.archive.org/web/20071125073713/http://madsci.org/posts/archives/2000-05/958588306.An.r.html |date=25 November 2007 }} Jeffrey Utz, M.D., The MadSci Network</ref>{{user-generated inline|date=November 2022}} To function properly, the body requires between {{convert|1|and|7|L|spell=in}}{{citation needed|date=April 2019}} of water per day to avoid [[dehydration]]; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though the British Dietetic Association advises that 2.5 liters of total water daily is the minimum to maintain proper hydration, including 1.8 liters (6 to 7 glasses) obtained directly from beverages.<ref>{{cite web |url=https://www.bbc.co.uk/health/healthy_living/nutrition/drinks_water.shtml |title=Healthy Water Living |work=BBC Health |access-date=1 February 2007 |url-status=dead |archive-url=https://web.archive.org/web/20070101100025/http://www.bbc.co.uk/health/healthy_living/nutrition/drinks_water.shtml |archive-date=1 January 2007}}</ref> Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather.<ref name=Rhoades_2003>{{cite book |vauthors=Rhoades RA, Tanner GA |title=Medical Physiology |publisher=Lippincott Williams & Wilkins |edition=2nd |location=Baltimore |year=2003 |isbn=978-0-7817-1936-0 |oclc=50554808 |url=https://archive.org/details/medicalphysiolog0000unse }}</ref>

Healthy kidneys can excrete 0.8 to 1 liter of water per hour, but stress such as exercise can reduce this amount. People can drink far more water than necessary while exercising, putting them at risk of [[water intoxication]] (hyperhydration), which can be fatal.<ref>{{cite journal |author=Noakes TD |author2=Goodwin N |author3=Rayner BL |display-authors=etal |title=Water intoxication: a possible complication during endurance exercise |journal=Medicine and Science in Sports and Exercise |year=1985 |volume=17 |issue=3 |pages=370–375 |pmid=4021781 |doi=10.1249/00005768-198506000-00012|doi-access=free }}</ref><ref>{{cite journal |vauthors=Noakes TD, Goodwin N, Rayner BL, Branken T, Taylor RK |title=Water intoxication: a possible complication during endurance exercise, 1985 |journal=Wilderness and Environmental Medicine |year=2005 |volume=16 |issue=4 |pages=221–227 |pmid=16366205 |doi=10.1580/1080-6032(2005)16[221:WIAPCD]2.0.CO;2|s2cid=28370290 |doi-access= }}</ref> The popular claim that "a person should consume eight glasses of water per day" seems to have no real basis in science.<ref>{{cite journal |title='Drink at least eight glasses of water a day.' Really? Is there scientific evidence for '8 × 8'? |journal=American Journal of Physiology. Regulatory, Integrative and Comparative Physiology |volume=283 |issue=5 |pages=R993–R1004 |doi=10.1152/ajpregu.00365.2002 |pmid=12376390 |year=2002 |last1=Valtin |first1=Heinz |s2cid=2256436 |url=http://pdfs.semanticscholar.org/3595/81eb8fa614a2f8c765dc1d4fed3c0e39ee7e.pdf |archive-url=https://web.archive.org/web/20190222112803/http://pdfs.semanticscholar.org/3595/81eb8fa614a2f8c765dc1d4fed3c0e39ee7e.pdf |url-status=dead |archive-date=22 February 2019 }}</ref> Studies have shown that extra water intake, especially up to {{convert|500|mL}} at mealtime, was associated with weight loss.<ref>{{cite journal |vauthors=Stookey JD, Constant F, Popkin BM, Gardner CD |title=Drinking water is associated with weight loss in overweight dieting women independent of diet and activity |journal=Obesity |volume=16 |issue=11 |pages=2481–2488 |date=November 2008 |pmid=18787524 |doi=10.1038/oby.2008.409|s2cid=24899383 }}</ref><ref>{{cite web |url=https://www.sciencedaily.com/releases/2010/08/100823142929.htm |title=Drink water to curb weight gain? Clinical trial confirms effectiveness of simple appetite control method |date=23 August 2010 |website=Science Daily |access-date=14 May 2017 |archive-url=https://web.archive.org/web/20170707071448/https://www.sciencedaily.com/releases/2010/08/100823142929.htm |archive-date=7 July 2017 |url-status=live}}</ref><ref>{{cite journal |vauthors=Dubnov-Raz G, Constantini NW, Yariv H, Nice S, Shapira N |title=Influence of water drinking on resting energy expenditure in overweight children |journal=International Journal of Obesity |volume=35 |issue=10 |pages=1295–1300 |date=October 2011 |pmid=21750519 |doi=10.1038/ijo.2011.130|s2cid=27561994 |doi-access= }}</ref><ref>{{cite journal |author=Dennis EA |author2=Dengo AL |author3=Comber DL |display-authors=etal |title=Water consumption increases weight loss during a hypocaloric diet intervention in middle-aged and older adults |journal=Obesity |volume=18 |issue=2 |pages=300–307 |date=February 2010 |pmid=19661958 |pmc=2859815 |doi=10.1038/oby.2009.235}}</ref><ref>{{cite journal |vauthors=Vij VA, Joshi AS |title=Effect of 'water induced thermogenesis' on body weight, body mass index and body composition of overweight subjects |journal=Journal of Clinical and Diagnostic Research |volume=7 |issue=9 |pages=1894–1896 |date=September 2013 |pmid=24179891 |pmc=3809630 |doi=10.7860/JCDR/2013/5862.3344}}</ref><ref>{{cite journal |vauthors=Muckelbauer R, Sarganas G, Grüneis A, Müller-Nordhorn J |title=Association between water consumption and body weight outcomes: a systematic review |journal=The American Journal of Clinical Nutrition |volume=98 |issue=2 |pages=282–299 |date=August 2013 |pmid=23803882 |doi=10.3945/ajcn.112.055061|s2cid=12265434 |doi-access=free }}</ref> Adequate fluid intake is helpful in preventing constipation.<ref>[http://www.webmd.com/digestive-disorders/water-a-fluid-way-to-manage-constipation "Water, Constipation, Dehydration, and Other Fluids"]. {{Webarchive|url=https://web.archive.org/web/20150304043454/http://www.webmd.com/digestive-disorders/water-a-fluid-way-to-manage-constipation |date=4 March 2015 }}. ''Science Daily''. Retrieved on 28 September 2015.</ref>

[[File:DIN 4844-2 D-P005.svg|thumb|right|[[Hazard symbol]] for non-potable water]]
An original recommendation for water intake in 1945 by the Food and Nutrition Board of the [[U.S. National Research Council]] read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods."<ref>{{cite book |title=Food and Nutrition Board, National Academy of Sciences. Recommended Dietary Allowances |publisher=National Research Council, Reprint and Circular Series, No. 122 |year=1945 |pages=3–18}}</ref> The latest dietary reference intake report by the U.S. National Research Council in general recommended, based on the median total water intake from US survey data (including food sources): {{convert|3.7|L}} for men and {{convert|2.7|L}} of water total for women, noting that water contained in food provided approximately 19% of total water intake in the survey.<ref>{{Cite book|url=https://www.nap.edu/read/10925/chapter/6|title=4 Water {{!}} Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate |publisher=The National Academies Press|doi=10.17226/10925|year=2005|isbn=978-0-309-09169-5|author1=Institute of Medicine|author2=Food Nutrition Board|author3=Standing Committee on the Scientific Evaluation of Dietary Reference Intakes|author4=Panel on Dietary Reference Intakes for Electrolytes and Water|access-date=11 January 2017|archive-url=https://web.archive.org/web/20170113063638/https://www.nap.edu/read/10925/chapter/6|archive-date=13 January 2017|url-status=live}}</ref>

Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. The US [[Institute of Medicine]] recommends that, on average, men consume {{convert|3|L}} and women {{convert|2.2|L}}; pregnant women should increase intake to {{convert|2.4|L}} and breastfeeding women should get 3 liters (12 cups), since an especially large amount of fluid is lost during nursing.<ref>{{cite web |url=http://www.mayoclinic.com/health/water/NU00283 |title=Water: How much should you drink every day? |publisher=Mayo Clinic |access-date=25 July 2010 |archive-url=https://web.archive.org/web/20101204012725/http://www.mayoclinic.com/health/water/NU00283 |archive-date=4 December 2010 |url-status=live}}</ref> Also noted is that normally, about 20% of water intake comes from food, while the rest comes from drinking water and beverages ([[Caffeine|caffeinated]] included). Water is excreted from the body in multiple forms; through [[urine]] and [[feces]], through [[sweat]]ing, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well.

Humans require water with few impurities. Common impurities include metal salts and oxides, including copper, iron, calcium and lead,<ref>''Conquering Chemistry'' (4th ed.), 2008</ref>{{full citation needed|date=November 2022}} and harmful bacteria, such as ''[[Vibrio]]''. Some [[solutes]] are acceptable and even desirable for taste enhancement and to provide needed [[electrolyte]]s.<ref>{{cite book |last1=Maton |first1=Anthea |first2=Jean |last2=Hopkins |first3=Charles William |last3=McLaughlin |first4=Susan |last4=Johnson |first5=Maryanna Quon |last5=Warner |first6=David |last6=LaHart |first7=Jill D. |last7=Wright |title=Human Biology and Health |publisher=Prentice Hall |year=1993 |location=Englewood Cliffs, New Jersey |isbn=978-0-13-981176-0 |oclc=32308337 |url=https://archive.org/details/humanbiologyheal00scho }}</ref>

The single largest (by volume) freshwater resource suitable for drinking is [[Lake Baikal]] in Siberia.<ref>{{cite book |url=https://archive.org/details/bub_gb_ujf0kkNF2H8C |page=[https://archive.org/details/bub_gb_ujf0kkNF2H8C/page/n140 125] |title=Water: a shared responsibility |author=Unesco |publisher=Berghahn Books |year=2006 |isbn=978-1-84545-177-6}}</ref>

====Washing====
{{excerpt|washing}}

====Transportation====
{{excerpt|maritime transport|only=paragraphs}}

====Chemical uses====
Water is widely used in chemical reactions as a [[solvent]] or [[reactant]] and less commonly as a [[solute]] or catalyst. In inorganic reactions, water is a common solvent, dissolving many ionic compounds, as well as other polar compounds such as [[ammonia]] and [[Hydrogen chalcogenide|compounds closely related to water]]. In organic reactions, it is not usually used as a reaction solvent, because it does not dissolve the reactants well and is [[amphoteric]] (acidic ''and'' basic) and [[nucleophilic]]. Nevertheless, these properties are sometimes desirable. Also, acceleration of [[Diels-Alder reaction]]s by water has been observed. [[Supercritical water]] has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently.

====Heat exchange====
Water and steam are a common fluid used for [[heat exchanger|heat exchange]], due to its availability and high [[Heat capacity of water|heat capacity]], both for cooling and heating. Cool water may even be naturally available from a lake or the sea. It is especially effective to transport heat through [[vaporization]] and [[condensation]] of water because of its large [[latent heat of vaporization]]. A disadvantage is that metals commonly found in industries such as steel and copper are [[oxidation|oxidized]] faster by untreated water and steam. In almost all [[thermal power station]]s, water is used as the working fluid (used in a closed-loop between boiler, steam turbine, and condenser), and the coolant (used to exchange the waste heat to a water body or carry it away by [[evaporation]] in a [[cooling tower]]). In the United States, cooling power plants is the largest use of water.<ref name="Water Use in the United States">[http://nationalatlas.gov/articles/water/a_wateruse.html "Water Use in the United States"], ''National Atlas''. {{webarchive|url=https://web.archive.org/web/20090814045418/http://nationalatlas.gov/articles/water/a_wateruse.html |date=14 August 2009 }}</ref>

In the [[nuclear power]] industry, water can also be used as a [[neutron moderator]]. In most [[nuclear reactor]]s, water is both a coolant and a moderator. This provides something of a passive safety measure, as removing the water from the reactor also [[void coefficient|slows the nuclear reaction down]]. However other methods are favored for stopping a reaction and it is preferred to keep the nuclear core covered with water so as to ensure adequate cooling.

====Fire considerations====
[[File:MH-60S Helicopter dumps water onto Fire.jpg|right|thumb|Water is used for [[fire fighting|fighting]] [[wildfire]]s.]]
Water has a high heat of vaporization and is relatively inert, which makes it a good [[Fire fighting#Use of water|fire extinguishing]] fluid. The evaporation of water carries heat away from the fire. It is dangerous to use water on fires involving oils and organic solvents because many organic materials float on water and the water tends to spread the burning liquid.

Use of water in fire fighting should also take into account the hazards of a [[steam explosion]], which may occur when water is used on very hot fires in confined spaces, and of a hydrogen explosion, when substances which react with water, such as certain metals or hot carbon such as coal, [[charcoal]], or [[coke (fuel)|coke]] graphite, decompose the water, producing [[water gas]].

The power of such explosions was seen in the [[Chernobyl disaster]], although the water involved in this case did not come from fire-fighting but from the reactor's own water cooling system. A steam explosion occurred when the extreme overheating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result of a reaction between steam and hot [[zirconium]].

Some metallic oxides, most notably those of [[alkali metals]] and [[alkaline earth metals]], produce so much heat in reaction with water that a fire hazard can develop. The alkaline earth oxide [[Calcium oxide|quicklime]], also known as calcium oxide, is a mass-produced substance that is often transported in paper bags. If these are soaked through, they may ignite as their contents react with water.<ref>{{cite web |title=Material Safety Data Sheet: Quicklime |url=https://www.lhoist.com/sites/lhoist/files/lna_msds_quicklime_2012-3.pdf |publisher=Lhoist North America |date=6 August 2012 |access-date=24 October 2019 |archive-url=https://web.archive.org/web/20160705030051/http://www.lhoist.com/sites/lhoist/files/lna_msds_quicklime_2012-3.pdf |archive-date=5 July 2016 |url-status=live }}</ref>

====Recreation====
{{Main|Water sport (recreation)}}
[[File:Johny Cay.jpg|thumb|right|[[San Andrés (island)|San Andrés island]], [[Colombia]]]]

Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, [[waterskiing]], [[boating]], [[surfing]] and [[Underwater diving|diving]]. In addition, some sports, like [[ice hockey]] and [[ice skating]], are played on ice. Lakesides, beaches and [[water park]]s are popular places for people to go to relax and enjoy recreation. Many find the sound and appearance of flowing water to be calming, and fountains and other flowing water structures are popular decorations. Some keep fish and other flora and fauna inside [[aquarium]]s or ponds for show, fun, and companionship. Humans also use water for snow sports such as [[skiing]], [[sledding]], [[snowmobiling]] or [[snowboarding]], which require the water to be at a low temperature either as ice or crystallized into [[snow]].

====Water industry====
The [[water industry]] provides drinking water and [[wastewater]] services (including [[sewage treatment]]) to households and industry. [[Water supply]] facilities include [[water well]]s, [[cistern]]s for [[rainwater harvesting]], [[water supply network]]s, and [[water purification]] facilities, [[water tank]]s, [[water tower]]s, [[water pipe]]s including old [[Aqueduct (watercourse)|aqueducts]]. [[Atmospheric water generator]]s are in development.

Drinking water is often collected at [[spring (hydrosphere)|springs]], extracted from artificial [[Boring (earth)|borings]] (wells) in the ground, or pumped from lakes and rivers. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Other water sources include rainwater collection. Water may require purification for human consumption. This may involve the removal of undissolved substances, dissolved substances and harmful [[microbe]]s. Popular methods are [[filter (water)|filtering]] with sand which only removes undissolved material, while [[Water chlorination|chlorination]] and [[boiling]] kill harmful microbes. [[Distillation]] does all three functions. More advanced techniques exist, such as [[reverse osmosis]]. [[Desalination]] of abundant [[seawater]] is a more expensive solution used in coastal [[arid]] [[climate]]s.

The distribution of drinking water is done through [[municipal water system]]s, tanker delivery or as [[bottled water]]. Governments in many countries have programs to distribute water to the needy at no charge.

Reducing usage by using drinking (potable) water only for human consumption is another option. In some cities such as Hong Kong, seawater is extensively used for flushing toilets citywide in order to [[Water conservation|conserve freshwater resources]].

[[Water pollution|Polluting water]] may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as [[externality|externalities]] for which the market cannot account. Thus other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population, victims of this pollution. [[Pharmaceuticals]] consumed by humans often end up in the waterways and can have detrimental effects on [[marine biology|aquatic]] life if they [[bioaccumulation|bioaccumulate]] and if they are not [[biodegradable]].

Municipal and [[industrial wastewater treatment|industrial wastewater]] are typically treated at [[wastewater treatment plant]]s. Mitigation of polluted [[surface runoff]] is addressed through a variety of [[Surface runoff#Mitigation and treatment|prevention and treatment techniques]].
{{gallery
|align=center
|File:Water carrier in India.jpg|A water-carrier in India, 1882. In many places where running water is not available, water has to be transported by people.
|File:TapWater-china.JPG|A manual water [[pump]] in China
|File:Usine Bret MG 1648.jpg|[[Water purification]] facility
|File:Reverse osmosis desalination plant.JPG|[[Reverse osmosis]] (RO) [[desalination]] plant in [[Barcelona]], Spain
}}

====Industrial applications====
Many industrial processes rely on reactions using chemicals dissolved in water, suspension of solids in water [[slurry|slurries]] or using water to dissolve and extract substances, or to wash products or process equipment. Processes such as [[mining]], [[chemical pulping]], [[pulp bleaching]], [[paper manufacturing]], textile production, dyeing, printing, and cooling of power plants use large amounts of water, requiring a dedicated water source, and often cause significant water pollution.

Water is used in [[power generation]]. [[Hydroelectricity]] is electricity obtained from [[hydropower]]. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the motion of water. Typically a dam is constructed on a river, creating an artificial lake behind it. Water flowing out of the lake is forced through turbines that turn generators.

{{wide image|200407-sandouping-sanxiadaba-4.med.jpg|800px|[[Three Gorges Dam]] is the [[List of the largest hydroelectric power stations|largest hydro-electric power station]] in the world.}}

Pressurized water is used in [[Hydrodemolition|water blasting]] and [[water jet cutter]]s. High pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in the cooling of machinery to prevent overheating, or prevent saw blades from overheating.

Water is also used in many industrial processes and machines, such as the [[steam turbine]] and [[heat exchanger]], in addition to its use as a chemical [[solvent]]. Discharge of untreated water from industrial uses is [[water pollution|pollution]]. Pollution includes discharged solutes (chemical pollution) and discharged coolant water ([[thermal pollution]]). Industry requires pure water for many applications and uses a variety of purification techniques both in water supply and discharge.

====Food processing====
[[File:Cuisson des pates.jpg|thumb|Water can be used to cook foods such as [[noodles]].]]
[[File:Sterilewater.jpg|thumb|upright|Sterile water for injection]]
[[Boiling]], [[steaming]], and [[simmering]] are popular cooking methods that often require immersing food in water or its gaseous state, steam.<ref>{{Cite book|url=https://books.google.com/books?id=xZHUAAAAMAAJ&pg=PA54|title=A Course in Household Arts: Part I|last=Duff|first=Loretto Basil|date=1916|publisher=Whitcomb & Barrows|access-date=3 December 2017|archive-date=14 April 2021|archive-url=https://web.archive.org/web/20210414164100/https://books.google.com/books?id=xZHUAAAAMAAJ&pg=PA54|url-status=live}}</ref> Water is also used for [[dishwashing]]. Water also plays many critical roles within the field of [[food science]].

[[Solutes]] such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water are affected by solutes, as well as [[air pressure]], which is in turn affected by altitude. Water boils at lower temperatures with the lower air pressure that occurs at higher elevations. One [[mole (unit)|mole]] of sucrose (sugar) per kilogram of water raises the boiling point of water by {{convert|0.51|C-change|3}}, and one mole of salt per kg raises the boiling point by {{convert|1.02|C-change|3}}; similarly, increasing the number of dissolved particles lowers water's freezing point.<ref name="vaclacik">{{cite book |title=Essentials of Food Science |url=https://books.google.com/books?id=iCCsvwZrguUC |year=2007 |last1=Vaclavik |first1=Vickie A. |last2=Christian |first2=Elizabeth W. |publisher=Springer |isbn=978-0-387-69939-4 |access-date=31 August 2020 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414164352/https://books.google.com/books?id=iCCsvwZrguUC |url-status=live }}</ref>

Solutes in water also affect water activity that affects many chemical reactions and the growth of microbes in food.<ref name="deman">{{cite book |url=https://books.google.com/books?id=kDYJ7a1HbD0C&pg=PA434 |title=Principles of Food Chemistry |year=1999 |last=DeMan |first=John M. |publisher=Springer |isbn=978-0-8342-1234-3 |access-date=31 August 2020 |archive-date=14 April 2021 |archive-url=https://web.archive.org/web/20210414185952/https://books.google.com/books?id=kDYJ7a1HbD0C&pg=PA434 |url-status=live }}</ref> Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water.<ref name="vaclacik" /> Solutes in water lower water activity—this is important to know because most bacterial growth ceases at low levels of water activity.<ref name="deman" /> Not only does microbial growth affect the safety of food, but also the preservation and shelf life of food.

[[Water hardness]] is also a critical factor in food processing and may be altered or treated by using a chemical ion exchange system. It can dramatically affect the quality of a product, as well as playing a role in sanitation. Water hardness is classified based on concentration of calcium carbonate the water contains. Water is classified as soft if it contains less than 100&nbsp;mg/L (UK)<ref name="DEFRA">{{cite web |url=http://dwi.defra.gov.uk/consumers/advice-leaflets/hardness_map.pdf |title=Map showing the rate of hardness in mg/L as Calcium carbonate in England and Wales |publisher=[[Department for Environment, Food and Rural Affairs|DEFRA]] Drinking Water Inspectorate |date=2009 |access-date=18 May 2015 |archive-url=https://web.archive.org/web/20150529054911/http://dwi.defra.gov.uk/consumers/advice-leaflets/hardness_map.pdf |archive-date=29 May 2015 |url-status=live }}</ref> or less than 60&nbsp;mg/L (US).<ref name="USGS">{{cite web |url=https://water.usgs.gov/edu/hardness.html |publisher=US Geological Service |title=Water hardness |date=8 April 2014 |access-date=18 May 2015 |archive-url=https://web.archive.org/web/20150518204909/https://water.usgs.gov/edu/hardness.html |archive-date=18 May 2015 |url-status=live}}</ref>

According to a report published by the Water Footprint organization in 2010, a single kilogram of beef requires {{convert|15|e3L|e3impgal+e3usgal}} of water; however, the authors also make clear that this is a global average and circumstantial factors determine the amount of water used in beef production.<ref>{{cite report |title=The green, blue and grey water footprint of farm animals and animal products, Value of Water |series=Research Report Series |volume=1|issue=48 |url=http://www.waterfootprint.org/Reports/Report-48-WaterFootprint-AnimalProducts-Vol1.pdf |publisher=UNESCO – IHE Institute for Water Education |access-date=30 January 2014 |first1=M. M. |last1=Mekonnen |first2=A. Y. |last2=Hoekstra |date=December 2010 |archive-url=https://web.archive.org/web/20140527104135/http://www.waterfootprint.org/Reports/Report-48-WaterFootprint-AnimalProducts-Vol1.pdf |archive-date=27 May 2014 |url-status=live}}</ref>

====Medical use====
[[Water for injection]] is on the [[World Health Organization]]'s [[World Health Organization's list of essential medicines|list of essential medicines]].<ref>{{cite web |url=http://apps.who.int/iris/bitstream/10665/93142/1/EML_18_eng.pdf?ua=1 |title=WHO Model List of EssentialMedicines |date=October 2013 |website=World Health Organization |access-date=22 April 2014 |archive-url=https://web.archive.org/web/20140423005004/http://apps.who.int/iris/bitstream/10665/93142/1/EML_18_eng.pdf?ua=1 |archive-date=23 April 2014 |url-status=live}}</ref>