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Atmosphere of Mars: 0.03%[24]
Atmosphere of Ceres[25]
Atmosphere of Jupiter: 0.0004%[26]
in icesonly; and that of itsmoon Europa[27]
Atmosphere of Saturnin icesonly;and that of itsmoons Titan(stratospheric), Enceladus
: 91%[28]and Dione(exosphere) Atmosphere of Uranusin trace
amounts below 50 bar[29]
Atmosphere of Neptunefound in thedeeper layers[30]
Extrasolar planetatmospheres:including those of HD 189733b[31]and HD 209458 b,[32]Tau Botisb,[33]HAT-P-11b,[34][35]XO-1b, WASP-12b, WASP-17b, and WASP-19b.[36]
Stellar atmospheres: not limited to
cooler stars and even detected in gianthot stars such as Betelgeuse, MuCephei,AntaresandArcturus.[35][37]
https://en.wikipedia.org/wiki/Atmosphere_of_Marshttps://en.wikipedia.org/wiki/Water#cite_note-Rapp2012-24https://en.wikipedia.org/wiki/Atmosphere_of_Cereshttps://en.wikipedia.org/wiki/Atmosphere_of_Cereshttps://en.wikipedia.org/wiki/Atmosphere_of_Jupiterhttps://en.wikipedia.org/wiki/Water#cite_note-26https://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Atmosphere_of_Saturnhttps://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Water#cite_note-Hansen-28https://en.wikipedia.org/wiki/Dione_(moon)https://en.wikipedia.org/wiki/Atmosphere_of_Uranushttps://en.wikipedia.org/wiki/Water#cite_note-FOOTNOTEEncrenaz200392-29https://en.wikipedia.org/wiki/Atmosphere_of_Neptunehttps://en.wikipedia.org/wiki/Water#cite_note-hubbard-30https://en.wikipedia.org/wiki/Extrasolar_planethttps://en.wikipedia.org/wiki/HD_189733_bhttps://en.wikipedia.org/wiki/HD_189733_bhttps://en.wikipedia.org/wiki/Water#cite_note-31https://en.wikipedia.org/wiki/HD_209458_bhttps://en.wikipedia.org/wiki/Water#cite_note-Space.com_water-32https://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis_bhttps://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis_bhttps://en.wikipedia.org/wiki/Water#cite_note-33https://en.wikipedia.org/wiki/HAT-P-11bhttps://en.wikipedia.org/wiki/Water#cite_note-NASA-20140924-34https://en.wikipedia.org/wiki/XO-1bhttps://en.wikipedia.org/wiki/WASP-12bhttps://en.wikipedia.org/wiki/WASP-12bhttps://en.wikipedia.org/wiki/WASP-17bhttps://en.wikipedia.org/wiki/WASP-19bhttps://en.wikipedia.org/wiki/Water#cite_note-NASA-20131203-36https://en.wikipedia.org/wiki/Stellar_atmospherehttps://en.wikipedia.org/wiki/Betelgeusehttps://en.wikipedia.org/wiki/Mu_Cepheihttps://en.wikipedia.org/wiki/Mu_Cepheihttps://en.wikipedia.org/wiki/Antareshttps://en.wikipedia.org/wiki/Arcturushttps://en.wikipedia.org/wiki/Water#cite_note-Hanslmeier2010-35https://en.wikipedia.org/wiki/Water#cite_note-Hanslmeier2010-35https://en.wikipedia.org/wiki/Water#cite_note-Hanslmeier2010-35https://en.wikipedia.org/wiki/Arcturushttps://en.wikipedia.org/wiki/Antareshttps://en.wikipedia.org/wiki/Mu_Cepheihttps://en.wikipedia.org/wiki/Mu_Cepheihttps://en.wikipedia.org/wiki/Betelgeusehttps://en.wikipedia.org/wiki/Stellar_atmospherehttps://en.wikipedia.org/wiki/Water#cite_note-NASA-20131203-36https://en.wikipedia.org/wiki/WASP-19bhttps://en.wikipedia.org/wiki/WASP-17bhttps://en.wikipedia.org/wiki/WASP-12bhttps://en.wikipedia.org/wiki/WASP-12bhttps://en.wikipedia.org/wiki/XO-1bhttps://en.wikipedia.org/wiki/Water#cite_note-NASA-20140924-34https://en.wikipedia.org/wiki/Water#cite_note-NASA-20140924-34https://en.wikipedia.org/wiki/HAT-P-11bhttps://en.wikipedia.org/wiki/Water#cite_note-33https://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis_bhttps://en.wikipedia.org/wiki/Tau_Bo%C3%B6tis_bhttps://en.wikipedia.org/wiki/Water#cite_note-Space.com_water-32https://en.wikipedia.org/wiki/HD_209458_bhttps://en.wikipedia.org/wiki/Water#cite_note-31https://en.wikipedia.org/wiki/HD_189733_bhttps://en.wikipedia.org/wiki/HD_189733_bhttps://en.wikipedia.org/wiki/Extrasolar_planethttps://en.wikipedia.org/wiki/Water#cite_note-hubbard-30https://en.wikipedia.org/wiki/Atmosphere_of_Neptunehttps://en.wikipedia.org/wiki/Water#cite_note-FOOTNOTEEncrenaz200392-29https://en.wikipedia.org/wiki/Atmosphere_of_Uranushttps://en.wikipedia.org/wiki/Dione_(moon)https://en.wikipedia.org/wiki/Water#cite_note-Hansen-28https://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Atmosphere_of_Saturnhttps://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Water#cite_note-26https://en.wikipedia.org/wiki/Atmosphere_of_Jupiterhttps://en.wikipedia.org/wiki/Atmosphere_of_Cereshttps://en.wikipedia.org/wiki/Atmosphere_of_Cereshttps://en.wikipedia.org/wiki/Water#cite_note-Rapp2012-24https://en.wikipedia.org/wiki/Atmosphere_of_Mars7/24/2019 sdhfcn djcnfg gh h
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Circumstellar disks: including those ofmore than half of T Tauri starssuch
asAA Tauri
[35]
as well as TWHydrae,[38][39]IRC +10216[40]andAPM08279+5255,[18][19]VY CanisMajorisand S Persei.[37]
Liquid water
Turquoise water with a bit of Sun.
Liquid water is known to be present onEarth, covering 71% of its surface.Scientists believe liquid water is presentin the Saturnian moons ofEnceladus, asa 10-kilometre thick ocean approximately3040 kilometres below Enceladus' southpolar surface,[41][42]and Titan, as a
https://en.wikipedia.org/wiki/Circumstellar_diskhttps://en.wikipedia.org/wiki/T_Tauri_starhttps://en.wikipedia.org/wiki/AA_Taurihttps://en.wikipedia.org/wiki/AA_Taurihttps://en.wikipedia.org/wiki/TW_Hydraehttps://en.wikipedia.org/wiki/TW_Hydraehttps://en.wikipedia.org/wiki/Water#cite_note-38https://en.wikipedia.org/wiki/IRC_%2B10216https://en.wikipedia.org/wiki/IRC_%2B10216https://en.wikipedia.org/wiki/APM_08279%2B5255https://en.wikipedia.org/wiki/APM_08279%2B5255https://en.wikipedia.org/wiki/Water#cite_note-Clavin-18https://en.wikipedia.org/wiki/VY_Canis_Majorishttps://en.wikipedia.org/wiki/VY_Canis_Majorishttps://en.wikipedia.org/wiki/S_Perseihttps://en.wikipedia.org/wiki/Water#cite_note-Lund_Observatory-37https://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Water#cite_note-NASA-20140403-41https://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/File:Turquoise_Water.jpghttps://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/Water#cite_note-NASA-20140403-41https://en.wikipedia.org/wiki/Water#cite_note-NASA-20140403-41https://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Water#cite_note-Lund_Observatory-37https://en.wikipedia.org/wiki/S_Perseihttps://en.wikipedia.org/wiki/VY_Canis_Majorishttps://en.wikipedia.org/wiki/VY_Canis_Majorishttps://en.wikipedia.org/wiki/Water#cite_note-Clavin-18https://en.wikipedia.org/wiki/Water#cite_note-Clavin-18https://en.wikipedia.org/wiki/APM_08279%2B5255https://en.wikipedia.org/wiki/APM_08279%2B5255https://en.wikipedia.org/wiki/IRC_%2B10216https://en.wikipedia.org/wiki/IRC_%2B10216https://en.wikipedia.org/wiki/Water#cite_note-38https://en.wikipedia.org/wiki/Water#cite_note-38https://en.wikipedia.org/wiki/TW_Hydraehttps://en.wikipedia.org/wiki/TW_Hydraehttps://en.wikipedia.org/wiki/AA_Taurihttps://en.wikipedia.org/wiki/AA_Taurihttps://en.wikipedia.org/wiki/T_Tauri_starhttps://en.wikipedia.org/wiki/Circumstellar_disk7/24/2019 sdhfcn djcnfg gh h
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subsurface layer, possibly mixedwith ammonia.[43]Jupiter's
moon Europahas surface characteristicswhich suggest a subsurface liquid waterocean.[44]Liquid water may also exist onJupiter's moon Ganymedeas a layersandwiched between high pressure iceand rock.[45]
Currently, there are two planets known tohave flowing liquid water on theirsurfaces: Earth and Mars.[46]
Water ice
Water is present as ice on:
Mars: under the regolith and at thepoles
Earth-Moon system: mainly as icesheetson Earth and in Lunar cratersand volcanic rocks[47]NASA reported
the detection of water molecules byNASA's Moon Mineralogy Mapperaboard the Indian Space Research
https://en.wikipedia.org/wiki/Ammoniahttps://en.wikipedia.org/wiki/Water#cite_note-43https://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Water#cite_note-44https://en.wikipedia.org/wiki/Ganymede_(moon)https://en.wikipedia.org/wiki/Water#cite_note-45https://en.wikipedia.org/wiki/Marshttps://en.wikipedia.org/wiki/Water#cite_note-46https://en.wikipedia.org/wiki/Water_on_Marshttps://en.wikipedia.org/wiki/Ice_sheethttps://en.wikipedia.org/wiki/Ice_sheethttps://en.wikipedia.org/wiki/Water#cite_note-47https://en.wikipedia.org/wiki/Water#cite_note-47https://en.wikipedia.org/wiki/Ice_sheethttps://en.wikipedia.org/wiki/Ice_sheethttps://en.wikipedia.org/wiki/Water_on_Marshttps://en.wikipedia.org/wiki/Water#cite_note-46https://en.wikipedia.org/wiki/Marshttps://en.wikipedia.org/wiki/Water#cite_note-45https://en.wikipedia.org/wiki/Ganymede_(moon)https://en.wikipedia.org/wiki/Water#cite_note-44https://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Water#cite_note-43https://en.wikipedia.org/wiki/Ammonia7/24/2019 sdhfcn djcnfg gh h
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Organization's Chandrayaan-1spacecraft in September 2009.[48]
Jupiter's moons: Europa's surface andalso that of Ganymede
Saturn: in the planet's ringsystem[49]and on the surface andmantle of Titanand Enceladus
Pluto-Charonsystem[49]
Cometsand related (Kuiperbeltand Oort cloudobjects).
And may also be present on:
Mercury's poles[50]
Ceres
Tethys
Exotic forms
Water and other volatilesprobablycomprise much of the internal structuresof Uranusand Neptuneand the water in
the deeper layers may be in the formof ionic waterin which the moleculesbreak down into a soup of hydrogen andoxygen ions, and deeper down
https://en.wikipedia.org/wiki/Water#cite_note-48https://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Rings_of_Saturnhttps://en.wikipedia.org/wiki/Rings_of_Saturnhttps://en.wikipedia.org/wiki/Water#cite_note-Sparrow-49https://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Plutohttps://en.wikipedia.org/wiki/Charon_(moon)https://en.wikipedia.org/wiki/Water#cite_note-Sparrow-49https://en.wikipedia.org/wiki/Cometshttps://en.wikipedia.org/wiki/Kuiper_belthttps://en.wikipedia.org/wiki/Kuiper_belthttps://en.wikipedia.org/wiki/Oort_cloudhttps://en.wikipedia.org/wiki/Water#cite_note-50https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)https://en.wikipedia.org/wiki/Tethys_(moon)https://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Uranushttps://en.wikipedia.org/wiki/Neptunehttps://en.wikipedia.org/w/index.php?title=Ionic_water&action=edit&redlink=1https://en.wikipedia.org/w/index.php?title=Ionic_water&action=edit&redlink=1https://en.wikipedia.org/wiki/Neptunehttps://en.wikipedia.org/wiki/Uranushttps://en.wikipedia.org/wiki/Volatileshttps://en.wikipedia.org/wiki/Tethys_(moon)https://en.wikipedia.org/wiki/Ceres_(dwarf_planet)https://en.wikipedia.org/wiki/Water#cite_note-50https://en.wikipedia.org/wiki/Oort_cloudhttps://en.wikipedia.org/wiki/Kuiper_belthttps://en.wikipedia.org/wiki/Kuiper_belthttps://en.wikipedia.org/wiki/Cometshttps://en.wikipedia.org/wiki/Water#cite_note-Sparrow-49https://en.wikipedia.org/wiki/Charon_(moon)https://en.wikipedia.org/wiki/Plutohttps://en.wikipedia.org/wiki/Enceladus_(moon)https://en.wikipedia.org/wiki/Titan_(moon)https://en.wikipedia.org/wiki/Water#cite_note-Sparrow-49https://en.wikipedia.org/wiki/Rings_of_Saturnhttps://en.wikipedia.org/wiki/Rings_of_Saturnhttps://en.wikipedia.org/wiki/Europa_(moon)https://en.wikipedia.org/wiki/Water#cite_note-487/24/2019 sdhfcn djcnfg gh h
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as superionic waterin which the oxygencrystallises but the hydrogen ions float
around freely within the oxygen lattice.
[51]
Water and habitable zoneFurther information: Water distribution onEarth
The existence of liquid water, and to alesser extent its gaseousand solid forms,on Earth are vital to the existence of lifeon Earthas we know it. The Earth islocated in the habitable zoneof the solarsystem; if it were slightly closer to orfarther from the Sun(about 5%, or about
8 million kilometers), the conditions whichallow the three forms to be presentsimultaneously would be far less likely toexist.[52][53]
Earth's gravityallows it to hold
an atmosphere. Water vapor and carbondioxide in the atmosphere provide atemperature buffer (greenhouse effect)which helps maintain a relatively steady
https://en.wikipedia.org/wiki/Superionic_waterhttps://en.wikipedia.org/wiki/Water#cite_note-newscientist.com-51https://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Gashttps://en.wikipedia.org/wiki/Organismhttps://en.wikipedia.org/wiki/Organismhttps://en.wikipedia.org/wiki/Habitable_zonehttps://en.wikipedia.org/wiki/Solar_systemhttps://en.wikipedia.org/wiki/Solar_systemhttps://en.wikipedia.org/wiki/Sunhttps://en.wikipedia.org/wiki/Water#cite_note-52https://en.wikipedia.org/wiki/Gravityhttps://en.wikipedia.org/wiki/Celestial_body_atmospherehttps://en.wikipedia.org/wiki/Greenhouse_effecthttps://en.wikipedia.org/wiki/Greenhouse_effecthttps://en.wikipedia.org/wiki/Celestial_body_atmospherehttps://en.wikipedia.org/wiki/Gravityhttps://en.wikipedia.org/wiki/Water#cite_note-52https://en.wikipedia.org/wiki/Water#cite_note-52https://en.wikipedia.org/wiki/Sunhttps://en.wikipedia.org/wiki/Solar_systemhttps://en.wikipedia.org/wiki/Solar_systemhttps://en.wikipedia.org/wiki/Habitable_zonehttps://en.wikipedia.org/wiki/Organismhttps://en.wikipedia.org/wiki/Organismhttps://en.wikipedia.org/wiki/Gashttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Water#cite_note-newscientist.com-51https://en.wikipedia.org/wiki/Superionic_water7/24/2019 sdhfcn djcnfg gh h
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surface temperature. If Earth weresmaller, a thinner atmosphere would
allow temperature extremes, thuspreventing the accumulation of waterexcept in polar ice caps(as on Mars).
The surface temperature of Earth hasbeen relatively constant through geologictimedespite varying levels of incoming
solar radiation (insolation), indicating thata dynamic process governs Earth'stemperature via a combination ofgreenhouse gases and surface oratmospheric albedo. This proposal is
known as the Gaia hypothesis.The state of water on a planet dependson ambient pressure, which isdetermined by the planet's gravity. If aplanet is sufficiently massive, the wateron it may be solid even at hightemperatures, because of the highpressure caused by gravity, as it wasobserved on exoplanets Gliese 436b[54]and GJ 1214 b.[55]
https://en.wikipedia.org/wiki/Polar_ice_caphttps://en.wikipedia.org/wiki/Marshttps://en.wikipedia.org/wiki/Geologic_timehttps://en.wikipedia.org/wiki/Geologic_timehttps://en.wikipedia.org/wiki/Insolationhttps://en.wikipedia.org/wiki/Albedohttps://en.wikipedia.org/wiki/Gaia_hypothesishttps://en.wikipedia.org/wiki/Gliese_436_bhttps://en.wikipedia.org/wiki/Gliese_436_bhttps://en.wikipedia.org/wiki/Water#cite_note-54https://en.wikipedia.org/wiki/GJ_1214_bhttps://en.wikipedia.org/wiki/Water#cite_note-55https://en.wikipedia.org/wiki/Water#cite_note-55https://en.wikipedia.org/wiki/GJ_1214_bhttps://en.wikipedia.org/wiki/Water#cite_note-54https://en.wikipedia.org/wiki/Gliese_436_bhttps://en.wikipedia.org/wiki/Gliese_436_bhttps://en.wikipedia.org/wiki/Gaia_hypothesishttps://en.wikipedia.org/wiki/Albedohttps://en.wikipedia.org/wiki/Insolationhttps://en.wikipedia.org/wiki/Geologic_timehttps://en.wikipedia.org/wiki/Geologic_timehttps://en.wikipedia.org/wiki/Marshttps://en.wikipedia.org/wiki/Polar_ice_cap7/24/2019 sdhfcn djcnfg gh h
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On Earth
Main articles: Hydrologyand Water
distribution on Earth
Water covers 71% of the Earth's surface;the oceans contain 96.5% of the Earth'swater. TheAntarctic ice sheet, whichcontains 61% of all fresh water on Earth,
is visible at the bottom. Condensedatmospheric water can be seenas clouds, contributing to theEarth's albedo.
Hydrology is the study of the movement,
distribution, and quality of waterthroughout the Earth. The study of thedistribution of water is hydrography. Thestudy of the distribution and movement of
https://en.wikipedia.org/wiki/Hydrologyhttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Antarctic_ice_sheethttps://en.wikipedia.org/wiki/Cloudhttps://en.wikipedia.org/wiki/Albedohttps://en.wikipedia.org/wiki/Hydrographyhttps://en.wikipedia.org/wiki/File:The_Earth_seen_from_Apollo_17.jpghttps://en.wikipedia.org/wiki/Hydrographyhttps://en.wikipedia.org/wiki/Albedohttps://en.wikipedia.org/wiki/Cloudhttps://en.wikipedia.org/wiki/Antarctic_ice_sheethttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Water_distribution_on_Earthhttps://en.wikipedia.org/wiki/Hydrology7/24/2019 sdhfcn djcnfg gh h
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groundwater is hydrogeology, of glaciersis glaciology, of inland waters
is limnologyand distribution of oceansis oceanography. Ecological processeswith hydrology are in focusof ecohydrology.
The collective mass of water found on,under, and over the surface of a planet is
called the hydrosphere. Earth'sapproximate water volume (the totalwater supply of the world) is1,338,000,000 km3(321,000,000 mi3).[2]
Liquid water is found inbodies of water,
such as anocean, sea, lake,river,stream, canal, pond, or puddle. The majority of water onEarth is sea water. Water is also presentin the atmosphere in solid, liquid, andvapor states. It also exists asgroundwater in aquifers.
Water is important in many geologicalprocesses. Groundwater is present in
https://en.wikipedia.org/wiki/Hydrogeologyhttps://en.wikipedia.org/wiki/Glaciologyhttps://en.wikipedia.org/wiki/Limnologyhttps://en.wikipedia.org/wiki/Oceanographyhttps://en.wikipedia.org/wiki/Ecohydrologyhttps://en.wikipedia.org/wiki/Hydrospherehttps://en.wikipedia.org/wiki/Water#cite_note-b1-2https://en.wikipedia.org/wiki/Water#cite_note-b1-2https://en.wikipedia.org/wiki/Body_of_waterhttps://en.wikipedia.org/wiki/Seahttps://en.wikipedia.org/wiki/Lakehttps://en.wikipedia.org/wiki/Riverhttps://en.wikipedia.org/wiki/Streamhttps://en.wikipedia.org/wiki/Canalhttps://en.wikipedia.org/wiki/Pondhttps://en.wikipedia.org/wiki/Pondhttps://en.wikipedia.org/wiki/Puddlehttps://en.wikipedia.org/wiki/Sea_waterhttps://en.wikipedia.org/wiki/Aquiferhttps://en.wikipedia.org/wiki/Aquiferhttps://en.wikipedia.org/wiki/Sea_waterhttps://en.wikipedia.org/wiki/Puddlehttps://en.wikipedia.org/wiki/Pondhttps://en.wikipedia.org/wiki/Pondhttps://en.wikipedia.org/wiki/Canalhttps://en.wikipedia.org/wiki/Streamhttps://en.wikipedia.org/wiki/Riverhttps://en.wikipedia.org/wiki/Lakehttps://en.wikipedia.org/wiki/Seahttps://en.wikipedia.org/wiki/Body_of_waterhttps://en.wikipedia.org/wiki/Water#cite_note-b1-2https://en.wikipedia.org/wiki/Hydrospherehttps://en.wikipedia.org/wiki/Ecohydrologyhttps://en.wikipedia.org/wiki/Oceanographyhttps://en.wikipedia.org/wiki/Limnologyhttps://en.wikipedia.org/wiki/Glaciologyhttps://en.wikipedia.org/wiki/Hydrogeology7/24/2019 sdhfcn djcnfg gh h
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most rocks, and the pressure of thisgroundwater affects patterns of faulting.
Water in the mantleis responsible for themelt thatproduces volcanoesat subduction zones.On the surface of the Earth, water isimportant in both chemical andphysical weatheringprocesses. Water,
and to a lesser but still significant extent,ice, are also responsible for a largeamount of sediment transportthat occurson the surface of the earth. Depositionoftransported sediment forms many typesof sedimentary rocks, which make upthe geologic recordof Earth history.
Water cycleMain article: Water cycle
Water cycle
https://en.wikipedia.org/wiki/Rock_(geology)https://en.wikipedia.org/wiki/Fault_(geology)https://en.wikipedia.org/wiki/Mantle_(geology)https://en.wikipedia.org/wiki/Volcanohttps://en.wikipedia.org/wiki/Subduction_zonehttps://en.wikipedia.org/wiki/Weatheringhttps://en.wikipedia.org/wiki/Sediment_transporthttps://en.wikipedia.org/wiki/Deposition_(geology)https://en.wikipedia.org/wiki/Sedimentary_rockhttps://en.wikipedia.org/wiki/Geologic_recordhttps://en.wikipedia.org/wiki/History_of_the_Earthhttps://en.wikipedia.org/wiki/Water_cyclehttps://en.wikipedia.org/wiki/Water_cyclehttps://en.wikipedia.org/wiki/File:Water_cycle.pnghttps://en.wikipedia.org/wiki/Water_cyclehttps://en.wikipedia.org/wiki/Water_cyclehttps://en.wikipedia.org/wiki/History_of_the_Earthhttps://en.wikipedia.org/wiki/Geologic_recordhttps://en.wikipedia.org/wiki/Sedimentary_rockhttps://en.wikipedia.org/wiki/Deposition_(geology)https://en.wikipedia.org/wiki/Sediment_transporthttps://en.wikipedia.org/wiki/Weatheringhttps://en.wikipedia.org/wiki/Subduction_zonehttps://en.wikipedia.org/wiki/Volcanohttps://en.wikipedia.org/wiki/Mantle_(geology)https://en.wikipedia.org/wiki/Fault_(geology)https://en.wikipedia.org/wiki/Rock_(geology)7/24/2019 sdhfcn djcnfg gh h
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The water cycle(known scientifically asthe hydrologic cycle) refers to the
continuous exchange of water withinthe hydrosphere, betweenthe atmosphere, soilwater, surfacewater, groundwater, and plants.
Water moves perpetually through each ofthese regions in the water
cycleconsisting of following transferprocesses:
evaporationfrom oceans and otherwater bodies into the airand transpirationfrom land plants and
animals into air. precipitation, from water vapor
condensing from the air and falling toearth or ocean.
runofffrom the land usually reaching
the sea.Most water vapor over the oceansreturns to the oceans, but winds carrywater vapor over land at the same rate
https://en.wikipedia.org/wiki/Water_cyclehttps://en.wikipedia.org/wiki/Hydrospherehttps://en.wikipedia.org/wiki/Earth_atmospherehttps://en.wikipedia.org/wiki/Soilhttps://en.wikipedia.org/wiki/Surface_waterhttps://en.wikipedia.org/wiki/Surface_waterhttps://en.wikipedia.org/wiki/Groundwaterhttps://en.wikipedia.org/wiki/Planthttps://en.wikipedia.org/wiki/Evaporationhttps://en.wikipedia.org/wiki/Transpirationhttps://en.wikipedia.org/wiki/Precipitation_(meteorology)https://en.wikipedia.org/wiki/Runoff_(water)https://en.wikipedia.org/wiki/Seahttps://en.wikipedia.org/wiki/Seahttps://en.wikipedia.org/wiki/Runoff_(water)https://en.wikipedia.org/wiki/Precipitation_(meteorology)https://en.wikipedia.org/wiki/Transpirationhttps://en.wikipedia.org/wiki/Evaporationhttps://en.wikipedia.org/wiki/Planthttps://en.wikipedia.org/wiki/Groundwaterhttps://en.wikipedia.org/wiki/Surface_waterhttps://en.wikipedia.org/wiki/Surface_waterhttps://en.wikipedia.org/wiki/Soilhttps://en.wikipedia.org/wiki/Earth_atmospherehttps://en.wikipedia.org/wiki/Hydrospherehttps://en.wikipedia.org/wiki/Water_cycle7/24/2019 sdhfcn djcnfg gh h
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as runoff into the sea, about 47 Ttperyear. Over land, evaporation and
transpiration contribute another 72 Tt peryear. Precipitation, at a rate of 119 Tt peryear over land, has several forms: mostcommonly rain, snow, and hail, withsome contributionfrom fogand dew.[56]Dew is small drops
of water that are condensed when a highdensity of water vapor meets a coolsurface. Dew usually forms in themorning when the temperature is thelowest, just before sunrise and when thetemperature of the earth's surface startsto increase.[57]Condensed water in theair may also refractsunlighttoproduce rainbows.
Water runoff often collectsover watershedsflowing into rivers. A
mathematical model used to simulateriver or stream flow and calculate waterquality parameters is a hydrologicaltransport model. Some water is diverted
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toirrigationfor agriculture. Rivers andseas offer opportunity
for traveland commerce.Through erosion, runoff shapes theenvironment creatingriver valleysand deltaswhich providerich soil and level ground for theestablishment of population centers.
A floodoccurs when an area of land,usually low-lying, is covered with water. Itis when a river overflows its banks orflood comes from the sea. A droughtisan extended period of months or yearswhen a region notes a deficiency in itswater supply. This occurs when a regionreceives consistently below averageprecipitation.
Fresh water storage
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The Bay of Fundyat high tide (left) andlow tide (right)
Main article: Water resources
Some runoff water is trapped for periodsof time, for example in lakes. At high
altitude, during winter, and in the farnorth and south, snow collects in icecaps, snow pack and glaciers. Water alsoinfiltrates the ground and goes intoaquifers. This groundwater later flows
back to the surface in springs, or morespectacularly in hot springsand geysers.Groundwater is also extracted artificiallyinwells. This water storage is important,
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since clean, fresh water is essential tohuman and other land-based life. In
many parts of the world, it is in shortsupply.
Sea water and tidesMain articles: Seawaterand Tides
Sea watercontains about 3.5% saltonaverage, plus smaller amounts of othersubstances. The physical properties ofsea water differ from fresh water in someimportant respects. It freezes at a lowertemperature (about 1.9C) and itsdensity increases with decreasing
temperature to the freezing point, insteadof reaching maximum density at atemperature above freezing. The salinityof water in major seas varies from about0.7% in the Baltic Seato 4.0% in the RedSea.
Tidesare the cyclic rising and falling oflocal sea levels caused by the tidalforcesof the Moon and the Sun acting on
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the oceans. Tides cause changes in thedepth of the marine and estuarinewater
bodies and produce oscillating currentsknown as tidal streams. The changingtide produced at a given location is theresult of the changing positions of theMoon and Sun relative to the Earthcoupled with the effects of Earth
rotationand the local bathymetry. Thestrip of seashore that is submerged athigh tide and exposed at low tide,the intertidal zone, is an importantecological product of ocean tides.
Effects on life
An oasisis an isolated watersourcewith vegetationin adesert.
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Overview
of photosynthesisandrespiration. Water(at right), together with carbon dioxide(CO2), form oxygen and organiccompounds (at left), which can berespired to water and (CO2).
From a biologicalstandpoint, water hasmany distinct properties that are criticalfor the proliferation of life. It carries outthis role by allowing organiccompoundsto react in ways thatultimately allow replication. All known
forms of life depend on water. Water isvital both as a solventin which many ofthe body's solutes dissolve and as anessential part of
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manymetabolicprocesses within thebody. Metabolism is the sum total of
anabolism and catabolism. In anabolism,water is removed from molecules(through energy requiring enzymaticchemical reactions) in order to growlarger molecules (e.g. starches,triglycerides and proteins for storage of
fuels and information). In catabolism,water is used to break bonds in order togenerate smaller molecules (e.g.glucose, fatty acids and amino acids tobe used for fuels for energy use or otherpurposes). Without water, theseparticular metabolic processes could notexist.
Water is fundamental to photosynthesisand respiration. Photosynthetic cells usethe sun's energy to split off water's
hydrogen from oxygen. Hydrogen iscombined with CO2(absorbed from air orwater) to form glucose and releaseoxygen. All living cells use such fuels and
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oxidize the hydrogen and carbon tocapture the sun's energy and reform
water and CO2in the process (cellularrespiration).
Water is also central to acid-baseneutrality and enzyme function. An acid,a hydrogen ion (H+, that is, a proton)donor, can be neutralized by a base, a
proton acceptor such as a hydroxide ion(OH) to form water. Water is consideredto be neutral, with a pH(the negative logof the hydrogen ion concentration) of7.Acidshave pH values less than 7
while baseshave values greater than 7.Aquatic life formsMain articles: HydrobiologyandAquaticplant
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Some of the biodiversityof a coral reef
Some marine diatomsakeyphytoplanktongroup
Earth surface waters are filled with life.The earliest life forms appeared in water;nearly all fishlive exclusively in water,and there are many types of marinemammals, such as dolphinsand whales.
Some kinds of animals, suchas amphibians, spend portions of theirlives in water and portions on land.Plants such as kelpand algaegrow in
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the water and are the basis for someunderwater ecosystems. Planktonis
generally the foundation of the oceanfoodchain.
Aquatic vertebrates must obtain oxygento survive, and they do so in variousways. Fish have gillsinstead of lungs,although some species of fish, such as
the lungfish, have both. Marinemammals, such as dolphins,whales, otters, and sealsneed to surfaceperiodically to breathe air. Someamphibians are able to absorb oxygen
through their skin. Invertebrates exhibit awide range of modifications to survive inpoorly oxygenated waters includingbreathing tubes (see insectand molluscsiphons) and gills(Carcinus). Howeveras invertebrate life evolved in an aquatic
habitat most have little or nospecialisation for respiration in water.
Effects on human civilization
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Water fountain
Civilization has historically flourishedaround rivers and major
waterways; Mesopotamia, the so-calledcradle of civilization, was situatedbetween the majorrivers Tigrisand Euphrates; the ancientsociety of the Egyptiansdependedentirely upon the Nile.
Large metropoliseslike Rotterdam, London, Montreal, Paris, New YorkCity, BuenosAires, Shanghai, Tokyo, Chicago,and Hong Kongowe their success in part
to their easy accessibility via water andthe resultant expansion of trade. Islandswith safe water ports, like Singapore,have flourished for the same reason. In
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places such as North Africaandthe Middle East, where water is more
scarce, access to clean drinking waterwas and is a major factor in humandevelopment.
Health and pollution
An environmental science programastudent from Iowa StateUniversitysampling water
Water fit for human consumption is calleddrinking water or potable water. Waterthat is not potable may be made potableby filtration or distillation, or by a rangeof other methods.
Water that is not fit for drinking but is notharmful for humans when used forswimming or bathing is called by variousnames other than potable or drinking
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water, and is sometimes called safewater, or "safe for bathing". Chlorine is a
skin and mucous membrane irritant thatis used to make water safe for bathing ordrinking. Its use is highly technical and isusually monitored by governmentregulations (typically 1 part per million(ppm) for drinking water, and 12 ppm of
chlorine not yet reacted with impuritiesfor bathing water). Water for bathing maybe maintained in satisfactorymicrobiological condition using chemicaldisinfectants such as chlorineor ozoneorby the use of ultravioletlight.
In the USA, non-potable formsof wastewatergenerated by humans maybe referred to as greywater, which istreatable and thus easily able to be madepotable again, and blackwater, which
generally contains sewageand otherforms of waste which require furthertreatmentin order to be made reusable.Greywater composes 5080% of
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residential wastewater generated by ahousehold's sanitation equipment
(sinks, showersand kitchenrunoff, butnot toilets, which generate blackwater.)These terms may have differentmeanings in other countries and cultures.
This natural resource is becomingscarcer in certain places, and its
availability is a major social andeconomic concern. Currently, about abillion people around the world routinelydrink unhealthy water. Most countriesaccepted the goal of halving by 2015 the
number of people worldwide who do nothave access to safe waterand sanitationduring the 2003 G8 Eviansummit.[58]Even if this difficult goal ismet, it will still leave more than anestimated half a billion people without
access to safe drinking water and over abillion without access to adequatesanitation. Poor water qualityand badsanitation are deadly; some five million
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deaths a year are caused by polluteddrinking water. The World Health
Organizationestimates that safewatercould prevent 1.4 million childdeaths from diarrheaeach year.[59]
Water, however, is not a finite resource,but rather re-circulated as potable waterin precipitation in quantities many
degrees of magnitude higher than humanconsumption. Therefore, it is therelatively small quantity of water inreserve in the earth (about 1% of ourdrinking water supply, which is
replenished in aquifers around every 1 to10 years), that is a non-renewableresource, and it is, rather, the distributionof potable and irrigation water which isscarce, rather than the actual amount ofit that exists on the earth. Water-poor
countries use importation of goods as theprimary method of importing water (toleave enough for local humanconsumption), since the manufacturing
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process uses around 10 to 100 timesproducts' masses in water.
In the developing world, 90% ofall wastewaterstill goes untreated intolocal rivers and streams.[60]Some 50countries, with roughly a third of theworld's population, also suffer frommedium or high water stress, and 17 of
these extract more water annually than isrecharged through their natural watercycles.[61]The strain not only affectssurface freshwater bodies like rivers andlakes, but it also degrades groundwater
resources.Human usesFurther information: Water supply
Agriculture
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Water distribution in subsurface dripirrigation
Irrigationof field crops
The most important use of waterin agricultureis for irrigation, which is akey component to produce enough food.Irrigation takes up to 90% of waterwithdrawn in some developingcountries[62]and significant proportions in
more economically developed countries(in the United States, 30% of freshwaterusage is for irrigation).[63]
Fifty years ago, the common perceptionwas that water was an infinite resource.
At this time, there were fewer than halfthe current number of people on theplanet. People were not as wealthy astoday, consumed fewer calories and ate
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less meat, so less water was needed toproduce their food. They required a third
of the volume of water we presently takefrom rivers. Today, the competition forthe fixed amount of water resources ismuch more intense, giving rise to theconcept of peak water.[64]This is becausethere are now nearly seven billion people
on the planet, their consumption of water-thirsty meat and vegetables is rising, andthere is increasing competition for waterfrom industry, urbanisationand biofuelcrops. In future, even more water will beneeded to produce food because theEarth's population is forecast to rise to 9billion by 2050.[65]
An assessment of water management inagriculture was conducted in 2007 bythe International Water Management
Institutein Sri Lankato see if the worldhad sufficient water to provide food for itsgrowing population.[66]It assessed thecurrent availability of water for agriculture
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on a global scale and mapped outlocations suffering from water scarcity. It
found that a fifth of the world's people,more than 1.2 billion, live in areasof physical water scarcity, where there isnot enough water to meet all demands. Afurther 1.6 billion people live in areasexperiencing economic water scarcity,
where the lack of investment in water orinsufficient human capacity make itimpossible for authorities to satisfy thedemand for water. The report found thatit would be possible to produce the foodrequired in future, but that continuation oftoday's food production andenvironmental trends would lead to crisesin many parts of the world. To avoid aglobal water crisis, farmers will have tostrive to increase productivity to meet
growing demands for food, while industryand cities find ways to use water moreefficiently.[67]
As a scientific standard
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On 7 April 1795, the gramwas definedin Franceto be equal to "the absolute
weight of a volume of pure water equal toa cube of one hundredth of a meter, andat the temperature of melting ice."[68]Forpractical purposes though, a metallicreference standard was required, onethousand times more massive,
the kilogram. Work was thereforecommissioned to determine precisely themass of one literof water. In spite of thefact that the decreed definition of thegram specified water at 0 C a highlyreproducible temperaturethescientists chose to redefine the standardand to perform their measurements at thetemperature of highest water density,which was measured at the time as 4 C(39 F).[69]
The Kelvin temperature scaleof the SIsystem is based on the triple pointofwater, defined as exactly 273.16 K or0.01 C. The scale is an absolute
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temperaturescale with the sameincrement as the Celsius temperature
scale, which was originally definedaccording the boiling point(set to 100 C)and melting point(set to 0 C) of water.
Natural water consists mainly of theisotopes hydrogen-1 and oxygen-16, butthere is also a small quantity of heavier
isotopes such as hydrogen-2(deuterium). The amount of deuteriumoxides or heavy wateris very small, but itstill affects the properties of water. Waterfrom rivers and lakes tends to contain
less deuterium than seawater. Therefore,standard water is defined in the ViennaStandard Mean OceanWaterspecification.
For drinkingMain article: Drinking water
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A young girl drinking bottled water
Water availability: fraction of populationusing improved water sources by country
The human bodycontains from 55% to78% water, depending on bodysize.[70]To function properly, the bodyrequires between one and seven liters ofwater per dayto avoid dehydration; theprecise amount depends on the level ofactivity, temperature, humidity, and otherfactors. Most of this is ingested through
foods or beverages other than drinkingstraight water. It is not clear how muchwater intake is needed by healthy people,though most specialists agree that
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approximately 2 liters (6 to 7 glasses) ofwater daily is the minimum to maintain
proper hydration.
[71]
Medical literaturefavors a lower consumption, typically 1liter of water for an average male,excluding extra requirements due to fluidloss from exercise or warm weather.[72]
For those who have healthy kidneys, it is
rather difficult to drink too much water,but (especially in warm humid weatherand while exercising) it is dangerous todrink too little. People can drink far morewater than necessary while exercising,
however, putting them at risk ofwaterintoxication(hyperhydration), which canbe fatal.[73][74]The popular claim that "aperson should consume eight glasses ofwater per day" seems to have no realbasis in science.[75]Studies have shown
that extra water intake, especially up to500 ml at mealtime was conducive toweight loss.[76][77][78][79][80][81]Adequate fluid
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intake is helpful in preventingconstipation.[82]
Hazard symbolfor non-potable water
An original recommendation for waterintake in 1945 by the Food and NutritionBoard of the United States NationalResearch Councilread: "An ordinary
standard for diverse persons is 1 milliliterfor each calorie of food. Most of thisquantity is contained in preparedfoods."[83]The latest dietary referenceintake report by theUnited StatesNational Research Councilin generalrecommended (including food sources):3.7 liters for men and 2.7 liters of watertotal for women.[84]
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Specifically, pregnantand breastfeedingwomen need additional fluids to stay
hydrated. The Institute of Medicine(U.S.)recommends that, on average, menconsume 3.0 liters and women 2.2 liters;pregnant women should increase intaketo 2.4 liters (10 cups) and breastfeedingwomen should get 3 liters (12 cups),
since an especially large amount of fluidis lost during nursing.[85]Also noted isthat normally, about 20% of water intakecomes from food, while the rest comesfrom drinking water and beverages(caffeinatedincluded). Water is excretedfrom the body in multiple forms;through urineand feces,through sweating, and by exhalation ofwater vapor in the breath. With physicalexertion and heat exposure, water loss
will increase an
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