Water 1

Water

Water in three states: liquid, solid (ice), and (invisible) water vapor in the air.Clouds are accumulations of water droplets, condensed from vapor-saturated air.

Water is a chemical substance with thechemical formula H2O. Its moleculecontains one oxygen and two hydrogenatoms connected by covalent bonds. Wateris a liquid at ambient conditions, but it oftenco-exists on Earth with its solid state, ice,and gaseous state, water vapor or steam.

Water covers 70.9% of the Earth's surface,[1]

and is vital for all known forms of life.[2] OnEarth, it is found mostly in oceans and otherlarge water bodies, with 1.6% of waterbelow ground in aquifers and 0.001% in theair as vapor, clouds (formed of solid andliquid water particles suspended in air), and precipitation.[3] Oceans hold 97% of surface water, glaciers and polar icecaps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth'swater is contained within biological bodies and manufactured products.

Water on Earth moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation,and runoff, usually reaching the sea. Over land, evaporation and transpiration contribute to the precipitation overland.

Clean drinking water is essential to human and other lifeforms. Access to safe drinking water has improved steadilyand substantially over the last decades in almost every part of the world.[4] [5] There is a clear correlation betweenaccess to safe water and GDP per capita.[6] However, some observers have estimated that by 2025 more than half ofthe world population will be facing water-based vulnerability.[7] A recent report (November 2009) suggests that by2030, in some developing regions of the world, water demand will exceed supply by 50%.[8] Water plays animportant role in the world economy, as it functions as a solvent for a wide variety of chemical substances andfacilitates industrial cooling and transportation. Approximately 70% of freshwater is consumed by agriculture.[9]

Chemical and physical properties

Model of hydrogen bonds between molecules ofwater

Water is the chemical substance with chemical formula H2O: onemolecule of water has two hydrogen atoms covalently bonded to asingle oxygen atom.

Water appears in nature in all three common states of matter and maytake many different forms on Earth: water vapor and clouds in the sky;seawater and icebergs in the polar oceans; glaciers and rivers in themountains; and the liquid in aquifers in the ground.

At high temperatures and pressures, such as in the interior of giantplanets, it is argued that water exists as ionic water in which themolecules break down into a soup of hydrogen and oxygen ions, and ateven higher pressures as superionic water in which the oxygencrystallises but the hydrogen ions float around freely within the oxygenlattice.[10]

The major chemical and physical properties of water are:

Water 2

Impact from a water drop causes an upward"rebound" jet surrounded by circular capillary

waves.

Snowflakes by Wilson Bentley, 1902

Dew drops adhering to a spider web

• Water is a tasteless, odorless liquid at standard temperature andpressure. The color of water and ice is, intrinsically, a very slightblue hue, although water appears colorless in small quantities. Icealso appears colorless, and water vapor is essentially invisible as agas.[11]

• Water is transparent, and thus aquatic plants can live within thewater because sunlight can reach them. Only strong UV light isslightly absorbed.

• Since the water molecule is not linear and the oxygen atom has ahigher electronegativity than hydrogen atoms, it carries a slightnegative charge, whereas the hydrogen atoms are slightly positive.As a result, water is a polar molecule with an electrical dipolemoment. Water also can form an unusually large number ofintermolecular hydrogen bonds (four) for a molecule of its size.These factors lead to strong attractive forces between molecules ofwater, giving rise to water's high surface tension[12] and capillaryforces. The capillary action refers to the tendency of water to moveup a narrow tube against the force of gravity. This property is reliedupon by all vascular plants, such as trees.

• Water is a good solvent and is often referred to as the universalsolvent. Substances that dissolve in water, e.g., salts, sugars, acids,alkalis, and some gases – especially oxygen, carbon dioxide(carbonation) are known as hydrophilic (water-loving) substances,while those that do not mix well with water (e.g., fats and oils), areknown as hydrophobic (water-fearing) substances.

• All the major components in cells (proteins, DNA andpolysaccharides) are also dissolved in water.

• Pure water has a low electrical conductivity, but this increasessignificantly with the dissolution of a small amount of ionic materialsuch as sodium chloride.

• The boiling point of water (and all other liquids) is dependent on thebarometric pressure. For example, on the top of Mt. Everest waterboils at 68 °C (154 °F), compared to 100 °C (212 °F) at sea level.Conversely, water deep in the ocean near geothermal vents canreach temperatures of hundreds of degrees and remain liquid.

• Water has the second highest molar specific heat capacity of anyknown substance, after ammonia, as well as a high heat ofvaporization (40.65 kJ·mol−1), both of which are a result of the extensive hydrogen bonding between itsmolecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuationsin temperature.

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Capillary action of water compared to mercury

• The maximum density of water occurs at 3.98 °C (39.16 °F).[13] Ithas the anomalous property of becoming less dense, not more, whenit is cooled down to its solid form, ice. It expands to occupy 9%greater volume in this solid state, which accounts for the fact of icefloating on liquid water.

ADR label for transporting goods dangerouslyreactive with water

• Water is miscible with many liquids, such as ethanol, in allproportions, forming a single homogeneous liquid. On the otherhand, water and most oils are immiscible usually forming layersaccording to increasing density from the top. As a gas, water vaporis completely miscible with air.

• Water forms an azeotrope with many other solvents.• Water can be split by electrolysis into hydrogen and oxygen.• As an oxide of hydrogen, water is formed when hydrogen or

hydrogen-containing compounds burn or react with oxygen oroxygen-containing compounds. Water is not a fuel, it is anend-product of the combustion of hydrogen. The energy required tosplit water into hydrogen and oxygen by electrolysis or any othermeans is greater than the energy released when the hydrogen andoxygen recombine.[14]

• Elements which are more electropositive than hydrogen such as lithium, sodium, calcium, potassium and caesiumdisplace hydrogen from water, forming hydroxides. Being a flammable gas, the hydrogen given off is dangerousand the reaction of water with the more electropositive of these elements may be violently explosive.

Taste and odorWater can dissolve many different substances, giving it varying tastes and odors. Humans and other animals havedeveloped senses which enable them to evaluate the potability of water by avoiding water that is too salty or putrid.The taste of spring water and mineral water, often advertised in marketing of consumer products, derives from theminerals dissolved in it. However, pure H2O is tasteless and odorless. The advertised purity of spring and mineralwater refers to absence of toxins, pollutants and microbes.

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Distribution of water in nature

Water in the universeMuch of the universe's water is produced as a byproduct of star formation. When stars are born, their birth isaccompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts thesurrounding gas, the shock waves that are created compress and heat the gas. The water observed is quicklyproduced in this warm dense gas.[15]

Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably exists in abundancein other galaxies, too, because its components, hydrogen and oxygen, are among the most abundant elements in theuniverse. Interstellar clouds eventually condense into solar nebulae and solar systems such as ours.Water vapor is present in• Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere[16]

• Atmosphere of Venus: 0.002%• Earth's atmosphere: ~0.40% over full atmosphere, typically 1–4% at surface• Atmosphere of Mars: 0.03%• Atmosphere of Jupiter: 0.0004%• Atmosphere of Saturn – in ices only• Enceladus (moon of Saturn): 91%• exoplanets known as HD 189733 b[17] and HD 209458 b.[18]

Liquid water is present on• Earth – 71% of surfaceStrong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus. Jupiter'smoon Europa may have liquid water in the form as a 100 km deep subsurface ocean, which would amount to morewater than is in all the Earth's oceans.Water ice is present on• Earth – mainly as ice sheets• polar ice caps on Mars• Moon• Titan• Europa• Saturn's rings[19]

• Enceladus• Pluto and Charon[19]

• Comets and comet source populations (Kuiper belt and Oort cloud objects).Water ice may be present on Ceres and Tethys. Water and other volatiles probably comprise much of the internalstructures of Uranus and Neptune and the water in the deeper layers may be in the form of ionic water in which themolecules break down into a soup of hydrogen and oxygen ions, and deeper down as superionic water in which theoxygen crystallises but the hydrogen ions float around freely within the oxygen lattice.[20]

Some of the Moon's minerals contain water molecules. For instance, in 2008 a laboratory device which ejects andidentifies particles found small amounts of the compound in the inside of volcanic pearls brought from Moon toEarth by the Apollo 15 crew in 1971.[21] NASA reported the detection of water molecules by NASA's MoonMineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September2009.[22]

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Water and habitable zone

The Solar System along center row range of possible habitable zones of varying star sizes.

The existence of liquid water, and to alesser extent its gaseous and solidforms, on Earth are vital to theexistence of life on Earth as we knowit. The Earth is located in the habitablezone of the solar system; if it wereslightly closer to or farther from theSun (about 5%, or about 8 millionkilometers), the conditions whichallow the three forms to be presentsimultaneously would be far less likelyto exist.[23] [24]

Earth's gravity allows it to hold anatmosphere. Water vapor and carbondioxide in the atmosphere provide atemperature buffer (greenhouse effect) which helps maintain a relatively steady surface temperature. If Earth weresmaller, a thinner atmosphere would allow temperature extremes, thus preventing the accumulation of water exceptin polar ice caps (as on Mars).

The surface temperature of Earth has been relatively constant through geologic time despite varying levels ofincoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via acombination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis.The state of water on a planet depends on ambient pressure, which is determined by the planet's gravity. If a planet issufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused bygravity, as it was observed on exoplanets Gliese 436 b[25] and GJ 1214 b.[26]

There are various theories about origin of water on Earth.

Water on Earth

A graphical distribution of the locations of water on Earth.

Hydrology is the study of themovement, distribution, and quality ofwater throughout the Earth. The studyof the distribution of water ishydrography. The study of thedistribution and movement ofgroundwater is hydrogeology, ofglaciers is glaciology, of inland watersis limnology and distribution of oceansis oceanography. Ecological processeswith hydrology are in focus ofecohydrology.

The collective mass of water found on,under, and over the surface of a planet

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Water covers 71% of the Earth's surface; theoceans contain 97.2% of the Earth's water. TheAntarctic ice sheet, which contains 61% of allfresh water on Earth, is visible at the bottom.Condensed atmospheric water can be seen as

clouds, contributing to the Earth's albedo.

is called the hydrosphere. Earth's approximate water volume (the totalwater supply of the world) is 1,360,000,000 km3 (326,000,000 mi3).

Groundwater and fresh water are useful or potentially useful to humansas water resources.

Liquid water is found in bodies of water, such as an ocean, sea, lake,river, stream, canal, pond, or puddle. The majority of water on Earth issea water. Water is also present in the atmosphere in solid, liquid, andvapor states. It also exists as groundwater in aquifers.

Water is important in many geological processes. Groundwater ispresent in most rocks, and the pressure of this groundwater affectspatterns of faulting. Water in the mantle is responsible for the melt thatproduces volcanoes at subduction zones. On the surface of the Earth,water is important in both chemical and physical weathering processes.Water and, to a lesser but still significant extent, ice, are alsoresponsible for a large amount of sediment transport that occurs on thesurface of the earth. Deposition of transported sediment forms manytypes of sedimentary rocks, which make up the geologic record of

Earth history.

Water cycle

Water cycle

The water cycle (known scientificallyas the hydrologic cycle) refers to thecontinuous exchange of water withinthe hydrosphere, between theatmosphere, soil water, surface water,groundwater, and plants.

Water moves perpetually through eachof these regions in the water cycleconsisting of following transferprocesses:

• evaporation from oceans and otherwater bodies into the air andtranspiration from land plants andanimals into air.

• precipitation, from water vaporcondensing from the air and falling to earth or ocean.

• runoff from the land usually reaching the sea.Most water vapor over the oceans returns to the oceans, but winds carry water vapor over land at the same rate asrunoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year.Precipitation, at a rate of 107 Tt per year over land, has several forms: most commonly rain, snow, and hail, withsome contribution from fog and dew. Condensed water in the air may also refract sunlight to produce rainbows.

Water runoff often collects over watersheds flowing into rivers. A mathematical model used to simulate river or stream flow and calculate water quality parameters is hydrological transport model. Some of water is diverted to irrigation for agriculture. Rivers and seas offer opportunity for travel and commerce. Through erosion, runoff shapes

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the environment creating river valleys and deltas which provide rich soil and level ground for the establishment ofpopulation centers. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a riveroverflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes adeficiency in its water supply. This occurs when a region receives consistently below average precipitation.

Fresh water storage

High tide (left) and low tide (right)Some runoff water is trapped for periods of time, for example in lakes. At high altitude, during winter, and in the farnorth and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes intoaquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs andgeysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh wateris essential to human and other land-based life. In many parts of the world, it is in short supply.

Sea waterSea water contains about 3.5% salt on average, plus smaller amounts of other substances. The physical properties ofsea water differ from fresh water in some important respects. It freezes at a lower temperature (about –1.9 °C) and itsdensity increases with decreasing temperature to the freezing point, instead of reaching maximum density at atemperature above freezing. The salinity of water in major seas varies from about 0.7% in the Baltic Sea to 4.0% inthe Red Sea.

TidesTides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sunacting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produceoscillating currents known as tidal streams. The changing tide produced at a given location is the result of thechanging positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the localbathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is animportant ecological product of ocean tides.

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Effects on life

An oasis is an isolated water source withvegetation in desert

Overview of photosynthesis and respiration.Water (at right), together with carbon dioxide

(CO2), form oxygen and organic compounds (atleft), which can be respired to water and (CO2).

From a biological standpoint, water has many distinct properties thatare critical for the proliferation of life that set it apart from othersubstances. It carries out this role by allowing organic compounds toreact in ways that ultimately allow replication. All known forms of lifedepend on water. Water is vital both as a solvent in which many of thebody's solutes dissolve and as an essential part of many metabolicprocesses within the body. Metabolism is the sum total of anabolismand catabolism. In anabolism, water is removed from molecules(through energy requiring enzymatic chemical reactions) in order togrow larger molecules (e.g. starches, triglycerides and proteins forstorage of fuels and information). In catabolism, water is used to breakbonds in order to generate smaller molecules (e.g. glucose, fatty acidsand amino acids to be used for fuels for energy use or other purposes).Without water, these particular metabolic processes could not exist.

Water is fundamental to photosynthesis and respiration. Photosyntheticcells use the sun's energy to split off water's hydrogen from oxygen.Hydrogen is combined with CO2 (absorbed from air or water) to formglucose and release oxygen. All living cells use such fuels and oxidizethe hydrogen and carbon to capture the sun's energy and reform waterand CO2 in the process (cellular respiration).

Water is also central to acid-base neutrality and enzyme function. Anacid, a hydrogen ion (H+, that is, a proton) donor, can be neutralized bya base, a proton acceptor such as hydroxide ion (OH−) to form water.Water is considered to be neutral, with a pH (the negative log of thehydrogen ion concentration) of 7. Acids have pH values less than 7while bases have values greater than 7.

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Some of the biodiversity of a coral reef

Aquatic life forms

Some marine diatoms – a key phytoplanktongroup

Earth's surface waters are filled with life. The earliest life formsappeared in water; nearly all fish live exclusively in water, and thereare many types of marine mammals, such as dolphins and whales.Some kinds of animals, such as amphibians, spend portions of theirlives in water and portions on land. Plants such as kelp and algae growin the water and are the basis for some underwater ecosystems.Plankton is generally the foundation of the ocean food chain.

Aquatic vertebrates must obtain oxygen to survive, and they do so invarious ways. Fish have gills instead of lungs, although some speciesof fish, such as the lungfish, have both. Marine mammals, such as

dolphins, whales, otters, and seals need to surface periodically to breathe air. Some amphibians are able to absorboxygen through their skin. Invertebrates exhibit a wide range of modifications to survive in poorly oxygenatedwaters including breathing tubes (see insect and mollusc siphons) and gills (Carcinus). However as invertebrate lifeevolved in an aquatic habitat most have little or no specialisation for respiration in water.

Effects on human civilization

Water fountain

Civilization has historically flourished around rivers and majorwaterways; Mesopotamia, the so-called cradle of civilization, wassituated between the major rivers Tigris and Euphrates; the ancientsociety of the Egyptians depended entirely upon the Nile. Largemetropolises like Rotterdam, London, Montreal, Paris, New York City,Buenos Aires, Shanghai, Tokyo, Chicago, and Hong Kong owe theirsuccess in part to their easy accessibility via water and the resultantexpansion of trade. Islands with safe water ports, like Singapore, haveflourished for the same reason. In places such as North Africa and the

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Middle East, where water is more scarce, access to clean drinking water was and is a major factor in humandevelopment.

Health and pollution

Environmental Science Program, Iowa StateUniversity student sampling water.

Water fit for human consumption is called drinking water or potablewater. Water that is not potable may be made potable by filtration ordistillation, or by a range of other methods.

Water that is not fit for drinking but is not harmful for humans whenused for swimming or bathing is called by various names other thanpotable or drinking water, and is sometimes called safe water, or "safefor bathing". Chlorine is a skin and mucous membrane irritant that isused to make water safe for bathing or drinking. Its use is highlytechnical and is usually monitored by government regulations(typically 1 part per million (ppm) for drinking water, and 1–2 ppm ofchlorine not yet reacted with impurities for bathing water). Water for

bathing may be maintained in satisfactory microbiological condition using chemical disinfectants such as chlorine orozone or by the use of ultraviolet light.

In the USA, non-potable forms of wastewater generated by humans may be referred to as greywater, which istreatable and thus easily able to be made potable again, and blackwater, which generally contains sewage and otherforms of waste which require further treatment in order to be made reusable. Greywater composes 50-80% ofresidential wastewater generated by a household's sanitation equipment (sinks, showers and kitchen runoff, but nottoilets, which generate blackwater.) These terms may have different meanings in other countries and cultures.This natural resource is becoming scarcer in certain places, and its availability is a major social and economicconcern. Currently, about a billion people around the world routinely drink unhealthy water. Most countries acceptedthe goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitationduring the 2003 G8 Evian summit.[27] Even if this difficult goal is met, it will still leave more than an estimated halfa billion people without access to safe drinking water and over a billion without access to adequate sanitation. Poorwater quality and bad sanitation are deadly; some five million deaths a year are caused by polluted drinking water.The World Health Organization estimates that safe water could prevent 1.4 million child deaths from diarrhea eachyear.[28] Water, however, is not a finite resource, but rather re-circulated as potable water in precipitation inquantities many degrees of magnitude higher than human consumption. Therefore, it is the relatively small quantityof water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers aroundevery 1 to 10 years), that is a non-renewable resource, and it is, rather, the distribution of potable and irrigation waterwhich is scarce, rather than the actual amount of it that exists on the earth. Water-poor countries use importation ofgoods as the primary method of importing water (to leave enough for local human consumption), since themanufacturing process uses around 10 to 100 times products' masses in water.In the developing world, 90% of all wastewater still goes untreated into local rivers and streams.[29] Some 50countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 ofthese extract more water annually than is recharged through their natural water cycles.[30] The strain not only affectssurface freshwater bodies like rivers and lakes, but it also degrades groundwater resources.

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Human uses

Agriculture

Irrigation of field crops

The most important use of water in agriculture is for irrigation, whichis a key component to produce enough food. Irrigation takes up to 90%of water withdrawn in some developing countries[31] and significantproportions in more economically developed countries (United States,30% of freshwater usage is for irrigation).[32]

Water as a scientific standard

On 7 April 1795, the gram was defined in France to be equal to "theabsolute weight of a volume of pure water equal to a cube of onehundredth of a meter, and to the temperature of the melting ice."[33]

For practical purposes though, a metallic reference standard was required, one thousand times more massive, thekilogram. Work was therefore commissioned to determine precisely the mass of one liter of water. In spite of the factthat the decreed definition of the gram specified water at 0 °C—a highly reproducible temperature—the scientistschose to redefine the standard and to perform their measurements at the temperature of highest water density, whichwas measured at the time as 4 °C (39 °F).[34]

The Kelvin temperature scale of the SI system is based on the triple point of water, defined as exactly 273.16 K or0.01 °C. The scale is a more accurate development of 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 the isotopes hydrogen-1 and oxygen-16, but there is also small quantity of heavierisotopes such as hydrogen-2 (deuterium). The amount of deuterium oxides or heavy water is very small, but it stillaffects the properties of water. Water from rivers and lakes tends to contain less deuterium than seawater. Therefore,standard water is defined in the Vienna Standard Mean Ocean Water specification.

For drinking

A young girl drinking bottled water

The human body is anywhere from 55% to 78% water depending onbody size.[35] To function properly, the body requires between one andseven liters of water per day to avoid dehydration; the precise amountdepends on the level of activity, temperature, humidity, and otherfactors. Most of this is ingested through foods or beverages other thandrinking straight water. It is not clear how much water intake is neededby healthy people, though most advocates agree that 6–7 glasses ofwater (approximately 2 liters) daily is the minimum to maintain properhydration.[36] Medical literature favors a lower consumption, typically1 liter of water for an average male, excluding extra requirements dueto fluid loss from exercise or warm weather.[37] For those who have

healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and whileexercising) it is dangerous to drink too little. People can drink far more water than necessary while exercising,however, putting them at risk of water intoxication (hyperhydration), which can be fatal. The popular claim that "aperson should consume eight glasses of water per day" seems to

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Water quality: fraction of population usingimproved water sources by country

have no real basis in science.[38] Similar misconceptions concerningthe effect of water on weight loss and constipation have also beendispelled.[39]

Hazard symbol for Not drinking water

An original recommendation for water intake in 1945 by the Food andNutrition Board of the National Research Council read: "An ordinarystandard for diverse persons is 1 milliliter for each calorie of food.Most of this quantity is contained in prepared foods."[40] The latestdietary reference intake report by the United States National ResearchCouncil in general recommended (including food sources): 2.7 liters ofwater total for women and 3.7 liters for men.[41] Specifically, pregnantand breastfeeding women need additional fluids to stay hydrated.According to the Institute of Medicine—who recommend that, onaverage, women consume 2.2 liters and men 3.0 liters—this isrecommended to be 2.4 liters (10 cups) for pregnant women and 3liters (12 cups) for breastfeeding women since an especially largeamount of fluid is lost during nursing.[42] Also noted is that normally,about 20% of water intake comes from food, while the rest comes from drinking water and beverages (caffeinatedincluded). Water is excreted from the body in multiple forms; through urine and faeces, through sweating, and byexhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and dailyfluid needs may increase as well.

Humans require water that does not contain too many impurities. Common impurities include metal salts and oxides(including copper, iron, calcium and lead)[43] and/or harmful bacteria, such as Vibrio. Some solutes are acceptableand even desirable for taste enhancement and to provide needed electrolytes.[44]

The single largest (by volume) freshwater resource suitable for drinking is Lake Baikal in Siberia.[45]

Washing

The propensity of water to form solutions and emulsions is useful in various washing processes. Many industrialprocesses rely on reactions using chemicals dissolved in water, suspension of solids in water slurries or using waterto dissolve and extract substances. Washing is also an important component of several aspects of personal bodyhygiene.

Chemical uses

Water is widely used in chemical reactions as a solvent or reactant and less commonly as a solute or catalyst. Ininorganic reactions, water is a common solvent, dissolving many ionic compounds. In organic reactions, it is notusually 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 reactionsby water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercriticalwater combusts organic pollutants efficiently.

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As a heat transfer fluid

Ice used for cooling.

Water and steam are used as heat transfer fluids in diverse heatexchange systems, due to its availability and high heat capacity, bothas a coolant and for heating. Cool water may even be naturallyavailable from a lake or the sea. Condensing steam is a particularlyefficient heating fluid because of the large heat of vaporization. Adisadvantage is that water and steam are somewhat corrosive. In almostall electric power stations, water is the coolant, which vaporizes anddrives steam turbines to drive generators. In the U.S., cooling powerplants is the largest use of water.[32]

In the nuclear power industry, water can also be used as a neutronmoderator. In most nuclear reactors, water is both a coolant and amoderator. This provides something of a passive safety measure, asremoving the water from the reactor also slows the nuclear reactiondown - however other methods are favored for stopping a reaction andit is preferred to keep the nuclear core covered with water so as toensure adequate cooling.

Extinguishing fires

Water is used for fighting wildfires.

Water has a high heat of vaporization and is relatively inert, whichmakes it a good fire extinguishing fluid. The evaporation of watercarries heat away from the fire. However, only distilled water can beused to fight fires of electric equipment, because impure water iselectrically conductive. Water is not suitable for use on fires of oils andorganic solvents, because they float on water and the explosive boilingof water tends to spread the burning liquid.

Use of water in fire fighting should also take into account the hazardsof a steam explosion, which may occur when water is used on very hotfires in confined spaces, and of a hydrogen explosion, when substanceswhich react with water, such as certain metals or hot graphite, decompose the water, producing hydrogen gas.

The power of such explosions was seen in the Chernobyl disaster, although the water involved did not come fromfire-fighting at that time but the reactor's own water cooling system. A steam explosion occurred when the extremeover-heating of the core caused water to flash into steam. A hydrogen explosion may have occurred as a result ofreaction between steam and hot zirconium.

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Recreation

Grand Anse Beach, St. George's, Grenada, WestIndies, often reported as one of the top 10

beaches in the world.

Humans use water for many recreational purposes, as well as forexercising and for sports. Some of these include swimming,waterskiing, boating, surfing and diving. In addition, some sports, likeice hockey and ice skating, are played on ice. Lakesides, beaches andwaterparks are popular places for people to go to relax and enjoyrecreation. Many find the sound and appearance of flowing water to becalming, and fountains and other water features are populardecorations. Some keep fish and other life in aquariums or ponds forshow, fun, and companionship. Humans also use water for snow sportsi.e. skiing, sledding, snowmobiling or snowboarding, which requiresthe water to be frozen. People may also use water for play fightingsuch as with snowballs, water guns or water balloons.

Water industry

A water-carrier in India, 1882. In many placeswhere running water was not available, water had

to be transported by people.

A manual water pump in China

The water industry provides drinking water and wastewater services(including sewage treatment) to households and industry. Water supplyfacilities include water wells cisterns for rainwater harvesting, watersupply network, water purification facilities, water tanks, water towers,water pipes including old aqueducts. Atmospheric water generators arein development.

Drinking water is often collected at springs, extracted from artificialborings (wells) in the ground, or pumped from lakes and rivers.Building more wells in adequate places is thus a possible way toproduce more water, assuming the aquifers can supply an adequateflow. Other water sources include rainwater collection. Water mayrequire purification for human consumption. This may involve removalof undissolved substances, dissolved substances and harmful microbes.Popular methods are filtering with sand which only removesundissolved material, while chlorination and boiling kill harmfulmicrobes. Distillation does all three functions. More advancedtechniques exist, such as reverse osmosis. Desalination of abundantseawater is a more expensive solution used in coastal arid climates.

The distribution of drinking water is done through municipal watersystems, tanker delivery or as bottled water. Governments in manycountries have programs to distribute water to the needy at no charge.Others argue that the market mechanism and free enterprise are best tomanage this rare resource and to finance the boring of wells or theconstruction of dams and reservoirs.

Reducing usage by using drinking (potable) water only for humanconsumption is another option. In some cities such as Hong Kong, seawater is extensively used for flushing toilets citywide in order toconserve fresh water resources.

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Water purification facility

Polluting water may be the biggest single misuse of water; to the extentthat a pollutant limits other uses of the water, it becomes a waste of theresource, regardless of benefits to the polluter. Like other types ofpollution, this does not enter standard accounting of market costs,being conceived as externalities for which the market cannot account.Thus other people pay the price of water pollution, while the privatefirms' profits are not redistributed to the local population victim of thispollution. Pharmaceuticals consumed by humans often end up in thewaterways and can have detrimental effects on aquatic life if theybioaccumulate and if they are not biodegradable.

Wastewater facilities are storm sewers and wastewater treatment plants. Another way to remove pollution fromsurface runoff water is bioswale.

Industrial applications

Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric powercomes 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 sun. Heat from the sun evaporates water, which condenses asrain in higher altitudes, from where it flows down.

Three Gorges Dam is the largest hydro-electric power station.Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used forprecise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in thecooling of machinery to prevent over-heating, or prevent saw blades from over-heating.Water is also used in many industrial processes and machines, such as the steam turbine and heat exchanger, inaddition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollutionincludes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requirespure water for many applications and utilizes a variety of purification techniques both in water supply and discharge.

Water 16

Food processing

Water can be used to cook foods such as noodles.

Water plays many critical roles within the field of food science. It isimportant for a food scientist to understand the roles that water playswithin food processing to ensure the success of their products.

Solutes such as salts and sugars found in water affect the physicalproperties of water. The boiling and freezing points of water areaffected by solutes, as well as air pressure, which is in turn affected byaltitude. Water boils at lower temperatures with the lower air pressurewhich occurs at higher elevations. One mole of sucrose (sugar) perkilogram of water raises the boiling point of water by 0.51 °C, and onemole of salt per kg raises the boiling point by 1.02 °C; similarly,increasing the number of dissolved particles lowers water's freezing

point.[46] Solutes in water also affect water activity which affects many chemical reactions and the growth ofmicrobes in food.[47] Water activity can be described as a ratio of the vapor pressure of water in a solution to thevapor pressure of pure water.[46] Solutes in water lower water activity. This is important to know because mostbacterial growth ceases at low levels of water activity.[47] Not only does microbial growth affect the safety of foodbut also the preservation and shelf life of food.

Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as wellas playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonatesalt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grainof hardness.[46] Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard ifit contains 11 to 20 grains. [46] The hardness of water may be altered or treated by using a chemical ion exchangesystem. The hardness of water also affects its pH balance which plays a critical role in food processing. For example,hard water prevents successful production of clear beverages. Water hardness also affects sanitation; with increasinghardness, there is a loss of effectiveness for its use as a sanitizer.[46]

Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or itsgaseous state, steam. Water is also used for dishwashing.

Water 17

Water law, water politics and water crisis

An estimate of the share of people in developing countries with access to potablewater 1970–2000

Water politics is politics affected by waterand water resources. For this reason,water is a strategic resource in the globeand an important element in manypolitical conflicts. It causes health impactsand damage to biodiversity.

1.6 billion people have gained access to asafe water source since 1990.[48] Theproportion of people in developingcountries with access to safe water iscalculated to have improved from 30% in1970[4] to 71% in 1990, 79% in 2000 and84% in 2004. This trend is projected tocontinue.[5] To halve, by 2015, theproportion of people without sustainableaccess to safe drinking water is one of theMillennium Development Goals. Thisgoal is projected to be reached.

A 2006 United Nations report stated that "there is enough water for everyone", but that access to it is hampered bymismanagement and corruption.[49] In addition, global initiatives to improve the efficiency of aid delivery, such asthe Paris Declaration on Aid Effectiveness, have not been taken up by water sector donors as effectively as they havein education and health, potentially leaving multiple donors working on overlapping projects and recipientgovernments without empowerment to act.[50]

The UN World Water Development Report (WWDR, 2003) from the World Water Assessment Program indicatesthat, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of theworld's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in2000 from waterborne diseases (related to the consumption of contaminated water) or drought. In 2004, the UKcharity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; oftenthis means lack of sewage disposal; see toilet.Organizations concerned with water protection include International Water Association (IWA), WaterAid, Water 1st,American Water Resources Association [51]. Water related conventions are United Nations Convention to CombatDesertification (UNCCD), International Convention for the Prevention of Pollution from Ships, United NationsConvention on the Law of the Sea and Ramsar Convention. World Day for Water takes place on 22 March andWorld Ocean Day on 8 June.Water used in the production of a good or service is virtual water.

Water in culture

ReligionWater is considered a purifier in most religions. Major faiths that incorporate ritual washing (ablution) include Christianity, Islam, Hinduism, Rastafari movement, Shinto, Taoism, Judaism, and Wicca. Immersion (or aspersion or affusion) of a person in water is a central sacrament of Christianity (where it is called baptism); it is also a part of the practice of other religions, including Judaism (mikvah) and Sikhism (Amrit Sanskar). In addition, a ritual bath in pure water is performed for the dead in many religions including Judaism and Islam. In Islam, the five daily prayers

Water 18

can be done in most cases (see Tayammum) after completing washing certain parts of the body using clean water(wudu). In Shinto, water is used in almost all rituals to cleanse a person or an area (e.g., in the ritual of misogi).Water is mentioned numerous times in the Bible, for example: "The earth was formed out of water and by water"(NIV). In the Qur'an it is stated that "Living things are made of water" and it is often used to described Paradise.

PhilosophyThe Ancient Greek philosopher Empedocles held that water is one of the four classical elements along with fire,earth and air, and was regarded as the ylem, or basic substance of the universe. Water was considered cold and moist.In the theory of the four bodily humors, water was associated with phlegm. The classical element of Water was alsoone of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal.Water is also taken as a role model in some parts of traditional and popular Asian philosophy. James Legge's 1891translation of the Dao De Jing states "The highest excellence is like (that of) water. The excellence of water appearsin its benefiting all things, and in its occupying, without striving (to the contrary), the low place which all mendislike. Hence (its way) is near to (that of) the Tao" and "There is nothing in the world more soft and weak thanwater, and yet for attacking things that are firm and strong there is nothing that can take precedence of it—for thereis nothing (so effectual) for which it can be changed."[52]

LiteratureWater is used in literature as a symbol of purification. Examples include the critical importance of a river in As I LayDying by William Faulkner and the drowning of Ophelia in Hamlet.Sherlock Holmes held that "From a drop of water, a logician could infer the possibility of an Atlantic or a Niagarawithout having seen or heard of one or the other."[53]

See also• The water (data page) is a collection of the chemical and physical properties of water.Water is described in many terms and contexts:• according to state

• solid – ice• liquid – water• gaseous – water vapor• plasma

• according to meteorology:• hydrometeor

• precipitation

precipitation according to movement precipitation according to state

Water 19

• vertical (falling) precipitation

• rain• freezing rain• drizzle• freezing drizzle• snow• snow pellets• snow grains• ice pellets• frozen rain• hail• ice crystals

• horizontal (seated) precipitation

• dew• hoarfrost• atmospheric icing• glaze ice

• liquid precipitation

• rain• freezing rain• drizzle• freezing drizzle• dew

• solid precipitation

• snow• snow pellets• snow grains• ice pellets• frozen rain• hail• ice crystals• hoarfrost• atmospheric icing• glaze ice

• mixed precipitation

• in temperatures around 0 °C

• levitating particles• clouds• fog• mist

• ascending particles (drifted by wind)• spindrift• stirred snow

• according to occurrence

• groundwater• meltwater• meteoric water• connate water• fresh water• surface water• mineral water – contains many minerals• brackish water• dead water – strange phenomenon which can occur when a layer of fresh or brackish water rests on top of

denser salt water, without the two layers mixing. It is dangerous for ship traveling.• seawater• brine

• according to uses

• tap water• bottled water• drinking water or potable water – useful for everyday drinking, without fouling, it contains balanced minerals

that are not harmful to health (see below)• purified water, laboratory-grade, analytical-grade or reagent-grade water – water which has been highly

purified for specific uses in science or engineering. Often broadly classified as Type I, Type II, or Type III, thiscategory of water includes, but is not limited to, the following:• distilled water

Water 20

• double distilled water• deionized water• Reverse osmosis plant Water

• according to other features

• soft water – contains fewer minerals• hard water – from underground, contains more minerals• distilled water, double distilled water, deionized water – contains no minerals• water of crystallization — water incorporated into crystalline structures• hydrates — water bound into other chemical substances• heavy water – made from heavy atoms of hydrogen – deuterium. It is in nature in normal water in very low

concentration. It was used in construction of first nuclear reactors.• tritiated water

• according to microbiology

• drinking water• wastewater• stormwater or surface water

• according to religion

• holy water

Other topics• Dihydrogen monoxide hoax• Water Pasteurization Indicator• Water intoxication• Water pinch analysis

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Water 21

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[17] Water Found on Distant Planet (http:/ / www. time. com/ time/ health/ article/ 0,8599,1642811,00. html) July 12, 2007 By Laura Blue, Time[18] Water Found in Extrasolar Planet's Atmosphere (http:/ / www. space. com/ scienceastronomy/ 070410_water_exoplanet. html) – Space.com[19] Sparrow, Giles (2006). The Solar System. Thunder Bay Press. ISBN 1592235794.[20] Weird water lurking inside giant planets (http:/ / www. newscientist. com/ article/ mg20727764.

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harvard. edu/ news/ 2009/ pr200924. html). Harvard-Smithsonian Center for Astrophysics. . Retrieved 2010-03-28.[27] "G8 "Action plan" decided upon at the 2003 Evian summit" (http:/ / www. g8. fr/ evian/ english/ navigation/ 2003_g8_summit/

summit_documents/ water_-_a_g8_action_plan. html). G8.fr. 2003-06-02. . Retrieved 2010-07-25.[28] "World Health Organization. Safe Water and Global Health" (http:/ / www. who. int/ features/ qa/ 70/ en/ ). Who.int. 2008-06-25. .

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html) Jeffrey Utz, M.D., The MadSci Network[36] "Healthy Water Living" (http:/ / www. bbc. co. uk/ health/ healthy_living/ nutrition/ drinks_water. shtml). BBC. . Retrieved 2007-02-01.[37] Rhoades RA, Tanner GA (2003). Medical Physiology (2nd ed.). Baltimore: Lippincott Williams & Wilkins. ISBN 0781719364.

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Nutrition Board[42] "Water: How much should you drink every day? –" (http:/ / www. mayoclinic. com/ health/ water/ NU00283). Mayoclinic.com. . Retrieved

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Human Biology and Health. Englewood Cliffs, New Jersey, USA: Prentice Hall. ISBN 0-13-981176-1. OCLC 32308337.[45] Unesco (2006). Water: a shared responsibility (http:/ / books. google. com/ ?id=1cV8tziHZ5sC& pg=PA125). Berghahn Books. p. 125.

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[47] DeMan, John M (1999). Principles of Food Chemistry (http:/ / books. google. com/ ?id=kDYJ7a1HbD0C& pg=PA434). Springer.ISBN 083421234X. .

[48] The Millennium Development Goals Report (http:/ / mdgs. un. org/ unsd/ mdg/ Resources/ Static/ Products/ Progress2008/MDG_Report_2008_En. pdf#page=44), United Nations, 2008

[49] UNESCO, (2006), Water, a shared responsibility. The United Nations World Water Development Report 2 (http:/ / unesdoc. unesco. org/images/ 0014/ 001444/ 144409E. pdf).

[50] Katharina Welle, Barbara Evans, Josephine Tucker and Alan Nicol (2008) Is water lagging behind on Aid Effectiveness? (http:/ / www. odi.org. uk/ resources/ download/ 1894. pdf)

[51] http:/ / www. awra. org/[52] "Internet Sacred Text Archive Home" (http:/ / www. sacred-texts. com/ tao/ taote. htm). Sacred-texts.com. . Retrieved 2010-07-25.[53] Arthur Conan Doyle, A Study in Scarlet, Chapter 2, "The Science of Deduction"

Further reading• OA Jones, JN Lester and N Voulvoulis, Pharmaceuticals: a threat to drinking water? TRENDS in Biotechnology

23(4): 163, 2005• Franks, F (Ed), Water, A comprehensive treatise, Plenum Press, New York, 1972–1982• PH Gleick and associates, The World's Water: The Biennial Report on Freshwater Resources. Island Press,

Washington, D.C. (published every two years, beginning in 1998.)• Marks, William E., The Holy Order of Water: Healing Earth's Waters and Ourselves. Bell Pond Books ( a div. of

Steiner Books), Great Barrington, MA, November 2001 [ISBN 0-88010-483-X]• Debenedetti, P. G., and Stanley, H. E.; "Supercooled and Glassy Water", Physics Today 56 (6), p. 40–46 (2003).

Downloadable PDF (1.9 MB) (http:/ / polymer. bu. edu/ hes/ articles/ ds03. pdf)

Water as a natural resource• Anderson (1991). Water Rights: Scarce Resource Allocation, Bureaucracy, and the Environment.

ISBN 0884103900.• Maude Barlow, Tony Clarke (2003). Blue Gold: The Fight to Stop the Corporate Theft of the World's Water.

ISBN 1565848136.• Gleick, Peter H.. The World's Water: The Biennial Report on Freshwater Resources. Washington: Island Press.

ISBN 1559637927.• Miriam R. Lowi (1995). Water and Power: The Politics of a Scarce Resource in the Jordan River Basin.

ISBN 0521431646. (Cambridge Middle East Library)• William E. Marks (2001). The Holy Order of Water: Healing Earths Waters and Ourselves.• Postel, Sandra (1997, second edition). Last Oasis: Facing Water Scarcity. New York: Norton Press.

ISBN 0393034283.• Reisner, Marc (1993). Cadillac Desert: The American West and Its Disappearing Water. ISBN 0670199273.• Vandana Shiva (2002). Water Wars: Privatization, Pollution, and Profit. London: Pluto Press [u.a.].

ISBN 0-7453-1837-1. OCLC 231955339.• Anita Roddick, et al (2004). Troubled Water: Saints, Sinners, Truth And Lies About The Global Water Crisis.

ISBN 095439593X.• Marq de Villiers (2003, revised edition). Water: The Fate of Our Most Precious Resource. ISBN 0618030093.• Diane Raines Ward (2002). Water Wars: Drought, Flood, Folly and the Politics of Thirst. ISBN 1573222291.• Worster, Donald (1992). Rivers of Empire: Water, Aridity, and the Growth of the American West.

ISBN 039451680X.

Water 23

External links• OECD Water statistics (http:/ / stats. oecd. org/ wbos/ Index. aspx?DataSetCode=ENV_WAT)bjn:Banyu

Article Sources and Contributors 24

Article Sources and ContributorsWater  Source: http://en.wikipedia.org/w/index.php?oldid=395081181  Contributors: -Majestic-, 11nniuq, 1qaz!QAZ, 334a, 5 albert square, A Softer Answer, A.b.s, A8UDI, ABlake, AEMoreira042281, ALIENDUDE5300, AWeishaupt, Abarton777, Abdullais4u, Absolwent, Acalamari, Acatkiller, Acceptable, Aceofhearts157, Achristl, Acroterion, Acs4b, Acspsg, Adambiswanger1, Adampantha, Adashiel, AdjustShift, Adsomvilay, Afluent Rider, Ahoerstemeier, Ahruman, Aillema, Airplanedude550, Aksi great, Al Adriance, Alan Liefting, Alansohn, Alegoo92, Alesnormales, Alex earlier account, AlexiusHoratius, Alexultima, Alhutch, Alight, Alison, Alistair b, Alloquep, AmandaFraser, AmiDaniel, Amiruka, Amkozmo10, Anastrophe, Andonic, Andre Engels, Andrewjlockley, Andrewpmk, Android79, Andy M. 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Image Sources, Licenses and ContributorsImage:Iceberg with hole near sanderson hope 2007-07-28 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Iceberg_with_hole_near_sanderson_hope_2007-07-28_2.jpg  License:GNU Free Documentation License  Contributors: User:SlaungerImage:3D model hydrogen bonds in water.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:3D_model_hydrogen_bonds_in_water.jpg  License: GNU Free Documentation License Contributors: User:snek01Image:Water droplet blue bg05.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Water_droplet_blue_bg05.jpg  License: unknown  Contributors: Fir0002Image:SnowflakesWilsonBentley.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:SnowflakesWilsonBentley.jpg  License: Public Domain  Contributors: Wilson BentleyImage:Spider web Luc Viatour.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Spider_web_Luc_Viatour.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors:user:LviatourImage:Capillarity.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Capillarity.svg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: user:MesserWolandImage:Label for dangerous goods - class 4.3.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Label_for_dangerous_goods_-_class_4.3.svg  License: Public Domain  Contributors:w:User:MysidMysidImage:Habitable zone-en.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Habitable_zone-en.svg  License: GNU Free Documentation License  Contributors: User:ChewieFile:Earth's water distribution.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Earth's_water_distribution.svg  License: Public Domain  Contributors: USGSImage:The Earth seen from Apollo 17.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:The_Earth_seen_from_Apollo_17.jpg  License: Public Domain  Contributors: NASA. Phototaken by either Harrison Schmitt or Ron Evans (of the Apollo 17 crew).Image:Water cycle.png  Source: http://en.wikipedia.org/w/index.php?title=File:Water_cycle.png  License: unknown  Contributors: AdiJapan, Helt, Juliancolton, Lupo, MARKELLOS, Marcbel,Masao jp, Saperaud, Seb az86556, Slady, 9 ,לורק לארשי anonymous editsImage:Bay of Fundy High Tide.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Bay_of_Fundy_High_Tide.jpg  License: GNU Free Documentation License  Contributors: Antaya,Ed Fitzgerald, GeorgHH, Sam, Sanao, ShizhaoImage:Bay of Fundy Low Tide.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Bay_of_Fundy_Low_Tide.jpg  License: GNU Free Documentation License  Contributors: Antaya, EdFitzgerald, GeorgHH, Sam, Sanao, Shizhao, SpiritiaImage:Oasis in Lybia.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Oasis_in_Lybia.JPG  License: Public Domain  Contributors: User:SfivatFile:Auto-and heterotrophs.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Auto-and_heterotrophs.svg  License: GNU Free Documentation License  Contributors: User:MikaelHäggströmImage:Blue Linckia Starfish.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Blue_Linckia_Starfish.JPG  License: Creative Commons Attribution-Sharealike 2.5  Contributors:User:RlingImage:Diatoms through the microscope.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Diatoms_through_the_microscope.jpg  License: Public Domain  Contributors: Prof. GordonT. Taylor, Stony Brook UniversityImage:Longwood Gardens-Italian Garden.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Longwood_Gardens-Italian_Garden.jpg  License: Creative CommonsAttribution-Sharealike 3.0  Contributors: Original uploader was MikeParker at en.wikipediaImage:Field Trip- water sampling.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Field_Trip-_water_sampling.jpg  License: Creative Commons Attribution 3.0  Contributors:Original uploader was Alloquep at en.wikipediaImage:SiphonTubes.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:SiphonTubes.JPG  License: Public Domain  Contributors: H2O-C, Honeplus, 1 anonymous editsImage:Humanitarian aid OCPA-2005-10-28-090517a.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Humanitarian_aid_OCPA-2005-10-28-090517a.jpg  License: unknown Contributors: Technical Sergeant Mike Buytas of the United States Air ForceImage:Water quality.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Water_quality.jpg  License: Creative Commons Attribution 3.0  Contributors: User:Ionut CojocaruImage:D-P005 Kein Trinkwasser.svg  Source: http://en.wikipedia.org/w/index.php?title=File:D-P005_Kein_Trinkwasser.svg  License: Public Domain  Contributors: User:DrTorstenHenningImage:Kookwekker1268.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Kookwekker1268.JPG  License: GNU Free Documentation License  Contributors: Original uploader wasAlgont at nl.wikipediaImage:MH-60S Helicopter dumps water onto Fire.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:MH-60S_Helicopter_dumps_water_onto_Fire.jpg  License: Public Domain Contributors: Mass Communication Specialist 2nd Class Chris Fahey, U.S. NavyFile:Grand_Anse_Beach_Grenada.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Grand_Anse_Beach_Grenada.jpg  License: Creative Commons Attribution 3.0  Contributors:VkapImage:Water carrier.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Water_carrier.jpg  License: unknown  Contributors: Alan Liefting, Idleguy, Magog the Ogre, SiddhantImage:TapWater-china.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:TapWater-china.JPG  License: GNU Free Documentation License  Contributors: User:ShizhaoImage:Usine Bret MG 1648.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Usine_Bret_MG_1648.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors:User:RamaFile:200407-sandouping-sanxiadaba-4.med.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:200407-sandouping-sanxiadaba-4.med.jpg  License: GNU Free Documentation License Contributors: Rehman, Saperaud, Shizhao, TomPreussFile:Magnify-clip.png  Source: http://en.wikipedia.org/w/index.php?title=File:Magnify-clip.png  License: GNU Free Documentation License  Contributors: User:Erasoft24Image:Cuisson des pates.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cuisson_des_pates.jpg  License: GNU Free Documentation License  Contributors: Antoinel, Catfisheye,Man vyiFile:Access to drinking water in third world.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Access_to_drinking_water_in_third_world.svg  License: Public Domain  Contributors:User:Ephemeronium

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