|right|thumb|280px|Impact from a water drop causes an upward "rebound" jet surrounded by circular capillary waves. jxdjdfgeto its liquid form or state, but the substance also has the solid suck my cock is a commonm term that they use todayair as vapor, clouds, and precipitation.Water Vapor in the Climate System, Special Report, [AGU], December 1995 (linked 4/2007). right|thumb|Water in three states: liquid water, solid water is ice and clouds are condensated water vapor. Water is a common chemical substance that is essential to all known forms of life.http://pubs.acs.org/cgi-bin/abstract.cgi/bichaw/1997/36/i43/abs/bi971323j.html
In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor. About 1,460 teratonnes (Tt) of water covers 71% of the Earth's surface, mostly in oceans and other large water bodies, with 1.6% of water below ground in aquifers and 0.001% in the air as vapor, clouds (formed of solid and liquid water particles suspended in air), and precipitation.Water Vapor in the Climate System, Special Report, [AGU], December 1995 (linked 4/2007). Vital Water UNEP. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%; and other land surface water such as rivers and lakes 0.025%. Water in these forms moves perpetually through the water cycle of evaporation and transpiration, precipitation, and runoff usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year to the precipitation of 107 Tt per year over land. Some water is trapped for periods in ice caps, glaciers, aquifers, or lakes for varying periods, sometimes providing fresh water for life on land. Clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply. Many very important chemical substances, such as salts, sugars, acids, alkalis, some gases (especially oxygen) and many organic molecules dissolve in water. Outside of our planet, a significant quantity is thought to exist underground on the planet Mars, on the moons Europa and Enceladus, and on the exoplanet known as HD 209458 b. Water Found in Extrasolar Planet's Atmosphere - Space.com
right|thumb|150px|Water covers 71% the Earth's surface; the oceans contain 97.2% of Earth's water. The Antarctic ice sheet, which contains 90% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the earth's albedo. Chemical and physical properties
<bigcock>Water</big> 135px|The dimensions and geometric structure of a water molecule110px|This space-filled model shows the molecular structure of water. Water is the base of human life, andan abundant compound on the earth's surface. Information and properties Systematic name water Alternative names aqua, dihydrogen monoxide, hydrogen hydroxide, (more) Molecular formula H2O Molar mass 18.0153 g/mol Density and phase 0.998 g/cm³ (liquid at 20 °C) 0.92 g/cm³ (solid) Melting point 0 °C (273.15 K) (32 °F) Boiling point 100 °C (373.15 K) (212 °F) Specific heat capacity 4.184 J/(g•K) (liquid at 20 °C) Supplementary data pageDisclaimer and references
Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. Water is a tasteless, odourless liquid at ambient temperature and pressure, and appears colourless in small quantities, although it has its own intrinsic very light blue hue. Ice also appears colourless, and water vapour is essentially invisible as a gas.Why is water blue? Water is primarily a liquid under standard conditions, which is not predicted from its relationship to other analogous hydrides of the oxygen family in the periodic table which are gases, such as hydrogen sulfide. Also the elements surrounding oxygen in the periodic table, nitrogen, fluorine, phosphorus, sulfur and chlorine, all combine with hydrogen to produce gases under standard conditions. The reason that oxygen hydride (water) forms a liquid is that it is more electronegative than all of these elements (other than fluorine). Oxygen attracts electrons much more strongly than hydrogen, resulting in a net positive charge on the hydrogen atoms, and a net negative charge on the oxygen atom. The presence of a charge on each of these atoms gives each water molecule a net dipole moment. Electrical attraction between water molecules due to this dipole pulls individual molecules closer together, making it more difficult to separate the molecules and therefore raising the boiling point. This attraction is known as hydrogen bonding. Water can be described as a polar liquid that dissociates disproportionately into the hydronium ion (H3O+(aq)) and an associated hydroxide ion (OH-(aq)). Water is in dynamic equilibrium between the liquid, gas and solid states at standard temperature and pressure, and is the only pure substance found naturally on Earth to be so. Cohesion and adhesion
Water has a partial negative charge (σ-) near the oxygen atom due to the unshared pairs of electrons, and partial positive charges (σ+) near the hydrogen atoms. In water, this happens because the oxygen atom is more electronegative than the hydrogen atoms — that is, it has a stronger "pulling power" on the molecule's electrons, drawing them closer (along with their negative charge) and making the area around the oxygen atom more negative than the area around both of the hydrogen atoms. Adhesion
thumb|right|Dew drops adhering to a spider web
Water sticks to itself (cohesion) because it is polar. Some of the Earth's water is contained within man-made and natural objects near the Earth's surface such as water towers, animal and plant bodies, manufactured products, and food stores. Saltwater oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers and lakes 0.6%. Water moves continually through a cycle of evaporation or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Winds carry water vapor over land at the same rate as runoff into the sea, about 36 Tt per year. Over land, evaporation and transpiration contribute another 71 Tt per year to the precipitation of 107 Tt per year over land. Some water is trapped for varying periods in ice caps, glaciers, aquifers, or in lakes, sometimes providing fresh water for life on land. Clean, fresh water is essential to human and other life. However, in many parts of the world - especially developing countries - it is in short supply. Water is a solvent for a wide variety of chemical substances. Overview of types of water
Water can appear in three phases. Water takes many different forms on Earth: water vapor and Clouds in the sky; seawater and rarely icebergs in the ocean; glaciers and rivers in the mountains; and aquifers in the ground. Water can dissolve many different substances, giving it different tastes and odors. In fact, humans and other animals have developed senses to be able to evaluate the potability of water: animals generally dislike the taste of salty sea water and the putrid swamps and favor the purer water of a mountain spring or aquifer. The taste advertised in spring water or mineral water derives from the minerals dissolved in it, as pure H2O is tasteless. As such, purity in spring and mineral water refers to purity from toxins, pollutants, and microbes. Because of the importance of precipitation to agriculture, and to mankind in general, different names are given to its various forms:
right|thumb|125px|Snowflakes by Wilson Bentley, 1902
according to phase
solid - ice
liquid - water, (supercooled water)
gaseous - water vapor
according to meteorology:
hydrometeor
precipitation
{| border=0|
|-
| ||precipitation according to moves|| ||precipitation according to phase
|-
|
|valign=top |
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
||
|valign=top |
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
BR (according to METAR)
ascending particles (drifted by wind)
spindrift
stirred snowaccording to occurence groundwater
meltwater
meteoric water
fresh water
mineral water – contains much minerals
brackish water
dead water – strange phenomenon which can occur when a layer of fresh or brackish water rests on top of more dense salt water, without the two layers mixing. It is dangerous for ship traveling. seawater
brineaccording to uses tap water
bottled water
safe water – Its use is highly technical, without minerals to not make limescale
drinking water or potable water – useful for everyday drinking, without fouling, it contains balanced minerals that are not harmful to health (see below)according to other features soft water – contains less minerals
hard water – from underground, contains more minerals
distilled water, double distilled water, deionized water - contains no minerals
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 wateraccording to microbiologydrinking water
wastewater
stormwater or surface wateraccording to religionholy water
Chemical and physical properties
Water 135px|The dimensions and geometric structure of a water molecule110px|This space-filled model shows the molecular structure of water. Water is the base of all life, andan abundant compound on the earth's surface. Information and properties Systematic name water Alternative names aqua, dihydrogen monoxide, hydrogen hydroxide, (more) Molecular formula H2O InChI InChI=1/H2O/h1H2 Molar mass 18.0153 g/mol Density and phase 0.998 g/cm³ (liquid at 20 °C) 0.92 g/cm³ (solid) Melting point 0 °C (273.15 K) (32 °F) Boiling point 100 °C (373.15 K) (212 °F) Specific heat capacity 4.184 J/(g·K) (liquid at 20 °C) Supplementary data pageDisclaimer and references
left|thumb|model of hydrogen bonds between molecules of water
left|thumb|Impact from a water drop causes an upward "rebound" jet surrounded by circular capillary waves. thumb|left|Dew drops adhering to a spider web
left|thumb|capillary action of water compared to mercury
Water is the chemical substance with chemical formula H2O: one molecule of water has two hydrogen atoms covalently bonded to a single oxygen atom. The major chemical and physical properties of water are:
Water is a tasteless, odorless liquid at ambient temperature and pressure. The color of water and ice are, intrinsically, a very light blue hue, although water appears colorless in small quantities. Ice also appears colorless, and water vapor is essentially invisible as a gas. Water is transparent, and thus aquatic plants can live within the water because sunlight can reach them. Only strong UV light is slightly adsorbed. Water is a liquid under standard conditions. Water consists of a polar molecule. Since oxygen has a higher electronegativity than hydrogen, the charge difference is called a dipole. The interactions between the different dipoles of each molecule cause a net attraction force. Another very important force that causes the water molecules to stick to one another is the hydrogen bond. The boiling point of water (and all other liquids) is directly related to the barometric pressure. For example, on the top of Mt. Everest water boils at about , compared to at sea level. Conversely, water deep in the ocean near geothermal vents can reach temperatures of hundreds of degrees and remain liquid. Water sticks to itself. Water has a high surface tension caused by the strong cohesion between water molecules because it is polar. The apparent elasticity caused by surface tension drives the capillary waves. Water also has high adhesion properties because of its polar nature. On extremely clean/smooth glass the water may form a thin film because the molecular forces between glass and water molecules (adhesive forces) are stronger than the cohesive forces. In biological cells and organelles, water is in contact with membrane and protein surfaces that are hydrophilic; that is, surfaces that have a strong attraction to water. Irving Langmuir observed a strong repulsive force between hydrophilic surfaces. To dehydrate hydrophilic surfaces — to remove the strongly held layers of water of hydration — requires doing substantial work against these forces, called hydration forces. These forces are very large but decrease rapidly over a nanometer or less. Their importance in biology has been extensively studied by V. Adrian Parsegian of the National Institute of Health. Physical Forces Organizing Biomolecules (PDF) They are particularly important when cells are dehydrated by exposure to dry atmospheres or to extracellular freezing. Surface tension
thumb|right|This daisy is under the water level, which has risen gently and smoothly. Surface tension prevents the water from submerging the flower. Water has a high surface tension caused by the strong cohesion between water molecules. This can be seen when small quantities of water are put onto a non-soluble surface such as polythene; the water stays together as drops. Just as significantly, air trapped in surface disturbances forms bubbles, which sometimes last long enough to transfer gas molecules to the water. Another surface tension effect is capillary waves which are the surface ripples that form from around the impact of drops on water surfaces, and some times occur with strong subsurface currents flow to the water surface. The apparent elasticity caused by surface tension drives the waves. Capillary action
Capillary action refers to the process of water moving up a narrow tube against the force of gravity. It occurs because water adheres to the sides of the tube, and then surface tension tends to straighten the surface making the surface rise, and more water is pulled up through cohesion. The process is repeated as the water flows up the tube until there is enough water that gravity can counteract the adhesive force. Solvation
thumb|200px|left|High concentrations of dissolved lime make the water of Havasu Falls appear turquoise. Capillary action refers to the tendency of water to move up a narrow tube against the force of gravity. Water is a very strong solvent, referred to as the universal solvent, dissolving many types of substances. Substances that will mix well and dissolve in water (e.g. salts) are known as "hydrophilic" (water-loving) substances, while those that do not mix well with water (e.g. Substances that will mix well and 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), are known as "hydrophobic" (water-fearing) substances. The ability of a substance to dissolve in water is determined by whether or not the substance can match or better the strong attractive forces that water molecules generate between other water molecules. If a substance has properties that do not allow it to overcome these strong intermolecular forces, the molecules are "pushed out" from amongst the water and do not dissolve. Electrical conductivity
Pure water has a low electrical conductivity, but this increases significantly upon solvation of a small amount of ionic material water such as hydrogen chloride. Thus the risks of electrocution are much greater in water with the usual impurities not found in pure water. Any electrical properties observable in water are from the ions of mineral salts and carbon dioxide dissolved in it. Water does self-ionize where two water molecules become one hydroxide anion and one hydronium cation, but not enough to carry enough electric current to do any work or harm for most operations. In pure water, sensitive equipment can detect a very slight electrical conductivity of 0.055 µS/cm at 25°C. Water can also be electrolyzed into oxygen and hydrogen gases but in the absence of dissolved ions this is a very slow process since very little current is conducted. Deuterated compounds of water
Hydrogen has 3 isotopes, the first being the most common, or having 1 proton and 0 neutrons. More than 95% of water consists of this regular water. There is a second isotope having 1 proton and 1 neutron, called deuterium (short form "D"). This is also known as heavy water and is used in nuclear reactors for storing nuclear wastes. The third isotope has 1 proton and 2 neutrons, called tritium. Tritium is radioactive, and therefore does not exist in nature as creation of the rare molecule would result in almost instantaneous decomposition. is stable; however, it is different from in that is heavier and denser, and it can block alpha and beta rays. occurs naturally in water in very low concentrations. Consumption of pure isolated may affect biochemical processes: ingestion of large amounts impairs kidney function and central nervous system operation. Water, ice, and vapor
Heat capacity and heat of vaporization
Water has the second highest specific heat capacity of any known chemical compound, after ammonia, as well as a high heat of vaporization (40.65 kJ mol-1), both of which are a result of the extensive hydrogen bonding between its molecules. All the major components in cells (proteins, DNA and polysaccharides) are also dissolved in water. Pure water has a low electrical conductivity, but this increases significantly upon solvation of a small amount of ionic material such as sodium chloride. Water has the second highest specific heat capacity of any known chemical compound, after ammonia, as well as a high heat of vaporization (40.65 kJ mol−1), both of which are a result of the extensive hydrogen bonding between its molecules. These two unusual properties allow water to moderate Earth's climate by buffering large fluctuations in temperature. Freezing point
A simple but environmentally important and unusual property of water is that its usual solid form, ice, floats on its liquid form. This solid state is not as dense as liquid water because of the geometry of the hydrogen bonds which are formed only at lower temperatures. For almost all other substances the solid form has a greater density than the liquid form. Fresh water at standard atmospheric pressure is most dense at 3.98 °C, and will sink by convection as it cools to that temperature, and if it becomes colder it will rise instead. This reversal will cause deep water to remain warmer than shallower freezing water, so that ice in a body of water will form first at the surface and progress downward, while the majority of the water underneath will hold a constant 4 °C. This effectively insulates a lake floor from the cold. The water will freeze at 0°C (32°F, 273 K), however, it can be supercooled in a fluid state down to its crystal homogeneous nucleation at almost 231 K (−42 °C). Ice also has a number of more exotic phases not commonly seen (go to the full article on Ice). Triple point
The triple point of water (the single combination of pressure and temperature at which pure liquid water, ice, and water vapor can coexist in a stable equilibrium) is used to define the kelvin, the SI unit of thermodynamic temperature. As a consequence, water's triple point temperature is an exact value rather than a measured quantity : 273.16 kelvins (0.01 °C) and a pressure of 611.73 pascals (approximately 0.0060373 atm). This is approximately the combination that exists with 100% relative humidity at sea level and the freezing point of water. Miscibility and condensation
Water is miscible with many liquids, for example ethanol in all proportions, forming a single homogeneous liquid. The maximum density of water is at . Water becomes even less dense upon freezing, expanding 9%. This causes an unusual phenomenon: ice floats upon water, and so water organisms can live inside a partly frozen pond because the water on the bottom has a temperature of around . Water is miscible with many liquids, for example ethanol, in all proportions, forming a single homogeneous liquid. On the other hand water and most oils are immiscible usually forming layers according to increasing density from the top. thumb|200px|right|Red line shows saturation
As a gas, water vapor is completely miscible with air. On the other hand the maximum water vapor pressure that is thermodynamically stable with the liquid (or solid) at a given temperature is relatively low compared with total atmospheric pressure. For example, if the vapor partial pressureThe pressure due to water vapor in the air is called the partial pressure(Dalton's law) and it is directly proportional to concentration of water molecules in air (Boyle's law). is 2% of atmospheric pressure and the air is cooled from 25 deg C, starting at about 22 C water will start to condense, defining the dew point, and creating fog or dew. The reverse process accounts for the fog burning off in the morning. If one raises the humidity at room temperature, say by running a hot shower or a bath, and the temperature stays about the same, the vapor soon reaches the pressure for phase change, and condenses out as steam. A gas in this context is referred to as saturated or 100% relative humidity, when the vapor pressure of water in the air is at the equilibrium with vapor pressure due to (liquid) water; water (or ice, if cool enough) will fail to lose mass through evaporation when exposed to saturated air. Because the amount of water vapor in air is small, relative humidity, the ratio of the partial pressure due to the water vapor to the saturated partial vapor pressure, is much more useful. Water vapor pressure above 100% relative humidity is called super-saturated and can occur if air is rapidly cooled, say by rising suddenly in an updraft. Adiabatic cooling resulting from the ideal gas law. Water on Earth
Origin and planetary effects
thumb|300px|right|The Solar System along center row range of possible habitable zones of varying size stars. Much of the universe's water may be produced as a byproduct of star formation. As a gas, water vapor is completely miscible with air. Water forms an azeotrope with many other solvents. right|thumb|ADR label for transporting goods dangerously reactive with water
Some substances (sodium, lithium, calcium, potassium) emit a flammable gas (hydrogen) when wet, or react violently with water. Distribution of water in nature
Water in the Universe
Much of the universe's water may be produced as a byproduct of star formation. When stars are born, their birth is accompanied by a strong outward wind of gas and dust. When this outflow of material eventually impacts the surrounding gas, the shock waves that are created compress and heat the gas. The water we observe is quickly produced in this warm dense gas. Gary Melnick, Harvard-Smithsonian Center for Astrophysics and David Neufeld, Johns Hopkins University quoted in:
. (linked 4/2007)
Solar distance and Earth gravity
The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth is vital to the existence of life on Earth. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or further from the Sun (about 5%, or 8 million kilometers or so), the conditions which allow the three forms to be present simultaneously would be far less likely to exist. <ref>J. The water observed is quickly produced in this warm dense gas.Gary Melnick, Harvard-Smithsonian Center for Astrophysics and David Neufeld, Johns Hopkins University quoted in:
(linked 4/2007)
Water has been detected in interstellar clouds within our galaxy, the Milky Way. It is believed that water exists in abundance in other galaxies too, because its components, hydrogen and oxygen, are among the most abundant elements in the universe. Interstellar clouds eventually condense into solar nebulae and solar systems, such as ours. Water vapor is on:
Mercury - 3.4% in the atmosphere
Venus - 0.002% in the atmosphere
Earth - trace in the atmosphere (varies with climate)
Mars - 0.03% in the atmosphere
Jupiter - 0.0004% in the atmosphere
Saturn - in ices only
Enceladus (moon of Saturn) - 91% in the atmosphere
exoplanets known as HD 189733 bWater Found on Distant Planet July 12, 2007 By Laura Blue, Time and HD 209458 b. Water Found in Extrasolar Planet's Atmosphere - Space.com
Liquid water is on:
Earth - 71% of surface
Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus. Probably some liquid water is on Europa. Water ice is on:
Earth - mainly on ice sheets
polar ice caps on Mars
Titan
Europa
Enceladus
Probability or possibility of distribution of water ice is at: lunar ice on the Moon, Ceres (dwarf planet), Tethys (moon). Ice is probably in internal structure of Uranus, Neptune, and Pluto and on comets. Water and habitable zone
thumb|450px|right|The Solar System along center row range of possible habitable zones of varying size stars. The existence of liquid water, and to a lesser extent its gaseous and solid forms, on Earth is vital to the existence of life on Earth as we know it. The Earth is located in the habitable zone of the solar system; if it were slightly closer to or further from the Sun (about 5%, or 8 million kilometers or so), the conditions which allow the three forms to be present simultaneously would be far less likely to exist.<ref>J. C. I. Dooge. "Integrated Management of Water Resources". in E. Ehlers, T. Krafft. (eds.) Understanding the Earth System: compartments, processes, and interactions. Springer, 2001, p. 116. More references are at the end of the article "Habitable Zone" at The Encyclopedia of Astrobiology, Astronomy and Spaceflight. </ref>
Earth's mass allows gravity to hold an atmosphere. Water vapor and carbon dioxide in the atmosphere provide a greenhouse effect which helps maintain a relatively steady surface temperature. If Earth were smaller, a thinner atmosphere would cause temperature extremes preventing the accumulation of water except in polar ice caps (as on Mars). It has been proposed that life itself may maintain the conditions that have allowed its continued existence. The surface temperature of Earth has been relatively constant through geologic time despite varying levels of incoming solar radiation (insolation), indicating that a dynamic process governs Earth's temperature via a combination of greenhouse gases and surface or atmospheric albedo. This proposal is known as the Gaia hypothesis. The state of water also depends on a planet's gravity. If a planet is sufficiently massive, the water on it may be solid even at high temperatures, because of the high pressure caused by gravity. Tides
Tides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides. Water cycle
right|thumb|250px|The movement of water around, over, and through the Earth is called the water cycle.The biosphere can be roughly divided into oceans, land, and atmosphere. There are various theories about origin of water on Earth. Water on Earth
right|thumb|Water covers 71% of the Earth's surface; the oceans contain 97.2% of the Earth's water. The Antarctic ice sheet, which contains 90% of all fresh water on Earth, is visible at the bottom. Condensed atmospheric water can be seen as clouds, contributing to the Earth's albedo. Hydrology is the study of the movement, distribution, and quality of water throughout the Earth. The study of the distribution of water is hydrography. The study of the distribution and movement of groundwater is hydrogeology, of glaciers is glaciology, of inland waters is limnology and distribution of oceans is oceanography. Ecological processes with hydrology are in focus of ecohydrology. The collective mass of water found on, under, and over the surface of a planet is called hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1 360 000 000 km³ (326 000 000 mi³). Of this volume:
1 320 000 000 km³ (316 900 000 mi³ or 97.2%) is in the oceans. 25 000 000 km³ (6 000 000 mi³ or 1.8%) is in glaciers, ice caps and ice sheets. 13 000 000 km³ (3,000,000 mi³ or 0.9%) is groundwater. 250 000 km³ (60,000 mi³ or 0.02%) is fresh water in lakes, inland seas, and rivers. 13 000 km³ (3,100 mi³ or 0.001%) is atmospheric water vapor at any given time. Groundwater and fresh water are useful or potentially useful to humans as 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 is sea water. Water is also present in the atmosphere in solid, liquid, and vapor phases. It also exists as groundwater in aquifers. The most important geological processes caused by water are: chemical weathering, water erosion, water sediment transport and sedimentation, mudflows, ice erosion and sedimentation by glacier. Water cycle
right|thumb|water cycle
The water cycle (known scientifically as the hydrologic cycle) refers to the continuous exchange of water within the hydrosphere, between the atmosphere, soil water, surface water, groundwater, and plants. Water moves perpetually through each of these regions in the water cycle consisting of following transfer processes:
evaporation from oceans and other water bodies into the air and transpiration from land plants and animals into air. precipitation, from water vapor condensing 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 as runoff 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, with some 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. Some of this is diverted to irrigation for agriculture. 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 the environment creating river valleys and deltas which provide rich soil and level ground for the establishment of population centers. Fresh water storage
Some runoff water is trapped for periods, for example in lakes. A flood occurs when an area of land, usually low-lying, is covered with water. It is when a river overflows its banks or flood from the sea. A drought is an extended period of months or years when a region notes a deficiency in its water supply. This occurs when a region receives consistently below average precipitation. Fresh water storage
Some runoff water is trapped for periods, for example in lakes. At high altitude, during winter, and in the far north and south, snow collects in ice caps, snow pack and glaciers. Water also infiltrates the ground and goes into aquifers. This groundwater later flows back to the surface in springs, or more spectacularly in hot springs and geysers. Groundwater is also extracted artificially in wells. This water storage is important, since clean, fresh water is essential to human and other land-based life. In many parts of the world, it is in short supply. left|thumb|125px|Snowflakes by Wilson Bentley, 1902
Forms of water
Water takes many different forms on Earth: water vapor and clouds in the sky; seawater and rarely icebergs in the ocean; glaciers and rivers in the mountains; and aquifers in the ground. Water can dissolve many different substances imparting upon it different tastes and odours. In fact, humans and other animals have developed senses to be able to evaluate the potability of water: animals generally dislike the taste of salty sea water and the putrid swamps and favor the purer water of a mountain spring or aquifer. The taste advertised in spring water or mineral water derives from the minerals dissolved, while pure H2O is tasteless. As such, purity in spring and mineral water refers to purity from toxins, pollutants, and microbes. Effects on life
thumb|left|A captive lion drinking water
From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. Tides
Tides are the cyclic rising and falling of Earth's ocean surface caused by the tidal forces of the Moon and the Sun acting on the oceans. Tides cause changes in the depth of the marine and estuarine water bodies and produce oscillating currents known as tidal streams. The changing tide produced at a given location is the result of the changing positions of the Moon and Sun relative to the Earth coupled with the effects of Earth rotation and the local bathymetry. The strip of seashore that is submerged at high tide and exposed at low tide, the intertidal zone, is an important ecological product of ocean tides. Effects on life
thumb|An oasis is an isolated water source with vegetation in desert
thumb|right|Some of the biodiversity of a coral reef
thumb|right|Water reflecting light in Crissy Field
From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. It carries out this role by allowing organic compounds to react in ways that ultimately allow replication. All known forms of life depend on water. Water is vital both as a solvent in which many of the body's solutes dissolve and as an essential part of many metabolic processes within the body. Metabolism is the sum total of anabolism and catabolism. In anabolism, water is removed from molecules (through energy requiring enzymatic chemical reactions) in order to grow larger molecules (e.g. starches, triglycerides and proteins for storage of fuels and information). In catabolism, water is used to break bonds in order to generate smaller molecules (e.g. glucose, fatty acids and amino acids to be used for fuels for energy use or other purposes). Water is thus essential and central to these metabolic processes. Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, or dust collection... Therefore, without water, these metabolic processes would cease to exist, leaving us to muse about what processes would be in its place, such as gas absorption, dust collection, etc. Water is also central to photosynthesis and respiration. Photosynthetic cells use the sun's energy to split off water's hydrogen from oxygen. Hydrogen is combined with CO2 (absorbed from air or water) to form glucose and release oxygen. All living cells use such fuels and oxidize the hydrogen and carbon to capture the sun's energy and reform water and CO2 in the process (cellular respiration). Water is also central to acid-base neutrality 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 hydroxide ion (OH−) to form water. Water is considered to be neutral, with a pH (the negative log of the hydrogen ion concentration) of 7. Acids have pH values less than 7 while bases have values greater than 7. Stomach acid (HCl) is useful to digestion. However, its corrosive effect on the esophagus during reflux can temporarily be neutralized by ingestion of a base such as aluminum hydroxide to produce the neutral molecules water and the salt aluminum chloride. Human biochemistry that involves enzymes usually performs optimally around a biologically neutral pH of 7.4. Aquatic life forms
thumb|right|Some of the biodiversity of a coral reef
thumb|right|Some marine diatoms - a key phytoplankton group
Earth's waters are filled with life. Nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. For example a cell of Escherichia coli contains 70% of water, a human body 60-70%, plant body up to 90% and the body of an adult jellyfish is made up of 94–98% water. Aquatic life forms
thumb|left|Some marine diatoms - a key phytoplankton group
Earth's waters are filled with life. The earliest life forms appeared in water; nearly all fish live exclusively in water, and there are many types of marine mammals, such as dolphins and whales that also live in the water. Some kinds of animals, such as amphibians, spend portions of their lives in water and portions on land. Plants such as kelp and algae grow in the water and are the basis for some underwater ecosystems. Plankton is generally the foundation of the ocean food chain. Different water creatures have found different solutions to obtaining oxygen in the water. Fish have gills instead of lungs, though some species of fish, such as the lungfish, have both. Marine mammals, such as dolphins, whales, otters, and seals need to surface periodically to breathe air. Effects on human civilization
thumb|right|A manual water pump in China
Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Effects on human civilization
thumb|right| Water Fountain
Civilization has historically flourished around rivers and major waterways; Mesopotamia, the so-called cradle of civilization, was situated between the major rivers Tigris and Euphrates; the ancient society of the Egyptians depended entirely upon the Nile. Large metropolises like Rotterdam, London, Montreal, Paris, New York City, Shanghai, Tokyo, Chicago, and Hong Kong owe their success in part to their easy accessibility via water and the resultant expansion of trade. Islands with safe water ports, like Singapore, have flourished for the same reason. In places such as North Africa and the Middle East, where water is more scarce, access to clean drinking water was and is a major factor in human development. Health and pollution
Water fit for human consumption is called drinking water or "potable water". Water that is not fit for drinking but is not harmful for humans when used for food preparation is called safe water. Health and pollution
thumb|Environmental Scientist sampling water. Water fit for human consumption is called drinking water or potable water. Water that is not potable can be made potable by distillation (heating it until it becomes water vapor, and then capturing the vapor without any of the impurities it leaves behind), or by other methods (chemical or heat treatment that kills bacteria). Sometimes the term safe water is applied to potable water of a lower quality threshold (i.e., it is used effectively for nutrition in humans that have weak access to water cleaning processes, and does more good than harm). Water that is not fit for drinking but is not harmful for humans when used for swimming or bathing is called by various names other than potable or drinking water, and is sometimes called safe water, or "safe for bathing". Chlorine is a skin and mucous membrane irritant that is used to make water safe for bathing or drinking. Its use is highly technical and is usually monitored by government regulations (typically 1 part per million (ppm) for drinking water, and 1-2 ppm of chlorine not yet reacted with impurities for bathing water). This natural resource is becoming scarcer in certain places, and its availability is a major social and economic concern. Currently, about 1 billion people around the world routinely drink unhealthy water. Currently, about 1 billion people around the world routinely drink unhealthy water. Most countries accepted the goal of halving by 2015 the number of people worldwide who do not have access to safe water and sanitation during the 2003 G8 Evian summit. G8 "Action plan" decided upon at the 2003 Evian summit Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water supplies and over 1 billion without access to adequate sanitation facilities. Poor water quality and bad sanitation are deadly; some 5 million deaths a year are caused by polluted drinking water. G8 "Action plan" decided upon at the 2003 Evian summit Even if this difficult goal is met, it will still leave more than an estimated half a billion people without access to safe drinking water and over 1 billion without access to adequate sanitation. Poor water quality and bad sanitation are deadly; some 5 million deaths a year are caused by polluted drinking water. Water, however, is not a finite resource (like petroleum is), but rather re-circulated as potable water in precipitation in quantities many degrees of magnitude higher than human consumption. Therefore, it is the relatively small quantity of water in reserve in the earth (about 1% of our drinking water supply, which is replenished in aquifers around every 1 to 10 years), that is a non-renewable resource, and it is, rather, the distribution of potable and irrigation water which is scarce, rather than the actual amount of it that exists on the earth. Water-poor countries use importation of goods as the primary method of importing water (to leave enough for local human consumption), since the manufacturing 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. Some 50 countries, with roughly a third of the world’s population, also suffer from medium or high water stress, and 17 of these extract more water annually than is recharged through their natural water cycles . The strain affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources. Human uses
thumb|right|Water under pressure from a sprinkler
For drinking
About 70% of the fat free mass of the human body is made of water. To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. The strain not only affects surface freshwater bodies like rivers and lakes, but it also degrades groundwater resources. Human uses
Agriculture
thumb|right|irrigation of field crops
The most important use of water in agriculture is for an irrigation and irrigation is key component to produce enough food. Irrigation takes up to 90% of water withdrawn in some developing countries.WBCSD Water Faacts & Trends
As a scientific standard
On 7 April 1795, the gram was defined in France to be equal to "the absolute weight of a volume of pure water equal to a cube of one hundredth of a meter, and to the temperature of the melting ice."Decree relating to the weights and measurements For practical purposes though, a metallic reference standard was required, one thousand times more massive, the kilogram. Work was therefore commissioned to determine precisely how massive one liter of water was. In spite of the fact that the decreed definition of the gram specified water at 0 °C—a highly stable temperature point—the scientists chose to redefine the standard and to perform their measurements at the most stable density point: the temperature at which water reaches maximum density, which was measured at the time as 4 °C.here L'Histoire Du Mètre, La Détermination De L'Unité De Poids
The Kelvin temperature scale of the SI system is based on the triple point of water. The scale is a more accurate development of the Celsius temperature scale ("centigrade"), which is defined by the boiling point (100 °C) and freezing point (0 °C) of water. Natural water consists mainly of the isotopes hydrogen-1 and oxygen-16, but there is also small quantity of heavier hydrogen-2 (deuterium). The amount of deuterium oxides or heavy water is very small, but it still affects the properties of water. Water from rivers and lakes tends to contain less deuterium than seawater. Therefore, a standard water called Vienna Standard Mean Ocean Water is defined as the standard water. For drinking
thumb|right|a young girl is drinking water. The human body is anywhere from 55% to 78% water depending on body size. Re: What percentage of the human body is composed of water? Jeffrey Utz, M.D., The MadSci Network To function properly, the body requires between one and seven liters of water per day to avoid dehydration; the precise amount depends on the level of activity, temperature, humidity, and other factors. Most of this is ingested through foods or beverages other than drinking straight water. It is not clear how much water intake is needed by healthy people, though most experts agree that 8-10 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration. For those who do not have kidney problems, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) 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, which can be fatal. It is not clear how much water intake is needed by healthy people, though most advocates agree that 8–10 glasses of water (approximately 2 liters) daily is the minimum to maintain proper hydration. Medical literature favors a lower consumption, typically 1 liter of water for an average male, excluding extra requirements due to fluid loss from exercise or warm weather. For those who have healthy kidneys, it is rather difficult to drink too much water, but (especially in warm humid weather and while exercising) 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 "fact" that a person should consume eight glasses of water per day cannot be traced back to a scientific source."Drink at least eight glasses of water a day." Really? Is there scientific evidence for "8 × 8"? by Heinz Valdin, Department of Physiology, Dartmouth Medical School, Lebanon, New Hampshire There are other myths such as the effect of water on weight loss and constipation that have been dispelled. Drinking Water - How Much?, Factsmart.org web site and references within
thumb|right|A shower
Original recommendation for water intake in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Drinking Water - How Much?, Factsmart.org web site and references within
Original recommendation for water intake in 1945 by the Food and Nutrition Board of the National Research Council read: "An ordinary standard for diverse persons is 1 milliliter for each calorie of food. Most of this quantity is contained in prepared foods."Food and Nutrition Board, National Academy of Sciences. Recommended Dietary Allowances, revised 1945. National Research Council, Reprint and Circular Series, No. 122, 1945 (Aug), p. 3-18. The latest dietary reference intake report by the United States National Research Council in general recommended (including food sources): 2.7 liters of water total for women and 3.7 liters for men.Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate, Food and Nutrition Board Specifically, pregnant and breastfeeding women need additional fluids to stay hydrated. According to the Institute of Medicine — who recommend that, on average, women consume 2.2 litres and men 3.0 litres — this is recommended to be 2.4 litres (approx. According to the Institute of Medicine—who recommend that, on average, women consume 2.2 litres and men 3.0 litres—this is recommended to be 2.4 litres (approx. 9 cups) for pregnant women and 3 litres (approx. 12.5 cups) for breastfeeding women since an especially large amount of fluid is lost during nursing.http://www.mayoclinic.com/health/water/NU00283 Also noted is that normally, about 20 percent of water intake comes from food, while the rest comes from drinking water and beverages (caffeinated included). Water is excreted from the body in multiple forms; through urine and feces, through sweating, and by exhalation of water vapor in the breath. With physical exertion and heat exposure, water loss will increase and daily fluid needs may increase as well. Humans require water that does not contain too many impurities. thumb|right|Hazard symbol for No drinking water
Humans require water that does not contain too many impurities. Common impurities include metal salts and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for taste enhancement and to provide needed electrolytes. The single largest freshwater resource suitable for drinking is the Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean. The single largest freshwater resource suitable for drinking is Lake Baikal in Siberia, which has a very low salt and calcium content and is very clean. As a solvent
Dissolving (or suspending) is used to wash everyday items such as the human body, clothes, floors, cars, food, and pets. As a thermal transfer agent
Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam. Water is also used in industrial contexts as a coolant, and in almost all power-stations as a coolant and to drive steam turbines to generate electricity. Also, human wastes are carried by water in the sewage system. Its use as a cleaning solvent consumes most of water in industrialized countries. Water can facilitate the chemical processing of wastewater. An aqueous environment can be favourable to the breakdown of pollutants, due to the ability to gain an homogenous solution that is pumpable and flexible to treat. Aerobic treatment can be used by applying oxygen or air to a solution reduce the reactivity of substances within it. Water also facilitates biological processing of waste that have been dissolved within it. Microorganisms that live within water can access dissolved wastes and can feed upon them breaking them down into less polluting substances. Reedbeds and anaerobic digesters are both examples of biological systems that are particularly suited to the treatment of effluents. Typically from both chemical and biological treatment of wastes, there is often a solid residue or cake that is left over from the treatment process. Depending upon its constituent parts, this 'cake' may be dried and spread on land as a fertilizer if it has beneficial properties, or alternatively disposed of in landfill or incinerated. As a heat transfer fluid
thumb|ice used for cooling
Water and steam are commonly used as heat transfer fluids in diverse heat exchanger systems, because of the availability and high heat capacity, both as a coolant and for heating. Cool water may even be naturally available from a lake or the sea. Condensing steam is a particularly efficient heating fluid because of the large heat of vaporization. A disadvantage is that water and steam are somewhat corrosive. In almost all power station, water is the coolant, which vaporizes and drives steam turbines to generate electricity. In the nuclear industry, water can also be used as a neutron moderator. In a pressurized water reactor, water is both a coolant and a moderator. This provides a passive safety measure, as removing the water from the reactor also slows the nuclear reaction down. Extinguishing fires
right|thumb|water is necessary for wildfires fire fighting and other fire fighting
Water has a high heat of vaporization and is relatively inert, which makes it a good fire extinguishing fluid. The evaporation of water carries heat away from the fire. However, water cannot be used to fight fires of electric equipment, because impure water is electrically conductive, or oils and organic solvents, because they float on water and the explosive boiling of water tends to spread the burning liquid. Decomposition of water may have played a role in the Chernobyl disaster. Initially, cooling of the incandescent reactor was attempted, but the result was an explosion, when the extreme heat caused water to flash into steam, thus leading to a steam explosion; it may also have decomposed water into hydrogen and oxygen, which subsequently exploded. Chemical uses
Organic reactions are usually quenched with water or a water solution of a suitable acid, base or buffer. Water is generally effective in removing inorganic salts. In inorganic reactions, water is a common solvent. In organic reactions, it is usually not 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 reactions by water has been observed. Supercritical water has recently been a topic of research. Oxygen-saturated supercritical water combusts organic pollutants efficiently. Recreation
Humans use water for many recreational purposes, as well as for exercising and for sports. Some of these include swimming, waterskiing, boating, fishing, and diving. Some of these include swimming, waterskiing, boating, and diving. In addition, some sports, like ice hockey and ice skating, are played on ice. thumb|right|Some boats in a harbor in Miami Beach, Florida
Lakesides and beaches are popular places for people to go to relax and enjoy recreation. Lakesides, beaches and waterparks are popular places for people to go to relax and enjoy recreation. Many find the sound of flowing water to be calming, too. Some keep fish and other life in water tanks or ponds for show, fun, and companionship. Some keep fish and other life in aquariums or ponds for show, fun, and companionship. Humans also use water for snow sports i.e. skiing or snowboarding, which requires the water to be frozen. People may also use water for play fighting such as with snowballs, water guns or water balloons. Industrial applications
Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. Food processing
Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products. Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) raises the boiling point of water by 0.52 °C, and one mole of salt raises the boiling point by 1.04 degrees while lowering the freezing point of water in a similar way.Vaclacik and Christian, 2003 Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food.DeMan, 1999 Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water. Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity. Not only does microbial growth affect the safety of food but also the preservation and shelf life of food. Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness. Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains. The hardness of water may be altered or treated by using a chemical ion exchange system. 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 increasing hardness, there is a loss of effectiveness for its use as a sanitizer. Power generation
Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. Politics
thumb|left|People waiting in line to gather water during the Siege of Sarajevo
Because of overpopulation, mass consumption, misuse, and water pollution, the availability of drinking water per capita is inadequate and shrinking as of the year 2006. For this reason, water is a strategic resource in the globe and an important element in many political conflicts. Some have predicted that clean water will become the "next oil", making Canada, with this resource in abundance, possibly the richest country in the world. There is a long history of conflict over water, including efforts to gain access to water, the use of water in wars started for other reasons, and tensions over shortages and control. A Chronology of Water-Related Conflicts UNESCO's World Water Development Report (WWDR, 2003) from its World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from diseases related to the consumption of contaminated water or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of sewage disposal; see toilet. Fresh water — now more precious than ever in our history for its extensive use in agriculture, high-tech manufacturing, and energy production — is increasingly receiving attention as a resource requiring better management and sustainable use. OECD countries
thumb|right|350px|Hopetoun Falls near Otway National Park, Victoria, Australia
With nearly 2,000 cubic metres (70,000 ft3) of water per person and per year, the United States leads the world in water consumption per capita. In the Organization for Economic Co-operation and Development (OECD) countries, the U.S. is first for water consumption, then Canada with 1,600 cubic meters (56,000 ft3) of water per person per year, which is about twice the amount of water used by the average person from France, three times as much as the average German, and almost eight times as much as the average Dane. Since 1980, overall water use in Canada has increased by 25.7%. This is five times higher than the overall OECD increase of 4.5%. In contrast, nine OECD nations were able to decrease their overall water use since 1980 (Sweden, the Netherlands, the United States, the United Kingdom, the Czech Republic, Luxembourg, Poland, Finland and Denmark). Water consumption indicator in the OECD countries
United States
Ninety-five percent of the United States' fresh water is underground. One crucial source is a huge underground reservoir, the 1,300-kilometer (800 mi) Ogallala aquifer which stretches from Texas to South Dakota and waters one fifth of U.S. irrigated land. Formed over millions of years, the Ogallala aquifer has since been cut off from its original natural sources. It is being depleted at a rate of 12 billion cubic meters (420 billion ft3) per year, amounting to a total depletion to date of a volume equal to the annual flow of 18 Colorado Rivers. Some estimates say it will dry up in as little as 25 years. Many farmers in the Texas High Plains, which rely particularly on the underground source, are now turning away from irrigated agriculture as they become aware of the hazards of overpumping. Mexico
In Mexico City, an estimated 40% of the city's water is lost through leaky pipes built at the turn of the 20th century. Middle East
The Middle East region has only 1% of the world's available fresh water, which is shared among 5% of the world's population. Thus, in this region, water is an important strategic resource. By 2025, it is predicted that the countries of the Arabian peninsula will be using more than double the amount of water naturally available to them. According to a report by the Arab League, two-thirds of Arab countries have less than 1,000 cubic meters (35,000 ft3) of water per person per year available, which is considered the limit. "Major aspects of scarce water resources management with reference to the Arab countries", Arab League report published for the International Conference on water gestion and water politics in arid zones, in Amman, Jordan, December 1-3, 1999. Quoted by French journalist Christian Chesnot in - French original version freely available here. Jordan, for example, has little water, and dams in other countries have reduced its available water over the years. The 1994 Israel-Jordan Treaty of Peace stated that Israel would give 50 million cubic meters of water (1.7 billion ft3) per year to Jordan, which it refused to do in 1999 before backtracking. The 1994 treaty stated that the two countries would cooperate in order to allow Jordan better access to water resources, notably through dams on the Yarmouk River. See 1994 Israel-Jordan Treaty of Peace, annex II, article II, first paragraph Confronted by this lack of water, Jordan is preparing new techniques to use non-conventional water resources, such as second-hand use of irrigation water and desalinization techniques, which are very costly and are not yet used. A desalinization project will soon be started in Hisban, south of Amman. The Disi groundwater project, in the south of Jordan, will cost at least $250 million to bring out water. Along with the Unity Dam on the Yarmouk River, it is one of Jordan's largest strategic projects. Born in 1987, the "Unity Dam" would involve both Jordan and Syria. This "Unity Dam" still has not been implemented because of Israel's opposition, Jordan and Syrian conflictive relations and refusal of world investors. However, Jordan's reconciliation with Syria following the death of King Hussein represents the removal of one of the project's greatest obstacles. See Christian Chesnot in - French original version freely available here. thumb|left|200px|The Jordan River
Both Israel and Jordan rely on the Jordan River, but Israel controls it, as well as 90% of the water resources in the region. Water is also an important issue in the conflict with the Palestinians - indeed, according to former Israeli prime minister Ariel Sharon quoted by Abel Darwish in the BBC, it was one of the causes of the 1967 Six-Day War. In practice the access to water has been a casus belli for Israel. The Israeli army prohibits Palestinians from pumping water, and settlers use much more advanced pumping equipment. Palestinians complain of a lack of access to water in the region. Israelis in the West Bank use four times as much water as their Palestinian neighbors. According to the World Bank, 90% of the West Bank's water is used by Israelis. Article 40 of the appendix B of the September 28, 1995 Oslo accords stated that "Israel recognizes Palestinians' rights on water in the West Bank". The Golan Heights provide 770 million cubic meters (27 billion ft3) of water per year to Israel, which represents a third of its annual consumption. The Golan's water goes to the Sea of Galilee — Israel's largest reserve — which is then redistributed throughout the country by the National Water Carrier. The Golan, which Israel annexed, represents a strategic territory for Israel because of its water resources.. However, the level on the Sea of Galilee has dropped over the years, sparking fears that Israel's main water reservoir will become salinated. On its northern border, Israel threatened military action in 2002 when Lebanon opened a new pumping station taking water from a river feeding the Jordan. To help ease the crisis, Israel has agreed to buy water from Turkey and is investigating the construction of desalination plants. Iraq and Syria watched with apprehension the construction of the Atatürk Dam in Turkey and a projected system of 22 dams on the Tigris and Euphrates rivers. According to the BBC, the list of 'water-scarce' countries in the region grew steadily from three in 1955 to eight in 1990 with another seven expected to be added within 20 years, including three Nile nations (the Nile is shared by nine countries). Asia
thumb|300px|Three Gorges Dam, receiving, upstream side, 26 July, 2004
In Asia, Cambodia and Vietnam are concerned by China's and Laos' attempts to control the flux of water. China is also preparing the Three Gorges Dam project on the Yangtze River, which would become the world's largest dam, causing many social and environmental problems. It also has a project to divert water from the Yangtze to the dwindling Yellow River, which feeds China's most important farming region. thumb|left|Ganges river delta, Bangladesh and India
The Ganges is disputed between India and Bangladesh. The water reserves are being quickly depleted and polluted, while the glacier feeding the sacred Hindu river is retreating hundreds of feet each year because of global warming and deforestation in the Himalayas, which is causing subsoil streams flowing into the Ganges river to dry up. Downstream, India controls the flow to Bangladesh with the Farakka Barrage, 10 kilometers (6 mi) on the Indian side of the border. Until the late 1990s, India used the barrage to divert the river to Calcutta to keep the city's port from drying up during the dry season. This denied Bangladeshi farmers water and silt, and it left the Sundarban wetlands and mangrove forests at the river's delta seriously threatened. The two countries have now signed an agreement to share the water more equally. Water quality, however, remains a problem, with high levels of arsenic and untreated sewage in the river water. South America
The Guaraní Aquifer, located between the Mercosur countries of Argentina, Brazil, Bolivia and Paraguay, with a volume of about 40,000 km³, is an important source of fresh potable water for all four countries. Privatization
Privatization of water companies has been contested on several occasions because of poor water quality, increasing prices, and ethical concerns. In Bolivia for example, the proposed privatization of water companies by the IMF was met by popular protests in Cochabamba in 2000, which ousted Bechtel, an American engineering firm based in San Francisco. SUEZ has started retreating from South America because of similar protests in Buenos Aires, Santa Fe, and Córdoba, Argentina. Consumers took to the streets to protest water rate hikes of as much as 500% mandated by SUEZ. In South and Central America, SUEZ has water concessions in Argentina, Bolivia, Brazil and Mexico. "Bolivian officials fault SUEZ for not connecting enough households to water lines as mandated by its contract and for charging as much as $455 a connection, or about three times the average monthly salary of an office clerk", according to the Mercury News. South Africa also made moves to privatize water, provoking an outbreak of cholera killing 200. In 1997, World Bank consultants assisted the Philippine government in the privatization of the city of Manila's Metropolitan Waterworks and Sewerage Systems (MWSS). By 2003, water price increases registered at 81% in the east zone of the Philippines and 36% in the west region. As services became more expensive and inefficient under privatization, there was reduced access to water for poor households. In October 2003, the Freedom from Debt Coalition reported that the diminished access to clean water resulted in an outbreak of cholera and other gastro-intestinal diseases. Regulation
right|thumb|220px|A water-carrier in India, circa ~1882. They may also make fountains and use water in their public or private decorations. Water industry
right|thumb|220px|A water-carrier in India, circa ~1882. In many places where running water is not available, water has to be transported by people. The water industry provides drinking water and wastewater services (including sewage treatment) to households and industry. thumb|left|A manual water pump in China
left|thumb|water purification facility
Water supply facilities includes for example water wells cisterns for rainwater harvesting, water supply network, water purification facilities, water tanks, water towers, water pipes including old aqueducts. Atmospheric water generator is in development. Drinking water is often collected at springs, extracted from artificial borings in the ground, or wells. Building more wells in adequate places is thus a possible way to produce more water, assuming the aquifers can supply an adequate flow. Other water sources are rainwater and river or lake water. This surface water, however, must be purified for human consumption. This may involve removal of undissolved substances, dissolved substances and harmful microbes. Popular methods are filtering with sand which only removes undissolved material, while chlorination and boiling kill harmful microbes. Distillation does all three functions. More advanced techniques exist, such as reverse osmosis. Desalination of abundant ocean or seawater is a more expensive solution used in coastal arid climates. The distribution of drinking water is done through municipal water systems or as bottled water. Governments in many countries have programs to distribute water to the needy at no charge. Others argue that the market mechanism and free enterprise are best to manage this rare resource and to finance the boring of wells or the construction of dams and reservoirs. Reducing waste by using drinking water only for human consumption is another option. In some cities such as Hong Kong, sea water is extensively used for flushing toilets citywide in order to conserve fresh water resources. Polluting water may be the biggest single misuse of water; to the extent that a pollutant limits other uses of the water, it becomes a waste of the resource, regardless of benefits to the polluter. Like other types of pollution, this does not enter standard accounting of market costs, being conceived as externalities for which the market cannot account. Thus other people pay the price of water pollution, while the private firms' profits are not redistributed to the local population victim of this pollution. Pharmaceuticals consumed by humans often end up in the waterways and can have detrimental effects on aquatic life if they bioaccumulate and if they are not biodegradable. Wastewater facilities are sewers and wastewater treatment plants. Another way to remove pollution from surface runoff water is bioswale. Industrial applications
right|thumb|Three Gorges Dam is the largest hydro-electric power station
Water is used in power generation. Hydroelectricity is electricity obtained from hydropower. Hydroelectric power comes from water driving a water turbine connected to a generator. Hydroelectricity is a low-cost, non-polluting, renewable energy source. The energy is supplied by the sun. Heat from the sun evaporates water, which condenses as rain in higher altitudes, from where it flows down. Pressurized water is used in water blasting and water jet cutters. Also, very high pressure water guns are used for precise cutting. It works very well, is relatively safe, and is not harmful to the environment. It is also used in the cooling of machinery to prevent 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, in addition to its use as a chemical solvent. Discharge of untreated water from industrial uses is pollution. Pollution includes discharged solutes (chemical pollution) and discharged coolant water (thermal pollution). Industry requires pure water for many applications and utilizes a variety of purification techniques both in water supply and discharge. Various uses of water include water fuel cell and water ionizer. Food processing
thumb|Boiling the food while cooking. Water plays many critical roles within the field of food science. It is important for a food scientist to understand the roles that water plays within food processing to ensure the success of their products. Solutes such as salts and sugars found in water affect the physical properties of water. The boiling and freezing points of water is affected by solutes. One mole of sucrose (sugar) raises the boiling point of water by 0.52 °C, and one mole of salt raises the boiling point by 1.04 °C while lowering the freezing point of water in a similar way.Vaclacik and Christian, 2003 Solutes in water also affect water activity which affects many chemical reactions and the growth of microbes in food.DeMan, 1999 Water activity can be described as a ratio of the vapor pressure of water in a solution to the vapor pressure of pure water. Solutes in water lower water activity. This is important to know because most bacterial growth ceases at low levels of water activity. Not only does microbial growth affect the safety of food but also the preservation and shelf life of food. Water hardness is also a critical factor in food processing. It can dramatically affect the quality of a product as well as playing a role in sanitation. Water hardness is classified based on the amounts of removable calcium carbonate salt it contains per gallon. Water hardness is measured in grains; 0.064 g calcium carbonate is equivalent to one grain of hardness. Water is classified as soft if it contains 1 to 4 grains, medium if it contains 5 to 10 grains and hard if it contains 11 to 20 grains. The hardness of water may be altered or treated by using a chemical ion exchange system. 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 increasing hardness, there is a loss of effectiveness for its use as a sanitizer. Boiling, steaming, and simmering are popular cooking methods that often require immersing food in water or its gaseous state, steam. While cooking water is used for dishwashing too. Water politics and water crisis
Water politics is politics affected by water and water resources. Because of overpopulation, mass consumption, misuse, and water pollution, the availability of drinking water per capita is inadequate and shrinking as of the year 2006. For this reason, water is a strategic resource in the globe and an important element in many political conflicts. It causes health impacts and damage to biodiversity. The serious worldwide water situation is called water crisis. UNESCO's World Water Development Report (WWDR, 2003) from its World Water Assessment Program indicates that, in the next 20 years, the quantity of water available to everyone is predicted to decrease by 30%. 40% of the world's inhabitants currently have insufficient fresh water for minimal hygiene. More than 2.2 million people died in 2000 from waterborne diseases (related to the consumption of contaminated water) or drought. In 2004, the UK charity WaterAid reported that a child dies every 15 seconds from easily preventable water-related diseases; often this means lack of sewage disposal; see toilet. To halve, by 2015, the proportion of people without sustainable access to safe drinking water is one of the Millennium Development Goals. Fresh water — now more precious than ever in our history for its extensive use in agriculture, high-tech manufacturing, and energy production — is increasingly receiving attention as a resource requiring better water management and sustainable use. Organizations concerned in water protection include International Water Association (IWA), WaterAid, Water 1st, American Water Resources Association. Water related conventions are United Nations Convention to Combat Desertification (UNCCD), International Convention for the Prevention of Pollution from Ships, United Nations Convention on the Law of the Sea and Ramsar Convention. World Day for Water takes place at March 22 and World Ocean Day at June 8. Water used in the production of a good or service is virtual water. Religion, philosophy, and literature
thumb|225px|A Hindu ablution as practiced in Tamil Nadu
Water is considered a purifier in most religions. Major faiths that incorporate ritual washing (ablution) include Hinduism, Christianity, Islam, Judaism, and Shinto. Water baptism is a central sacrament of Christianity; it is also a part of the practice of other religions, including Judaism (mikvah) and Sikhism (Amrit Sanskar). Major faiths that incorporate ritual washing (ablution) include Christianity, Hinduism, Rastafarianism, Islam, Shinto, Taoism, and Judaism. 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 can be done in most cases 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 in the Bible 442 times in the New International Version and 363 times in the King James Version: 2 Peter 3:5(b) states, "The earth was formed out of water and by water" (NIV). Some faiths use water especially prepared for religious purposes (holy water in some Christian denominations, Amrit in Sikhism and Hinduism). Many religions also consider particular sources or bodies of water to be sacred or at least auspicious; examples include Lourdes in Roman Catholicism, the Zamzam Well in Islam and the River Ganges (among many others) in Hinduism. In Neo-Paganism water is often combined with salt in the first steps of a ritual, to act as a purifier of worshippers and the altar, symbolising both cleansing tears and the ocean. Many religions also consider particular sources or bodies of water to be sacred or at least auspicious; examples include Lourdes in Roman Catholicism, the Jordan River (at least symbolically) in some Christian churches, the Zamzam Well in Islam and the River Ganges (among many others) in Hinduism. In Neo-Paganism water is often combined with salt in the first steps of a ritual, to act as a purifier of worshipers and the altar, symbolising both cleansing tears and the ocean. Water is often believed to have spiritual powers. In Celtic mythology, Sulis is the local goddess of thermal springs; in Hinduism, the Ganges is also personified as a goddess, while Saraswati have been referred to as goddess in Vedas. Also water is one of the "panch-tatva"s (basic 5 elements, others including fire, earth, space, air). Alternatively, gods can be patrons of particular springs, rivers, or lakes: for example in Greek and Roman mythology, Peneus was a river god, one of the three thousand Oceanids. In Islam, not only does water give life, but every life is itself made of water: "We made from water every living thing". Sura of Al-Anbiya 21:30
The 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. Sura of Al-Anbiya 21:30
The 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. Water was also one of the five elements in traditional Chinese philosophy, along with earth, fire, wood, and metal. Water also plays an important role in literature as a symbol of purification. Examples include the critical importance of a river in As I Lay Dying by William Faulkner and the drowning of Ophelia in Hamlet. See also
Main lists: List of water related topics and List by water type Atmospheric water generator
Bioswale
Carbonation
Cistern
Color of water
Dehydration (hypohydration) vs. hyperhydration
Desalination
Dihydrogen monoxide hoax
Distilled water
Drinking water
Drought
Ecohydrology
Evapotranspiration
Flood
Fresh water
Heavy water
Hydrological transport model
Hydrography
Hydrology
Hydropower
Hydrosphere
Ice
Irrigation
Mineral water
Origin of water on Earth
Precipitation (meteorology)
Rain
Rainwater harvesting
Safe water
Sea water
Spring water
Steam
Tide
United Nations Convention to Combat Desertification (UNCCD). Virtual water
Wastewater
WaterAid (international non-profit organisation). Water crisis
Water (molecule) - Water (data page)
Water cycle
Water fuel cell
Water industry
Water intoxication
Water ionizer
Water memory
Water park
Water purification
Water quality
Water resources
Water right
Water sport (recreation)
Water tank
Water torture
World Ocean Day
World Water Day
References
Cited references
General references
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
Property of Water and Water Steam w Thermodynamic Surface
PH Gleick and associates, The World's Water: The Biennial Report on Freshwater Resources. References
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. E.; "Supercooled and Glassy Water", Physics Today'' 56''' (6), p. 40–46 (2003). Downloadable PDF (1.9 MB)
Water as a natural resource
(November 10, 2006)| ISBN-13: 9781597261050]
(Cambridge Middle East Library)
External links
Water UK, Water for Health: Ask About: Adults : Water requirements in adults
Water for kids
Answers to several questions of curious youngsters related to water
American Water Resources Association
WaterAid - Charity dedicated to the provision of clean water, sanitation and hygiene education
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zh:水 Downloadable PDF (1.9 MB)
Water SA
Water as a natural resource
(November 10, 2006)| ISBN-13: 9781597261050]
(Cambridge Middle East Library)
Category:Natural resources
Category:Oxygen compounds
Category:Hydrogen compounds
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