   #copyright

Water

2007 Schools Wikipedia Selection. Related subjects: Climate and the Weather

   Water is a tasteless, odourless substance that is essential to all
   known forms of life and is known as the universal solvent. It appears
   colorless to the naked eye in small quantities. It covers nearly 70% of
   Earth's surface. The UN Environment Program estimates there are 1.4
   billion cubic kilometres (330 million mi^3) available on Earth, and it
   exists in many forms. It appears mostly in the oceans (saltwater) and
   polar ice caps, but it is also present as clouds, rain water, rivers,
   freshwater aquifers, lakes, and sea ice. Water in these bodies
   perpetually moves through a cycle of evaporation, precipitation, and
   runoff to the sea. Clean water is essential to human life. In many
   parts of the world, it is in short supply. Significant quantities exist
   on the moons Europa and Enceladus. Thales of Miletus, an early Greek
   philosopher, known for his analysis of the scope and nature of the term
   " landscaping", believed that "all is water."
   Impact of a drop of water.
   Enlarge
   Impact of a drop of water.
   Trillium Lake in the Mt. Hood National Forest
   Enlarge
   Trillium Lake in the Mt. Hood National Forest

Chemical and physical properties

   Water
   This shows the basic geometric structure of a molecule of water. This
   space-filled model shows the molecular structure of water.
   Information and properties
   Systematic name water
   Alternative names aqua, dihydrogen monoxide,
   hydrogen hydroxide
   Molecular formula H[2]O
   Molar mass 18.0153 g/mol
   Density and phase 1.000 g/cm^3, liquid
   0.917 g/cm^3, solid
   Melting point 0 °C (273.15 K) (32 ºF)
   Boiling point 100 °C (373.15 K) (212ºF)
   Specific heat capacity (liquid) 4184 J/(kg·K)
   Supplementary data page
   Disclaimer and references

   Water has the chemical formula H[2]O meaning that one molecule of water
   is composed of two hydrogen atoms and one oxygen atom. It can be
   described ionically as HOH, with a hydrogen ion (H^+) that is bonded to
   a hydroxide ion (OH^-). It is in dynamic equilibrium between the liquid
   and vapor states at standard temperature and pressure. Water alone is a
   colourless, tasteless, and odourless liquid, but upon standing it takes
   on the traces of carbon dioxide in the air and tends toward a sour
   solution of carbonic acid that is unpleasant-tasting and more
   inhospitable to life.

   Water is often referred to in the sciences as the universal solvent and
   the only pure substance found naturally in all three states of matter;
   however, "found" should not mean that water is the only such natural
   substance that can be in three states at regular Earthly conditions, as
   its two elements are much more abundant than those of at least ten
   other molecules that share water's range but that are often found
   dissolved in water or shale. Examples are acetic acid, formic acid,
   hydrazine, dioxane, and benzene.
   High concentrations of dissolved lime make the water of Havasu Falls
   appear turquoise.
   Enlarge
   High concentrations of dissolved lime make the water of Havasu Falls
   appear turquoise.

Colour

   Iron-rich rocks have turned this river red.
   Enlarge
   Iron-rich rocks have turned this river red.

   Water strongly absorbs infrared radiation. As infrared radiation is
   next to red-colored light on the EM spectrum, a small amount of visible
   red light is absorbed as well. This results in pure water appearing
   slightly blue when seen in mass quantities such as a lake or ocean. The
   blue color can easily be seen as one sees the blue color of the sea or
   a clear lake under an overcast sky, which means that it is not a
   reflection of the sky. In practice, the colour of water can vary
   greatly, depending on impurities. Limestone turns bodies of water
   turquoise, while iron compounds turn it red/brown and copper compounds
   create an intense blue. Algae commonly colors water green.

Solvation

   Water is a very good solvent, dissolving many types of substances. The
   substances that will mix well and dissolve in water (e.g. salts) are
   known as " hydrophilic" (water-loving) substances, and 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 themselves. If the ability of a substance to dissolve
   in water cannot, the molecules are " pushed out" from amongst the water
   and do not dissolve.

Cohesion and adhesion

   Dew drops adhering to a spider web.
   Enlarge
   Dew drops adhering to a spider web.

   Water sticks to itself ( cohesion) because it is polar, meaning one end
   of the molecule has slightly more negative charge than the other, which
   has slightly more positive charge. In water, this happens because the
   oxygen atom is more electronegative—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 the hydrogen atoms.

   Water also has high adhesion properties because of its polar nature.

Surface tension

   This daisy is under the water level, which has risen gently and
   smoothly. Surface tension prevents the water from submerging the
   flower.
   Enlarge
   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 nonsoluble surface such as polythene: the water stays
   together as drops. 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.
   They are particularly important when cells are dehydrated by exposure
   to dry atmospheres or to extracellular freezing.'

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 more water is pulled on top of that water
   through cohesion, which sticks to the sides of the tube. The process is
   repeated as the water flows up the tube until there is enough water
   that gravity can counteract the adhesive force.

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), 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
   swings in temperature.

Freezing point

   A simple but environmentally important and unusual property of water is
   that its common solid form, ice, floats on its liquid form. This solid
   phase is not as dense as liquid water because of the geometry of the
   strong hydrogen bonds which are formed only at lower temperatures. For
   almost all other substances and for all other 11 uncommon phases, the
   solid form is denser 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. Almost all other chemicals are denser as
   solids than they are as liquids and freeze from the bottom up.

Triple point

   The triple point of water (the single combination of pressure and
   temperature at which pure liquid water, ice, and water vapour 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 (0.0060373
   atm).

Electrical conductivity

   A common misconception about water is that it is a powerful conductor
   of electricity, with risks of electrocution explaining this popular
   belief. 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). Pure water can also be electrolyzed into oxygen and hydrogen gases
   but without any dissolved ions; this is a very slow process and thus
   very little current is conducted.

Forms

   Snowflakes by Wilson Bentley, 1902.
   Enlarge
   Snowflakes by Wilson Bentley, 1902.

   Water takes many different forms on Earth: water vapor and clouds in
   the sky; seawater and icebergs in the ocean; glaciers and rivers in the
   mountains; and aquifers in the ground, to name but a few. Through
   evaporation, precipitation, and runoff, water is continuously flowing
   from one form to another, in what is called the water cycle.
   Rainbows like this one are formed by rain drops acting as a natural
   prism.
   Enlarge
   Rainbows like this one are formed by rain drops acting as a natural
   prism.

   Because of the importance of precipitation to agriculture, and to
   mankind in general, different names are given to its various forms:
   rain is common in most countries, and hail, snow, fog and dew are other
   examples. When appropriately lit, water drops in the air can refract
   sunlight to produce rainbows.

   Similarly, water runoffs have played major roles in human history as
   rivers and irrigation brought the water needed for agriculture. Rivers
   and seas offered opportunity for travel and commerce. Through erosion,
   runoffs played a major part in shaping the environment providing river
   valleys and deltas which provide rich soil and level ground for the
   establishment of population centers.

   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.

   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 drinkability of water:
   animals generally dislike the taste of salty sea water and the putrid
   swamps and favour 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 H[2]O is tasteless. As such, purity in
   spring and mineral water refers to purity from toxins, pollutants, and
   microbes.

Position of the Earth relating to water

   Over two thirds of the earth's surface is covered with water, 97.2% of
   which is contained in the five oceans. The Antarctic ice sheet,
   containing 90% of all fresh water on the planet, is visible at the
   bottom. Atmospheric water vapour can be seen as clouds, contributing to
   the earth's albedo.
   Enlarge
   Over two thirds of the earth's surface is covered with water, 97.2% of
   which is contained in the five oceans. The Antarctic ice sheet,
   containing 90% of all fresh water on the planet, is visible at the
   bottom. Atmospheric water vapour can be seen as clouds, contributing to
   the earth's albedo.

   Scientists theorize that most of the universe's water is produced as a
   byproduct of star formation. Gary Melnick, a scientist at the
   Harvard-Smithsonian Centre for Astrophysics, explains: "For reasons
   that aren't entirely understood, when stars are born, their birth is
   accompanied by a strong outward wind of gas and dust. When this
   outflowing material eventually impacts the surrounding gas, the shock
   waves that are created compress and heat the gas. The water we observe
   is rapidly produced in this warm dense gas."

   The coexistence of the solid, liquid, and gaseous phases of water on
   Earth is vital to existence of life on Earth. However, if the Earth's
   location in the solar system were even marginally closer to or further
   from the Sun (a million miles or so), the conditions which allow the
   three forms to be present simultaneously would be far less likely to
   exist.

   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
   less massive, 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.

Effects on life

   A lion drinking water.
   Enlarge
   A 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. It carries out this role by allowing organic compounds to
   react in ways that ultimately allows 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. startches, 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.

   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
   (burn) 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 neutraled by ingestion of a base such as aluminum
   hydroxide to produce the neutral molecules water and the salt aluminium
   chloride. Human biochemistry that involves enzymes usually performs
   optimally at water's neutral ph of 7.

Aquatic life forms

   Some of the biodiversity of a coral reef.
   Enlarge
   Some of the biodiversity of a coral reef.

   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. 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.
   Some marine diatoms - a key phytoplankton group.
   Enlarge
   Some marine diatoms - a key phytoplankton group.

   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

   A manual water pump in China.
   Enlarge
   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. Large
   metropolises like Rotterdam, London, Montreal, Paris, New York, and
   Tokyo owe their success in part to their easy accessibility via water
   and the resultant expansion of trade. Islands with safe water ports,
   like Singapore and Hong Kong, 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

   Drinking water from a tap.
   Enlarge
   Drinking water from a tap.

   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.

   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. 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. 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.

   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

   Water under pressure from a sprinkler.
   Enlarge
   Water under pressure from a sprinkler.
   A leaking tap.
   Enlarge
   A leaking tap.

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 litres 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. 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. The "fact" that a person should consume eight glasses of water
   per day cannot be traced back to a scientific source. There are other
   myths such as the effect of water on weight loss and constipation that
   have been dispelled.
   A shower.
   Enlarge
   A shower.

   The latest dietary reference intake report by the United States
   National Research Council recommended (including food sources): 2.7
   litres of water total for women and 3.7 litres for men. Water is lost
   from the body in urine and feces, through sweating, and by exhalation
   of water vapor in the breath.

   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.

As a solvent

   Dissolving (or suspending) is used to wash everyday items such as the
   human body, clothes, floors, cars, food, and pets. Sometimes water is
   not enough, and many chemicals can be added in order to improve the
   solvating power of water. These chemicals include saliva, soap,
   shampoo, alcohol, vinegar and various surfactants; these are all
   examples of emulsifying agents. When water will not do (to remove a
   nonwater-soluble substance such as paint), other solvents are used,
   such as ethanol (in meths) or acetone (in nail varnish remover).

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
   powerstations as a coolant and to drive steam turbines to generate
   electricity. In the nuclear industry, water can also be used as a
   neutron moderator.

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. In addition, some sports, like ice hockey
   and ice skating, are played on ice.
   Some boats in a harbor in Miami Beach, Florida.
   Enlarge
   Some boats in a harbour in Miami Beach, Florida.

   Lakesides and beaches 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. People may also use water for play fighting
   such as with water guns or water balloons.

Industrial applications

   Pressurized water is used in water blasting and water jet cutters.

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 insure 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 degrees 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 (Vaclacik and Christian, 2003).
   Solutes in water lower water activity. This is important to know
   because most bacterial growth ceases at low levels of water activity
   (DeMan, 1999). Not only does microbial growth affect the safety of food
   but also the preservation and shelf life of food. Figure 2 shows a
   slice of moldy bread, an example of microbial growth.

   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 gm calcium carbonate is equivalent to one
   grain of hardness (Vaclacik and Christian, 2003). 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 (Vaclacik and Christian,
   2003). 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 (Vaclacik and
   Christian, 2003).

Politics

   People waiting in line to gather water during the Siege of Sarajevo.
   Enlarge
   People waiting in line to gather water during the Siege of Sarajevo.

   Because of overpopulation in many regions of the world, 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. 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. 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

   Hopetoun Falls near Otway National Park, Victoria, Australia.
   Enlarge
   Hopetoun Falls near Otway National Park, Victoria, Australia.

   With nearly 2,000  cubic metres (70,000 ft^3) of water per person and
   per year, the United States leads the world in water consumption per
   capita (a large quantity of golf fields and car washing partly explain
   this massive consumption). 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 metres (56,000 ft^3) 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).

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
   metres (420 billion ft^3) 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. Many people advise
   that it is not safe to drink and may cause sickness.

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 ft^3) of water per person per
   year available, which is considered the limit.

   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 ft^3) 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. 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 conflictual 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.
   The Jordan River.
   Enlarge
   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 neighbours. 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 ft^3) 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&dash;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

   Three Gorges Dam, receiving, upstream side, 26 July 2004.
   Enlarge
   Three Gorges Dam, receiving, upstream side, 26 July 2004.

   In Asia, Vietnam and Cambodia 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.
   Ganges river delta, Bangladesh and India.
   Enlarge
   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. ASIA.

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 bad quality of the water, increasing prices, and
   ethical concerns. In Bolivia for example, the proposed privatization of
   water companies by the IMF were 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.

Regulation

   Two people reflected in the water of a fish pond.
   Enlarge
   Two people reflected in the water of a fish pond.

   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.

Religion, philosophy, and literature

   A Hindu ablution as practiced in Tamil Nadu.
   Enlarge
   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). 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.

   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.

   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. 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.

   Retrieved from " http://en.wikipedia.org/wiki/Water"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
