Water

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Water (from the Old English waeter; c.f German "Wasser", from Proto-Indo-European language*wod-or, "water"), in its pure form, is a tasteless, odorless substance that is essential to all known forms of life and is known also as the most universal solvent. Without it, life as we know it would not exist. It appears colorless to the naked eye in small quantities, though it can be seen to be blue in large quantities or with scientific instruments<ref>The Color of Water: Visibility Under Water</ref>. An abundant substance on Earth, it exists in many places and forms. It appears mostly in the oceans and polar ice caps, but also as clouds, rain water, rivers, freshwater aquifers, and sea ice. On the planet, water is continuously moving through the water cycle involving evaporation, precipitation, and runoff to the sea.

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

Water fit for human consumption is called drinking water or "potable water". Water that is not specifically made 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 have 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 <ref> G8 "Action plan" decided upon at the 2003 Evian summit </ref>. 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 killers; some 5 million deaths a year are caused by polluted drinking water.

Hardly surprising, since 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.

Contents 1 Molecular properties 1.1 Forms of water 1.2 Water in biology 1.2.1 Heat capacity and heat of vaporization 1.2.2 Solvation 1.2.2.1 Cohesion 1.2.2.2 Capillary Action 1.3 Water in human civilization 2 Human uses of water 3 Water as a precious resource: politics of water 3.1 Water in the OECD countries 3.2 Water in Central America 3.3 Water in the Middle East 3.4 Water in Asia 3.5 Water in South America 4 See also 5 References 5.1 Notes 6 External links

Molecular properties

Water has the chemical formula H₂O, meaning that one molecule of water is composed of two hydrogen atoms and one oxygen atom. It can also 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. At room temperature, it is a nearly colorless, tasteless, and odorless liquid. It is often referred to in the sciences as the universal solvent and the only pure substance found naturally in all three states of matter.

Forms of water

Water takes many different shapes on Earth: water vapor and clouds in the sky, waves and icebergs in the sea, glaciers in the mountain, 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.

Because of the importance of precipitation to agriculture, and to mankind in general, different names are given to its various forms: while rain is common in most countries, other phenomena are quite surprising when seen for the first time. Hail, snow, fog or dew are 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 river delta 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.

Because water can contain many different substances, it can taste or smell very differently. In fact, humans and other animals have developed their senses to be able to evaluate the drinkability 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.

Water in biology

From a biological standpoint, water has many distinct properties that are critical for the proliferation of life that set it apart from other substances. Water carries out this role by allowing organic compounds to react in ways that ultimately allows replication. It is a good solvent and has a high surface tension, and thus allows organic compounds and living things to be transported in it. Fresh water has its greatest density under normal atmospheric pressure at 4 °C, then becoming less dense as it freezes or heats up from this point. As a stable, polar molecule prevalent in the atmosphere, it plays an important role as a greenhouse gas absorbing infrared radiation, without which, Earth's average surface temperature would be −18 ° Celsius.

Heat capacity and heat of vaporization

Water also has an unusually high specific heat capacity and heat of vaporization compared with other members of Periodic table group 16 elements due to hydrogen bonding. These two factors give water a moderating influence on Earth's climate by buffering large swings in temperature. Because it absorbs strongly in the infrared portion of the light spectrum, a small amount of visible red light is absorbed as well, resulting in water's slightly blue color when seen in mass quantities such as a lake or ocean.

Solvation

Water is a very good solvent, dissolving many types of substances, such as various salts and sugar. It facilitates chemical interactions such as the process of metabolism. Some substances, however, do not mix well with water, including lipids, some proteins and other hydrophobic substances. The chemical force explaining (among other things) why oil and water, famously, do not mix is Van der Waals force. Cell membranes take advantage of this property to carefully control interactions between their contents and external chemicals, which is facilitated somewhat by the surface tension of water.

Cohesion

Water sticks to itself because it is polar, (one ion of the molecule has more negative charge than the others). The oxygen ion in water has a slighly higher negative charge than the hydrogen ion.

Capillary Action

Water will actually flow up hill due to capillary action. The best example is that water will flow up a tube. The water adheres to the sides of the tube, and then more water is pulled on top of that water due to 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 polar properties of water.

Water in human civilization

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 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 precisely this reason. In places such as North Africa and the Middle East, where water is scarcer, access to clean drinking water was and is a major factor in human development.

Human uses of water

All known forms of life depend on water. (Note however that some bacteria and plant seeds can enter a cryptobiotic state for an indefinite period when dehydrated, and "come back to life" when returned to a wet environment). Water is a vital part of many metabolic processes within the body, and significant quantities of water are used during the digestion of food.

About 72% 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 depending on the level of activity, temperature, humidity, and other factors. However, most of this is ingested through other foods or beverages (hot tea being often used in deserts to avoid dehydration, etc.) It is not clear how much water intake is needed by healthy people. However, 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) 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 <ref> "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 </ref>. There are other myths such as the effect of water on weight loss and constipation that have been dispelled <ref> Drinking Water - How Much?, Factsmart.org web site and references within </ref>. The latest dietary reference intake report by the US National Research Council recommended 2.7 liters of water total (including food sources) for women and 3.7 liters for men <ref> Dietary Reference Intakes: Water, Potassium, Sodium, Chloride, and Sulfate, Food and Nutrition Board</ref>. 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 much salt or other impurities. Common impurities include chemicals and/or harmful bacteria, such as Vibrio. Some solutes are acceptable and even desirable for perceived taste enhancement and to provide needed electrolytes.

Water as a precious resource: politics of water

Because of overpopulation in many regions of the world, mass consumption 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 <ref> A Chronology of Water-Related Conflicts </ref>. 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 due to 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.

Water in the OECD countries

With nearly 2,000 cubic metres of water per person and per year, the United States leads the world in water consumption per capita (a large quantity of golf courses and car washing partly explain this massive consumption). In the Organisation for Economic Co-operation and Development (OECD) countries, the U.S. comes first for water consumption, then Canada with 1,600 cubic metres 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) <ref> Water consumption indicator in the OECD countries </ref> <ref> Golf 'is water hazard', BBC News, March 17, 2003, url=http://news.bbc.co.uk/1/hi/sci/tech/2857587.stm </ref>.

Ninety-five percent of the United States' fresh water is underground. One crucial source is a huge underground reservoir, the 800-mile (1,300 km) 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 a 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 Texan 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 <ref> Ogallala aquifer - Water hot spots, BBC News, url=http://news.bbc.co.uk/1/shared/spl/hi/world/03/world_forum/water/html/ogallala_aquifer.stm </ref>.

Water in Central America

In Mexico City, an estimated 40% of the city's water is lost through leaky pipes built at the turn of the century <ref> Mexico City - Water hot spots, publisher=BBC News, url=http://news.bbc.co.uk/1/shared/spl/hi/world/03/world_forum/water/html/mexico_city.stm}} </ref>.

Water in the Middle East

The Middle East region has only 1% of the world's available fresh water, which is shared between 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 <ref> Water shortages 'foster terrorism', BBC News, date=March 18, 2003, url=http://news.bbc.co.uk/1/hi/sci/tech/2859937.stm </ref>. According to a report by the Arab League, two-thirds of Arab countries have less than 1,000 cubic meters water per person per year, which is considered the limit <ref> "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 Drought in the Middle East, Monde diplomatique, date=February 2000, url=http://mondediplo.com/2000/02/08chesnot - French original version freely available here. Compare with the 1,600 cubic meters of water used per person and per year in Canada, for example </ref>.

Water in Asia

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 one of the world's largest dams, 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.

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 causing subsoil streams flowing into the Ganges river to dry up. Downstream, India controls the flow to Bangladesh with the Farakka Barrage, 10 km on the Indian side of the border. Until the late 1990s, India used the barrage to divert the river to Calcutta to stop the city's port drying up during the dry season. This denied Bangladeshi farmers water and silt, and 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 huge problem, with high levels of arsenic and untreated sewage in the river water <ref> Ganges river - water hot spots, BBC News, url=http://news.bbc.co.uk/1/shared/spl/hi/world/03/world_forum/water/html/river_ganges.stm </ref>.

Water in South America

The Guaraní Aquifer, located between the Mercosur countries of Argentina, Brazil, Bolivia and Paraguay, with ith a volume of about 40000 km³, is an important source of fresh, drinkable water, for all four countries. The increasing presence of US military forces in Paraguay, most notably near the Mariscal Estigarribia airport, has lifted some concerns about the reason for this new interest toward Asunción (Paraguay).

The Argentine film Sed, Invasión Gota a Gota ("Thirst, Invasion Drop by Drop"), directed by Mausi Martinéz, portrayed the US military as slowly but steadily increasing its presence in the area known as the Triple Frontera (Triple Frontier, between Paraguay, Argentina and Brazil). Martinéz alleged that it is the water which brings the Americans to the area, and she fears a subtle takeover before the local governments even realize what is going on. Similar concerns could be found in the Clarín newspaper end of 2005, which explained the new military agreement between Paraguay and the US, as well as United States Secretary of Defense Donald Rumsfeld's visit to Asunción and the creation of the military base, by its presence to Bolivia — paramount in the midst of the Bolivian Gas War, which finally led to the election of Evo Morales in December 2005, who has approached Venezuelian leader Hugo Chávez, qualified by the US State Department as a "factor of instability" in the region — as well as its location near the Triple Frontier and the Guarani aquifer <ref> U.S. Military Moves in Paraguay Rattle Regional Relations, International Relations Center, December 14, 2005, April 2006, url=http://americas.irc-online.org/am/2991 </ref> <ref name="Clarin"> US Marines put a foot in Paraguay, El Clarín, September 9, 2005 </ref>.

See also

• Dehydration (hypohydration) vs. hyperhydration
• Desalination
• Distilled water
• Drinking water
• Fresh water
• Heavy water
• Ice
• Irrigation
• Mineral water
• Rain
• Safe water
• Sea water
• Spring water
• Water cycle
• Water industry
• Water intoxication
• Water purification
• Water quality
• Water therapy

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. Island Press, Washington, D.C. (published every two years, beginning in 1998.)

Notes

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External links

• Water Conserve - Water Conservation Portal
• UNESCO's World Water Assessment Program
• UNESCO Water Portal
• UNESCO-IHE Institute for Water Education
• European Water Association.
• Whose right to water Schools resource on water rights
• United Nations' World Water Development Report
• United Nations GEMS/Water Programme
• The World's Water, data, historical information on conflict
• Phase diagrams of water
• Oceans and Water Issues Page
• Scientific Facts on Water Disinfectants A faithful summary by GreenFacts of a leading scientific consensus report on Drinking Water Disinfectants published by the International Programme on Chemical Safety of the WHO.
• World Water Forum
• Water Structure and Behaviour
• WaterAid
• SAHRA—Global Water Newswatch
• Stockholm International Water Institute (SIWI)
• California Water Impact Network (C-WIN)
• BBC: The water debate
• BBC News (International): The Water Debate
• E the Environmental Magazine piece on bottled water (Oct 2003).
• International Association for the Properties of Water and Steam
• US Geological Survey: Comprehensive discussion of the water cycle, in many languages
• Why is water blue?
• Water, scientific data (by London South Bank University)
• Water requirements in adults
• Climate change raises markets for environmental technology, drinking water and clean energies
• 'Unfreezable water', bound water and water of hydration
• Wikipedia