Portal:Water

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Water

Water in two states: liquid (including the clouds, which are examples of aerosols), and solid (ice).

Water is a transparent, tasteless, odorless, and nearly colorless chemical substance that is the main constituent of Earth's streams, lakes, and oceans, and the fluids of most living organisms. Its chemical formula is H2O, meaning that each of its molecules contains one oxygen and two hydrogen atoms that are connected by covalent bonds. Strictly speaking, water refers to the liquid state of a substance that prevails at standard ambient temperature and pressure; but it often refers also to its solid state (ice) or its gaseous state (steam or water vapor). It also occurs in nature as snow, glaciers, ice packs and icebergs, clouds, fog, dew, aquifers, and atmospheric humidity.

Water covers 71% of the Earth's surface. It is vital for all known forms of life. On Earth, 96.5% of the planet's crust water is found in seas and oceans, 1.7% in groundwater, 1.7% in glaciers and the ice caps of Antarctica and Greenland, a small fraction in other large water bodies, and 0.001% in the air as vapor, clouds (formed of ice and liquid water suspended in air), and precipitation. Only 2.5% of this water is freshwater, and 98.8% of that water is in ice (excepting ice in clouds) and groundwater. Less than 0.3% of all freshwater is in rivers, lakes, and the atmosphere, and an even smaller amount of the Earth's freshwater (0.003%) is contained within biological bodies and manufactured products. A greater quantity of water is found in the earth's interior.

Water on Earth moves continually through the water cycle of evaporation and transpiration (evapotranspiration), condensation, precipitation, and runoff, usually reaching the sea. Evaporation and transpiration contribute to the precipitation over land. Large amounts of water are also chemically combined or adsorbed in hydrated minerals.

Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients. Access to safe drinking water has improved over the last decades in almost every part of the world, but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A report, issued in November 2009, suggests that by 2030, in some developing regions of the world, water demand will exceed supply by 50%.

Water plays an important role in the world economy. Approximately 70% of the freshwater used by humans goes to agriculture. Fishing in salt and fresh water bodies is a major source of food for many parts of the world. Much of long-distance trade of commodities (such as oil and natural gas) and manufactured products is transported by boats through seas, rivers, lakes, and canals. Large quantities of water, ice, and steam are used for cooling and heating, in industry and homes. Water is an excellent solvent for a wide variety of chemical substances; as such it is widely used in industrial processes, and in cooking and washing. Water is also central to many sports and other forms of entertainment, such as swimming, pleasure boating, boat racing, surfing, sport fishing, and diving.

Featured article

Clear water pours from a spout into a drinking glass.
Fluoridation does not affect the appearance, taste or smell of drinking water.

Water fluoridation is the controlled addition of fluoride to a public water supply to reduce tooth decay. Fluoridated water contains fluoride at a level that is effective for preventing cavities; this can occur naturally or by adding fluoride. Fluoridated water operates on tooth surfaces: in the mouth, it creates low levels of fluoride in saliva, which reduces the rate at which tooth enamel demineralizes and increases the rate at which it remineralizes in the early stages of cavities. Typically a fluoridated compound is added to drinking water, a process that in the U.S. costs an average of about $1.06 per person-year.[1] Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. In 2011 the World Health Organization suggested a level of fluoride from 0.5 to 1.5 mg/L (milligrams per litre), depending on climate, local environment, and other sources of fluoride. Bottled water typically has unknown fluoride levels.


Dental caries remains a major public health concern in most industrialized countries, affecting 60–90% of schoolchildren and the vast majority of adults. Water fluoridation reduces cavities in children, while efficacy in adults is less clear. A Cochrane review estimates a reduction in cavities when water fluoridation was used by children who had no access to other sources of fluoride to be 35% in baby teeth and 26% in permanent teeth. The evidence quality was poor. Most European countries have experienced substantial declines in tooth decay without its use, however milk and salt fluoridation is widespread. Recent studies suggest that water fluoridation, particularly in industrialized nations, may be unnecessary because topical fluorides (such as in toothpaste) are widely used, and caries rates have become low.


Although fluoridation can cause dental fluorosis, which can alter the appearance of developing teeth or enamel fluorosis, the differences are mild and usually not considered to be of aesthetic or public health concern. There is no clear evidence of other adverse effects from water fluoridation. Fluoride's effects depend on the total daily intake of fluoride from all sources. Drinking water is typically the largest source; other methods of fluoride therapy include fluoridation of toothpaste, salt, and milk. The views on the most efficient method for community prevention of tooth decay are mixed. The Australian government states that water fluoridation is the most effective way to achieve fluoride exposure that is community-wide. The World Health Organization reports that water fluoridation, when feasible and culturally acceptable, has substantial advantages, especially for subgroups at high risk, while the European Commission finds no benefit to water fluoridation compared with topical use.


Public water fluoridation was first practiced in the U.S. As of 2012, 25 countries have artificial water fluoridation to varying degrees, 11 of them have more than 50% of their population drinking fluoridated water. A further 28 countries have water that is naturally fluoridated, though in many of them the fluoride is above the optimal level. As of 2012, about 435 million people worldwide received water fluoridated at the recommended level (i.e., about 5.4% of the global population). About 214 million of them living in the United States. Major health organizations such as the World Health Organization and FDI World Dental Federation supported water fluoridation as safe and effective. The Centers for Disease Control and Prevention lists water fluoridation as one of the ten great public health achievements of the 20th century in the U.S. Despite this, the practice is controversial as a public health measure. Some countries and communities have discontinued fluoridation, while others have expanded it. Opponents of the practice argue that neither the benefits nor the risks have been studied adequately, and debate the conflict between what might be considered mass medication and individual liberties. Read more...

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Water cycle.png

Did you know...

DYK Question Mark

... that the International Water Management Institute celebrated its 25th anniversary last year?

... that the International Water Centre celebrated its 5th birthday last year?

... that the National Rural Water Association represents more than 26,242 water and wastewater utility members?

... that "water bears" are small, segmented animals that can survive in a dehydrated state for nearly 10 years?

... that there are at least 15 different forms of crystalline ice?

... that water memory is a controversial homeopathic concept, which holds that water is capable of containing "memory" of particles dissolved in it?

... that there are more particles in a glass of water than grains of sand on earth?

... that there is a new definition for Earth's water cycle that includes the three "interactive" cycles: cosmic water cycle; atmospheric water cycle, and oceanic water cycle (new ocean recycled from center of Earth about every 7 million years) The Water Channel TV

Water Rights

  • "The Arizona Court of Appeals recently upheld a decision that the Arizona Department of Water Resources has the right to issue instream flow permits and affirmed the principle that instream flow and in situ water rights need not be diversionary." [1]

Photo gallery

  • UNESCO World Water Assessment Programme photo library
  • The UK Collection of Freshwater Sites
  • HyDis - Hydrologic Data and Information System GIS maps
  • Water Science Picture Gallery from U.S. Geological Survey
  • FAO Water Multimedia Gallery featuring animations and videos

Water News

  • The World Water Assessment Programme monitors freshwater issues and provides recommendations
  • The Source Water and Sanitation News Service provides news in English, French and Spanish with an emphasis on rural and peri-urban areas in developing countries
  • UNESCO Water Portal and weekly newsletter
  • Dundee UNESCO Centre a portal for Water Law, Policy and Science from the University of Dundee
  • Water Planning Tools - news, reviews and updates for water planners and managers, Australia
  • [2] - [The Water Network - knowledge platform for the Water professionals to connect share knowledge.Switzerland
  • Global Water News Watch, from SAHRA in Arizona USA
  • U.S. Water Monitor - a portal to federal water information
  • Watershed News from U.S. Environmental Protection Agency
  • USDA Soil Conservation Service website news
  • National Rural Water Association NRWA news and press releases
  • The 2005 Preliminary Report of the Sustainable Water Resources Roundtable (SWRR) is now available.
  • India Water Portal Community-contributed water resources, articles, news, Q&A, data, events, opportunities, photos and videos.
  • Alberta WaterPortal Water news, info, events, and community.

Things you can do


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  • Expand : water footprint
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  • Other : * Invite water experts to contribute their information.
    • Add your expert knowledge for your local river at WikiProject Rivers.
    • Help rotate/refresh the three items in the "Did you know?" box.
    • Expand articles on local lakes at WikiProject Lakes
    • Write or improve an article on a country whose water sector you know well at Category:Water supply and sanitation by country

Categories

Wikiprojects

  • WikiProject Lakes describes the Earth's lakes. The project aims to consolidate and unify pages relating to lakes around the world.

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  1. ^ Federal Reserve Bank of Minneapolis Community Development Project. "Consumer Price Index (estimate) 1800–". Federal Reserve Bank of Minneapolis. Retrieved January 2, 2018. 
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