Water the ultimate resource

Water is a chemical substance with the chemical formula H2O. Its molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water vapor or steam). Water also exists in a liquid crystal state near hydrophilic surfaces.

Water covers 70.9% of the Earth's surface and is vital for all known forms of life. On Earth, it is found 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. Oceans hold 97% of surface water, glaciers and polar ice caps 2.4%, and other land surface water such as rivers, lakes and ponds 0.6%. A very small amount of the Earth's water is contained within biological bodies and manufactured products.

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

Clean drinking water is essential to humans and other lifeforms. Access to safe drinking water has improved steadily and substantially over the last decades in almost every part of the world. There is a clear correlation between access to safe water and GDP per capita. However, some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability. A recent report (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, as it functions as a solvent for a wide variety of chemical substances and facilitates industrial cooling and transportation. Approximately 70% of the fresh water which is actively handled by humans, is consumed by agriculture.

Taste and odor

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

Distribution in nature

In the universe
Much of the universe's water is 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 observed is quickly produced in this warm dense gas.

On 22 July 2011, a report described the discovery of a gigantic cloud of water vapor, containing "140 trillion times more water than all of Earth's oceans combined," around a quasar located 12 billion light years from Earth. According to the researchers, the "discovery shows that water has been prevalent in the universe for nearly its entire existence."

Water has been detected in interstellar clouds within our galaxy, the Milky Way. Water probably 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 present in

  • Atmosphere of Mercury: 3.4%, and large amounts of water in Mercury's exosphere[21]
  • Atmosphere of Venus: 0.002%
  • Earth's atmosphere: ~0.40% over full atmosphere, typically 1–4% at surface
  • Atmosphere of Mars: 0.03%
  • Atmosphere of Jupiter: 0.0004%
  • Atmosphere of Saturn – in ices only
  • Enceladus (moon of Saturn): 91%
  • exoplanets known as HD 189733 b[22] and HD 209458 b.[23]

Liquid water is present on

  • Earth: 71% of surface
  • Europa: 100km deep subsurface ocean

Strong evidence suggests that liquid water is present just under the surface of Saturn's moon Enceladus.

Water ice is present on

  • Earth – mainly as ice sheets
  • polar ice caps on Mars
  • Moon
  • Titan
  • Europa
  • Saturn's rings[24]
  • Enceladus
  • Pluto and Charon[24]
  • Comets and comet source populations (Kuiper belt and Oort cloud objects).

Water ice may be present on Ceres and Tethys. Water and other volatiles probably comprise much of the internal structures of Uranus and Neptune and the water in the deeper layers may be in the form of ionic water in which the molecules break down into a soup of hydrogen and oxygen ions, and deeper down as superionic water in which the oxygen crystallises but the hydrogen ions float around freely within the oxygen lattice.[12]

Some of the Moon's minerals contain water molecules. For instance, in 2008 a laboratory device which ejects and identifies particles found small amounts of the compound in the inside of volcanic pearls brought from Moon to Earth by the Apollo 15 crew in 1971.[25] NASA reported the detection of water molecules by NASA's Moon Mineralogy Mapper aboard the Indian Space Research Organization's Chandrayaan-1 spacecraft in September 2009.[26]

On Earth

Water covers 71% of the Earth's surface; the oceans contain 97.2% of the Earth's water. The Antarctic ice sheet, which contains 61% 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 the hydrosphere. Earth's approximate water volume (the total water supply of the world) is 1,360,000,000 km3 (326,000,000 mi3).

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 states. It also exists as groundwater in aquifers.

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

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. 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. 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.

Liquid water and ice structures

  • according to state
    • solid – ice
    • liquid – water
    • gaseous – water vapor
    • plasma
  • according to meteorology:
    • hydrometeor
      • precipitation

precipitation according to movement

  • 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

precipitation according to state

  • liquid precipitation
    • snow
    • snow pellets
    • snow grains
    • ice pellets
    • frozen rain
    • hail
    • ice crystals
    • hoarfrost
    • atmospheric icing
    • glaze ice
  • solid precipitation
    • dew
    • hoarfrost
    • atmospheric icing
    • glaze ice
  • mixed precipitation
    • in temperatures around 0 °C
    • levitating particles
      • clouds
      • fog
      • mist
    • ascending particles (drifted by wind)
      • spindrift
      • stirred snow
  • according to occurrence
    • groundwater
    • meltwater
    • meteoric water
    • connate water
    • fresh water
    • surface water
    • mineral water – contains many minerals
    • brackish water
    • dead water – strange phenomenon which can occur when a layer of fresh or brackish water rests on top of denser salt water, without the two layers mixing. It is dangerous for ship traveling.
    • seawater
    • brine
  • according to uses
    • tap water
    • bottled water
    • drinking water or potable water – useful for everyday drinking, without fouling, it contains balanced minerals that are not harmful to health (see below)
    • purified water, laboratory-grade, analytical-grade or reagent-grade water – water which has been highly purified for specific uses in science or engineering. Often broadly classified as Type I, Type II, or Type III, this category of water includes, but is not limited to, the following:
      • distilled water
      • double distilled water
      • deionized water
      • Reverse osmosis plant Water
  • • according to other features
    • soft water – contains fewer minerals
    • hard water – from underground, contains more minerals
    • distilled water, double distilled water, deionized water – contains no minerals
    • water of crystallization — water incorporated into crystalline structures
    • hydrates — water bound into other chemical substances
    • heavy water – made from heavy atoms of hydrogen – deuterium. It is in nature in normal water in very low concentration. It was used in construction of first nuclear reactors.
    • tritiated water
  • • according to microbiology
    • drinking water
    • wastewater
    • stormwater or surface water
  • according to religion
    • holy water

The final word to say is Save Water Save Earth.