Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state (water v***r 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 i
n aquifers and 0.001% in the air as v***r, 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 ev***ration or transpiration (evapotranspiration), precipitation, and runoff, usually reaching the sea. Over land, ev***ration 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 freshwater is consumed by agriculture. WIKIPEDIA
http://en.wikipedia.org/wiki/Water
