Editing Water (section)

===Water cycle===
{{Main|Water cycle}}
[[File:Water cycle.png|thumb|Water cycle]]

The water cycle (known scientifically as the hydrologic cycle) is the continuous exchange of water within the [[hydrosphere]], between the [[Earth atmosphere|atmosphere]], [[soil]] water, [[surface water]], groundwater, and plants.

Water moves perpetually through each of these regions in the ''water cycle'' consisting of the following transfer processes:
* [[evaporation]] from oceans and other water bodies into the air and [[transpiration]] from land plants and animals into the air.
* [[precipitation (meteorology)|precipitation]], from water vapor condensing from the air and falling to the earth or ocean.
* [[runoff (water)|runoff]] from the land usually reaching the sea.
Most water vapors found mostly in the ocean returns to it, but winds carry water vapor over land at the same rate as runoff into the sea, about 47&nbsp;[[Metric tonne unit|Tt]] per year while evaporation and transpiration happening in land masses also contribute another 72&nbsp;Tt per year. Precipitation, at a rate of 119 Tt per year over land, has several forms: most commonly rain, snow, and [[hail]], with some contribution from [[fog]] and [[dew]].<ref>{{cite book |title=Water in Crisis: A Guide to the World's Freshwater Resources |editor-last=Gleick |editor-first=P. H. |publisher=Oxford University Press |year=1993 |page=15, Table 2.3 |url=http://www.oup.com/us/catalog/general/subject/EarthSciences/Oceanography/?view=usa&ci=9780195076288 |url-status=dead |archive-url=https://web.archive.org/web/20130408091921/http://www.oup.com/us/catalog/general/subject/EarthSciences/Oceanography/?view=usa&ci=9780195076288 |archive-date=8 April 2013}}</ref> Dew is small drops of water that are condensed when a high density of water vapor meets a cool surface. Dew usually forms in the morning when the temperature is the lowest, just before sunrise and when the temperature of the earth's surface starts to increase.<ref>{{cite book |title=Alice's Adventures in Water-land |last1=Ben-Naim |first1=A. |last2=Ben-Naim |first2=R. |publisher=World Scientific Publishing |year=2011 |page=31 |doi=10.1142/8068 |isbn=978-981-4338-96-7}}</ref> Condensed water in the air may also [[refract]] [[sunlight]] to produce [[rainbow]]s.

Water runoff often collects over [[Drainage basin|watersheds]] flowing into rivers. Through [[erosion]], runoff shapes the environment creating river [[valley]]s and [[river delta|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 which occurs when a river overflows its banks or a storm surge happens. On the other hand, 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 either due to its topography or due to its location in terms of [[latitude]].