Water Cycle

The water cycle, also known as the hydrological cycle or H2O cycle, describes the continuous movement of water on, above and below the surface of the Earth. Although the balance of water on Earth remains fairly constant over time, individual water molecules can come and go, in and out of the atmosphere. The water moves from one reservoir to another, such as from river to ocean, or from the ocean to the atmosphere, by the physical processes of evaporation, condensation, precipitation, infiltration, runoff, and subsurface flow. In so doing, the water goes through different phases: liquid, solid (ice), and gas (vapor).

The water cycle involves the exchange of heat, which leads to temperature changes. For instance, when water evaporates, it takes up energy from its surroundings and cools the environment. When it condenses, it releases energy and warms the environment. These heat exchanges influence climate. By transferring water from one reservoir to another, the water cycle purifies water, replenishes the land with freshwater, and transports minerals to different parts of the globe. It is also involved in reshaping the geological features of the Earth, through such processes as erosion and sedimentation. Finally, the water cycle figures significantly in the maintenance of life and ecosystems on Earth.


As the Earth's surface water evaporates, winds move water in the air from the sea to the land, increasing the amount of fresh water on land. Water vapor is converted to clouds that bring fresh water to land in the form of rain or snow. Precipitation falls on the ground, but what happens to that water depends greatly on the geography of the land at any particular place.


Read more about Water CycleDescription, Residence Times, Changes Over Time, Effects On Climate, Effects On Biogeochemical Cycling, Slow Loss Over Geologic Time

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Groundwater - Water Cycle
... Groundwater makes up about twenty percent of the world's fresh water supply, which is about 0.61% of the entire world's water, including oceans and permanent ice ... resource which can act as a natural storage that can buffer against shortages of surface water, as in during times of drought ... Groundwater is naturally replenished by surface water from precipitation, streams, and rivers when this recharge reaches the water table ...
Natural Environment - Biogeochemical Cycles
... Global biogeochemical cycles are critical to life, most notably those of water, oxygen, carbon, nitrogen and phosphorus ... The nitrogen cycle is the transformation of nitrogen and nitrogen-containing compounds in nature ... It is a cycle which includes gaseous components ...
Abiogenesis - Current Models - Origin of Organic Molecules - Ultraviolet and Temperature-assisted Replication Model
... the entropy production of Earth by catalysing the water cycle through evapotranspiration ... of life today is to produce entropy through coupling with the water cycle, then this probably was its function at its very beginnings ... It turns out that both RNA and DNA when in water solution are very strong absorbers and extremely rapid dissipaters of ultraviolet light within the 200–300 nm wavelength range ...

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