Water cycle

Sava river Croatia by Ivica BRLC


Water cycle, or hydrological cycle, is a succession of stages through which water passes from the atmosphere to the Earth and returns to the atmosphere: evaporation from the land or sea or inland water, condensation to form clouds, precipitation, interception, infiltration, percolation, runoff, accumulation in the soil or in bodies of water, and re-evaporation (WMO/UNESCO International Glossary of Hydrology).

The water cycle is an essential component of the climate system, controlling the interaction between the land surface and the atmosphere and providing feedback mechanisms for the transport, storage and exchange of mass and energy. Thus, it is a complex balance of the planet’s water in its various forms and proportions. It is liable to natural variation, as well as changes caused by humans.


WMO (2006). Technical Regulations, Volume III: Hydrology. WMO-No. 49, Basic Documents-No. 2.

WMO (2020). Guide to Hydrological Practices, Volume I: From Measurements to Hydrological Information. WMO-No. 168.