Definition · Plain-language
Water cycle
The water cycle is the continuous journey of water as it moves between the oceans, atmosphere and land, changing between liquid, vapour and ice.
The step most authors miss
Doing CRediT right? Don’t stop at the statement.
A CRediT statement credits you inside one paper. The recognition CRediT was built for happens when those roles are tied to you, persistently. Sign in with your ORCID — free — and claim your CRediT contributions on casrai.org, the home of the standard. They become a verified, portable part of your identity, not a line that disappears into one PDF.
Free: claim your contributions, then export a journal-ready CRediT statement, schema.org structured data, JATS XML, CSV or BibTeX — and preview your public profile. A membership publishes that profile publicly and verifies the journals you serve.
Water on the move
The water cycle, also called the hydrological cycle, describes how Earth’s water continuously circulates between the sea, the sky and the land. The same water is used over and over: the total amount on the planet stays roughly constant, but it is forever changing form and location. The cycle is driven by two forces — energy from the Sun, which lifts water into the air, and gravity, which pulls it back down and moves it across and through the ground. Because it loops endlessly, the water cycle has no true start or finish.
The main stages
The cycle is usually described in four linked stages. In evaporation, the Sun’s heat turns surface water from oceans, lakes and rivers into water vapour that rises into the air; plants add vapour through transpiration. In condensation, the rising vapour cools and turns into the tiny droplets and ice crystals that form clouds. In precipitation, those droplets grow heavy and fall as rain, snow, sleet or hail. In collection, the fallen water gathers — running off into rivers and back to the sea, soaking into the ground as groundwater, or being stored in ice and snow — before evaporating again.
Why it matters
The water cycle is essential to life and to the planet’s climate. It is the natural system that delivers fresh water to the land, filling rivers, lakes and aquifers that plants, animals and people depend on, while constantly purifying water as evaporation leaves salts and many impurities behind. The cycle also moves vast amounts of heat around the globe and shapes the weather, since the energy involved in evaporation and condensation powers storms and rainfall. Changes to the cycle — through a warming climate, deforestation or heavy water use — can shift rainfall patterns and intensify droughts and floods.
Key facts
At a glance
- Definition: the continuous movement of water between ocean, air and land
- Also called: the hydrological cycle
- Main stages: evaporation, condensation, precipitation, collection
- Powered by: energy from the Sun and the pull of gravity
- Key feature: recycles a fixed amount of water, with no start or end
- Why it matters: supplies fresh water and helps drive weather and climate
Common misconceptions
What people often get wrong
Often heard: The water cycle is constantly making new water.
Actually: No new water is created. The cycle recycles the same fixed supply of water over and over, simply changing its form between liquid, vapour and ice and moving it around the planet.
Often heard: The water cycle has a clear beginning and an end.
Actually: It is a continuous loop with no real start or finish. Water can enter any stage at any time, so any point — evaporation, say — is only a convenient place to begin describing it.
Often heard: Only the oceans take part in the water cycle.
Actually: Water also evaporates from lakes, rivers, soil and plants, falls as precipitation on land, flows in rivers, and soaks underground. The whole planet — sea, sky and land — is involved.
