Nature · Earth Science
The endless journey of every drop
The water cycle is the ceaseless movement of water between ocean, sky and land. Powered by the Sun and gravity, the same water has circulated for billions of years — evaporating from the seas, drifting as cloud, falling as rain and snow, and flowing back again — linking every river, glacier and living thing on Earth.
The Sun heats the oceans, turning liquid water into invisible vapour that rises and cools into clouds. That water returns as precipitation, then runs off into rivers, soaks into the ground or freezes into ice — before evaporating once more. Nothing is lost; the same water is used over and over.
Evaporation, condensation, precipitation and runoff link ocean, sky and land in one endless loop.
Water rising into the sky
Solar heat lifts water off oceans, lakes and soil as vapour, while plants add moisture through their leaves. This invisible rise of water into the air begins every trip around the cycle.
Vapour gathering into cloud
As moist air rises and cools, vapour condenses onto tiny particles into the water droplets and ice crystals that make clouds. Clouds are the visible reservoir between sky and rain.
Water falling back to Earth
When cloud droplets merge until they are too heavy to stay aloft, they fall as rain, snow, sleet or hail. Precipitation is how the sky returns its water to land and sea.
Water’s return route
Fallen water either runs off into streams, soaks into the ground to recharge aquifers, or freezes into glaciers and ice caps — some stored for days, some for thousands of years — before evaporating again.