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How does the water cycle work?

Rain at Ocean Beach, San FranciscoRain at Ocean Beach, San FranciscoThe oceans hold about 97% of the world’s water. Water evaporated from the oceans may be carried as water vapour across land. As it rises above high ground, it condenses and falls to the ground as rain or snow. Rivers carry the water on the land’s surface back to the ocean and the cycle begins again. Much of the water evaporated from the oceans falls directly back into the oceans. This never-ending cycle of water moving between the ocean and atmosphere is called the water cycle.

 

A block diagram showing the water cycleA block diagram showing the water cycle

Evaporation and condensation

When water from oceans, rivers or lakes is heated by the Sun, it evaporates: it turns into an invisible gas called water vapour. This rises into the air and is blown by winds. As the air rises, it cools and starts to condense (turn back into a liquid) around tiny dust particles in the air. Millions of water droplets gather together to form clouds.


Groundwater flooding to the surfaceGroundwater flooding to the surface

Groundwater

Rain that falls anywhere except the tropics usually falls from the clouds as snow. It turns to rain as it melts in the warmer air below.

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