A loop with no end
Where Does Water Go?
Earth's water has been going round the same loop for billions of years.
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Step 1 of 5
Earth never gains or loses water.
The water here now is the water that has always been here. It changes form and location, but essentially none escapes and none arrives.
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Step 2 of 5
Sun lifts it into the air.
Warmth gives surface water molecules enough energy to break free as vapour. Oceans supply about 86 percent of it; plants and soil supply the rest.
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Step 3 of 5
Cooling turns it back into droplets.
High up it is cold, so vapour condenses onto dust into cloud droplets. That is condensation — evaporation running backwards.
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Step 4 of 5
It falls, and then it travels.
Rain and snow land, then run into streams, soak into the ground, or freeze into glaciers. Every route eventually leads back to the sea.
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Step 5 of 5
Some water takes a very long detour.
A molecule may spend nine days in the air, but two thousand years in the deep ocean or a hundred thousand in an ice sheet.
Water you drink today has almost certainly been inside a dinosaur at some point.
The short version
Water endlessly loops from sea to sky to land and back — the same water, never new.
Try it yourself
Put a bowl of water in a sealed clear bag on a sunny sill. Watch it evaporate, condense on the bag and rain back down.
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