Guides
Earth's water
Evidence-led explainers on earth's water, with every figure sourced.
Where is Earth’s water?
Earth holds about 1.386 billion cubic kilometres of water. Only 2.5% is fresh, most of that is frozen, and the liquid fresh water at the surface is a rounding error on the total.
Why is the sea salty?
Rivers deliver dissolved minerals to the ocean continuously. Evaporation removes the water and leaves the minerals behind. Over hundreds of millions of years, that one-way filter is enough.
Oceans and seawater
96.5% of Earth’s water is in the oceans. Its salinity, circulation and chemistry set the conditions everything else operates within.