Earth is called the blue planet: oceans cover about 71% of its surface. Water is part of the hydrosphere, and almost all of it is salty. The fresh water that people, plants and land animals use is a small slice, and most of that slice is locked away.
| Where the water is | Share of all water | Share of fresh water |
|---|---|---|
| Oceans (salt water) | about 96.5% | — |
| Ice caps and glaciers | about 1.7% | about 69% |
| Groundwater | about 1.7% (about half of it salty) | about 30% |
| Lakes, rivers, swamps, soil, air and living things | well under 1% | about 1% |
Key idea
About 97% of Earth's water is salt water, nearly all in the oceans. Of the small share that is fresh, about two-thirds is frozen in ice and nearly one-third is underground; lakes and rivers hold only a tiny part.
Why it works
Imagine all of Earth's water as 1,000 liters. Using percents, the fresh water is 2.5% of it: 25 L. Of that, 69% is ice ($25 \times 0.69 \approx 17$ L) and 30% is groundwater (about 7.5 L). All the lakes and rivers together are only about 0.27% of the fresh water: about 70 mL, less than half a cup.
Worked example: A model of the water
In a model where all of Earth's water is 2,000 L, about 2.5% is fresh. How many liters is that, and about how much of it is ice (69%)?
- Fresh water: $2{,}000 \times 0.025 = 50$ L.
- Ice: $50 \times 0.69 = 34.5$ L.
Answer: 50 L fresh, about 34.5 L of it ice
Worked example: Where is most fresh water?
Is most of Earth's fresh water in lakes and rivers?
- Ice holds about 69% and groundwater about 30%: together about 99%.
- Lakes and rivers hold well under 1% of the fresh water.
Answer: No: it is mostly ice and groundwater
Common mistake
Thinking most fresh water is in lakes and rivers, because that is the water we see. They hold well under 1% of it. Most fresh water is frozen in ice sheets and glaciers or hidden underground. Check: add the ice (69%) and groundwater (30%) shares, and almost nothing is left over.