A surfer inside a breaking wave as spray lifts off its crest

A field guide to Earth's water

Every drop on Earth, followed from sky to sea.

The planet holds 1.386 billion cubic kilometres of water. It has all been here for billions of years — moving between ocean, ice, river and air.

See where it is How long it stays

Rows of green breakers rolling toward a beach under a deep blue sky

02 Ocean

The ocean is the planet's heat store.

Surface covered: 71%
Average depth: 3.7 km
Extra heat absorbed since 1971: >90%

A swimmer stands at the shoreline as a wave breaks white in front of him

It covers 71% of the surface at an average depth of about 3,700 metres.

Since 1971 it has taken up more than 90% of the extra heat trapped by greenhouse gases — a buffer that is now warming the water itself.

03 Ice

Ice holds two-thirds of the fresh water.

Glaciers and ice sheets lock away 68.7% of Earth's fresh water. If Greenland's ice melted, seas would rise about 7 metres. Antarctica holds enough for 58.

A blue crevasse carved by meltwater into the Athabasca Glacier

Flat-topped mountains rising out of the Greenland ice sheet

Greenland, sea-level rise if melted: 7.4 m
Antarctica, sea-level rise if melted: 58 m
Fresh water held as ice: 68.7%

04 Rivers & lakes

Rivers and lakes are the 1.2% we see.

Every river, lake and swamp together holds just over one percent of the fresh water. Yet this thin, fast-moving share feeds most of our cities, farms and power plants.

Montmorency Falls pouring white water into a wide river basin — i. Montmorency Falls, 83 m — higher than Niagara.

The braided channels of the Macaulay River seen from a small plane — ii. The braided Macaulay River from the air.

1.2%

of fresh water is in lakes, rivers, soil and air. It moves fastest — a river renews itself in months.

A snow-capped peak reflected in a still mountain lake at dusk — iii. A mountain lake at dusk, holding last winter's snow.

Next How long does it stay?

05 Time

A drop's stay ranges from nine days to 20,000 years.

Average time a water molecule spends in each place before it moves on. The scale is logarithmic — each step is ten times longer.

Atmosphere9 days
Soil moisture1–2 months
Rivers2–6 months
Lakes50–100 years
Shallow groundwater100–200 years
Ocean3,200 years
Deep groundwater10,000 years
Antarctic ice20,000 years

06 Up close

One drop of water holds 1.7 sextillion molecules.

Water is strange. It is densest at 4 °C, so lakes freeze from the top down. Its ice is 9% lighter than its liquid, so it floats. Without those two quirks, life under winter ice could not survive.

1,700,000,000,000,000,000,000

A single drop of water clinging to a green leaf beneath its stems — 4 °C — densest point

A droplet rebounding from a ring of ripples in black and white — Surface tension, 72 mN/m

Two divers silhouetted against sunlight above a reef — Ice floats — 9% lighter

07 Access

2.2 billion people

still had no safely managed drinking water at home in 2022.

The water is not missing — it is unevenly placed, unevenly piped and unevenly clean. Protecting rivers, aquifers and ice is how the next drop stays drinkable.

Back to the surface Read the WHO/UNICEF data

People without safe drinking water at home: 1 in 4
Without safely managed sanitation: 3.5 bn
Still drinking straight from rivers, lakes and ponds: 115 m