How much water is underground?
About 23,400,000 cubic kilometres — 1.7% of all the water on Earth. That is 11,038 times more water than there is in every river on the planet put together, and it is nearly as much as all the ice.
AI reconstruction — not a photograph · Shutterstock AI/Shutterstock.com · Shutterstock Standard License
Rivers are the rounding error
Every river on Earth — the Amazon, the Nile, the Mississippi, the stream at the bottom of your road — holds about 2,120 cubic kilometres of water between them. Lakes hold 176,400. Underground there is 23,400,000.
Groundwater, fresh and saline together
23,400,000
cubic kilometres
Ice caps, glaciers and permanent snow
24,064,000
cubic kilometres
Lakes, fresh and saline
176,400
cubic kilometres
Groundwater is 97% of the volume held in all the ice caps, glaciers and permanent snow on Earth. Almost the same amount of water is sitting in the ground beneath you as is frozen at the poles — and it is completely invisible.
Real photograph · 301540237/Shutterstock.com · Shutterstock Standard (free image collection, API) License
And more than half of it is salty
This is the part that catches people out. Of that 23,400,000 cubic kilometres, 12,870,000 is saline and only 10,530,000 is fresh. Underground water is not automatically drinkable, and most of the world's is not.
The fresh part still matters enormously: it is 30.1% of all the freshwater on Earth. Almost a third of the planet's usable water is underground rather than on the surface.
Real photograph · 228988681/Shutterstock.com · Shutterstock Standard (free image collection, API) License
Why this site cares
Because it is where the water goes when it is not visible. Rain that soaks in does not leave — it joins the largest store of liquid fresh water on the planet, moves slowly, and comes back out somewhere else, sometimes centuries later. That is how a hot spring works: water percolating deep enough to meet hot rock, then rising again.
It is also part of why the water in your glass can be older than the dinosaurs. Water on the surface is a small, fast-moving fraction of the whole. Most of it is somewhere slower — in ice, in rock, in the deep sea — waiting its turn.
For teachers
For school
- That is 11,038 times more water than there is in every river on the planet put together, and it is nearly as much as all the ice.
- Underground water is not automatically drinkable, and most of the world's is not.
- Rain that soaks in does not leave — it joins the largest store of liquid fresh water on the planet, moves slowly, and comes back out somewhere else, sometimes centuries later.
Classroom prompt
Nobody can see groundwater, yet this page says there is far more of it than in every river. Using the three boxes of figures on the page, put groundwater, ice and lakes in order and explain why the biggest one is the one we notice least.
Extension: the table calls itself “one estimate”. How did this page check it, and why is a check against a separate figure worth more than reading the same table twice?
Ages: the “more than every river” comparison works from about seven; cubic kilometres and the salty-or-fresh split suit pupils of about ten upwards. That range is our teaching choice for this page, not a curriculum claim.
Where this comes from
- The figures
- USGS Water Science School — Where is Earth's Water? (global water distribution table), read . Credit: U.S. Geological Survey. USGS names its own source for the table, and so do we: Igor Shiklomanov’s chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis. Every volume here is in the cubic kilometres the table itself publishes, so no conversion of ours sits between you and the source.
- How sure is this?
- The table calls itself “one estimate” of global water distribution, and that is the right word — nobody has measured the water in the world’s rock directly. We checked it against a separate USGS figure this site already used for the total volume of Earth’s water: the two agree (96.5% of that total is ocean, and the table independently says 96.5%). Reconstructions and estimates are not photographs, and this one is honest about being an estimate.
Where next
Groundwater is the deepest row the famous table counts, and is there water inside Earth? asks what lies below it. Hot springs, volcanoes and the rest of this family are gathered on the volcano water page. Want to check another page? Our evidence guide explains which questions maps, rocks and fossil records can answer.