MEPX
Chapter 5 of 10All chapters
  1. 1Inside the Earth
  2. 2Plate tectonics
  3. 3Rocks and minerals
  4. 4Shaping the surface
  5. 5Water on Earth
  6. 6Earthquakes
  7. 7Volcanoes
  8. 8The atmosphere
  9. 9Geological time
  10. 10Resources and hazards

Chapter 5 of 10

Water on Earth

The cycle and where it is stored.

The cycle

Solar energy evaporates water, it condenses into cloud, falls as precipitation and flows back to the sea. The same water has been through this cycle for billions of years.

  • Over 97 percent of Earth water is salt water in oceans.
  • Most fresh water is locked in ice caps and groundwater, not rivers.

Groundwater

Water held in porous rock supplies much of the world's drinking and irrigation. Aquifers refill slowly, so extraction can outrun replacement for decades before the problem is visible.