The water cycle

The water cycleis also known as the hydrological cycle.

Seas and oceans contain 97% of the world's water, and ice holds 2%.

That leaves just 1% of the world's water as fresh water on land or in the air.

This water is recycled again and again through the process of evaporation, condensation and water transfers such as surface runoff.

Illustration showing the cycle of the drainage basinKey stages of the water cycle

Key terms:

  • Infiltration - Water soaks or filters into the soil.
  • Surface runoff - Water moves across the surface of the earth becoming a stream, tributary or river.
  • Precipitation - An input where water is introduced to the drainage basin system.
  • Evapotranspiration - Water vapour is evaporated from the trunk and leaves of trees and other vegetation, back into the atmosphere.
  • Throughflow - Water moves downhill through the soil.
  • Groundwater flow - Water moving slowly through the soil and porous rocks to move back towards the sea.
  • Percolation - Water moving from the soil into the spaces (pores) in the rock.