Water or Hydrologic Cycle

The quantity of water on earth is fixed, if we consider it on a 100 year scale or so. It's around 1.386 billion cubic km. The distribution is as follows :

This water is constantly in motion. It loops endlessly between ocean, atmosphere and land. Also it changes form, from gas to liquid to solid.The energy driving this is solar and earth's gravity.

Major Components of Water Cycle


Sunlight heats the water which evaporates and rise as vapour to the atmosphere.


Transpiration is the evaporation of water from the leaves of the plants.


The evaporated or transpired water vapour cools as it rises in the atmosphere. The cooled vapour again becomes liquid or ice and settles on the dust particles present in the atmosphere. This is called condensation. This forms the cloud.



Runoff can be described as the part of the water cycle that flows over land as surface water instead of being absorbed into groundwater or evaporating


Percolation is the seepage of water through cracks, joints and pores in soil and rocks until it reaches the water table where it becomes groundwater.

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