Hydrological cycle; water on Earth's surface, components and processes of water cycle

Oceans are large depressions or basins on the surface of earth containing saline water and covers 71% of the earth’s surface and about 97% of earth’s water. Some of the major oceans of the world are, Pacific Ocean, Atlantic Ocean, Indian ocean, Arctic Ocean and Southern Ocean or Antarctic Ocean. Water is an essential component of all life forms that exist over the surface of earth. Water is a rare commodity in our solar system. The earth fortunately has an abundant supply of water on its surface. Hence, our planet is called the ‘Blue Planet’.

HYDROLOGICAL CYCLE

Water cycle, also called hydrological cycle, involves the continuous circulation of water in the Earth – atmosphere system. Of the many processes involved in the water cycle, the most important are evaporation, transpiration, condensation, precipitation, and runoff.

WATER OF EARTH’S SURFACE

Reservoir	Volume (Million Cubic km)	Percentage of the Total
Oceans	1,370	97.25
Ice Caps and Glaciers	29	2.05
Groundwater	9.5	0.68
Lakes	0.125	0.01
Soil Moisture	0.065	0.005
Atmosphere	0.013	0.001
Streams and Rivers	0.0017	0.0001
Biosphere	0.0006	0.00004

COMPONENTS AND PROCESSES OF THE WATER CYCLE

Components	Processes
Water storage in oceans	Evaporation, Evapotranspiration, Sublimation
Water in the atmosphere	Condensation, Precipitation
Water storage in ice and snow	Snowmelt runoff to streams
Surface runoff	Stream flow, freshwater storage, infiltration
Groundwater storage	Groundwater discharge springs