Hydrology cycle of water

Definition of Hydrology:

Water is vital for all living organisms on Earth. For centuries, people have been investigating where water comes from and where it goes, why some of it is salty and some is fresh, why sometimes there is not enough and sometimes too much. All questions and answers related to water have been grouped together into a discipline. The name of the discipline is hydrology and is formed by two Greek words: "hydro" and "logos" meaning "water" and "science". Hydrology is the science concerned with the occurrence, distribution, movement and properties of all the waters of the Earth.

The total amount of water on Earth is invariable. At the same time water is continuously renewed while circulating between oceans, land and atmosphere. All processes like evaporation, condensation, precipitation, interception, transpiration, infiltration, storage, runoff, and groundwater flow which keep water in motion constitute the hydrologic cycle. Those processes are stimulated by solar energy. They take place simultaneously and, except for precipitation, continuously. Consider Figure:

 

o       evaporation, (release of water vapour/steam by a free surface at a temperature below the boiling point. Through evaporation water leaves the land and oceans, rising into atmosphere.)

o       condensation, (The change in water phase, from a vapour state into a liquid state. The condensation is produced by way of air cooling below the dew point and by the deposition of the water vapours on the nucleus of condensation.)

o       precipitation, (Liquid or solid products of the condensation of water vapour falling from clouds or deposited from the air on the ground. For example, rain, sleet, snow, hail.)

o       interception, (The process by which precipitation is caught and held by vegetation (canopy and litter structures) then may be lost by evaporation without reaching the ground.) 

transpiration, (The process by which water from vegetation is transferred into the atmosphere in the form of vapour.) 

 

o     infiltration, (The process of entry of water into a soil through the soil surface.      The part of rainfall that enters the soil)

o       storage, (Volume of water stored.)

o       runoff, (The part of precipitation that flows towards the stream on the ground surface (surface runoff) or within the soil (subsurface runoff). That part of the precipitation appearing in surface streams. The portion of precipitation that, after reaching the ground surface, runs off to a water body.)

o       groundwater flow, (Movement of water in an aquifer. It is considerably slower than surface runoff. Groundwater flows until reaches lakes, rivers or oceans. It can also reach the surface through artesian wells.)