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Water Cycle


WATER CYCLE


  • Water cycle is defined as a constant interaction between biotic and abiotic components to maintain the level of different forms of water in the environment to support life.
  • Or, it can also be defined as a series of processes in which water evaporates and falls on the land as rain and later flows back into the sea via rivers. It is also known as hydrological cycle.

 

Occurrence:

  • Water can exist in different states in different regions of our environment.

S.No.

State

Forms

Region

1

liquid

Water

Hydrosphere/ Lithosphere- rivers, seas, oceans, underground water etc.

2

Solid

Snow, ice

Hydrosphere/ Lithosphere- polar regions

3

Gaseous

Water vapors

Atmosphere

  • Living organisms can consume water in liquid form but the other states are also required so as to maintain the level of liquid form on earth. The level is maintained because of various biotic and abiotic processes that can interconvert the water into gaseous and liquid forms.

 

Processes involved in water cycle:

  • Some processes convert the liquid form of water into gaseous and further other different processes converts it back into liquid form.

 

Conversion of water liquid water to gaseous state:

Evaporation:

  • It is defined as a conversion of water into water vapors due to high temperature. During this, sun’s heat warms the water in water bodies like sea, ocean, rivers, streams, lakes, moist soil etc. Due to which it converts into water vapors and rises in the atmosphere.  These vapors tend to move towards the region of low temperature where they condenses and form the clouds.

Respiration:

  • It is defined as a process in which living organisms oxidizes food material and produces CO2 and water in the form of water vapors. Thus this process adds to water vapor content in the environment.

Transpiration:

  • Transpiration is defined as loss of excess of water from the plants through stomata in the environment. This process not only maintains the water vapor level in environment but also helps in keeping the environment cool.

 

Conversion of water vapors to liquid water state:

Condensation:

  • It is a chemical process of conversion of liquid water into solid state under low temperature and high pressure. The vapors present in the environment move towards the region of low temperature where they condenses and forms the clouds.

Precipitation:

  • The clouds are blown in different regions by winds where they fall down on land or water bodies as hail, snow, sleet or rain. Such conversion of condensed water into liquid or solid form of water/ water vapors is known as precipitation. Thus this process brings down the water on land. This water tends to flow in rivers or oceans or different reservoirs. Also some of this water seeps down in soil and maintain the level of underground water. While some maintains the thickness of ice in polar regions.

 

Representative diagram of water cycle:

 

Consumption of water:

  • Living organisms consume for different purposes by animals including human beings and plants.

  • Animals consume it by drinking while human beings need it for various activities like drinking, washing, bathing, irrigation, industrial use etc.
  • For this they obtain water from different sources thus decreasing the level of liquid form on earth which is later maintained by other biotic and abiotic processes.
  • Plants need water for photosynthesis which it obtains by absorption from soil via roots. Therefore decreases the level of underground water.
  • If the over consumption of water occurs it will lead to a imbalance in water cycle and decrease in usable form of water.
  • Thus for maintenance of life balanced water cycle is required in the environment.

 

Fate of water on earth:

  • All of the water that falls on the land does not immediately flow back into the sea.
  • Some of it seeps into the soil and becomes part of the underground reservoir of fresh-water.
  • Some of this underground water finds its way to the surface through springs.
  • It is brought to the surface for our use through wells or tube wells.
  • Water is capable of dissolving a large number of substances. As water flows through or over rocks containing soluble through or over rocks containing soluble minerals, some of them get dissolved in the water.
  • Thus rivers carry many nutrients from the land to the sea, and these are used by the marine organisms.