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Natural Resources

Tutormate > CBSE Syllabus-Class 9th Biology > Natural Resources

7 Water Cycle

  • There is constant cycling of nutrients and materials in an ecosystem between biotic (living) and abiotic (non-living) components.
  • This cycling of minerals in an ecosystem and finally in biosphere is called biogeochemical cycle.
  • The biogeochemical cycles are also known as nutrient cycles.
  • Some of the biochemical cycles are:
    • Water Cycle
    • Nitrogen Cycle
    • Carbon Cycle
    • Oxygen Cycle

Water Cycle:

  • The whole process in which water evaporates and falls on the land as rain and later flows back into the sea via rivers is known as the water-cycle or biogeochemical cycle or hydrological cycle.
  • The Sun could be called as the powerhouse which initiates this process. There is a continuous exchange of moisture from the water bodies, atmosphere, and the land surface.
  • The water cycle is a multi-phase journey in which the water molecules from the earth surface make their way towards the atmosphere and return.

Water Cycle Process:

  • The hydrological cycle repeats itself continuously.
  • Evaporation, sublimation, and transpiration together are responsible for the water vapor present in the atmosphere.
  • Evaporation is a process in which the water changes from liquid phase to gaseous phase.
  • Most of the moisture found in our atmosphere is a result of evaporation that occurs from oceans, seas, lakes, etc.
  • Plants also play a role in releasing the moisture through the process of transpiration.
  • Plants take in water from the ground through their roots and release them into the atmosphere, with the help of small pores present on the leaves.
  • Sublimation of snow also results in the formation of vapor to a certain extent.
  • As water vapors find their way into the lower atmosphere, the air currents raise them up into the higher atmosphere where they undergo condensation which is a process in which matter changes its state from gaseous phase to liquid phase.
  • Due to condensation and the atmospheric conditions, the vapors get converted into a precipitate such as snow, rain, sleet, or hail.
  • Once the precipitate falls on the surface of the earth, it takes various paths.
  • Some of the precipitates get evaporated.
  • Others seep into the ground while some flow into oceans, rivers, and streams.

The water cycle process can also be divided into the following categories:

Global water cycle

  • Water evaporates from oceans, seas, rivers under sun’s heat and forms clouds.
  • Then the clouds fall on Earth as rain after the wind blows the clouds over to the land to cool enough.
  • Some water from rain soaks into the ground but most of it flows in rivers and returns directly to the seas.
  • The ground water comes to surface again with the help of springs and pumps.
  • It is used in agriculture, industry and homes.
  • This water finally evaporates into the atmosphere.

Biological water cycle


  • It is a process where, plants absorb water from the soil or water reservoir and add it to the air in vapour form.
  • Animals take water from the water reservoir or with food (plants or other animals or their products).
  • They return it to the air as vapours by respiration or to the soil as fluid by excretion. Water vapour formed by transpiration and respiration form clouds and enter global water cycle.
  • Rain adds water to soil and reservoir for reuse by plants and animals. This completes the water cycle.

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