Water Cycle: Definition, Stages of Water Cycle and Evaporation
Get unlimited access to the best preparation resource for NEET : fully solved questions with step-by-step explanation- practice your way to success.
Definition of Water Cycle
Water Cycle describes the continuous movement of water on above and below the surface of the Earth.
This cycle is also known as the hydrologic cycle or the hydrological cycle.
It involves the exchange of energy leading to temperature changes.
The movement of water i8s from one reservoir to another such as from river to ocean, or from the ocean to the atmosphere.
Physical processes involved are:
Evaporation
Condensation
Precipitation
Infiltration
Surface runoff
Subsurface flow
The Water Cycle
Stages of Water Cycle
Evaporation
This occurs when the water molecules at the surface of the water bodies rise into the air.
The molecules accumulate into water vapour clouds.
When evaporation takes place through the leaves, the process is known as evapotranspiration.
This process usually takes place below the boiling point of water.
Sublimation
This process occurs when snow or ice changes directly into water vapour without becoming water.
This can be observed on mountain peaks (the air pressure is quite low).
The ice sheets covering the poles of the earth are the primary source of sublimation.
The low air pressure helps in sublimation.
Condensation
It is the change of the physical state of matter from the gas phase into the liquid phase.
Wind and air currents move the moisture, which leads to the formation of clouds.
Precipitation
The vapours will condense into water droplets above zero degrees centigrade.
It is the action or process of precipitating a substance from a solution.
The vapours cannot condense in the absence of dust and other impurities.
Infiltration
Rainwater gets absorbed into the ground through this process.
One of the examples is that of rocks which can retain comparatively less water than the soil.
Runoff
The water from the rainfall often flows down the sides of mountains and hills forming rivers eventually.
Ice caps are formed in the colder regions.
At the poles, the biggest icecaps on earth are found.
Implications of Water Cycle
It is an essential part of other biogeochemical cycles.
All life processes on earth gets affected by the water cycle.
The earth’s temperature would rise drastically without the evaporating cooling effect of the water cycle.
Other Important Processes
Snowmelt
It is the runoff produced by the melting snow.
Advection
It is the movement of water through the atmosphere.
Without this, the water that evaporated over the oceans could not precipitate over land.
Percolation
Under the influence of gravity, water flows vertically through the soil and rocks.
Plate Tectonics
It is a scientific theory describing the large-scale motion of seven large plates.
This also includes the movements of a larger number of smaller plates of Earth’s lithosphere.
Transpiration
It is the release of water vapour from plants and soil into the air.
FAQs
Q1. What are the various stages involved in a complete water cycle?
Answer:
Following are the stages involved in a complete water cycle:
i) Evaporation and Transpiration
ii) Condensation
iii) Precipitation
iv) Runoff and Infiltration
Q 2. What is Sublimation?
Answer:
Sublimation process occurs when snow or ice changes directly into water vapour without becoming water.
This can be observed on mountain peaks (the air pressure is quite low).
The ice sheets covering the poles of the earth are the primary source of sublimation.
The low air pressure helps in sublimation.
Q 3. What is the importance of biogeochemical cycles?
Answer:
Biogeochemical cycles are important for regulating the elements essential for life on Earth.
This form of natural recycling allows the continuous survival of ecosystems.