Our Earth is covered by two-thirds of water, but most of the
water is not potable and contains salt.
Water is used for various activities such as agriculture, industries,
cooking, cleaning utensils,
bathing, washing clothes, and, most importantly, for drinking.
Ponds, wells, streams, lakes and rivers are the different sources of
drinking water.They are supplied water by the oceans and seas.Oceans
and seas supply water to other water bodies through the water cycle.
The circulation of water from the oceans and the surface of the
earth, to the air as water vapour,
and its return to the ocean as rain, hail or snow, is called the water
A variety of salts, like sodium chloride, calcium, magnesium and
potassium, are present in saline
water. The evaporation of water takes place in the water cycle,
leaving the salts behind in the ocean.
The water present on the surface of the ocean evaporates by the
sun’s heat. This process of conversion of water from liquid state to
vapour state is called evaporation. The sun warms up the surrounding
air as well. Evaporation takes place faster in direct sunlight, than
in a shady area.
Evaporation also takes place from wet clothes, fields, ponds,
lakes and rivers.
Plants take in water to grow as well as to prepare their food.
They retain the water they need and release the excess water
into the air as water vapour through
the stomata of the leaves and the stem. This process is called
Thus, water is mainly evapo-transpirated to the air from land, water
bodies and plants.
The evaporated water is carried away by warm air.As
the warm air moves higher from the surface of the Earth, it starts to
cool down. It is because the water vapour present
starts to condense to form tiny water droplets. These
droplets float in the air and form cloud and fog.
All these droplets collect to form bigger drops of water. Some of them
may become too heavy to remain in the sky and fall down as rain. This
process is known as precipitation.
If the air is too cold, the water drops can become snow or hail and
may settle on the top of a mountain. When these snow or hail melts,
they can become part of a river or a stream. Thus, the water that is
evaporated from the oceans or seas is again condensed to form water
and fills up the rivers and seas. Rain water also seeps into the
ground to form ground water.
This circulation of water is called the water cycle.