Water Cycle

Water Cycle –

 

The ocean is the major reservoir of water which covers about seventy percent of the earth's surface. Ocean water is salty. Freshwater is mostly found in rivers, glaciers and in between rocks below the surface of the earth.

The water cycle is driven by the sun's heat energy, which causes water to evaporate while gravity draws the water back to earth in the form of rain, snow etc after water vapour condenses. The water cycle is divided into 4 basic steps.

1) All water, which is used by mankind for personal and industrial purposes, is plain or freshwater, which is derived largely from the ocean water through evaporation and precipitation.

2) As the precipitation reaches the earth, some of the waterfalls directly on the ground, some falls on vegetation, on buildings, and on streets. A part of the water that falls on the ground, seeps through the soil, to an impervious layer of clay or rock where it is collected as groundwater. The rate of downward movement of water in the soil is dependent on the type of soil, its slope, type of vegetation and the amount of rainfall. The underground water is utilised by human beings for domestic, agricultural or for industrial purposes.

3) Some of the water falling on the ground runs down the gutters and drains to be carried off to rivers. Some surface runoff water may also get collected in small ditches, lakes, etc.

4) So far we have been discussing the various ways in which water, in different forms, reaches the earth. Now let us understand as to how water reaches back to the

atmosphere.

i)                   Some amount of rainwater never reaches the ground as it evaporates back into the atmosphere.

ii) Plants also give out large amounts of water back to the atmosphere through their leaves.

iii-v) The water remaining on the surface of the ground and on vegetation as well as the water in the surface layers of streams, lakes mad oceans evaporates and goes back to the atmosphere. As the water vapors in the atmosphere form clouds and drift with the wind,'they eventually meet cold air and condense, this leads to rainfall, snowfall, etc. and thus the water cycle continues.