DESRIBE WATER CYCLE

The earth has a limited amount of water which gets recycled continuously. This recycling of water is called the water cycle. Broadly, water cycle comprises evaporation of water, its falling on land as rain and its flowing into the sea via the rivers.

To understand the water cycle, we should know:

• How water is lost from the environment
• The processes of change and the different states of water
• The method by which water is returned to the environment

Steps involved in the water cycle are:

• Evaporation and transpiration
• Condensation
• Precipitation
• Surface runoff

Step 1:Evaporation and transpiration

Water molecules change into water vapours and move up the atmosphere by the process ofevaporation. The excess water absorbed by plant roots is released through the pores on the surface of leaves by the process oftranspiration.

Step 2:Condensation

The process by which water vapours move upward, cool down in the higher atmosphere and form clouds is calledcondensation.

Step 3:Precipitation

As condensation proceeds, water vapours change into water droplets. When enough water droplets accumulate, they fall down as rain. This process is calledprecipitation.

Step 4:Surface runoff

Rains replenish the water in the ponds, lakes, rivers and oceans. The process wherein rainwater enters the soil is known as infiltration. The process in which rainwater flows over the surface of land before entering different water bodies is called surface runoff.

At very low temperatures, water droplets freeze and fall down as hail, snow or sleet.