What is a Water Cycle ? Explained

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WATER CYCLE

Water Cycle :  
  1. The cyclic movement of water from the atmosphere to the earth and back to the atmosphere through various processes is called  Water Cycle.
  2. The steps involved in the water cycle are :  Evaporation, Transpiration, Condensation, Percipitation and surface run off. 
  3. Water is present on the earth in rivers, ponds, oceans, lakes and soil. Some water is also present in the ground. 
  4. Heat from the sun evaporates from rivers, lakes, ponds, oceans and soil to form WATER VAPOUR (gas). This process is called EVAPORATION. 
  5. The water vapour(gas) goes into the air. The plants and trees absorb water from the soil through their roots. 
  6. The plant and trees lose water as water vapour by the process of TRASPIRATION.
  7. The water vapour goes into the air. The air containing the water vapour is heated by the sun. hot air, being lighter, rises high in the sky.
  8. So, when the air containing the water vapour rises to high altitude, the water vapour present in it gets cooled. The cold water vapour condenses to form tiny droplets of water. This process is called CONDENSATION.
  9. Thus, tiny droplets of water form clouds in the sky. The tiny droplets of water in the cloud join together to form bigger drops of water. These drops of water fall down on earth in the form of rain. This process is called PERCIPITATION.
  10. In very cold regions, the water drops in the sky freeze to form snow. So, water also falls down to earth in the frozen stat called SNOW.
  11. Water formed by the melting of snow and some of the rain water flows into river and finally into oceans. The rain water also fills the lake and ponds and gets absorbed by the soil. Some of the rain water seeps through the soil and goes under the ground. This process is called SURFACE RUN OFF.
IMPORTANCE OF WATER CYCLE 
  • Water cycle makes fresh water available in the form of rain : The sea water is highly salty which is not fit for drinking by animals or for the growth of the plants. But the rain water is pure water.
  • Water cycle keeps the amount of water or earth's surface constant : This is because, the water removed from the earth during evaporation and transpiration is put back to the earth by rain or by snowfall. 
IF IT RAINS HEAVILY
ADVANTAGES :
  •  Rain brings relief by cooling the environment after hot summer days.
  • The sowing of many crops depends on the arrival of rains during monsoon. 
  • Rain provide water in the rivers and damns of hydroelectric power plants.
  • rain fill the lakes and ponds which acts as a source of water.
  • Rains are also responsible for the ground water which gets stored under the surface of earth. 
DISADVANTAGES :
  • Heavy rain in the city areas lead to water logged roads and streets. This disrupts the traffic on roads and causes inconvenience to people.
  • It causes floods. Heavy rains leads to too much rise in the level of water in rivers. The river water starts overflowing from its  banks and spreads over a large area of land causing FLOODS
  • The flood water submerge in the cities, villages crop fields and forest causing damage to the property.
  • The animals living in water are carried away by the fast flowing flood water.
  • Heavy rains also kills the animals living in soil because animals do not get air to breathe when all the soil gets covered with water.
IF IT DOES NOT RAIN FOR A LONG TIME 
DROUGHT : 
Drought is long period without rains leading to severe shortage of water in the region. The soil in the fields is normally moist because it has water in it.
The soil continues to lose water by evaporation and transpiration.
The water lost by the soil is usually made up by rains. If it doesn't rain for a long time, the loss of water from the soil is not made up and hence, the soil becomes dry.
Due to lack of rain the water level in the lakes and ponds also goes down and some of them may even dry up completely.
In absence of rain, no water seeps into the ground and hence, the level of  groundwater in wells etc., falls drastically. Due to this groundwater also become SCARCE (shortage). 

PROBLEMS FACED DURING DROUGHTS 
  1. The soil does not have sufficient moisture(water) to grow crops well. Since, the crops do not grow well, droughts leads to severe SHORTAGE OF FOOD for the people of the region.
  2. The vegetation such as grass does not grow well and leads to shortage of fodder for the domestic animals (cows, buffaloes, etc.,)
  3. Due to shortage of food, many  people living in these areas migrate to other places along with their domestic animals in search of food.
  4. Some people and animals may even die of starvation.



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