Effects of Rainfall - Droughts and Floods


LearnNext Lesson Video

Water cycle plays an important role in maintaining the climate. Oceans absorb heat from the sun. They provide warmth on the land. Water gets evaporated from the surface of oceans by absorption of heat. Water vapour releases heat by cooling in the process of condensation. This continuous absorption and release of heat in the form of heat maintains the constant climate of a particular place.

Natural calamities
Natural calamities related to water are floods and droughts. These are uncontrolled conditions during which floods and droughts prevailing affect an area or a region on earth.

a) Floods: The condition during which rain water being everywhere, even submerging the land is called as flood. 

  • Floods are caused by rise in the water level in ponds and lakes due to heavy rainfall. The excess rain water flows on to land causing floods. Floods make the soil water-logged.
  • Floods affect normal life by disturbing everything which comes in its way.
  • Floods wash out the living beings such as plants, fish and other animals etc.
  • Floods create water-logging in the soil bringing out stored air from the spaces. Organisms like earthworms, ants, insects rats, rabbits, snakes living under soil get disturbed by floods.
  • Floods cause heavy loss to human life.
  • Floods damage different types of property.
  • Floods cause uprooting of trees. Floods wash away the crops.
  • Floods result in shortage of food supply.
  • Floods cause stagnation of water forming the breeding ground for many disease causing organisms. Diseases can easily spread out during floods. These are called as water-borne diseases.
  • Floods cause disruption of modes of transport and communication.
  • Floods also disturb many kinds of food chains.

b) Droughts: Droughts are the conditions which involve abnormally long period of insufficient or no rainfall.
  • Droughts are caused due to lack of rains. 
  • Drought condition results in drying up of wells, lakes, ponds and thereby creating water scarcity. 
  • Droughts result in the evaporation of water from the soil leaving the soil dry and patchy. 
  • Droughts result in mass death of plants and animals due to dehydration. 
  • Droughts affect agriculture and lessen food production. 
  • Droughts result in death of animals and birds which provide us animal products like milk, meat and eggs. This scarcity of food results in the famine.
  • Droughts result in forest fires caused by enormous amount of heat from scorching sun.

Water conservation
Water is an essential natural resource. These exists no life without water. Water is so precious that it has to be conserved.
  • Avoiding water wastage is also a kind of water conservation.
  • Excess rain water running in the river is stored in huge and special structure called as dam.
  • Dams are huge structures built on rivers to hold back excess water. Dams prevent areas from flooding by storing large amount of water.
  • Dams provide water for irrigating fields, domestic use and also drinking water for some areas.
  • Drinking water should not be wasted to water the plants.
  • Water bodies should not be polluted in order to get pure water.
  • Water should not be wasted during irrigation of fields. Modern methods like spraying, sprinkling or drip irrigation should be used.
  • Water should be used judiciously to avoid wastage.
  • Destruction of trees should be controlled to increase the rainfall.

Rain water harvesting

Rain water harvesting includes collection and storing of rain water from the roofs of houses and huge constructions. This is also called as roof-top rainwater harvesting. Constant use of fresh water from the ground results in water scarcity. Rain water harvesting increases the level of ground water.

Technique involved in rain water harvesting

  • Rain water is collected at the roof top.
  • It is allowed to flow into pipes.
  • It is filtered through wire mesh.
  • It is allowed to pour into an underground tank setup to store rain water. These tanks contain layers of sand, gravel, charcoal that will filter the dirt and other impurities from rain water.
  • This water seeps back into ground slowly to increase the level of ground water table.
  • of concrete floor which does not allow the rain water to seep into the ground.

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Activities & Simulations

Activity 1
Dmc.gov.lk has formulated an informative game designed to explain the topic droughts. This is devised as a snake and ladder game. Student has to select the number of players and name the players. These players are taken to the game chart. A die and coins are given to represent the players. After the rolling the die student needs to press the 'Go' button. Coins climb up the ladders and come down the snakes. Every satge has got flah cards about water conservation, ill effects of droughts etc.
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Activity 2
Floodsmart.gov has created an animated video to explain the concept of ' Floods'. This is an activity which discusses different types of scenarios under different captions. All the scenarios are represented as buttons at the top. At all the scenarios, the disastrous conditions caused by floods are explained with the help of animation. Student has just to click on the different options according to the information provided. This module helps the student to learn about the ill-effects of floods caused in different areas.
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