STD - 4, CHAPTER 8 - Water Scarcity and Conservation of Water, EXTRA QUESTIONS AND ANSWERS

 

1.      How much of the surface of earth is covered by water?

Ans: Three-fourth of the surface of earth is covered by water.

2.      Why is Earth called a blue planet?

Ans: The Earth is called a blue planet, because three-fourth of its surface is covered with water.

3.      Why the ocean water cannot be used for our daily needs?

Ans: Ocean water cannot be used for our daily needs, because ocean water is salty.

4.      Name three sources of fresh water.

Ans: Rivers, streams and lakes are the sources of fresh water.

5.      ‘Three-fourth of the surface of earth is covered by water. Still, there is a scarcity of water.’ Give reason.

Ans: i) Most of the water exists in oceans, which is salty.

ii) Only a small part of water is fresh water. Amount of fresh water is further decreasing due to various factors.

Hence, there is a scarcity of water.

6.      State three factors that are responsible for water scarcity.

Ans: Three factors that are responsible for water scarcity are, i) Population

                                                                                                              ii) Deforestation and

                                                                                                             iii) Setting-up of factories.

7.      How does increase in population lead to water scarcity?

Ans: i) With increase in population, the demand for water has also increased.

ii) More people need more water, but the supply is not increasing.

Thus, it leads to scarcity of water.

8.      Name the two main natural sources of water.

Ans: Rain and snow are the two main natural sources of water.

9.      What is deforestation?

Ans: Cutting of trees in more numbers is called deforestation.

10.  State two reasons that are leading to clearing of forests.

Ans: i) Forests are being cleared, for building houses and factories.

ii) Also, people cut trees for earning money by selling the wood of trees.

11.  State the effect of deforestation on rainfall.

Ans: Deforestation results in a decrease in rainfall.

12.  How can we bring balance in nature?

Ans:i) We can bring balance in nature by taking strict steps to prevent deforestation.

ii) More and more trees need to be planted to maintain the balance in nature.

13.  How does setting-up of factories affect the ground water level?

Ans:  i) The factories need a large quantity of water. So, they use underground water.

ii) Due to shortage of rainfall, underground water does not get filled up again as much as it is used.

iii) This has led to a sharp decrease in the level of underground water.

14.  What is the need to save water?

Ans: i) If we continue to waste water resources carelessly, a time will come when there will not be enough water for all of us.

ii) The crops can also die due to lack of irrigation.

So, there is a need to save water now, so that it remains available for use in future also.

15.  What is water conservation?

Ans: Proper and careful utilisation of water, avoiding its wastage, and maintaining the amount of water in its different sources, is called water conservation.

16.  State the different ways of conserving water at home.

Ans: We can conserve water at home by adopting the following measures.

i) Turn off the tap after using it.

ii) Do not keep the tap running while brushing teeth or washing hands.

iii) Use a mug and bucket to take bath instead of a shower.

iv) Water the plants with a bucket and mug instead of a pipe.

v) Take only that much water in a tumbler that you can drink. Do not throw the leftover water in the sink. Pour it over plants.

vi) Do not throw away water used for washing vegetables, rice or pulses. Use it for watering plants.

vii) Get the leaking pipes and taps repaired immediately.

17.  How should the fields be irrigated toreduce wastage of water?

Ans: i) Over-irrigation of fields should be checked.

ii) Water sprinkler should be used for irrigation. This reduces the wastage of water.

18.  State the utilities of dams.

Ans: i) Dams preserve a large quantity of water.

ii) Dams also check floods.

19.  What is rain water harvesting?

Ans: Collecting rain water for day-to-day use, is called rain water harvesting.

20.  State two ways to do rain-water harvesting.

Ans: i) Rain water can be collected in large underground tanks from where it seeps slowly into the ground.

ii) Rain water may also be collected in overhead tanks and used for daily needs.

21.  How can we increase the level of underground water?

Ans: By collecting rain water in large underground tanks from where it seeps slowly into the ground, we can increase the underground water.