NCERT Solutions Class 7 Science Chapter 16 Water A Precious Resource

NCERT Solutions for Class 7 Science for chapter 16 Water A Precious Resource

Exercises

1. Mark ‘T’ if the statement is true and ‘F’ if it is false:
(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. (T/F)
(b) Water shortage is a problem faced only by people living in rural areas. (T/F)
(c) Water from rivers is the only source for irrigation in the fields. (T/F)
(d) Rain is the ultimate source of water. (T/F)

Answer

(a) T
(b) F
(c) F
(d) T

2. Explain how groundwater is recharged?

Answer

The rainwater and water from other sources such as rivers and ponds seeps through the soil and fills the empty spaces and cracks deep below the ground. The process of seeping of water into the ground is called infiltration. The groundwater thus gets recharged by this process.

3. There are ten tubewells in a lane of fifty houses. What could be the long term impact on the water table?

Answer

This will lead to exploitation of water resource present underground if people of all the fifty houses in the lane use the ten tubewells regularly. In long term, the water level will go below and thus the depletion of tubewells.

4. You have been asked to maintain a garden. How will you minimise the use of water?

Answer

For minimising the use of water in maintenance of garden, i will use the technique of drip irrigation. In this method, required amount water is supplied directly to the roots of the plants using narrow pipes thus preventing the loss of water.

5. Explain the factors responsible for the depletion of water table.

Answer

Factors responsible for the depletion of water level:
(i) Increase in the demand of water due to overpopulation.
(ii) Deforestation leads to less rainfall which affect the recharge of river and pounds.
(iii) Increase the number of industries as they use a lot of water for their purpose.
(iv) Insignificant uses in agriculture activities as in many parts of the world people uses old techniques which waste a lot of water.
(v) Lack awareness in people is also a main reason behind the depletion of water level as they waste water without any uses.

6. Fill in the blanks with the appropriate answers:
(a) People obtain groundwater through________ and ________ .
(b) Three forms of water are ________, ________ and ________.
(c) The water bearing layer of the earth is ________.
(d) The process of water seepage into the ground is called ________.

Answer

(a) People obtain groundwater through tube wells and hand pumps. 

(b) Three forms of water are ice, water and vapour. 

(c) The water bearing layer of the earth is aquifer. 

(d) The process of water seepage into the ground is called infiltration.


7. Which one of the following is not responsbile for water shortage?
(i) Rapid growth of industries
(ii) Increasing population
(iii) Heavy rainfall
(iv) Mismanagement of water resources

Answer

(iii) Heavy rainfall

8. Choose the correct option. The total water
(i) in the lakes and rivers of the world remains constant.
(ii) under the ground remains constant.
(iii) in the seas and oceans of the world remains constant.
(iv) of the world remains constant.

Answer

(iv) of the world remains constant.

9. Make a sketch showing groundwater and water table. Label it.