Chapter 16 : Water: A Precious Resource - Ncert Solutions for Class 7 Science CBSE

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Chapter 16 - Water: A Precious Resource Exercise 203

Solution 1

(a) The freshwater stored in the ground is much more than that present in the rivers and lakes of the world. True
(b) Water shortage is a problem faced only by people living in rural areas. False
(c) Water from rivers is the only source for irrigation in the fields. False
(d) Rain is the ultimate source of water. False

Concept insight: Important from Exam Point of View.

Solution 2

Rain water and the water from water bodies on earth's surface pass through the soil by the process of infiltration. This water than gets accumulated in the water table. This is how ground water gets recharged.

Concept insight: Ground water is recharged by the rain water through the process of infilteration.

Solution 3

If the people of the fifty houses use the ten tube wells, then the water required by them is drawn from the ground. If these tube wells are used for long time, then the ground water would be reduced and the water table would go down.

Concept insight: Tube wells directly take water from the ground water.

Solution 4

To maintain a garden, water is necessary. Therefore, to minimize the use of water, we can apply the drip irrigation method. In this method, water is supplied directly to the base of the plants using narrow pipes, thereby reducing the loss of water.

Concept insight: In drip irrigation method water is directly supplied to the base of the plants by narrow pipes.

Solution 5

The factors responsible for the depletion of water table are as follows:
(i)Increasing population - As a result of increasing population, all the facilities such as houses, shops, roads, offices, pavements, etc. increase to fulfil the increasing demands. This, in turn, decreases the open area for seepage of water into the ground.
(ii) Industrialization -  Most of the stages of manufacturing processes in industries require water. If the number of industries increases, then the water required by them will also increase. Therefore, increase of industries contributes to the depletion of water table.
(iii)Agricultural activities - India is an agricultural country and agriculture is impossible without water. The water for agriculture is mainly utilized from ground water, rain water and canal water. As there is no rainfall in many places, agriculture cannot be entirely dependent on rain water. Also, canal water is available in a few places only. Therefore, ground water is the main source of water for agricultural activities and this causes depletion of water table.

Concept insight: List the factors responsible for depletion of water table.

Solution 6

(a) Tube wells and hand pumps
(b) Ice, water and vapour
(c) Hydrosphere/aquifer
(d) Infiltration


Concept insight: Important from Exam Point of View.

Chapter 16 - Water: A Precious Resource Exercise 204

Solution 1

(iii) Heavy rainfall

Concept insight: Rainfall increases the water table.

Solution 2

The total water
(iv) of the world remains constant.

Concept insight: Important from Exam Point of View.

Solution 3

Concept insight: Recall the concept of water table and ground water.

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