TEXTBOOK ANSWERS AND SOLUTIONS OF CBSE CLASS VII SCIENCE Chapter 16 Water-A Precious Resource

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)
(b) Water shortage is a problem faced
only by people living in rural areas. (F)
(c) Water from rivers is the only source
for irrigation in the fields. (F)
(d) Rain is the ultimate source of
water. (F)
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:-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.


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


ANSWER:- To maintain a garden, water is necessary. Therefore, to minimise
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.

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 affects 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 use 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 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 responsible 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.