CBSE Class 7, NCERT Science
Chapter 16, Water: A Precious Resource
NCERT Answers of Exercise Questions (Only important questions)
QUESTION.1: Mark True
(T) or False (F):
(a) The fresh water stored in the ground is much more than that
present in the rivers and lakes of the world.
(b) Water storage is a problem faced only by people living in
rural areas.
(c) Water from river is the only source for irrigation in the
fields.
(d) Rain is the ultimate source of water.
Answer: (a) T (b) F (c) F (d) T
QUESTION.2: Explain how
is ground water recharged ?
Answer: The ground water is recharged by
seepage of rain water or what is known as ‘Infiltration’. The rain water and
water from other resources such as rivers and ponds seeps through the soil and
fills the empty pores and cracks below the ground.
QUESTION.3: There are ten tube wells in a lane of fifty
houses. What could be the long term impact on the water table ?
Answer: As a result of so many tube wells
within a small area a huge amount of water will be pumped out from these tube
wells which will ultimately cause a depletion of ground water in that area. The
water table will go down with the time and in longer term it will affect the
availability of water in that area.
QUESTION.4: You have
been asked to maintain a garden. How will you minimize the use of water ?
Answer: The use of water can be minimized by
-
- using drip irrigation
- preventing any leakage in the
drains in the water delivery pipes
- filling the burrows of snakes and
rats
- protect the boundaries of the
field from breakage, etc.
QUESTION.5: Explain the factors responsible for the
depletion of water table.
Answer: Following factors are responsible
for the depletion of water table:
- Increasing population - This creates demand for
construction of houses, shops, buildings, and roads etc. which require
water. It decreases open areas like parks, fields and playgrounds which in
turn, decreases the seepage of rain water into the ground. While the
increase in demand of water for the constructional activities is met using
ground water.
- Increasing industries - Water which is essential for
almost all industries are drawn from the ground.
- Agricultural activities - Farmers have to use ground
water for irrigation. Population pressure on agriculture forces increasing
use of ground water day by day. This results in depletion of water table.
QUESTION.6: Fill in
the blanks:
(a) People obtain ground
water through ______ and ______.
(b) Three forms of water
are ____, _____ and ______.
(c) The water bearing
layer of earth is _______.
(d) The process of water
seepage of water in to the ground is called ______.
Answer:
(a) tube wells, hand pumps (b) solid, liquid, gas (c) aquifer (d)
infiltration
Solutions of CBSE sample questions for Chapter 16 Water: A Precious Resource
CBSE Questions (short answer type)
QUESTION.1: On which day ‘world water day’ is observed ?
Solution: 22nd March every year.
QUESTION.2: What is fresh water ?
Solution: The water that is fit for human
consumption is called fresh water.
QUESTION.3: What percentage of water on the earth is available
for use by human being (fresh water%) ?
Solution: 0.01%
QUESTION.4: Define:
(i) Aquifer
(ii) Rain water harvesting
(iii) Drip irrigation
(iv) Ground water
(v) Water table
(vi) Bawris
Solution:
(i) Aquifer - Places where ground water is stored
between the layers of hard and impervious rock below the water table.
(ii) Rain
water harvesting -
The rain water can be stored and used to recharge the ground water. This is
referred to as rain water harvesting.
(iii) Drip
irrigation - Drip
irrigation is the technique of watering plants by making use of narrow tubing
which delivers water directly at the base of the plant. This method of
irrigation helps us to avoid wastage of water.
(iv) Ground
water - The water
found below the water table is called ground water.
(v) Water
table - The plane
which forms the upper surface of the zone of ground water saturation is known
as water table. Above the water table the rocks and soil are unsaturated. Below
water table all rocks, soil particles and pores in between them are filled with
water.
(vi) Bawris - Bawri was the traditional way of
collecting water.
CBSE Questions (long answer type)
QUESTION.1: What do you understand by water management ?
Solution: Water is a precious natural resource
which must be conserved. By the term ‘Water Management’ we mean that:
1) We
should prevent the wastage of water during supply through pipes, the leaking
taps in buildings and other places.
2) Unnecessary
use of water and overdrawing from ground water should be avoided.
3) Recharge
of ground water through the processes like Rain Water Harvesting etc should be
encouraged.
CBSE Questions (objective type)
QUESTION.1: Fill in the
blanks:
(a) ______ percentage of earth’s surface is covered with water.
(b) Water on the earth has been maintained for million of years by
various process which make _______.
(c) The ______ form of water is the water vapour.
(d) Water in the _______ can be easily pumped out with the help of tube
wells and hand pumps.
(e) _____ was observed as the International Year of Fresh Water.
Solution: (a) 71% (b) water cycle (c) gaseous
(d) aquifer (e) 2003
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