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%) ?
(ii) Rain water harvesting
(iii) Drip irrigation
(iv) Ground water
(v) Water table
(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