Class 7 Science

Water

NCERT Solution

Question 1: Mark ‘T’ if the statement is true and ‘F’ if it is false:

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

Answer: (a) T, (b) F, (c) F, (d) T

Question 2: Explain how groundwater is recharged?

Answer: The surface water seeps down the ground through the porous layers of the soil. This process is called infiltration and is responsible for recharging the groundwater.


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

Answer: Ten tube-wells in a lane of fifty houses can lead people to mindlessly exploit the groundwater. This can lead to depletion of the water table in the long run.

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

Answer: Drip irrigation can be used in the garden to minimize the use of water.



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

Answer: Following factors are responsible for depletion of water table:

  • There is more demand of water due to increasing population. Increasing population means there is ever increasing demand of water for various human activities.
  • Deforestation has removed a large portion of forest cover. This has disturbed the natural process of recharging the groundwater.
  • While demand for water has increased, the supply has reduced. The mismatch between demand and supply is mainly responsible for depletion of water table.

Question 6: Fill in the blanks with the appropriate answers:

  • People obtain groundwater through________ and ________.
  • Three forms of water are ________, ________ and ________.
  • The water bearing layer of the earth is ________.
  • The process of water seepage into the ground is called ________.

Answer: (a) wells and tube-wells, (b) ice, water and vapour, (c) aquifer, (d) infiltration



Question 7: Which one of the following is not responsible for water shortage?

  • Rapid growth of industries
  • Increasing population
  • Heavy rainfall
  • Mismanagement of water resources

Answer: (iii) Heavy rainfall

Question 8: The total water

  • In the lakes and rivers of the world remains constant.
  • Under the ground remains constant.
  • In the seas and oceans of the world remains constant.
  • Of the world remains constant.

Answer: (iv) Of the world remains constant