Tuesday , July 5 2022

NCERT 7th Class (CBSE) Science: Water: A Precious Resource

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

Answer: For maintaining the garden, we can take following steps to minimise the use of water:

  1. We can employ drip irrigation to water the garden. Drip irrigation is a technique of watering plants by making use of narrow tubings which deliver water directly at the base of the plant.
  2. We should water the plants in garden in early morning hours.If you are unable to water early in the morning, late afternoon is the next best; this is after the sun’s heat has lost its harshness but before the chill in the air begins to set in.
  3. We should avoid using a sprinkler during windy weather, as the water will blow away and evaporate, wasting the water.

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

Answer: Water drawn from under the ground gets replenished by seepage of rainwater. The water table does not get affected as long as we draw as much water as is replenished by natural processes. However, water table may go down if the water is not sufficiently replenished. As stated, there are ten tube wells in a lane of fifty houses, so the quantity of water being pumped out by 10 tube wells can not be replenished by the available sources like rain, drainage to recharge the ground water table. As a result of this, in long term the water table beneath will be get depleted and after some years there will be no water for 10 tube wells to pump out.

Question: Explain how we can recharge ground water?

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. At places the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer. Water in the aquifers can be usually pumped out with the help of tube wells or hand pumps.

Question: Explain the three form of water that exists in nature.

Answer: In nature, water exists in three forms:

  1. As a solid, it exists as icecaps at the poles, snow-covered mountains and glaciers.
  2. As a liquid, it is in the form of water in oceans, lakes and rivers, and underground water.
  3. Its gaseous form is the water vapour in the air around us.

Question: What is water management?

Answer: Water management is the continuous matching of water resources with the water requirements of a place.

  1. Water management essentially involves activities that identify sources of water, prevent wastage of water, and implement recycling of water.
  2. It may also include treatment of water to make it suitable for human consumption
  3. Prevent wastage of water
  4. Water leaking from pipes
  5. Leaking tap
  6. Water over-flowing from buckets while clothes are being washed along side
  7. A person brushing teeth with the tap left running

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