Saturday , May 21 2022

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

Question: Define the following: Glacier, Iceberg, Snow, Hail, Frost.

Answer: Glacier: It is large chunk of ice that moves like a river over the surface of land. Glaciers are found moving from high mountains and are a source of fresh water.

Iceberg: It is a large piece of ice that has broken off a glacier and floats in seas and oceans.

Snow: It is a form of precipitation in which crystals of ice fall on the ground.

Hail: These are hard lumps of ice falling from the sky during precipitation.

Frost: It is formed when water vapour solidifies and gets deposited on plants, trees, homes, vehicles etc.

Question: What are the reasons for an increase in the demand of water?

Answer: The reasons for an increase in the demand of water are:

  1. Increasing population: Increase in population creates demand for construction of houses, shops, offices, roads and pavements. A huge amount of water is required for construction work.
  2. Increasing Industries: With the increase in population demand for mass production increases and hence there is increase in number of industries. Water is used by all the industries. Almost everything that we use needs water somewhere in its production process. Thus increase in the number of industries means increased demand of water.
  3. Agricultural activity: Increased population demands more food so the agriculture activities have been modified to increase production. Earlier farmers depend on rainfall for irrigating their crops now, they use canals and groundwater.

Question: How does afforestation help in improving groundwater?

Answer: Deforestation leads to less rainfall. A major remedy to lessen the problem of scarcity of water is afforestation. Large areas of forests are being wiped out due to an ever-increasing population. Planting trees and increasing the forest cover would lead to good rainfall and less pollution.

Question: What is rain water harvesting and how it is important?

Answer: Rainwater falls on the roofs of houses and buildings. From there, it passes into the gutters, lining the edge of the roofs. It flows through the gutters and pipes into the tanks built on the ground or under the ground. This water is stored in the tanks until required. It is drawn up by pumps. It can be used for domestic purposes as well as for agricultural uses. A lot of rainwater goes into storm drains during rainy seasons. This water can be conserved for use or to replenish the groundwater levels by the method of rainwater harvesting.

Question: Write a note on the natural distribution of water in India.

Answer: The movement of wind influences rainfall in India. The amount of rainfall is not uniform at all the places. Uneven rainfall leads to floods in some place and droughts in other places. Some regions like the north-eastern states of Meghalaya, Sikkim, Manipur etc. get torrential rainfall during monsoon season. Some coastal states like Andhra Pradesh, Odisha and west Bengal get rainfall due to the cyclones in the sea and high winds. The heavy rainfall in these regions causes floods, destroying life and property. However, the western regions of Rajasthan, Gujarat and Madhya Pradesh do not have sufficient rainfall, leading to drought conditions.

Question: What are the uses of water?

Answer: Water is used for various activities such as agriculture, industries, cooking, cleaning utensils, bathing, washing clothes and most importantly for drinking.

Question: What are the causes of water scarcity in India?

Answer: There are many causes of water scarcity:

  1. Rapid increase in population has led to a greater demand for more water.
  2. The use of water as coolant in industries and for washing causes scarcity and also leads to pollution of water resources. This causes water to become unfit for use.
  3. Deforestation leads to less rainfall.
  4. Agriculture in India mainly depends on rainfall, however it is unseasonal and irregular, which causes scarcity of water and eventually leads to crop loss.
  5. Leaking pipes, taps and overflowing tanks are the major contributors to water wastage in the cities. Water gets wasted due to ignorance, wrong attitudes and general apathy- lack of responsibility.

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