CBSE – 7th Standard Science

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Chapter 16 – Water: A Precious Resource

Chapter 16

 Water: A Precious Resource 

  • Water on the earth has been maintained for millions of years by various processes which make the water cycle.

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  • The solid form, snow and ice, is present as ice caps at the poles of the earth, snow-covered mountains and glaciers.
  •  Liquid water is present in oceans, lakes, rivers, and even underground. The gaseous form is the water vapour present in the air around us.
  • 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 groundwater thus gets recharged by this process.

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  • At places the groundwater is stored between layers of hard rock below the water table. This is known as an aquifer.
  • Groundwater is an important source of water.
  • A level where all the space between particles of soil and gaps between rocks are filled with water is called the water table.

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  • This may happen due to many reasons.
  •  Increase in population, industrial and agricultural activities are some common factors affecting water table.
  • Scanty rainfall is another factor that may deplete the water table.
  • Yet another factor affecting water table could be deforestation and decrease in the effective area for seepage of water.
  • Increasing population creates demand for construction of houses etc.
  • This decreases the open areas like parks, and playgrounds. This, in turn, decreases the seepage of rainwater into the ground.
  • Moreover a huge amount of water is required for construction work.
  • Often groundwater is used for this purpose, on one hand we are consuming more groundwater, and on the other we are allowing lesser water to seep into the ground.
  • This results in depletion of water table.
  • Water is used by all the industries.
  •  Almost everything that we use needs water somewhere in its production process.
  • The number of industries is increasing continuously.
  • Water used by most of the industries is drawn from the ground.
  • A majority of farmers in India depend upon rains for irrigating their crops. Irrigation systems such as canals are there only in a few places.
  •  Even these systems may suffer from lack of water due to erratic rainfall.
  • Farmers have to use groundwater for irrigation.
  •  Population pressure on agriculture forces increasing use of groundwater day by day.
  •  This results in depletion of water table.
  • Some places have good amount of rain and are water-rich. On the other hand, there are deserts which have scanty rainfall.
  • Excessive rains cause floods, whereas the absence of rains results in droughts.
  • Therefore, some regions in our country may have floods while others may suffer from droughts at the same time.
  • Supply of water is provided by a well-planned pipe system.
  •  When the civic authorities supply water supply pipes leaking and a lot of water gushing out of the pipes.
  • It is the responsibility of the civic authorities to prevent such wastage of precious water.
  • Wastage may take place at the level of individuals also.
  • We waste water while brushing teeth, shaving, bathing, washing and during many other activities.
  • Leaking taps is another source of huge water wastage.
  • The rainwater can be used to recharge the groundwater.

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  • This is referred to as water harvesting or rainwater harvesting.

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  • Drip irrigation is a technique of watering plants by making use of narrow tubings which deliver water directly at the base of the plant.

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  • If water is not available to plants,
  • The green character of the planet shall be lost.
  • This may mean the end of all life, for a world without plants shall mean no food, no oxygen, not enough rain, and innumerable other problems.
  • Water is essential for all living beings. There can be no life without it.
  • Water exists in three forms: solid, liquid and vapour.
  • Though water is maintained by the water cycle, yet there is an acute scarcity of water in many parts of the globe.
  • There is an uneven distribution of water. Much of it has resulted from human activities.
  • Rapid growth of industries, increasing population, growing irrigation requirements and mismanagement are some of the causes for water shortage.
  • We need to be worried about the wastage during the supply of water through pipes, the leaking taps in buildings and other places.
  • Unnecessary use of water and overdrawing from groundwater should be avoided. Recharge of water to the ground should be increased.
  • The need of the hour is that every individual uses water economically.

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