Water A Precious Resource - Revision Notes

 CBSE Class 7 Science

Revision Notes 
Chapter – 16
Water: A Precious Resource

  • Water is essential for all living beings. No one can imagine life without water.
  • Water exists in three forms: solid, liquid and gas.
  1. Solid: At poles of earth, snow-covered mountains and glaciers.
  2. Liquids: In oceans, lakes, rivers and underground.
  3. Gaseous: Water vapors in air.​
  • Surface water: Sea and oceans, Rivers, Springs, Lakes and Ponds.
  • Ground water: It is the water that sweeps into the ground through soil and collects over non-porous rocks (aquifer). Level of groundwater at any place is called water table. Groundwater gets recharged by seepage of water into the ground (infiltration).
  • Water scarcity: Depletion of water table.
  • Reasons for scarcity of water
  1. Increase population decreases open areas which decreases seepage of rainwater.
  2. Increasing industries more water is drawn out from ground.
  3. Agricultural activities irrigation systems fail due to erratic rainfall which results in increased use of ground water.
  4. Uneven distribution of rainfall.
  5. Scanty rainfall.
  6. Deforestation.
  • 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. Most of it has been 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 should use water economically.
  • Plants wilt and ultimately dry-up if they are not watered for a few days.