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.
- Solid: At poles of earth, snow-covered mountains and glaciers.
- Liquids: In oceans, lakes, rivers and underground.
- 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
- Increase population decreases open areas which decreases seepage of rainwater.
- Increasing industries more water is drawn out from ground.
- Agricultural activities irrigation systems fail due to erratic rainfall which results in increased use of ground water.
- Uneven distribution of rainfall.
- Scanty rainfall.
- 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.