7th Class Science Water: A Precious Resource Water - A Precious Resource

Water : A precious Resource

Synopsis

• Water is the most essential thing for the existence of life. Water is an extremely stable compound. It does not decompose into its constituents, hydrogen and oxygen, easily.

• Water exists in three states - solid, liquid and gas.

• About \[71%\]of the earth's surface is covered with water but only \[0.006%\] of the water found on the earth is available for our use.

• The continuous cycling of water among its three forms keeps the total amount of water constant. This is known as water cycle.

• 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.

• Water in our body helps in the movement and absorption of nutrients. It also helps to control the body temperature.

• Ground water is an important source of fresh water. The availability of ground water depends on the water table of a place.

• The water table goes down if the usage is more than the replenished water through rains and seepage.

• Rapid growth of industries, increasing population, growing irrigation requirements and mismanage-ment are some of the causes for water shortage.

• Water harvesting is one of the methods of recharging ground water.

• The seeping of water into the ground is called infiltration.

• Ground water at some places is stored between the layers of hard rock below the water table is known as aquifer.

• Sewage is liquid waste. The impurities in water are called contaminants.

• Chemicals used in agriculture, factories and human waste contaminate water.

• Plants wilt and ultimately dry-up if they are not watered for a few days.

• Waste Water Treatment Plants (WWTP) clean water before its disposal by using a series of processes like filtration, sedimentation, skimming, treatment with anaerobic and aerobic bacteria, chlorination, etc.