CBSE – 7th Standard Science

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.

 

• 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.

• 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.

• 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.

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

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

• 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.