Water - A Precious Resource Summary Class 7 NCERT Summary

How much water is available?

• Earth’s surface is covered with about 71% of water.
• Not all water is good for human consumption. The water fit to use is fresh water.
• All water on the earth is contained in the seas and oceans, rivers, lakes, ice caps, as groundwater and in the atmosphere.

Water Forms

• Water on earth can be maintained for millions of years by various processes which make water cycle.
• Water circulates in water cycle which is found in three forms. They are:
  (i) Solid: Snow-covered Mountains and glaciers.
  (ii) Liquids: Oceans, lakes, rivers and underground.
  (iii) Gaseous: Water vapor in atmosphere.

Water cycle

• It is also known as hydrologic cycle.
• Water cycle describes the continuous movement of water on the surface or below the surface of earth.
• The balance of water on earth remains fairly constant over time individuals water molecules can come and go in and out of the atmosphere.

Steps of water cycle

• Ground water
• Evaporation
• Condensation
• Clouds
• Transpiration
• Infiltration
• Precipitation

Groundwater

• Ground water is the large storage of water is inside the ground.
• The water is located beneath the ground surface in soil pore spaces and in the fractures of rock formations.
• Water table is the upper limit of layer.
• Ground water is founds below the water table.
• Infiltration: It is a process of seeping of water into the ground is called infiltration.
• Aquifer: water which is stored between layers of hard rocks below the water table is called aquifer.

Depletion of water table

• If water is not sufficiently replenished then water table may go down.
• The reason is increasing population, industries, agricultural activities, decrease of seepage area for seepage of rainwater, deforestation and scanty rainfall.

Water management

• Ground water that we get as rain fall just flows away. Rainwater is used to recharge the groundwater. This is referred to as water harvesting.
• In India water storage and water recharge like the Bawris. It was the traditional way of collecting water.
• Drip Irrigation is water saving Irrigation system. In this system, water falls on the roots of the plants drop by drop by the help of pipes.
• We should turn off taps while bathing.
• Map the floor instead of washing.
• Use a bucket instead of bathtub.

Reasons for scarcity of water

• Deforestation.
• Uneven distribution of rainfall.
• Scanty rainfall.
• Increasing industries.
• Increasing population rate.