Class 7 Science Chapter 16 Notes
In this chapter, the main idea is to aware the students about the importance of water in life. Life is impossible without water. As it is rightly said “Jal Hai to Kal Hai“.
Class 7 Science Chapter 16 Overview
Here is the list of topics that we will study in this Class 7 Science Chapter 16 Water A Precious Resource.
- Uses of Water
- Scarcity of Water
- Availability of Water
- Forms of Water
- Water Cycle
- Depletion of Water Table
- Management of Water
- Rainwater Harvesting
Uses of Water
There are different uses of water. Water is used for drinking, bathing, cooking food, watering plants, washing, etc. But let us categorize some the important uses of water.
- Domestic Uses: it is used for drinking, cooking food, bathing, etc.
- Industrial Use: Water is used for cooling machines, for making chemicals, dyes, etc.
- Agricultural Use: used by farmers for watering their land to grow crops.
- Hydroelectricity: Used for generating electricity.
Scarcity of Water
It means the shortage of water. Due to the huge consumption of water for various purposes like industrial use, domestic use, etc. is causing the reduction or shortage of water.
Availability of Water
- 71% of the earth is covered with water, and it is available in the oceans, seas, lakes, rivers, glaciers, etc.
- Most of the water is not fit for drinking or cannot be directly accessed.
- Out of these 71% water. 97.5% is saline in nature, and only 2.5% is freshwater in different forms.
- Out of this 2.5% freshwater, 68.7% is in the form of glaciers, ice-caps, 30.1% is Groundwater, 0.4% is in lakes and rivers, and 0.8% are in some other forms.
Forms of Water
The water is available in three forms namely Solid, Liquid, and Gas.
Solid- Glaciers, ice-caps
Liquid- Rivers, Lakes, etc.
Gas- water vapor in the atmosphere
It is a natural process that helps in rainfall in which water from the earth goes to the atmosphere and again come back to the earth in the form of rainfall.
The different processes involved in the water cycle are-
Evaporation: water converts to vapor
Transpiration: water converts to vapor. water is lost to the environment from the aerial parts of the plants.
Condensation: water vapor condenses to water droplets
Precipitation: condensed water falls on the earth in the form of rain, snow, hail
The water found inside the earth below the water table.
It is process of seeping of water into the ground is called infiltration.
These are the water-storing underground layers below the water table that supply water to wells. This can be used as a source of freshwater for our use.
Depletion of Water table
The underground water gets recharged due to the seepage or infiltration of rainwater.
The excessive use of water and change in the climate has depleted the water table.
Reasons for Water table depletion-
The are many reasons for the depletion of water table. Some of the main reasons for its depletion are as follows-
- Population increase
- Increase in industries
- Increase in agricultural activities
- Scanty waterfall
Management of Water
We use different ways in order to meet the shortage of water. These various ways of saving and conserving the water is called management of water.
Some of the techniques of managing the water shortage are-
- Rainwater Harvesting
- Construction of Bawris
- Drip Irrigation
It is a method of conserving or recharging the groundwater by catching, collecting and storing.
This helps to prevent the rainwater from flowing away to the sea, or mix with dirty water.
- It is a method of watering the plants.
- In this method the water is directly delivered to the plant’s root.
- Watering is done with the help of network of small tubes drop by drop in a slow and controlled manner.
- Since water is not sprayed over the entire field, it helps in conserving water by reducing evaporation and runoff.
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