4th Class Science Weather, Air and Water Water


Category : 4th Class


This lesson will help you to:

  • learn and study about the various water sources.
  • study about the ill effects of drinking dirty water.
  • study about the seasonal change in water flow and about different water animals.
  • study about water pollution and its harmful effects on the animals.
  • learn about the importance of water conservation.



Sources of Water

The various sources of water are ocean, sea, rivers, springs, lakes, ponds, wells, taps, rains, waterfalls etc. Water is also stored underground.


Real Life Examples

  • We often see water boiling in our homes to kill the germs in the water and make it germ free.
  • During rainy reason. We often see pople suffering from fevers and diarrhea. The reason behind this is the contamination of water and the high percentage of germs in the rainy season.



  • Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater), very often by human activities.
  • Water pollution occurs when pollutants (particles, chemicals or substances that make water contaminated) are discharged directly or indirectly into water bodies without enough treatment to get rid of harmful compounds. Pollutants get into water mainly by human causes or factors.
  • Water pollution affects drinking water, rivers, lakes and oceans all over the world. In many developing countries, it is usually a leading cause of death, by people drinking from polluted water sources.
  • The effects of water pollution are varied and depend on what chemicals are dumped and in what locations.
  • Many water bodies near urban areas (cities and towns) are highly polluted. This is the result of both garbage dumped by individuals and dangerous chemicals legally or illegally dumped by manufacturing industries, health centers, schools and market places.
  • The various effects are:

(a) Death of aquatic (water) animals.

(b) Disruption of food-chains.

(c) Diseases- People can get diseases such as hepatitis by eating seafood that has been poisoned.

(d) Destruction of ecosystems.


Historical preview

  • Ancient sanskrit writing known as “Sus’ruta Samhita,” which dates back to approximately 2000 B.C., reveal a traditional recipe using alum that was used to purify water. In the recipe, a lump of earth (alum) was mixed with local Indian herbs, with names such as phana, mustaka, ela, ustra and candana, and baked well in a fire. The resulting material was then dropped into water to purify it.



Drinking or swimming in unclean water can cause:

  • Vomiting or diarrhoea
  • A sick stomach
  • Skin rashes
  • Cancer (Some kinds of cancer can happen after drinking bad water for a long period of time.)



Misconcept: Fresh water is one of the earth’s most abundant natural resources.

Concept: Only 3% of the water on earth is fresh 3%, 2% is found in glaciers and only 0.5% is accessible.

Misconcept: Businesses and industries are majorly responsible for water pollution.

Concept: water pollution from residential areas is large source of water pollution as well.



The flow of water changes according to the season. In the rainy season, the flow of water increases whereas in summers, the water evaporates at a fast pace thus the flow of water also decreases.



The animals that live in water are known as water animals or aquatic animals. The various water animals are fishes, octopus, turtles, sea horse, crabs, prawns and shrimps.

Other Topics

Notes - Water

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