NCERT Solutions for Class 3 EVS Chapter 20 Drop by Drop

People in Madho’s village usually fetched water from a nearby pond. As the nearby pond had also dried up, his mother and sister had to walk a longer distance to fetch water. Sometimes a train carrying water use to come and Madho’s father went to fetch water in his camel-cart. Some people collected rain water through a special method – by making tanks (tanka). They filtered the rain water through a special procedure and used the water for drinking after it was cleaned.

Madho’s mother and sister went to the nearby pond to fetch water. His father went to fetch water in his camel-cart. Sometimes, Madho was permitted to take water from one of the tanks of the village.

Rain water is collected by some people through a special method by making tanks (tanka). The tanka is kept covered with a lid always and the water collected is filtered properly and is used for drinking after it is cleaned.

No, rain water is not collected in my house.

Question:
Can there be any other method of collecting water?
Answer:
Yes, water can be collected in tanks, drums, buckets, etc. It can also be stored by setting up water collection units or plastic water tanks at the house rooftop.

It is possible for us to drink untreated rainwater. This is because rainwater is pure, distilled water evaporated from the sun. This water (groundwater) is relatively safe for drinking. However, rainwater that falls to the ground does not just get absorbed into the soil, it goes everywhere.

To build a tanka, a pit is dug in the courtyard and it is made pucca. The tanka is kept covered with a lid. The roof of the house is made sloping so that the rainwater collected here flows through a pipe into the tanka. A sieve is attached to the mouth of the pipe so that no dirt goes into the tanka.

Rooftop rainwater harvesting’ was commonly practiced to store drinking water, especially in semi-arid and arid regions of Rajasthan.
(1) All the houses had underground tankas or ‘tankas’ for storing drinking water built inside the house. They were the part of the well-developed rooftop rainwater harvesting system.
(2) The tankas could be as large as a big room and were built inside the main house or the courtyard.
(3) The tanks were connected to the sloping roofs of the houses through a pipe. The falling rain would travel down the pipes and get stored in the underground ‘tankas’. The first of rain would not be collected as it cleaned the roof and pipes. The rainwater from subsequent showers was collected.
(4) Many houses constructed underground rooms adjoining the tanka to beat the summer heat as it would keep the room cool.

There are three states of the water.
• Solid water is called ice.
• Liquid water is just called water. As ice heats up, it will change its state to liquid water.
• Gaseous water is called steam or water vapour. When water boils it will turn into water vapour.

The difficulties which people face due to scarcity of water are-
• people can’t get enough to drink, wash, or do other things
• Farmers are unable to grow crops, and economic decline may occur.
• people are not able to get fresh, clean drinking water
• Water scarcity causes starvation and hunger
• It leads to the destruction of whole habitats

Oceans do not overflow even though the rivers keep adding water to them, as a lot of water evaporates and changes to water vapour due to the heat of the Sun.

This is because most of the water is found in the oceans and seas and is unfit for human consumption. We need water from freshwater sources like, rivers, lakes, ponds and streams. A large amount of freshwater is locked up in the frozen ice caps of the mountains.

Water dissolves a large number of substances in it. Substances that dissolve in water are soluble substances, like salt, sugar, soap and milk powder.
• Water has no smell or taste. Pure water is tasteless.
• Water has no shape of its own. Water takes the shape of the container in which it is kept. It can easily be poured into different containers.

Water cycle is a process in which:
• Water from the water bodies such as oceans, evaporates due to the heat of the sun.
• Water vapour rises up in the sky, cools down and condenses back into liquid water.
• These tiny droplets of water settle on small dust particles present in the air.
• These particles join together to form clouds. Many such tiny drops of water make the clouds very heavy, which then fall as rain.
• This rainwater flows into lakes, ponds and rivers. The rivers in turn flow back into the oceans. Some part of rainwater even goes underground.
• In colder areas like mountain tops water in the clouds freezes and falls as snow. In this way, water keeps circulating. This is called the water cycle.

We need water for:
• Drinking
• Bathing
• Irrigation
• Washing clothes
• Brushing Teeth
• Watering plants
• Cooking and other household work etc.

Ways to clean water are-
• Before drinking water from any source, we must make sure that it is fit for drinking. There are various ways of purifying polluted or contaminated water.
• Sometimes water contains sand or mud. Such water is not suitable for drinking.
• We can clean such water by either Sedimentation, Decantation or Filtration.
• We can also boil the water to purify it.

i. Sedimentation- Settling down of heavier insoluble particles/ solids from a mixture is called sedimentation. Like mud settles from muddy water.
ii. Decantation is pouring out of upper clear layer of liquid into another container leaving the solid particles settled at the bottom.
iii. Filtration is the process in which solid particles in a liquid or gaseous fluid are removed by the use of a filter medium like a cloth, sieve or filter paper that permits the fluid to pass through but retains the solid particles.