⛪Home⇐ Class VII RAIN AND RIVERS


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Class VII - Social: Rain and Rivers
One Word Answer Questions:
Q) In the plate becomes water vapour and mixes with the air through a process called?
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Q) Winds come all the way from the Arabian Sea and the Bay of Bengal and they transport the rain clouds. They are?
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Q) The South West Monsoons bring normal rains to?
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Q) The North and Eastern parts of Telangana receive?
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Q) Smaller rivers or streams which join a large river are called?
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Q) Every year, when it rains heavily, the valley is filled with water allowing no permanent trees or plants to grow here. This treeless bed is called?
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Q) The sea coasts are lined with the?
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Q) An instrument by which the rainfall is measured is known as?
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Q) An instrument by which the rainfall is measured is known as?
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Q) Which town has the highest rainfall?
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Q) How do we measure the amount of rainfall?
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Q) What brings them deep inland??
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Short Answer Questions:
Q) How can people meet the challenge of disasters like cyclones and floods?
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Q) How can the people prepare for disasters?
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Q) What is Evaporation?
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Q) What is Winds and Clouds?
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Q) What is Rain gauge?
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Q) What is Tributaries?
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Q) Explain briefly about during Floods?
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Q) Write a short note on Formation of plains?
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Long Answer Questions:
Q) Explain in detail about facing the challenge in Cyclones and Floods?
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Q) Explain in detail about transformation of a stream into a broad river?
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Q) Explain in detail about Flow of Rivers?
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Q) Explain in detail about Rainfall in Telangana?
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Q) Explain in detail about Formation of Clouds and Rain?
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Q) Explain in detail about Flood-Plains and Floods?
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Q) Explain the Delta?
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Q) Write a short note on Rainfall in Telangana?
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Q) Explain the Winds and Clouds?
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RAIN AND RIVERS
Evaporation
  • If you keep some water in a plate, it dries up in a couple of days.
  • In the plate becomes water vapour and mixes with the air through a process called 'evaporation'. So, even when water is not boiling there is evaporation.

Evaporation

  • There are several water bodies on the earth's surface - oceans, rivers, lakes etc.
  • There is constant evaporation of water from these water bodies.
  • In fact, wherever there is moisture, like on wet clothes, evaporation will take place.
  • There is evaporation from our bodies, from trees, plants and soil.
  • The process of evaporation speeds up with the increase in temperature.
Formation of Clouds and Rain

When water vapour rises with hot air and reaches high up in the sky, it gets cooled. This is because the atmosphere gets cooler as we rise above the surface of the earth. With the cooling, water vapour is transformed into tiny water droplets. These droplets gather around minute dust or smoke particles in the air and gradually increase in size. These small drops of water gather to form the clouds.



Formation of clouds

As the clouds continue to rise upwards, it gets cooler and more droplets are formed. The droplets come together to form bigger drops. As they get heavier, it gets more and more difficult for them to remain in the air and so they begin to fall as rain drops.


Winds and Clouds

winds come all the way from the Arabian Sea and the Bay of Bengal and they transport the rain clouds. They are called 'Monsoon winds'. They are also called 'south- west monsoon winds' as they blow from that direction. These winds blow only in the summer. There are two arms of the monsoon winds: one blows from the Arabian Sea and the other from the Bay of Bengal.



Winds and Clouds
Rainfall in Telangana

The South West Monsoons bring normal rains to Telangana. The North and Eastern parts of Telangana receive heavy rainfall. Large areas in the Telangana Plateau receive low rainfall. Mahaboobnagar district receives very little rainfall in Telangana State.



Rainfall in Telangana

The mountain ranges like the Western Ghats come in the path of rain - bearing winds and cause them to rise. Rising air cools down and the water vapour condenses faster. Further ascent leads to rainfall. This type of rainfall is common in the mountainous regions.

The direction of the winds reverses after October as the winds begin to blow from the Bay of Bengal towards south west . This causes very little rains in October and November in Telangana region. This is called North East Monsoons or the Retreating Monsoons.


Rain gauge

Rain Gauge

An instrument by which the rainfall is measured is known as 'Rain gauge'. The amount of rainfall for a unit area is measured in centimeters.When it rains, the water level in the bottle rises. Measure the height of water with the help of a scale and you will get the rainfall in Centimetres for your area during the period you had kept the bottle in the open.


Flow of Rivers

When the water that falls on the earth, some of it percolates into the soil, some flows on the surface of the land and the rest becomes water vapour and mixes with air.



Flowing River
Rivers

Water flows in small streams from the mountain slopes during the rainy season.When it rains, water flows down the same channels. In this way, river courses and river valleys are formed.


Transformation of a stream into a broad river

Tributaries:

A river usually starts in the form of a thin stream. As it flows further, it gets bigger and broader. This happens because many small streams join it as the stream flows. Smaller rivers or streams which join a large river are called 'tributaries'.



Tributaries
Formation of plains:

As the river becomes bigger and broader, its flow gets slower. It starts depositing the silt and sand it has carried, on its bed and banks. This causes the formation of plains.


Delta:

When the speed of water in the river decreases and is no longer able to carry the silt and sand. It deposits them on its own course, which then gets filled up. When flood waters come again, they have to cut through new channels to reach the sea. Thus, towards the end of its journey to the sea, a river forms a delta. River Krishna and Godavari form deltas in the Eastern Coast.



Delta
Flood-Plains and Floods

Every year, when it rains heavily, the valley is filled with water allowing no permanent trees or plants to grow here. This treeless bed is called the flood-plain of the river. All major rivers have their flood plains.



Flood plains

Floods are often caused by sudden increase in the volume of water reaching a river. Vegetation allows the water to flow slowly into the river, thus preventing sudden flooding. It also helps to increase the amount of water which goes into the soil.


Whenever there is heavy rainfall, the rainwater rapidly flows down the slopes of the mountains and fills up the flood plain of the river. The waters also bring a very large quantity of silt and deposit it on the riverbed. This results in frequent floods which cause heavy damage to life and property along the river.


Facing the challenge in Cyclones and Floods

When heavy winds blow from the sea, heavy rains lash the lands, and high waves make the sea very unsafe.The sea coasts are lined with the huts of poor fisher folk and the low lands of the towns and villages, which get flooded, are usually inhabited by the slums of the poor. The people who live in high cement concrete buildings are able to store food, water etc. for many days. Thus, we can see that disasters affect the poorest the most.Usually, immediately after the flood waters recede, all sources of water are polluted and become unsafe for drinking. But, the poor are forced to use the polluted water and face the risk of several diseases like cholera, dysentery, jaundice etc.



Floods

While the immediate damage of the cyclones is also heavy - like loss of lives, crops, houses etc., more importantly they also cause long term damages.


How can people meet the challenge of disasters like cyclones and floods?

It is possible to predict the possibilities of natural disasters like cyclones and floods. Governments thus put these systems in place and inform people about the possibility of disasters.



Cyclone
How can the people prepare for disasters?
  • 1. In case of a cyclone/flood warning, ensure that everyone is alerted. This is usually done through loudspeakers or by going from door to door.
  • 2. Emergency kits should contain important papers, some food, some money and emergency telephone numbers.
  • 3. In case of a cyclone, one should seek the nearest refugee camp.
  • 4. The walls of the house, roofing, doors and windows should be strengthened.
  • 5. Store adequate drinking water and food grains in waterproof bags.
  • 6. Move to a pucca building if you feel your house is not strong enough.
  • 7. If the cyclone strikes while you are in a vehicle, stop but keep away from the seashore, trees, electric poles and other objects.
During Floods:
  • 1. Avoid entering floodwaters. If you have to enter, wear proper protection for your feet and check the depth and current with a stick. Stay away from water with over kneedeep depth.
  • 2. Boil tap water before drinking.

Disaster after Cyclone
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