WBBSE Solutions For Class 7 Geography Chapter 5 River Topic A Concept Of River

WBBSE Chapter 5 River Topic A Concept Of River Long Question And Answers

Question 1. What do you mean by a river? State the general characteristics of a river.
Answer:

River:

A river is a natural course of water that flows through a channel down the slope of the land under the influence of gravity from the source towards the confluence.

• The place of origin of a river is known as its source, the path it follows is called its course and the place where it joins a sea or a lake is called its mouth.
• Usually, a river is either rain-fed or snow-fed and always flows into a sea, lake or another river. Example: Ganga, Brahmaputra, Yamuna, etc.

General Characteristics of a River:

The general characteristics of a river are as follows-

1. A river flows in a specific direction through a valley following the slope of the land.
2. The water flowing through the rivers has natural sources which usually drains into the sea, ocean or any other water body.
3. A river performs three activities-erosion, transportation and deposition along its course and also creates various landforms.
4. Several small streams join together to form the main river and several small streams also branch out from the main river. These are known as tributaries and distributaries respectively.

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Question 2. What is meant by a river basin?
Answer:

River basin:

A total surface area drained by a river and its tributaries and distributaries is called a basin. Each drainage basin is separated topographically from adjacent basins by a watershed.

Example: Ganga Basin is the largest river basin in India.

• Important river basins of the world are- Amazon Basin, Thames Basin (London Basin), Seine Basin (Paris Basin), Ganga Basin, etc.
• Amazon Basin is the largest basin in the world (almost 70.50 lacks sq. km) and Ganga Basin is the largest basin in India (13.2 lacks sq. km).

 

WBBSE Chapter 5 River Topic A Concept Of River Short Question And Answers

Question 1. What do you mean by the source of the river? What is the mouth of a river? Which force helps a river to flow from source to confluence?
Answer:

Source of the river:

• The place where a river originates is called the source of a river. Example-‘Gomukh’ in the Gangotri glacier is the source of the river Ganga.
• The place where a river ends or flows into a sea or bay or lake or any other waterbody is called the mouth of a river.

Example: The Bay of Bengal is the mouth or confluence of the river Ganga.

The gravitational force helps a river to flow from the source of confluence.

Question 2. Prepare a table of the major rivers of the world along with their respective continents and length.
Answer:

Major rivers along with their respective continents and length are tabulated below-

 

Question 3. Why is River Ganga narrow at Haridwar but wide at Diamond Harbour?
Answer:

River Ganga narrow at Haridwar but wide at Diamond Harbour:

River Ganga has its source at Gomukh ice cave near Gangotri Glacier and enters the plain land at Haridwar.

• As the land is very steep and river velocity is high, vertical erosion predominates making the river valley narrow and deep.
• Near Diamond Harbour, River Ganga is at its mouth, and flows into the Bay of Bengal.
• Here, the land slope is gentle and lateral erosion is predominant with little vertical erosion.
• Moreover, many tributaries join River Ganga although its middle course increasing its water content and thus, making the river wide.

 

Question 4. What determines the velocity of river flow?
Answer:

The velocity of river flow:

• The volume of water and river current together determine the velocity of river flow. The unit used to measure river flow is ‘cusec’ or ‘cumec’.
• The unit used to measure the volume of water flowing within a specific area per second is called cusec (cubic feet per second). In the metric system instead of cubic feet, a cubic metre is used for calculation, that is cumec (cubic metre per second).
• Thus, the unit to measure river velocity in a specific area is cusec or cumec.

Question 5. What is a river?
Answer:

River:

A river is a natural course of water that flows through a channel down the slope of the land under the influence of gravity from the source towards the confluence.

• The place of origin of a river is known as its source, the path it follows is called its course and the place where it joins a sea or a lake is called its mouth.
• Usually, a river is either rain-fed or snow-fed and always flows into a sea, lake or another river.

Example: Ganga, Brahmaputra and Yamuna, etc.

Question 6. What do you mean by the source of a river?
Answer:

Source of a river:

• The place of origin of a river is called its source. For example, the source of the River Indus is the Senge Khabab, a spring near Manasarovar in Tibet.
• The source of a river is almost always a highland.

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Question 7. What is meant by the mouth of a river?
Answer:

Mouth of a river:

The place where a river joins a sea, lake or any other waterbody is known as its mouth.

Example: The mouth of the River Ganga is near Sagar Island where it flows into the Bay of Bengal after forming many deltas and distributaries.

Question 8. Define ‘catchment area’.
Answer:

catchment area:

• A river usually originates in the mountains or high plateaus and flows down along the slope towards lowlands under the force of gravity.
• The extensive area over which several small streams or channels and the main river flow is called the catchment area of the river.
• These streams originate from the highlands and join to form a river at the foothills.

Example: The catchment area of River Ganga is in the mountains of Uttarakhand.

Question 9. Define ‘watershed’ or ‘water divide’.
Answer:

‘Watershed’ or ‘water divide’:

• The highland which separates the course of one river system from another is called a watershed or water divide.
• The peak of the highland divides and distributes the water and makes parts of it flow in different directions.
• In most cases, river basins are surrounded by watersheds.

Example: The Central Highlands of India separate the rivers of North and South India.

Question 10. Differentiate between a catchment area and a water divide.
Answer:

The differences between a catchment area and a water divide are as follows-

 

Question 11. What would happen if a water divide gets eroded?
Answer:

A water divide gets eroded:

A water divide separates the course of one river from the other. In case the water divide gets eroded, the two distinct river systems would join as one and the entire volume of water would flow in one direction.

As a result of this increased volume, there would be floods on the river banks.

Question 12. Define the terms ‘tributary’ and ‘distributary’.
Answer:

‘Tributary’ and ‘distributary’:

• The small streams which flow from different source regions and join the main river are called tributaries. Example: River Yamuna is a tributary of the River Ganga.
• Whereas, the small streams which branch off the main river channel and has its mouth somewhere else are called distributaries.
• The water of the main river flows through the distributaries.

Example: River Bhagirathi- Hooghly is a distributary of River Ganga.

Question 13. Define ‘inland river’ and ‘international inland river a river’. Or, What do you mean by ‘International river’? Or, What do you mean by ‘inland river’?
Answer:

A river originating in a highland and flowing into a lake or any waterbody or swamp within the same country is called an inland river.

Example: River Luni of India.

A river which flows through more than one country is called an international river.

Example: River Ganga in India and Bangladesh.

Question 14. Have you ever wondered where does the huge volume of water in a river that you have seen come from?

(ice-melt water/rainwater/water from a waterfall/a lake/ another river)

Answer:

1. Name of the river-Nagar River
2. Location of river-Raiganj

Such a huge volume of water in this river comes from rainwater.

Question 15. What is a perennial river?
Answer:

Perennial river:

A perennial river is a stream or river that has a continuous flow of water in its channel throughout the year. They are fed by the melting snow from glaciers of the high mountains where the streams have their sources.

Example: Ganga, Indus, and Brahmaputra are all perennial rivers.

Question 16. What is a non-perennial river?
Answer:

Non-perennial river:

• A non-perennial river is a river which does not have a continuous flow of water in its channel throughout the year.
• In the summer season, these streams have little water in their channels but in the rainy season, they come alive when rainfall is sufficient to generate run-off.
• These rain-fed rivers generally originate from areas of low elevation such as hills and plateaus and are called non-perennial or seasonal rivers.

Example: Rivers of the western plateau in West Bengal namely Ajoy, Damodar, Mayurakshi, etc. are all non-perennial rivers.

Short Answers on Stages of a River

Question 17. All rivers don’t have water flow throughout the year. Give a geographical explanation.
Answer:

All rivers don’t have water flow throughout the year.

• The volume of water or the water content in various rivers varies. The rivers originating from the high mountains are glacier-fed and thus perennial.
• Whereas, rivers originating from the plateaus are rain-fed and thus remain low in water content in seasons apart from the monsoon.
• Thus the volume of water or water content varies in different rivers throughout the year.

Question 18. What is a river valley?
Answer:

River valley:

• A lowland between two highlands or mountains is called a valley. It may be narrow or wide.
• A number of tributaries in the course of a river determines its width. When a river flows through a valley, it is called a river valley.
• In other words, from source to mouth, the valley confined by lateral banks through which the river maintains its flow is called a river valley.

Question 19. What is a doab?
Answer:

Doab:

• Doab (Do two, ab – water) is a tract of land lying between two rivers. The confluence of any two rivers which have the same slope forms a doab. It is also called an interfluve.
• Silt deposition in a doab makes the land very fertile and suitable for agriculture.

Example: The confluence of River Ganga and River Yamuna near Allahabad. Punjab is situated at the confluence of five rivers.

Question 20. How do the river valleys of perennial and non-perennial rivers form?
Answer:

The rivers of the mountainous regions being perennial form valleys that are very deep and very wide.

Example: The valleys of the River Ganga.

Since the rivers of the plateau region are non-perennial and do not have water throughout the year, the valleys formed are shallow and less wide.

Example:-The valleys of the River Mayurakshi.

WBBSE Chapter 5 River Topic A Concept Of River Very Short Question And Answers

Question 1. What is a natural stream of water regulated by slope called?
Answer: River.

Question 2. What is the place from where a river originates called?
Answer: Source.

Question 3. What is the place where a river flows into the sea, lake or any other waterbody called?
Answer: Mouth.

Question 4. Which is the longest river in the world?
Answer: River Nile.

Question 5. What is a river that flows into a main river called?
Answer: Tributary.

Question 6. What is a river that branches off from and flows away from the main river called?
Answer: Distributary.

Question 7. What is a river which has water throughout the year called?
Answer: Perennial.

Question 8. What is a river which remains dry for the most part of the year known as?
Answer: Non-perennial.

Question 9. What is a river which has its source and mouth within the mainland of the same country called?
Answer: Inland river.

Question 10. What is a river which flows through more than one country known as?
Answer: International river.

Question 11. What is the land in between two rivers called?
Answer: Doab.

Question 12. Give the unit for the volume of water (in cubic centimetres) flowing per second.
Answer: Cusec.

Question 13. Which is the most important river in Oceania?
Answer: Murray-Darling.

Question 14. Why does river water appear muddy in the rainy season?
Answer:

Rainwater carries sand, silt, etc. from the land surface to the river, which mixes with the water making the river water appear muddy.

WBBSE Chapter 5 River Topic A Concept Of River Fill In The Blanks

Question 1. The place where a river originates is called its __________.
Answer: Source

Question 2. Gomukh ice cave of the Gangotri Glacier is the source of River __________.
Answer: Ganga

Question 3. The length of River Nile is __________.
Answer: 6650 km

Question 4. The longest river in India is __________ (length 2,510 km).
Answer: Ganga

Question 5. The longest river in the world is __________ (length 6650 km).
Answer: Nile

Question 6. The volume of water flow transported through a given cross-sectional area of a river at a given rate and time is called __________.
Answer: Discharge

Question 7. The widely used unit to measure river discharge is __________.
Answer: Cusec

Question 8. The largest river basin in the world is formed by the River __________.
Answer: Amazon

Question 9. The area in the highlands from where a river gets its supply of water is called its __________ area.
Answer: Catchment

Question 10. The highland which separates the course of one river system from another is called a __________.
Answer: Watershed

Question 11.The watershed separating the North Indian and South Indian rivers is called __________.
Answer: Central Highlands of India

Question 12. Channels of water branching from the main river are __________.
Answer: Distributaries

Question 13. River __________ is an inland river of India.
Answer: Luni

Question 14. The meeting point of the two rivers is known as their __________.
Answer: Confluence

Question 15. The land in between two rivers is called a __________.
Answer: Doab

Question 16. With the decrease in the slope of the land, the river’s velocity __________.
Answer: Decreases

WBBSE Chapter 5 River Topic A Concept Of River True Or False

Question 1. The source of the River Ganga is the Gangotri Glacier.
Answer: True

Question 2. River Mahananda is a tributary of River Ganga.
Answer: True

Question 3. The highland which separates the course of one river system from another is called a river valley.
Answer: False

Question 4. The surface area covered by a river, its tributaries and distributaries is called the watershed.
Answer: False

Question 5. The land in between two river valleys is called a catchment area.
Answer: False

Question 6. The River Nile of Egypt is the longest river in the world.
Answer: True

Question 7. The Yangtze is the longest river in Asia.
Answer: True

Question 8. The number of tributaries of a river is highest in the delta region.
Answer: False

Question 9. The supply of water is maximum in the catchment area of a river.
Answer: True

Question 10. Bhagirathi-Hooghly is the most important distributary of Ganga.
Answer: True

Question 11. Perennial rivers are generally rain-fed.
Answer: False

WBBSE Chapter 5 River Topic A Concept Of River Match The Columns

1.

Answer: 1. B, 2. D, 3. F, 4. C, 5. A, 6. E