Drainage: NBSE class 9 social science chapter 7 answers

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Get here solutions, questions, answers, and notes of chapter 7: Drainage which is a part of social science class 9 syllabus of students studying under the Nagaland Board of School Education. However, these notes should be used only for references and additions/modifications should be made as per the requirements.


The term drainage describes the river system of an area. Small streams flowing from different directions come together to form the main river, which ultimately drains into a large water body such as a lake or a sea or an ocean. The area drained by a single river system is called a drainage basin.

A closer observation on a map will indicate that any elevated area, such as a mountain or an upland, separates two drainage basins. Such an upland is known as water divide. The drainage systems of India are mainly controlled by the broad relief features of the subcontinent.

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Textual questions and answers

Choose the correct answer

1. In which of the following states is the Wular lake located?

(a) Rajasthan (b) Punjab (c) Uttar Pradesh (d) Jammu and Kashmir

Answer: D. Jammu and Kashmir

2. Why is the Godavari River sometimes referred to as the “Dakshin Ganga”?

(a) Due to its spiritual significance (b) Because it flows northwards (c) It is the longest river in India (d) It flows through the Himalayas

Answer: A. Due to its spiritual significance

3. The river Narmada has its source at

(a) Satpura (b) Amarkantak (c) Brahmagiri (d) Slopes of the Western Ghats

Answer: B. Amarkantak

4. Which one of the following lakes is a salt water lake?

(a) Sambhar (b) Wular (c) Dal (d) Gobind Sagar

Answer: A. Sambhar

5. Which of the following statements about the above drainage pattern is incorrect?

(a) This pattern develops in a region made of rocks having a uniform structure (b) There is a single main stream with tributaries joining like the branches of a tree (c) The direction of the river and its tributaries are determined by the slope (d) The river flows outward forming a pattern like the spokes of a wheel

Answer: B. There is a single main stream with tributaries joining like the branches of a tree

6. Consider the statements given below and choose the correct answer.

Statement I: The Indus is about 2900 km long.
Statement II: It originates near Mansarovar lake.

(a) Statement (I) is correct and (II) is incorrect (b) Statement (I) is incorrect and (II) is correct (c) Both (I) and (II) are incorrect (d) Both (I) and (II) are correct

Answer: D. Both (I) and (II) are correct

Very short answer type questions

1. What is a drainage basin.

Answer: The area drained by a single river system is called a drainage basin.

2. Where do the following rivers originate?
(a) Kaveri (b) Brahmaputra (c) Mahanadi (d) Tapi

Answer: (a) Brahmagir Hills, ht. 1,341 m.

(b) About 100 km S.W. of Mansarovar ht. 5,150 m.

(c) Raipur district, Chhattisgarh ht. 442 m.

(d) Rises in Betul district.

3. What is a watershed?

Answer: Watershed is the boundary between two rivers.

4. What is the radial pattern of rivers?

Answer: This has the streams flowing in different directions from a central peak or dome-like structure.

5. Name the different stages of rivers.

Answer: The different stages of rivers are:

i. Source of river
ii. Upper course
iii. Middle course
iv. Oxbow lake
v. Lower course
vi. Delta

6. Where do the river Indus and Ganga have their origin?

Answer: Indus has its origins in the Himalayas of western Tibet, near the lake Mansarowar. The Ganga rises in the Himalayas on the Indian side of the Tibet border.

Short answer type questions.

1. Differentiate between dendritic and trellis pattern of rivers.

Answer: A dendritic patter: This consists of a single mainstream with tributaries joining like the branches of a tree.

A trellis pattern: This is a rectangular pattern formed when a long river is joined by short flowing streams, approximately at right angles.

2. Give any three characteristics of Himalayan rivers.

Answer: Three characteristics of Himalayan rivers are:

i. These rivers have large basins, e.g. Indus Basin.
ii. The rivers passing through the Himalayas create spectacular gorges.
iii. The steep rock-sided deep valleys were created by the down-cutting of the river during the period of the Himalayan uplift.

3. Why are rivers important for the country’s economy?

Answer: Rivers are important for the country’s economy because of the following reasons:

i. River valleys provided easy routes and fertile land. This helps in the transportation of goods and agriculture.
ii. Rivers are needed for hydroelectric projects which powers the country.

Long answer type questions

1. What is the difference between the peninsular rivers and Himalayan rivers?

Answer: The difference between the peninsular and Himalayan rivers are as follows:

Peninsular rivers Himalayan rivers
Most of these rivers are seasonal and their flow depends on rainfall.These rivers are perennial as they receive water from rainfall and melting ice all the time.
The gentler slopes cause a low intensity of erosional activity as compared to other rivers.These rivers carry out intensive erosional activities upstream and also carry huge loads of sand and silt.
These rivers do not have many meanders as the hard rock bed and lack of silt and sand does not allow them.When in the plains, these rivers form large meanders and depositional features such as flood plains, river cliffs and levees.

2. Write notes on (i) Ganga System (ii) Brahmaputra System (iii) Indus System.

Answer: (i) The Ganga System: The length of the river Ganga is 2510 km. Rising in the Himalayas on the Indian side of the Tibet border, the Ganga’s five headstreams Bhagirathi, Alaknanda, Mandakini, Dhauliganga and Pindar have their origins in Uttarakhand. The Alaknanda and Bhagirathi meet at Devaprayag to form the Ganga. In Bangladesh, Brahmaputra joins Ganga to form the combined stream called the Padma.

(ii) The Brahmaputra System: The Brahmaputra or Yarlung Zangbo is one of the great rivers of southern Asia. The river’s source lies in the Chemayungdung Glacier. The river flows for nearly 1,126 km in an easterly direction. Throughout its upper course, the river is generally known as the Tsangpo. Near Sadiya, Assam, the Dihang changes course to the southwest and is known as the Brahmaputra. After flowing 800 km in this direction it turns south again, going through Bangladesh.

(iii) The Indus System: The Indus is approximately 2900 kilometres long. Its sources are in western Tibet’s Himalayas, near Lake Mansarowar. It winds its way through Ladakh. It is joined by various tributaries at Gilgit. Attock is where it emerges from the mountains. The Indian states of Jammu and Kashmir, Himachal Pradesh, and Punjab make up a third of the Indus Basin. The remainder is located in Pakistan. The Indus has a drainage area of around 1,165,500 square kilometres, with 453,250 square kilometres in the Himalayan ranges and foothills and the rest in Pakistan’s semi-arid plains. It is one of the world’s longest rivers. The Sutlej, Ravi, Chenab, Jhelum, and Beas are five of its tributaries.

3. Suppose, you are travelling from Haridwar to Siliguri along the foothills of the Himalayas. Name the important rivers you will come across. Describe the characteristics of any one of them.

Answer: Travelling from Haridwar to Siliguri along the foothills of the Himalayas, you would encounter several major rivers that are part of the rich and extensive river systems of the region. These include the Ganga, Yamuna, and the Brahmaputra, among others.

The Ganga, also known as the Ganges, is particularly notable among these. Originating from the Gangotri Glacier in the Uttarakashi district of Uttarakhand, the river travels through the plains of North India, flowing southeast through the Gangetic Plain of North India into Bangladesh, where it empties into the Bay of Bengal. The Ganga is sacred to Hindus, and its water is considered purifying. It supports some of the most densely populated areas in the world, with millions depending on it for their daily water needs.

The Ganga is characterised by its extensive basin, which is the largest river basin in India, covering more than a million square kilometres. It is a lifeline to millions of Indians who live along its course and depend on it for their daily needs. The river is known for its strong religious significance as well as its pivotal role in agriculture, particularly through its fertile plains. However, it is also one of the world’s most polluted rivers, with severe pollution threatening the health of humans and wildlife dependent on it. Efforts to clean and rejuvenate the Ganga have been ongoing for decades, highlighting its environmental and cultural importance.

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1 thought on “Drainage: NBSE class 9 social science chapter 7 answers”

  1. Long answer type questions question number 2 point number 3…
    The question is asking for indus system but instead peninsular river is given..
    Can you please give notes for the indus system?

    Editor’s response:
    Thank you for pointing out the mistake. It has been corrected.

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