NCERT Notes for Class 9 Social Science Chapter 3 Drainage

The phrase drainage refers to an area’s river system. Small streams moving in various directions join to create the main river, which finally flows into a big body of water such as a lake, sea, or ocean. CBSE Notes Class 9 Geography Chapter 3 on Drainage can assist you in understanding India’s drainage system. At the chapter’s conclusion, you will also learn about lakes, their significance, the economic function of rivers, and river pollution.

CBSE Class 9 Social Science notes will assist students in studying the topic thoroughly and clearly.

These CBSE Class 9 Social Science notes were written by subject experts who made the study material very basic, both in terms of language and format.

Drainage Systems In India

The Peninsular Rivers

  1. These rivers are seasonal in nature, since their flow is controlled by rainfall.
  2. The big rivers even decreased the flow of water through their channels during the dry season.
  3. These rivers have shorter and shallower courses than Himalayan rivers.

The majority of Peninsular rivers originate in the Western Ghats and flow towards the Bay of Bengal, including the Mahanadi and Godavari rivers, although other rivers start in the central highlands and travel westward into the Arabian sea.

The Himalayan Rivers

  1. These rivers are generated by rain and melting snow from the high mountains.
  2. The majority of Himalayan rivers are perennial, which means they get water all year.
  3. The Indus and Brahmaputra rivers are significant Himalayan rivers. They originate in the mountains to the north.
  4. These rivers are lengthy and are connected by many big and major streams.
  5. They’ve carved gorges into the mountains. From their source to the sea, the Himalayan rivers have a lengthy journey.
  6. These rivers have a high rate of erosion in their upper reaches and carry huge loads of silt and sand.
  7. Throughout their middle and lower courses in the floodplains, these rivers produce meanders, Ox-bow lakes, and other depositional features. These rivers have extensive deltas.

The Peninsular Rivers

Godavari, Mahanadi, Krishna, and Kaveri are the Peninsula’s principal rivers. They drain into the Bay of Bengal, flowing eastward. At the mouths of these rivers, deltas form. Only the Tapi and the Narmada are lengthy rivers that travel west and form estuaries. Peninsular rivers have very limited drainage basins.

The Mahanadi Basin

  1. The Mahanadi originates in the Chhattisgarh highlands and flows through Odisha to the Bay of Bengal.
  2. The river is around 860 kilometres. Maharashtra, Chhattisgarh, Jharkhand, and Odisha share its drainage basin.

The Krishna Basin

  1. The Krishna river starts at Mahabaleshwar in the Western Ghats.
  2. It runs into the Bay of Bengal, where it forms a sizable delta.
  3. It is approximately 1400 kilometres long.
  4. Its tributaries are the Tungabhadra, Koyana, Ghatprabha, Musi, and Bhima.
  5. It has a basin that stretches through Maharashtra, Karnataka, and Andhra Pradesh.

The Kaveri Basin

  1. It starts in the Western Ghats’ Brahmagiri mountain and runs into the Bay of Bengal south of Cuddalore in Tamil Nadu.
  2. Amravati, Bhavani, Hemavati, and Kabini are its major tributaries.
  3. The river is around 760 kilometres long.
  4. In portions of Karnataka, Kerala, and Tamil Nadu, the Kaveri drains.
  5. The river Kaveri creates India’s second largest waterfall, Sivasamudram.

The Narmada Basin

  1. The Narmada starts in Madhya Pradesh’s Amarkantak hills. It runs westward in a rift valley created by a geological fault.
  2. All of Narmada’s tributaries are quite short in length.
  3. Most of its tributaries form right angles to the mainstream.
  4. Parts of Madhya Pradesh and Gujarat are included in the Narmada basin.
  5. Madhya Pradesh’s Narmada River Conservation Mission is being carried out through a scheme called Namami Devi Narmade.

The Tapi Basin

  1. The Tapi starts in the Satpura mountains of Madhya Pradesh’s Betul district.
  2. It runs parallel to the Narmada in a rift valley, but is significantly shorter in length.
  3. It is divided among sections of Madhya Pradesh, Gujarat, and Maharashtra.
  4. It measures around 724 kilometres in length.

The Godavari Basin

  1. It is the Peninsular rivers’ longest river (about 1500 kilometres), with the biggest drainage basin and delta. Due to its length and breadth, it is also known as the Dakshin Ganga.
  2. The Godavari river starts on the Western Ghats in Maharashtra’s Nashik district.
  3. The Godavari has several tributaries, including the Manjra, Wainganga, and Penganga rivers, as well as the Puma, Wardha, and Pranhita.
  4. Maharashtra, Madhya Pradesh, Odisha, and Andhra Pradesh are all included in the Godavari basin. It eventually flows into the Bay of Bengal.

The Brahmaputra River System

  1. The Brahmaputra river starts in Tibet, east of the Mansarovar lake. It runs eastward parallel to the Himalayas until it reaches Namcha Barwa (7757m), at which point it does a U-turn and enters India via a canyon in Arunachal Pradesh. Here, I am referred to as Dihang.
  2. It takes a little amount of silt and water from Tibet because of the area’s cold and dry climate. It carries a lot of water and a lot of silt in Assam due to the state’s heavy rainfall.
  3. It is somewhat longer than the Indus and runs for the most of its length outside of India. In Assam, it is joined by many tributaries such as the Dibang, Lohit, and others to create the Brahmaputra.
  4. In Assam, it has a braided channel that forms many riverine islands. It is responsible for the formation of Majuli island, the world’s biggest riverine island.
  5. Each year, the Brahmaputra exceeds its banks, producing severe flooding in Assam and Bangladesh.

The Indus River System

  1. It is 2900 kilometres long in total, making it one of the world’s longest rivers.
  2. Near Mansarovar lake, the Indus river starts in China (Tibet). It flows westward and reaches India in the Jammu and Kashmir province of Ladakh.
  3. In the Kashmir area, it is joined by other tributaries, including the Zaskar, Nu bra, Shyok, and Hunza.
  4. The Indus River runs through Baltistan and Gilgit and emerges in Attock from the Himalayas.
  5. The Indus River runs southward till it meets the Arabian Sea east of Pakistan’s Karachi port.
  6. According to the 1960 Indus Water Treaty between India and Pakistan, India is permitted to use just 20% of the water carried by the Indus River System. This water is used for irrigation in Punjab, Haryana, and the southern and western regions of Rajasthan.
  7. One-third of its basin is in India, specifically in the states of Jammu & Kashmir, Himachal Pradesh, and Punjab. The remainder is located in Pakistan.

The Ganga River System

  1. This system originates as the Bhagirathi (Ganga’s Headwaters) from Uttarakhand’s Gangotri glacier. At Devprayag, it is joined with the Alaknanda river to create the Ganga. Its length exceeds 2500 kilometres.
  2. The Ghaghara, Gandak, and Kosi rivers all start in Nepal’s Himalayas.
  3. The Yamuna river starts in the Himalayas at the Yamunotri glacier. It is a right bank tributary of the Ganga. At Allahabad, it joins the Ganga.
  4. The Ganga comes from the mountains onto the lowlands in Haridwar. Its principal tributaries are the Yamuna, the Ghaghara, the Gandak, and the Kosi.
  5. The Chambal, Betwa, and Son are the Ganga’s primary tributaries that start in the Peninsular uplands. These originate in semi-arid regions, have shorter courses, and carry less water.
  6. The Ganga continues eastward till it reaches Farakka in West Bengal. It then splits into two branches and creates the Bhagirathi-Hooghly (also known as Hugli), which flows into the Bay of Bengal.
  7. The Ganga’s main stream enters Bangladesh, where it is joined with the Brahmaputra, which starts in Assam, to create the Meghna.
  8. It runs into the Bay of Bengal, where it forms the Sunderban delta.

Lakes In India

  1. India is filled with lakes. There are both permanent and seasonal lakes.
  2. Only during the monsoon season can seasonal lakes hold water. the lakes found in semi-arid areas’ inland drainage basins, such as the Sambhar salt lake in Rajasthan.
  3. Its water is stored in the formation of salt. Lakes in India are produced by a variety of processes, including glacier and ice sheet movement, wind, river action, and human activity.
  4. A meandering river cutting through a flood plain creates cut-offs that eventually become Ox-bow lakes. In coastal regions, spits and bars create lagoons, as do the Chilika, Pulicat, and Kolleru lakes.

Importance Of Lakes

  1. Lakes help in the regulation of a river’s flow. It avoids floods during periods of heavy rainfall and assists in maintaining an equal flow of water throughout the dry season.
  2. 71% of the earth’s surface is covered by water, yet 97% of that water is salt water. Three-quarters of the 3% available as freshwater is locked as ice.
  3. Additionally, it may be utilised to generate hydroelectricity. It serves to control the surrounding climate, maintain the aquatic environment, improve natural beauty, promote tourist development, and give recreation.
  4. Seas are larger lakes, such as the Caspian, Dead, and Aral seas.

Role Of Rivers In The Economy

  1. Throughout human history, rivers have played an important role. River water is a vital natural resource that is required for a variety of human activities.
  2. They supply water for agriculture, navigation, and fisheries, as well as water for household purposes such as washing, cooking, and drinking.
  3. They also contribute to the generation of hydroelectric electricity.

River Pollution

  1. The increasing demand for water from rivers by domestic, municipal, industrial, and agricultural users has an effect on the water’s quality.
  2. Allowing untreated sewage and industrial waste to enter rivers has an effect on both the water and the river’s ability to self-cleanse.

NCERT Solutions For Class 9 Social Science (Geography) Chapter 3 DRAINAGE

Question 1.

Choose the right answer from the four alternatives given below.

(i) Which one of the following describes the drainage patterns resembling the branches of a tree?

(a) Radial

(b) Dendritic

(c) Centrifugal

(d) Trellis

Ans. (b) Dendritic pattern

In India, rivers that follow dendritic drainage patterns include the Ganga-Brahmaputra, the Indus, Mahanadi, Godavari, and Krishna. These rivers have numerous tributaries and form a structure resembling tree branches.

(ii) In which of the following states is the Wular lake located?

(a) Rajasthan

(b) Uttar Pradesh

(c) Punjab

(d) Jammu and Kashmir

Ans. (d) Jammu and Kashmir state.

(iii) The river Narmada has its source at

(a) Satpura

(b) Brahmagiri

(c) Amarkantak

(d) Slopes of Western Ghats

Ans. (c) Amarkantak

Amarkantak is a pilgrim town and a Nagar Panchayat in the Indian district of Anuppur in Madhya Pradesh. The Amarkantak region is a unique natural heritage site that serves as the juncture of the Vindhya and Satpura Ranges, with the Maikal Hills serving as the fulcrum. This is the source of the Narmada, Son, and Johila rivers.

(iv) Which one of the following lakes is a salt water lake?

(a) Sambhar

(b) Dal

(c) Wular

(d) Gobind Sagar

Ans. (a) Sambhar lake

The Sambhar Salt Lake, India’s largest inland salt lake, is located in Rajasthan, 80 kilometres southwest of Jaipur and 64 kilometres northeast of Ajmer. It surrounds the historic town of Sambhar Lake.

(v) Which one of the following is the longest river of the Peninsular India?

(a) Narmada

(b) Krishna

(c) Godavari

(d) Mahanadi

Ans. (c) Godavari river

The Godavari, India’s second-longest river after the Ganges and third-largest, drains approximately 10% of the country’s total geographical area. Trimbakeshwar, Nashik, Maharashtra is its source. It drains the states of Maharashtra, Telangana, Andhra Pradesh, Chhattisgarh, and Odisha over a 1,465-kilometer stretch.

(vi) Which one amongst the following rivers flows through a rift valley?

(a) Mahanadi

(b) Tungabhadra

(c) Krishna

(d) Tapi river 

Ans. (d) Tapi river

The Tapti River is a river in central India that flows westward from the Narmada River before emptying into the Arabian Sea. The river flows for approximately 724 kilometres through the states of Maharashtra, Gujarat, and Madhya Pradesh.

Question 2.

Answer the following questions briefly.

(i) What is meant by a water divide? Give an example.

Ans: A water divide is an elevated terrain feature, such as a mountain or upland, that separates two drainage basins. Ambala, for example, is the confluence of the Indus and Ganga rivers.

(ii) Which is the largest river basin in India?

Ans: The Ganga river basin is the largest in India. This basin spans nearly 2,500 kilometres.

(iii) Where do the rivers Indus and Ganga have their origin? 

Ans: The Indus River originates in Tibet near Mansarovar Lake. The Ganga River originates on the Himalayan southern slopes at the Gangotri Glacier.

(iv) Name the two headstreams of the Ganga. Where do they meet to form the Ganga?

Ans:The Ganga’s two headstreams are the Bhagirathi and the Alaknanda. They converge at Devprayag in Uttarakhand to form the Ganga.

(v) Why does the Brahmaputra in its Tibetan part have less silt, despite a longer course?

Ans:Due to the region’s cold and dry climate, the Brahmaputra’s Tibetan section carries less water and silt.

(vi) Which two peninsular rivers flow  through trough?

Ans: Two peninsular rivers, the Narmada and the Tapi, pass through the valley.

(vii) State some economic benefits of rivers and lakes. 

Ans. Economic benefits of rivers:

  • Rivers provide access to water, a critical natural resource for a variety of human activities including irrigation, navigation, and hydroelectric power generation.
  • Additionally, they provide cooling to the surrounding environment and aid in the preservation of aquatic ecology.

Economic benefits of lakes:

  • They contribute to river flow regulation by preventing flooding during periods of heavy rainfall and assisting in the maintenance of an even flow of water during the dry season.
  • Additionally, they support aquatic ecology by regulating the surrounding climatic conditions.
  • They promote tourism, which benefits natural beauty and recreational opportunities.
  • Additionally, lakes are used to generate hydroelectricity.

Question 3.

Below are given names of a few lakes of India. Group them under two categories- natural and created by human beings:

(a) Wular 

(b) Dal 

(c) Nainital 

(d) Bhimtal 

(e) Gobind Sagar 

(f) Loktak 

(g) Barapani 

(h) Chilika 

(i) Sambhar 

(j) Rana Pratap Sagar 

(k) Nizam Sagar 

(l) Pulicat 

(m) Nagarjuna Sagar 

(n) Hirakund


Natural Lakes:

(a) Wular 

(b) Dal 

(c) Nainital 

(d) Bhimtal 

(f) Loktak 

(g) Barapani 

(h) Chilika 

(i) Sambhar 

(l) Pulicat

Lakes Created human beings:

(e) Gobind Sagar

 (j) Rana Pratap Sagar 

(k) Nizam Sagar 

(m) Nagarjuna Sagar 

(n) Hirakund

Question 4.

Discuss the significant difference between the Himalayan and the Peninsular rivers.


The Himalayan Rivers 

  • They are never-dying rivers. They get their water from both melted snow and torrential rain.
  • They exhibit massive erosional activity in the upper course.
  • They take a circuitous route from source to mouth.
  • They carry a substantial amount of silt and sand, which is replenished annually by floods.
  • As a result, they contribute to agriculture’s success.
  • The Ganga, Indus, and Brahmaputra are the three major Himalayan rivers.

The Peninsular Rivers

  • They are only available during specific seasons. They rely entirely on rainfall.
  • They take no erosional action in the upper course.
  • Their route is more direct and direct.
  • With no significant plains, these rivers do not carry a lot of silt. Fertile lands are found only in the tiniest delta areas.
  • The Mahanadi, Godavari, Krishna, Kaveri, Narmada, and Tapi are notable Peninsular rivers.

Question 5.

Compare the east-flowing and the west-flowing rivers of the Peninsular plateau.


The East Flowing Rivers

  • Peninsular India’s east-flowing rivers are the Mahanadi, the Godavari, the Krishna, and the Kaveri.
  • These rivers provide water to the Bay of Bengal.
  • These rivers form deltas on the east coast.
  • These rivers have a large and well-developed network of tributaries.

The West Flowing Rivers

  • Peninsular India’s major west-flowing rivers are the Narmada and Tapi.
  • These rivers provide water to the Arabian Sea.
  • These rivers form estuaries along the western seaboard.
  • These rivers do not have an established tributary system.

Question 6.

Why are rivers important for the country’s economy?

Answer: Rivers are beneficial to a country’s economy in several ways:

  • Rivers produce water, a necessary resource for a variety of purposes.
  • Since prehistoric times, riverbanks have attracted settlers. These small towns have developed into colossal metropolises.
  • Rivers provide water for agriculture, navigation, and the generation of hydroelectric power.
  • Rivers have also aided agriculture, the most vital economic sector of any country.
  • Rivers have a calming effect on the climate immediately surrounding them.
  • Additionally, they contribute to the conservation of aquatic ecology.
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