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Drainage Detailed Chapter Notes - Social Studies (SST) Class 9


The term "drainage" refers to the river system within a specific area. On a physical map, the convergence of small streams from various directions is evident, forming the main river that eventually empties into a larger water body, such as a lake, sea, or ocean. The region drained by a single river system is termed a "drainage basin." A detailed map examination reveals that elevated features, such as mountains or uplands, act as dividers between two distinct drainage basins.  

Drainage Patterns

The streams within a drainage basin form certain patterns, depending on the slope of the land, underlying rock structure as well as the climatic conditions of the area. These are dendritic, trellis, rectangular, and radial patterns. 

  • The dendritic pattern develops where the river channel follows the slope of the terrain. The stream with its tributaries resembles the branches of a tree, thus the name dendritic. 
  • A river joined by its tributaries, at approximately right angles, develops a trellis pattern. A trellis drainage pattern develops where hard and soft rocks exist parallel to each other. 
  • A rectangular drainage pattern develops on a strongly jointed rocky terrain. 
  • The radial pattern develops when streams flow in different directions from a central peak or dome-like structure.

A combination of several patterns may be found in the same drainage basin.

Types of Drainage PatternsTypes of Drainage Patterns

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Drainage System in India

The Drainage systems of India are mainly controlled by the broad relief features of the subcontinent. accordingly, the Indian rivers are divided into two major groups:

(i) The Himalayan Rivers and                                                  
(ii) The Peninsular Rivers.

Drainage Detailed Chapter Notes | Social Studies (SST) Class 9

Drainage Detailed Chapter Notes | Social Studies (SST) Class 9

The Himalayan Rivers

The major Himalayan Rivers are the Indus, the Ganga and the Brahmaputra. These rivers are long and are joined by many large and important tributaries.

The Indus River System

The river Indus rises in Tibet, near Lake Mansarovar. Flowing west, it enters India in the Ladakh district of Jammu and Kashmir. Several tributaries, the Zaskar, the Nubra, the Shyok and the Hunza, Join it in the Kashmir region. The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock. The  Satluj, the Beas, the Ravi, the Chenab and the Jhelum join together to enter the Indus near Mithankot in Pakistan. Beyond this, the Indus flows southwards eventually reaching the Arabian Sea, east of Karachi. The Indus Plain has a very gentle slope. With a total length of 2900 km, the Indus is one of the longest rivers in the world. a little over a third of the Indus Basin is located in India in the states of Jammu and Kashmir, Himachal Pradesh, and Punjab and the rest are in Pakistan.

Drainage Detailed Chapter Notes | Social Studies (SST) Class 9

Indus River System

  • The Jhelum, an important tributary of the Indus, rises from a spring at Verinag situated at the foot of the Pir Panjal in the southeastern part of the valley of Kashmir.
  • The Chenab is the largest tributary of the Indus. it is formed by two streams, the Chandra and the Bhaga, which join at Tandi near Keylong in Himachal Pradesh. hence, it is also known as Chandrabhaga. The river flows for 1,180 km before entering Pakistan.
  • The Ravi is another important tributary of the Indus. it rises west of the Rohtang pass in the Kullu hills of Himachal Pradesh and flows through the Chamba valley of the state.
  • The Beas is another important tributary of the Indus, originating from the Beas Kund near the Rohtang Pass at an elevation of 4,000 m above the mean sea level.
  • The Satluj originates in the Rakas Lake near Mansarovar at an altitude of 4,555 mt. In Tibet, where it is known as Langchen Khambad.

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What is the term used to describe the river system within a specific area?
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The Ganga System

  • The headwaters of the Ganga called the ‘Bhagirathi is fed by the Gangotri Glacier and Joined by the Alaknanda at Devprayag in Uttaranchal. At Haridwar, the Ganga emerges from the mountains onto the plains.
  • The Ganga is joined by the many tributaries from the Himalayas such as the Yamuna, the Ghaghara, the Gandak and the Kosi. The river Yamuna rises from the Yamunotri Glacier in the Himalayas and meets the Ganga at Allahabad. The Ghaghara, the Gandak and the Kosi rise in the Nepal Himalaya.
  • The main tributaries from the peninsular uplands are the Chambat, the Betwa and the son.
  • The Ganga flows eastwards till Farakka in West Bengal, the northernmost point of the Ganga delta. The river bifurcates here; the Bhagirathi-Hooghly flows southwards through the deltaic plains to the Bay of Bengal. The mainstream flows southwards into Bangladesh and is joined by the Brahmaputra. Further downstream, it is known as the Meghna and finally flows into the Bay of Bengal. The delta formed by these rivers is known as the Sunderban Delta.
    Ganga River System and Brahmaputra River System
    Ganga River System and Brahmaputra River System

The Brahmaputra System

  • The Brahmaputra rises in Tibet east of Mansarovar Lake. It is slightly longer than the Indus. It flows eastwards parallel to the Himalayas.
  • On reaching the Namcha Barwa (7757 m), it takes a ‘U’ turn and enters India in Arunachal Pradesh through a gorge. Here, it is called the Dihang and it is joined by the Dibang, the Lohit, the Kenula and many other tributaries to form the Brahmaputra in Assam.
  • In India, it passes through a region of high rainfall. Here the river carries a large volume of water and a considerable amount of silt. The Brahmaputra has a braided channel in its entire length in Assam and forms many riverine islands (Majuli, in the Brahmaputra River, is the largest inhabited riverine island in the world).
  • During the rainy season, the river overflows its banks, causing widespread devastation due to floods in Assam and Bangladesh. Unlike other north Indian rivers, the Brahmaputra is marked by huge deposits of silt on its bed causing the river bed to rise. The river also shifts its channel frequently.

Question for Detailed Chapter Notes - Drainage
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The Peninsular Rivers

The Peninsular drainage system is older than the Himalayan one. This is evident from the broad, largely-graded shallow valleys, and the maturity of the rivers. Peninsular rivers are characterized by fixed course, absence of meanders, small drainage basins and non-perennial flow of water. The main water divide in peninsular Indian is formed by the Western Ghats. Most of the major rivers of the Peninsula flow eastwards and drain into the Bay of Bengal. The Narmada and the Tapi which flow through the rift valley are exceptions.

The Narmada Basin

  • The Narmada originates on the western flank of the Amarkantak plateau at a height of about 1, 057m. It falls into the Arabian Sea south of Bharuch. The Sardar Sarovar Project has been constructed on this river.
  • Flowing in the rift valley between the Satpura in the south and the Vindhya range in the north the Narmada creates many picturesque locations. the ‘Marble Rocks’, near Jabalpur where the Narmada flows through a deep gorge, and the ‘Dhuadhar Falls’ where the river plunges over steep rocks, are some of the notable ones.
  • All the tributaries of the Narmada are very short and most of these join the mainstream at right angles. The Narmada basin covers parts of Madhya Pradesh and Gujarat.

The Tapi Basin

The Tapi originates from the Satpura ranges in the Betul district of Madhya Pradesh. nearly 79 percent of its basin lies in Maharashtra, 15 percent in Madhya Pradesh, and the remaining 6 percent in Gujarat. The Tapi flows in a rift valley parallel to the Narmada but it is much shorter in length.

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Which river is known as the Dakshin Ganga?
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The Godavari Basin

  • The Godavari is the largest peninsular river system. it rises from the slopes of the Western Ghats in the Nashik district of Maharashtra. its length is about 1500 km.
  • Because of its length and the area it covers, it is also known as the Dakshin Ganga.  its basin cover parts of Maharashtra, Madhya Pradesh, Orissa and Andhra Pradesh.
  • The Godavari is joined by a number of tributaries such as the Penganga, the Preheat, the Manjira, the Wainganga, and the Wardha. It finally drains into the Bay of Bengal.
  • The Mahanadi rises near Sihawa in the Raipur district of Chattisgarh and runs through Orissa to discharge its water into the Bay of Bengal. fifty-three percent of the drainage basin of this river lies in Madhya Pradesh and Chattisgarh, while 47 percent lies in Orissa.
  • The Krishna is the second-largest east-flowing peninsular river which rises near Mahabaleshwar in Sahyadri. Its total length is 1,401 km. the Koyna, the Tungbhadra, and the Bhima are its major tributaries. 
  •  The Kaveri rises in Brahmagiri hills (3,341m) of Kogadu district in Karnataka. Since the upper catchment area receives rainfall during the southwest monsoon season (summer) and the lower part during the northeast monsoon season (winter), the river carries water throughout the year with comparatively less fluctuation than the other Peninsular rivers. Its important tributaries are the Kabini, the Bhavani and the Amravati.

Drainage Detailed Chapter Notes | Social Studies (SST) Class 9

 Drainage Detailed Chapter Notes | Social Studies (SST) Class 9


  • Sambhar Lake is the largest inland salt lake in India situated in Rajasthan. Other salt lakes in Rajasthan are Didwana, Degana, Pachadra, Kucha man, and Lunkaransar.
  • Lunar Lake situated in Maharashtra is a crater lake.
  • Chilka Lake situated in the Puri district of Orissa & south of the Mahanadi delta is the biggest lake in the country.

Loktak Lake Loktak Lake 

  • Kolleru Lake is a deltaic Lake of Andhra Pradesh situated between the Krishna & Godavari delta.
  • Pulicat Lake situated in the north of Chennai is a shallow lagoon. it has been barred by a long sandpit which is actually Sri Harikota island.
  • Loktak Lake situated in Manipur is the largest freshwater lake in North East India. Keibul lamjao, the only floating National Park of the country is situated here.
  • Vembanad Lake is a lagoon in Kerala and is an important tourist spot. coconut islands are located in it.
  • Gohna Lake situated near Devprayag in Garhwal has been formed by a huge landslide across a tributary of the Ganga.
  • Wular Lake & Dal Lake are tectonic lakes formed by faulting activities.

Question for Detailed Chapter Notes - Drainage
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What is the main cause of river pollution mentioned in the passage?
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Importance of Lakes

  • Lakes are very important to man.
  • A lake helps to regulate the flow of a river.
  • During heavy rainfall they prevent flooding and during the dry season, they help maintain an even flow of water.
  • Lakes are also used for developing hydel power.
  • Lakes are a valuable source of water.
  • They moderate the climate of the surrounding areas.
  • They maintain the aquatic ecosystem.
  • They enhance natural beauty, helps in developing tourism.
  • They provide recreation through boating and swimming.

Role of Rivers 

  • Rivers have formed fertile northern plains and deltas containing alluvial soils which are the most productive agricultural lands of India.
  • Water from rivers is a basic natural resource essential for the survival of humans, plants and animals, for agricultural and industrial activities.
  • The banks of rivers have been cradles of civilization all over the world. For example Indus civilization in India.
  • Rivers have provided cultural and economic progress since ancient times.
  • Rivers provide an inland transportation system. They also dilute and transport wastes from settlements.
  • Industrial; development has flourished along rivers. Most industrial processes depend on water as raw material, as a coolant, and for generating hydroelectricity.

Question for Detailed Chapter Notes - Drainage
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What is the world's largest and fastest-growing delta?
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River Pollution

Rapidly growing domestic, Municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water. Today more and more water is drained out of the rivers. It has resulted in reducing their volume. A heavy load of untreated sewage and industrial effluents is emptied into the rivers.

  • This affects not only the quality of water but also the self-cleansing capacity of the river. For example, if there is adequate streamflow, the Ganga water is able to dilute and assimilate pollution loads of large cities within 20 km.
  • The result is that the pollution level of many rivers is rising.
  • Concern over the rising pollution of our rivers has launched of various action plants to clean the rivers.

National River Conservation Plan (NRCP)

  • The activities of Ganga Action Plan (GAP) phase-l were started in 1985.
  • They declared closed on 31st March 2000.
  • The steering committee of the National River Conservation Authority reviewed the progress of the GAP and necessary corrections were made on the basis of lamed and experiences gained from GAP phase l.
  • They have been applied to the major polluted rivers of their country under the NRCP.
  • The Ganga Action Plan (GAP) Phase-ll has been merged with the NRCP. The expanded NRCP now covers 152 towns located along 27 interstate rivers in 16 states. Under this action plan, pollution abatement work is being taken up in 57 towns. a total of 215 schemes of pollution abatement have been sanctioned. so far, 69 schemes have been completed under this action plan. A million liter of sewage is targeted to be intercepted, diverted, and treated.

[Intext Question]

For a detailed understanding of this chapter, check the video below.

Some Interesting Knowledge

  • The world’s largest drainage basin is the River Amazon which is situated in South America.
  • According to the regulation of the Indus Water Treaty (1960), India can use only 20 per cent of the total water carried by the Indus River system. This water is used for irrigation in the Punjab, Haryana, and the southern and western parts of Rajasthan.
  • The Sundarban Delta derived its name from the Sundari tree which grows well in marshland. it is the world’s largest and fastest-growing delta. it is also the home of the Royal Bengal Tiger.
  • The Brahmaputra is known as the Tsang Po in Tibet and Jamuna in Bangladesh.
  • The river Kaveri is the second biggest waterfall in India. it is known as Sivasmudram. the fall supplies hydroelectric power to Mysore, Bangalore, and the Kolar Gold Field.
  • 71 percent of the world’s surface is covered with water, but 97 percent of that is saltwater. Of the 3 percent that is available as freshwater, three-quarters of it is trapped as ice.
  • Lakes of large extent are called the seas, like the Caspian, the Dead, and the Aral seas.
The document Drainage Detailed Chapter Notes | Social Studies (SST) Class 9 is a part of the Class 9 Course Social Studies (SST) Class 9.
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FAQs on Drainage Detailed Chapter Notes - Social Studies (SST) Class 9

1. What is the significance of the drainage system in India?
Ans. The drainage system in India is significant because it plays a crucial role in the country's agricultural, industrial, and domestic activities. It helps in the distribution of water for irrigation, provides a means of transportation, and supports the generation of hydroelectric power.
2. What are the Himalayan rivers and why are they important?
Ans. The Himalayan rivers are rivers that originate in the Himalayan mountain range. They are important because they provide a constant water supply to the northern plains of India, which are highly dependent on agriculture. These rivers also support hydropower generation and serve as transportation routes.
3. Which rivers are part of the peninsular river system in India?
Ans. The peninsular rivers in India include rivers such as the Godavari, Krishna, Mahanadi, Cauvery, and Narmada. These rivers flow through the Deccan Plateau and are mostly rain-fed, making them important sources of water for irrigation and hydropower generation in the region.
4. What is the role of rivers in India?
Ans. Rivers in India play a vital role in the country's economy and society. They provide water for irrigation, enabling agriculture to thrive. Rivers also serve as a means of transportation, facilitating trade and commerce. Additionally, they support the generation of hydroelectric power and provide a habitat for various flora and fauna.
5. How does river pollution affect India's water resources?
Ans. River pollution in India has a detrimental impact on the country's water resources. It leads to the contamination of water, making it unsafe for drinking and irrigation purposes. It also harms aquatic life, disrupts the ecological balance, and contributes to the spread of waterborne diseases. River pollution poses a significant threat to both human health and the environment.
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