NCERT Class 11 Indian Geography Chapter 3 – Drainage System

NCERT Class 11 Indian Geography Chapter 3 explains the drainage system of India and the origin, course and features of major rivers. In NCERT Class 11 Indian Geography Chapter 3, students study the Himalayan and Peninsular river systems, their tributaries and their role in shaping India’s plains.

NCERT Class 11 Indian Geography Chapter 3 is highly important for CBSE board exams and competitive exams like UPSC and BPSC because map-based and analytical questions are frequently asked from river systems. A clear understanding of NCERT Class 11 Indian Geography Chapter 3 builds a strong base for topics like climate, soils and agriculture. Students should refer to the official NCERT website at for authentic textbooks and syllabus updates.

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1. Introduction

• The flow of water through well-defined natural channels is called Drainage, and the network of such channels is known as a Drainage System.
• The pattern of drainage in an area depends on geological structure, rock type, topography, slope, amount of water and periodicity of flow.
• A river collects water from a specific region known as its Catchment Area, and the total area drained by a river and its tributaries is called a Drainage Basin.
• The boundary separating two drainage basins is known as a Watershed; watersheds are smaller units, while river basins cover larger areas and are useful for micro, meso and macro-level planning.
• On the basis of direction of flow (orientation to sea), Indian drainage is divided into Arabian Sea Drainage and Bay of Bengal Drainage, separated by water divides such as the Delhi Ridge, Aravali Range and Sahyadris (Western Ghats).
• Nearly 77% of India’s drainage area (including rivers like Ganga, Brahmaputra, Mahanadi, Krishna) flows into the Bay of Bengal, while 23% (including Indus, Narmada, Tapi, Mahi, Periyar) drains into the Arabian Sea.
• Based on catchment size, river basins are classified into:
  Major Basins (>20,000 sq km; e.g., Ganga, Brahmaputra, Krishna, Narmada, Tapi, Mahi, Pennar, Sabarmati, Barak),
  Medium Basins (2,000–20,000 sq km; e.g., Kalindi, Periyar, Meghna),
  Minor Basins (<2,000 sq km).
• Important drainage patterns include Dendritic (tree-like; common in Northern Plains), Radial (e.g., rivers from Amarkantak Plateau), Trellis, and Centripetal (rivers flowing into a depression or lake).

2. Drainage systems of india

• The Indian Drainage System consists of numerous large and small rivers, shaped by the evolutionary history of the three major physiographic units — Himalayas, Northern Plains and Peninsular Plateau — and the nature of monsoonal precipitation.
• On the basis of origin, nature and characteristics, Indian drainage is broadly classified into Himalayan Drainage and Peninsular Drainage, which is the most accepted classification system.
• The Himalayan drainage includes the river basins of Indus, Ganga and Brahmaputra, while the Peninsular drainage includes rivers such as Mahanadi, Godavari, Krishna, Kaveri, Narmada and Tapi.
• Although rivers like Chambal, Betwa and Son originate in the Peninsular region, they are part of the Ganga River System, showing complexity in classification.
• The drainage system can also be classified based on the orientation of flow, with rivers draining into the Bay of Bengal (77%) and the Arabian Sea (23%).
• Large rivers originating in the Himalayas are generally perennial due to both snowmelt and rainfall, while many Peninsular rivers are seasonal and dependent mainly on rainfall.
• Major river basins of India include the Ganga Basin, Brahmaputra Basin, Indus Basin, Godavari Basin, Krishna Basin, Narmada Basin and Mahanadi Basin, each supporting large populations and agricultural activities.

3. The Himalayan drainage

• The Himalayan Drainage System mainly includes the river basins of Indus, Ganga and Brahmaputra, and has evolved through a long geological history.
• These rivers are perennial because they are fed by both snowmelt from glaciers and monsoonal rainfall, ensuring continuous flow throughout the year.
• In their mountainous course, they carve deep gorges, form V-shaped valleys, rapids and waterfalls, indicating youthful topography and active erosion.
• Upon entering the plains, these rivers create depositional landforms such as floodplains, ox-bow lakes, braided channels and deltas, particularly visible in the Ganga-Brahmaputra Delta.
• In the Himalayan region, river courses are highly tortuous (irregular) due to tectonic activity, while in the plains they show strong meandering tendencies and frequent course shifting.
• The Kosi River, known as the “Sorrow of Bihar”, frequently changes its course due to heavy sediment deposition brought from the upper Himalayan region.
• The heavy sediment load of Himalayan rivers is due to steep slopes, intense weathering and high rainfall, especially during the South-West Monsoon season.
• Flooding is common in these river systems, producing both positive effects (fertile alluvial soil) and negative effects (loss of life, property and crop damage).

4. Evolution of the Himalayan drainage

• Geologists believe that during the Miocene period (5–24 million years ago), a mighty river known as the Shiwalik or Indo–Brahma River flowed along the longitudinal extent of the Himalayas from Assam to Punjab and Sind, finally draining into the Gulf of Sind.
• Evidence supporting this theory includes the continuity of Shiwalik deposits consisting of sand, silt, clay, boulders and conglomerates, indicating lacustrine (lake) and alluvial origin.
• Over time, the Indo–Brahma River was dismembered into three major river systems:
  the Indus system in the west,
  the Ganga system in the central region,
  and the Brahmaputra system in the east.
• The disintegration of this ancient river is attributed to Pleistocene tectonic movements, especially the uplift of the Potwar Plateau (Delhi Ridge), which acted as a water divide between the Indus and Ganga systems.
• The down-thrusting of the Malda Gap between the Rajmahal Hills and Meghalaya Plateau during the mid-Pleistocene period diverted the Ganga and Brahmaputra systems toward the Bay of Bengal.
• Continuous tectonic uplift of the Himalayas and erosion by rivers contributed to the development of antecedent rivers, which maintained their original courses despite mountain uplift.
• This geological evolution explains the present complex drainage pattern of the Himalayan river systems, their deep gorges and large alluvial plains.

5. The river systems of the Himalayan drainage

• The Himalayan drainage is divided into three major river systems: The Indus System, The Ganga System, and The Brahmaputra System, each forming extensive drainage basins.
• These rivers originate from glaciers and snowfields of the Himalayas and Tibetan Plateau, and are fed by both snowmelt and monsoonal rainfall, making them perennial rivers.
• They carve deep gorges in the Himalayan region, especially near high peaks and structural bends, and form wide alluvial plains and deltas in the lowlands.
• The rivers of this system carry large quantities of sediments, resulting in fertile plains but also frequent flooding and channel shifting, particularly in the Ganga and Brahmaputra basins.
• Many of these rivers are classified as antecedent rivers, meaning they maintained their courses even as the Himalayas were uplifted.
• The Himalayan rivers generally have long courses, large catchment areas and numerous tributaries, forming some of the largest river basins in the world.
• These river systems support dense population, agriculture, irrigation and hydroelectric projects across northern and northeastern India.

5.1 The Indus System

• The Indus River (Sindhu) is the westernmost Himalayan river and one of the largest river basins in the world, covering about 11,65,000 sq km, of which 3,21,289 sq km lies in India; its total length is 2,880 km, with 1,114 km in India.
• It originates from a glacier near Bokhar Chu (31°15′N, 81°40′E) in the Kailash Range of Tibet at an altitude of about 4,164 metres, where it is known as Singi Khamban (Lion’s Mouth).
• The river flows northwest between the Ladakh and Zaskar Ranges, forms a deep gorge near Gilgit, passes through Ladakh and Baltistan, and enters Pakistan near Chilas (Dardistan region).
• Major left-bank tributaries in the upper course include Shyok, Gilgit, Zaskar, Hunza, Nubra, Shigar, Gasting and Dras.
• At Attock, it receives the Kabul River on the right bank; other important right-bank tributaries are Khurram, Tochi, Gomal, Viboa and Sangar.
• The five major eastern tributaries of the Indus, forming the Punjab rivers, are Jhelum, Chenab, Ravi, Beas and Sutlej, which join the Indus system mainly in Pakistan.
• The Indus basin is primarily snow-fed and supports irrigation through an extensive canal system, though most of its lower course lies outside India.
• The river finally drains into the Arabian Sea near Karachi, forming a delta region.

5.2 The Ganga System

• The Ganga River originates as the Bhagirathi from the Gangotri Glacier near Gaumukh in the Uttarkashi district of Uttarakhand at an altitude of about 3,900 metres.
• At Devprayag, the Bhagirathi joins the Alaknanda, after which the river is officially known as the Ganga.
• The Alaknanda River originates from the Satopanth Glacier, and its important tributaries include Dhauliganga (Vishnuprayag), Nandakini (Nandprayag), Pindar (Karnaprayag) and Mandakini (Rudraprayag).
• The Ganga enters the plains at Haridwar, flows through Uttarakhand, Uttar Pradesh, Bihar and West Bengal, and has a total length of about 2,525 km.
• Important right-bank tributaries include Yamuna, Son and Punpun, while major left-bank tributaries are Ramganga, Gomti, Ghaghara, Gandak and Kosi.
• The Yamuna, the largest tributary of the Ganga, originates from the Yamunotri Glacier, and meets the Ganga at Prayagraj (Allahabad), forming the famous Triveni Sangam.
• The Ganga forms a vast alluvial plain and, along with the Brahmaputra, creates the Sunderbans Delta, one of the largest deltas in the world, before draining into the Bay of Bengal.
• The Ganga Basin is the most densely populated river basin in India and supports agriculture through its fertile alluvial soil deposits.

5.3 The Brahmaputra System

• The Brahmaputra River originates from the Chemayungdung Glacier near Mansarovar Lake in the Kailash Range (Tibet); in Tibet, it is known as the Tsangpo (meaning “The Purifier”).
• It flows eastward for nearly 1,200 km across southern Tibet in a dry plateau region; its major right-bank tributary in Tibet is the Rango Tsangpo.
• Near Namcha Barwa Peak (7,755 m), it carves a deep gorge in the Eastern Himalayas and enters India west of Sadiya (Arunachal Pradesh) as the Siang or Dihang.
• In Arunachal Pradesh and Assam, it receives important left-bank tributaries Dibang (Sikang) and Lohit, after which it is called the Brahmaputra.
• During its 750 km journey across the Assam Valley, major left-bank tributaries include Burhi Dihing and Dhansari (South), while important right-bank tributaries are Subansiri, Kameng, Manas and Sankosh.
• The Subansiri, originating in Tibet, is an example of an antecedent river, maintaining its course despite Himalayan uplift.
• The Brahmaputra enters Bangladesh near Dhubri, where the Tista joins it on the right bank; in Bangladesh it is known as the Jamuna, and later merges with the Padma (Ganga) before draining into the Bay of Bengal.
• The river is notorious for floods, bank erosion and channel shifting due to heavy rainfall in its catchment area and large sediment load brought by numerous tributaries.

6. The peninsular drainage system

• The Peninsular Drainage System is older than the Himalayan drainage and shows features of river maturity such as broad, shallow and graded valleys.
• The Western Ghats (Sahyadris) act as the main water divide, separating rivers flowing eastward into the Bay of Bengal from those flowing westward into the Arabian Sea.
• Most major Peninsular rivers such as Mahanadi, Godavari, Krishna and Kaveri flow from west to east, following the general slope of the Peninsular Plateau.
• Two important exceptions are the Narmada and Tapi, which flow westward through rift valleys and drain into the Arabian Sea.
• Rivers like Chambal, Sind, Betwa, Ken and Son, though originating in the northern part of the Peninsular Plateau, are tributaries of the Ganga River System.
• Peninsular rivers are generally non-perennial (seasonal), dependent mainly on monsoonal rainfall, and show a fixed course with absence of meanders compared to Himalayan rivers.
• Delta formation is prominent along the east coast where rivers like Godavari, Krishna and Kaveri deposit sediments before entering the Bay of Bengal.

7. The Evolution of Peninsular Drainage System

• The present drainage pattern of Peninsular India is the result of three major geological events that occurred in the distant past.
• First, the subsidence (sinking) of the western flank of the Peninsular block during the Early Tertiary period led to its partial submergence below sea level, disturbing the original symmetrical river pattern.
• Second, the upheaval of the Himalayas caused subsidence of the northern flank of the Peninsular block and resulted in trough faulting, through which rivers like Narmada and Tapi began flowing in rift valleys.
• The Narmada and Tapi Rivers filled these trough faults with detritus materials, and due to this tectonic structure, they lack significant alluvial and deltaic deposits near their mouths.
• Third, a slight tilting of the Peninsular block from northwest to southeast reoriented most river systems towards the Bay of Bengal.
• This tilting explains why major Peninsular rivers such as Mahanadi, Godavari, Krishna and Kaveri flow eastward, while only a few like Narmada and Tapi flow westward into the Arabian Sea.
• These geological events shaped the present drainage pattern, valley forms and flow directions of the Peninsular rivers.

8. River Systems of the Peninsular Drainage

• The Mahanadi River originates near Sihawa in Raipur district (Chhattisgarh), flows through Chhattisgarh and Odisha, and drains into the Bay of Bengal; it is about 851 km long with a catchment area of 1.42 lakh sq km, of which 53% lies in Madhya Pradesh–Chhattisgarh and 47% in Odisha.
• The Godavari River, known as the Dakshin Ganga, rises in the Nasik district of Maharashtra, is the largest Peninsular river system, flows through Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha and Andhra Pradesh, and drains into the Bay of Bengal; it is about 1,465 km long with a catchment area of 3.13 lakh sq km.
• The Krishna River originates near Mahabaleshwar in Maharashtra, flows through Maharashtra, Karnataka, Telangana and Andhra Pradesh, and empties into the Bay of Bengal; important tributaries include Bhima and Tungabhadra.
• The Kaveri River rises in the Brahmagiri Hills (Western Ghats) in Karnataka, flows through Karnataka and Tamil Nadu, and forms a delta before entering the Bay of Bengal; major tributaries include Hemavati, Kabini and Bhavani.
• The Narmada River originates from the Amarkantak Plateau (Madhya Pradesh), flows westward through a rift valley between the Vindhya and Satpura ranges, and drains into the Arabian Sea near Bharuch (Gujarat).
• The Tapi River originates from Multai in Betul district (Madhya Pradesh), flows westward through Madhya Pradesh, Maharashtra and Gujarat, and drains into the Arabian Sea; it is about 724 km long and drains an area of 65,145 sq km.
• The Luni River, the largest river system of western Rajasthan, originates near Pushkar (Aravali region), flows southwest and finally drains into the Rann of Kachchh; it is an ephemeral river.
• Rivers such as Chambal, Sind, Betwa, Ken and Son originate in the northern Peninsular region but join the Ganga River System, showing integration between Peninsular and Himalayan drainage.

9. Smaller Rivers Flowing Towards the West

• The rivers flowing towards the Arabian Sea along the western coast generally have short courses because the Western Ghats lie very close to the coastline, creating a steep gradient.
• In Gujarat, important west-flowing rivers include Sabarmati, Mahi, Shetrunji (Shetruniji), Bhadra and Dhadhar.
• The Shetrunji River rises near Dalkahwa in Amreli district (Gujarat) and flows into the Arabian Sea.
• The Bhadra River originates near Aniali village in Rajkot district (Gujarat) and drains westward.
• The Dhadhar River rises near Ghantar village in Panchmahal district (Gujarat) and flows towards the Arabian Sea.
• The Sabarmati River originates in the Aravali Hills (Rajasthan) and flows through Rajasthan and Gujarat, draining into the Arabian Sea near the Gulf of Khambhat.
• The Mahi River originates from the Vindhyan Range (Madhya Pradesh), flows through Madhya Pradesh, Rajasthan and Gujarat, and drains into the Arabian Sea; it crosses the Tropic of Cancer twice.
• These west-flowing rivers are mostly seasonal, carry limited sediment and generally do not form large deltas due to their short course and steep slope.

10. Extent of usability of river water

• India receives abundant water through monsoonal rainfall, but its availability is unevenly distributed across space and time, leading to regional imbalances in water resources.
• Although the total water availability in Indian rivers is large, only a limited portion is utilisable due to constraints such as topography, uneven distribution, seasonal flow and technical limitations.
• River water is mainly used for irrigation, drinking water supply, hydroelectric power generation, industrial use and inland navigation.
• The Ganga–Brahmaputra Basin has the highest water availability due to heavy rainfall and large catchment area, while western and peninsular regions often face water scarcity.
• Seasonal rivers of the Peninsular Plateau depend heavily on monsoon rainfall, causing fluctuations in water discharge and limiting year-round usability.
• Floods during monsoon and droughts during dry seasons reflect the challenge of managing river water efficiently.
• Construction of dams, reservoirs and multipurpose river valley projects has increased the usable water potential, but inter-state disputes over river water sharing remain a significant issue.
• Effective river basin planning and watershed management are essential for sustainable utilisation of India’s river water resources.

11. Exam Oriented Facts

• Drainage = flow of water through well-defined channels; Drainage Basin = area drained by a river and its tributaries; Watershed = boundary separating two drainage basins.
• 77% drainage area flows into Bay of Bengal (e.g., Ganga, Brahmaputra, Mahanadi, Krishna); 23% flows into Arabian Sea (e.g., Indus, Narmada, Tapi, Mahi, Periyar).
• Major drainage patterns: Dendritic (Northern Plains), Radial (Amarkantak Plateau), Trellis, Centripetal.

Himalayan Drainage – Key Facts

• Ancient river: Shiwalik/Indo–Brahma River (Miocene, 5–24 million years ago); later divided into Indus, Ganga, Brahmaputra systems due to Pleistocene uplift, Potwar Plateau (Delhi Ridge) and Malda Gap subsidence.

Indus System

• Origin: Glacier near Bokhar Chu (31°15′N, 81°40′E) in Kailash Range (Tibet) at 4,164 m; called Singi Khamban in Tibet.
• Length: 2,880 km (India: 1,114 km); Basin area: 11,65,000 sq km (India: 3,21,289 sq km).
• Major tributaries: Shyok, Gilgit, Zaskar, Hunza, Nubra, Shigar, Gasting, Dras; Right bank: Kabul (at Attock), Khurram, Tochi, Gomal.
• Punjab rivers: Jhelum, Chenab, Ravi, Beas, Sutlej.
• Drains into Arabian Sea near Karachi.

Ganga System

• Origin: Bhagirathi from Gangotri Glacier (Gaumukh, Uttarakhand, ~3,900 m).
• Becomes Ganga at Devprayag (confluence of Bhagirathi + Alaknanda).
• Length: 2,525 km.
• Major tributaries:
  Left bank → Ramganga, Gomti, Ghaghara, Gandak, Kosi.
  Right bank → Yamuna (origin: Yamunotri Glacier), Son, Punpun.
• Important confluence: Triveni Sangam (Ganga + Yamuna + mythical Saraswati) at Prayagraj.
• Forms Sunderbans Delta with Brahmaputra before entering Bay of Bengal.
• Kosi = “Sorrow of Bihar” due to frequent course shifting.

Brahmaputra System

• Origin: Chemayungdung Glacier near Mansarovar Lake (Kailash Range); called Tsangpo in Tibet.
• Flows ~1,200 km in Tibet, enters India near Sadiya (Arunachal Pradesh) as Siang/Dihang.
• Major tributaries:
  Left bank → Dibang, Lohit, Burhi Dihing, Dhansari.
  Right bank → Subansiri (antecedent), Kameng, Manas, Sankosh.
• Enters Bangladesh near Dhubri, called Jamuna; merges with Padma (Ganga) before draining into Bay of Bengal.
• Known for floods, erosion and heavy sediment load.

Peninsular Drainage – Key Facts

• Old drainage; rivers show fixed course, absence of meanders, mainly rain-fed.
• General slope: Northwest to Southeast, causing eastward flow.

Major Peninsular Rivers

• Mahanadi: Origin → Sihawa (Chhattisgarh); Length → 851 km; Basin → 1.42 lakh sq km; drains into Bay of Bengal.
• Godavari (Dakshin Ganga): Origin → Nasik (Maharashtra); Length → 1,465 km; Basin → 3.13 lakh sq km; drains into Bay of Bengal.
• Krishna: Origin → Mahabaleshwar (Maharashtra); tributaries → Bhima, Tungabhadra; drains into Bay of Bengal.
• Kaveri: Origin → Brahmagiri Hills (Karnataka); tributaries → Hemavati, Kabini, Bhavani; drains into Bay of Bengal.
• Narmada: Origin → Amarkantak Plateau; flows through rift valley between Vindhya and Satpura; drains into Arabian Sea near Bharuch.
• Tapi: Origin → Multai (Madhya Pradesh); Length → 724 km; Basin → 65,145 sq km; drains into Arabian Sea.
• Luni: Origin → Pushkar (Aravali region); drains into Rann of Kachchh; ephemeral river.

Smaller West-Flowing Rivers (Gujarat Region)

• Sabarmati: Origin → Aravali Hills; drains into Gulf of Khambhat.
• Mahi: Origin → Vindhyan Range (MP); crosses Tropic of Cancer twice; drains into Arabian Sea.
• Shetrunji: Origin → Amreli district.
• Bhadra: Origin → Rajkot district.
• Dhadhar: Origin → Panchmahal district.

Usability of River Water

• High availability in Ganga–Brahmaputra Basin; seasonal variability in Peninsular rivers.
• Major uses: Irrigation, drinking water, hydroelectricity, navigation, industry.
• Challenges: Floods, droughts, inter-state disputes, uneven distribution.

NCERT Class 11 Indian Geography Chapter 3 provides a detailed understanding of India’s river systems and drainage patterns. Mastering NCERT Class 11 Indian Geography Chapter 3 helps students confidently answer questions related to Indus, Ganga, Brahmaputra and Peninsular rivers in CBSE and competitive exams.

A strong grasp of NCERT Class 11 Indian Geography Chapter 3 also makes it easier to understand the monsoon and rainfall patterns discussed in the next chapter.

Continue reading NCERT Class 11 Indian Geography Chapter 4 – Climate to understand India’s monsoon system and seasonal variations.

Frequently Asked Questions (FAQs)

Q1. What is NCERT Class 11 Indian Geography Chapter 3 about?
NCERT Class 11 Indian Geography Chapter 3 explains India’s drainage system, including Himalayan and Peninsular rivers.

Q2. Why is NCERT Class 11 Indian Geography Chapter 3 important for exams?
NCERT Class 11 Indian Geography Chapter 3 is important because questions on river origins, tributaries and drainage patterns are frequently asked in CBSE and competitive exams.

Q3. Which major river systems are covered in NCERT Class 11 Indian Geography Chapter 3?
NCERT Class 11 Indian Geography Chapter 3 covers the Indus, Ganga and Brahmaputra systems along with Peninsular rivers.

Q4. How does NCERT Class 11 Indian Geography Chapter 3 help in UPSC preparation?
NCERT Class 11 Indian Geography Chapter 3 builds conceptual clarity about river systems, which is essential for geography, environment and disaster-related topics in UPSC and BPSC exams.

Q5. Which chapter comes after NCERT Class 11 Indian Geography Chapter 3?
Students should continue with NCERT Class 11 Indian Geography Chapter 4 – Climate to understand monsoon and weather patterns.

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