Geography
Drainage System of India
Himalayan Rivers: Indus, Ganga and Brahmaputra Systems
Himalayan drainage for CGPSC: drainage patterns, antecedent rivers, the Indus, Ganga and Brahmaputra systems, their tributaries, sources and confluences.
Prerequisites
- India: Location and Physiography: the Himalaya, the Northern Plains and the Peninsular plateau, the three units that decide where rivers rise and flow
- Drainage: Rivers and Basins of Chhattisgarh: the Rihand and Kanhar from Chhattisgarh reach the Ganga through the Son
The Hook: A River from Surguja That Ends in the Bay via Patna
Connect
The Rihand (रिहंद) rises in the Matiranga hills near Mainpat in Surguja and flows north into Uttar Pradesh. It joins the Son, the Son joins the Ganga near Arrah in Bihar, and the Ganga reaches the Bay of Bengal through the world’s largest delta. So a stream from northern Chhattisgarh is part of the Ganga system, a Himalayan river system.
How do the three great Himalayan systems (Indus, Ganga, Brahmaputra) work, and which tributary goes where?
Why it matters: Prelims loves source–confluence–tributary questions (“Chandra and Bhaga form which river?”, “which river forms the Panch Prayag?”), left-bank vs right-bank lists and “antecedent river” statements. Mains GS-III asks about floods, the Ganga’s pollution and water treaties with neighbours.
Drainage Basics (अपवाह तंत्र)
| Term | Meaning |
|---|---|
| Drainage (अपवाह) | The flow of water through well-defined channels |
| Drainage basin / catchment (जलग्रहण क्षेत्र) | The area drained by a river and its tributaries |
| Water divide (जल विभाजक) | High ground separating two basins, e.g. the Western Ghats between east- and west-flowing Peninsular rivers |
| Confluence (संगम) | Point where two rivers meet, e.g. Devprayag |
| Distributary | A channel that leaves the main river, usually in a delta (the Hugli from the Ganga) |
Drainage patterns
| Pattern | Shape | Indian example |
|---|---|---|
| Dendritic (वृक्षाकार) | Like the branches of a tree | Rivers of the Northern Plains |
| Trellis (जालीनुमा) | Main streams parallel, tributaries join at right angles; in folded rocks | Parts of the Himalaya and older fold belts |
| Radial (अरीय) | Streams flow outward from a central high point | Rivers rising in the Amarkantak area (Narmada, Son) |
| Centripetal (अभिकेंद्री) | Streams flow inward into a depression or lake | Streams draining into Loktak lake, Manipur |
| Rectangular | Streams bend at right angles along joints in hard rock | Peninsular plateau areas |
Himalayan vs Peninsular rivers
| Feature | Himalayan rivers | Peninsular rivers |
|---|---|---|
| Source | Himalayan glaciers and snowfields | Peninsular plateau, Western Ghats, central highlands |
| Flow | Perennial (snowmelt + rain) | Mostly seasonal (rain-fed) |
| Valleys | Deep gorges in the mountains; meanders, shifting courses in the plains | Shallow, well-adjusted valleys; courses largely fixed |
| Type | Antecedent in parts, dendritic in the plains | Superimposed, rejuvenated; trellis, radial, rectangular |
| Age | Young, still deepening their valleys (active erosion) | Old, with graded profiles close to base level |
| Basin | Very large | Relatively small |
| Mouth | Large deltas (Ganga–Brahmaputra) | Deltas on the east coast; estuaries for the Narmada and Tapi |
Antecedent rivers
An antecedent river (पूर्ववर्ती नदी) is older than the mountain it crosses. As the Himalaya rose, the Indus, Sutlej and Brahmaputra kept cutting down and kept their courses, carving deep gorges. They rise north of the Great Himalaya, in Tibet, and cut across the ranges.
1. The Indus System (सिंधु)
| Fact | Detail |
|---|---|
| Source | Tibet, near the Bokhar Chu glacier on the Kailash range (north of the Himalaya) |
| Length | About 2,880 km, of which about 1,114 km is in India (NCERT figures) |
| Route in India | Enters Ladakh, flows north-west between the Ladakh and Zaskar ranges past Leh, then into Pakistan (Gilgit–Baltistan) |
| Outlet | Arabian Sea, near Karachi |
| Upper tributaries | Zaskar, Shyok, Nubra (joins the Shyok), Gilgit, Hunza |
| Panjnad (पंजनद) | The five Punjab rivers (Jhelum, Chenab, Ravi, Beas, Sutlej) unite and join the Indus a little above Mithankot in Pakistan |
The five rivers of Punjab
| River | Source | Key points |
|---|---|---|
| Jhelum (झेलम) | Spring at Verinag, south-east Kashmir valley | Flows through Srinagar and the Wular lake; deep gorge; joins the Chenab in Pakistan |
| Chenab (चिनाब) | Formed by the Chandra and Bhaga, which meet at Tandi (Lahaul, Himachal Pradesh) | Largest tributary of the Indus; also called Chandrabhaga |
| Ravi (रावी) | Kullu hills, west of the Rohtang pass | Drains the Chamba valley |
| Beas (ब्यास) | Beas Kund, near the Rohtang pass | Flows through Kullu–Manali; joins the Sutlej at Harike (Punjab); the only one of the five that flows entirely in India |
| Sutlej (सतलुज) | Rakas Tal near Mansarovar, Tibet (known there as Langchen Khambab) | Antecedent; enters India at Shipki La; feeds the Bhakra–Nangal project |
Indus Waters Treaty (1960): status as of 2026
Signed in 1960 with World Bank mediation. The eastern rivers (Ravi, Beas, Sutlej) went to India; the western rivers (Indus, Jhelum, Chenab) went mainly to Pakistan, with limited Indian uses such as run-of-river hydropower.
After the Pahalgam terror attack, India placed the treaty “in abeyance” in April 2025 and has said it stays so until Pakistan credibly ends support for cross-border terrorism. Pakistan says the treaty is still in force. In May 2026 a Court of Arbitration at The Hague issued a ruling on Indian projects on the western rivers; India rejected it, saying the tribunal was illegally constituted. Treat this as a live issue and check the latest position before writing about it.
2. The Ganga System (गंगा)
| Fact | Detail |
|---|---|
| Headstreams | Bhagirathi from the Gangotri glacier (snout at Gaumukh, Uttarkashi) and Alaknanda from the Satopanth glacier above Badrinath |
| Name “Ganga” | From Devprayag, where the Bhagirathi joins the Alaknanda |
| Enters the plains | At Haridwar |
| Length | About 2,525 km, the longest river in India (NCERT) |
| Basin | Largest in India: about 8.6 lakh km² in India alone |
| National River | Declared India’s National River in 2008 |
| Lower course | Farakka barrage (West Bengal) diverts water into the Bhagirathi–Hugli; the main stream enters Bangladesh as the Padma, joins the Brahmaputra (Jamuna) and then the Meghna |
| Delta | Ganga–Brahmaputra (Sundarbans) delta, the largest delta in the world |
Panch Prayag on the Alaknanda (upstream to downstream)
| Prayag | Alaknanda meets |
|---|---|
| Vishnuprayag | Dhauliganga |
| Nandprayag | Nandakini |
| Karnaprayag | Pindar |
| Rudraprayag | Mandakini |
| Devprayag | Bhagirathi (the river becomes the Ganga) |
Tributaries by bank
| Left bank (from the Himalaya) | Right bank (mostly from the Peninsula) |
|---|---|
| Ramganga | Yamuna (from Yamunotri; joins at Prayagraj) |
| Gomti (rises in the plains, Pilibhit) | Son (from Amarkantak; joins near Arrah, west of Patna) |
| Ghaghra (joins near Chhapra) | Damodar (joins the Hugli; “Sorrow of Bengal”) |
| Gandak (from Nepal; joins near Patna, at Sonpur–Hajipur) | Punpun |
| Kosi (“Sorrow of Bihar”) | |
| Mahananda (Darjeeling hills; last left-bank tributary in India) |
The Yamuna and its Peninsular tributaries
- Yamuna (यमुना): the longest tributary of the Ganga. It rises at the Yamunotri glacier on the Bandarpunch range and joins the Ganga at Prayagraj.
- Its right-bank tributaries come from the Peninsular plateau: Chambal (rises near Mhow, Malwa plateau; famous for its badland ravines; Gandhi Sagar, Rana Pratap Sagar and Jawahar Sagar dams, Kota barrage), Sind, Betwa and Ken. The Ken and Betwa are the rivers of the first river-link project (see Inter-linking of Rivers).
- Left-bank: Hindan, among others.
The Son and Chhattisgarh
The Son (सोन) rises in the Amarkantak area, flows north and east, drops in a series of falls off the plateau edge and joins the Ganga near Arrah. Chhattisgarh’s Rihand (dam: Govind Ballabh Pant Sagar, in Sonbhadra, UP) and Kanhar join the Son, which is how about a seventh of Chhattisgarh drains to the Ganga. Details: Drainage of Chhattisgarh.
Two “sorrows”
| River | Why a “sorrow” | Response |
|---|---|---|
| Kosi (कोसी), Sorrow of Bihar | Huge silt load from Nepal; the channel has shifted westward dramatically over the last two centuries; breaches such as 2008 | Kosi barrage and embankments (Indo-Nepal agreement) |
| Damodar (दामोदर), Sorrow of Bengal | Flash floods from the Chotanagpur plateau | Damodar Valley Corporation (DVC), 1948, on the model of the Tennessee Valley Authority |
3. The Brahmaputra System (ब्रह्मपुत्र)
| Fact | Detail |
|---|---|
| Source | Chemayungdung glacier of the Kailash range, near Lake Mansarovar |
| In Tibet | Yarlung Tsangpo, flows east parallel to the Himalaya |
| Entry into India | Takes a U-turn around Namcha Barwa and enters Arunachal Pradesh as the Siang / Dihang |
| Becomes “Brahmaputra” | When the Dibang and Lohit join near Sadiya (Assam) |
| Length | About 2,900 km (NCERT) |
| In Bangladesh | Jamuna; joins the Padma, then flows into the Bay as the Meghna |
| Right-bank tributaries | Subansiri (antecedent), Kameng, Manas, Sankosh; the Teesta joins in Bangladesh |
| Left-bank tributaries | Burhi Dihing, Dhansiri (south), Kopili |
| River island | Majuli (Assam), made a district in 2016; often called the largest river island in the world |
Mains angle: dams upstream in Tibet
On 19 July 2025, China formally began construction of a very large hydropower project on the lower Yarlung Tsangpo in Medog (Mêdog) county, just before the river enters India. India’s concerns are flow regulation in the lean season, flood surges, sediment and the absence of any water-sharing treaty (cooperation has been limited to sharing flood-season hydrological data under MoUs). India’s own counter-plan is a large storage project on the Siang in Arunachal Pradesh, which faces local opposition. Check the latest status before quoting.
Analysis for Mains: Why Himalayan Rivers Matter
- Agriculture and food security: perennial flow and the alluvial plains they built support the Indo-Gangetic grain belt.
- Floods: heavy silt, low gradient in the plains and embankment failures make Bihar, Assam and eastern UP flood-prone (Kosi, Brahmaputra).
- Hydropower potential: steep gradients in the Himalaya; but seismic risk, glacial-lake outburst floods (GLOFs) and fragile slopes demand caution.
- Pollution: urban sewage and industrial effluents in the Ganga and Yamuna. The Namami Gange programme (approved as a flagship programme in 2014) runs through the National Mission for Clean Ganga.
- Inland waterways: National Waterway 1 (Ganga–Bhagirathi–Hugli, Haldia to Prayagraj) and NW 2 (Brahmaputra, Dhubri to Sadiya).
- Geopolitics: shared basins with Pakistan (Indus), Nepal (Kosi, Gandak), China (Brahmaputra) and Bangladesh (Ganga, Teesta).
Memory Tricks
Panch Prayag upstream to downstream: 'Very Nice Kids Read Daily'
Vishnuprayag (Dhauliganga), Nandprayag (Nandakini), Karnaprayag (Pindar), Rudraprayag (Mandakini), Devprayag (Bhagirathi).
Indus Treaty split: 'East = RBS for India'
Ravi, Beas, Sutlej (eastern) for India; Indus, Jhelum, Chenab (western) mainly for Pakistan.
Brahmaputra's three names
T-S-J: Tsangpo in Tibet, Siang/Dihang in Arunachal, Jamuna in Bangladesh. It is called the Brahmaputra only after the Dibang + Lohit join near Sadiya.
Don’t Confuse
| This | vs | That |
|---|---|---|
| Chenab = Chandra + Bhaga (at Tandi) | Ganga = Bhagirathi + Alaknanda (at Devprayag) | |
| Beas joins the Sutlej at Harike (in India) | Panjnad joins the Indus near Mithankot (in Pakistan) | |
| Kosi: Sorrow of Bihar | Damodar: Sorrow of Bengal | |
| Son joins the Ganga directly | Chambal, Betwa, Ken join the Yamuna | |
| Yamuna: longest Ganga tributary | Chenab: largest Indus tributary | |
| Gangotri (Bhagirathi) | Yamunotri (Yamuna) |
Common Mistakes
Trap 1: the Son is a left-bank, Himalayan tributary
The Son is a right-bank tributary that comes from the Peninsula (Amarkantak). It belongs to the Ganga system, but it is not a Himalayan river by origin.
Trap 2: the Ganga gets its name at Haridwar or Rishikesh
The name Ganga begins at Devprayag. Haridwar is where it enters the plains.
Trap 3: the Teesta joins the Brahmaputra in India
The Teesta flows through Sikkim and West Bengal but joins the Brahmaputra (Jamuna) in Bangladesh, which is why its water sharing is an India–Bangladesh issue.
Trap 4: all Himalayan rivers rise south of the Great Himalaya
The Indus, Sutlej and Brahmaputra rise in Tibet, north of the main ranges, and cut across them. That is the evidence for calling them antecedent.
Practice
All questions below are original practice questions written in CGPSC style. They are not previous-year questions.
Level 1: Foundation
- The Chandra and the Bhaga meet at ________ to form the ________.
- The Bhagirathi and Alaknanda meet at ________.
- The Brahmaputra is known as the ________ in Tibet and the ________ in Bangladesh.
Answers
- Tandi (Lahaul, Himachal Pradesh); Chenab
- Devprayag
- Yarlung Tsangpo; Jamuna
Level 2: Prelims MCQs
Q1. Consider the following statements:
- The Indus, the Sutlej and the Brahmaputra are examples of antecedent rivers.
- The Beas joins the Sutlej in Pakistan.
- The Chenab is formed by the confluence of the Chandra and the Bhaga.
Which of the statements given above is/are correct?
- (a) 1 and 2 only
- (b) 1 and 3 only
- (c) 2 and 3 only
- (d) 1, 2 and 3
Answer and explanation
(b) 1 and 3 only. The three rivers rise north of the Great Himalaya and cut gorges across it, so they are antecedent. The Beas joins the Sutlej at Harike in Punjab (India); it is the only Punjab river that flows entirely within India. The Chandra and Bhaga meet at Tandi to form the Chenab.
Q2. Match List-I (Prayag) with List-II (River that joins the Alaknanda):
| List-I | List-II |
|---|---|
| A. Vishnuprayag | 1. Mandakini |
| B. Karnaprayag | 2. Dhauliganga |
| C. Rudraprayag | 3. Bhagirathi |
| D. Devprayag | 4. Pindar |
- (a) A-2, B-4, C-1, D-3
- (b) A-4, B-2, C-1, D-3
- (c) A-2, B-1, C-4, D-3
- (d) A-1, B-4, C-2, D-3
Answer and explanation
(a) A-2, B-4, C-1, D-3. Vishnuprayag: Dhauliganga; Karnaprayag: Pindar; Rudraprayag: Mandakini; Devprayag: Bhagirathi, after which the river is called the Ganga. Nandprayag (Nandakini) is the fifth.
Q3. Which one of the following is a right-bank tributary of the Ganga that rises on the Peninsular plateau?
- (a) Gandak
- (b) Ghaghra
- (c) Son
- (d) Kosi
Answer and explanation
(c) Son. The Son rises in the Amarkantak area and joins the Ganga near Arrah. The Gandak, Ghaghra and Kosi are left-bank tributaries from the Himalaya. Chhattisgarh’s Rihand and Kanhar feed the Son.
Q4. Under the Indus Waters Treaty of 1960, which rivers were allocated to India for unrestricted use?
- (a) Indus, Jhelum, Chenab
- (b) Ravi, Beas, Sutlej
- (c) Jhelum, Ravi, Beas
- (d) Chenab, Sutlej, Ravi
Answer and explanation
(b) Ravi, Beas, Sutlej, the eastern rivers. The western rivers (Indus, Jhelum, Chenab) went mainly to Pakistan, with limited permitted uses for India. India placed the treaty in abeyance in April 2025.
Q5. The Brahmaputra takes this name after which rivers join the Siang (Dihang) near Sadiya?
- (a) Subansiri and Manas
- (b) Teesta and Kameng
- (c) Dibang and Lohit
- (d) Dhansiri and Kopili
Answer and explanation
(c) Dibang and Lohit. The Subansiri, Kameng and Manas join lower down on the right bank; the Dhansiri and Kopili are left-bank tributaries; the Teesta joins in Bangladesh.
Level 3: Mains Answer Writing
Q1. Distinguish between Himalayan and Peninsular rivers. (60 words)
Model answer outline
- Himalayan: glacier-fed, perennial, young and actively eroding, deep gorges (antecedent: Indus, Sutlej, Brahmaputra), meandering and shifting courses in the plains, large basins and deltas.
- Peninsular: rain-fed, seasonal, old with graded profiles, fixed shallow valleys, smaller basins; east-flowing rivers form deltas, the Narmada and Tapi form estuaries.
- Conclusion: The contrast reflects the age and structure of the two landmasses.
Q2. “The Ganga is both a lifeline and a challenge.” Discuss with reference to floods, pollution and river management. (150–200 words)
Model answer outline
- Intro: India’s longest river (about 2,525 km) and largest basin (about 8.6 lakh km² in India); National River since 2008.
- Lifeline: perennial water for the Indo-Gangetic grain belt; fertile alluvium; NW-1 waterway; cultural and pilgrimage economy (Haridwar, Prayagraj, Varanasi).
- Challenges:
- Floods from left-bank tributaries (Kosi, Gandak, Ghaghra) and silt build-up.
- Pollution from untreated sewage and industrial effluents.
- Reduced lean-season flow from heavy diversion and groundwater pumping.
- Barrage-related issues (Farakka: silting, India–Bangladesh sharing).
- Responses: Namami Gange (2014) through the National Mission for Clean Ganga; sewage treatment capacity; DVC model for the Damodar; floodplain zoning.
- Chhattisgarh angle: the state’s Rihand and Kanhar feed the Son, so forest and catchment protection in Surguja matters for the Ganga basin too.
- Conclusion: Basin-wide, integrated management, not isolated projects, is needed.
Quick Revision Table
| Fact | Detail |
|---|---|
| Antecedent rivers | Indus, Sutlej, Brahmaputra |
| Indus | Bokhar Chu (Tibet); about 2,880 km (1,114 km in India); Panjnad joins near Mithankot |
| Jhelum | Verinag spring; through Wular lake |
| Chenab | Chandra + Bhaga at Tandi; largest Indus tributary |
| Beas | Beas Kund; joins Sutlej at Harike; wholly in India |
| Sutlej | Rakas Tal; enters India at Shipki La; Bhakra–Nangal |
| Indus Waters Treaty | 1960; east (Ravi, Beas, Sutlej) to India; in abeyance from India’s side since April 2025 |
| Ganga | Bhagirathi (Gangotri, Gaumukh) + Alaknanda at Devprayag; about 2,525 km; National River 2008 |
| Panch Prayag | Vishnu (Dhauliganga), Nand (Nandakini), Karna (Pindar), Rudra (Mandakini), Dev (Bhagirathi) |
| Yamuna | Yamunotri; joins at Prayagraj; longest Ganga tributary; Chambal, Sind, Betwa, Ken |
| Son | Amarkantak; joins near Arrah; Rihand, Kanhar from Chhattisgarh |
| Sorrows | Kosi (Bihar), Damodar (Bengal; DVC 1948) |
| Brahmaputra | Chemayungdung glacier; Tsangpo, Siang/Dihang, Jamuna; Dibang + Lohit at Sadiya; about 2,900 km |
| Majuli | River island in Assam; district since 2016 |
Key Takeaways
Key Takeaways
- Himalayan rivers are perennial, young and erosive; the Indus, Sutlej and Brahmaputra are antecedent.
- Indus system: Panjnad of five rivers; Treaty of 1960 gives India the eastern rivers; in abeyance from India’s side since 2025.
- Ganga system: Devprayag, Panch Prayag, Yamuna as the longest tributary, Son and Chambal from the Peninsula.
- Brahmaputra: three names, joined by the Dibang and Lohit near Sadiya; upstream dams in Tibet are a strategic concern.
- Northern Chhattisgarh belongs to the Ganga system through the Rihand and Kanhar → Son.
What’s Next
- Peninsular Rivers: the Mahanadi, Godavari, Krishna, Kaveri, Narmada and Tapi
- Lakes of India: Wular on the Jhelum, Loktak’s centripetal drainage and more
- Climate and the Indian Monsoon: the rain that feeds both river systems
- Indian Agriculture: irrigation in the Indo-Gangetic plains
Advertisement