Chapter summary
The flow of water on land is called drainage. The area drained by a single river system is called a drainage basin (or catchment). India has one of the richest drainage networks in the world — over a hundred named rivers, hundreds of tributaries, thousands of streams.
The chapter divides India's rivers into two principal systems: Himalayan and Peninsular. The Himalayan rivers — Indus, Ganga, Brahmaputra and their tributaries — are perennial (year-round flow), fed by both monsoon rainfall and Himalayan snow/glacier melt. The Peninsular rivers — Godavari, Krishna, Kaveri, Narmada, Tapi, Mahanadi — are rain-fed, with significantly higher monsoon flow than dry-season flow.
The two systems also differ in direction: most Peninsular rivers flow east into the Bay of Bengal (because of the eastward slope of the Deccan Plateau), while the Narmada and Tapi flow west into the Arabian Sea through rift valleys. Himalayan rivers form well-developed deltas (the Sundarban Delta is the world's largest); most Peninsular rivers also form deltas, though Narmada and Tapi form estuaries.
The chapter ends with India's lake systems and the urgent topic of river conservation — particularly the Namami Gange Programme launched in 2014 to clean and rejuvenate the Ganga.
Key concepts in this chapter
- DrainageFlow of water on land in streams, rivers
- Drainage basinArea drained by a single river system
- WatershedBoundary line separating one drainage basin from another
- TributaryA river or stream that joins a larger river
- DistributaryA river that branches off from the main stream (in deltas)
- PerennialRiver that flows all year round; Himalayan rivers
- SeasonalRiver that flows mainly during monsoon; most Peninsular rivers
- DeltaTriangular landmass at river mouth formed by sediment deposit
- EstuaryWide funnel-shaped mouth where river meets sea; no delta forms
- DoabLand between two rivers (Indo-Aryan word: "do" = two, "ab" = water)
Two drainage systems — Himalayan vs Peninsular
| Feature | Himalayan Rivers | Peninsular Rivers |
|---|---|---|
| Origin | Himalayas (mostly glaciers) | Western Ghats or Central Highlands |
| Source water | Glaciers + monsoon rain | Monsoon rain only |
| Flow regime | Perennial (year-round) | Mostly seasonal |
| Geological age | Younger (post-Himalayan upheaval) | Older (existed before Himalayas formed) |
| Length | Long (Ganga 2,525 km; Brahmaputra 2,900 km) | Shorter (Godavari 1,465 km; Kaveri 800 km) |
| Basin size | Very large basins | Smaller basins |
| Catchment | Vast Northern Plains | Concentrated in Deccan |
| Course | Meandering in plains; changes course frequently | Fixed channels; do not change course |
| Sediment load | Very high | Lower |
| Direction | Various — Indus flows NW; Ganga E; Brahmaputra SW after entry to Assam | Mostly east (towards Bay of Bengal); Narmada, Tapi flow west |
| Mouth feature | Form deltas (largest: Sundarban) | Mostly deltas; Narmada/Tapi form estuaries |
Indus River System
The Indus
Rises near Lake Manasarovar in Tibet at an altitude of about 5,182 m. Enters India through Ladakh. Cuts a deep gorge in the Karakoram-Zanskar range. Length: 2,900 km (total); about 1,114 km in India.
The Indus system is the lifeline of Punjab (Punjab = "land of five rivers"). After the 1960 Indus Waters Treaty between India and Pakistan (mediated by World Bank), India received exclusive rights to the three "eastern rivers" (Ravi, Beas, Sutlej) and limited rights on the three "western rivers" (Indus, Jhelum, Chenab).
Major tributaries:
- Jhelum — rises near Verinag (J&K); flows through Wular Lake; meets Chenab in Pakistan.
- Chenab — formed by Chandra + Bhaga at Tandi (Himachal); largest tributary by water.
- Ravi — rises in Kullu hills; flows through Chamba; meets Chenab in Pakistan.
- Beas — rises near Rohtang Pass; meets Sutlej in Punjab (India).
- Sutlej — rises in Rakshastal (Tibet); originally tributary of Ghaggar before river capture; Bhakra Dam on this river.
Ganga River System
The Ganga
The headwaters Bhagirathi rise from the Gangotri Glacier in Uttarakhand. At Devprayag, it meets the Alaknanda (other headstream) and is called Ganga. Length: 2,525 km. Total basin: 8.6 lakh sq km — about 26% of India's land area; supports the densest population on Earth.
The Ganga is India's holiest river and the country's lifeline. It flows through Uttarakhand, UP, Bihar, Jharkhand, West Bengal before entering Bangladesh.
Major tributaries:
- Left-bank (from Himalayas): Yamuna (its biggest tributary; rises from Yamunotri Glacier; flows parallel to Ganga; joins at Allahabad-Prayagraj), Ghaghara, Gandak, Kosi — all monsoon-fed Himalayan rivers; cause major floods.
- Right-bank (from Peninsular Plateau): Chambal (rises in MP, flows through ravines), Betwa, Ken, Son — these are not snow-fed and have lower flow than the Himalayan tributaries.
The Ganga forms the world's largest delta — the Sundarban Delta — covering 80,000 sq km (largest in India + Bangladesh). The delta is home to mangrove forests and the Royal Bengal Tiger. It's a UNESCO World Heritage Site.
Brahmaputra River System
The Brahmaputra
Rises in the Mansarovar region (Tibet) under the name Tsangpo. Flows east through Tibet for about 1,800 km, then takes a sharp U-turn around Namcha Barwa peak ("Great Bend") and enters India in Arunachal Pradesh as Siang/Dihang. Joins the Lohit and Dibang in Assam to become Brahmaputra. Length: 2,900 km total; 720 km in India. The river is known as Jamuna in Bangladesh and joins the Ganga to form the Padma.
The Brahmaputra is famous for its enormous silt load and frequent devastating floods. It changes its course frequently in the Assam plain, leading to disastrous bank erosion. The river creates the world's largest river island — Majuli (Assam).
Major tributaries: Subansiri, Manas, Tista (also flows into Brahmaputra after passing through Bangladesh), Lohit, Dibang, Burhi Dihing.
Peninsular Rivers
Six major rivers, most flowing east; two (Narmada, Tapi) flow west through rift valleys.
Godavari — "Dakshin Ganga" (Ganga of the South)
The largest Peninsular river. Rises near Nashik (Maharashtra). Flows east through Maharashtra, Telangana, Andhra Pradesh — drains into Bay of Bengal. Length: 1,465 km. Tributaries: Penganga, Indravati, Manjira, Wardha, Pranhita. Forms a large delta near Rajahmundry.
Krishna
Rises near Mahabaleshwar (Maharashtra, Western Ghats). Flows east through Maharashtra, Karnataka, Telangana, Andhra Pradesh. Length: 1,400 km. Tributaries: Koyna, Bhima, Tungabhadra, Musi. Forms delta near Vijayawada.
Kaveri (Cauvery)
Rises in Brahmagiri hills (Karnataka, Western Ghats). Flows through Karnataka and Tamil Nadu — drains into Bay of Bengal. Length: 800 km. Tributaries: Kabini, Bhavani, Amravati. Source of perennial inter-state water dispute between Karnataka and Tamil Nadu.
Narmada — flows WEST
Rises from Amarkantak Plateau (MP). Flows west through Madhya Pradesh and Gujarat through a rift valley between Vindhya and Satpura. Length: 1,312 km. Famous Marble Rocks gorge at Bhedaghat (Jabalpur). Forms an estuary in the Gulf of Khambhat. Sardar Sarovar Dam controversy.
Tapi (Tapti) — flows WEST
Rises in Satpura range (MP). Flows west parallel to Narmada through a rift valley. Length: 724 km. Drains into Gulf of Khambhat near Surat (Gujarat). Like Narmada, forms an estuary, not a delta.
Mahanadi
Rises in Chhattisgarh. Flows through Chhattisgarh and Odisha into the Bay of Bengal. Length: 858 km. Forms a delta near Cuttack/Paradeep. Hirakud Dam — one of the world's longest earthen dams — is on this river.
Lakes of India
India has a great variety of lakes, classified by origin:
Glacial lakes (Himalayan origin)
- Wular Lake (J&K) — India's largest freshwater lake; formed by glacial action.
- Dal Lake (J&K) — Srinagar; famous for shikaras and floating gardens.
- Pangong Tso (Ladakh) — saltwater lake at 4,350 m altitude; divided between India and China.
- Tsomoriri (Ladakh) — Ramsar wetland.
Lagoons / Backwater lakes
- Chilika Lake (Odisha) — Asia's largest brackish water lagoon; Ramsar wetland; migratory bird habitat.
- Pulicat (Andhra-Tamil Nadu) — second largest brackish lagoon in India.
- Vembanad (Kerala) — largest lake in Kerala; central to Kerala's backwater system.
- Ashtamudi (Kerala) — eight-armed lake; Ramsar site.
Tectonic lakes
- Loktak (Manipur) — famous for floating phumdis (mats of vegetation); Keibul Lamjao National Park is the world's only floating park, home to the endangered Sangai deer.
Salt lakes
- Sambhar (Rajasthan) — India's largest saltwater lake; major source of salt.
- Pushkar (Rajasthan) — sacred lake; site of the annual Pushkar Fair.
Crater lakes
- Lonar Lake (Maharashtra) — formed by a meteorite impact 50,000 years ago; both saline and alkaline.
Artificial lakes (reservoirs)
- Govind Sagar (Bhakra Dam, Himachal)
- Indira Sagar (Narmada, MP)
- Hirakud (Mahanadi, Odisha)
- Nagarjuna Sagar (Krishna, Telangana)
Rivers and conservation
India's rivers face severe pollution. The Central Pollution Control Board (CPCB) has identified hundreds of polluted stretches across major rivers. Key issues:
- Domestic sewage — over 70% of India's urban sewage goes untreated into rivers.
- Industrial effluents — leather (Kanpur), textiles (Tirupur), paper, chemicals — discharge toxic waste.
- Agricultural runoff — pesticides and fertilisers leach into rivers.
- Idol immersion — Plaster of Paris idols release heavy metals.
- Damming — reduces natural flushing; alters ecosystem.
Ganga conservation efforts have included Ganga Action Plan I (1986) and II, which had limited success. The Namami Gange Programme launched in May 2014 is the latest integrated mission — with Rs 20,000 crore initial budget (extended) and components covering sewage treatment, riverfront development, biodiversity conservation, afforestation, and public awareness. Progress has been uneven — some stretches show improvement, others worsen.
Other major river protection efforts: Yamuna Action Plan, National River Conservation Plan (NRCP), Brahmaputra Board, Tapi Action Plan.
NCERT exercise Q&A (with explanations)
(b) Dendritic. A dendritic drainage pattern (from Greek dendron = tree) develops when a river system follows the slope of the terrain in a tree-like pattern. The main river is the "trunk" and the tributaries are the "branches." Tributaries join the main river at acute angles. This is the most common drainage pattern, formed where the underlying rock is uniform.
(a) Radial — rivers radiate outward from a central high point (e.g., from a volcano). (c) Centripetal — rivers flow inward toward a central low point. (d) Trellis — rivers join their parent at near right-angles, like a trellis pattern; develops where alternating hard and soft rocks lie roughly parallel.
(d) Jammu and Kashmir. Wular Lake is located in the Bandipora district of Jammu and Kashmir. It is India's largest freshwater lake and has been formed by tectonic activity. The Jhelum River flows through it. It is a Ramsar wetland of international importance.
(b) Amarkantak. The Narmada rises from the Amarkantak Plateau in eastern Madhya Pradesh. It flows westward through a rift valley between the Vindhya and Satpura ranges, then through Madhya Pradesh and Gujarat before draining into the Arabian Sea at the Gulf of Khambhat. The Tapi rises in the Satpura range (option a) but the question asks about the Narmada.
(a) Sambhar Lake in Rajasthan is India's largest salt water (saline) lake. It is an inland saline lake — formed by streams that bring in mineral salts from the Aravali Range; the salts concentrate as water evaporates in the arid climate. Sambhar is a major source of salt in India.
(b) Wular and (c) Dal are freshwater lakes in J&K. (d) Gobind Sagar is an artificial reservoir created by the Bhakra Dam — freshwater.
(c) Godavari. The Godavari, at 1,465 km, is the longest river of Peninsular India. It is also called "Dakshin Ganga" (the Ganges of the South). It rises near Trimbak (close to Nashik) in Maharashtra and flows east through Maharashtra, Telangana, and Andhra Pradesh into the Bay of Bengal. Comparative lengths: Krishna 1,400 km; Narmada 1,312 km; Mahanadi 858 km.
The Himalayan and Peninsular rivers differ in five major ways:
(1) Origin and source water: Himalayan rivers originate in the Himalayas, mostly in glaciers. They are fed by BOTH rainfall AND snow/glacier melt — so they have water year-round. Peninsular rivers originate in the Western Ghats or Central Highlands. They are fed by rainfall only — so they have heavy flow in monsoon and low flow in summer.
(2) Flow regime: Himalayan rivers are perennial (year-round flow). Peninsular rivers are mostly seasonal — many become trickles in summer.
(3) Age: Himalayan rivers are geologically younger (formed after the Himalayan upheaval ~50 million years ago). Peninsular rivers are much older (existed before the Himalayas; their courses have been long-established).
(4) Channel character: Himalayan rivers meander widely in the plains, frequently changing course (Kosi is called "Bihar's Sorrow" for this reason). Peninsular rivers flow through fixed, well-defined channels — they do not change course because the underlying rock is hard.
(5) Erosion and deposit: Himalayan rivers carry enormous sediment loads and form large fertile deltas (Sundarban — world's largest). Peninsular rivers carry less sediment; Narmada and Tapi form estuaries (not deltas) because they flow through rift valleys where the river meets the sea quickly.
UPSC / MPSC previous year questions on this chapter
UPSC Mains GS-1 2023
"Discuss the salient features of the Drainage System of India. How does it influence the economy?" — Direct test. Frame answer around Himalayan vs Peninsular systems + agricultural, hydroelectric, transportation, drinking water, fishery economic contributions.
UPSC Prelims 2020
"Consider the following pairs: 1. Aspatial River — Bay of Bengal. 2. Brahmani River — Bay of Bengal. 3. Pranahita — Tributary of Godavari. Which of the above is/are correct?" — Tests detailed river knowledge.
UPSC Prelims 2017
"With reference to the river Luni, which one of the following statements is correct? (a) It flows into Gulf of Khambhat. (b) It flows into Gulf of Kachchh. (c) It flows into Pakistan and merges with a tributary of Indus. (d) It is lost in marshy land of Rann of Kachchh." — Answer: (d). The Luni rises in Aravali and disappears in the Rann of Kutch — does not reach the sea.
MPSC Rajyaseva 2020
"Which is the longest river of South India?" — Answer: Godavari (1,465 km).