Indian Drainage System and Rivers

Flagship: what this is and why CAPF cares

A drainage system is the network of channels by which a region sheds its water, and the divide that separates one such basin from the next. India's rivers are tested by CAPF as a matching and location quiz: source to river, river to tributary, river to mouth, river to dam, lake to State, waterfall to river. The east-versus-west flow rule and the tributaries of the big three systems return year after year. The security value is just as real. The Indus system is locked into the Indus Waters Treaty with Pakistan and is a standing diplomatic and security lever; the Brahmaputra rises in China, making upstream dams a strategic worry; and the riverine stretches of the Indo-Bangladesh border, the Sundarbans and the char (river-island) tracts, are among the Border Security Force's hardest sectors, patrolled by boat and floating border outposts. The anchor text is NCERT Class XI, India: Physical Environment (the chapter on drainage).

The Indus system

The Indus rises near Lake Mansarovar in Tibet, flows north-west through Ladakh, gorges past Nanga Parbat, and turns south through Pakistan to the Arabian Sea. Its five great left-bank tributaries give Punjab ("land of five waters") its name: the Jhelum (rises at Verinag, flows through the Kashmir Valley and Wular Lake), the Chenab (largest of the five, formed by the Chandra and Bhaga at Tandi), the Ravi, the Beas (entirely within India, joins the Sutlej at Harike), and the Sutlej (rises near Mansarovar as the Langchen, an antecedent river, dammed at Bhakra). Under the Indus Waters Treaty of 1960, brokered by the World Bank, the three eastern rivers (Ravi, Beas, Sutlej) are allocated to India and the three western rivers (Indus, Jhelum, Chenab) largely to Pakistan, with India retaining limited non-consumptive use of the western rivers.

The Ganga system

The Ganga is the longest river within India. It rises as the Bhagirathi from the Gangotri glacier (at Gaumukh); the Alaknanda joins it at Devprayag, and below that confluence the river is called the Ganga. It emerges onto the plains at Haridwar, runs through Uttar Pradesh, Bihar and West Bengal, and splits in the delta: the Bhagirathi-Hooghly distributary turns south past Kolkata while the main flow continues east into Bangladesh as the Padma. Joined there by the Brahmaputra (as the Jamuna) and the Meghna, it forms the world's largest delta, the Sundarbans, on the Bay of Bengal. The Yamuna is its longest and most important tributary, rising at the Yamunotri glacier and joining the Ganga at Prayagraj (Allahabad), the Triveni Sangam.

Ganga course landmarks

From source to sea the Ganga passes a recognisable string of landmarks the exam draws on: Gangotri and Gaumukh (glacier source), Devprayag (named), Haridwar (onto the plains), Kanpur and Prayagraj (Yamuna confluence), Varanasi, Patna (joined by the Son, Gandak and Ghaghara), Farakka (the barrage where the Hooghly distributary splits off), and the Sundarbans mouth. The Ganga is the subject of the Namami Gange and earlier Ganga Action Plan clean-up programmes.

The Brahmaputra system

The Brahmaputra rises in Tibet as the Tsangpo, runs east for a great distance behind the Himalayas, then takes a hairpin bend (the Great Bend) around Namcha Barwa and plunges south into Arunachal Pradesh as the Siang or Dihang. In Assam, joined by the Dibang and Lohit, it becomes the Brahmaputra, a braided river so heavy with silt that it builds and shifts sandbar islands and is notorious for flooding; Majuli, in its course, is the world's largest river island. It is one of the few rivers with a masculine name ("son of Brahma"). It enters Bangladesh as the Jamuna and joins the Ganga.

The Brahmaputra's chief tributaries in India are the Subansiri, Kameng, Manas, Dhansiri and Dibang on the north bank and the Lohit on the east; the Tista joins it within Bangladesh. The Barak (Surma-Meghna) is the other major north-eastern river, draining the Manipur and Mizoram hills and joining the Ganga-Brahmaputra system in Bangladesh. The names of the river at its three stages, Tsangpo (Tibet), Siang or Dihang (Arunachal) and Brahmaputra (Assam), are a common matching trap.

Peninsular rivers

• Mahanadi: rises in the Chhattisgarh highlands, dammed at Hirakud (one of the longest dams), flows east to the Bay of Bengal through Odisha.
• Godavari: the largest peninsular river, the "Dakshina Ganga" (Ganga of the South), rises at Triambak near Nashik in Maharashtra and drains the widest peninsular basin, reaching the Bay of Bengal through a large delta in Andhra Pradesh.
• Krishna: the second-longest peninsular river, rises at Mahabaleshwar in the Western Ghats, dammed at Nagarjuna Sagar and Srisailam, flows east through Karnataka, Telangana and Andhra Pradesh.
• Kaveri: rises at Talakaveri on the Brahmagiri hills in Karnataka, the most regulated peninsular river (it gets rain from both monsoons, so it flows more steadily), forms the Shivanasamudra falls, flows through the fertile Tamil Nadu delta to the Bay of Bengal; subject of the long Karnataka-Tamil Nadu water dispute.
• Narmada: rises at Amarkantak (Maikal hills) in Madhya Pradesh, flows west through the rift between the Vindhya and Satpura ranges, makes the Dhuandhar falls at Jabalpur, is dammed at Sardar Sarovar, and reaches the Gulf of Khambhat as an estuary.
• Tapi (Tapti): rises at Multai (Betul) in Madhya Pradesh, flows west parallel to and south of the Narmada through another rift trough to the Gulf of Khambhat.

West-coast and minor rivers

Besides the Narmada and Tapi, the western seaboard has many short, swift, non-perennial streams that tumble off the Western Ghats: the Mandovi and Zuari (Goa), the Sharavati (which makes the Jog falls), the Periyar and Bharathapuzha (Kerala), and the Sabarmati and Mahi (Gujarat, flowing to the Gulf of Khambhat). The Vaigai (Madurai) and the Penna are smaller east-flowing peninsular rivers. The Subarnarekha and Brahmani drain the eastern Chota Nagpur region to the Bay of Bengal. None build large deltas because they are short and the Ghats edge is close to the sea.

Lakes

Lakes are natural (tectonic, glacial, ox-bow, lagoon, volcanic-crater) or man-made reservoirs. Wular (Jammu and Kashmir) is India's largest freshwater lake, a tectonic basin on the Jhelum. Dal (Srinagar) is a famous valley lake. Chilika (Odisha) is the largest coastal lagoon, brackish, on the east coast. Sambhar (Rajasthan) is the largest inland saltwater lake. Vembanad (Kerala) is the longest lake, a backwater. Loktak (Manipur) is famous for its floating phumdis (mats of vegetation) and hosts the only floating national park, Keibul Lamjao, the last refuge of the sangai deer. Lonar (Maharashtra) is a meteorite-impact crater lake in the Deccan basalt. Pulicat straddles Andhra Pradesh and Tamil Nadu.

River lengths and basins (orientation)

Static facts to memorise (rivers)

Tributaries reference table (high-yield matching)

Lakes by type (orientation)

Lakes and waterfalls (matching)

Major dams and multipurpose projects (matching)

The Damodar Valley Corporation (on the Damodar, modelled on the Tennessee Valley Authority) was India's first multipurpose river-valley project; the Bhakra Nangal followed as the showpiece of the Sutlej. These projects deliver irrigation, power, flood control and drinking water, the basis of the link to indian agriculture and cropping and indian industries transport and population.

Cities on rivers (matching)

Security and strategic angle

Rivers are border infrastructure and bargaining chips. The Indus system is governed by the Indus Waters Treaty of 1960, and water-sharing with Pakistan is a recurring flashpoint and a lever India can adjust within the treaty. The Brahmaputra rises in China as the Tsangpo, so any upstream dam, diversion or sudden release is a strategic concern for the lower riparian States of the north-east, and India watches Chinese hydro projects near the Great Bend closely. River borders are physically demanding to police: the Sundarbans delta and the char (shifting river-island) tracts of the Indo-Bangladesh boundary are guarded by the Border Security Force using boats and floating border outposts, because the channel shifts and the islands appear and vanish with the flood, complicating where the line even sits. The Sutlej and other riverine stretches with Pakistan, and the man-eating tiger and tidal cover of the Sundarbans, make these among the hardest frontiers in the world to hold. See india borders neighbours and strategic geography and indian monsoon and climate.

Inter-State and international water disputes (orientation)

Water sharing is a recurring federal and diplomatic theme that CAPF touches in current affairs and the security angle.

Disputes are referred to tribunals under the Inter-State River Water Disputes Act, while international rivers are governed by treaty.

How CAPF asks it

• Matching feature to location: river to its source, to its tributaries, or to the dam on it.
• Single-correct location: place a river or confluence (Devprayag, Prayagraj, the Sundarbans) on a map.
• Statement-based: judge claims such as "The Narmada and Tapi flow west through rift valleys" (correct) and "The Godavari drains into the Arabian Sea" (incorrect, the Bay of Bengal).
• One-liner: largest peninsular river (Godavari), largest freshwater lake (Wular), highest waterfall (Kunchikal).
• Pairing: dam to river; tributary to master river.

Authored practice:

1. Which one of the following rivers flows west into the Arabian Sea through a rift valley? (a) Mahanadi (b) Godavari (c) Tapi (d) Kaveri. Answer (c). The Tapi and the Narmada are the major west-flowing peninsular rivers in fault troughs.
2. The Bhagirathi and the Alaknanda join to form the Ganga at (a) Haridwar (b) Devprayag (c) Rudraprayag (d) Prayagraj. Answer (b). Below Devprayag the river is called the Ganga; it reaches the plains at Haridwar.
3. Match the river with its source. The Kaveri rises at (a) Amarkantak (b) Mahabaleshwar (c) Talakaveri (d) Triambak. Answer (c). Amarkantak is the Narmada, Mahabaleshwar the Krishna, Triambak the Godavari.
4. Consider: (1) The Brahmaputra is known as the Tsangpo in Tibet. (2) Majuli is the largest river island in the world. Which is or are correct? Answer: both. Majuli lies in the Brahmaputra in Assam.
5. The largest inland saltwater lake in India is (a) Wular (b) Sambhar (c) Chilika (d) Vembanad. Answer (b). Wular is the largest freshwater lake, Chilika the largest coastal lagoon, Vembanad the longest.
6. The city of Prayagraj (Allahabad) lies at the confluence of the Ganga with the (a) Son (b) Yamuna (c) Gomti (d) Ghaghara. Answer (b). The Triveni Sangam is the meeting of the Ganga and the Yamuna.
7. India's tallest dam is built on the (a) Sutlej (b) Mahanadi (c) Bhagirathi (d) Krishna. Answer (c). The Tehri dam is on the Bhagirathi in Uttarakhand; Bhakra is on the Sutlej, Hirakud on the Mahanadi.
8. Which river forms the Sundarbans delta jointly with the Ganga? (a) Mahanadi (b) Brahmaputra (c) Godavari (d) Krishna. Answer (b). The Ganga and the Brahmaputra (with the Meghna) build the world's largest delta.
9. The Kosi, infamous as the "sorrow of Bihar", is a tributary of the (a) Yamuna (b) Brahmaputra (c) Ganga (d) Son. Answer (c). The Kosi is a left-bank Ganga tributary that shifts course and floods.

Common confusion

• Godavari (largest peninsular river, to the Bay of Bengal) versus Narmada (largest west-flowing, to the Arabian Sea).
• Wular (largest freshwater) versus Sambhar (largest inland salt) versus Chilika (largest coastal lagoon) versus Vembanad (longest).
• Chambal and Betwa join the Yamuna, not the Ganga directly; the Yamuna then joins the Ganga at Prayagraj.
• The Tsangpo (Brahmaputra in Tibet) versus the Sutlej (also rises near Mansarovar); both gorge through the Himalayas.
• Kunchikal (highest waterfall, on the Varahi) versus Jog (on the Sharavati, the famous segmented fall).
• Krishna rises at Mahabaleshwar; the Kaveri at Talakaveri; do not swap them.
• Godavari source is Triambak (Nashik); Krishna source is Mahabaleshwar; both flow east; only the Narmada and Tapi go west.
• The Sutlej and the Indus both rise near Lake Mansarovar; the Sutlej is dammed at Bhakra, the Indus is governed by the treaty.
• Jhelum (Wular Lake, Srinagar) versus Chenab (largest of the five, formed at Tandi); both are western Indus rivers under Pakistan's share.

Memory hook

• Five rivers of Punjab, west to east: "Jolly Chaps Ride Bikes Slowly" for Jhelum, Chenab, Ravi, Beas, Sutlej.
• Ganga left-bank tributaries upstream-down: "Really Good Girls Get Kissed" for Ramganga, Gomti, Ghaghara, Gandak, Kosi.
• West-flowing peninsular pair: "NT" for Narmada and Tapi (the only big ones going to the Arabian Sea).
• Indus Waters Treaty: India keeps the eastern rivers (Ravi, Beas, Sutlej), Pakistan the western (Indus, Jhelum, Chenab).
• Panch Prayag end at Devprayag: "Vishnu, Nand, Karna, Rudra, Dev" for the order down the Alaknanda.
• "Godavari is the biggest peninsular, the Dakshina Ganga" fixes the largest east-flowing river.
• Dams to rivers: "Bhakra-Sutlej, Hirakud-Mahanadi, Sardar Sarovar-Narmada, Tehri-Bhagirathi, Nagarjuna Sagar-Krishna."

The five Prayags of the Ganga headwaters

The Alaknanda gathers its head-tributaries at five sacred confluences (the Panch Prayag), a favourite ordering question:

• Vishnuprayag: Alaknanda meets the Dhauliganga.
• Nandprayag: Alaknanda meets the Nandakini.
• Karnaprayag: Alaknanda meets the Pindar.
• Rudraprayag: Alaknanda meets the Mandakini.
• Devprayag: Alaknanda meets the Bhagirathi, below which the river is called the Ganga.

Night before

• Himalayan rivers perennial (snow plus rain); peninsular rivers mostly seasonal.
• Indus near Mansarovar; Indus Waters Treaty 1960; east rivers to India, west rivers to Pakistan.
• Ganga starts at Devprayag (Bhagirathi plus Alaknanda); plains at Haridwar; Yamuna joins at Prayagraj.
• Godavari largest peninsular ("Dakshina Ganga"); Narmada and Tapi flow west to the Gulf of Khambhat.
• Wular largest freshwater, Chilika largest lagoon, Sambhar largest inland salt, Vembanad longest, Loktak phumdis.
• Kunchikal highest waterfall, Jog on the Sharavati; Bhakra on the Sutlej, Hirakud on the Mahanadi.
• Panch Prayag end at Devprayag, where the Ganga is named; the headwater confluences are an ordering favourite.
• Damodar Valley Corporation was the first multipurpose project; Tehri (Bhagirathi) is the tallest dam.

Glossary

• Drainage basin: the whole area drained by a river and its tributaries.
• Watershed (water divide): the high ground separating two basins.
• Perennial river: a river that flows all year, like the Himalayan rivers fed by snowmelt.
• Antecedent river: a river older than the mountains it crosses, having cut its gorge as the land rose.
• Tributary: a stream that flows into a larger river; a distributary is a channel that branches off near the mouth.
• Confluence: the meeting point of two rivers (Devprayag, Prayagraj).
• Delta: a fan of sediment built where a river meets the sea (the Sundarbans).
• Estuary: a funnel-shaped tidal mouth without a delta (the Narmada and Tapi mouths).
• Ox-bow lake: a curved lake left when a meander is cut off.
• Lagoon: a shallow coastal water body separated from the sea by a bar (Chilika, Pulicat).
• Phumdi: a floating mat of vegetation, characteristic of Loktak Lake.
• Char: a shifting river-island of silt, important on the Indo-Bangladesh riverine border.
• Riparian State: a State or country through which, or along which, a river flows; "lower riparian" is downstream.
• Doab: the land between two rivers, as in the Punjab and the Ganga-Yamuna doab.
• Braided river: a river splitting into many shifting channels around sandbars, like the Brahmaputra.
• Meander: a looping bend in a mature river across its floodplain.
• Sangam / Prayag: a sacred river confluence, the most famous at Prayagraj (Ganga and Yamuna).
• Multipurpose project: a dam serving irrigation, power, flood control and water supply together.
• Drainage divide (watershed): the high ground separating two river basins.
• Trellis pattern: a drainage pattern of right-angle joins, formed on folded or faulted rock.
• Panch Prayag: the five sacred head-confluences of the Alaknanda, ending at Devprayag.
• Indus Waters Treaty: the 1960 World-Bank-brokered pact dividing the Indus rivers between India and Pakistan.
• Antecedent gorge: a deep valley cut by a river older than the mountain it crosses (the Indus and Sutlej gorges).
• Endorheic basin: an inland drainage with no outlet to the sea (Sambhar, the Rann).
• Barrage: a low diversion dam to raise water level and direct flow (Farakka on the Ganga).
• Namami Gange / Ganga Action Plan: the river clean-up and conservation programmes for the Ganga.
• Phumdi: a floating mat of soil and vegetation, the signature feature of Loktak Lake in Manipur.

Related notes

• india physiography
• indian monsoon and climate
• indian agriculture and cropping
• minerals and energy resources of india
• india borders neighbours and strategic geography
• syllabus index