Drainage System of India – NDA Geography Notes

India has one of the world’s richest river systems. Rivers have shaped India’s landscape, supported its agriculture, and built its civilisations. Almost every major city (Delhi, Patna, Varanasi, Kolkata, Hyderabad) sits on a riverbank.

NDA tests this chapter heavily. Questions come from river origins, tributaries, which river flows through which state, river-city pairs, dams, and lakes. River questions appear in almost every NDA paper.

The key is to understand the pattern, not to memorise every detail. Once you understand why Himalayan rivers behave differently from Peninsular rivers, everything else falls into place.

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What is a Drainage System?

A drainage system is a network of rivers and their branches that collects water from a region and carries it to the sea, a lake, or another river. The area drained by a single river and all its branches is called a drainage basin or catchment area. The boundary line separating two drainage basins is called a watershed or water divide.

In India, the Western Ghats act as the most important watershed. Rivers west of the Western Ghats flow into the Arabian Sea. Rivers east of them flow into the Bay of Bengal.

When rivers from all directions discharge water into a lake or depression, the drainage pattern is called centripetal.

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Two Types of Rivers in India

Feature	Himalayan Rivers	Peninsular Rivers
Source	Glaciers and snowfields	Rain, springs, rocky plateaus
Flow	Perennial: flow all year	Seasonal: depend on monsoon rain
Nature	Young, fast, carry heavy silt	Old, slow, broad, shallow valleys
Valley	Deep V-shaped gorges	Broad, shallow
Stage	All three stages of erosion	Have reached maturity
Examples	Ganga, Yamuna, Brahmaputra	Godavari, Krishna, Cauvery

Himalayan rivers are perennial. They carry glacial meltwater even in summer. The claim that “Himalayan rivers are dry in winter” is wrong. They flow throughout the year.

Peninsular rivers have reached maturity. They flow in broad, old, shallow valleys because the plateau is ancient and hard.

East-flowing Peninsular rivers form deltas because they flow slowly through soft rocks and deposit sediment before reaching the sea. West-flowing rivers do not form deltas. They originate in the Western Ghats, have a short distance to cover, flow fast, and carry their sediment all the way to the sea. They form estuaries instead.

Antecedent Drainage

Some Himalayan rivers, like the Indus, Sutlej, and Brahmaputra, are older than the Himalayas. They were flowing before the mountains rose. As the mountains slowly rose, these rivers kept cutting downward and maintained their original course. This is called antecedent drainage. That is why they cut deep gorges through the mountains instead of going around them. [NDA 2010-II | NDA 2024-II]

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The Indus River System

The Indus is one of the longest rivers in Asia. Most of it flows through Pakistan. It originates in the Mansarovar Lake region in Tibet, near Mount Kailash, enters India through Ladakh, and drains into the Arabian Sea in Pakistan. Its total length is about 3,180 km.

The Five Rivers of Punjab

The word Punjab means “land of five rivers.” The five rivers are: Jhelum, Chenab, Ravi, Beas, and Sutlej.

Tributary	Origin	Key Fact
Jhelum	Verinag spring, Kashmir Valley	Flows through Wular Lake; enters Pakistan
Chenab	Bara Lacha La pass, HP	Longest tributary of Indus
Ravi	Near Kullu, HP	Flows past Chamba
Beas	Beas Kund near Rohtang Pass, HP	Flows through Kullu Valley; joins Sutlej
Sutlej	Rakshas Tal lake, Tibet (called Langchen Khambab)	Enters India at Shipki La; antecedent river

The Sutlej originates in Tibet where it is known as Langchen Khambab. It is a classic example of an antecedent river. [NDA 2024-II]

The Jhelum is NOT the largest tributary of the Indus. Chenab is the longest tributary. [NDA 2024-II]

Wular Lake, India’s largest freshwater lake, is in the Kashmir Valley. The Jhelum River flows into and out of Wular Lake. Dal Lake is also in Kashmir, famous for its houseboats and floating vegetable gardens called Rad.

Indus Waters Treaty

Under the Indus Waters Treaty between India and Pakistan: Eastern Rivers (Sutlej, Beas, Ravi) are allocated to India; Western Rivers (Indus, Jhelum, Chenab) are allocated to Pakistan.

Hydropower projects on Chenab: Bagalihar, Dulhasti, and Salal hydropower projects are all built on the Chenab River. [NDA 2020-I]

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The Ganga River System

The Ganga is India’s most important river, culturally, economically, and geographically. It drains the largest river basin in India.

The Ganga originates at Gangotri Glacier in Uttarakhand. The river emerges from a glacier snout called Gomukh. The Bhagirathi (which starts at Gangotri) meets the Alaknanda at Devprayag. From this confluence the combined river is called the Ganga. It flows through Uttarakhand, UP, Bihar, Jharkhand (partially), and West Bengal, draining into the Bay of Bengal through the Sundarbans delta. Its length is about 2,525 km.

The Panch Prayag : Five Confluences in Uttarakhand

Confluence	Rivers That Meet	Location
Vishnuprayag	Alaknanda + Dhauliganga	Uttarakhand
Nandaprayag	Alaknanda + Nandakini	Uttarakhand
Karnaprayag	Alaknanda + Pindar	Uttarakhand
Rudraprayag	Alaknanda + Mandakini	Uttarakhand
Devprayag	Alaknanda + Bhagirathi	Ganga begins here

Left Bank Tributaries (Himalayan Origin)

River	Origin	Key Fact
Ramganga	Garhwal Himalayas	Joins Ganga near Kannauj
Gomti	Gomat Taal lake, UP	Flows through Lucknow
Ghaghra (Karnali)	Near Mansarovar, Tibet	Largest tributary of Ganga by volume
Gandak	Nepal Himalayas	Joins Ganga at Sonpur, Bihar
Kosi	Nepal Himalayas	Called Sorrow of Bihar

Kosi River is called the Sorrow of Bihar. It frequently changes course and causes devastating floods in Bihar every year. It has shifted its course westward by about 120 km over 200 years.

Right Bank Tributaries (Peninsular Origin)

River	Origin	Key Fact
Yamuna	Yamunotri Glacier, Uttarakhand	Longest tributary of Ganga; joins at Prayagraj
Son	Amarkantak plateau, MP	Joins Ganga near Patna
Chambal	Vindhya range, MP	Famous for deep ravines; joins Yamuna
Betwa	Vindhya range, MP	Joins Yamuna
Ken	Vindhya range, MP	Joins Yamuna; Ken-Betwa Link Project

Yamuna originates at Yamunotri Glacier in Uttarakhand, is the longest tributary of the Ganga, flows through Delhi, Agra, and Mathura, and meets the Ganga at Prayagraj (Allahabad), the Triveni Sangam.

Chambal River originates in the Vindhya Range in MP. It is famous for its ravines (badlands), deeply eroded, rugged terrain carved by intensive gully erosion. Gandhi Sagar Dam on the Chambal is in Madhya Pradesh. [NDA 2007-I]

Son River originates at Amarkantak in MP, the same plateau where the Narmada also starts. Son flows northeast toward the Ganga; the Narmada flows southwest toward the Arabian Sea. They start from the same place but flow in opposite directions.

Chambal and Betwa join the Yamuna, not the Ganga directly. [NDA 2024-I]

Ganga Basin States: Chhattisgarh is part of the Ganga Basin (through the Son River). Himachal Pradesh and Rajasthan are NOT part of the Ganga Basin.

The Sundarbans

The Ganga meets the Bay of Bengal through the world’s largest delta, the Sundarbans. This delta is shared between India (West Bengal) and Bangladesh. It is covered by mangrove forests and is home to the Royal Bengal Tiger. It is a UNESCO World Heritage Site. In West Bengal, the Ganga flows as the Hooghly River past Kolkata toward the sea.

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The Brahmaputra River System

The Brahmaputra is one of the world’s mightiest rivers. It is unusual because it flows from east to west for much of its course before turning south.

It originates at the Chemayungdung glacier near Mansarovar Lake in Tibet, where it is called Tsangpo (or Yarlung Tsangpo). It enters India through Arunachal Pradesh as the Dihang (or Siang). [NDA 2024-I] In Assam, it is called Brahmaputra, flowing westward through the Assam Valley. In Bangladesh, it is called the Jamuna and drains into the Bay of Bengal.

The Great Bend: Near Namcha Barwa peak in Arunachal Pradesh, the Brahmaputra takes a dramatic U-turn, from flowing east to flowing west and then south. This creates one of the world’s deepest gorges.

Majuli Island in Assam is the world’s largest river island, located in the Brahmaputra. [NDA 2018-II] The Brahmaputra causes severe floods in Assam every year during the monsoon.

Main Tributaries of the Brahmaputra in India

Tributary	Side	Key Fact
Subansiri	Left (north)	Largest tributary of Brahmaputra in India
Lohit	Left (north)	Joins near Sadiya, Assam
Dibang	Left (north)	Eastern Assam
Manas	Right (south)	Flows through Manas National Park
Teesta	Right (south)	From Sikkim; joins Brahmaputra in Bangladesh
Puthimari	Right (south)	Tributary of Brahmaputra

Ghaggar River (different from Ghaghra) does NOT drain into the sea. It gets lost in the Rajasthan desert. Barak River rises in Manipur (not Meghalaya) and is the headstream of the Meghna. Brahmani River is formed by the confluence of the Kosi and Sankh rivers in Jharkhand/Odisha. [NDA 2022-II]

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Peninsular River Systems

Peninsular rivers flow from the Peninsular Plateau, depend mostly on monsoon rainfall, and are seasonal. They swell in the monsoon and shrink in summer. The Western Ghats act as the main watershed. Most major rivers flow eastward because the plateau slopes from west to east.

Eastward Flowing Rivers (Bay of Bengal)

Mahanadi River

It originates at Sihawa in Chhattisgarh (Dandakaranya plateau) and flows through Chhattisgarh and Odisha before draining into the Bay of Bengal near Cuttack. Hirakud Dam, one of the world’s longest earthen dams, is on the Mahanadi in Odisha, with its reservoir near Sambalpur. [NDA 2006-I] Chilika Lake lies near the Mahanadi delta.

Godavari River

Godavari originates at Trimbakeshwar near Nashik, Maharashtra (Western Ghats) and flows through Maharashtra, Telangana, and Andhra Pradesh before draining into the Bay of Bengal near Rajahmundry.

At about 1,465 km, it is the longest Peninsular River and is called “Dakshin Ganga” (Ganga of the South). Its tributaries include Wardha, Pranhita, Indravati, and Manjira. Godavari has the second-largest river basin in India, covering about 10% of India’s area. [NDA 2024-I]

The Indravati River (a tributary of the Godavari) flows through Chhattisgarh and is famous for the Chitrakoot Waterfalls.

Krishna River

The Krishna River originates near Mahabaleshwar, Maharashtra (Western Ghats) and flows through Maharashtra, Karnataka, and Andhra Pradesh before draining into the Bay of Bengal near Vijayawada. Its length is about 1,400 km.

Tungabhadra is the most important tributary of the Krishna. The Hampi ruins are on its banks. Musi River flows through Hyderabad. Nagarjuna Sagar Dam is on the Krishna River. [NDA 2016-I] Srisailam Dam and Alamatti Dam are also on the Krishna.

Cauvery River (Kaveri)

It originates at Talakaveri in the Brahmagiri Hills, Kodagu (Coorg), Karnataka and flows through Karnataka and Tamil Nadu before draining into the Bay of Bengal near Poompuhar. Its length is about 800 km. Shivasamudram Falls is a famous waterfall on the Cauvery in Karnataka. India’s first major hydroelectric station was built here. Krishnarajasagara (KRS) Dam is in Karnataka; Mettur Dam (which forms Stanley Reservoir) is in Tamil Nadu. Kabini River is a tributary of the Cauvery. The Cauvery water dispute involves Kerala, Karnataka, Tamil Nadu, and Puducherry.

Pennar River

It flows through Karnataka and Andhra Pradesh, draining into the Bay of Bengal.

Kolleru Lake in Andhra Pradesh is a large freshwater lake between the deltas of the Krishna and Godavari rivers and a Ramsar wetland site.

Westward Flowing Rivers (Arabian Sea)

Most Peninsular rivers flow east. Only a few flow west, and these have distinctive characteristics.

Narmada River

The Narmada originates in the Amarkantak Plateau, Madhya Pradesh, and flows through MP, Maharashtra, and Gujarat before draining into the Arabian Sea at the Gulf of Khambhat. At about 1,312 km, it is India’s longest west-flowing river.

The Narmada flows through a rift valley, a valley formed by the sinking of land between two parallel faults (structural origin). Narmada does NOT form a delta. It forms an estuary. Marble Rocks (Bhedaghat) near Jabalpur is a famous gorge where the river flows between white marble cliffs. Dhuandhar Falls is the dramatic waterfall at Bhedaghat.

Tapti (Tapi) River

Tapti River originates in the Satpura range, Betul district, Madhya Pradesh, and flows through MP, Maharashtra, and Gujarat before draining into the Arabian Sea at the Gulf of Khambhat near Surat. Like the Narmada, it also flows through a rift valley between the Satpura range (north) and the Ajanta range (south), and also forms an estuary, not a delta. Ukai Dam is on the Tapti (Tapi) River in Gujarat.

Both Narmada and Tapti flow through rift valleys and form estuaries. Both drain into the Gulf of Khambhat.

Luni River

It originates in the Aravalli Hills near Pushkar, Rajasthan, and flows southwest through Rajasthan into the Rann of Kutch in Gujarat. It is the only significant river in the Thar Desert. Its lower course is saline and unsuitable for drinking or farming. The Luni does NOT reach the sea. It disappears into the Rann of Kutch.

Mahi River

It originates in MP, flows through Rajasthan and Gujarat, and drains into the Gulf of Khambhat.

Sabarmati River

It originates in the Aravalli Hills in Rajasthan, flows through Gujarat, and drains into the Gulf of Khambhat near Ahmedabad. Mahatma Gandhi’s Sabarmati Ashram was on its banks.

Periyar River

It is Kerala’s longest river. It flows through the Periyar Wildlife Sanctuary.

Sharavati River

It is famous for creating Jog Falls (Gersoppa Falls), the highest waterfall in India at about 253 metres, in Karnataka. [NDA 2022-II] The Mahatma Gandhi Hydroelectric Project is on the Sharavati River in Karnataka. [NDA 2008-I]

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Important Dams and Projects

Dam / Project	River	State	Key Fact
Hirakud Dam	Mahanadi	Odisha	One of the longest earthen dams; reservoir near Sambalpur [NDA 2006-I]
Bhakra Nangal Dam	Sutlej	HP / Punjab	Feeds Bhakra Canal: most important canal in Haryana [NDA 2015-I]
Gandhi Sagar Dam	Chambal	Madhya Pradesh	[NDA 2007-I]
Nagarjuna Sagar Dam	Krishna	Andhra Pradesh	[NDA 2016-I]
Srisailam Dam	Krishna	Andhra Pradesh	—
Alamatti Dam	Krishna	Karnataka	NOT on Cauvery [NDA 2007-II]
Mettur Dam	Cauvery	Tamil Nadu	Forms Stanley Reservoir: NOT on Krishna [NDA 2007-II]
KRS (Krishnarajasagara)	Cauvery	Karnataka	—
Ukai Dam	Tapi (Tapti)	Gujarat	[NDA 2014-II]
Tehri Dam	Bhagirathi	Uttarakhand	—
GB Pant Sagar (Rihand)	Rihand	Uttar Pradesh	—
Bagalihar Dam	Chenab	J&K	All three on Chenab only [NDA 2020-I]
Dulhasti Dam	Chenab	J&K	—
Salal Dam	Chenab	J&K	—
Ranjit Sagar Dam	Ravi	Punjab	NOT on Beas [NDA 2007-I]

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Lakes of India

Freshwater Lakes

Lake	State	Type	Key Fact
Wular Lake	J&K	Freshwater (tectonic)	Largest freshwater lake in India; Jhelum flows through it
Dal Lake	J&K	Freshwater (residual)	Famous houseboats; floating gardens called Rad
Loktak Lake	Manipur	Freshwater	Largest freshwater lake in NE India; Phumdis; Keibul Lamjao NP (world’s only floating national park)
Kolleru Lake	Andhra Pradesh	Freshwater	Between Krishna-Godavari deltas; Ramsar site
Bhimtal Lake	Uttarakhand	Freshwater (tectonic)	Larger than Nainital but less famous
Roopkund Lake	Uttarakhand	Glacial	Famous for skeletal remains; “Skeleton Lake” [NDA 2023-II]
Tsomgo Lake	Sikkim	Glacial	—
Pangong Tso	Ladakh	Glacial	Extends into China
Tso Kar	Ladakh	Salt lake	—
Tso Moriri	Ladakh	High altitude	—

Lake types to know: Bhimtal = Tectonic | Ashtamudi = Lagoon | Gohna Lake = Landslide lake | Lonar Lake = Crater (meteorite impact) | Tsomgo = Glacial | Dal Lake = Residual

Saltwater and Brackish Lakes

Lake	State	Type	Key Fact
Chilika Lake	Odisha	Brackish (lagoon)	Largest coastal lagoon in India; largest brackish lake in Asia; Ramsar site; migratory birds
Vembanad Lake	Kerala	Brackish	Longest lake in India; west coast backwaters
Ashtamudi Lake	Kerala	Lagoon	On the west coast [NDA 2014-I]
Pulicat Lake	AP / TN	Brackish	Second largest brackish lake in India; flamingo habitat
Sambhar Lake	Rajasthan	Saltwater	Largest saltwater lake in India; Ramsar site; highest salinity in India
Lonar Lake	Maharashtra	Saline + alkaline	Crater lake (meteorite impact); formed in basaltic rock; contains mineral found on the Moon [NDA 2021-II]

Lonar Lake formed from a meteorite impact, not volcanic activity. It is unique because it is formed in basaltic rock. The water is both saline and alkaline. It contains maskelynite, a substance also found on the Moon. [NDA 2021-II]

West coast lakes: Ashtamudi and Vembanad are on the west coast. Chilika, Pulicat, and Kolleru are on the east coast. [NDA 2014-I]

Barapani Lake (Umiam Lake) is in Meghalaya. Panchmuli Lake is near the Statue of Unity in Gujarat. Lakes in Ladakh: Tso Kar, Pangong Tso, and Tso Moriri. Tsomgo is in Sikkim, not Ladakh.

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Waterfalls in India

Waterfall	River	State	Note
Jog Falls (Gersoppa Falls)	Sharavati	Karnataka	Highest waterfall in India (~253 m) [NDA 2022-II]
Chitrakoot Falls	Indravati	Chhattisgarh	—
Dhuandhar Falls	Narmada	Madhya Pradesh	At Bhedaghat (Marble Rocks), Jabalpur
Shivasamudram Falls	Cauvery	Karnataka	Site of India’s first major hydroelectric station
Dudhsagar Falls	—	Goa	—
Barkana Falls	—	Karnataka	—
Duduma Falls	—	Odisha	—
Kiliyur Falls	—	Tamil Nadu	—

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