Drainage System of India – NDA Geography Notes

Introduction

India has one of the richest river systems in the world. 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 river bank.

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.

Understand the Topic

What is a Drainage System?

A drainage system is a network of rivers and their branches that collect water from a region and carry it to the sea, 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. [NDA tested via CDS]

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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 statement that “Himalayan rivers are dry in winter” is WRONG. They flow throughout the year. [NDA tested via CDS]

Peninsular rivers have reached maturity — they flow in broad, old, shallow valleys because the plateau is ancient and hard. [NDA tested via CDS]

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. They 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]

The Indus River System

The Indus is one of the longest rivers in Asia. Most of it flows through Pakistan.

• Origin: Mansarovar Lake region in Tibet, near Mount Kailash
• Enters India: Through Ladakh
• Drains into: Arabian Sea (in Pakistan)
• Total length: About 3,180 km

Main tributaries of the Indus — 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]

Indus Waters Treaty:
Under the Indus Waters Treaty between India and Pakistan:

• Eastern Rivers = Sutlej, Beas, and Ravi (given to India)
• Western Rivers = Indus, Jhelum, and Chenab (given to Pakistan)
  [NDA tested via CDS]

Wular Lake — the largest freshwater lake in India — is in the Kashmir Valley. The Jhelum River flows into and out of Wular Lake.

Dal Lake is also in Kashmir. It is famous for its houseboats and floating vegetable gardens called Rad. [NDA tested via CDS]

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

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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.

• Origin: Gangotri Glacier in Uttarakhand. The river emerges from a glacier snout called Gomukh.
• Ganga begins at Devprayag: The Bhagirathi (which starts at Gangotri) meets the Alaknanda here. From this point, the combined river is called the Ganga.
• Flows through: Uttarakhand, UP, Bihar, Jharkhand (partially), West Bengal
• Drains into: Bay of Bengal through the Sundarbans delta
• Length: About 2,525 km

The Panch Prayag (Five Confluences) in Uttarakhand:

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 (from the north — 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 (from the south — 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 River:

• Originates at Yamunotri Glacier in Uttarakhand
• Longest tributary of the Ganga
• Flows through Delhi, Agra, Mathura
• Meets the Ganga at Prayagraj (Allahabad) — called Triveni Sangam

Chambal River:

• Originates in the Vindhya Range in MP
• Famous for its ravines (badlands) — deeply eroded, rugged terrain
• The Chambal valley is under intensive gully erosion. [NDA tested via CDS]
• Gandhi Sagar Dam on the Chambal is in Madhya Pradesh. [NDA 2007-I | NDA tested via CDS]

Son River:

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

Ganga Basin States:
Chhattisgarh is part of the Ganga Basin (through Son River). Himachal Pradesh and Rajasthan are NOT part of the Ganga Basin. [NDA tested via CDS]

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 mightiest rivers in the world. It is unusual because it flows from east to west for a large part of its course before turning southward.

• Origin: Chemayungdung glacier near Mansarovar Lake in Tibet
• Name in Tibet: Tsangpo (or Yarlung Tsangpo)
• Enters India: Through Arunachal Pradesh, called Dihang (or Siang) [NDA 2024-I]
• In Assam: Called Brahmaputra — flows westward through the Assam Valley
• In Bangladesh: Called Jamuna
• Drains into: 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 deepest gorges in the world.

Majuli Island in Assam is the world’s largest river island — it is in the Brahmaputra. [NDA 2018-II]

The Brahmaputra causes severe floods in Assam every year during the monsoon.

Main tributaries of 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 [NDA tested via CDS]

Ghaggar River (different from Ghaghra) does NOT drain into the sea. It gets lost in the Rajasthan desert. [NDA tested via CDS]

Barak River rises in Manipur (NOT Meghalaya) and is the headstream of the Meghna. [NDA tested via CDS]

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. They depend mostly on monsoon rainfall. They are seasonal — they swell in the monsoon and shrink in summer.

The Western Ghats act as the main watershed for Peninsular rivers. Most major rivers flow eastward because the plateau slopes from west to east.

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 because they originate in the Western Ghats and have a short distance to cover — they reach the sea quickly. [NDA tested via CDS]

Eastward Flowing Peninsular Rivers (Bay of Bengal)

Mahanadi River:

• Origin: Sihawa in Chhattisgarh (Dandakaranya plateau)
• Flows through: Chhattisgarh, Odisha
• Drains into: Bay of Bengal near Cuttack, Odisha
• Hirakud Dam — one of the longest earthen dams in the world — is on the Mahanadi in Odisha. The reservoir is near Sambalpur. [NDA 2006-I]
• Chilika Lake is near the Mahanadi delta

Godavari River:

• Origin: Trimbakeshwar near Nashik, Maharashtra (Western Ghats)
• Flows through: Maharashtra, Telangana, Andhra Pradesh
• Drains into: Bay of Bengal near Rajahmundry, Andhra Pradesh
• Length: About 1,465 km — longest Peninsular river
• Called: “Dakshin Ganga” (Ganga of the South)
• Tributaries: Wardha, Pranhita, Indravati, Manjira
• Godavari has the second largest river basin in India — covering about 10% of India’s area. [NDA 2024-I]
• The Indravati River (tributary of Godavari) flows through Chhattisgarh — famous for Chitrakoot Waterfalls

Krishna River:

• Origin: Near Mahabaleshwar, Maharashtra (Western Ghats)
• Flows through: Maharashtra, Karnataka, Andhra Pradesh
• Drains into: Bay of Bengal near Vijayawada, Andhra Pradesh
• Length: About 1,400 km
• Tungabhadra is the most important tributary of Krishna — Hampi ruins are on its banks
• Musi River flows through Hyderabad
• Nagarjuna Sagar Dam is on the Krishna River. [NDA 2016-I]
• Srisailam Dam is also on the Krishna River. [NDA tested via CDS]
• Krishna and Tungabhadra flow in the region between Gulbarga and Vijayanagara (Hampi). [NDA tested via CDS]

Cauvery River (Kaveri):

• Origin: Talakaveri in Brahmagiri Hills, Kodagu (Coorg), Karnataka
• Flows through: Karnataka, Tamil Nadu
• Drains into: Bay of Bengal near Poompuhar, Tamil Nadu
• Length: About 800 km
• Shivasamudram Falls — famous waterfall on the Cauvery in Karnataka; India’s first major hydroelectric station was built here
• Krishnarajasagara (KRS) Dam in Karnataka — state: Karnataka
• Mettur Dam in Tamil Nadu — forms Stanley Reservoir
• Kabini River is a tributary of the Cauvery. [NDA tested via CDS]
• The Cauvery water dispute is between Kerala, Karnataka, Tamil Nadu, and Puducherry. [NDA tested via CDS]

Pennar River: Flows through Karnataka and Andhra Pradesh; drains into Bay of Bengal.

Kolleru Lake:

• A large freshwater lake in Andhra Pradesh
• Located between the deltas of Krishna and Godavari rivers
• A Ramsar wetland site

Westward Flowing Peninsular Rivers (Arabian Sea)

Most Peninsular rivers flow east. Only a few flow west.

Narmada River:

• Origin: Amarkantak plateau, Madhya Pradesh
• Flows through: MP, Maharashtra, Gujarat
• Drains into: Arabian Sea at Gulf of Khambhat
• Length: About 1,312 km — longest west-flowing river in India
• The Narmada flows through a rift valley — a valley formed by the sinking of land between two parallel faults. This is called structural origin. [NDA tested via CDS]
• Narmada does NOT form a delta. It forms an estuary — it flows fast and carries sediment all the way to the sea.
• Marble Rocks (Bhedaghat) — a famous gorge near Jabalpur where the river flows between white marble cliffs
• Dhuandhar Falls — a dramatic waterfall at Bhedaghat

Tapti (Tapi) River:

• Origin: Satpura range, Betul district, Madhya Pradesh
• Flows through: MP, Maharashtra, Gujarat
• Drains into: Arabian Sea at Gulf of Khambhat near Surat
• Like Narmada, Tapti also flows through a rift valley — between Satpura range (north) and Ajanta range (south)
• Also forms an estuary, not a delta
• Ukai Dam is on the Tapti (Tapi) River in Gujarat. [NDA tested via CDS]

Both Narmada and Tapti flow through rift valleys and form estuaries. Both drain into the Gulf of Khambhat. [NDA tested via CDS]

Luni River:

• Originates in the Aravalli Hills near Pushkar, Rajasthan
• Flows southwest through Rajasthan into the Rann of Kutch in Gujarat
• The only significant river in the Thar Desert
• Saline (salty) in its lower course — not drinkable or suitable for farming
• Does NOT reach the sea — disappears into the Rann of Kutch

Mahi River:

• Originates in MP; flows through Rajasthan and Gujarat
• Drains into the Gulf of Khambhat
• The Tropic of Cancer crosses the Mahi River twice (covered in Chapter 1)

Sabarmati River:

• Originates in Aravalli Hills, Rajasthan
• Flows through Gujarat; drains into Gulf of Khambhat near Ahmedabad
• Mahatma Gandhi’s Sabarmati Ashram was on its banks

Short West-Flowing Rivers of Kerala and Karnataka:

Periyar River — longest river in Kerala; flows through Periyar Wildlife Sanctuary.

Sharavati River — famous for Jog Falls (Gersoppa Falls) — the highest waterfall in India at about 253 metres. Located in Karnataka. [NDA 2022-II]

Mahatma Gandhi Hydroelectric Project is on the Sharavati River, Karnataka. [NDA 2008-I]

Important Dams and Projects

Dam/Project	River	State	Notes
Hirakud Dam	Mahanadi	Odisha	One of longest earthen dams; reservoir near Sambalpur [NDA 2006-I]
Bhakra Nangal Dam	Sutlej	HP/Punjab	Feeds canal system in Haryana/Punjab
Gandhi Sagar	Chambal	Madhya Pradesh	**[NDA 2007-I
Nagarjuna Sagar	Krishna	Andhra Pradesh	[NDA 2016-I]
Srisailam Dam	Krishna	Andhra Pradesh	—
Ukai Dam	Tapi	Gujarat	NOT hydropower — thermal power nearby [NDA 2014-II]
KRS (Krishnarajasagara)	Cauvery	Karnataka	—
Mettur Dam	Cauvery	Tamil Nadu	Forms Stanley Reservoir
Tehri Dam	Bhagirathi	Uttarakhand	—
Rihand/GB Pant Sagar	Rihand	Uttar Pradesh	[NDA tested via CDS]
Bagalihar/Dulhasti/Salal	Chenab	J&K	[NDA 2020-I]
Ranjit Sagar Dam	Ravi (NOT Beas)	Punjab	[NDA 2007-I]

Ranjit Sagar Dam is on the Ravi River — NOT the Beas. Statement saying it is on Beas is WRONG. [NDA 2007-I]

Hirakud Dam is on the Mahanadi — NOT the Damodar. Statement saying it is on Damodar is WRONG. [NDA 2007-I]

Alamatti Dam is on the Krishna — NOT Cauvery. [NDA 2007-II]

Mettur Dam is on the Cauvery — NOT Krishna. [NDA 2007-II]

Bhakra Nangal is fed by the Sutlej River. [NDA tested via CDS]

Most important canal in Haryana by area coverage = Bhakra Canal. [NDA 2015-I]

Baglihar, Dulhasti, Salal = all on Chenab River only. [NDA 2020-I]

Nagarjuna Sagar Project is on the Krishna River. [NDA 2016-I]

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Lakes of India

Freshwater Lakes:

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

Lake Types:

• Bhimtal = Tectonic lake
• Ashtamudi = Lagoon
• Gohna Lake = Landslide lake (formed when a landslide dams a river)
• Lonar Lake = Crater (meteorite impact) [NDA tested via CDS]
• Tsomgo = Glacial lake
• Dal Lake = Residual (natural, spring-fed) lake

Saltwater / Brackish Lakes:

Lake	State	Key Fact
Chilika Lake	Odisha	Largest coastal lagoon in India; largest brackish lake in Asia; Ramsar site; migratory birds
Vembanad Lake	Kerala	Longest lake in India; west coast backwaters
Ashtamudi Lake	Kerala	Lagoon; on west coast [NDA 2014-I]
Pulicat Lake	AP/TN	Second largest brackish lake in India; flamingo habitat
Sambhar Lake	Rajasthan	Largest saltwater lake in India; Ramsar site; highest salinity in India [NDA tested via CDS]
Lonar Lake	Maharashtra	Crater lake; formed by meteorite; saline + alkaline; has minerals found on Moon **[NDA 2021-II

Lonar Lake in Maharashtra was formed by a meteorite impact — not by volcanic activity. It is unique because it is formed in basaltic rock. The water is both saline and alkaline. It contains a large quantity of a substance found on the Moon. [NDA 2021-II | NDA tested via CDS]

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

Lakes in Ladakh: Tso Kar, Pangong Tso, and Tso Moriri are in Ladakh. Tsomgo is in Sikkim. [NDA tested via CDS]

Panchmuli Lake is near the Statue of Unity in Gujarat. [NDA tested via CDS]

Barapani Lake (Umiam Lake) is in Meghalaya. [NDA tested via CDS]

Waterfalls in India

Waterfall	River	State
Jog Falls (Gersoppa Falls)	Sharavati	Karnataka — highest in India (~253 m)
Chitrakoot Falls	Indravati	Chhattisgarh
Dhuandhar Falls	Narmada	Madhya Pradesh
Shivasamudram Falls	Cauvery	Karnataka
Dudhsagar Falls	—	Goa [NDA tested via CDS]
Barkana Falls	—	Karnataka [NDA tested via CDS]
Duduma Falls	—	Odisha [NDA tested via CDS]
Kiliyur Falls	—	Tamil Nadu [NDA tested via CDS]

Sharavati River creates Jog Falls — TRUE. [NDA 2022-II]

Brahmani River is formed by confluence of Kosi and Sankh rivers — TRUE. [NDA 2022-II]

Tamraparni is a river of Tirunelveli district, Tamil Nadu — TRUE. [NDA 2022-II]

All three statements — two are correct and one needs to be verified. The NDA PYQ answer says (b) 2 of the above are correct. The Tamraparni statement is correct; the Brahmani statement is correct; Sharavati-Jog Falls is correct. The answer (b) 2 in the PYQ suggests one statement is disputed.