🌊 Chapter 3 – DRAINAGE

🌧️ 1. Meaning of Drainage

The term drainage refers to the river system of an area.
Many small streams join together to form a main river, which finally flows into a sea, lake, or ocean.
The area drained by a river and its tributaries is called a drainage basin.
An upland or high area that separates two drainage basins is called a water divide.
👉 Example: The Ambala region separates the Indus and Ganga basins.

🗺️ 2. Drainage Systems of India

India’s drainage system is controlled by the physical features of the land.
There are two main groups of rivers:

The Himalayan Rivers
The Peninsular Rivers

🏔️ 3. The Himalayan Rivers

These rivers are perennial, meaning they have water throughout the year.
They are fed by rainfall and melting snow.
They flow through deep gorges, create meanders, oxbow lakes, and form large deltas at their mouths.
The three main Himalayan river systems are:
1. The Indus River System
2. The Ganga River System
3. The Brahmaputra River System

🌍 (a) The Indus River System

Origin: Tibet, near Lake Mansarovar.
Enters India through Ladakh.
Major tributaries: Zaskar, Nubra, Shyok, Hunza, Jhelum, Chenab, Ravi, Beas, Satluj.
Flows through Pakistan and drains into the Arabian Sea near Karachi.
Total length: ~2900 km, one of the longest rivers in the world.
Indus Water Treaty (1960): India can use 20% of its water for irrigation in Punjab, Haryana, and Rajasthan.

🕉️ (b) The Ganga River System

Origin: Gangotri Glacier (Bhagirathi) in Uttarakhand.
Bhagirathi and Alaknanda meet at Devaprayag to form the Ganga.
Major Himalayan tributaries: Yamuna, Ghaghara, Gandak, Kosi.
- Yamuna: rises from Yamunotri Glacier, joins Ganga at Prayagraj (Allahabad).
- Ghaghara, Gandak, Kosi: rise in Nepal Himalayas; cause floods but enrich the soil.
Peninsular tributaries: Chambal, Betwa, Son.
At Farakka (West Bengal), Ganga divides:
- Bhagirathi-Hooghly (flows through West Bengal)
- Main stream flows into Bangladesh, joins the Brahmaputra, forming the Meghna and Sundarban Delta.
Sundarban Delta: Largest and fastest-growing delta; home of the Royal Bengal Tiger.

🌧️ (c) The Brahmaputra River System

Origin: Tibet, east of Mansarovar (called Tsang Po there).
Enters India (Arunachal Pradesh) as Dihang, joined by Dibang and Lohit, forming the Brahmaputra in Assam.
Enters Bangladesh as Jamuna.
Carries less water and silt in Tibet (dry, cold area) but more in India (wet region).
Has a braided channel and forms riverine islands like Majuli (world’s largest river island).
Causes floods every year due to heavy rainfall and silt deposits.

🪨 4. The Peninsular Rivers

Mostly seasonal (depend on rainfall).
Shorter and shallower than Himalayan rivers.
Flow mainly eastwards into the Bay of Bengal, forming deltas.
Some rivers flow westwards into the Arabian Sea, forming estuaries.
The Western Ghats act as the main water divide.

🌅 What is an Estuary?

An estuary is the wide mouth of a river where it meets the sea or ocean, but does not form a delta.
Instead of depositing silt, the river’s strong flow mixes directly with seawater, creating a deep and narrow channel.

🌊 Key Features of an Estuary:

It is usually deep, narrow, and tidal (affected by sea tides).
Formed where the river flows quickly into the sea — not enough time for silt to settle.
No delta formation occurs.
Found mostly along India’s western coast, where land slopes steeply.

🗺️ Examples of Estuaries in India:

Narmada River (flows into Arabian Sea)
Tapi River (flows into Arabian Sea)
Mahi River (flows into Arabian Sea)
Mandovi and Zuari Rivers (Goa)

🌿 Difference between Delta and Estuary:

Feature	Delta	Estuary
Formation	By deposition of silt	By erosion and strong tides
Shape	Triangular / fan-shaped	Funnel-shaped
Sediment	High (lots of deposits)	Very little or no deposits
Example	Ganga, Godavari	Narmada, Tapi

🏞️ (a) The Narmada Basin

Origin: Amarkantak Hills (Madhya Pradesh).
Flows westward through a rift valley into the Arabian Sea.
Famous spots: Marble Rocks (Jabalpur), Dhuandhar Falls.
Important states: Madhya Pradesh and Gujarat.
Namami Devi Narmade project focuses on its conservation.

🏞️ (b) The Tapi Basin

Origin: Satpura Ranges (Betul district, MP).
Flows parallel to Narmada, also in a rift valley.
Passes through Madhya Pradesh, Maharashtra, and Gujarat.

🌊 (c) The Godavari Basin

Origin: Nasik district, Maharashtra.
Longest Peninsular river (about 1500 km).
Tributaries: Purna, Wardha, Pranhita, Manjra, Wainganga, Penganga.
Flows into the Bay of Bengal.
Known as Dakshin Ganga (Southern Ganga).

🏝️ (d) The Mahanadi Basin

Origin: Highlands of Chhattisgarh.
Flows through Odisha into the Bay of Bengal.
Basin shared by Maharashtra, Chhattisgarh, Jharkhand, and Odisha.

💧 (e) The Krishna Basin

Origin: Mahabaleshwar (Maharashtra).
Flows ~1400 km to the Bay of Bengal.
Tributaries: Tungabhadra, Koyana, Bhima, Musi, Ghatprabha.
Basin shared by Maharashtra, Karnataka, and Andhra Pradesh.

🌴 (f) The Kaveri Basin

Origin: Brahmagiri Range (Western Ghats).
Flows through Karnataka and Tamil Nadu, drains into Bay of Bengal.
Tributaries: Amravati, Bhavani, Hemavati, Kabini.
Known for Shivasamudram Falls, a major source of hydropower.

🌅 (g) Smaller East-Flowing Rivers

Damodar, Brahmani, Baitarani, Subarnarekha—flow into Bay of Bengal.
West-flowing rivers: Sabarmati, Mahi, Bharathpuzha, Periyar—flow into Arabian Sea.

🏞️ 5. Lakes

India has many natural and artificial lakes.
Natural lakes are formed by glaciers, tectonic movements, or river actions.
Artificial lakes are created by damming rivers.

Types and Examples:

Type	Example
Glacial Lake	Dal, Nainital, Bhimtal, Barapani
Tectonic Lake	Wular (largest freshwater lake in India)
Lagoon (coastal lake)	Chilika, Pulicat, Kolleru
Saltwater Lake	Sambhar (Rajasthan)
Artificial (man-made)	Gobind Sagar (Bhakra Nangal Dam), Hirakud, Nagarjuna Sagar, Rana Pratap Sagar

Importance of Lakes:

Store and regulate river flow
Prevent floods, provide water during dry season
Generate hydel power
Support aquatic life and tourism (Dal, Nainital)
Help maintain local climate

🏞️ 6. Role of Rivers in the Economy

Provide water for irrigation, drinking, and industries.
Support navigation and transport.
Used for hydropower generation.
Encourage settlements, trade, and agriculture.
Many cities (Delhi, Kolkata, Varanasi) are on riverbanks.

☣️ 7. River Pollution

Industrial waste, sewage, and agricultural chemicals pollute rivers.
This reduces water quality and harms aquatic life.
Rivers lose their self-cleaning ability due to overuse.

River Conservation Programmes:

Ganga Action Plan (1985) → launched to clean the Ganga.
Later expanded into the National River Conservation Plan (NRCP, 1995) to clean all major rivers.

🧠 8. Concept Summary

Concept	Key Points
Drainage Basin	Area drained by a river system
Water Divide	Upland separating two drainage basins
Himalayan Rivers	Perennial, long, erosional, delta-forming
Peninsular Rivers	Seasonal, short, form estuaries or small deltas
Lakes	Regulate water, prevent floods, generate power
Rivers’ Importance	Irrigation, hydropower, transport, economy
River Pollution	Caused by waste, sewage, chemicals
Conservation Plans	GAP and NRCP to clean rivers

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📘 Chapter 3 – Drainage (Page-wise Q&A)

📖 Page 17

Q 1. What does the term drainage mean?
A 1. Drainage means the river system of an area—how streams and rivers flow together and finally empty into a sea, lake, or ocean.

Q 2. What is a drainage basin?
A 2. The area drained by a single river and its tributaries is called a drainage basin.

Q 3. What is a water divide? Give one example.
A 3. An elevated area separating two drainage basins is a water divide.
👉 Example – Ambala divides the Indus and Ganga basins.

Q 4. Which river has the largest drainage basin in India?
A 4. The Ganga River has the largest drainage basin in India.

📖 Page 18–19

Q 1. How are Indian rivers classified?
A 1. They are divided into two groups:
1️⃣ Himalayan Rivers 2️⃣ Peninsular Rivers.

Q 2. How are Himalayan rivers different from Peninsular rivers?

Himalayan Rivers	Peninsular Rivers
Perennial (flow all year)	Mostly seasonal
Long and deep-coursed	Short and shallow
Form meanders and deltas	Form smaller deltas or estuaries
Fed by rain + snow	Fed mainly by rain

Q 3. What are the three major Himalayan river systems?
A 3. Indus, Ganga, and Brahmaputra.

Q 4. Name the major tributaries of the Indus.
A 4. Jhelum, Chenab, Ravi, Beas and Satluj.

Q 5. According to the Indus Water Treaty (1960), how much of Indus water can India use?
A 5. India can use 20 per cent of the total Indus system water—for irrigation in Punjab, Haryana and Rajasthan.

📖 Page 20

Q 1. Name the headstreams of the Ganga. Where do they meet?
A 1. Bhagirathi (from Gangotri Glacier) and Alaknanda meet at Devaprayag (Uttarakhand) to form the Ganga.

Q 2. List the important Himalayan tributaries of the Ganga.
A 2. Yamuna, Ghaghara, Gandak and Kosi.

Q 3. Which tributaries join the Ganga from the Peninsular uplands?
A 3. Chambal, Betwa and Son.

Q 4. Where does the Ganga form a delta?
A 4. At its mouth in West Bengal and Bangladesh —the Sundarban Delta.

📖 Page 21

Q 1. Why is the Brahmaputra called Tsang Po in Tibet and Jamuna in Bangladesh?
A 1. Because it flows through these regions under local names—Tsang Po in Tibet, Brahmaputra in India, Jamuna in Bangladesh.

Q 2. Why does the Brahmaputra carry less silt in Tibet?
A 2. Tibet is a cold, dry region; less rainfall → less erosion → less silt.

Q 3. What makes Brahmaputra floods common in Assam?
A 3. Heavy rainfall + huge silt deposits raise the riverbed and make it overflow each year.

📖 Page 21–22

Q 1. Name the main water divide of Peninsular India.
A 1. The Western Ghats.

Q 2. Which are the only long west-flowing rivers?
A 2. Narmada and Tapi.

Q 3. Where does the Narmada rise? Name two famous places on it.
A 3. Origin – Amarkantak Hills (Madhya Pradesh).
Famous spots – Marble Rocks and Dhuandhar Falls at Jabalpur.

Q 4. Where does the Tapi rise and where does it drain?
A 4. Rises in Satpura Ranges (Betul district, MP); drains into the Arabian Sea.

📖 Page 22

Q 1. Give details of major east-flowing rivers.

River	Origin	Outflow	States
Godavari	Nasik (Maharashtra)	Bay of Bengal	MH, MP, Odisha, AP
Mahanadi	Highlands of Chhattisgarh	Bay of Bengal	MH, CG, JH, OD
Krishna	Mahabaleshwar (MH)	Bay of Bengal	MH, KA, AP
Kaveri	Brahmagiri Range (WG)	Bay of Bengal	KA, TN, KL

Q 2. Which river is called Dakshin Ganga?
A 2. The Godavari River.

Q 3. Which is the second-largest waterfall in India and on which river?
A 3. Shivasamudram Falls on the Kaveri.

Q 4. Which is the biggest waterfall in India?
A 4. Jog Falls on the Sharavathi River.

📖 Page 22–23

Q 1. What are different types of Indian lakes? Give examples.

Type	Example
Glacial (Freshwater)	Dal, Nainital, Bhimtal, Barapani
Tectonic	Wular (J&K)
Lagoon (Coastal)	Chilika, Pulicat, Kolleru
Saltwater	Sambhar (Rajasthan)
Man-made	Gobind Sagar, Hirakud, Nagarjuna Sagar

Q 2. Why are lakes useful?
A 2. They regulate river flow, prevent floods, store water, generate hydel power, support aquatic life, promote tourism and beautify landscapes.

Activity:
Make a list of natural and artificial lakes (students use atlas).

📖 Page 23

Q 1. Why are rivers important for our economy?
A 1.

Provide water for irrigation and industries
Support navigation & transport
Help generate hydropower
Encourage settlements and trade

Q 2. What causes river pollution?
A 2. Untreated sewage, industrial waste, and agricultural chemicals entering rivers reduce water quality and harm aquatic life.

Q 3. Name two major programmes for cleaning rivers.
A 3.
1️⃣ Ganga Action Plan (GAP, 1985)
2️⃣ National River Conservation Plan (NRCP, 1995)

🧾 EXERCISE – Page 24–25

1. Choose the right answer

Question	Correct Answer
(i) Wular Lake is in —	(d) Jammu and Kashmir
(ii) Source of Narmada —	(c) Amarkantak
(iii) Salt water lake —	(a) Sambhar
(iv) Longest Peninsular river —	(c) Godavari
(v) River flowing through rift valley —	(d) Tapi

2. Answer briefly

(i) Water divide – Elevated area separating two basins; e.g. Ambala.
(ii) Largest river basin – Ganga River Basin.
(iii) Origin of Indus and Ganga – Both in the Himalayas (near Lake Mansarovar and Gangotri Glacier).
(iv) Two headstreams of Ganga – Bhagirathi and Alaknanda meet at Devaprayag.
(v) Brahmaputra in Tibet has less silt because of cold dry climate and little rain.
(vi) Two Peninsular rivers flowing through troughs – Narmada and Tapi.
(vii) Economic benefits – Irrigation, fishing, hydel power, tourism, transport.

3. Group the lakes

Natural Lakes	Artificial / Man-made Lakes
Wular, Dal, Nainital, Bhimtal, Loktak, Barapani, Chilika, Sambhar, Pulicat	Gobind Sagar, Rana Pratap Sagar, Nizam Sagar, Nagarjuna Sagar, Hirakud

4. Difference – Himalayan vs Peninsular Rivers

Himalayan Rivers	Peninsular Rivers
Perennial (flow year-round)	Seasonal (flow in monsoon)
Long and deep valleys	Short and shallow
Form deltas at mouth	Form small deltas/estuaries
Fed by snow + rain	Fed mainly by rain

5. Compare East-flowing and West-flowing Rivers

East-flowing	West-flowing
Flow into Bay of Bengal	Flow into Arabian Sea
Form large deltas	Form estuaries
Longer courses	Short courses
Examples – Mahanadi, Godavari, Krishna, Kaveri	Narmada, Tapi, Mahi, Sabarmati

6. Why are rivers important for India’s economy?

Provide irrigation and drinking water
Enable navigation and trade
Produce hydroelectric power
Support agriculture, industry and fisheries
Maintain ecological balance and recharge groundwater

Map Skills

1️⃣ Mark and label rivers – Ganga, Satluj, Damodar, Krishna, Narmada, Tapi, Mahanadi, Brahmaputra.
2️⃣ Mark and label lakes – Chilika, Sambhar, Wular, Pulicat, Kolleru.

✅ Summary for Revision

Drainage = river system of an area.
Two river groups – Himalayan (perennial) & Peninsular (seasonal).
Major Himalayan rivers – Indus, Ganga, Brahmaputra.
Major Peninsular rivers – Narmada, Tapi, Godavari, Mahanadi, Krishna, Kaveri.
Lakes help in flood control, hydel power and tourism.
Rivers = lifelines of the economy.
Pollution control plans – Ganga Action Plan & NRCP.

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