🌊 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:

  1. The Himalayan Rivers
  2. 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:

  1. It is usually deep, narrow, and tidal (affected by sea tides).
  2. Formed where the river flows quickly into the sea — not enough time for silt to settle.
  3. No delta formation occurs.
  4. 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

 

 

**********

 

 

 

📘 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:
2️⃣ Peninsular Rivers. 1️⃣ Himalayan 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.

 

********