Class | Subject | Book | Chapter | Session | Questions covered |
|---|---|---|---|---|---|
XI | Geography | India: Physical Environment (NCERT) | 3 – Drainage System | 2026-27 | 13 of 13 |
Chapter at a glance
Topic | Key points |
|---|---|
Drainage patterns | Dendritic, trellis, rectangular, radial, centripetal |
Drainage basin and watershed | Area drained by a river and its tributaries; small basins are watersheds; divides separate basins |
Himalayan rivers | Indus, Ganga, Brahmaputra systems; perennial (snow + rain), antecedent, gorges, meanders, deltas |
Peninsular rivers | Mahanadi, Godavari, Krishna, Kaveri (east, deltas); Narmada, Tapi (west, rift valleys, estuaries); seasonal, older, graded |
River regime | Seasonal pattern of flow |
Issues | Floods, pollution, inter-state disputes, inter-linking of rivers |
Exercise Questions
Question 1 (i)
Which one of the following rivers was known as the ‘Sorrow of Bengal’?
(a) The Gandak (b) The Son (c) The Kosi (d) The Damodar
Answer
The Damodar was notorious for devastating floods in West Bengal; it has been tamed by the Damodar Valley Corporation.
- The Damodar
Question 1 (ii)
Which one of the following rivers has the largest river basin in India?
(a) The Indus (b) The Brahmaputra (c) The Ganga (d) The Krishna
Answer
- The Ganga
Question 1 (iii)
Which one of the following rivers is not included in ‘Panchnad’?
(a) The Ravi (b) The Chenab (c) The Indus (d) The Jhelum
Answer
Panchnad refers to the five rivers of Punjab — Satluj, Beas, Ravi, Chenab and Jhelum — which join the Indus.
- The Indus
Question 1 (iv)
Which one of the following rivers flows in a rift valley?
(a) The Son (b) The Yamuna (c) The Narmada (d) The Luni
Answer
- The Narmada
Question 1 (v)
Which one of the following is the place of confluence of the Alaknanda and the Bhagirathi?
(a) Vishnu Prayag (b) Rudra Prayag (c) Karan Prayag (d) Deva Prayag
Answer
Below Deva Prayag the combined stream is called the Ganga.
- Deva Prayag
Question 2 (i)
State the differences between River Basin and Watershed.
Answer
River basin | Watershed |
|---|---|
Area drained by a large river and all its tributaries | Area drained by a small river or stream |
Very large in size (e.g. Ganga basin) | Small in size |
Includes many watersheds | Is a part of a river basin |
A river basin is the large area drained by a major river and its tributaries; a watershed is the small area drained by a minor stream, forming part of a basin.
Question 2 (ii)
State the differences between Dendritic and Trellis drainage pattern.
Answer
Dendritic | Trellis |
|---|---|
Resembles the branches of a tree | Primary tributaries flow parallel to each other and secondary tributaries join them at right angles |
Develops on uniform rock with a general slope | Develops where hard and soft rocks lie parallel (folded topography) |
Example: rivers of the northern plains | Example: rivers in the upper Himalayan region / Singhbhum |
Dendritic is tree-like on uniform rocks; trellis has parallel main streams joined at right angles, on alternating hard and soft rock bands.
Question 2 (iii)
State the differences between Radial and Centripetal drainage pattern.
Answer
Radial | Centripetal |
|---|---|
Rivers originate from a hill and flow outward in all directions | Rivers flow inward from all directions into a lake or depression |
Example: rivers from the Amarkantak range | Example: streams draining into Loktak lake (Manipur) |
Radial streams flow outward from a central height (Amarkantak); centripetal streams flow inward into a depression (Loktak lake).
Question 2 (iv)
State the differences between Delta and Estuary.
Answer
Delta | Estuary |
|---|---|
A triangular landform formed by deposition of sediments at the mouth of a river | A funnel-shaped mouth where the river enters the sea without forming a delta |
River slows down and splits into distributaries | Strong tides and currents carry the sediment away; no distributaries |
Very fertile land | Good for natural harbours |
Example: Ganga, Mahanadi, Godavari, Krishna, Kaveri | Example: Narmada, Tapi |
A delta is a depositional, triangular landform with distributaries (Ganga); an estuary is a funnel-shaped tidal mouth without deposition (Narmada, Tapi).
Question 3 (i)
What are the socio-economic advantages of inter-linking of rivers in India?
Answer
Interlinking can transfer surplus water from flood-prone basins (e.g. Ganga–Brahmaputra) to water-deficit regions (e.g. peninsular and western India). Advantages:
- Flood control in the surplus basins and drought relief in deficit areas.
- More irrigation, raising agricultural production.
- Drinking water supply to dry regions.
- Hydroelectric power generation.
- Inland navigation and fisheries; employment.
It can reduce floods and droughts, expand irrigation and drinking water, generate hydropower, and aid navigation and jobs.
Question 3 (ii)
Write three characteristics of the Peninsular river.
Answer
- They are seasonal, fed mainly by monsoon rain; flow is reduced in the dry season.
- They are older rivers with graded profiles, broad and shallow valleys, flowing through hard rocks; they do not meander much.
- Most flow east into the Bay of Bengal forming deltas; the Narmada and Tapi flow west through rift valleys forming estuaries.
(Also: smaller catchment areas than Himalayan rivers.)
Seasonal and rain-fed; old with graded, shallow valleys; mostly east-flowing with deltas (Narmada and Tapi west-flowing in rift valleys with estuaries).
Question 4 (i)
What are the important characteristic features of north Indian rivers? How are these different from Peninsular rivers?
Answer
Features of north Indian (Himalayan) rivers
- Perennial: fed by both melting snow/glaciers and rainfall.
- Antecedent rivers that cut deep gorges through the Himalayas.
- Long courses and large basins.
- In the plains, they meander, shift courses and form oxbow lakes, floodplains and huge deltas.
- Carry heavy loads of silt; prone to floods.
- Useful for irrigation and navigation.
Differences
Basis | Himalayan rivers | Peninsular rivers |
|---|---|---|
Source | Himalayan glaciers | Peninsular plateau and Western Ghats |
Nature of flow | Perennial (snow + rain) | Seasonal (rain-fed) |
Type | Antecedent, youthful | Consequent, mature/old |
Valleys | Deep gorges, V-shaped valleys | Broad, shallow valleys |
Course | Meandering, shifting | Graded, fixed courses |
Basin size | Very large | Small to medium |
Mouth | Large deltas | Deltas (east) / estuaries (west) |
Himalayan rivers are perennial, antecedent, form gorges and meander in plains with large basins and deltas; Peninsular rivers are seasonal, older, with graded shallow valleys, fixed courses and smaller basins.
Question 4 (ii)
Suppose you are travelling from Haridwar to Siliguri along the foothills of the Himalayas. Name the important rivers you will come across. Describe the characteristics of any one of them.
Answer
Rivers crossed (west to east): Ganga (at Haridwar), Ramganga, Sharda/Kali, Ghaghara, Gandak, Burhi Gandak, Bagmati, Kosi, Mahananda and, near Siliguri, the Tista.
The Kosi
- An antecedent river rising north of Mount Everest in Tibet; its main stream is the Arun, joined by the Son Kosi and Tamur Kosi in Nepal to form the Sapta Kosi.
- It carries a huge load of sediment.
- It frequently changes its course and causes devastating floods in north Bihar, which is why it is called the “Sorrow of Bihar”.
- It joins the Ganga in Bihar.
Ganga, Ramganga, Sharda, Ghaghara, Gandak, Bagmati, Kosi, Mahananda and Tista. The Kosi is an antecedent, silt-laden river that frequently shifts course and floods north Bihar (“Sorrow of Bihar”).
Topic checklist
- Drainage patterns, basins and watersheds
- Himalayan drainage: Indus, Ganga and Brahmaputra systems
- Peninsular drainage: east- and west-flowing rivers
- Comparison of Himalayan and Peninsular rivers
- River regimes; inter-linking and pollution of rivers