This MCQ module is based on: Chapter 3 Summary, Map Work & Exercises
TOPIC 8 OF 17
Chapter 3 Summary, Map Work & Exercises
🎓 Class 11
Social Science
CBSE
Theory
Ch 3 — Drainage System
⏱ ~18 min
🌐 Language: [gtranslate]
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Chapter 3 · Drainage System — Summary, Key Terms & Exercises
Bring it all together. This part of the chapter is built for revision and assessment — a tight summary of every section you have studied, a glossary of the must-know terms, the official NCERT exercises with model answers, plus project work and map work to take learning from the page to the field.
3.13 Chapter Summary — In One Long Breath
The flow of water through well-defined channels is called drainage; the network of those channels is a drainage system. The whole area drained by a river along with its tributaries is a drainage basin; the boundary between two basins is a watershed. India's drainage can be classified by (i) which sea it discharges into — about 77% to the Bay of Bengal, 23% to the Arabian Sea — separated by the Delhi Ridge, Aravalis and Sahyadris; (ii) by basin size — major (>20,000 sq km), medium (2,000–20,000 sq km) and minor (<2,000 sq km); and (iii) by mode of origin — Himalayan and Peninsular drainage.
Four classic drainage patterns appear on Indian topo sheets — dendritic (branches like a tree, e.g. rivers of the Northern Plain), radial (outward from a central hill, e.g. rivers from the Amarkantak range), trellis (parallel primary tributaries with right-angled secondaries) and centripetal (inward into a lake or depression).
The Himalayan drainage is fed by both monsoon rain and snow-melt, so it is perennial. Geologists believe a single mighty Miocene river — the Indo-Brahma (Shiwalik) — once ran along the entire Himalayan foot before being dismembered by the Pleistocene uplift of the Potwar Plateau and the Malda gap into three children: the Indus, the Ganga and the Brahmaputra. The Indus rises near Bokhar Chu (4,164 m), is 2,880 km long, and receives the Panjnad — Satluj, Beas, Ravi, Chenab, Jhelum. The Ganga rises at Gaumukh (Gangotri, 3,900 m), is 2,525 km long, drains 8.6 lakh sq km in India alone, has the Yamuna as its longest tributary and the Kosi as its most volatile (the 'Sorrow of Bihar'). The Brahmaputra rises in the Chemayungdung glacier near Mansarovar, runs 1,200 km across Tibet as the Tsangpo, carves a deep gorge near Namcha Barwa, enters India as the Siang, picks up the Dibang and Lohit, and finally pours into the Bay of Bengal as the Padma.
The Peninsular drainage is older, mature and graded. Three geological events shaped it — subsidence of the western flank, Himalayan upheaval (which opened the Narmada and Tapi rifts) and a slight north-west to south-east tilt that sent most rivers eastward. The major east-flowing rivers are the Mahanadi (851 km), Godavari (1,465 km — Dakshin Ganga), Krishna (1,401 km) and Kaveri (800 km); the major west-flowing exceptions are the Narmada (1,312 km, Sardar Sarovar) and the Tapi (724 km), both flowing in rift valleys and forming estuaries rather than deltas. The Luni drains the desert of western Rajasthan, but is entirely ephemeral.
The two systems contrast sharply in regime: Himalayan rivers are perennial, with V-valleys, gorges, meandering plains-courses, and large deltas; Peninsular rivers are mostly seasonal, with broad valleys, fixed courses, modest sediment loads, and (except Narmada and Tapi) deltas at the Bay of Bengal mouth. India's water is unevenly distributed in time and space; floods and droughts often coexist. Inter-basin transfer projects (Periyar Diversion, Indira Gandhi Canal, Beas–Satluj Link, the proposed Ganga–Kaveri link) try to even this out, but face huge engineering and ecological challenges. Rivers are also threatened by pollution from sewage, effluent, cremation, immersion of statues and bathing — addressed by missions like the Ganga Action Plan and Namami Gange.
3.14 Key Terms — Glossary
Drainage
Flow of water through well-defined channels.
Drainage System
The network of channels through which water flows.
Drainage Pattern
The geometric arrangement of channels — dendritic, trellis, radial, centripetal.
Catchment Area
The land area from which a river collects its water.
Drainage Basin
Whole area drained by a river plus all its tributaries.
Watershed
Boundary line between two adjacent drainage basins; small catchments are also called watersheds.
Dendritic
Tree-like branching pattern — e.g. rivers of the Northern Plain.
Trellis
Grid-like; primary tributaries parallel, secondary tributaries at right angles.
Radial
Streams flow outward from a central hill — e.g. Amarkantak.
Centripetal
Streams flow inward into a basin or lake.
Antecedent River
A river that pre-dates the mountain it now cuts through, e.g. Satluj, Subansiri.
Perennial River
Carries water throughout the year — e.g. Ganga, Brahmaputra.
Ephemeral River
Flows only during the rains — e.g. Luni.
Regime
Pattern of variation in river discharge through the year.
Riparian
Anything connected with a river bank or basin; 'riparian state'.
Thalweg
Line of lowest elevation along the river channel — the deep current line.
Rift Valley
Linear valley formed by subsidence between parallel faults — Narmada, Tapi.
Estuary
Wide, tidal river-mouth without delta deposits — e.g. Narmada (27 km).
Delta
Triangular sediment deposit at a river mouth — e.g. Mahanadi, Krishna, Godavari.
Panjnad
The five rivers of Punjab — Satluj, Beas, Ravi, Chenab, Jhelum.
3.15 NCERT Exercises — MCQs
Choose the right answer from the four alternatives given below. Click "Show Answer" after you have made your choice.
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Multiple-Choice Questions (NCERT Q.1)
(i) Which one of the following rivers was known as the 'Sorrow of Bengal'?
L1 RememberAnswer: (d) The Damodar. It earned the nickname 'Sorrow of Bengal' because of its repeated devastating floods through the eastern margins of the Chotanagpur Plateau, before being tamed by the multipurpose Damodar Valley Corporation. (The Kosi, by contrast, is the 'Sorrow of Bihar'.)
(ii) Which one of the following rivers has the largest river basin in India?
L1 RememberAnswer: (c) The Ganga. The Ganga basin covers about 8.6 lakh sq km in India alone — the largest of any Indian river. The Indus is longer in total, but a much greater portion of its basin lies outside India.
(iii) Which one of the following rivers is not included in 'Panchnad'?
L2 UnderstandAnswer: (c) The Indus. 'Panjnad' (or Panchnad) is the joint name for the five tributaries of the Indus — Satluj, Beas, Ravi, Chenab and Jhelum. The Indus itself is the master stream that receives the Panjnad just above Mithankot.
(iv) Which one of the following rivers flows in a rift valley?
L2 UnderstandAnswer: (b) The Narmada. The Narmada flows westward in a trough fault between the Satpura range to the south and the Vindhyan range to the north — the textbook Indian rift-valley river. The Tapi shares this distinction.
(v) Which one of the following is the place of confluence of the Alaknanda and the Bhagirathi?
L1 RememberAnswer: (d) Deva Prayag. The Bhagirathi (from Gaumukh) meets the Alaknanda (from Satopanth) at Devprayag — and from this confluence onward the river is called the Ganga. (Vishnu Prayag is where the Dhauli meets the Vishnu Ganga; Rudra Prayag is where Mandakini joins; Karan Prayag is where Pindar joins.)
3.16 NCERT Exercises — Differences (Q.2)
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State the Differences Between the Following
(i) River Basin and Watershed
L2 UnderstandModel Answer: A river basin is the entire area drained by a major river along with all its tributaries — large in size, often spanning several states. A watershed, on the other hand, refers to the catchment of small rivulets and rills, and also to the line that separates one basin from another. Both share unity (what happens in one part affects the others), but basins cover larger areas while watersheds are small.
(ii) Dendritic and Trellis Drainage Patterns
L2 UnderstandModel Answer: A dendritic drainage pattern resembles the branches of a tree — it forms where rocks are uniform and the slope is gentle, e.g. rivers of the Northern Plain. A trellis pattern looks like a garden trellis — primary tributaries flow parallel to each other while secondary tributaries join them at right angles, typical of a folded-and-faulted ridge-and-valley terrain.
(iii) Radial and Centripetal Drainage Patterns
L2 UnderstandModel Answer: In a radial pattern, rivers originate on a central hill or dome and flow outward in all directions — for example, the rivers rising from the Amarkantak range. In a centripetal pattern, rivers from all directions flow inward and discharge into a central lake or depression. Radial = outward from a hill; centripetal = inward into a basin.
(iv) Delta and Estuary
L3 ApplyModel Answer: A delta is a triangular deposit of sediment built where a river enters a calm sea — for example, the deltas of the Ganga–Brahmaputra (Sundarbans), Mahanadi, Godavari, Krishna and Kaveri at the Bay of Bengal. An estuary is a broad, funnel-shaped, tidal river-mouth where the river fails to build a delta — for example, the 27 km Narmada estuary and the Tapi estuary on the Arabian Sea, where strong tides and rift-valley sediment-trapping prevent delta formation.
3.17 Short Answer Questions (Q.3 — about 30 words)
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Answer in About 30 Words
(i) What are the socio-economic advantages of inter-linking of rivers in India?
L4 AnalyseModel Answer (~30 words): Inter-linking transfers surplus monsoon water from flood-prone basins to drought-hit basins, expands irrigated agriculture, enables hydropower generation and inland navigation, supplies drinking water to dry regions, and helps reduce both floods and droughts simultaneously.
(ii) Write three characteristics of the Peninsular river.
L2 UnderstandModel Answer: (1) Peninsular rivers are older than Himalayan rivers and have broad, graded, mature valleys. (2) Their courses are fixed, with very few meanders and almost no shifting. (3) They are mainly rain-fed and therefore seasonal, with the Narmada and Tapi flowing in rift valleys as westward exceptions.
3.18 Long Answer Questions (Q.4 — about 125 words)
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Answer in Not More than 125 Words
(i) What are the important characteristic features of north Indian rivers? How are these different from Peninsular rivers?
L5 EvaluateModel Answer (~125 words): North Indian (Himalayan) rivers like the Indus, Ganga and Brahmaputra are perennial — fed by both monsoon rain and glacial melt, they carry water all year. Within the mountains they cut deep gorges and V-shaped valleys; on the plains they meander, build flood plains, ox-bow lakes, braided channels and large deltas. Course-shifting is common (Kosi, Brahmaputra). Their sediment loads are very high.
Peninsular rivers (Mahanadi, Godavari, Krishna, Kaveri, Narmada, Tapi) are older, mature, with shallow graded valleys. They flow over a rigid Archaean shield, follow fixed courses with few meanders, and depend mostly on monsoon rainfall — so they are largely seasonal (the Kaveri being an exception, fed by both monsoons). The Narmada and Tapi flow westward in rift valleys, forming estuaries instead of deltas.
Peninsular rivers (Mahanadi, Godavari, Krishna, Kaveri, Narmada, Tapi) are older, mature, with shallow graded valleys. They flow over a rigid Archaean shield, follow fixed courses with few meanders, and depend mostly on monsoon rainfall — so they are largely seasonal (the Kaveri being an exception, fed by both monsoons). The Narmada and Tapi flow westward in rift valleys, forming estuaries instead of deltas.
(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.
L3 ApplyModel Answer (~120 words): Travelling east from Haridwar to Siliguri along the Himalayan foothills, you cross (in order): the Ganga at Haridwar, the Ramganga, the Yamuna (further south), then the Sarda, the Ghaghara, the Gandak, the Kosi, the Mahananda and finally the Tista. Take the Kosi as an example. It rises north of Mount Everest in Tibet (its main stream is the Arun), is an antecedent river, crosses the Central Himalayas and forms Sapt Kosi after uniting with the Son Kosi and Tamur Kosi. On the Bihar plains it carries enormous sediment loads, blocks its own channel, and shifts course frequently — earning the title 'Sorrow of Bihar'. The Sapt Kosi finally joins the Ganga.
3.19 Map Work — Test Yourself
MAP WORK — Mark on an Outline Map of India
Bloom: L3 Apply
On a blank political map of India:
- Mark and label the Indus with at least three of its tributaries (Satluj, Beas, Ravi, Chenab, Jhelum).
- Mark and label the Ganga, with the Yamuna, Chambal, Ghaghara, Gandak and Kosi.
- Mark and label the Brahmaputra, with the Subansiri, Kameng, Manas and Lohit.
- Mark the four major east-flowing Peninsular rivers — Mahanadi, Godavari, Krishna, Kaveri — with their sources.
- Mark the two west-flowing rifts — Narmada and Tapi.
- Shade the area drained by the Luni system in western Rajasthan.
- Mark Devprayag, Allahabad (Prayag), Patna, Polavaram, Bharuch and Mahabaleshwar.
✅ Tips
Use blue arrows to show the direction of flow. Use a thick line for the master stream and thinner lines for tributaries. Always write the source location alongside the source point. Remember — the Indus and the Brahmaputra both rise close to Mansarovar in Tibet, but flow off in opposite directions.
3.20 Project Work
PROJECT — A Day in the Life of a River
Bloom: L6 Create
Pick any one Indian river — Himalayan or Peninsular. Over four weeks, build a project file with the following sections:
- Source & Course (week 1): Map the river from source to mouth using an outline map of India. Mark all major tributaries.
- Cultural & Economic Profile (week 2): Collect three news clippings, one folk-story or hymn, and a list of major cities along its banks.
- Hazard & Management (week 3): Document floods, droughts or pollution events from the last 10 years and the response (dams, treatment plants, programmes like Namami Gange / Namami Devi Narmade).
- Your Recommendation (week 4): Write a 200-word policy note proposing one specific action you would take if you were the river's regional planner. Justify it using basin-unity arguments.
✅ Sample Approach — Narmada
Trace the Narmada from Amarkantak (1,057 m) to its 27 km estuary south of Bharuch. Record the Sardar Sarovar Project's irrigation/hydropower benefits along with displacement issues. Note pilgrimage tradition and the Namami Devi Narmade conservation mission. End with a recommendation — e.g. catchment afforestation upstream + sustainable sand-mining controls midstream.
DEBATE PROMPT — Linking Rivers
Bloom: L5 Evaluate
Hold a class debate on:
- "Resolved: India should aggressively pursue inter-basin river-linking to address flood–drought asymmetry."
- Each side prepares a 5-point statement plus rebuttal pointers.
- Conclude with a class vote — and write a 150-word reflection on which side you found more convincing and why.
✅ Debate Hooks
Pro: existing successes — Indira Gandhi Canal (Rajasthan), Periyar Diversion (Tamil Nadu), Beas–Satluj Link (Punjab/Haryana). Con: lifting cost across the Vindhya–Satpura divide; loss of sediment supply to coastal deltas like the Sundarbans; displacement of communities; ecological disruption to fish migration.
3.21 Self-Test — Quick Recall
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Quick Recall (CBQ Style)
Case Study: The District Magistrate of a Bihar district has been asked to file a 'River Resilience Report' covering both the Kosi (north) and the Son (south) tributaries of the Ganga that pass through the district. She must explain why the two rivers behave so differently despite being neighbours — and what unique problems each poses for the people of her district.
Q1. The Kosi rises north of Mount Everest, the Son rises on the Amarkantak plateau. To which two drainage systems do they respectively belong?
L1 RememberAnswer: (C) — The Kosi is a left-bank Himalayan tributary of the Ganga (its main stream Arun rises in Tibet); the Son rises in the Amarkantak plateau and is the largest right-bank Peninsular tributary of the Ganga.
Q2. Why does the Kosi shift its course frequently while the Son does not?
L4 AnalyseModel Answer: The Kosi rises in a rapidly rising young mountain belt and brings massive sediment from its upper reaches. When this sediment is dumped on the Bihar plains, it blocks the channel, forcing the river to break out and shift sideways. The Son, by contrast, flows over a rigid Peninsular shield with hard rocks and modest sediment, so it stays within a fixed channel.
Q3. List two characteristics that define a river's regime.
L2 UnderstandModel Answer: A regime is described by (i) the seasonal pattern of discharge — when the river's flow peaks and when it bottoms out; and (ii) the source(s) of water — whether the river is fed only by rain (single peak) or also by snow-melt (twin peak). Climate, basin geology and rock type also affect the regime.
HOT Q. Design a 'River Health Index' for any one Indian river using five indicators (e.g., perennial flow, sediment load, pollution level, biodiversity, basin governance). Score one Himalayan river and one Peninsular river out of 5 on each indicator, and explain how the differences flow from the geological character of the basin.
L6 CreateHint: Pick (say) Ganga vs Krishna. Ganga scores high on perennial flow (snow-melt + monsoon) and biodiversity but low on pollution. Krishna scores low on perennial flow (mostly rain-fed) but mid-high on basin governance (well-defined tribunal). Tie each score back to the contrast between a young, snow-fed Himalayan basin and an old, rain-fed Peninsular basin.
3.22 Drainage at a Glance — Comparative Visual
Figure 3.5: Length comparison (km) of India's nine landmark rivers — three Himalayan giants (Indus, Ganga, Brahmaputra-Tibet stretch) plus six Peninsular rivers. Note how the Ganga's length is shared by Uttarakhand (110 km), UP (1,450 km), Bihar (445 km) and West Bengal (520 km).
⚖️ Final Assertion–Reason — Whole-Chapter Check
Options:
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is NOT the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
(A) Both A and R are true, and R is the correct explanation of A.
(B) Both A and R are true, but R is NOT the correct explanation of A.
(C) A is true, but R is false.
(D) A is false, but R is true.
Assertion (A): About 77% of India's drainage area discharges into the Bay of Bengal.
Reason (R): The Delhi Ridge, the Aravalis and the Sahyadris together act as the major water-divide separating the Bay of Bengal drainage from the Arabian Sea drainage.
Answer: (A) — Both A and R are true, and R is the correct explanation. Most of the country lies on the eastern side of this divide, so 77% of the drainage area runs to the Bay of Bengal, while only 23% (Indus, Narmada, Tapi, Mahi, Periyar) reaches the Arabian Sea.
Assertion (A): A river basin is the most appropriate unit for micro, meso and macro planning regions.
Reason (R): A river basin is bound by physical unity — what happens in one part directly affects every other part of the basin.
Answer: (A) — Both A and R are true, and R is the correct explanation. Because basins are bound by unity, planning at the basin scale internalises upstream–downstream effects (silt, water sharing, pollution) far better than political-boundary planning.
Assertion (A): The Kaveri carries water year-round with much less fluctuation than other Peninsular rivers.
Reason (R): Its upper catchment is fed by the south-west monsoon in summer and its lower catchment by the north-east monsoon in winter.
Answer: (A) — Both A and R are true, and R is the correct explanation. The two staggered monsoons keep the Kaveri replenished throughout the year, smoothing its discharge curve in a way no other Peninsular river enjoys.
🌍 What You Should Now Be Able to Do
After working through this chapter you should be able to: (1) define drainage, basin and watershed; (2) identify the four classic drainage patterns on a topo sheet; (3) recall the source, length and main tributaries of the Indus, Ganga and Brahmaputra; (4) profile the Mahanadi, Godavari, Krishna, Kaveri, Narmada and Tapi; (5) contrast Himalayan and Peninsular regimes; and (6) argue both sides of the river-linking debate using basin-unity logic.
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