Drainage System, Class 11 Geography (India: Physical Environment)

What Drainage System is about

Weightage: This chapter is part of Unit II, Physiography, of India: Physical Environment, which carries 13 of the 70 theory marks in the school annual exam together with Structure and Physiography. Map work carries a further 5 marks for each book.Source: CBSE Geography (029) syllabus 2026-27, Class XI course structure

Key concepts

Drainage, catchment, basin and watershed; drainage patterns

NCERT section Drainage System (introduction)

Drainage: flow of water through well-defined channels; the network is a drainage system. Ill-defined or choked channels cause flooding.

Pattern depends on: geological time period, nature and structure of rocks, topography, slope, amount of water and periodicity of flow.

Terms:

• Catchment area: the specific area from which a river collects water.
• Drainage basin: area drained by a river and its tributaries.
• Watershed: the boundary line separating one basin from another; also the term for small catchments of rivulets and rills, while large ones are river basins.
• Basins and watersheds show unity: change in one part affects the whole, so they are ideal micro, meso or macro planning regions.

Patterns:

Pattern	Description	Example
Dendritic	Like the branches of a tree	Rivers of the northern plain
Radial	Rivers rise on a hill and flow in all directions	Rivers from the Amarkantak range
Trellis	Primary tributaries parallel; secondary ones join them at right angles	-
Centripetal	Rivers flow from all directions into a lake or depression	-

Worked example

Rivers such as the Narmada and the Son start from the same highland and flow away in different directions, while streams in a basin drain inward into a lake. Name the two drainage patterns and give the NCERT example of the first. (2 marks)

Try it first, then show the solutionSolution

1. Rivers rising on a hill and flowing out in all directions form a radial pattern; the rivers from the Amarkantak range are the NCERT example.
2. Rivers draining from all sides into a lake or depression form a centripetal pattern.

Answer: Radial (Amarkantak range) and centripetal.

Classification of Indian drainage

NCERT section Drainage Systems of India

1. By discharge (orientation to the sea):

Group	Share of drainage area	Rivers
Bay of Bengal	About 77%	Ganga, Brahmaputra, Mahanadi, Krishna, etc.
Arabian Sea	About 23%	Indus, Narmada, Tapi, Mahi, Periyar

Separated by the Delhi ridge, the Aravalis and the Sahyadris.

2. By size of watershed:

Category	Catchment	Number/examples
Major	> 20,000 sq km	14 basins: Ganga, Brahmaputra, Krishna, Tapi, Narmada, Mahi, Pennar, Sabarmati, Barak, etc.
Medium	2,000-20,000 sq km	44 basins: Kalindi, Periyar, Meghna, etc.
Minor	< 2,000 sq km	Many rivers in low-rainfall areas

3. By mode of origin, nature and characteristics: Himalayan and Peninsular drainage. Its problem: the Chambal, Betwa, Son, etc. (Peninsular in origin and older) belong to the Ganga system; still it is the most accepted basis, and NCERT follows it.

General: Indian drainage results from the evolution of the three physiographic units and the nature of precipitation. Most large Peninsular rivers rise in the Western Ghats and flow into the Bay of Bengal; the Narmada and Tapi are exceptions flowing to the Arabian Sea.

Worked example

Why is the Himalayan-Peninsular classification 'imperfect' even though it is the most accepted? (2 marks)

Try it first, then show the solutionSolution

1. It groups rivers by origin and nature, but the Chambal, Betwa and Son, which rise on the Peninsula and are older, join the Ganga, a Himalayan system.
2. So some rivers counted in the Himalayan (Ganga) system are Peninsular in origin and age.

Answer: Older Peninsular rivers like the Chambal, Betwa and Son belong to the Himalayan Ganga system.

Himalayan drainage and its evolution

NCERT section The Himalayan Drainage; Evolution of the Himalayan Drainage

Character:

• Mainly the Ganga, Indus and Brahmaputra basins.
• Perennial: fed by melting snow and rain.
• In the mountains: giant gorges carved as the Himalayas rose, V-shaped valleys, rapids and waterfalls; course highly tortuous.
• In the plains: flat valleys, oxbow lakes, floodplains, braided channels, deltas; strong meandering and frequent shifts of course.
• Kosi, 'sorrow of Bihar': brings huge sediment from its upper reaches, deposits it in the plains, blocks its course and shifts channels.

Evolution (one view among differing opinions):

• A mighty river, the Shiwalik or Indo-Brahma, flowed along the whole Himalaya from Assam to Punjab and Sind, discharging into the Gulf of Sind near lower Punjab in the Miocene (about 5-24 million years ago). Evidence: the remarkable continuity of the Shiwalik, its lacustrine origin and alluvial deposits (sand, silt, clay, boulders, conglomerates).
• It was dismembered into: (i) the Indus and its five tributaries (west); (ii) the Ganga and its Himalayan tributaries (centre); (iii) the Brahmaputra stretch in Assam with its tributaries (east).
• Causes: the Pleistocene upheaval in the western Himalaya, including uplift of the Potwar Plateau (Delhi Ridge), which became the Indus-Ganga divide; and the down-thrusting of the Malda gap (between the Rajmahal hills and Meghalaya plateau) in the mid-Pleistocene, which diverted the Ganga and Brahmaputra to the Bay of Bengal.

Worked example

What evidence supports the existence of the Indo-Brahma river? (2 marks)

Try it first, then show the solutionSolution

1. The remarkable continuity of the Shiwalik hills along the Himalaya.
2. Their lacustrine origin and alluvial deposits of sand, silt, clay, boulders and conglomerates, as left by a great river.

Answer: Continuous Shiwaliks with lake and river deposits along the whole range.

The Indus system

NCERT section The River Systems of the Himalayan Drainage

Indus (Sindhu):

• One of the world's largest basins: 11,65,000 sq km (India 321,289 sq km); length 2,880 km (India 1,114 km). Westernmost Himalayan river of India.
• Source: a glacier near Bokhar Chu (31°15'N, 81°40'E), 4,164 m, Kailash range, Tibet; called Singi Khamban (Lion's mouth).
• Flows north-west between the Ladakh and Zaskar ranges, through Ladakh and Baltistan; forms a spectacular gorge near Gilgit; enters Pakistan near Chilas (Dardistan).
• Himalayan tributaries: Shyok, Gilgit, Zaskar, Hunza, Nubra, Shigar, Gasting, Dras. At Attock it receives the Kabul (right bank); other right-bank tributaries (from the Sulaiman ranges): Khurram, Tochi, Gomal, Viboa, Sangar.
• Receives the Panjnad (Satluj, Beas, Ravi, Chenab, Jhelum) above Mithankot; enters the Arabian Sea east of Karachi. In India it flows through Ladakh and Jammu and Kashmir.

Tributaries:

River	Source and key points
Jhelum	Spring at Verinag at the foot of the Pir Panjal; through Srinagar and Wular lake; deep gorge into Pakistan; joins the Chenab near Jhang
Chenab	Largest tributary; Chandra + Bhaga meet at Tandi near Keylong (hence Chandrabhaga); 1,180 km before Pakistan
Ravi	West of the Rohtang pass, Kullu hills; Chamba valley; between Pir Panjal and Dhauladhar; joins the Chenab near Sarai Sidhu
Beas	Beas Kund near Rohtang (4,000 m); Kullu valley; gorges at Kati and Largi; meets the Satluj near Harike
Satluj	Raksas tal near Mansarovar (4,555 m), called Langchen Khambab; parallel to the Indus for 400 km; through Shipki La; gorge at Rupar; antecedent river; feeds the Bhakra Nangal canal system

Worked example

Which river is not part of the Panjnad: Ravi, Chenab, Indus or Jhelum? Name the five Panjnad rivers. (2 marks)

Try it first, then show the solutionSolution

1. The Panjnad is the name for the five rivers of Punjab that join the Indus.
2. They are the Satluj, Beas, Ravi, Chenab and Jhelum; the Indus itself is not one of them.

Answer: The Indus; Panjnad = Satluj, Beas, Ravi, Chenab, Jhelum.

The Ganga system

NCERT section The River Systems of the Himalayan Drainage

Ganga:

• Most important river in basin size and culture. Rises in the Gangotri glacier near Gaumukh (3,900 m), Uttarkashi, as the Bhagirathi; cuts the Central and Lesser Himalayas in gorges.
• Devprayag: Bhagirathi meets Alaknanda → Ganga. The Alaknanda rises in the Satopanth glacier above Badrinath; it is formed by the Dhauli and Vishnu Ganga at Joshimath (Vishnu Prayag); the Pindar joins at Karna Prayag, the Mandakini (Kali Ganga) at Rudra Prayag.
• Enters the plains at Haridwar; flows south, south-east and east; splits into the Bhagirathi and Padma.
• Length 2,525 km: Uttarakhand 110 km, Uttar Pradesh 1,450 km, Bihar 445 km, West Bengal 520 km. Basin about 8.6 lakh sq km in India; the largest river system in India.
• Right-bank: Son (major). Left-bank: Ramganga, Gomati, Ghaghara, Gandak, Kosi, Mahananda. Enters the Bay of Bengal near Sagar Island.
• Namami Gange Programme (flagship, June 2014): abatement of pollution and rejuvenation of the Ganga.

Tributaries:

River	Key points
Yamuna	Westernmost and longest tributary; Yamunotri glacier, Banderpunch range (6,316 m); joins at Prayag (Allahabad); right bank: Chambal, Sind, Betwa, Ken (from the Peninsula); left bank: Hindan, Rind, Sengar, Varuna; feeds Western and Eastern Yamuna and Agra canals
Chambal	Near Mhow, Malwa plateau; gorge above Kota (Gandhisagar dam); Bundi, Sawai Madhopur, Dholpur; famous badland ravines
Gandak	Kaligandak + Trishulganga; Nepal Himalaya between Dhaulagiri and Everest; enters Bihar in Champaran; joins at Sonpur near Patna
Ghaghara	Glaciers of Mapchachungo; Tila, Seti, Beri; gorge at Shishapani; Sarda joins it; meets the Ganga at Chhapra
Kosi	Antecedent; source north of Everest (Arun); Son Kosi (west) + Tamur Kosi (east) → Sapt Kosi
Ramganga	Garhwal hills near Gairsain; enters UP plains near Najibabad; joins near Kannauj
Damodar	Eastern margins of the Chotanagpur plateau; rift valley; joins the Hugli; tributary Barakar; once 'sorrow of Bengal', tamed by the Damodar Valley Corporation
Sarda (Saryu)	Milam glacier (Goriganga); Kali or Chauk on the Indo-Nepal border; joins the Ghaghara
Mahananda	Darjiling hills; last left-bank tributary, in West Bengal
Son	Large south-bank tributary from Amarkantak; waterfalls at the plateau edge; joins near Arrah, west of Patna

Worked example

Using NCERT's figures, what share of the Ganga's 2,525 km length lies in Uttar Pradesh? (1 mark)

Try it first, then show the solutionSolution

1. Uttar Pradesh share = 1,450 km.
2. 1,450 ÷ 2,525 × 100 ≈ 57.4 per cent.

Answer: About 57 per cent.

The Brahmaputra system

NCERT section The River Systems of the Himalayan Drainage

• One of the world's largest rivers; source: Chemayungdung glacier, Kailash range, near Mansarovar.
• Flows east for about 1,200 km through dry, flat southern Tibet as the Tsangpo ('the purifier'); main right-bank tributary in Tibet: Rango Tsangpo.
• Carves a deep gorge near Namcha Barwa (7,755 m); emerges from the foothills as the Siang or Dihang; enters India west of Sadiya (Arunachal Pradesh).
• Flowing south-west it receives the Dibang (Sikang) and Lohit (left bank); thereafter called the Brahmaputra.
• In its 750 km through the Assam valley: left-bank tributaries Burhi Dihing, Dhansari (South); right-bank Subansiri, Kameng, Manas, Sankosh. The Subansiri (from Tibet) is antecedent.
• Enters Bangladesh near Dhubri and flows south; the Tista joins on the right, after which it is the Jamuna; it merges with the Padma and enters the Bay of Bengal.
• Known for floods, channel shifting and bank erosion, because its tributaries are large and carry heavy sediment due to heavy rain in the catchment.

Worked example

Why is the Brahmaputra known for floods and bank erosion? (2 marks)

Try it first, then show the solutionSolution

1. Most of its tributaries are large and bring large quantities of sediment.
2. This is because of heavy rainfall in its catchment, causing floods, channel shifting and bank erosion.

Answer: Large, sediment-laden tributaries fed by heavy rainfall.

Peninsular drainage: features and evolution

NCERT section The Peninsular Drainage System

Older than the Himalayan system: shown by broad, largely graded, shallow valleys and mature rivers.

Water divide: the Western Ghats, close to the west coast, separate the major rivers flowing to the Bay of Bengal from small rivulets to the Arabian Sea.

Direction: most major rivers flow west to east, except the Narmada and Tapi. The Chambal, Sind, Betwa, Ken and Son (from the north of the Peninsula) belong to the Ganga system. Other major systems: Mahanadi, Godavari, Krishna, Kaveri.

Characteristics: fixed course, absence of meanders, non-perennial flow; the Narmada and Tapi in rift valleys are exceptions.

Three geological events shaped it:
1. Subsidence of the western flank of the Peninsula below the sea in the early Tertiary, disturbing the symmetry of rivers on either side of the original watershed.
2. Upheaval of the Himalayas, when the northern flank subsided with trough faulting; the Narmada and Tapi flow in trough faults and fill the original cracks with detritus, so they lack alluvial and deltaic deposits.
3. Slight tilting of the Peninsular block from north-west to south-east, orienting the drainage towards the Bay of Bengal.

Worked example

Why do the Narmada and Tapi not form deltas? (2 marks)

Try it first, then show the solutionSolution

1. They flow in trough faults (rift valleys) formed when the northern flank of the Peninsula subsided during the Himalayan upheaval.
2. They fill these original cracks with their detritus, so they lack alluvial and deltaic deposits (and end in estuaries, e.g. the Narmada's 27 km estuary).

Answer: They flow in rift valleys and deposit their load in the faults, forming estuaries, not deltas.

Peninsular river systems

NCERT section The Peninsular Drainage System

River	Source	Length / basin	Key points
Mahanadi	Near Sihawa, Raipur district, Chhattisgarh	851 km; 1.42 lakh sq km	Through Odisha to the Bay of Bengal; some navigation in the lower course; basin 53% MP and Chhattisgarh, 47% Odisha
Godavari (Dakshin Ganga)	Nasik district, Maharashtra	1,465 km; 3.13 lakh sq km	Largest Peninsular system; basin 49% Maharashtra, 20% MP and Chhattisgarh, rest Andhra Pradesh; tributaries Penganga, Indravati, Pranhita, Manjra; floods below Polavaram (gorge); navigable only in the delta; splits after Rajamundri into a large delta
Krishna	Near Mahabaleshwar, Sahyadri	1,401 km	Second largest east-flowing river; tributaries Koyna, Tungabhadra, Bhima; basin 27% Maharashtra, 44% Karnataka, 29% Andhra Pradesh and Telangana
Kaveri	Brahmagiri hills (1,341 m), Kodagu, Karnataka	800 km; 81,155 sq km	Upper basin gets south-west monsoon (summer) rain, lower basin north-east monsoon (winter) rain, so it flows all year with less fluctuation; basin 3% Kerala, 41% Karnataka, 56% Tamil Nadu; tributaries Kabini, Bhavani, Amravati
Narmada	Western flank of Amarkantak (about 1,057 m)	1,312 km; about 98,796 sq km	Rift valley between Satpura (south) and Vindhyan (north); gorge in marble rocks and Dhuandhar falls near Jabalpur; 27 km estuary south of Bharuch; Sardar Sarovar Project
Tapi	Multai, Betul district, MP	724 km; 65,145 sq km	West-flowing; basin 79% Maharashtra, 15% MP, 6% Gujarat
Luni	Near Pushkar in two branches (Saraswati, Sabarmati) joining at Govindgarh	-	Largest river system of Rajasthan, west of the Aravali; west to Telwara, then south-west to the Rann of Kachchh; ephemeral

Worked example

Why does the Kaveri carry water throughout the year with less fluctuation than other Peninsular rivers? (2 marks)

Try it first, then show the solutionSolution

1. Its upper catchment receives rain from the south-west monsoon in summer.
2. Its lower catchment receives rain from the north-east monsoon in winter, so it gets water in both seasons.

Answer: Rain in both monsoons feeds different parts of its basin.

Extent of usability of river water

NCERT section Extent of Usability of River Water

Uneven water: rivers carry huge volumes but unevenly in time and space. Perennial rivers flow all year; non-perennial ones have little water in the dry season. In the rainy season much water is wasted in floods and flows to the sea; when one part floods, another may suffer drought: a question of management as much as availability.

Inter-basin linkage: transferring surplus water to deficit basins. Examples NCERT lists for teachers to explain include the Indira Gandhi Canal Project, the Periyar Diversion Scheme, the Beas-Satluj Link Canal, the Kurnool-Cuddapah Canal and the Ganga-Kaveri Link Canal. Questions raised: is a canal enough, how to lift water from plains to plateau (uneven terrain), and is there regular surplus in northern rivers.

Problems in using river water (for ranking):
1. Not available in sufficient quantity
2. River water pollution
3. Silt load
4. Uneven seasonal flow
5. Inter-state river water disputes
6. Shrinking channels as settlements extend towards the thalweg

Pollution sources: city sewage, industrial effluents and wastes, cremation and bodies thrown in rivers, immersion of flowers and idols during festivals, large-scale bathing and washing. Remedies: schemes such as the Ganga Action Plan, the campaign to clean the Yamuna at Delhi, and Namami Gange (and the Narmada conservation mission Namami Devi Narmade).

Worked example

In the same monsoon, Assam faces floods while parts of Rajasthan and Tamil Nadu face drought. How could linking rivers help, and what difficulty does the terrain pose? (2 marks)

Try it first, then show the solutionSolution

1. Linking would carry surplus water from flood-prone basins to water-deficit basins, easing both floods and droughts and giving more assured water for irrigation and drinking in dry areas.
2. Terrain is a problem: water would have to be lifted from the plains over the higher Peninsular uplands, so a simple canal is not enough.

Answer: Transfers surplus to deficit areas (flood and drought relief, irrigation, drinking water); uneven terrain makes transfer difficult.

Drainage System in real life

Each concept, met in an everyday situation. Read the situation, answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

Topics in this chapter

• Drainage Patterns, Classification of Indian Drainage and Himalayan versus Peninsular Rivers
• Major River Systems: Indus, Ganga, Brahmaputra, Peninsular Rivers and Use of River Water

Drainage System: key facts

Drainage by sea

Bay of Bengal about 77% | Arabian Sea about 23%

Divided by the Delhi ridge, Aravalis and Sahyadris.

Basins by size

• •Major > 20,000 sq km (14)
• •medium 2,000-20,000 (44)
• •minor < 2,000

Watersheds small, basins large.

Patterns

Dendritic	tree
radial	from hill
trellis	right angles
centripetal	into a lake

Amarkantak = radial.

Indo-Brahma

Miocene (5-24 Ma) → dismembered into Indus, Ganga, Brahmaputra (Pleistocene uplift of Potwar plateau; Malda gap down-throw)

Evidence: Shiwalik continuity and deposits.

Indus figures

Basin 11,65,000 sq km (India 321,289); length 2,880 km (India 1,114)

Source near Bokhar Chu, 4,164 m.

Ganga figures

$2,525km=Uttarakhand110+UP1,450+Bihar445+WB520;basin8.6lakhsqkminIndia$

Gaumukh 3,900 m; Devprayag confluence.

Brahmaputra figures

Tsangpo about 1,200 km in Tibet; 750 km in the Assam valley; gorge near Namcha Barwa (7,755 m)

Becomes Jamuna after the Tista joins.

Peninsular lengths

$Godavari1,465|Krishna1,401|Narmada1,312|Mahanadi851|Kaveri800|Tapi724km$

Godavari largest Peninsular system.

Basin share

$Areainastate=basinarea\times stat{e}^{\prime }spercentage÷100$

e.g. Tapi in Maharashtra: 65,145 × 79% ≈ 51,465 sq km.

Drainage System: diagrams to practise

Practise each one on paper: draw it from the checklist, then tick off every label.

Drainage System: map work

The places on the official CBSE map list for this chapter. Find each one on an outline map of India and practise marking it.

How the school exam asks Drainage System

The question patterns to expect, and the method that works for each.

Tricks to remember Drainage System

Short memory aids. Say each one aloud once, then use it on a question the same day.

• Panjnad

  'Sweet Bananas Ripen Can Juicy': Satluj, Beas, Ravi, Chenab, Jhelum.

  Use it when: Five rivers of Punjab.

• Ganga left-bank tributaries

  'Ram Goes Ghar Gandak Kosi Mahan': Ramganga, Gomati, Ghaghara, Gandak, Kosi, Mahananda.

  Use it when: Left-bank tributaries in order.

• Prayags downstream

  'Very Kind Rivers Dance': Vishnu, Karna, Rudra, Dev Prayag.

  Use it when: Alaknanda-Bhagirathi confluences.

• Peninsular lengths

  'God Kept Nature Mighty, Kind, Tidy': Godavari 1,465, Krishna 1,401, Narmada 1,312, Mahanadi 851, Kaveri 800, Tapi 724.

  Use it when: Order of lengths.

• Peninsular events

  'Sink, Split, Slope': western subsidence, trough faulting, tilt to the south-east.

  Use it when: Evolution of Peninsular drainage.

Drainage System: exam-level solved questions

Ordered from exam level to HOTS. Cover the solution, write your own, then compare step by step.

Case-study practice (Section E style)

Read the situation, then answer every part. In a school exam set on the board pattern this is a 4-mark question split into 1 + 1 + 2 marks.

Where the marks are

How a typical answer is split into step marks. Show every step: a right final answer alone rarely earns full marks.

Where students lose marks in Drainage System

The slips examiners see most often, and what to write instead.

• ✗Mistake: Mixing up Kosi and Damodar nicknames

  Both were 'sorrows'.

  Wrong working

  The Kosi is the sorrow of Bengal.

  Right working

  Kosi: sorrow of Bihar. Damodar: once sorrow of Bengal, tamed by the DVC.

  ✓Do this: Kosi-Bihar (both have an 'i'); Damodar-Bengal (D then B, as in DVC's home state).

  Usually costs: 1 mark per MCQ.

• ✗Mistake: Wrong prayag order

  Four similar names.

  Wrong working

  Bhagirathi and Alaknanda meet at Rudra Prayag.

  Right working

  They meet at Devprayag; Rudra Prayag is where the Mandakini joins the Alaknanda.

  ✓Do this: 'Very Kind Rivers Dance': Vishnu, Karna, Rudra, Dev downstream.

  Usually costs: 1 mark.

• ✗Mistake: Saying the Narmada forms a delta

  Assuming all big rivers form deltas.

  Wrong working

  The Narmada forms a large delta in Gujarat.

  Right working

  The Narmada flows in a rift valley and forms a 27 km estuary south of Bharuch.

  ✓Do this: Rift rivers end in estuaries.

  Usually costs: 1-2 marks.

• ✗Mistake: Calling the Yamuna a left-bank tributary from the Peninsula

  Confusing the Yamuna with its own tributaries.

  Wrong working

  The Yamuna rises in the Peninsular plateau.

  Right working

  The Yamuna rises in the Yamunotri glacier; its right-bank tributaries Chambal, Sind, Betwa, Ken come from the Peninsula.

  ✓Do this: Yamuna from ice; its right bank from rock.

  Usually costs: 1 mark.

• ✗Mistake: Drawing the Tapi north of the Narmada

  Map positions mixed.

  Wrong working

  Tapi drawn between the Vindhyan and Satpura.

  Right working

  The Narmada flows between the Vindhyan and Satpura; the Tapi is south of the Satpura, parallel to the Narmada.

  ✓Do this: N before T, north to south.

  Usually costs: 1 map mark.

NCERT exercise guide: Drainage System

What each exercise in the NCERT chapter tests, how to approach it, and a question of the same kind solved step by step. Questions here are written in our own words.

Practice questions on Drainage System

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

1. Q1 · 1 mark · MCQExam level

   Which river system is the largest in India, draining about 8.6 lakh sq km within the country?
   (a) Indus
   (b) Brahmaputra
   (c) Ganga
   (d) Godavari

   Hint

   Perennial Himalayan and non-perennial Peninsular tributaries both join it.

   Answer

   (c) Ganga.

2. Q2 · 1 mark · MCQExam level

   The Alaknanda and the Bhagirathi meet at:
   (a) Vishnu Prayag
   (b) Rudra Prayag
   (c) Karna Prayag
   (d) Devprayag

   Hint

   After this the river is called the Ganga.

   Answer

   (d) Devprayag.

3. Q3 · 1 mark · Assertion-reasonHarder exam level

   Assertion (A): The Satluj is an antecedent river.
   Reason (R): It passes through the Shipki La on the Himalayan ranges and comes out of a gorge at Rupar.
   Choose (a)-(d).

   Hint

   Both statements are in NCERT; does R define 'antecedent'?

   Answer

   (b). Both are true, but R describes its route; it does not by itself explain what makes a river antecedent (existing before the uplift and keeping its course).

4. Q4 · 2 marks · Short answerExam level

   A district plans its water use separately for each small stream catchment, while the state plans for the whole Krishna catchment. Which unit is the river basin and which the watershed, and how do they differ? (2 marks)

   Hint

   Size of catchment.

   Answer

   The state's unit (the whole Krishna catchment) is the river basin, the large catchment of a major river; the district's small stream catchments are watersheds, the catchments of rivulets and rills. Basins are large; watersheds are small units used for local planning.

5. Q5 · 3 marks · Short answerExam level

   A dam engineer says Peninsular rivers are easier to plan for than Himalayan ones because they "stay put". Using three characteristics of Peninsular rivers, explain what she means and give one drawback. (3 marks)

   Hint

   Fixed course, no meanders, seasonal flow.

   Answer

   Peninsular rivers have fixed courses, no meanders and broad, graded, shallow valleys, so their channels do not shift like the Kosi. The drawback is that they are non-perennial, fed only by rain, so their flow drops sharply in the dry season (the Kaveri is steadier). The Narmada and Tapi, in rift valleys, are exceptions in forming estuaries.

6. Q6 · 3 marks · Short answerHOTS / competency

   Suppose a state plans to link a north Indian river to a Deccan river by a canal. Using the chapter, list three practical problems it must solve. (3 marks)

   Hint

   Terrain, surplus, disputes.

   Answer

   Uneven terrain: water must be lifted from the plains to the plateau. Surplus: it must check that northern rivers have regular surplus water (flow is seasonal). Disputes and silt: inter-state water disputes and heavy silt loads must be managed.

7. Q7 · 2 marks · Short answerHarder exam level

   Why are the Himalayan rivers perennial while most Peninsular rivers are not? (2 marks)

   Hint

   Sources of water.

   Answer

   Himalayan rivers are fed by both melting snow and rainfall, so they flow all year; Peninsular rivers depend on rain alone, so they carry little water in the dry season.

8. Q8 · 5 marks · Long answerHarder exam level

   Describe the three geological events that shaped Peninsular drainage. (5 marks)

   Hint

   Subsidence, trough faulting, tilting.

   Answer

   (i) Subsidence of the western flank below the sea in the early Tertiary, disturbing the symmetry of rivers on either side of the original watershed. (ii) Himalayan upheaval with subsidence of the northern flank and trough faulting; the Narmada and Tapi flow in these troughs and lack deltaic deposits. (iii) Slight tilting of the block from north-west to south-east, orienting the drainage towards the Bay of Bengal. Result: east-flowing rivers with deltas and two west-flowing rift-valley rivers with estuaries.

9. Q9 · 2 marks · Short answerHOTS / competency

   Rank and justify two problems in using river water that you think most serious in a big city on a river. (2 marks)

   Hint

   Pollution, shrinking channels.

   Answer

   Pollution (sewage, industrial effluents, washing and immersion make water unusable) and shrinking channels as settlements extend towards the thalweg (raising flood risk). Both arise from urban pressure.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1. 1.What is a watershed?Show answer

   The boundary line separating one drainage basin from another (also the small catchment of rivulets).

2. 2.What share of India's drainage area drains into the Bay of Bengal?Show answer

   About 77 per cent.

3. 3.In which period did the Indo-Brahma river flow?Show answer

   The Miocene, some 5-24 million years ago.

4. 4.Where does the Jhelum rise?Show answer

   A spring at Verinag at the foot of the Pir Panjal.

5. 5.Which is the largest tributary of the Indus?Show answer

   The Chenab.

6. 6.What is the Tsangpo?Show answer

   The name of the Brahmaputra in Tibet, meaning 'the purifier'.

7. 7.Why is the Godavari called Dakshin Ganga?Show answer

   It is the largest Peninsular river system.

8. 8.Name the largest river system of Rajasthan.Show answer

   The Luni.

Quick revision checklist

The night before the exam: can you do each of these without looking?

• ☐Drainage: flow through defined channels; pattern depends on rocks, slope, time, water.
• ☐Patterns: dendritic (plains), radial (Amarkantak), trellis, centripetal.
• ☐Basin, catchment, watershed; basins are planning units.
• ☐Bay of Bengal 77%, Arabian Sea 23%; major 14, medium 44 basins.
• ☐Himalayan: perennial, gorges, meanders, course shifts (Kosi); Indo-Brahma dismembered by Potwar uplift and Malda gap.
• ☐Indus: 2,880 km; Panjnad above Mithankot; Chenab largest tributary; Satluj antecedent (Bhakra Nangal).
• ☐Ganga: Gaumukh, Devprayag, Haridwar; 2,525 km; Yamuna longest tributary; Son right bank; Damodar sorrow of Bengal.
• ☐Brahmaputra: Tsangpo, Namcha Barwa gorge, Siang, Sadiya, Dhubri, Jamuna; floods and bank erosion.
• ☐Peninsular: older, fixed course, no meanders, non-perennial; three events; Narmada and Tapi in rift valleys.
• ☐Godavari largest (1,465 km); Krishna 1,401; Kaveri steady (two monsoons); Narmada estuary 27 km; Luni ephemeral.
• ☐Usability: uneven flow, floods and droughts, inter-basin links, pollution.

Drainage System: frequently asked questions