class 11 notes

Class 11 Geography Notes Chapter 3 (Drainage system) – India Physical Environment Book

Philoid

Philoid

— 10 min read

India Physical Environment
Alright class, let's delve into one of the most crucial topics for understanding India's physical geography – the Drainage System. This chapter is vital not just for your Class 11 understanding but forms a significant part of the syllabus for various government examinations. Pay close attention to the key terms, river systems, and their characteristics.

Chapter 3: Drainage System - Detailed Notes

1. Introduction: Basic Concepts

  • Drainage: The flow of water through well-defined channels.
  • Drainage System: A network of such channels (rivers, streams).
  • Drainage Basin/River Basin: The area drained by a single river system (a major river and its tributaries).
  • Catchment Area: The area from which a river collects its water, essentially synonymous with the river basin.
  • Watershed: The boundary line separating one drainage basin from another. While often used interchangeably with 'drainage basin', 'watershed' technically refers to the dividing line, but is commonly used for smaller basins/catchments of smaller rivers or rivulets.
  • River Regime: The pattern of flow of water in a river channel over a year, influenced by rainfall seasonality, snowmelt, groundwater contribution, etc.

2. Drainage Patterns

The geometric arrangement of streams in a region; determined by slope, geological structure, rock type, and climate. Major patterns in India:

  • Dendritic: Tree-branch like pattern. Develops where the river channel follows the slope of the terrain in areas with uniform rock structure. Example: Most rivers of the Indo-Gangetic plains.
  • Trellis: Rectangular pattern formed where tributaries join the main river at nearly right angles. Develops in regions of parallel, folded, or tilted hard and soft rock strata. Example: Rivers in the Himalayan foothills, older folded mountains.
  • Radial: Streams flow in different directions from a central peak or dome-like structure. Example: Rivers originating from the Amarkantak range (Narmada, Son).
  • Centripetal: Streams converge from all directions into a central depression or lake. Example: Streams in Ladakh, Loktak Lake area in Manipur.

3. Classification of Indian Drainage Systems

Indian drainage systems can be classified on different bases:

(A) Based on Discharge Orientation (Sea)

  • Arabian Sea Drainage: Rivers draining into the Arabian Sea (approx. 23% of total drainage area). Includes Indus, Narmada, Tapi, Sabarmati, Mahi, and numerous small swift rivers of the Western Ghats (e.g., Periyar, Sharavati).
  • Bay of Bengal Drainage: Rivers draining into the Bay of Bengal (approx. 77% of total drainage area). Includes Ganga, Brahmaputra, Mahanadi, Godavari, Krishna, Kaveri, Subarnarekha, etc.
  • Water Divide: An elevated area (mountain or upland) separating these two drainage systems. Major examples in India include the Delhi Ridge, Aravallis, and the Sahyadris (Western Ghats).

(B) Based on Mode of Origin, Nature, and Characteristics

  • The Himalayan Drainage System:
    • Origin: Originate in the Himalayas, fed by glaciers and rainfall.
    • Nature: Perennial (flow throughout the year). Antecedent (existed before the Himalayas uplifted and cut gorges) and consequent rivers.
    • Course: Long courses, flow through rugged mountains, experience intense headward erosion and river capturing. Form deep V-shaped valleys, gorges, rapids, and waterfalls in upper reaches. Enter plains, form depositional features like flat valleys, ox-bow lakes, braided channels, floodplains, levees, and deltas. Course is often meandering in plains and frequently shifts.
    • Basins: Large basins.
    • Stage: Youthful stage in mountains, mature/old stage in plains.
  • The Peninsular Drainage System:
    • Origin: Originate mainly in the Peninsular Plateau and central highlands, mostly rain-fed.
    • Nature: Mostly seasonal/non-perennial (flow dependent on monsoon rains), except for rivers like Kaveri which have a more complex regime. Consequent rivers, following the slope.
    • Course: Shorter and shallower courses compared to Himalayan rivers. Flow through relatively stable, hard rock areas. Limited erosional activity. Characterized by broad, shallow valleys. Generally straight courses with low meandering due to hard rock base.
    • Basins: Relatively smaller basins.
    • Stage: Old stage, graded profiles (smooth slope), indicating they are close to the base level of erosion.

4. Evolution of Drainage Systems

  • Himalayan Drainage: Believed to have evolved through the Miocene period (about 24 million years ago) possibly from a single mighty river called the "Indo-Brahma" or "Siwalik River". This river flowed longitudinally along the foothills from Assam to Punjab and Sindh, discharging into the Gulf of Sindh. Later dismembered due to:
    • Pleistocene upheaval in the western Himalayas (Potwar Plateau uplift creating the Indus-Ganga divide).
    • Down-thrusting of the Malda gap area (between Rajmahal hills and Meghalaya plateau), diverting the Ganga eastwards to the Bay of Bengal.
  • Peninsular Drainage: Shaped by major geological events:
    • Subsidence of the western flank of the Peninsula during the early Tertiary period, leading to submergence below the sea. This disturbed the symmetry of river basins.
    • Upheaval of the Himalayas, causing subsidence of the northern flank of the Peninsular block and consequent trough faulting (leading to rift valleys for Narmada and Tapi).
    • Slight tilting of the Peninsular block from northwest to southeast, orienting major river flows towards the Bay of Bengal.

5. Major River Systems

(A) The Himalayan Rivers

  • The Indus System:

    • Source: Bokhar Chu glacier near Mansarovar Lake, Tibetan plateau. Known as ‘Singi Khamban’ (Lion’s mouth) in Tibet.
    • Course: Flows NW through Ladakh, enters Pakistan near Chilas (Gilgit-Baltistan). Cuts a deep gorge near Attock.
    • Tributaries (India): Zaskar, Shyok, Nubra, Hunza (in Ladakh).
    • Panjnad (Punjab Tributaries):
      • Jhelum (Vitasta): Rises from Verinag spring (Pir Panjal). Flows through Srinagar and Wular Lake. Joins Chenab near Jhang (Pakistan).
      • Chenab (Chandrabhaga): Largest tributary of Indus. Formed by two streams, Chandra and Bhaga, meeting at Tandi (HP).
      • Ravi (Iravati): Rises west of Rohtang Pass (Kullu hills, HP). Flows through Chamba valley. Joins Chenab near Sarai Sidhu.
      • Beas (Vipasa): Rises from Beas Kund near Rohtang Pass (HP). Flows through Kullu Valley. Meets Satluj near Harike (Punjab). Entirely within India.
      • Satluj (Satadru): Originates from Rakas Lake near Mansarovar (Tibet), known as Langchen Khambab. Enters India via Shipki La pass (HP). An antecedent river. Feeds Bhakra Nangal project. Joins Chenab.
    • Discharge: Arabian Sea, east of Karachi.
    • Indus Water Treaty (1960): India controls waters of Ravi, Beas, Satluj (Eastern rivers). Pakistan controls waters of Indus, Jhelum, Chenab (Western rivers). India can use 20% of the water of western rivers for irrigation, power generation, and transport.
    • Length: ~2,880 km (Total), ~1,114 km (in India).
    • Basin: Covers parts of J&K, Ladakh, HP, Punjab.

  • The Ganga System:

    • Source: Rises in Gangotri glacier near Gaumukh (Uttarkashi, Uttarakhand) as Bhagirathi.
    • Formation of Ganga: Bhagirathi joins Alaknanda (originating from Satopanth glacier above Badrinath) at Devprayag.
    • Panch Prayag (Confluences along Alaknanda):
      • Vishnuprayag: Dhauliganga meets Alaknanda
      • Nandaprayag: Nandakini meets Alaknanda
      • Karnaprayag: Pindar meets Alaknanda
      • Rudraprayag: Mandakini (from Kedarnath) meets Alaknanda
      • Devprayag: Bhagirathi meets Alaknanda
    • Course: Enters plains at Haridwar. Flows south, then southeast through UP, Bihar, West Bengal. Bifurcates near Farakka (WB) into Hooghly (distributary, flows south through Kolkata) and Padma (main branch, enters Bangladesh). In Bangladesh, Padma joins Jamuna (Brahmaputra) and later Meghna, forming the vast Ganga-Brahmaputra Delta (Sundarbans).
    • Length: ~2,525 km (Longest river in India).
    • Basin: Largest river basin in India, covering parts of Uttarakhand, UP, MP, Rajasthan, Haryana, HP, Chhattisgarh, Jharkhand, Bihar, West Bengal, Delhi.
    • Right Bank Tributaries:
      • Yamuna: Longest tributary. Rises from Yamunotri glacier (Bandarpunch range). Joins Ganga at Prayagraj (Allahabad). Tributaries: Chambal, Sind, Betwa, Ken (flow from Peninsular plateau).
      • Chambal: Rises near Mhow (MP). Flows through a gorge, known for badland topography (Chambal ravines). Tributaries: Banas, Kali Sindh, Parbati.
      • Son: Large south bank tributary. Rises from Amarkantak plateau. Joins Ganga near Patna.
      • Damodar: Rises in Chotanagpur plateau. Flows through a rift valley. Known as 'Sorrow of Bengal'. Joins Hooghly. (Note: Technically joins Hooghly, a distributary, not Ganga directly in its main course).
    • Left Bank Tributaries:
      • Ramganga: Rises in Garhwal hills. Joins Ganga near Kannauj.
      • Ghaghara (Saryu): Rises from Mapchachungo glacier (Tibet). Cuts a deep gorge. Joins Ganga at Chhapra (Bihar). Tributaries: Sarda (Kali/Kali Ganga), Rapti.
      • Gandak: Formed by Kali Gandak and Trishulganga (Nepal Himalayas). Joins Ganga at Sonpur near Patna.
      • Kosi: Rises north of Mt. Everest (Tibet/Nepal). Consists of 7 streams (Sapt Kosi). Known as 'Sorrow of Bihar' due to frequent course changes and floods. Joins Ganga near Kursela.
      • Mahananda: Rises in Darjeeling hills. Last major left bank tributary in West Bengal. Joins Ganga/Padma.

  • The Brahmaputra System:

    • Source: Chemayungdung glacier, Kailash range near Mansarovar Lake.
    • Course: Flows eastwards parallel to Himalayas in Tibet as Tsangpo (meaning 'the purifier'). Takes a U-turn around Namcha Barwa (7756m) and enters India in Arunachal Pradesh through a deep gorge as Dihang or Siang. Joined by Dibang and Lohit near Sadiya (Assam) to form the Brahmaputra. Flows westwards through Assam valley. Enters Bangladesh near Dhubri as Jamuna. Joins Padma (Ganga) and then Meghna before emptying into Bay of Bengal.
    • Characteristics: Known for floods, channel shifting, and formation of braided channels and riverine islands (e.g., Majuli - largest riverine island in the world). Carries large sediment load.
    • Length: ~2,900 km (Total, longer than Indus/Ganga), but most lies outside India. ~916 km in India.
    • Basin: Covers parts of Arunachal Pradesh, Assam.
    • Major Tributaries:
      • Left Bank: Dibang (Sikang), Lohit, Burhi Dihing, Dhansiri, Kopili.
      • Right Bank: Subansiri (antecedent river), Kameng (Jia Bharali), Manas, Sankosh, Teesta (rose in Sikkim, joined Ganga earlier, now joins Jamuna/Brahmaputra in Bangladesh after 1787 floods).

(B) The Peninsular Rivers

  • East Flowing Rivers (Delta forming, drain into Bay of Bengal):

    • Mahanadi: Rises in Sihawa, Raipur district (Chhattisgarh). Flows through Odisha. Forms a large delta. Hirakud Dam is built on it. Tributaries: Seonath, Hasdeo, Mand, Ib (Left); Ong, Tel, Jonk (Right).
    • Godavari (Dakshin Ganga / Vridha Ganga): Largest Peninsular river. Rises from Trimbakeshwar, Nashik district (Maharashtra). Flows southeast across Deccan Plateau. Forms a large delta. Tributaries: Penganga, Wainganga, Wardha (collectively called Pranhita), Indravati, Sabari (Left); Manjra (Right).
    • Krishna: Second largest east-flowing Peninsular river. Rises near Mahabaleshwar, Sahyadri (Maharashtra). Forms a large delta. Tributaries: Koyna, Ghatprabha, Malprabha, Bhima, Musi (Left); Tungabhadra (formed by Tunga and Bhadra), Venna (Right). Shared water disputes among Maharashtra, Karnataka, Andhra Pradesh, Telangana.
    • Kaveri (Cauvery): Rises in Brahmagiri hills, Kodagu district (Karnataka). Flows through Karnataka and Tamil Nadu. Forms a large delta ('Garden of Southern India'). Considered sacred. Relatively less seasonal fluctuation compared to other peninsular rivers as its upper catchment receives rain during SW monsoon and lower catchment during NE retreating monsoon. Forms Sivasamudram waterfalls. Tributaries: Hemavati, Shimsha, Arkavathy (Left); Kabini, Bhavani, Noyyal, Amaravati (Right).
    • Subarnarekha: Rises near Ranchi plateau. Flows through Jharkhand, West Bengal, Odisha. Forms an estuary (though often grouped with delta-formers). Known for pollution from mining activities. Hundru falls is on this river.
    • Baitarani: Rises in Kendujhar (Keonjhar) plateau, Odisha.
    • Brahmani: Formed by the confluence of Koel and Sankh rivers near Rourkela, Odisha.
    • Pennar: Rises in Nandidurg range, Karnataka. Flows through Andhra Pradesh.
    • Vaigai: Rises in Varusanadu Hills (Tamil Nadu). Drains into Palk Strait. Flows through Madurai.

  • West Flowing Rivers (Estuary forming, drain into Arabian Sea):

    • Narmada: Rises from Amarkantak plateau (MP). Flows westwards through a rift valley between Vindhya (North) and Satpura (South) ranges. Forms Dhuandhar falls (Marble Rocks) near Jabalpur. Forms a large estuary near Bharuch (Gujarat). Sardar Sarovar Dam is built on it. Does not form a delta due to flow through hard rocks and steep gradient near the coast. Major Tributaries: Tawa, Hiran, Barna, Orsang.
    • Tapi (Tapti): Rises in Betul district (MP), Satpura ranges. Flows westwards, parallel to Narmada, also through a rift valley (south of Satpura). Forms an estuary near Surat (Gujarat). Ukai Dam is built on it. Major Tributaries: Purna, Girna, Panzara.
    • Sabarmati: Rises in Aravalli range (Rajasthan). Flows south-west through Gujarat. Drains into Gulf of Khambhat. Ahmedabad and Gandhinagar are on its banks.
    • Mahi: Rises in Vindhyan range (MP). Flows through MP, Rajasthan, Gujarat. Drains into Gulf of Khambhat. Cuts the Tropic of Cancer twice.
    • Luni: Largest river system of Rajasthan. Rises near Pushkar (Aravallis). Flows towards southwest. Ephemeral (seasonal). Drains into the Rann of Kutch (Inland Drainage). Water is brackish beyond Balotra.
    • Small West Flowing Rivers (Western Ghats): Numerous swift rivers originating in Western Ghats, short courses, steep gradients. Examples: Shetrunji (Gujarat), Vaitarna (Maharashtra), Mandovi & Zuari (Goa), Sharavati (Karnataka - forms Jog/Gersoppa Falls, India's highest untiered waterfall), Periyar & Pamba (Kerala).

6. River Regime

  • Himalayan Rivers: Perennial. Flow pattern influenced by both snowmelt (summer) and rainfall (monsoon season). Ganga has minimum flow during Jan-June, maximum in Aug/Sep. Brahmaputra has floods during monsoon due to heavy rain and snowmelt.
  • Peninsular Rivers: Seasonal. Flow heavily dependent on SW Monsoon (June-September). Godavari, Krishna, Kaveri have large fluctuations. Narmada and Tapi show less fluctuation due to groundwater/spring feeding in rift valley. Kaveri has a complex regime with peaks in SW monsoon (upper catchment) and NE monsoon (lower catchment), making it less seasonal than others.

7. Utility of Rivers

  • Water Source: Drinking, domestic use, industrial use.
  • Irrigation: Crucial for agriculture, especially in plains (canals from Himalayan rivers) and delta regions.
  • Hydroelectric Power: Dams on rivers generate electricity (e.g., Bhakra Nangal, Hirakud, Sardar Sarovar, Nagarjuna Sagar).
  • Navigation: Important waterways, especially Ganga, Brahmaputra, and backwaters of Kerala. Declining importance due to irrigation diversions and competition from railways/roads, but being revived (National Waterways).
  • Fisheries: Livelihood for many communities.
  • Ecological Significance: Support diverse aquatic ecosystems, recharge groundwater, act as natural drainage channels.
  • Cultural/Religious Significance: Many rivers considered sacred (Ganga, Yamuna, Narmada, Kaveri). Riverbanks host major cities and pilgrimage centres.

8. River Pollution

  • Causes: Untreated sewage, industrial effluents, agricultural runoff (pesticides, fertilizers), solid waste dumping, religious offerings.
  • Consequences: Water-borne diseases, loss of aquatic life, eutrophication, contamination of groundwater, reduced utility of water.
  • Initiatives: Ganga Action Plan (GAP), Namami Gange Programme aim to clean rivers, but challenges remain.

Multiple Choice Questions (MCQs)

  1. Which of the following drainage patterns resembles the branches of a tree?
    (a) Radial
    (b) Dendritic
    (c) Trellis
    (d) Centripetal

  2. The Narmada river originates from:
    (a) Trimbakeshwar Plateau
    (b) Brahmagiri Hills
    (c) Amarkantak Plateau
    (d) Mahabaleshwar

  3. Which one of the following rivers flows through a rift valley?
    (a) Godavari
    (b) Krishna
    (c) Tapi
    (d) Mahanadi

  4. The confluence of Bhagirathi and Alaknanda rivers occurs at which place, forming the Ganga?
    (a) Rudraprayag
    (b) Karnaprayag
    (c) Vishnuprayag
    (d) Devprayag

  5. Majuli, the largest riverine island in the world, is located in which river?
    (a) Ganga
    (b) Brahmaputra
    (c) Godavari
    (d) Indus

  6. Which of the following is a major right-bank tributary of the Ganga river?
    (a) Ghaghara
    (b) Kosi
    (c) Gandak
    (d) Yamuna

  7. The Indus Water Treaty (1960) gives India control over the waters of which set of rivers?
    (a) Indus, Jhelum, Chenab
    (b) Ravi, Beas, Satluj
    (c) Ganga, Yamuna, Brahmaputra
    (d) Narmada, Tapi, Mahi

  8. Which Peninsular river is known as 'Dakshin Ganga' and is the largest river system of Peninsular India?
    (a) Krishna
    (b) Kaveri
    (c) Godavari
    (d) Mahanadi

  9. The Luni river, characterized by inland drainage, drains into:
    (a) Arabian Sea
    (b) Bay of Bengal
    (c) Rann of Kutch
    (d) Sambhar Lake

  10. Which of the following is NOT a characteristic feature of Peninsular rivers compared to Himalayan rivers?
    (a) Shorter and shallower courses
    (b) Flow through hard, stable rocky terrain
    (c) Perennial flow throughout the year
    (d) Absence of deep gorges and significant meandering

Answer Key for MCQs:

  1. (b) Dendritic
  2. (c) Amarkantak Plateau
  3. (c) Tapi (Narmada also flows through a rift valley)
  4. (d) Devprayag
  5. (b) Brahmaputra
  6. (d) Yamuna (Others are left-bank tributaries)
  7. (b) Ravi, Beas, Satluj
  8. (c) Godavari
  9. (c) Rann of Kutch
  10. (c) Perennial flow throughout the year (Most Peninsular rivers are seasonal)

Make sure you revise these notes thoroughly. Understanding the river systems, their origins, tributaries, and characteristics is fundamental. Don't just memorize; try to visualize the flow on a map. Good luck with your preparation!

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