Drainage System

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

1. MCQs with Reasons

Q.No.	Question	Correct Answer	Reason
(i)	Which river is known as the Sorrow of Bengal?	(c) The Kosi 🌊	The Kosi frequently changes its course in Bihar and West Bengal, causing massive floods every year—hence the nickname.
(ii)	Largest river basin in India	(c) The Ganga 🌏	The Ganga drains an area of about 8.6 lakh sq. km, the largest in India, supporting millions through agriculture and water use.
(iii)	Not included in Panchnad	(c) The Indus 🏞️	Panchnad means “five rivers” of Punjab—Sutlej, Beas, Ravi, Chenab, Jhelum. The Indus is the main river, not part of this confluence group.
(iv)	Flows in a rift valley	(b) The Narmada ⛰️	Narmada flows west through a rift valley between Vindhya and Satpura ranges—formed by tectonic forces.
(v)	Confluence of Alaknanda & Bhagirathi	(d) Deva Prayag 🙏	At Devprayag, in Uttarakhand, the Alaknanda and Bhagirathi meet to form the holy Ganga River.

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2. Differences

(i) River Basin vs. Watershed

Aspect	River Basin 🌏	Watershed 💧
1. Size	Large area drained by a river & its tributaries	Smaller area drained by a stream
2. Scale	Macro-level	Micro-level
3. Boundaries	Formed by highlands/mountains between basins	Formed by ridges or small hills
4. Examples	Ganga Basin	A pond’s catchment area
5. Water Flow	Main river + tributaries	Only one main stream

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(ii) Dendritic vs. Trellis Drainage Pattern

Aspect	Dendritic 🌳	Trellis 🪢
1. Shape	Tree-like pattern	Rectangular/block pattern
2. Cause	Uniform rock resistance	Alternating hard & soft rocks
3. Main Stream	No specific control by rock structure	Main streams run parallel
4. Joining Tributaries	Join main river at any angle	Join main river at nearly right angles
5. Examples	Ganga River	Rivers in the Chotanagpur plateau

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(iii) Radial vs. Centripetal Drainage Pattern

Aspect	Radial ☀️	Centripetal 🎯
1. Direction of Flow	Outward from central high point	Inward towards central depression
2. Landform	Conical hills/volcanoes	Basins/lakes
3. Water Spread	Away from centre	Towards the centre
4. Examples	Rivers from Amarkantak Hills	Sambhar Lake drainage
5. Cause	High elevation at centre	Low elevation at centre

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(iv) Delta vs. Estuary

Aspect	Delta 🔺	Estuary 🌊
1. Formation	By deposition of sediments	By tidal action, no delta formation
2. Shape	Triangular fan-shaped	Funnel-shaped
3. Suitable for	Agriculture	Ports/harbours
4. Examples	Ganga-Brahmaputra Delta	Narmada Estuary
5. Sediment Load	High	Low (carried into sea)

ALTERNATE

1. River Basin vs. Watershed

A river basin is a large geographical area drained by a main river and all its tributaries. It can cover thousands of square kilometres, for example, the Ganga Basin. A watershed, on the other hand, is much smaller—it is the catchment area for a single stream or a small river. The boundaries of a river basin are marked by high mountains or ridges between basins, while a watershed’s boundary is usually a small ridge or hill. River basins operate on a macro scale, whereas watersheds are micro-scale drainage areas. In short, every river basin is made up of many smaller watersheds. 🌊

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2. Dendritic vs. Trellis Drainage Pattern

In a dendritic drainage pattern, streams branch out like the limbs of a tree, joining the main river at irregular angles. This pattern develops in regions where the rock type is uniform and does not strongly control the river’s direction. In a trellis pattern, the main rivers run parallel to each other, with short tributaries joining them at nearly right angles. This pattern forms in areas with alternating hard and soft rock bands, where softer rocks are eroded more easily, creating parallel valleys. 🌳🪢

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3. Radial vs. Centripetal Drainage Pattern

Radial drainage occurs when rivers flow outward from a central high point such as a volcano, dome, or hill—examples include rivers from the Amarkantak Hills. In centripetal drainage, rivers flow inward from all directions towards a central low area, like a basin or depression—examples include the drainage into Sambhar Lake. The key difference is that radial patterns spread water away from the centre, while centripetal patterns collect water towards the centre. ☀️🎯

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4. Delta vs. Estuary

A delta is a triangular or fan-shaped landform created by the deposition of sediments at the mouth of a river. It usually forms in slow-moving water where the river meets the sea, such as the Ganga-Brahmaputra Delta. An estuary, in contrast, is a funnel-shaped mouth of a river where freshwater mixes with seawater, often influenced by tides. Deltas are fertile and support agriculture, while estuaries are good for ports and harbours. Rivers with high sediment load form deltas, while those with strong tidal currents usually form estuaries. 🔺🌊

(i) Socio-economic advantages of inter-linking rivers in India

Inter-linking rivers helps transfer surplus water to water-deficit regions, solving floods and droughts. It improves irrigation, boosts farmers’ productivity, supplies drinking water, fosters inland water transport, and supports hydroelectricity and fisheries—thus enhancing regional economic growth.

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(ii) Three characteristics of Peninsular rivers

Peninsular rivers are shorter and fewer in number, with fixed courses and well-adjusted valleys. They depend mainly on monsoon rainfall, making them seasonal. Mostly older rivers with graded profiles, they have relatively smaller basins and shallower, broad valleys.

Q4(i) What are the important characteristic features of North Indian rivers? How are these different from Peninsular rivers?

Characteristics of North Indian Rivers 🏔️

1. Origin in the Himalayas – Most arise from glaciers and snowfields.
2. Perennial Flow – Fed by both snowmelt and rainfall, ensuring water throughout the year.
3. Long Courses – Travel great distances, creating vast drainage basins.
4. Fertile Plains – Deposit nutrient-rich alluvium, forming extensive floodplains.
5. Meandering Nature – Often change course and create oxbow lakes.
6. High Sediment Load – Carry large amounts of silt from mountains.
7. Deltas Formation – End by forming large deltas (e.g., Ganga-Brahmaputra Delta).

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Differences Between North Indian and Peninsular Rivers

Feature	North Indian Rivers 🏔️	Peninsular Rivers 🪨
Origin	Himalayas (snow + rain)	Western Ghats / Central Highlands
Flow	Perennial (water all year)	Seasonal (mainly monsoon-fed)
Length	Very long with large basins	Shorter with smaller basins
Nature	Young, active, meandering	Old, stable, straight courses
Bedrock	Flow over alluvial plains	Flow over hard, rocky terrain
Examples	Ganga, Yamuna, Brahmaputra	Godavari, Krishna, Narmada

Q4(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.

Important Rivers Along the Route 🚗🌊

While travelling from Haridwar (Uttarakhand) to Siliguri (West Bengal) along the Himalayan foothills, you may come across:

• Ganga
• Ramganga
• Kosi
• Gandak
• Kamla
• Bagmati
• Teesta

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Example – The Ganga River 🌊🙏

1. Origin – Emerges from the Gangotri Glacier in Uttarakhand as Bhagirathi.
2. Length – About 2,525 km, one of the longest rivers in India.
3. Drainage Basin – Covers vast fertile plains of north India.
4. Perennial Nature – Fed by glaciers and monsoon rains.
5. Economic Importance – Supports irrigation, transport, fishing, and religious activities.
6. Delta Formation – Forms the Sundarbans Delta, the largest in the world.

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