NCERT Summary: Indo Gangetic Plains | Geography for UPSC CSE PDF Download

The Indo-Gangetic Plains, also known as the Great Plains of North India, stretch from the Himalayan foothills to the Bay of Bengal. These fertile plains have been formed over centuries by sediment deposits from the Indus, Ganges, and Brahmaputra rivers, playing a crucial role in the cultural, economic, and ecological aspects of the subcontinent.

• Features of the Indo-Gangetic Plains

  • North-South Extension: The Indo-Gangetic Plains stretch from the southern foothills of the Himalayas to the edge of the Peninsular Plateau.
  • East-West Extension: These plains span from the mouth of the Indus River in the west to the mouth of the Ganga River in the east.
  • Boundaries: Bordered by the Shiwalik range to the north, the Desert to the west, the Peninsular Plateau to the south, and the Purvanchal Hills to the east.
  • Length: The total length of this region is 3200 km, with approximately 2400 km located in India and the remainder in Bangladesh.
  • Width: The Great Northern Plains have an average width of 150-300 km, widening to 500 km in the west and narrowing to 60-100 km in the east.
  • Area: Encompassing about 7.8 lakh sq. km, it stands as the largest alluvial plain globally.
  • States Covered: These plains span across Punjab, Haryana, Delhi, Uttar Pradesh, Bihar, parts of Jharkhand and West Bengal, and Assam.
  • Extreme Horizontality: Notably flat, with an average elevation of 200 m and the highest point at around 291 m above sea level, exhibiting a gentle gradient of 15-20 cm.
  • Soil Cover: Rich and fertile soil deposits due to sediments carried by rivers originating from the northern mountains.

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Formation of the Indo-Gangetic Plains

• The Indo-Gangetic Plains were shaped by the sediment deposits of three significant river systems: the Indus, Ganga, and Brahmaputra. These rivers filled a vast depression that was situated between the Peninsular and Himalayan regions.
• During the Tertiary Period, the movement of the Indo-Australian Plate towards the Eurasian Plate resulted in the emergence of the Himalayas. The ongoing convergence of these plates caused upheavals in the Himalayas, creating a deep depression in the form of a large syncline between the Peninsula and the Himalayas.
• Rivers originating from the Himalayas carried substantial sediment loads, which were then deposited in the deep depression. This process ultimately led to the formation of the extensive Indo-Gangetic Plains, also known as the Great Plains of India.

Regional Divisions of the Indo-Gangetic Plains

• The Rajasthan Plain
  • The western part of the Indo-Gangetic Plains is known as the Rajasthan Plain.
  • It includes the Thar or Great Indian Desert, which spans across western Rajasthan and neighboring areas in Pakistan.
  • The Rajasthan Plain can be further categorized into two main regions:
  • Marusthali: This region is characterized by arid desert conditions.
• The Punjab-Haryana Plain
• The Ganga Plain
• The Brahmaputra Plain

The Rajasthan Plain

• The Rajasthan Plain marks the western boundary of the Indo-Gangetic Plains.
• This area encompasses the Thar or Great Indian Desert, extending over western Rajasthan and parts of Pakistan.
• The Rajasthan Plain can be segmented into two distinct parts:
• Western Extremities: This area signifies the farthest western reaches of the Indo-Gangetic Plains.

The Eastern Part of the Rajasthan Plain: Marusthali

• The eastern part of the Rajasthan Plain, which is a proper desert, is known as Marusthali.
• It covers a great part of the Marwar plain.
• Although it looks like an aggradational plain on the surface, geologically it is a part of the Peninsular Plateau. This is evident from the vast stretch of sand with few outcrops of bedrock composed of gneisses, schists, and granites.
• Its eastern part is rocky, while the western part is covered by shifting sand dunes locally known as Dhrian.

Rajasthan Bagar: Semi-Arid Plain

• The eastern part of the Thar desert up to the Aravalli Range is a semi-arid plain known as Rajasthan Bagar.
• Numerous short seasonal streams originating from the Aravalli drain this area and create patches of fertile tracts called Rohi.
• The river Luni exemplifies such streams, flowing southwest of Aravalli and draining into the Rann of Kutch.
• The tract north of the Luni is referred to as Thali or sandy plain.

The Thar Desert

• The region to the north of the Luni River is known as Thali or the sandy plain.
• Thali is characterized by its sandy terrain.
• The Thar desert contains various saline lakes like Sambhar, Didwana, and Khatu.

The Punjab-Haryana Plain

• The Punjab-Haryana Plain is a significant geographical area in the region.
• It is known for its fertile land and agricultural productivity.
• This plain is a crucial agricultural hub in India.
• It is an area where wheat and rice cultivation thrives.

Description of Punjab Plain and its Features

• The Punjab Plain is situated towards the east and north-east of the Rajasthan Plain.
• Spanning a length of 640 km from northwest to southeast, it covers regions in Punjab and Haryana.
• The average width of the plain is 300 km.
• It gently slopes towards the southwest, causing rivers to flow in that direction.
• Primarily composed of silts, the soil in the plain is porous.

Special Features of the Punjab Plain

• Bet: This term refers to the area near river banks where new alluvium is deposited.
• 'Bhabar' Plain: This region consists of large boulders, gravel, sand, and clay, characterized by poor water retention.
• In Haryana, the plain is bordered to the east by the Yamuna River.
• The Punjab portion of the plain is formed due to the alluvial deposits of five rivers - Satluj, Beas, Ravi, Chenab, and Jhelum, earning the nickname 'Land of Five Rivers'.

Divisions within the Punjab Plain

• Bist-Jalandhar Doab: The region lying between the Beas and Satluj rivers.
• Bari Doab: Area between the Beas and Ravi rivers.
• Rachna Doab: The tract of land between the Ravi and Chenab rivers.
• Chaj Doab: Region between the Chenab and Jhelum rivers.
• Sind Sagar Doab: Area between the Jhelum-Chenab and Indus rivers.

Land of Five Rivers: Punjab Plain

• Punjab Plain is renowned as the 'Land of Five Rivers' due to its geographical significance.

The Five 'Doabs' of the Punjab Plain

The Punjab region of the plain comprises five 'Doabs', which are tracts of land lying between two converging rivers:

• Bist-Jalandhar Doab: Situated between the Beas and the Satluj rivers.
• Bari Doab: Positioned between the Beas and the Ravi rivers.
• Rachna Doab: Found between the Ravi and the Chenab rivers.
• Chaj Doab: Located between the Chenab and the Jhelum rivers.
• Sind Sagar Doab: Lies between the Jhelum-Chenab and the Indus rivers.

Key Features of the Punjab-Haryana Plain

• Bet Lands: These areas consist of Khadar-rich floodplains where fertile soils are deposited annually, enhancing their fertility.
• Dhayas: Broad flood plains of Khadar bordered by bluffs.
• Chos: The northern region of the plain, near the Shiwalik hills, characterized by significant erosion from numerous streams known as Chhos.

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The Ganga Plain

• The Ganga Plain is the most extensive part of the Indo-Gangetic Plains, covering an area of 3.75 lakh square kilometers.
• This vast plain is a result of the accumulation of alluvial deposits from the Ganga River and its tributaries originating from the Himalayas and the Peninsular region.
• Stretching from Delhi to Kolkata, the Ganga Plain spans across the states of Uttar Pradesh, Bihar, and West Bengal.
• The overall topography of the plain slopes towards the east and southeast, influencing the flow of water and shaping the landscape.

The Upper Ganga Plain

The Upper Ganga Plain is characterized by its rich fertility and extensive agricultural practices. This region benefits from the fertile soil deposited by the Ganga River, supporting a variety of crops such as rice, wheat, and sugarcane. The availability of water resources from the river and its tributaries further enhances agricultural productivity in this area.

Geographical Features of the Middle Ganga Plain

• Location: The Middle Ganga Plain comprises the westernmost and upper part of the Ganga Plain.
• Boundaries: Bounded by the Shiwaliks to the north, the Peninsular boundary to the south, and the Yamuna River to the west. The eastern boundary is not clearly defined.
• Average Gradient: The region exhibits a gentle slope, with an average gradient of approximately 25 cm per km.
• Distinctive Features: Due to its minimal gradient, rivers in the Middle Ganga Plain flow slowly, resulting in the formation of various riverine characteristics. These include river bluffs, meanders, oxbow lakes, levees, abandoned river courses, and sandy stretches known as Bhurs.
• Major Units: The region can be divided into three main units from west to east: Ganga-Yamuna Doab, Rohilkhand Plains, and Avadh Plains.

The Eastern Coastal Plain

• Location: The Eastern Coastal Plain is situated to the east of the Middle Ganga Plain, spanning across the eastern part of Bihar, all of Bengal, and a significant portion of Bangladesh.
• Boundaries: It is bordered by the Darjeeling Himalaya to the north, the Bay of Bengal to the south, the Chotanagpur Highlands to the west, and the Bangladesh border to the east.
• Important Features: This region is characterized by the formation of deltas, constituting approximately two-thirds of the plain. The Ganga and Brahmaputra rivers combine to create the largest delta globally on the coastal side, known as the Ganga-Brahmaputra Delta. Notably, this delta is renowned for its mangroves and the presence of the Royal Bengal Tiger.

The Brahmaputra Plain

The Brahmaputra Plain is a significant geographical region with distinct characteristics and features.

Geographical Features of Brahmaputra Valley

• The region is situated in the northeastern part of the country.
• Referred to as the Brahmaputra Valley, Assam Valley, or Assam Plain.
• Distinct from the Ganga Plain, surrounded by various geographical features:
  • Eastern Himalayas of Arunachal Pradesh to the north.
  • Patkai Bum and Naga Hills in the east.
  • Garo-Khasi-Jaintia and Mikir Hills in the south.
  • Indo-Bangladesh border and lower Ganga Plain boundary in the west.
• Similar to the Ganga Plain, it is an aggradational plain formed by the Brahmaputra and its tributaries.
• Distinct riverine features due to the abrupt debouching of Brahmaputra tributaries:
  • Formation of alluvial fans, sandbars, river meanders, and oxbow lakes.
  • Majuli Island, created by the Brahmaputra, is the world's largest riverine island.
• Renowned for its sprawling tea plantations.

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Geomorphology of the Indo-Gangetic Plains

Geomorphology of the Indo-Gangetic Plains encompasses various unique features:

The Bhabar

• The Bhabar is a narrow belt, approximately 8-16 km wide, extending east to west, marking the northern boundary of the Great Northern Plains.
• It runs along the foothills of the Shiwaliks, spanning from the River Indus to the River Tista.
• This zone comprises alluvial fans formed by the deposition of unsorted sediments like gravel and pebble-studded rocks.
• Due to the porous nature of the sediments, water streams tend to sink and flow underground, resulting in dry river courses outside the monsoon season.

The Tarai

• The Tarai lies to the south of the Bhabhar region and runs parallel to it.
• It has a width ranging from 15-30 km.
• The streams that were underground in the Bhabhar region come up in this area, creating marshy and damp lands.
• The Tarai is made up of relatively finer alluvium and is mostly covered by forests.
• Much of the Tarai region has been converted into agricultural land, notably in states like Punjab, Uttar Pradesh, and Uttarakhand.

The Khadar

• The Khadar region is the floodplain area situated next to a river.
• It is enriched with fresh alluvium deposits carried by the river during floods, making it highly fertile.
• Khadar regions are known for their suitability for agriculture due to the nutrient-rich soil.
• The periodic flooding of rivers in the Khadar area helps in replenishing the soil with essential minerals.

The Bhangar (or Bangar)

• The Bhangar refers to an alluvial terrace situated above the flood plain level, predominantly found in the vast Indo-Gangetic Plains.
• Comprising older alluvium, this region's soil isn't regularly replenished, resulting in lower fertility levels.
• It contains calcareous deposits, locally termed as Kankar, further influencing its agricultural productivity.

Reh or Kallar

• Reh or Kallar are barren saline efflorescences found in the dry regions of Uttar Pradesh and Haryana.

Bhur

• Bhur refers to elevated land formations along the banks of the Ganga river, created by the accumulation of wind-blown sand during hot and dry months.

Significance of the Indo-Gangetic Plains

•  Home to a Large Population:  The plains cover less than one-third of the country's total area but accommodate over 40% of its population.
•  Agricultural Hub:  The region's fertile alluvial soils, flat terrain, slow-moving perennial rivers, and favorable climate support intensive agricultural practices. This area is often referred to as the granary of the nation.
•  Infrastructure Development:  The Indo-Gangetic Plains boast a well-developed network of roads and railways due to the easy topography, fostering urbanization and industrial growth.
•  Religious and Cultural Importance:  This region is significant for its numerous religious sites situated along the banks of revered rivers like the Ganga and Yamuna.

The Indo-Gangetic Plains, beyond being a geographical entity, represent the historical foundation of Indian civilization. These fertile lands have sustained the Indian populace for generations. In recent times, challenges such as decreasing soil fertility, water scarcity, and rapid population growth threaten the region. Ensuring the sustainability of the Great Northern Plains of India is not only vital for the subcontinent but also for the global ecological and cultural heritage. Embracing sustainable development practices is imperative for the region's future.

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