The Drainage System of India

For any aspirant of Indian Geography (UPSC/CGL), the Drainage System is the backbone of the syllabus. It is not just about memorizing names; it is about understanding the lifeline of India's agriculture and economy.

Broadly, the Indian drainage system is divided into two distinct groups based on their origin:

1. The Himalayan Rivers (Perennial, snow-fed).
2. The Peninsular Rivers (Seasonal, rain-fed).

THE WATER DIVIDE The Aravalli Range and the elevated land near Ambala act as the "Water Divide" separating the Indus system (flowing West) from the Ganga system (flowing East).

1. The Himalayan River System

These rivers originate from the glaciers of the Himalayas. They are young, energetic, and cut deep gorges. They carry huge silt and form massive deltas.

A. The Indus System

• Origin: Near Lake Mansarovar (Tibet).
• Length: 2,880 km (One of the longest in the world).
• Key Tributaries (The Panjnad): Jhelum, Chenab (Largest), Ravi, Beas, and Sutlej.

Exam Trap: The Indus flows between the Ladakh and Zaskar ranges. It enters Pakistan near Chillar.

B. The Ganga System (Largest in India)

The Ganga is not just one river; it is a result of a confluence. It originates as the Bhagirathi from the Gangotri Glacier.

THE FORMATION OF GANGA (At Devprayag)

Alaknanda River

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Bhagirathi River

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GANGA

• Left Bank Tributaries: Gomti, Ghaghara, Gandak, Kosi (Sorrow of Bihar).
• Right Bank Tributaries: Yamuna (Longest tributary), Son.
• Endpoint: Meets Brahmaputra (called Padma in Bangladesh) -> Forms Sunderbans Delta -> Bay of Bengal.

C. The Brahmaputra System

Known by many names, this river creates the world's largest riverine island (Majuli) in Assam.

• Tibet: Yarlung Tsangpo
• Arunachal Pradesh: Dihang
• Assam: Brahmaputra
• Bangladesh: Jamuna

2. The Peninsular River System

These rivers are older than the Himalayas. Their valleys are broad and shallow. They are rain-fed, meaning they can dry up in summer.

A. West Flowing Rivers (Into Arabian Sea)

These rivers flow against the general slope of the plateau because they flow through Rift Valleys.

• Narmada: Originates at Amarkantak Plateau. Flows between Vindhya and Satpura ranges. Creates "Marble Rocks" gorge near Jabalpur.
• Tapti: Originates in Betul district (MP). known as the "Twin" or "Handmaid" of Narmada.
• Mahi: The only river in India that cuts the Tropic of Cancer twice.

ESTUARIES vs DELTAS West flowing rivers do NOT form deltas because they have a short course and flow through hard rocks (less silt). Instead, they form Estuaries.

B. East Flowing Rivers (Into Bay of Bengal)

These rivers form the "Rice Bowl" of India due to their fertile deltas.

• Godavari: The largest Peninsular river.
  Nicknames: Dakshin Ganga, Vridha Ganga.
  Origin: Nasik (Trimbakeshwar).
• Krishna: Originates at Mahabaleshwar.
  Dispute: The Almatti Dam is a major source of conflict between Karnataka and Andhra.
• Cauvery (Kaveri): The only peninsular river that flows almost all year round (receives rain from both SW and NE monsoons).
  Waterfall: Shivasamudram Falls.

Comparison: Himalayan vs. Peninsular

Feature	Himalayan Rivers	Peninsular Rivers
Nature	Perennial (Snow + Rain)	Seasonal (Rain only)
Age	Young, Active (Erosion)	Old, Stable
Path	Meandering (Curvy)	Straight / Fixed
Mouth	Big Deltas	Deltas (East) / Estuaries (West)

Quick Revision Flashcards

"Sorrow of Bihar"

Which river changes its course frequently?

River Kosi

It brings massive sediment from Nepal, clogs its own path, and floods vast areas.

Dakshin Ganga

Is it Godavari or Cauvery?

Godavari

Godavari is "Dakshin Ganga" (South Ganga) due to size.
Cauvery is "Ganga of the South" due to holiness.

Majuli Island

Located in which state?

Assam

Formed by the Brahmaputra river. It is the first island district of India.

Rift Valleys

Which two major rivers flow in rift valleys?

Narmada & Tapti

This is why they flow West, unlike most other Indian rivers.

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