The Drainage System of India

The flow of water through well-defined channels is known as ‘drainage’ and the network of such channels is called a ‘drainage system’. The drainage pattern of an area is the outcome of the geological time period, nature and structure of rocks, topography, slope, and amount of water flowing.

1. Classification of Indian Drainage

Indian drainage can be divided based on various factors:

• On the Basis of Discharge of Water:
  • Arabian Sea Drainage: (approx 23%) Rivers like Indus, Narmada, Tapi.
  • Bay of Bengal Drainage: (approx 77%) Rivers like Ganga, Brahmaputra, Mahanadi, Godavari, Krishna.
• On the Basis of Size of Catchment Area:
  • Major: Area > 20,000 sq km (14 basins).
  • Medium: Area between 2,000 to 20,000 sq km (44 basins).
  • Minor: Area < 2,000 sq km.

2. The Himalayan Drainage System

These are perennial rivers fed by both melting snow and rain. They have long courses and pass through deep V-shaped gorges.

A. The Indus System

• Origin: Near Mansarovar Lake (Tibet) at Sen-ge-Zangbo or Lion's Mouth.
• Tributaries: Jhelum, Chenab (Largest tributary), Ravi, Beas, Satluj (Panchnad).
• Indus Water Treaty (1960): India can use 20% of the total water (on Western rivers: Indus, Jhelum, Chenab).

B. The Ganga System

• Origin: Gangotri Glacier (Gaumukh) as Bhagirathi. It becomes Ganga after meeting Alaknanda at Devprayag.
• Tributaries:
  • Left Bank: Ramganga, Gomti, Ghaghara, Gandak, Kosi (Sorrow of Bihar).
  • Right Bank: Yamuna (largest), Son.
• Yamuna: Originates from Yamunotri. Meets Ganga at Prayagraj (Sangam).

C. The Brahmaputra System

• Origin: Chemayungdung Glacier near Mansarovar (Tibet) where it is called Tsangpo.
• Course: Enters India in Arunachal Pradesh as Dihang. In Bangladesh, it is called Jamuna and joins Padma (Ganga) to form the world's largest delta, Sunderbans.

3. The Peninsular Drainage System

These are seasonal rivers (non-perennial) with shorter courses.

A. West Flowing Rivers (Arabian Sea)

• Narmada: Rising in Amarkantak, flows through a Rift Valley between Vindhyas and Satpuras. Forms Dhuandhar Falls.
• Tapi: Rising in Betul (MP), also flows in a Rift Valley.
• Other Rivers: Luni (inland drainage), Mahi (crosses Tropic of Cancer twice), Sabarmati.

B. East Flowing Rivers (Bay of Bengal)

• Mahanadi: Rises in Chhattisgarh, Hirakud dam is built on it.
• Godavari: Longest river of Peninsular India (Dakshin Ganga). Rises in Trimbakeshwar (Nasik).
• Krishna: Rises near Mahabaleshwar.
• Cauvery: Rises in Brahmagiri hills (Karnataka), flows throughout the year due to North-East monsoon in winter.

4. Watershed Management

The rational utilization of land and water resources for optimum production with minimum hazard to natural resources. Success stories like Ralegan Siddhi (Anna Hazare) demonstrate its potential for rural upliftment.