Drainage System

• Definition: A network of rivers and their tributaries in a specific area.
• Drainage Basin: The area drained by a single river system.
• Water Divide: An elevated area or ridge that separates two drainage basins (e.g., Ambala separates the Indus and Ganga river systems).

Drainage Patterns

• Dendritic: Tree-like pattern where tributaries join the main river (e.g., Ganga River System).
• Trellis: Tributaries flow parallel to each other and join at right angles (e.g., rivers in the Narmada Valley).
• Radial: Streams radiate outward from a central point, often a hill or mountain (e.g., rivers originating from Amarkantak Plateau).
• Centripetal: Rivers flow inward towards a central depression or lake (e.g., rivers draining into Sambhar Lake).

River Systems of India

1. The Himalayan Rivers
   1. Characteristics:
      • Perennial (flow throughout the year).
      • Fed by glaciers and rainfall.
      • Known for erosional and depositional activities, forming valleys and fertile plains.
   2. Major River Systems:
      • Indus River System:
        • Origin: Mansarovar Lake, Tibet.
        • Length: 2,900 km (total), 1,114 km in India.
        • Drainage Area: Approximately 1.2 million sq. km (321,289 sq. km in India).
        • Tributaries: Jhelum, Chenab, Ravi, Beas, Sutlej.
        • Flows through India and Pakistan.
        • Significance: Allocated between India and Pakistan under the Indus Water Treaty (1960).
      • Ganga River System:
        • Origin: Gangotri Glacier (Bhagirathi merges with Alaknanda to form the Ganga).
        • Length: 2,525 km (total), 2,410 km in India.
        • Drainage Area: Over 1 million sq. km.
        • Tributaries: Yamuna, Ghaghara, Gandak, Kosi, Son, Chambal.
        • Delta: Ends in the Bay of Bengal, forming the Sundarbans Delta (largest delta in the world).
      • Brahmaputra River System:
        • Origin: Tibet (known as Tsangpo).
        • Length: 2,900 km (total), 916 km in India.
        • Drainage Area: Approximately 580,000 sq. km.
        • Enters India in Arunachal Pradesh, flows through Assam, and merges with the Ganga in Bangladesh.
        • Features: Prone to flooding, highly braided.
2. The Peninsular Rivers
   1. Characteristics:
      • Seasonal, dependent on monsoons.
      • Flow through older, hard rocks with low gradients.
      • Most rivers flow eastward into the Bay of Bengal, forming deltas; a few flow westward into the Arabian Sea, forming estuaries.
   2. Major River Systems:
      • Mahanadi River:
        • Origin: Chhattisgarh.
        • Length: 851 km.
        • Drainage Area: 141,589 sq. km.
      • Godavari River:
        • Known as: Dakshin Ganga (South Ganga).
        • Origin: Maharashtra.
        • Length: 1,465 km (longest river in Peninsular India).
        • Drainage Area: 312,812 sq. km.
      • Krishna River:
        • Origin: Maharashtra.
        • Length: 1,400 km.
        • Drainage Area: 258,948 sq. km.
      • Kaveri River:
        • Origin: Karnataka.
        • Length: 800 km.
        • Drainage Area: 81,155 sq. km.
      • Narmada and Tapi Rivers:
        • Flow westward into the Arabian Sea.
        • Narmada Length: 1,312 km
        • Tapi Length: 724 km
        • Drainage Area: Narmada – 98,796 sq. km; Tapi – 65,145 sq. km.
      • Other Rivers: Subarnarekha, Pennar, and Vaigai.

Lakes in India

• Types of Lakes:
  • Freshwater Lakes: Found in the Himalayas (e.g., Dal Lake, Wular Lake).
  • Saltwater Lakes: Found in arid and semi-arid regions (e.g., Sambhar Lake in Rajasthan).
  • Artificial Lakes: Created by damming rivers (e.g., Gobind Sagar on Bhakra Nangal Dam).
• Significance of Lakes:
  Source of freshwater.
  Support aquatic ecosystems.
  Help regulate river flow during floods.
  Promote tourism and recreation.

Importance of Rivers

• Economic Importance:
  • Provide water for irrigation, drinking, and industry.
  • Act as natural highways for transportation and trade.
  • Source of hydroelectric power.
• Cultural Importance:
  • Many rivers are considered sacred (e.g., Ganga, Yamuna).
  • Sites for pilgrimage and rituals.

Important Terms:

• Delta: A triangular landform created by river deposition at its mouth (e.g., Sundarbans Delta).
• Estuary: A funnel-shaped mouth of a river where tides meet river currents (e.g., Narmada).
• Inland Drainage: Rivers that do not reach the sea but drain into lakes or inland depressions (e.g., rivers in Rajasthan).