Chapter: Drainage System

• Introduction

  • Drainage: Flow of water through well-defined channels
  • Drainage System: Network of small channels (streams)
  • Drainage Basin: Area drained by a single river system
  • Watershed: Ridge/boundary separating two drainage basins
  • Catchment Area: Source area supplying water to the river

• Drainage Patterns

  • Dendritic: Tree-like branch pattern (e.g., Northern plains)
  • Radial: Streams flow outward from a central peak (e.g., Amarkantak)
  • Trellis: Primary and secondary tributaries join at right angles (e.g., Himalayan valleys)
  • Centripetal: Streams discharge water into a central lake or depression (e.g., Loktak Lake)

• Classification of Indian Drainage

  • Evolutionary Basis
    • Himalayan Drainage: Antecedent, perennial, deep gorges
    • Peninsular Drainage: Superimposed, antecedent, seasonal, shallow valleys
  • Discharge Basis (Water Division)
    • Arabian Sea Drainage: ~23% (e.g., Narmada, Tapi)
    • Bay of Bengal Drainage: ~77% (e.g., Ganga, Brahmaputra)
  • Watershed Basis
    • Major River Basins (>20,000 sq. km)
    • Medium River Basins (2,000 - 20,000 sq. km)
    • Minor River Basins (<2,000 sq. km)

• The Himalayan River Systems

  • Indus System
    • Origin: Bokhar Chu glacier (Tibet)
    • Left Bank Tributaries: Zaskar, Chenab, Jhelum, Ravi, Beas, Satluj
    • Right Bank Tributaries: Shyok, Gilgit, Kabul
  • Ganga System
    • Origin: Gangotri glacier (as Bhagirathi), joins Alaknanda at Devprayag
    • Left Bank Tributaries: Ramganga, Gomti, Ghaghara, Gandak, Kosi
    • Right Bank Tributaries: Yamuna, Son, Damodar
    • Distributary: Hooghly; Mouth: Sundarbans Delta
  • Brahmaputra System
    • Origin: Chemaungdung glacier (Tibet, known as Tsangpo)
    • Enters India in Arunachal Pradesh as Dihang
    • Tributaries: Dibang, Lohit, Subansiri, Teesta
    • Forms world's largest riverine island: Majuli

• The Peninsular River Systems

  • Mahanadi: Originates in Sihawa (Chhattisgarh), flows to Bay of Bengal
  • Godavari (Dakshina Ganga)
    • Largest Peninsular river
    • Origin: Trimbakeshwar (Nasik)
    • Tributaries: Pranhita, Indravati, Manjira
  • Krishna
    • Origin: Mahabaleshwar
    • Tributaries: Koyna, Tungabhadra, Bhima
  • Cauvery
    • Origin: Brahmagiri hills (Karnataka)
    • Perennial nature due to both monsoons
  • West-Flowing Rivers
    • Narmada: Flows through rift valley between Vindhya and Satpura; forms Dhuandhar Falls
    • Tapi: Originates in Multai (Betul, MP)
    • Luni: Inland drainage, disappears in Rann of Kachchh

• River Regimes and Water Resources

  • River Regime: Pattern of flow of water in a river channel throughout the year
  • Himalayan Rivers: Perennial (fed by glaciers and monsoon)
  • Peninsular Rivers: Seasonal/Fluctuating (fed by rain only)
  • Water Utilization Issues
    • Uneven spatial and temporal distribution
    • Pollution from industrial and domestic waste
    • Inter-state water disputes (e.g., Cauvery, Krishna)

• Conservation and Management

  • River Conservation Programmes (e.g., Namami Gange, National River Conservation Plan)
  • Interlinking of Rivers: Proposed to transfer surplus water to deficit basins
  • Watershed Management: Rainwater harvesting, afforestation, check dams to conserve soil and water