Quick Revision Notes: Class 11 Geography

Chapter: Drainage System (अपवाह तंत्र)

1. Introduction & Basic Terms

• Drainage (अपवाह): The flow of water through well-defined channels.
• Drainage System (अपवाह तंत्र): The network of a river and its tributaries.
• Drainage Basin (अपवाह बेसिन): The area drained by a single river system.
• Watershed (जल-संभर): A small upland boundary (mountain or ridge) that separates two drainage basins.
• Water Divide (जल विभाजक): An elevated area, such as a mountain or an upland, that separates two drainage basins (e.g., the Western Ghats).

2. Drainage Patterns (अपवाह प्रतिरूप)

The geometric arrangement of streams in a region determines its drainage pattern:

1. Dendritic Pattern (वृक्षाकार प्रतिरूप): Resembles the branches of a tree (e.g., Rivers of the Northern Plains like Ganga, Brahmaputra).
2. Trellis Pattern (जालीनुमा प्रतिरूप): Primary tributaries flow parallel to each other, and secondary tributaries join them at right angles (e.g., Rivers in the Himalayan region).
3. Rectangular Pattern (आयताकार प्रतिरूप): A patterned stream bed that is heavily jointed, developing right-angled bends.
4. Radial Pattern (अरापजीवी / अपकेंद्रीय प्रतिरूप): Streams diverge from a central high point or dome in all directions (e.g., Amarkantak range rivers like Narmada and Son).
5. Centripetal Pattern (अभिसारी प्रतिरूप): Streams converge into a central depression or lake (e.g., Loktak Lake).

3. Classification of Indian Drainage Systems

Indian drainage is broadly classified on the basis of origin, nature, and size into two major groups:

A. The Himalayan Drainage (हिमालयी अपवाह तंत्र)

• Characteristics: Perennial rivers (fed by melting snow and rain), long courses, gorge formation, and meandering in plains.
• Major River Systems:
  1. Indus System (सिंधु नदी तंत्र):
     • Origin: Kailash range, Tibet (near Mansarovar Lake).
     • Major Tributaries (The Panjnad): Jhelum, Chenab, Ravi, Beas, and Satluj.
     • Flows into: Arabian Sea.
  2. Ganga System (गंगा नदी तंत्र):
     • Origin: Bhagirathi from Gangotri glacier (meets Alaknanda at Devprayag).
     • Major Tributaries: Yamuna, Ghaghara, Gandak, Kosi (Left/Right banks), Chambal, Betwa, Son.
     • Flows into: Bay of Bengal (forms Sundarbans Delta).
  3. Brahmaputra System (ब्रह्मपुत्र नदी तंत्र):
     • Origin: Chemayungdung glacier (Tibet, known as Tsangpo).
     • Enters India in Arunachal Pradesh as Dihang, then joins Dibang and Lohit.
     • Flows into: Bay of Bengal (forms delta along with Ganga).

B. The Peninsular Drainage (प्रायद्वीपीय अपवाह तंत्र)

• Characteristics: Older than Himalayan rivers, broad and shallow valleys, seasonal/non-perennial (rain-fed), fixed courses with little meandering.
• Major River Systems:
  1. Mahanadi: Rises in Sihawa (Chhattisgarh), flows into Bay of Bengal.
  2. Godavari (Dakshin Ganga): Largest Peninsular river. Rises in Nashik (Maharashtra), flows into Bay of Bengal.
  3. Krishna: Second largest East-flowing Peninsular river. Rises near Mahabaleshwar.
  4. Kaveri: Rises in Brahmagiri hills (Karnataka), flows through Tamil Nadu to Bay of Bengal (perennial to an extent due to both monsoons).
  5. Narmada: West-flowing river. Rises in Amarkantak plateau, flows through a rift valley between Vindhya and Satpura ranges, forms estuary.
  6. Tapti: West-flowing river. Rises in Betul district (Madhya Pradesh), flows into Arabian Sea.

4. Comparison: Himalayan vs. Peninsular Rivers

5. Important Terms & Concepts to Remember

• River Regime (नदी का जल-प्रवाह पैटर्न): The pattern of flow of water in a river channel over a year.
• Catchment Area (जलग्रहण क्षेत्र): The area from which rainfall flows into a river or lake.
• Estuary (ज्वारनदमुख): Tidal mouth of a large river, where the tide meets the stream (formed by Narmada and Tapti).
• Delta (डेल्टा): A wetland that forms as a river empties its water and sediment into another body of water.