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Summary
Geography Class 38

DISCUSSION ON THE UPSC 2023 PRELIMS PAPER (5:16 PM)

DISCUSSION ON THE PREVIOUS CLASS (5:44 PM)

DRAINAGE SYSTEM OF INDIA (5:49 PM)

  • The drainage system of India is mainly divided into Himalayan rivers and Peninsular rivers.
  • Evolution of Himalayan Drainage System(5:55 PM)
  • Widely accepted theory regarding the evolution of Himalayan drainage proposes the existence of a single river all along the entire stretch of Himalayas to the south of Shivaliks flowing from East to West called Indobrahma or Shivalik River.
  • It drained into the Gulf of Sindh.
  • The earlier drainage system was disturbed by three main events:
  • (a) Higher upliftment of the western Himalayas.
  • (b) Rising of Potwar plateau and Delhi ridge.
  • (c) Downthursting of Malda gap or Garo-Rajmahal gap.
  • This divided the entire river into Indus and its tributaries, Ganga and its tributaries, and the Brahmaputra and its tributaries.
  • Peninsular Drainage System (6:08 PM)
  • The peninsular drainage system is influenced by three major events:
  • (a) Submergence of the western side of the western ghats which disturbed the earlier symmetrical pattern of peninsular drainage and shortened the west-flowing rivers.
  • (b) Upliftment of the Himalayas which caused the northern part of the Vindhyas to tilt more towards the north and also the deepening of the rift valley of Narmada and Tapi.
  • (c) Slight tilting of the peninsular block from northwest to southeast direction, causing the slope towards the Bay of Bengal drainage.
  • Difference between Himalayan and Peninsular Drainage (6:26 PM)
  • Himalayan Drainage Peninsular Drainage
    The source of the drainage is glaciers.  The source of the drainage is rainfall. 
    The Himalayan drainage is perennial.  The Peninsular Rivers are seasonal. 
    The Himalayan rivers are dominated by the youth stage.  The Peninsular rivers are dominated by mature and old stages. 
    They form V-shaped valleys.  They formed U-shaped valleys. 
    They have high meandering. (High meandering due to high sediments and flowing through plain regions.)  These have low meandering. (Low meandering due to lower sediments and flowing through plateau region.) 
    These have larger river basins and a catchment area.  These have smaller river basins and a catchment area. 
    The deltas of the Himalayan rivers are very large. 

    The deltas present are small. Some rivers just have estuaries. 
    Himalayan rivers are more navigable in the plains. 

    These are less navigable. 
    The Himalayan drainage has many antecedent rivers. 

    In Peninsular drainage, there are only consequent rivers. 
    The drainage pattern is mainly dendritic. 

    The drainage pattern is mainly rectangular or trellis. 
  • Examples of antecedent rivers are Indus, Brahmaputra, Sutlej, Ghagra, Gandak, and Kosi. Ganga and Yamuna are the consequent rivers.

DRAINAGE PATTERNS (7:06 PM)

  • The flow characteristic of a river is called a drainage pattern.
  • (a) Dendritic Pattern
  • It appears like the branches of a tree or a leaf.
  • This is characterized by the lack of structural control.
  • This is found in the Himalayan rivers. For example, the Ganga drainage pattern.
  • (b) Rectangular Pattern
  • The river takes sharp turns.
  • It is found in the plateau regions with high structural control. 
  • This is found in the case of the peninsular rivers. For example, the River Mahanadi, Godavari, Cauvery, etc. follows this drainage pattern.
  • (c) Trellis pattern
  • The main river flows in the rift valley and tributaries join at the right angle.
  • This is possible when the river flows in the rift valley. For example, the Narmada and Tapi Rivers follow this drainage pattern.
  • (d) Radial Pattern
  • In this, the different rivers originate from the raised platform or mountain and flow in various directions.
  • For example, from Amarkantak we have the Narmada, Son, and Hasdeo rivers originate.
  • (e) Parallel Drainage
  • The rivers flow parallel to each other and drain directly into the sea.
  • For example, West flowing rivers of the western ghats.

MAPPING OF THE RIVERS (7:28 PM)

  • (a) Indus River System
  • Indus flows through three countries namely China, Pakistan, and India.
  • It originates near Mansarovar Lake.
  • The right bank tributaries are Shyok, Gilgit, and Kabul.
  • The left bank tributaries are Jhelum, Chenab, Sutlej, Ravi, and Beas.
  • Nubra is the tributary of River Shyok. It comes from the Siachen glacier.
  • (b) Jhelum
  • Jhelum originates from Verinag.
  • It flows through the Jhelum River valley called Kashmir Valley.
  • It passes through Wular Lake. It is the largest freshwater lake in India.
  • Jhelum River meanders while it is flowing through Kashmir. It is the only river that meanders in the youth stage.
  • In Pakistan, Jhelum merges with Chenab.
  • (c) Chenab
  • It originates near Bara Lacha La.
  • Chenab formed after the confluence of the Chandra and Bhaga rivers.
  • Chandra originates from the Chandra tal.
  • Bhaga originates from the Suraj tal.
  • Barashigri glacier feeds the Chander tal.
  • (d) Ravi
  • It originates from the Kullu Hills.
  • In ancient times it was called the Parushni River.
  • It forms the natural boundary between India and Pakistan along the northern part of Punjab.
  • (e) Beas
  • It originates from the Rohtang.
  • It lies completely inside India.
  • It merges with Sutlej in Punjab.
  • (f) Sutlej
  • It originates from Lake Rakas. Its water is salty.
  • Sutlej and Beas merge in Harikke.

THE TOPIC FOR THE NEXT CLASS: DRAINAGE SYSTEM OF INDIA (CONTINUED)