DRAINAGE

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Introduction

• The term “drainage” refers to the river system within a particular geographic area.
• The area that is drained by a single river system is known as a drainage basin.
• The boundaries of a drainage basin are often referred to as water divides or watershed divides.
• A water divide is an elevated land feature, such as a hill, ridge, or mountain, that separates the drainage of one river system from another.

Indian Rivers

• Indian rivers are classified as:
  • Himalayan Rivers 
  • Peninsular Rivers
• Himalayan Rivers:
  • These are perennial rivers. 
  • Receive water from both rain and melted snow from the glaciers.
  • These rivers have a long course. 
  • They form meanders, oxbow lakes and other landforms.
• Peninsular Rivers:
  • These are seasonal rivers, and their flow is dependent on rain.  
  • They have shorter and shallower course. 
  • Most of these originate in western ghats and drain into the bay of Bengal.

Drainage Patterns

• There are four types of drainage patterns shown by rivers:
  • Dendritic Drainage 
  • Trellis Drainage
  • Rectangular Drainage 
  • Radial Drainage 

Dendritic Drainage

• Dendritic drainage patterns resemble the branching of tree roots or leaf veins.
• They occur in regions with uniform geology and gentle slopes.
• Water follows the path of least resistance, eroding channels and forming a branching network.
• The main channel collects water from smaller tributaries at acute angles.
• They are associated with mature river systems that have undergone extensive erosion.
• Examples include the Mississippi River system and the Ganges-Brahmaputra system.

Trellis Drainage

• Parallel main channels with tributaries at right angles.
• Found in folded or tilted rock regions.
• Main channels follow fold axes or structural weaknesses.
• Seen in eroded landscapes with tectonic activity.
• Examples: Appalachian Mountains, North Caucasus.

Rectangle Drainage

• Straight channels intersect at right angles.
• Develop in regions with jointed or faulted rock structures.
• Channels align with rock joints or faults.
• Examples: Colorado Plateau, United States.

Radial Drainage

• Rivers and streams flow outward from a central point.
• Common in volcanic or mountain regions.
• Water follows slopes like spokes on a wheel.
• Central point corresponds to the highest point.
• Efficiently drains water in multiple directions.
• Examples: Mount Rainier, Washington, USA.

Himalayan Rivers

• Originating from the Himalayas, a high mountain range.
• Fed by melting snow and glaciers.
• Major rivers include Ganges, Brahmaputra, Indus, Yamuna, Sutlej, Chenab, and Kosi.
• Provide water for agriculture and hydropower.
• Shape the geography and culture of the region.
• Support diverse ecosystems and wildlife.
• Face challenges such as pollution and climate change impacts.

The Indus River System

• Length: Approximately 2,900 km (1,800 miles).
• Origin: Southern slopes of the Kailash Mountain Range in the Tibetan Plateau.
• Major Tributaries: Jhelum, Chenab, Ravi, Beas, and Sutlej rivers.
• Historical significance: Cradle of the ancient Indus Valley Civilization.
• Water resource: Vital for agriculture in Punjab and Sindh.
• Enables irrigation for crops like wheat, rice, cotton, and sugarcane.

The Ganga River System

• The Ganga originates from the Gangotri Glacier. It originates as Bhagirathi. 
• Major Tributaries:
  • Alaknanda – Joins Bhagirathi at Devprayag. The river is called Ganga from there on.
  • Yamuna – it is the longest tributary in India, length: 1385 km, joins Ganga at Prayag Raj. 
  • Ghagra, Kosi and Gandak originate in the Nepal Himalayas and joins the Ganga from the northern side. 
  • Chambal, Son and Betwa join the Ganga from the south. 
• The Ganga bifurcates into Hooghly and Bhagirathi at Farakka in West Bengal.
• As the Ganga enters Bangladesh, it is called Padma.
• The total length of Ganga is 2510 km.
• The Sunderban Delta is formed  by the Ganga and Brahmaputra rivers. 

The Brahmaputra River System

• Origin: The Brahmaputra begins at Mansarovar lake in the Kailash range. Length – 2900 km 
• Tributaries: Major tributaries include Dibang and Lohit.
• Course: in Tibet, it flows eastward parallel to the Himalayas and takes a U-turn at Namcha Barwa. 
• Entry into India: It enters India through a gorge and is called Dihang.
• Riverine islands: Brahmaputra has numerous broad riverine islands.
• Majuli island is the biggest riverine island in India.

Peninsular Rivers

• Found in the peninsular region of India.
• Major rivers include Godavari, Krishna, Kaveri, Narmada, and Tapti.
• Shorter in length compared to Himalayan rivers.
• Originates from the Western Ghats and Central Highlands.
• Influenced by monsoon rains, with peak flow during monsoon season.
• Provide water for irrigation, hydroelectric power, and drinking water.

Narmada River System

• Size and Geography: Narmada is the largest west flowing river in the peninsular region, flowing through a rift valley between the Vindhya (north) and Satpura Range (south).
• Origin: It rises from the Maikala range near Amarkantak in Madhya Pradesh.
• Major Tributaries: Hiran, Orsang, Barna, and Kolar are significant tributaries of the river.
• Basin: The Narmada basin covers parts of Madhya Pradesh, Maharashtra, and Gujarat.

Tapi River System

• Origin: The Tapi River originates in Betul district of Madhya Pradesh, India.
• Course: It flows westward through Madhya Pradesh, Maharashtra, and Gujarat.
• Length and Tributaries: It has a length of approximately 724 km and is fed by tributaries such as Purna, Girna, Panzara, and Arunavati rivers.
• Basin: The Tapi River basin covers parts of Madhya Pradesh, Maharashtra, and Gujarat.
• Environmental significance: The Tapi River system is ecologically significant, supporting a variety of wildlife and bird species.

Mahanadi River

• Origin and Course: Mahanadi rises in Raipur district of Chhattisgarh and flows through Odisha before draining into the Bay of Bengal.
• Drainage Basin: 53% of its basin is in Madhya Pradesh and Chhattisgarh, while 47% lies in Odisha.
• Major Tributaries: The river is joined by tributaries like Seonath, Hasdeo, Mand, Ib, Jonking, and Tel rivers.
• Basin Boundaries: The basin is bordered by the Central India hills (north), Eastern Ghats (south and east), and Maikala range (west).

Godavari River

• Size and Name: Godavari is the largest Peninsular river system and is known as the “Dakshin Ganga.“
• Origin and Outflow: It rises in Maharashtra Nashik district and flows into the Bay of Bengal.
• Tributaries and States: Its tributaries pass through Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha, and Andhra Pradesh.
• Principal Tributaries: Notable tributaries include Penganga, Indravati, Pranhita, and Manjra.

Krishna River

• Course: Krishna River flows through the states of Maharashtra, Karnataka, and Andhra Pradesh.
• Origin and Outflow: It originates in the Western Ghats of Maharashtra and empties into the Bay of Bengal.
• Tributaries: The river is fed by numerous tributaries, including the Tungabhadra, Bhima, and Ghataprabha rivers.
• Importance: Krishna River is significant for irrigation, hydropower generation, and water supply for agriculture and drinking purposes.

Kaveri River

• Origin: Kaveri rises in the Brahmagiri hills of Kodagu district in Karnataka.
• Sacred River: It is a revered river in southern India.
• Major Tributaries: Important tributaries include Arkavathi, Hemavathi, Bhavani, Kabini, and Amravati.
• Course and Outflow: Kaveri flows southeast through Karnataka, Kerala, and Tamil Nadu before draining into the Bay of Bengal via Pondicherry.