Drainage Class 9 ||Geography|| Chapter 3 NCERT Notes

Drainage Class 9 ||Geography|| Chapter 3 NCERT Notes

  1. Drainage Basin and Water Divide:
    • Drainage Basin: The area drained by a single river system, including its tributaries, is known as a drainage basin. For example, the Ganga basin is the area drained by the Ganga River and its tributaries.
    • Water Divide: A higher land area, such as a ridge or mountain, that separates two drainage basins. Water from one side of the divide flows into one basin, while water on the other side flows into another basin. The Western Ghats, for instance, form a divide between rivers flowing towards the Arabian Sea and those flowing towards the Bay of Bengal.

Drainage Systems of India:

India’s drainage system is classified into two major categories:

  1. Himalayan Rivers
  2. Peninsular Rivers

1. The Himalayan Rivers:

Himalayan rivers are perennial, meaning they have water throughout the year due to melting glaciers and rainfall. These rivers flow across the Northern Plains of India.

  • Characteristics of Himalayan Rivers:
    • They originate from the snow-covered peaks of the Himalayas.
    • They have large basins and long courses.
    • These rivers are involved in the process of erosion in their upper course, transportation in the middle course, and deposition in their lower course.
    • Himalayan rivers form meanders, oxbow lakes, and deltas.

Major Himalayan River Systems:

a. The Indus River System:

  • Originates in Tibet near Lake Mansarovar.
  • Enters India in the Ladakh region and flows through Pakistan into the Arabian Sea.
  • Major tributaries: Jhelum, Chenab, Ravi, Beas, Sutlej.
  • India utilizes 20% of the Indus water under the Indus Water Treaty (1960).

b. The Ganga River System:

  • Originates from the Gangotri Glacier in the Uttarakhand region.
  • Known as the Bhagirathi in its upper course, it meets the Alaknanda at Devprayag to form the Ganga.
  • Flows through the Northern Plains and empties into the Bay of Bengal.
  • Major tributaries: Yamuna, Ghaghara, Gandak, Kosi (from the north); Chambal, Betwa, Son (from the south).
  • Forms the largest delta in the world, the Sundarbans Delta.

c. The Brahmaputra River System:

  • Originates in Tibet, where it is called the Tsangpo, and flows eastward parallel to the Himalayas.
  • Takes a U-turn at Namcha Barwa and enters India in Arunachal Pradesh as the Dihang River.
  • Flows through Assam and Bangladesh, where it joins the Ganga River to form the world's largest delta.
  • The Brahmaputra is prone to flooding due to its high sediment load.

2. The Peninsular Rivers:

Peninsular rivers are seasonal, depending largely on rainfall. They are characterized by shorter and shallower courses compared to the Himalayan rivers. Most of these rivers flow eastward into the Bay of Bengal, though a few flow westward into the Arabian Sea.

  • Characteristics of Peninsular Rivers:
    • They originate from the Western Ghats or the Central Highlands.
    • They flow in well-defined channels and have relatively shorter courses.
    • Peninsular rivers do not form meanders or deltas as prominently as Himalayan rivers, though some like the Godavari and Mahanadi do.

Major Peninsular River Systems:

a. The Narmada River:

  • Originates from the Amarkantak hills in Madhya Pradesh.
  • Flows westward through a rift valley between the Vindhya and Satpura ranges.
  • Empties into the Arabian Sea near the Gulf of Khambhat.
  • Forms estuaries instead of deltas.

b. The Tapi River:

  • Originates in Madhya Pradesh.
  • Flows westward, parallel to the Narmada, and also forms an estuary at the Gulf of Khambhat.
  • The Tapi and Narmada are the only two major rivers flowing westward.

c. The Godavari River:

  • Known as the Dakshin Ganga (Ganga of the South), the Godavari is the largest river in peninsular India.
  • Originates from the Western Ghats in Maharashtra.
  • Flows eastward across the Deccan Plateau and empties into the Bay of Bengal.
  • Major tributaries: Purna, Wardha, Pranhita, Manjra, Penganga.

d. The Krishna River:

  • Originates near Mahabaleshwar in Maharashtra.
  • Flows eastward, passing through Karnataka and Andhra Pradesh before entering the Bay of Bengal.
  • Major tributaries: Bhima, Tungabhadra, Koyna.

e. The Mahanadi River:

  • Originates in Chhattisgarh.
  • Flows through Odisha and enters the Bay of Bengal.
  • The Mahanadi forms a large delta on the east coast.

f. The Kaveri River:

  • Originates in the Western Ghats of Karnataka.
  • Flows through Tamil Nadu and empties into the Bay of Bengal.
  • It forms a delta at its mouth, known for its fertile alluvial soil.

Lakes:

India also has a rich variety of lakes that contribute to the drainage system. They are classified into various types:

  1. Freshwater Lakes:

    • Located mainly in the Himalayan region.
    • Examples: Dal Lake (Kashmir), Wular Lake (Jammu and Kashmir, the largest freshwater lake).

  2. Saltwater Lakes:

    • Found mostly in arid regions.
    • Examples: Sambhar Lake (Rajasthan), which is India's largest inland saltwater lake.

  3. Artificial Lakes:

    • Man-made lakes, mostly created for irrigation, hydropower, or water supply.
    • Example: Gobind Sagar (Bhakra Nangal Dam).

Role of Rivers in the Economy:

  1. Agriculture:

    • Rivers provide water for irrigation, supporting the cultivation of crops like rice, wheat, and sugarcane.

  2. Hydroelectric Power:

    • Many rivers have been harnessed for hydroelectricity, which is a key source of renewable energy in India.

  3. Transportation:

    • Rivers serve as natural waterways, facilitating the movement of goods and people, particularly in the Ganga-Brahmaputra basin.

  4. Fisheries:

    • River systems and lakes are crucial for freshwater fisheries, which support the livelihood of many communities.

River Pollution:

While rivers are crucial for the economy and ecology, they are often subjected to severe pollution due to industrial waste, agricultural runoff, and untreated sewage. The Ganga and Yamuna are among the most polluted rivers in the world, despite being culturally significant.

Conservation Efforts:

  1. National Mission for Clean Ganga (NMCG):
    An initiative aimed at reducing pollution and revitalizing the Ganga River.

  2. Watershed Management:
    Efforts to conserve soil and water resources, particularly in the upper reaches of river basins, to prevent degradation of the environment.

Conclusion:

India’s diverse river systems are essential for its geography, culture, economy, and ecology. They not only shape the physical landscape but also support millions of livelihoods across the country. However, the challenge remains to protect and preserve these vital water resources from overuse and pollution to ensure sustainable development.