Class 9 Geography Chapter 3 Notes - Drainage

Introduction

The term "drainage" refers to the river system within a specific area. On a physical map, the convergence of small streams from various directions is evident, forming the main river that eventually empties into a larger water body, such as a lake, sea, or ocean. The region drained by a single river system is termed a "drainage basin." A detailed map examination reveals that elevated features, such as mountains or uplands, act as dividers between two distinct drainage basins.  

Types of Drainage Patterns

Drainage System in India

The Drainage systems of India are mainly controlled by the broad relief features of the subcontinent. accordingly, the Indian rivers are divided into two major groups:

(i) The Himalayan Rivers and                                                  
(ii) The Peninsular Rivers.

The Himalayan Rivers

The major Himalayan Rivers are the Indus, the Ganga and the Brahmaputra. These rivers are long and are joined by many large and important tributaries.

1. The Indus River System

• The river Indus rises in Tibet, near Lake Mansarovar. 
• Flowing west, it enters India in the Ladakh district of Jammu and Kashmir. Several tributaries, the Zaskar, the Nubra, the Shyok and the Hunza, Join it in the Kashmir region. 
• The Indus flows through Baltistan and Gilgit and emerges from the mountains at Attock. 
• The  Satluj, the Beas, the Ravi, the Chenab and the Jhelum join together to enter the Indus near Mithankot in Pakistan. 
• Beyond this, the Indus flows southwards eventually reaching the Arabian Sea, east of Karachi.
• With a total length of 2900 km, the Indus is one of the longest rivers in the world. a little over a third of the Indus Basin is located in India in the states of Jammu and Kashmir, Himachal Pradesh, and Punjab and the rest are in Pakistan.

2. The Ganga System

• The headwaters of the Ganga called the ‘Bhagirathi' is fed by the Gangotri Glacier and Joined by the Alaknanda at Devprayag in Uttaranchal. At Haridwar, the Ganga emerges from the mountains onto the plains.
• The Ganga is joined by the many tributaries from the Himalayas such as the Yamuna, the Ghaghara, the Gandak and the Kosi. The river Yamuna rises from the Yamunotri Glacier in the Himalayas and meets the Ganga at Allahabad. The Ghaghara, the Gandak and the Kosi rise in the Nepal Himalaya.
• The main tributaries from the peninsular uplands are the Chambal, the Betwa and the Son.
• The Ganga flows eastwards till Farakka in West Bengal, the northernmost point of the Ganga delta. The river bifurcates here; the Bhagirathi-Hooghly flows southwards through the deltaic plains to the Bay of Bengal. The mainstream flows southwards into Bangladesh and is joined by the Brahmaputra. Further downstream, it is known as the Meghna and finally flows into the Bay of Bengal. The delta formed by these rivers is known as the Sunderban Delta.
  
  Ganga River System and Brahmaputra River System

3. The Brahmaputra System

• The Brahmaputra rises in Tibet east of Mansarovar Lake. It is slightly longer than the Indus. It flows eastwards parallel to the Himalayas.
• On reaching the Namcha Barwa (7757 m), it takes a ‘U’ turn and enters India in Arunachal Pradesh through a gorge. Here, it is called the Dihang and it is joined by the Dibang, the Lohit, the Kenula and many other tributaries to form the Brahmaputra in Assam.
• In India, it passes through a region of high rainfall. Here the river carries a large volume of water and a considerable amount of silt. The Brahmaputra has a braided channel in its entire length in Assam and forms many riverine islands (Majuli, in the Brahmaputra River, is the largest inhabited riverine island in the world).
• During the rainy season, the river overflows its banks, causing widespread devastation due to floods in Assam and Bangladesh. Unlike other north Indian rivers, the Brahmaputra is marked by huge deposits of silt on its bed causing the river bed to rise. The river also shifts its channel frequently.

The Peninsular Rivers

4. The Mahanadi Basin

• The Mahanadi rises near Sihawa in the Raipur district of Chattisgarh and runs through Orissa to discharge its water into the Bay of Bengal. 
• Fifty-three percent of the drainage basin of this river lies in Madhya Pradesh and Chattisgarh, while 47 percent lies in Orissa.

5. The Krishna Basin

• The Krishna is the second-largest east-flowing peninsular river which rises near Mahabaleshwar in Sahyadri. 
• Its total length is 1,401 km. the Koyna, the Tungbhadra, and the Bhima are its major tributaries. 

6. The Kaveri Basin

• The Kaveri rises in Brahmagiri hills (3,341m) of Kogadu district in Karnataka. 
• Since the upper catchment area receives rainfall during the southwest monsoon season (summer) and the lower part during the northeast monsoon season (winter), the river carries water throughout the year with comparatively less fluctuation than the other Peninsular rivers. 
• Its important tributaries are the Kabini, the Bhavani and the Amravati.

  

   

Lakes

• Sambhar Lake is the largest inland salt lake in India situated in Rajasthan. Other salt lakes in Rajasthan are Didwana, Degana, Pachadra, Kucha man, and Lunkaransar.
• Lunar Lake situated in Maharashtra is a crater lake.
• Chilka Lake situated in the Puri district of Orissa & south of the Mahanadi delta is the biggest lake in the country.

Loktak Lake 

• Kolleru Lake is a deltaic Lake of Andhra Pradesh situated between the Krishna & Godavari delta.
• Pulicat Lake situated in the north of Chennai is a shallow lagoon. it has been barred by a long sandpit which is actually Sri Harikota island.
• Loktak Lake situated in Manipur is the largest freshwater lake in North East India. Keibul lamjao, the only floating National Park of the country is situated here.
• Vembanad Lake is a lagoon in Kerala and is an important tourist spot. coconut islands are located in it.
• Gohna Lake situated near Devprayag in Garhwal has been formed by a huge landslide across a tributary of the Ganga.
• Wular Lake & Dal Lake are tectonic lakes formed by faulting activities.

Importance of Lakes

• Lakes are vital for regulating rivers, preventing floods in heavy rainfall, and ensuring a steady water flow during dry spells. 
• They serve as sources of hydropower, and freshwater, and contribute to climate moderation. 
• Lakes also support diverse ecosystems, enhance natural beauty, and provide recreational opportunities, making them indispensable and multifunctional components of the environment.

Role of Rivers in Economy

• Rivers have formed fertile northern plains and deltas containing alluvial soils, India's most productive agricultural lands.
• Water from rivers is a basic natural resource essential for the survival of humans, plants and animals, for agricultural and industrial activities.
• The banks of rivers have been cradles of civilization all over the world. For example Indus civilization in India.
• Rivers have provided cultural and economic progress since ancient times.
• Rivers provide an inland transportation system. They also dilute and transport wastes from settlements.
• Industrial development has flourished along rivers. Most industrial processes depend on water as raw material, as a coolant, and for generating hydroelectricity.

River Pollution

Rapidly growing domestic, Municipal, industrial, and agricultural demand for water from rivers naturally affects the quality of water. Today more and more water is drained out of the rivers. It has resulted in reducing their volume. A heavy load of untreated sewage and industrial effluents is emptied into the rivers.

• This affects not only the quality of water but also the self-cleansing capacity of the river. For example, if there is adequate streamflow, the Ganga water is able to dilute and assimilate pollution loads of large cities within 20 km.
• The result is that the pollution level of many rivers is rising.
• Concern over the rising pollution of our rivers has launched of various action plants to clean the rivers.

National River Conservation Plan (NRCP)

• The Ganga Action Plan (GAP) Phase-I commenced in 1985 and concluded on March 31, 2000. 
• Following a review by the steering committee of the National River Conservation Authority, adjustments based on lessons learned were incorporated into the National River Conservation Program (NRCP). 
• GAP Phase-II has been integrated into the NRCP, which now encompasses 152 towns along 27 interstate rivers in 16 states. Pollution abatement initiatives are underway in 57 towns, with 215 schemes sanctioned. 
• Currently, 69 schemes have been successfully completed, aiming to intercept, divert, and treat one million liters of sewage.

For a detailed understanding of this chapter, check the video below.

Some Interesting Knowledge

• The world’s largest drainage basin is the River Amazon which is situated in South America.
• According to the regulation of the Indus Water Treaty (1960), India can use only 20 per cent of the total water carried by the Indus River system. This water is used for irrigation in the Punjab, Haryana, and the southern and western parts of Rajasthan.
• The Sundarban Delta derived its name from the Sundari tree which grows well in marshland. it is the world’s largest and fastest-growing delta. it is also the home of the Royal Bengal Tiger.
• The Brahmaputra is known as the Tsang Po in Tibet and Jamuna in Bangladesh.
• The river Kaveri is the second biggest waterfall in India. it is known as Sivasmudram. the fall supplies hydroelectric power to Mysore, Bangalore, and the Kolar Gold Field.
• 71 percent of the world’s surface is covered with water, but 97 percent of that is saltwater. Of the 3 percent that is available as freshwater, three-quarters of it is trapped as ice.
• Lakes of large extent are called the seas, like the Caspian, the Dead, and the Arab seas.