Drainage Class 9 Notes NCERT and MCQs
This chapter discusses the river system of India and other drainage patterns.
Drainage: The term drainage describes the river system of an area. Small streams flowing from different directions come together to form the main river, which ultimately drains into a large water body such as a lake or a sea or an ocean.
Drainage basin: The area drained by a single river system is called a drainage basin.
Water divide: Any elevated area, such as a mountain or an upland, separates two drainage basins. Such an upland is known as a water divide.
Drainage system of India is controlled by the relief features and accordingly, the Indian rivers are divided into two major groups:
The Himalayan Rivers
- Most of the Himalayan rivers are perennial and have water throughout the year.
- These rivers receive water from rain as well as from melted snow from the lofty mountains.
- The major Himalayan rivers are the Indus, the Ganga and the Brahmaputra.
- The Himalayan rivers have long courses from their source to the sea.
- They perform intensive erosional activity in their upper courses and carry huge loads of silt and sand.
- In the middle and the lower courses, these rivers form meanders, oxbow lakes, and many other depositional features in their floodplains. They also have well developed
Major river systems in this region are:
1. The Indus River System
2. The Ganga River System
3. The Brahmaputra River System
1. The Indus River System
- The river Indus rises in Tibet, near Lake Mansarovar. Flowing west, it enters India in Ladakh. It forms a picturesque gorge in this part.
- 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.
- The Indus plain has a very gentle slope.
- 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 Ladakh, Jammu and Kashmir, Himachal Pradesh and Punjab and the rest is in Pakistan.
2. The Ganga River System
- The headwaters of the Ganga- the ‘Bhagirathi’ (fed by the Gangotri Glacier) and Alaknanda- meet at Devaprayag in Uttarakhand. At Haridwar, the Ganga emerges from the mountains onto the plains.
- The Ganga is joined by many tributaries from the Himalayas, a few of them being major rivers, such as the Yamuna, the Ghaghara, the Gandak and the Kosi.
- The river Yamuna rises from the Yamunotri Glacier in the Himalayas. It flows parallel to the Ganga and as a right bank tributary meets the Ganga at Allahabad.
- The Ghaghara, the Gandak and the Kosi rise in the Nepal Himalaya. They are the rivers, which flood parts of the northern plains every year, causing widespread damage to life and property, but also enriching the soil for agricultural use.
- The main tributaries, which come from the peninsular uplands, are the Chambal, the Betwa and the Son. These rise from semi-arid areas, have shorter courses and do not carry much water in them.
- Enlarged with the waters from its right and left bank tributaries, the Ganga flows eastwards till Farakka in West Bengal. This is the northernmost point of the Ganga delta.
- The river bifurcates here; the Bhagirathi-Hooghly (a distributary) 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.
- This mighty river, with waters from the Ganga and the Brahmaputra, flows into the Bay of Bengal. The delta formed by these rivers is known as the Sundarbans Delta.
- The length of the Ganga is over 2500 km.
- Ambala is located on the water divide between the Indus and the Ganga river systems. The plains from Ambala to the Sundarbans stretch over nearly 1800 km, but the fall in its slope is hardly 300 m. Therefore, the river develops large meanders.
3. The Brahmaputra River System
- Brahmaputra is known as the Tsang Po in Tibet and Jamuna in Bangladesh.
- It rises in Tibet east of Mansarovar lake very close to the sources of the Indus and the Satluj.
- It is slightly longer than the Indus, and most of its course lies outside India. 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, and many other tributaries to form the Brahmaputra in Assam.
- In Tibet, the river carries a smaller volume of water and less silt as it is a cold and dry area.
- 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.
- The world’s largest riverine island is formed by the Brahmaputra, called Majuli Island.
- Every year 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 riverbed to rise. The river also shifts its channel frequently.
The Peninsular Rivers
- The main water divide in Peninsular India is formed by the Western Ghats, which runs from north to south close to the western coast.
- Most of the major rivers of the Peninsula, such as the Mahanadi, the Godavari, the Krishna and the Kaveri flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths.
- There are numerous small streams flowing west of the Western Ghats.
- The Narmada and the Tapi are the only long rivers, which flow west and make estuaries. These rivers flow through the troughs.
- The drainage basins of the peninsular rivers are comparatively smaller in size.
1. The Narmada Basin
- The Narmada rises in the Amarkantak hills in Madhya Pradesh. It flows towards the west in a rift valley formed due to faulting.
- On its way to the sea, the Narmada creates many picturesque locations. The ‘Marble rocks’, near Jabalpur, where the Narmada flows through a deep gorge, and the ‘Dhuadhar falls’, where the river plunges over steep rocks, are some of the notable ones.
- All tributaries of the Narmada are very short and most of these join the mainstream at right angles.
- The Narmada basin covers parts of Madhya Pradesh and Gujarat.
2. The Tapi Basin
- The Tapi rises in the Satpura ranges, in the Betul district of Madhya Pradesh.
- It also flows in a rift valley parallel to the Narmada but it is much shorter in length.
- Its basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.
- The coastal plains between Western Ghats and the Arabian Sea are very narrow. Hence, the coastal rivers are short.
- The main west flowing rivers are Sabarmati, Mahi, Bharathpuzha and Periyar.
3. The Godavari Basin
- The Godavari is the largest Peninsular river.
- It rises from the slopes of the Western Ghats in the Nasik district of Maharashtra. Its length is about 1500 km.
- It drains into the Bay of Bengal.
- Its drainage basin is also the largest among the peninsular rivers.
- The basin covers parts of Maharashtra (about 50 percent of the basin area lies in Maharashtra), Madhya Pradesh, Odisha and Andhra Pradesh.
- The Godavari is joined by a number of tributaries, such as the Purna, the Wardha, the Pranhita, the Manjra, the Wainganga and the Penganga. The last three tributaries are very large.
- Because of its length and the area it covers, it is also known as the Dakshin Ganga.
4. The Mahanadi Basin
- The Mahanadi rises in the highlands of Chhattisgarh.
- It flows through Odisha to reach the Bay of Bengal. The length of the river is about 860 km.
- Its drainage basin is shared by Maharashtra, Chhattisgarh, Jharkhand, and Odisha.
5. The Krishna Basin
- Rising from a spring near Mahabaleshwar, the Krishna flows for about 1400 km and reaches the Bay of Bengal.
- The Tungabhadra, the Koyana, the Ghatprabha, the Musi and the Bhima are some of its tributaries.
- Its drainage basin is shared by Maharasthra, Karnataka and Andhra Pradesh.
6. The Kaveri Basin
- The Kaveri rises in the Brahmagri range of the Western Ghats and it reaches the Bay of Bengal south of Cuddalore in Tamil Nadu.
- The total length of the river is about 760 km.
- Its main tributaries are Amravati, Bhavani, Hemavati and Kabini.
- Its basin drains parts of Karnataka, Kerala and Tamil Nadu.
- It makes the second biggest waterfall in India, known as Shivasamudram Falls. The hydroelectric power generated from the falls is supplied to Mysuru, Bengaluru and the Kolar Gold Field.
- Besides these major rivers, there are some smaller rivers flowing towards the east like the Damoder, the Brahmani, the Baitarni and the Subarnrekha.
Lakes in India
- India has many lakes which differ from each other in size and other characteristics.
- Most lakes are permanent; some contain water only during the rainy season, like the lakes in the basins of inland drainage of semi-arid regions.
- There are some lakes that are the result of the action of glaciers and ice sheets, while others have been formed by wind, river action and human activities.
- A meandering river across a floodplain forms a cut-off that later develops into ox-bow lakes.
- Spits and bars form lagoons in the coastal areas, e.g. the Chilika lake, the Pulicat lake and the Kolleru lake.
- Lakes in the region of inland drainage are sometimes seasonal; for example, the Sambhar lake in Rajasthan, which is a salt water lake. Its water is used for producing salt.
- Most of the freshwater lakes are in the Himalayan region. They are of glacial origin i.e., they formed when glaciers dug out a basin, which was later filled with snowmelt.
- The Wular lake in Jammu and Kashmir, in contrast, is the result of tectonic activity. It is the largest freshwater lake in India. The Dal lake, Bhimtal, Nainital, Loktak and Barapani are some other important freshwater lakes.
- Apart from natural lakes, the damming of the rivers for the generation of hydel power has also led to the formation of lakes, such as Guru Gobind Sagar (Bhakra Nangal Project).
Importance of lakes
- A lake helps to regulate the flow of a river.
- During heavy rains, it prevents flooding and during the dry season, it helps to maintain an even flow of water.
- Lakes can also be used for developing hydel power.
- They moderate the climate of the surroundings; maintain the aquatic ecosystem, enhance natural beauty, help develop tourism and provide recreation.
Economic role of rivers
- Water from rivers is a basic natural resource, essential for various human activities.
- Therefore, riverbanks have attracted settlers from ancient times. These settlements have now become big cities.
- Rivers are used for irrigation, navigation and hydro-power generation which are extremely important for agriculture and livelihood of people.
- The growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water.
- The heavy load of untreated sewage and industrial effluents are also emptied into the rivers.
- This affects not only the quality of water but also the self-cleansing capacity of the river.
- Concern over rising pollution in our rivers led to the launching of various action plans to clean the rivers.
Government Initiatives to combat river pollution
National River Conservation Plan (NRCP)
- The river cleaning programme in the country was initiated with the launching of the Ganga Action Plan (GAP) in 1985.
- The Ganga Action Plan was expanded to cover other rivers under the National River Conservation Plan (NRCP) in the year 1995.
- The objective of the NRCP is to improve the water quality of the rivers, which are major water sources in the country, through the implementation of pollution abatement work.
The Narmada River conservation mission has been undertaken by the government of Madhya Pradesh by a scheme named Namami Devi Narmade.
The Namami Gange Programme is an Integrated Conservation Mission approved as a ‘flagship programme’ by the Union Government in June 2014 to accomplish the twin objectives of effective abatement of pollution, conservation and rejuvenation of the national river, Ganga.
Need to Know Facts
- The world’s largest drainage basin is the Amazon basin.
- According to the regulations of the Indus Water Treaty (1960), India can use only 20% of the total water carried by the Indus river system. This water is used for irrigation in Punjab, Haryana and the southern and western parts of Rajasthan.
- The Sundarbans:
- 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 Royal Bengal tiger.
- Lakes of large extent are called seas, like the Caspian, the Dead and the Aral seas.
- 71% of the world’s surface is covered with water, but 97% of that is salt water. Of the 3% that is available as freshwater, three quarters of it is trapped as ice.
MCQs based on NCERT Class 9 Geography Chapter 3:Drainage
1. In which of the following states is the Wular Lake located?
(b) Uttar Pradesh
(d) Jammu and Kashmir
Wular lake, the largest freshwater lake of India, is located in Jammu and Kashmir.
2. The river Narmada has its source at
(d) Slopes of the Western Ghats
The river Narmada has its source at Amarkantak hills in Madhya Pradesh.
3. Which of the following lakes is a salt water lake?
(d) Gobind Sagar
Sambar Lake in Rajasthan is a salt water lake. Dal lake and Wular lake are fresh water lakes.
4. Which one of the following is the longest river of Peninsular India?
Godavari river is the longest river in Peninsular India.
5. Which one amongst the following rivers flows through a rift valley?
Narmada and Tapi are the two rivers that flow through a rift valley.