Points to Remember
- The term drainage describes the river system of an area.
- The area drained by a single river system is called a drainage basin.
- Any elevated area such as a mountain or an upland which separates two drainage basins is known as a water divide.
- Small streams flowing in different directions come together to form a river which ultimately drains into a large waterbody such as a lake or sea or an ocean.
2. Drainage Systems in India Indian rivers are divided into two major groups: the Himalayan rivers and the Peninsul arrives.
(i) The Himalayan Rivers
- (a) Most of the Himalayan rivers are perennial, which means that they have water throughout the year.
- (b) These rivers receive water from rain as well as frommelted snow from the lofty mountains.
- (c) The two major Himalayan rivers, the Indus and the Brahmaputra, originate from the North of the mountain ranges.
- (d) They perform intensive erosional activity in their upper courses and carry huge loads of silt and sand.
(ii) The Peninsular Rivers
- (a) Peninsular Rivers are mainly seasonal and flow during the rainy season.
- (b) During the dry season, the peninsular regions have reduced flow of water.
- (c) They have shallower and shorter courses.
- (d) Most peninsular rivers originate in the Western Ghats and flow towards the Bay of Bengal.
3. Drainage Patterns
(i) The streams within a drainage basin form certain patterns, depending on the slope of land, underlying rock structure and the climatic conditions of the area. The drainage patterns are
- (a) Dendritic Pattern A dendritic pattern develops when the river channel follows the slope of the terrain. The stream with its tributaries resemble the branches of a tree and so it is called dendritic.
- (b) Trellis Pattern A river, joined by its tributaries at approximately right angles, develops where hard and soft rocks exits parallel to each other.
- (c) Rectangular Pattern A rectangular drainage pattern develops on a strongly jointed rocky terrain.
- (d) Radial Pattern The radial pattern develops when streams flow in different directions from a central peak or dome like structure. A combination of several patterns may be found in the same drainage basin.
4. The Himalayan Rivers
(i) The major Himalayan rivers are the Indus, the Ganga and the Brahmaputra.(ii) The rivers are long and are joined by many large and important tributaries. A river along with its tributaries is called a river system.
5. The Indus River System
- The river Indus rises in Tibet near lake Mansarowar.
- Flowing West, it enters India in the Ladakh district of Jammu and Kashmir.
- Several tributaries, the Zanskar, 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 in Pakistan.
- The Satluj, Beas, Ravi, Chenab and Jhelum join together to enter the Indus near Mithankot in Pakistan.
- 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 2,900 km, the Indus is one of the longest rivers of 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. The rest is in Pakistan.
6. The Ganga River System
- The headwaters of the Ganga, called the Bhagirathi, is fed by the Gangotri glacier and joined by the Alaknanda at Devaprayag in Uttarakhand to form the Ganga.
- At Haridwar the Ganga emerges from the mountains into the plains.
- The Ganga is joined by many tributaries from the Himalayas, a few of them being major rivers such as Yamuna, Ghaghara, Gandak and Kosi.
- The Ganga from Farakka in West-Bengal bifurcates into two, from where the Bhagirathi-Hooghly (a distributary)flows southwards to the Bay of Bengal. The main stream flows southwards into Bangladesh and is joined by the Brahmaputra.
- It forms the world’s biggest delta called Sunderban delta. The length of the Ganga is 2,500 km.
7. The Brahmaputra River System
- The Brahmaputra rises in Tibet east of Mansarowar Lakevery close to the sources of Indus and the Satluj.
- It is slightly longer than the Indus and most of its course lies outside India.
- On reaching the Namcha Barwa (7,757 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 others tributaries to form the Brahmaputra in Assam.
- In Tibet, it carries a smaller volume of water and less siltas it is a cold region.(vi) In India, it carries a large volume of water and considerable amount of silt because it passes through an area of high rainfall.
- During the rainy season, the river overflows its banks causing widespread devastation due to floods in Assam and Bangladesh.
- It flows into the Bay of Bengal and deposits a lot of silt. Its hifts its channel frequently.
8. 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 peninsular rivers like the Mahanadi, Godavari, Krishna and Kaveri flow eastwards and drain into the Bay of Bengal.
- These rivers make deltas at their mouths.
- The Narmada and the Tapi are the only long rivers which flow west and make estuaries.
- The drainage basins of the peninsular rivers are comparatively small in size.
9. The Narmada Basin
- The Narmada rises in the Amarkantak Hills in Madhya Pradesh.
- It flows towards the west in the Rift Valley formed due to faulting.
- Narmada creates many picturesque locations like the ‘Marble Rocks’ near Jabalpur, where the Narmada flows through a deep gorge and the ‘Dhuadhar falls’ where the river plunges over steep rocks.
- All the tributaries of the Narmada are very short and most of these join the main stream at right angles.
- The Narmada basin covers parts of Madhya Pradesh and Gujarat.
10. The Tapi Basin
- The Tapi rises in the Satpura ranges in the Betul district of Madhya Pradesh.
- It 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 main west flowing rivers are Sabarmati, Mahi, Bharathpuzha and Periyar.
11. 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 and it drains into the Bay of Bengal.
- Its drainage basin is among the largest in the peninsula arrivers and covers parts of Maharashtra Madhya Pradesh, Odisha and Andhra Pradesh.
- Its tributaries are Purna, Wardha, Pranhita, Manjra, Wainganga and Penganga.
- Because of its length and the large area that it covers, it is also known as the Dakshin Ganga.
12. The Mahanadi Basin
- The Mahandi rises in the high lands 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 Orrisa.
13. The Krishna Basin
- It rises from a spring near Mahabaleshwar and flows for about 1400 km to reach the Bay of Bengal.
- The Tungabhadra, Koyana, Ghatprabha, Musi and Bhimaare some of its tributaries.
- Its drainage basin is shared by Maharashtra, Karnataka and Andhra Pradesh.
14. The Kaveri Basin
- The Kaveri rises in Brahmagri range of the Western Ghats and reaches the Bay of Bengal south of Cuddalore in Tamil Nadu.
- 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.
- India has many lakes. These differ from one another in size and other characteristics.
- Some of the lakes are the result of the action of glaciers and ice sheets, while others have been formed by wind or river action and human activities.
- A meandering river across a flood plain forms cut-offs that later develop into ox-bow lakes.
- Spits and bars form lagoons in the coastal areas e.g.,Chilka Lake, Pulicat Lake and Kolleru Lake.
- Most fresh water lakes are in the Himalayan region. They are mainly of glacial origin.
- The Wular Lake in Jammu and Kashmir is the result of tectonic activity. It is the largest fresh water lake in India.
- The Dal lake, Bhimtal, Nainital, Loktak and Barapani are some important fresh water lakes
- Apart from natural lakes, damming of rivers for the generation of hydel power has also led to the formation of lakes such as Guru Gobind Sagar (Bhakra Nangal Project).
- Lakes are of great value to human beings because they help to regulate the flow of a river.
- During heavy rainfall lakes prevent flooding.
- They can be used for developing hydel power.
- They moderate the climate of the surroundings and maintain the aquatic eco-system, enhancing natural beauty.
- Lakes also help to develop tourism and provide recreation.
- Inland salt water lakes are mainly found in Rajasthan e.g., Sambhar Lake. It is used for producing salt.
16. Role of Rivers in the Economy
- Rivers have played an important role throughout human history.
- Water from the rivers is a basic natural resource essential for various human activities.
- Rivers provide water for irrigation.
- They provide the facility for navigation.
- They provide water for domestic use like washing, cooking, drinking etc.
- They help to generate hydroelectric power.
- The river banks attracted settlers from ancient times, and these settlements have now become big cities.
- They help to moderae the climate of the surrounding area.
- They help to promote fisheries.
17. Causes of River Pollution
- The growing domestic, municipal, industrial and agricultural demand for water from rivers naturally affects the quality of water.
- Due to this demand, more and more water is being drained out of the rivers, reducing their volume.
- Due to overuse of river water, aquatic life is affected negatively.
- Heavy loads of untreated sewage and industrial effluents are emptied into the rivers, thus polluting them.
18. Conservation of Rivers
- Concern over river pollution in our rivers led to the launching of various action plans to clean the rivers.
- The Ganga Action Plan has been launched to cleanse and save the Ganga.
- Through newspapers, radio and TV, awareness is being generated among the people about the need to protect our rivers.
- The National River Conservation Plan (NRCP) was launched to protect the rivers.
- A total of 215 schemes of pollution abatement have been sanctioned. 69 schemes have been completed under the NRCP.
- A million litres of sewage is targeted to be intercepted, diverted and treated per year.
- NCERT Revision Notes for Class 9 (All Subjects)
- Class 9 Social Science Notes (Chapter-wise PDF)
- NCERT Solutions for class 9th Social-Science Geography Chapter 3 Drainage