What is Drainage?
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 that separates two drainage basins is known as a water divide.
The streams within a drainage basin form certain patterns, depending on the slope of the land, underlying rock structure as well as the climatic conditions of the area. These are dendritic, trellis, rectangular, and radial patterns.
- The dendritic pattern develops where the river channel follows the slope of the terrain. The stream with its tributaries resembles the branches of a tree, thus the name dendritic.
- A river joined by its tributaries, at approximately right angles, develops a trellis pattern. A trellis drainage pattern develops where hard and soft rocks exist parallel to each other.
- A rectangular drainage pattern develops on a strongly jointed rocky terrain.
- 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.
Types of Drainage Patterns
Try yourself:Which of the following describes drainage patterns resembling branches of a tree?
Dendritic drainage pattern.
In a dendritic system, there are many contributing streams (analogous to the twigs of a tree), which are then joined together into the tributaries of the main river (the branches and the trunk of the tree, respectively). They develop where the river channel follows the slope of the terrain.
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 Peninsular Rivers
These rivers originate from glaciers.
These rivers originate on the plateau.
Their catchment area is very large.
Their catchment area is very small.
These rivers pass through gorges and carve
These rivers form shallow valleys.
These rivers are young.
These have acquired maturity.
These are engaged in high erosion activity.
These have very little erosional activity.
These are useful for irrigation.
These are of little use for irrigation.
These rivers are perennial, i.e., they flow
throughout the year.
These rivers are non-perennial.
Indus, Ganga, Brahmaputra Are The Main
Godavari, Krishna, Kaveri, Narmada and Tapti
are major 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.
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. 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 the states of Jammu and Kashmir, Himachal Pradesh and Punjab and the rest are in Pakistan.
Indus River System
The Ganga System
- The Jhelum, an important tributary of the Indus, rises from a spring at Verinag situated at the foot of the Pir Panjal in the south-eastern part of the valley of Kashmir.
- The Chenab is the largest tributary of the Indus. it is formed by two streams, the Chandra and the Bhaga, which join at Tandi near Keylong in Himachal Pradesh. hence, it is also known as Chandrabhaga. The river flows for 1,180 km before entering Pakistan.
- The Ravi is another important tributary of the Indus. it rises west of the Rohtang pass in the Kullu hills of Himachal Pradesh and flows through the Chamba valley of the state.
- The Beas is another important tributary of the Indus, originating from the Beas Kund near the Rohtang Pass at an elevation of 4,000 m above the mean sea level.
- The Satluj originates in the Rakas Lake near Mansarovar at an altitude of 4,555 mt. In Tibet, where it is known as Langchen Khambad.
The Brahmaputra 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 Chambat, 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
- 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.
Try yourself:Which place is located on the water divide between the Indus and the Ganga river system ?
Ambala is the city located on the water divide between Indus and Ganga river systems. Any elevated area, such as a mountain or upland, separates two drainage basins. Such upland is known as water divide.
The Peninsular Rivers
The Peninsular drainage system is older than the Himalayan one. This is evident from the broad, largely-graded shallow valleys, and the maturity of the rivers. Peninsular rivers are characterized by fixed course, absence of meanders, small drainage basins and non-perennial flow of water. The main water divide in peninsular Indian is formed by the Western Ghats. Most of the major rivers of the Peninsula flow eastwards and drain into the Bay of Bengal. The Narmada and the Tapi which flow through the rift valley are exceptions.The Narmada Basin
The Tapi Basin
- The Narmada originates on the western flank of the Amarkantak plateau at a height of about 1, 057m. It falls into the Arabian Sea south of Bharuch. The Sardar Sarovar Project has been constructed on this river.
- Flowing in the rift valley between the Satpura in the south and the Vindhya range in the north 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 the 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.
The Tapi originates from the Satpura ranges in the Betul district of Madhya Pradesh. nearly 79 per cent of its basin lies in Maharashtra, 15 per cent in Madhya Pradesh and the remaining 6 per cent in Gujarat. The Tapi flows in a rift valley parallel to the Narmada but it is much shorter in length.The Godavari Basin
- The Godavari is the largest peninsular river system. it rises from the slopes of the Western Ghats in the Nashik district of Maharashtra. its length is about 1500 km.
- Because of its length and the area it covers, it is also known as the Dakshin Ganga. its basin cover parts of Maharashtra, Madhya Pradesh, Orissa and Andhra Pradesh.
- The Godavari is joined by a number of tributaries such as the Penganga, the Preheat, the Manjira, the Wainganga and the Wardha. It finally drains into the Bay of Bengal.
- The Mahanadi rises near Sihawa in the Raipur district of Chattisgarh and runs through Orissa to discharge its water into Bay of Bengal. fifty-three per cent of the drainage basin of this river lies in Madhya Pradesh and Chattisgarh, while 47 per cent lies in Orissa.
- 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.
- 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.
East flowing Rivers of Peninsular
West flowing Rivers of Peninsular
Rivers – Mahanadi, Godavari, Krishna and Kaveri flow from west to east into the Bay of Bengal.
Rivers – Narmada and Tapi flow from East to West into the Arabian Sea.
These rivers form fertile deltas along the eastern coast.
These form estuaries on the western coast.
These rivers are longer and drain bigger areas. Their main course is in a flat area.
These two rivers are shorter as compared to east-flowing rivers. They flow through the trough and from gorges.
They are rain-fed and depend on rainfall and are seasonal.
They are also rain-fed and are seasonal rivers.
- Sambhar Lake is the largest inland salt take of India situated in Rajasthan. Other salt lakes in Rajasthan are Didwana, Degana, Pachadra, Kucha man, 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.
- 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 very important to man.
- A lake helps to regulate the flow of a river.
- During heavy rainfall they prevent flooding and during the dry season, they help maintain an even flow of water.
- Lakes are also used for developing hydel power.
- Lakes are a valuable source of water.
- They moderate the climate of the surrounding areas.
- They maintain the aquatic ecosystem.
- They enhance natural beauty, helps in developing tourism.
- They provide recreation through boating and swimming.
Role of Rivers in the Economy
- Rivers have formed fertile northern plains and deltas containing alluvial soils which are the most productive agricultural lands of India.
- 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.
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 rising pollution of our rivers has launched of various action plants to clean the rivers.
National River Conservation Plan (NRCP)
- The activates of Ganga Action Plan (GAP) phase-l were started in 1985.
- They declared closed on 31st March 2000.
- The steering committee of the National River Conservation Authority reviewed the progress of the GAP and necessary corrections were made on the basis of lamed and experiences gained from GAP phase l.
- They have been applied to the major polluted rivers of their country under the NRCP.
- The Ganga Action Plan (GAP) Phase-ll has been merged with the NRCP. The expanded NRCP now covers 152 towns located along 27 interstate rivers in 16 states. Under this action plan, pollution abatement work is being taken up in 57 towns. a total of 215 schemes of pollution abatement have been sanctioned. so far, 69 schemes have been completed under this action plan. A million litre of sewage is targeted to be intercepted, diverted and treated.
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 makes 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 Aral seas.