Drainage
The flow of water through well-defined channels is known as ‘Drainage,’ and the network of such channels is called a ‘Drainage System.’
Drainage Pattern
- Drainage Pattern refers to the system of flow of surface water, mainly through the forms of rivers and basins.
- The drainage system depends upon factors such as the slope of the land, the geological structure, the amount of water, and the velocity of water.
Types of Drainage Patterns
Dendritic Drainage Pattern
- It is the most common form and resembles the branching pattern of tree roots.
- The dendritic pattern develops where the river channel follows the slope of the terrain.
- The pattern develops in areas where the rock beneath the stream has no particular structure and can be eroded equally easily in all directions.
- Tributaries join larger streams at acute angles (less than 90°).
- For example, the rivers of the northern plains are Indus, Ganga, and Brahmaputra.
Parallel drainage pattern
- It develops in regions of parallel, elongated landforms where there is a pronounced slope to the surface.
- Tributary streams tend to stretch out in a parallel-like fashion following the slope of the surface.
- For example, the rivers originating in the Western Ghats are Godavari, Kaveri, Krishna, and Tungabhadra.
Trellis Drainage Pattern
- Trellis drainage develops in folded topography where hard and soft rocks exist parallel to each other.
- Down-turned folds called synclines form valleys in which reside the main channel of the stream.
- Such a pattern is formed when the primary tributaries of the main rivers flow parallel to each other and secondary tributaries join them at right angles.
- For example, the rivers in the upper part of the Himalayan region are Indus, Ganga, and Brahmaputra.
Rectangular Drainage Pattern
- It develops on a strongly joined rocky terrain.
- The rectangular drainage pattern is found in regions that have undergone faulting.
- Streams follow the path of least resistance and thus are concentrated in places where exposed rock is the weakest.
- The tributary streams make sharp bends and enter the mainstream at high angles.
- For example, streams are found in the Vindhya mountain range, Chambal, Betwa, and Ken.
Folding and Faulting
- When the Earth’s crust is pushed together via compression forces, it can experience geological processes called folding and faulting.
- Folding occurs when the Earth’s crust bends away from a flat surface.
- A bend upward results in an anticline, and a bend downward results in a syncline.
- Faulting happens when the Earth’s crust completely breaks and slides past each other.
- Whether the Earth’s crust experiences a fold or fault will depend on the material it is made out of in that area.
- A fold is more likely to happen with flexible material and it is what causes mountains to form, whereas a fault will happen with more brittle material and is what causes earthquakes to occur.
Radial Drainage Pattern
- The radial drainage pattern develops around a central elevated point and is common to conically shaped features such as volcanoes.
- When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial.’
- For example, the rivers originate from the Amarkantak range, Narmada, and Son (a tributary of Ganga).
Centripetal Drainage Pattern
- It is just the opposite of the radial as streams flow toward a central depression.
- During wetter portions of the year, these streams feed ephemeral lakes, which evaporate away during dry periods.
- Sometimes, salt flats are also created in these dry lake beds as salt dissolved in the lake water precipitates out of solution and is left behind when the water evaporates away.
- E.g. Loktak lake in Manipur.
Drainage System of India
Himalayan Drainage System
About
- Rivers of this system are fed by the melting of snow and precipitation and, hence, are perennial.
- In their mountainous course, these rivers form V-shaped valleys, rapids, and waterfalls.
- While entering the plains, they form depositional features like flat valleys, oxbow lakes, flood plains, braided channels, and deltas near the river mouth.
Indus River System
- It is one of the largest river basins in the world.
- It is also known as the Sindhu and is the westernmost of the Himalayan rivers in India.
- It originates from a glacier near Bokhar Chu in the Tibetan region in the Kailash Mountain range.
- In Tibet, it is known as ‘Singi Khamban,’ or Lion’s mouth.
- The Indus flows in India only through the Leh district in the Union Territory of Ladakh.
- Important tributaries of the Indus are Sutlej, Ravi, Jhelum, Chenab (the largest tributary of the Indus), and Beas.
Ganga River System
- It rises in the Gangotri glacier near Gaumukh (3,900 m) in Uttarakhand, where it is known as Bhagirathi.
- At Devprayag, the Bhagirathi meets the Alaknanda; hereafter, it is known as the Ganga.
- The Ganga enters the Northern plains at Haridwar.
- Ganga flows through the states of Uttarakhand, Uttar Pradesh, Bihar, and West Bengal.
- Son is the major right bank tributary, and the important left bank tributaries are Ramganga, Gomati, Ghaghara, Gandak, Kosi, and Mahananda.
- The Yamuna is the Ganga’s westernmost and longest tributary, and it has its source in the Yamunotri glacier.
- Ganga flows into the Bay of Bengal near the Sagar Island.
Brahmaputra River System
- It is one of the largest rivers in the world and originated in the Chemayungdung glacier (Kailash range) near the Mansarovar lake.
- In southern Tibet, it is known as the Tsangpo, which means ‘the purifier.’
- The river emerges from the foothills of the Himalayas under the name of Siang or Dihang.
- It enters India west of Sadiya town in Arunachal Pradesh.
- Its main left bank tributaries are Dibang or Sikang, Lohit, Burhi Dihing and Dhansari.
- Important right bank tributaries are the Subansiri, Kameng, Manas, and Sankosh.
- In Bangladesh, it merges with the river Padma, which falls in the Bay of Bengal.
Peninsular Drainage System
About
- The peninsular rivers are characterized by fixed courses, the absence of meanders, and the nonperennial flow of water.
- The drainage system is older than that of the Himalayan one.
- The Western Ghats, which run close to the western coast, act as the water divide between the major Peninsular rivers.
- Most of the major Peninsular rivers, except Narmada and Tapi, flow from west to east.
- The other major river systems of the Peninsular drainage are Mahanadi, Godavari, Krishna, and Kaveri.
Narmada
- It is the largest west-flowing river of the peninsular region, flowing through a rift valley between the Vindhya (north) and the Satpura Range (south).
- It rises from the Maikala range near Amarkantak in Madhya Pradesh.
- Major Tributaries of the river are Hiran, Orsang, Barna, and Kolar.
- The Narmada basin covers parts of Madhya Pradesh, Maharashtra and Gujarat.
- The Sardar Sarovar Project has been constructed on this river.
Tapi
- Another important westward-flowing river originates from the Betul district of Madhya Pradesh in the Satpura ranges.
- It flows in a rift valley parallel to the Narmada but is much shorter in length.
- Its basin covers parts of Madhya Pradesh, Gujarat and Maharashtra.
Mahanadi
- It rises in the Raipur district of Chhattisgarh and runs through Odisha to discharge its water into the Bay of Bengal.
- 53% of the drainage basin of this river lies in Madhya Pradesh and Chhattisgarh, while 47% lies in Odisha.
- Major tributaries: Seonath, Hasdeo, Mand, Ib, Jonking, and Tel rivers.
- Its basin is bounded by the Central India hills on the north, by the Eastern Ghats on the south and east, and by the Maikala range on the west.
Godavari
- It is the largest Peninsular river system and is also called the “Dakshin Ganga.”
- It rises in the Nasik district of Maharashtra and discharges its water into the Bay of Bengal.
- Its tributaries run through the states of Maharashtra, Madhya Pradesh, Chhattisgarh, Odisha, and Andhra Pradesh.
- Penganga, Indravati, Pranhita, and Manjra are its principal tributaries.
Krishna
- Krishna is the second largest east-flowing Peninsular river, which rises near Mahabaleshwar in Sahyadri.
- Koyna, Tungbhadra, and Bhima are its major tributaries.
- It flows through the states of Maharashtra, Karnataka, Telangana, and Andhra Pradesh before flowing into the Bay of Bengal.
Kaveri
- Kaveri rises in Brahmagiri hills of Kodagu district in Karnataka.
- It is a sacred river of southern India.
- Its important tributaries are Arkavathi, Hemavathi, Bhavani, Kabini and Amravati.
- It flows in a southeasterly direction through the states of Karnataka, Kerala and Tamil Nadu and drains into Bay of Bengal through Pondicherry.
