Introduction to Drainage System
This article deals with ‘Introduction to Drainage System ’ This is part of our series on ‘Geography’ which is important pillar of GS-1 syllabus . For more articles , you can click here
|Channel||A defined zone which has a certain depth in which there is continuous flow of water under normal conditions.|
|Drainage||The flow of water in well defined channel is known as Drainage .|
|Drainage System||The network of channels which drains a region is known as Drainage System.|
|Drainage Basin||The drainage basin is the area drained by the river and it’s tributaries.|
|Catchment / Catchment Area||The river drains the water collected from a specific area. This area is known as the Catchment Area or Catchment .|
|Water Divide / Watershed||Watershed divides the one catchment area from other catchment area. It is also known as Water divide.|
|River Regime||The seasonal flow of water in a river is known as River regime. Hence, if the water availability is uniform around the year, it is known as Uniform River Regime. Whereas rivers where the water is seasonal, it is known as Non-uniform River Regime. Such seasonal rivers are also known as Ephemeral rivers.|
|Inland Drainage||Rivers which don’t reach the ocean . In desert or arid regions, such rivers lead to the formation of Salt Lakes or Playa Lakes .|
Types of drainage pattern
Geometric system of streams in a region is determined by.
|1. Slope||3. Hydraulic Variability.|
|2. Difference in rock resistance to erosion||4. Structural control of Landscape.|
1 . Antecedent or Inconsequent
- Antecedent drainage pattern is one in which a part of a river slope and the surrounding area gets uplifted but the river sticks to its original slope, cutting through the uplifted portion forming deep gorges
- Eg : Those rivers which existed before upheaval of Himalayas like Indus, Satluj, Ganga, Brahmaputra, Arun, Tista etc. . These rivers originates in Tibet and cut across Himalayas forming deep gorges.
- Rivers which flow in direction of slope.
- Most peninsular rivers like Godavari, Krishna, Cauvery etc.
3. Superimposed /Superinduced
- In this, drainage pattern exhibits discordance with underlying rock because it originally developed on a cover of rocks that has now disappeared .
- The river has enough erosive power that it can cut through any kind of bedrock, maintaining its former drainage pattern.
- Damodar, Subarnarekha, Chambal, Banas etc.
- Drainage in which branches give appearance of tree .
- Dendritic pattern develops in a terrain which has uniform lithology, and where faulting and jointing are insignificant.
- Most rivers of Indo-Gangetic plain show Dendritic drainage pattern.
- Rectangular pattern where two sets of structural control occur at right angle.
- Eg : Drainage pattern of Singhbhum(Chotanagpur).
- In Obsequent drainage pattern, tributaries intend to flow upstream instead of downstream.
- Eg : Arun river which is tributary of Kosi & Suru of Indus.
- The main stream bends at right angles and the tributaries join at right angles creating rectangular patterns.
- It differs from trellis as it is more irregular.
- It is found in Vindhyan mountains.
- Outflowing rivers , away from central point.
- Radial pattern tends to develop on flanks of a dome or volcanic cone.
- Rivers originating from Amarkantak hills , Chotanagpur Plateau & Mikir hills .
- Subsequent stream flows curving prior to joining the consequent stream.
- It is not very common . In India, it is found in Nilgiri hills of Tamil Nadu & Kerala.
10 . Parallel
- Rivers flow parallel to each other. In this, rivers will not meet but keep on running parallel.
- Small rivers originating in western ghats & discharging water in Arabian sea.
- Uncoordinated pattern of drainage, characteristic of a region recently vacated by ice sheet & has not adjusted according to solid rocks underlying.
- Eg : Drainage pattern found in glaciated valleys of Karakoram.
There are various ways to classify Indian Rivers.
1 . On basis of Discharge of Water
- All Indian rivers discharge water either in Arabian Sea or Bay of Bengal.
- Nearly 77% of the drainage area consisting of the Ganga, the Brahmaputra, the Mahanadi, the Krishna, etc. is oriented towards the Bay of Bengal while 23% comprising the Indus, the Narmada, the Tapi, the Mahi and the Periyar systems discharge their waters in the Arabian Sea.
- They are separated from each other through the Delhi ridge, the Aravallis and the Sahyadri.
- It should be mentioned here that the over 90% of the water carried by the Indian rivers is drained into the Bay of Bengal; the rest is drained into the Arabian Sea or forms inland drainage.
2. On Basis of Size of Watershed
|Major River Basins||Catchment area of more than 20,000 sq. km||14|
|Medium River Basins||2,000 to 20,000 sq. km||44|
|Minor River Basins||Less than 2,000 sq. km||55|
Ranking (catchment area)
3. On Basis of Mode of Origin
- Northern/Himalayan Rivers
- Peninsular Rivers.
- Although it has the problem of including Chambal, Betwa, Son, etc. which are much older in age and origin. than other rivers that have their origin in the Himalayas, it is the most accepted basis of classification.
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