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Peninsular River System or Peninsular Drainage
Peninsula rivers are much older than the Himalayan rivers {Discordant}.
The peninsular drainage is mainly Concordant except for few rivers in the upper peninsular region.
They are non-perennial rivers with a maximum discharge in the rainy season.
The peninsular rivers have reached mature stage {Fluvial Landforms} and have almost reached their base level. [Vertical downcutting is negligible].
The rivers are characterized by broad and shallow valleys.
The river banks have gentle slopes except for a limited tract where faulting forms steep sides.
The main water divide in peninsular rivers is formed by the Western Ghats, which run from north to south close to the western coast.
The velocity of water in the rivers and the load carrying capacity of the streams is low due to low gradient.
Most of the major rivers of the peninsula such as the Mahanadi, the Godavari, the Krishna and the Cauvery flow eastwards and drain into the Bay of Bengal. These rivers make deltas at their mouths.
But the west flowing rivers of Narmada and Tapi as well as those originating from the Western Ghats and falling in the Arabian Sea form estuaries in place of deltas.
There are few places where rivers form superimposed and rejuvenated drainage which are represented by
Examples: The Jog on the Sharvati (289 m), Yenna of Mahabaleshwar (183 m), Sivasamundram on the Cauvery (101 m), Gokak on the Gokak (55 m), Kapildhara (23 m) and Dhuandar (15 m) on the Narmada are the major waterfalls in the Peninsular India.
Evolution of the Peninsular Drainage
Theory 1
Geologists believe that the Sahyadri-Aravali axis was the main water divide in the past.
According to one hypothesis, the existing peninsula is the remaining half of bigger landmass.
The Western Ghats were located in the middle of this landmass.
So one drainage was towards east flowing into Bay of Bengal and the other towards west draining into Arabian Sea.
The western part of the Peninsula cracked and submerged in the Arabian Sea during the early Tertiary period (coinciding with the formation of Himalayas).
During the collision of the Indian plate, the Peninsular block was subjected to subsidence in few regions creating a series of rifts (trough, faults).
The now west flowing rivers of the Peninsula, namely the Narmada and the Tapi flow through these rifts.
Straight coastline, steep western slope of the Western Ghats, and the absence of delta formations on the western coast makes this theory a possibility.
Theory 2
It is believed that the west flowing peninsular rivers do not flow in the valleys formed by the rivers themselves.
Rather they have occupied two fault rifts in rocks running parallel to the Vindhyas.
These faults are supposed to be caused by bend of the northern part of the Peninsula at the time of upheaval of the Himalayas.
Peninsular block, south of the cracks, tilted slightly eastwards during the event thus giving the orientation to the entire drainage towards the Bay of Bengal.
Criticism: Tilting should have increased the gradient of the river valleys and caused some rejuvenation of the rivers. This type of phenomenon is absent in the Peninsula, barring a few exceptions such as waterfalls.
Peninsular River System
Rivers that drain into Bay of Bengal: The Mahanadi, the Godavari, the Krishna, the Cauvery and several smaller rivers drains south-east into the Bay of Bengal.
Rivers that drain into Arabian Sea: The Narmada, the Tapi, the Mahi flowing west as well as several small streams originating from the Western Ghats flow westwards into the Arabian Sea.
Rivers that drain into the Ganges: Tributaries of the Ganga and the Yamuna such as the Chambal, the Betwa, the Ken, the Son and the Damodar flow in the north-easterly direction.
Himalayan River System vs. Peninsular River System
The Himalayan River System
The Peninsular River System
These rivets originate from the lofty Himalayan ranges and are named as the Himalayan rivers.
These rivers originate in the Peninsular Plateau and are named as Peninsular rivers.
Catchment area
These rivers have large basins and catchment areas. The total basin area of the Indus, the Ganga and the Brahmaputra is 11.78, 8.61 and 5.8 lakh square kilometres respectively.
These rivers have small basins and catchment areas. The Godavari has the largest basin area of 3.12 lakh square kilometres only which is less than one-third the basin area of the Indus.
Valleys
The Himalayan rivers flow through deep V – shaped valleys called gorges. These gorges have been carved out by down cutting carried on side by side with the uplift of the Himalayas.
The Peninsular rivers flow in comparatively shallow valleys. These are more or less completely graded valleys. The rivers have little erosional activity to perform.
Drainage Type
These are examples of antecedent drainage.
These are examples of consequent drainage.
Water Flow
The Himalayan rivers are perennial in nature, i.e., water flows throughout the year in these rivers. These rivers receive water both from the monsoons and snow-melt. The perennial nature of these rivers makes them useful for irrigation.
The Peninsular rivers receive water only from rainfall and water flows in these rivers in rainy season only. Therefore, these rivers are seasonal or non-perennial. As such these rivers are much less useful for irrigation.
Stage
These rivers flow across the young fold mountains and are still in a youthful stage.
These rivers have been flowing in one of the oldest plateaus of the world and have reached maturity.
Meanders
The upper reaches of the Himalayan rivers are highly tortuous. When they enter the plains, there is a sudden reduction in the speed of flow of water. Under these circumstances these rivers form meanders and often shift their beds.
The hard rock surface and non-alluvial character of the plateau permits little scope for the formation of meanders. As such, the rivers of the Peninsular Plateau follow more or less straight courses.
Deltas and Estuaries
The Himalayan rivers form big deltas at their mouths. The Ganga-Brahmaputra delta is the largest in the world.
Some of the Peninsular rivers, such as the Narmada and the Tapi form estuaries.
Other rivers such as the Mahanadi, the Godavari, the Krishna and the Cauvery form deltas.
Several small streams originating from the Western Ghats and flowing towards the west enter the Arabian Sea without forming any delta.
Sir, when will you release the updated version of your notes?