Drainage systems of India: Himalayan & peninsular

Drainage systems of India

  • An area drained by a river and its tributaries is called a drainage basin while the area drained by a single river system is called a drainage basin.

  • The Indian rivers are divided into two major groups: (i) the Himalayan rivers; and (ii) the peninsular rivers.

The Himalayan drainage

  • 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.

  • Since these are fed both by melting of snow and precipitation, rivers of this system are perennial.

Evolution of the Himalayan drainage

  • Geologists believe that a mighty river called shiwalik or Indo-brahma traversed the entire longitudinal extent of the Himalaya from assam to punjab.

  • And onwards to sind, and finally discharged into the gulf of sind near lower punjab during the miocene period some 5-24 million years ago.

  • It is opined that in due course of time Indo–brahma river was dismembered into three main drainage systems:

(i) the indus and its 5 tributaries in the western part;

(ii) the ganga and its Himalayan tributaries in the central part; and

(iii) the stretch of the brahmaputra in assam and its Himalayan tributaries in the eastern part.

The peninsular drainage system

  • 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.

  • The western ghats running close to the western coast act as the water divide between the major peninsular rivers, discharging their water in the bay of Bengal and as small rivulets joining the arabian sea.

  • Most of the major peninsular rivers mahanadi, the godavari, the krishna and the kaveri except narmada and tapi flow from west to east.

  • The chambal, the sind, the betwa, the ken, the son, originating in the northern part of the peninsula belong to the ganga river system.

Evolution of peninsular drainage system

  • Three major geological events in the distant past have shaped the present drainage systems of peninsular India:

  • (i) subsidence of the western flank of the peninsula leading to its submergence below the sea during the early tertiary period.

  • (ii) upheaval of the Himalayas when the northern flank of the peninsular block was subjected to subsidence and the consequent trough faulting.

  • (iii) slight tilting of the peninsular block from northwest to the southeastern direction gave orientation to the entire drainage system towards the bay of Bengal during the same period.

Difference between Himalayan rivers and peninsular rivers:

Aspects Himalayan river Peninsular river
1. Place of origin Himalayan mountain covered with glaciers Peninsular plateau and central highland
2. Nature of flow Perennial; receive water from glacier and rainfall Seasonal; dependent on monsoon rainfall
3. Type of drainage Antecedent and consequent leading to dendritic pattern in plains Super imposed, rejuvenated resulting in trellis, radial and rectangular patterns
4. Nature of river Long course, flowing through the rugged mountains experiencing headward erosion and river capturing Smaller, fixed course with well-adjusted Valleys
5. Catchment area Very large basins Relatively smaller basin
6. Age of the river Young and youthful, active and deepening in the valleys Old rivers with graded profile & have Almost reached their base levels

Drainage patterns of IndiaImportant drainage patterns

Dentritic pattern:

  • The drainage pattern resembling the branches of a tree is known as “dendritic”.

  • Ex:- rivers of northern plain.

Radial pattern:

  • When the rivers originate from a hill and flow in all directions, the drainage pattern is known as ‘radial’.

  • Ex:- rivers originating from the amarkantak range.

Trellis pattern:

  • When the primary tributaries of rivers flow parallel to each other and secondary tributaries join them at right angles, the pattern is known as ‘trellis’.

Centripetal pattern:

  • When the rivers discharge their waters from all directions in a lake or depression, the pattern is know as ‘centripetal’.

Other divisions drainage systems of India

On the basis of discharge of water:

  • The discharge is the volume of water flowing in a river measured over time. It is measured either in cusecs (cubic feet per second) or cumecs (cubic metres per second)..

(i) the Arabian Sea drainage; and

(ii) the Bay of Bengal drainage.

  • They are separated from each other through the Delhi ridge, the Aravalis and the Sahyadris.

  • 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.

On the basis of the size of the watershed:

  • A river drains the water collected from a specific area, which is called its ‘catchment area’.

  • The catchments of large rivers are called river basins while those of small rivulets and rills are often referred to as watersheds.Watershed rivers in India

(i) Major river basins

  • More than 20,000 sq. km of catchment area.

  • It includes 14 drainage basins such as the Ganga, the Brahmaputra, the Krishna, the Tapi, the Narmada, the Mahi, the Pennar, the Sabarmati, the Barak, etc.

(ii) Medium river basins

  • Between 2,000-20,000 sq. km catchment area

  • Incorporating 44 river basins such as the Kalindi, the Periyar, the Meghna, etc.

(iii) Minor river basins

  • Less than 2,000 sq. km catchment area

  • It include number of rivers flowing in the area of low rainfall.

Note: The Narmada and Tapi are two large rivers which are exceptions. They along with many small rivers discharge their waters in the Arabian Sea.

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