Drainage System of India

Drainage System of India

In this article, we provide you with notes on the Drainage System of India. Drainage System in India is a very important topic for the UPSC preparation. In the Indian Drainage System, you will study the Himalayan drainage system and the Peninsular Drainage System.

You can also check – Geography notes for UPSC

Drainage System of India – Overview

The flow of water through well-defined channels is known as ‘drainage’ and the network of such channels is called a ‘drainage system’. The drainage pattern of an area is the outcome of the geological time period, nature and structure of rocks, topography, slope, amount of water flowing and the periodicity of the flow.

Catchment area– 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. Watersheds are small in area while the basins cover larger areas.

An area drained by a river and its tributaries is called a drainage basin.

The boundary line separating one drainage basin from the other is known as the watershed.

Important Drainage Patterns

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.

• Dendritic Pattern: 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. eg. rivers of the northern plain
• Radial Pattern: The radial pattern develops when streams flow in different directions from a central peak or dome-like structure. eg- The 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’. A trellis drainage pattern develops where hard and soft rocks exist parallel to each other.
• Rectangular Pattern: A rectangular drainage pattern develops on a strongly jointed rocky terrain.
• When the rivers discharge their waters from all directions in a lake or depression, the pattern is known as ‘centripetal’.

A combination of several patterns may be found in the same drainage basin.

Classification of the Indian Drainage System

The Drainage System of India is divided on various bases.

1. On the basis of the discharge of water (orientations to the sea),

1. Arabian Sea drainage; – 23 per cent comprising the Indus, the Narmada, the Tapi, the Mahi and the Periyar systems discharge their waters in the Arabian Sea.
2. Bay of Bengal drainage. – 77 per cent of the drainage area consists of the Ganga, the Brahmaputra, the Mahanadi, the Krishna, etc.

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

2. On the basis of the size of the watershed,

1. Major river basins with 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.
2. Medium river basins with a catchment area between 2,000-20,000 sq. km incorporating 44 river basins such as the Kalindi, the Periyar, the Meghna, etc.
3. Minor river basins with a catchment area of less than 2,000 sq. km include a fairly good number of rivers flowing in the area of low rainfall.

3. On the basis of the mode of origin, nature and characteristics,

1. Himalayan drainage
2. Peninsular drainage.

it is the most accepted basis of classification.

Drainage Systems of India

The Indian drainage system consists of a large number of small and big rivers. It is the outcome of the evolutionary process of the three major physiographic units and the nature and characteristics of precipitation.

The Himalayan Drainage

The Himalayan drainage system has evolved through a long geological history. It mainly includes the Ganga, the Indus and the Brahmaputra river basins.

• Since these are fed both by the melting of snow and precipitation, rivers of this system are perennial.
• These rivers pass through the giant gorges carved out by the erosional activity carried on simultaneously with the uplift of the Himalayas.
• These rivers also form V-shaped valleys, rapids and waterfalls in their mountainous course.
• While entering the plains, they form depositional features like flat valleys, oxbow lakes, flood plains, braided channels, and deltas near the river mouth.
• In the Himalayan reaches, the course of these rivers is highly tortous, but over the plains, they display a strong meandering tendency and shift their courses frequently.
  • River Kosi, also known as the ‘sorrow of Bihar’, has been notorious for frequently changing its course.
  • The Kosi brings a huge quantity of sediments from its upper reaches and deposits it in the plains. The course gets blocked, and consequently, the river changes its course.

Evolution of Himalayan Drainage

There are differences of opinion about the evolution of the Himalayan rivers. However, geologists believe that a mighty river called Shiwalik or Indo-Brahma traversed the entire longitudinal extent of the Himalayas 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

• The remarkable continuity of the Shiwalik and its lacustrine origin and alluvial deposits consisting of sands, silt, clay, boulders and conglomerates support this viewpoint.

It is opined that in due course of time Indo– the Brahma River was dismembered into three main drainage systems:

1. the Indus and its five tributaries in the western part;
2. the Ganga and its Himalayan tributaries in the central part; and
3. the stretch of the Brahmaputra in Assam and its Himalayan tributaries in the eastern part.

The dismemberment was probably due to the Pleistocene upheaval in the western Himalayas, including the uplift of he Potwar Plateau (Delhi Ridge), which acted as the water divide between the Indus and Ganga drainage systems.

The River Systems of the Himalayan Drainage

1. The Indus System

2. The Ganga System

3. The Brahmaputra System

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 except Narmada and Tapi flow from west to east.
• The Chambal, the Sind, the Betwa, the Ken, and the Son, originating in the northern part of the Peninsula belong to the Ganga river system.
• The other major river systems of the Peninsular drainage are – the Mahanadi the Godavari, the Krishna and the Kaveri. Peninsular rivers are characterised by fixed courses, absence of meanders and non-perennial flow of water.
• The Narmada and the Tapi which flow through the rift valley are exceptions.

The Evolution of the Peninsular Drainage System

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

1. Subsidence of the western flank of the Peninsula led to its submergence below the sea during the early tertiary period. Generally, it has disturbed the symmetrical plan of the river on either side of the original watershed.
2. The upheaval of the Himalayas when the northern flank of the Peninsular block was subjected to subsidence and the consequent trough faulting. The Narmada and The Tapi flow in trough faults and fill the original cracks with their detritus materials. Hence, there is a lack of alluvial and deltaic deposits in these rivers.
3. Slight tilting of the Peninsular block from the northwest to the southeastern direction gave orientation to the entire drainage system towards the Bay of Bengal during the same period.

River Systems of the Peninsular Drainage

1. The Mahanadi

2. The Godavari

3. The Krishna

4. The Kaveri

5. The Narmada

6. Tapi

7. Luni

Smaller Rivers Flowing Towards the West

The rivers flowing towards the Arabian Sea have short courses.

• The Shetruniji is one such river which rises near Dalkahwa in Amreli district.
• The Bhadra originates near Aniali village in Rajkot district.
• The Dhadhar rises near Ghantar village in Panchmahal district.
• Sabarmati and Mahi are the two famous rivers of Gujarat.
• The Vaitarna rises from the Trimbak hills in Nasik district at an elevation of 670 m.
• The Kalinadi rises from the Belgaum district and falls into the Karwar Bay.
• The source of the Bedti River lies in Hubli Dharwar and traverses a course of 161 km.
• The Sharavati is another important river in Karnataka flowing towards the west.
  • The Sharavati originates in Shimoga district of Karnataka and drains a catchment area of 2,209 sq. km.
• Goa has two important rivers One is Mandovi and the other is Juari.
• Kerala has a narrow coastline. The longest river of Kerala, Bharathapuzha rises near Annamalai hills. It is also known as Ponnani. It drains an area of 5,397 sq. km.
• The Periyar is the second-largest river in Kerala. Its catchment area is 5,243 sq. km. You can see that there is a marginal difference in the catchment area of the Bhartapuzha and the Periyar rivers.
• Another river of Kerala is the Pamba River which falls in the Vemobanad lake after traversing a course of 177 km.

Small Rivers Flowing towards the East

There are a large number of rivers flowing towards the east along with their tributaries. they join the Bay of Bengal.

These are – The Subarnrekha, the Baitarni, the Brahmani, the Vamsadhara, the Penner, the Palar and the Vaigai are important rivers.

River Regimes

The pattern of flow of water in a river channel over a year is known as its regime.

• The north Indian rivers originating from the Himalayas are perennial
• The rivers of South India do not originate from glaciers and their flow pattern witnesses fluctuations.
  • The flow increases considerably during monsoon rains.
  • Thus, the regime of the rivers of South India is controlled by rainfall which also varies from one part of the Peninsular plateau to the other.
• 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).
• The Ganga has its minimum flow during the January-June period. The maximum flow is attained either in August or in September. After September, there is a steady fall in the flow. The river, thus, has a monsoon regime during the rainy season.
• Narmada has a very low volume of discharge from January to July but it suddenly rises in August when the maximum flow is attained.
• The Godavari has the minimum discharge in May and the maximum in July-August.

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Think and Write

1. Do you know that rivers flow in the same direction?
2. Can you, then, explain the reason for water flowing from one direction to the other?
3. Why do the rivers originating from the Himalayas in northern India and the Western Ghat in southern India flow towards the east and discharge their waters in the Bay of Bengal?
4. Why does the Kosi River bring such a huge quantity of sediments from the upper reaches? Do you think that the discharge of the water in the rivers in general and the Kosi in particular, remains the same, or does it fluctuate?
5. When does the river course receive the maximum quantity of water?
6. What are the positive and negative effects of flooding?
7. Why The rivers flowing towards the Arabian Sea have short courses.

Extra point

Identify these rivers of North India. Large rivers flowing on the Peninsular plateau have their origin in the Western Ghats and discharge their waters in the Bay of Bengal. Identify these rivers of the South India. The Narmada and Tapi are two large rivers which are exceptions. They along with many small rivers discharge their waters in the Arabian Sea. Name these rivers of the western coastal region from the Konkan to the Malabar coast.