The Drainage System of India

The Drainage System of India is controlled by the geographical features of the Indian subcontinent. By examining the situation of Indian Geography, rivers of India are divided into two categories; Himalayan Rivers (Drainage System) and Peninsular Rivers. This section of Rivers of India is the most important topic for UPSC prelims and other State PSCs prelims examinations.

Basic Terms related to Drainage System of India

Catchment Area (Or) Basin Area the area in which a river drains its water collected from a specific source Command Area is the area around the dam, where the benefits of the dam, such as irrigation water, electricity, etc., reach. Govt. runs various Command Area development programs nearby almost all big & small Dams.

Rivers of India

Antecedent Rivers: These are rivers that are older than the physical barrier it cuts through. For instance, all rivers originating from Tibet is older than the Himalayas. These rivers thus originate before the shape is formed (Tibet is older than the Himalayas). Antecedent rivers are those rivers that originate before their slope or gradient.

Consequent Rivers are those rivers that originate only after the formation of its slope. All Peninsular rivers and their drainage system emerge only after the formation of landforms that created a slope towards the sea. (Deccan Plateau is the geologically oldest landform in India.)

V-Shaped Valley: In conditions of high altitude, high slope and flow are over soft rocks, then steep, deep and narrow valley is formed due to Vertical Erosion. Such valleys are V-shaped valleys.

Climate of India
V-shaped Valley

Meander: These soft rocks are easily eroded resulting in the serpentine Flow pattern of the river. These are called Meanders. E.g: v-shaped valleys and meanders are seen predominantly in the Himalayan Rivers.

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Lateral Erosion: If the flow is over hard rocks, the banks are eroded and the valleys formed are wide and shallow. This erosion of banks alone is called lateral erosion. Here meanders are restricted. E.g. peninsular Rivers of India. [Hard rocks resist erosion; the metamorphic rocks of the Peninsular are highly resistant to erosion by their hardness]

Climate of India
Illustration of Lateral Erosion

The Drainage system of India 

The Drainage system of India is purely controlled by the geographical condition of the Indian Subcontinent. Based on origin, the drainage system of India (Rivers of India) is divided into two categories:

Himalayan Drainage System of India

The Himalayan drainage system of India contains Indus, Ganga, Brahmaputra, and their tributaries. The basin or catchment area of Ganga is the largest in India. Indus and Brahmaputra are the longest rivers of this drainage system but these rivers are being shared by neighboring countries as well. The Longest River in India is River Ganga. The Himalayan rivers of India have long routes from their originating source to the Oceans or sea. These rivers perform heavy soil erosional activity in the upper region of routes (Himalayan Regions) and carry a large amount of sand and silt along to the plains.

Major rivers of India
Major Rivers of India

Himalayan rivers have perennial flow. Their valleys are deep due to the vertical erosion. With perennial flow and deep valleys, in the Himalayan course, these rivers are useful for Hydro Power Production and in plains for Navigation. The Himalayan rivers form Meanders as their flow is serpentine. The Himalayan drainage system is Antecedent in nature as these rivers are older than the Himalayan mountain ranges. Indus, Brahmaputra, Sutlej, and Arun-Kosi originate from Tibet and cut across the Himalayan mountain ranges to flow into the plains.

Climate of India
Classification of Drainage System of India| Image Credit: Internet

Peninsular Rivers of India is a type of drainage system based on the flow of the river, peninsular rivers are classified as East flowing peninsular rivers, West flowing Peninsular rivers, and Inland Drainage.

East Flowing Peninsular Rivers

Mahanadi (Odisha), Godavari, Krishna (Andhra Pradesh) & Kaveri (Tamil Nadu). The Godavari has the largest basin and it is the second-largest basin of India after Ganga. So it is called Dakshinganga.

These rivers are consequent. Their flow is south-east along the slope of the Indian Peninsular. These rivers are seasonal as their flow is over hard metamorphic rocks. With low altitude and slope, these rivers are involved in lateral erosion. With lateral erosion, their valleys are wide and shallow. With seasonal flow and wide and shallow valleys, these rivers are neither useful for hydric power nor navigation. Formations of meanders are restricted.

West Flowing Peninsular Rivers

Narmada and Tapi are the important west-flowing rivers. These rivers flow into rift valleys which are linear, deep, narrow, and steep (which is why their course is almost like a straight line). Rift valleys are formed due to the Down faulting of rocks (Endogenetic Forces). This is why their flow is opposite to the slope of the Peninsula [the slope of the Indian is south-east ward]. Narmada is the longest west flowing river.

Inland Drainage System

If the ultimate flow of water is not to the sea, it is called an Inland Drainage System. Luni forms an inland drainage system. Its flow is into the Rann Of Kutch in Gujarat. The Rann of Kutch is saline and marshy area.