Classification of Drainage Systems of India
Geography › Drainage Systems of India · Topic 15.1
A drainage system is the pattern formed by streams and rivers of an area. India's rivers are classified by origin as Himalayan, which are perennial, and Peninsular, which are mostly seasonal; by direction as those draining to the Bay of Bengal, which carry most of the water, those to the Arabian Sea, and inland drainage; and by size of catchment as major, medium and minor. Patterns such as dendritic, trellis, radial and parallel describe the shape of the drainage.
6 min read · UPSC Prelims · Geography · Drainage Systems of India
At a Glance
- By origin Himalayan (perennial) and Peninsular (seasonal)
- By direction Bay of Bengal about 77 per cent of area, Arabian Sea about 23 per cent
- Water share Over 90 per cent of runoff reaches the Bay of Bengal
- Largest basin Ganga, about 8.6 lakh sq km
- Himalayan type Antecedent; Peninsular type: consequent
- Exam link UPSC Prelims, Geography: Drainage Systems of India
Where Does It Fit?
This is the first topic of the macro on the drainage systems of India. The previous macro covered the landforms the rivers flow over, and this one begins with how the rivers are classified. The next topic describes the Indus river system. Previous topic: Lakshadweep Islands and New Moore Island. Next topic: Indus River System.
How Are the Drainage Systems Classified?
In short: Indian rivers can be sorted by where they start, where they end, and how big they are.
| Basis | Classes | Notes |
|---|---|---|
| Origin | Himalayan rivers and Peninsular rivers | Himalayan rivers such as the Indus, Ganga and Brahmaputra are perennial, fed by rain and snow-melt; Peninsular rivers such as the Mahanadi, Godavari, Krishna, Kaveri, Narmada and Tapti depend on rain and are seasonal |
| Direction of flow | Bay of Bengal drainage, Arabian Sea drainage and inland drainage | About 77 per cent of the drainage area is oriented to the Bay of Bengal and about 23 per cent to the Arabian Sea; streams of western Rajasthan such as those draining to Sambhar lake form inland drainage, and the Luni is the main river of the Rann of Kachchh |
| Size of catchment | Major (above 20,000 sq km), medium (2,000 to 20,000), minor (below 2,000) | Basins are grouped by the Central Water Commission into 20 or more river basins |
The largest basin is that of the Ganga, with around 8.6 lakh sq km in India, followed by the Indus (about 3.2 lakh in India), Godavari (3.1 lakh), Krishna (2.6 lakh), Brahmaputra (1.9 lakh), Mahanadi (1.4 lakh), Narmada (about 99,000) and Cauvery (about 81,000). The Brahmaputra and Indus are the longest rivers that flow through India, but much of their courses lie outside the country; the Ganga, at about 2,525 km, is the longest river within India. The Godavari, at about 1,465 km, is the longest of the peninsular rivers.
Why Does the Bay of Bengal Receive So Much More Water?
- Himalayan rivers: the perennial Ganga and Brahmaputra, which carry the largest volumes, flow east.
- Rainfall: the eastern basins get rain from both the southwest and northeast monsoons and from cyclones, while the Arabian Sea basins, including Rajasthan, Haryana and Punjab in the Indus system, are drier, as in Mechanism of the Indian Monsoon.
- Slope: the Peninsula slopes eastward, so its large rivers flow to the Bay of Bengal, while the west-flowing rivers are short and steep streams from the Western Ghats, apart from the Narmada and the Tapti.
- Result: over 90 per cent of India’s river water drains to the Bay of Bengal, even though it covers a smaller share of the area, and this has a bearing on the planning of river-linking schemes, as in Peninsular Drainage and East-Flowing Rivers.
What Are the Types of Drainage Patterns and Evolution?
| Pattern | Description | Example in India |
|---|---|---|
| Dendritic | Tree-like branching on uniform rock | Northern plains rivers |
| Trellis | Main streams parallel with short tributaries meeting at right angles, on folded rocks | Rivers of the old folded Singhbhum region; rivers in the Himalaya before they reach the plains |
| Rectangular | Streams with right-angled bends, controlled by joints and faults | Vindhyan region, such as the Kaimur |
| Radial | Streams flow outward from a central high point | Rivers from Amarkantak; the Girnar and Mandav hills; Chotanagpur |
| Parallel | Streams flow in similar directions on a steep, uniform slope | West-flowing rivers of the Western Ghats |
| Centripetal | Streams flow inward to a basin | Rivers draining into inland lakes such as Sambhar |
The Himalayan rivers are largely antecedent. They existed before the Himalaya rose and, as the land was lifted, they kept cutting down and carved deep gorges, such as those of the Indus, Sutlej and Brahmaputra. In the Peninsula, the rivers are older still and have reached maturity, with broad shallow valleys, little erosion and straight courses, and their drainage is mainly consequent, following the slope. The Narmada and Tapti are thought to occupy rift valleys, and the Himalayan and Peninsular systems also differ in meanders, deltas and navigability, as in Fluvial Landforms and Drainage Patterns. As an analytical point, India has about 4 per cent of the world’s freshwater and 18 per cent of its people, and the average annual flow of its rivers is about 1,900 cubic kilometres, of which only around 1,100 cubic kilometres can be used, so the large east-west gap in the distribution of water is a central question of planning.
Why Is This Topic Important?
- Foundation Frame for all river questions
- Concepts Antecedent and consequent drainage
- Policy River-linking and water sharing
What Came Next?
The next topic describes the Indus river system and its tributaries. Next topic: Indus River System.
Key People and Terms
- Drainage basin Area drained by a river system
- Watershed Divide between two basins
- Antecedent drainage River older than the uplift it cuts
- Consequent drainage River following the slope
- Perennial river River with water all year
- Inland drainage Streams that do not reach the sea
Exam Corner
Points to Remember
- Himalayan rivers are perennial and antecedent.
- About 77 per cent of the area drains to the Bay of Bengal.
- Over 90 per cent of the water goes to the Bay of Bengal.
- The Ganga is the longest river within India.
- The Luni is the main river of the Rann of Kachchh.
Do Not Confuse With
- Antecedent and superimposed drainage Older than the uplift versus from a buried surface
- Basin area and water share Area drained versus volume carried
- Perennial and non-perennial Snow plus rain versus rain only
Memory Hook
Himalayan rivers cut as the mountains rose; Peninsular rivers slope east and wait for the rain.
Mains Angle
Questions compare the two river systems. These points add depth.
- Origin Himalayan versus Peninsular
- Pattern Antecedent versus consequent
- Utility Perennial irrigation
A Question You May Face
An original practice question, not a past paper question.
“Compare the Himalayan and the Peninsular river systems of India in terms of origin, character and utility.”
How to Answer
- Classification Origin, direction, size.
- Himalayan Perennial, antecedent.
- Peninsular Seasonal, mature.
- Importance Irrigation and hydropower.
GS Relevance
Frequently Asked Questions
How are the drainage systems of India classified?
India's drainage systems are classified by origin into Himalayan and Peninsular rivers, by direction of flow into those draining to the Bay of Bengal, the Arabian Sea and inland basins, and by catchment size into major, medium and minor rivers. Drainage patterns describe the geometric shapes the streams form.
What is the difference between Himalayan and Peninsular rivers?
Himalayan rivers are perennial, fed by rain and snow-melt, flow through deep gorges, form meanders and large deltas in the plains, and are antecedent. Peninsular rivers are seasonal, rain-fed, flow in shallow, mature valleys on straight courses, and are consequent in character.
What is antecedent drainage?
Antecedent drainage is a river system that existed before the uplift of the land and maintained its course by cutting down as the land rose. The Indus, Sutlej and Brahmaputra are antecedent rivers, and their deep gorges through the Himalayas show that they are older than the mountains.
Why does most of India's river water flow to the Bay of Bengal?
Most of India's water flows to the Bay of Bengal because the large perennial Himalayan rivers, the Ganga and Brahmaputra, drain eastward, the Peninsula slopes eastward, and the eastern basins receive both southwest and northeast monsoon rain. More than 90 per cent of the runoff goes to the Bay of Bengal.
Which is the largest river basin of India?
The Ganga basin is the largest, with about 8.6 lakh square kilometres in India, followed by the Indus, Godavari, Krishna and Brahmaputra basins. The Godavari is the largest basin among the peninsular rivers, with an area of about 3.1 lakh square kilometres.
PYQ Practice — Statement Analysis
1 The Himalayan rivers are generally perennial.
They get snow-melt and rain.
2 Most Peninsular rivers drain into the Arabian Sea.
Most flow east to the Bay of Bengal.
3 The Indus and Brahmaputra are examples of antecedent drainage.
They cut gorges while the Himalayas rose.
4 The Luni is the longest river of the Peninsula.
The Godavari is the longest peninsular river.
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