Contribution of Water by Various Rivers

River	% Contribution of water
Brahmaputra	~ 40
Ganga	~ 25
Godavari	~ 6.4
Mahanadi	~ 3.5
Krishna	~ 3.4
Narmada	~ 2.9
Rest	~ 20

Classification of Drainage Systems of India

Drainage Systems Based on the Size of the Catchment Area

Division	Size of catchment area in sq km
Major river	20,000
Medium river	20,000 – 2,000
Minor river	2,000 and below

Drainage Systems Based on Origin

• The Himalayan Rivers: Perennial rivers: Indus, the Ganga, the Brahmaputra and their tributaries.
• The Peninsular Rivers: Non-Perennial rivers: Mahanadi, the Godavari, the Krishna, the Cauvery, the Narmada and the Tapi and their tributaries.

Drainage Systems Based on the Type of Drainage

The river systems of India can be classified into four groups viz.

• Himalayan rivers, Deccan rivers and Coastal rivers that drain into the sea.
• Rivers of the inland drainage basin (endorheic basin). Streams like the Sambhar in western Rajasthan are mainly seasonal in character, draining into the inland basins and salt lakes. In the Rann of Kutch, the only river that flows through the salt desert is the Luni.

Drainage Systems Based on Orientation to the sea

• The Bay of Bengal drainage (Rivers that drain into Bay of Bengal)(East flowing rivers)
• Arabian sea drainage (Rivers that drain into Arabian sea)(West flowing rivers).
• The rivers Narmada (India’s holiest river) and Tapti flow almost parallel to each other but empty themselves in opposite directions (West flowing). The two rivers make the valley rich in alluvial soil and teak forests cover much of the land.

The Bay of Bengal drainage	Arabian Sea drainage
Rivers that drain into Bay of Bengal	Rivers that drain into Arabian sea
East flowing rivers	West flowing rivers
~ 77 per cent of the drainage area of the country is oriented towards the Bay of Bengal	~ 23 per cent of the drainage area of the country is oriented towards the Arabian sea
The Ganga, the Brahmaputra, the Mahanadi, the Godavari, the Krishna, the Cauvery, the Penneru, the Penneiyar, the Vaigai, etc.	The Indus, the Narmada, the Tapi, the Sabarmati, the Mahi and the large number of swift flowing western coast rivers descending from the Sahyadris.

• The area covered by The Bay of Bengal drainage and Arabian Sea drainage are not proportional to the amount of water that drains trough them.

Over 90 per cent of the water drains into the Bay of Bengal; the rest is drained into the Arabian Sea or forms inland drainage.

Lop sided distribution

• The Arabian Sea drainage or Western drainage receive less rainfall [Rajasthan, Haryana and Punjab receive very low rainfall].
• The Eastern drainage or the Bay of Bengal drainage receives rainfall both from South-west and North-east monsoons.
• Most of the Himalayan waters (perennial rivers) flow into eastern drainage (Ganges and Brahmaputra).
• Indian Rivers that flow into Arabian Sea are seasonal or non-perennial (Luni, Narmada, etc.).
• Occurrence of more cyclonic rainfall in the eastern parts is another major reason.

Major River System or Drainage Systems in India

Himalayan River systems

• Indus River System
• Brahmaputra River System
• Ganga River System

Peninsular River Systems

• Godavari River System
• Krishna River System
• Cauvery River System
• Mahanadi River System

West Flowing Peninsular River Systems

• Narmada River System
• Tapti River System

• The names of the basins along with their id and area are given in the table.

Sl. No	Basin Code	Basin Name	Area (sq.km)	Rank
1	1	Indus (Up to border)	3,21,289	3
2	2A	Ganga	8,61,452	1
3	2B	Brahmaputra	1,94,413	6
4	2C	Barak and others	41,723
5	3	Godavari	3,12,812	4
6	4	Krishna	2,58,948	5
7	5	Cauvery	81,155	11
8	6	Subernarekha	29,196
9	7	Brahmani and Baitarni	51,822
10	8	Mahanadi	1,41,589	7
11	9	Pennar	55,213
12	10	Mahi	34,842
13	11	Sabarmati	21,674
14	12	Narmada	98,796	9
15	13	Tapi (Tapti)	65,145	12
16	14	West flowing rivers from Tapi to Tadri	55,940
17	15	West flowing rivers from Tadri to Kanyakumari	56,177
18	16	East flowing rivers between Mahanadi and Pennar	86,643	10
19	17	East flowing rivers between Pennar and Kanyakumari	1,00,139	8
20	18	West flowing rivers of Kutch and Saurashtra including Luni	3,21,851	2
21	19	Area of inland drainage in Rajasthan
22	20	Minor rivers draining into Myanmar & Bangladesh	36,202

Primary References: NCERT Geography, Govt Website, Indian Geography by Kullar [Amazon and Flipkart]