Geography · Ch 3 — Drainage System
Drainage Systems of India
Drainage Systems of India
The map is a physical-political hybrid of India, drawn with a graticule that runs from 68°E to 96°E longitude and 8°N to 36°N latitude. That frame is not decoration — it fixes the drainage systems in absolute space, so you can read the east-west spread of the Indus and Ganga basins, the north-south run of the Peninsular rivers, and the way the Brahmaputra swings east before turning south into Bangladesh. A scale bar of 0–600 km and a north arrow complete the cartographic apparatus, letting you measure distances and orient the drainage pattern correctly.
The heart of the map is the river network itself. Every major system is labelled by name, not just drawn as a line. In the northwest you see the Indus and its five tributaries — Jhelum, Chenab, Ravi, Beas, and Sutlej — arranged like the fingers of a hand feeding a single trunk. Further south, the Luni runs as a short, lonely stream toward the Rann of Kachchh, a reminder that not all drainage reaches the sea. The Ganga system dominates the north-central belt: the main stem plus Yamuna, Chambal, Betwa, Ken, Gomti, Ghaghara, Gandak, Kosi, and Son. Notice how the northern tributaries (Ghaghara, Gandak, Kosi) descend from the Himalaya, while the southern ones (Chambal, Betwa, Ken, Son) rise in the Peninsular block — the map lets you see this two-sided feeding pattern at a glance.
The Peninsular rivers are shown with their own character. Narmada and Tapi run roughly parallel, flowing west into the Arabian Sea through rift valleys. On the eastern side, the Godavari, Mahanadi, and Krishna drain into the Bay of Bengal, with the Tungabhadra shown as a major tributary of the Krishna and the Kaveri further south. The Penganga appears as a tributary of the Godavari. The Brahmaputra system is drawn in the northeast with its two headstreams, the Dihang and the Lohit, converging to form the main river — a detail that matters because it shows the river's origin as a junction, not a single source.
The single most instructive element is the curved Water Divide line. It runs along the Delhi Ridge, the Aravalli range, and the Sahyadri (Western Ghats), separating the entire country's drainage into two domains: rivers west of this line flow into the Arabian Sea, and rivers east of it flow into the Bay of Bengal. This is not a political boundary — it is a topographic one, and the map makes the concept of a drainage divide visible. Once you trace that curve, you understand why the Narmada and Tapi go west while the Godavari and Krishna go east, and why the Ganga, rising in the Himalaya, still ends up in the Bay of Bengal. …
The Indian drainage system is not a random scatter of rivers — it is the product of two forces working together over geological time. First, the evolution of the three major physiographic units of the country: the Himalayas, the Peninsular Plateau, and the Indo-Gangetic Plain. Second, the nature and characteristics of precipitation, which decides how much water a river carries and how it behaves through the year. Together, these have shaped a network of small and big rivers that drain the entire landmass.
The system is vast. It includes thousands of rivers, ranging from minor seasonal streams to mighty perennial rivers like the Ganga and the Brahmaputra. Every one of them, whether it flows for a few kilometres or for over three thousand, is part of this single integrated drainage network. The size and behaviour of each river depend on the terrain it originates in and the rainfall it receives.
The Himalayan rivers, for instance, are born in snow-covered peaks and are fed by both melting glaciers and monsoon rain. This makes them perennial — they flow throughout the year. They are also young and energetic, carving deep gorges and carrying enormous loads of silt. The Peninsular rivers, in contrast, originate in the plateau region and depend largely on monsoon rainfall. Many of them are seasonal, shrinking to thin streams in the dry months. They flow through older, harder rocks and have gentler gradients compared to their Himalayan counterparts.
The nature of precipitation matters just as much as the terrain. In areas of heavy rainfall, rivers are more numerous and more powerful. In drier regions, the drainage is sparse and the rivers are shorter and less reliable. This is why the drainage density — the number and length of rivers per unit area — varies so greatly across the country. …
- The drainage pattern resembling the branches of a tree is known as 'dendritic', the examples of which are the rivers of the northern plain.
- When the rivers originate from a hill and flow in all directions, the drainage pattern is known as 'radial'. The rivers originating from the Amarkantak range present a good example of it.
- 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'. …