Indian drainage systems: Himalayan & Peninsular rivers
A systematic comparison of India's Himalayan and Peninsular drainage systems—origins, antecedence, river capture, and the dispute geography UPSC tests.
The fundamental binary
Indian drainage is classified into two great systems whose contrasts UPSC tests relentlessly: the Himalayan rivers (perennial, snow- and rain-fed) and the Peninsular rivers (largely seasonal, rain-fed). The dividing logic is geological age and source.
The Himalayan system comprises three master streams—the Indus, Ganga, and Brahmaputra—each rising beyond the great Himalayan crest near the Tibetan Plateau and the Mansarovar–Kailash region. The Indus rises near Lake Mansarovar (Tibet) at about 4,164 m; the Ganga's headstream, the Bhagirathi, emerges from the Gangotri glacier (Gaumukh); the Brahmaputra rises as the Tsangpo in the Chemayungdung glacier near Mansarovar. These rivers are antecedent—they predate the Himalayan uplift and cut down their gorges as the mountains rose, producing the deep transverse gorges of the Indus (near Gilgit), the Sutlej, and the Brahmaputra's Dihang gorge through the Namcha Barwa syntaxial bend.
Himalayan characteristics
Himalayan rivers are perennial because they draw from both glacial melt and the summer monsoon. In their youthful upper courses they perform intense vertical erosion, carving V-shaped valleys, gorges, rapids and waterfalls. On reaching the plains they enter old age: meanders, ox-bow lakes, braided channels, and vast deltas. The Ganga–Brahmaputra delta (the Sundarbans) is the world's largest delta. These rivers carry enormous silt loads, building the fertile Indo-Gangetic alluvial plain—the foundation of India's most productive agriculture.
The Ganga system's chief left-bank tributaries (Ghaghara, Gandak, Kosi) are Himalayan and flood-prone; the Kosi is called the 'Sorrow of Bihar' for its westward channel-shifting. Right-bank tributaries (Yamuna, Son, Chambal) include Peninsular contributors. The Brahmaputra enters India in Arunachal Pradesh as the Siang/Dihang, becomes the Brahmaputra in Assam, is braided and flood-prone, and is called the Jamuna in Bangladesh before joining the Ganga (Padma).
River capture and the Peninsular contrast
The Peninsular rivers flow over an old, stable, hard Archaean shield. They are mostly seasonal, follow broad shallow valleys nearly graded to base level (showing little down-cutting), and have small deltas or estuaries. The main water divide is the Western Ghats, running close to the west coast—hence most large Peninsular rivers (Godavari, Krishna, Kaveri, Mahanadi) flow east into the Bay of Bengal and build deltas, while only the Narmada and Tapi flow west into the Arabian Sea through fault troughs (rift valleys), forming estuaries, not deltas.
The Godavari is the largest Peninsular river ('Dakshin Ganga'), rising at Trimbak near Nashik. River capture (e.g. the Chambal–Banas systems) and superimposed/rejuvenated drainage in the Peninsula are recurring Prelims map questions.
