India: Physical Environment and Drainage
India’s physical environment and drainage form the base map for agriculture, settlement and hazards. The exam tests physiographic divisions, river systems, drainage patterns and the Himalayan–peninsular contrast.
Core rules
- Major divisions: Himalayas, Indo-Gangetic Plain, Peninsular Plateau, coastal plains and islands.
- Himalayan rivers (Indus, Ganga, Brahmaputra) are perennial, fed by snowmelt and monsoon; peninsular rivers are largely rain-fed and seasonal.
- East-flowing peninsular rivers such as Mahanadi, Godavari, Krishna and Kaveri build deltas; west-flowing rivers such as Narmada and Tapi flow through rift valleys.
- Drainage patterns include dendritic, trellis, radial and centripetal; a water divide separates basins.
- The Ganga–Brahmaputra delta is the world’s largest delta, formed by heavy sediment load.
Worked example
Classify the Godavari and justify it. It rises in the Western Ghats, flows east across the Deccan Plateau and forms a delta on the Bay of Bengal. It is a peninsular, east-flowing river, rain-fed and seasonal, with a large delta. Unlike the Ganga, it does not receive Himalayan snowmelt, so its low-flow season is more pronounced. The reasoning uses source, direction, regime and landform.
Traps
Do not label Narmada and Tapi east-flowing; they enter the Arabian Sea. Do not call all peninsular rivers non-perennial without noting exceptions. Do not confuse a drainage pattern with a drainage system. Do not place the Western Ghats in the Indo-Gangetic Plain.