Overview
This lecture covers the drainage system of India, focusing on the concepts of drainage basins, river systems, patterns, and the major Indian rivers, along with their significance, features, patterns, and economic importance.
Introduction to Drainage Systems
- A drainage system is the network of rivers and streams draining an area.
- A drainage basin is the area drained by a main river and its tributaries.
- Water divide: elevated land separating two drainage basins.
- Tributary: smaller river joining a main river; distributary: branch that leaves a main river.
Patterns of Drainage
- Drainage patterns are influenced by land slope, rock structure, and climate.
- Main patterns: dendritic (tree-like), rectangular, radial (from a central point), and trellis (parallel streams).
Major Drainage Systems in India
- India’s rivers are classified as Himalayan rivers and Peninsular rivers.
- Himalayan river systems: Indus, Ganga, Brahmaputra.
- Peninsular river systems: Narmada, Tapi, Godavari, Krishna, Mahanadi, Kaveri, etc.
Himalayan River Systems
- Originate from glaciers; perennial (flow year-round).
- Have large basins, long courses, and create fertile plains and deltas.
- Indus system: major tributaries include Jhelum, Chenab, Ravi, Beas, Sutlej.
- Ganga system: main tributaries are Yamuna, Ghaghra, Gandak, Kosi, Son.
- Brahmaputra system starts in Tibet, called Tsangpo, enters India as Dihang.
Peninsular River Systems
- Mostly originate in Western Ghats; rain-fed (seasonal).
- Flow through hard rocks, shorter and straighter courses.
- Narmada and Tapi flow westwards; others flow east to Bay of Bengal.
- Godavari is the largest Peninsular river, known as ‘Dakshin Ganga’.
River Features and Economic Importance
- Floodplains, deltas, and fertile soil are formed by rivers.
- Rivers support agriculture, are sources of hydropower, drinking water, and inland transport.
- River pollution is a concern due to overuse and contamination from human activities.
- Conservation measures like Ganga Action Plan and Namami Gange are in place.
Lakes and Water Bodies
- Types of lakes: freshwater, saltwater, artificial, and those formed by tectonic or glacial activities.
- Example: Wular Lake (freshwater, Kashmir), Chilika Lake (lagoon, Odisha), Sambhar Lake (saltwater, Rajasthan).
Key Terms & Definitions
- Drainage Basin — Area drained by a river and its tributaries.
- Water Divide — Elevated land separating two drainage basins.
- Tributary — River joining a main river.
- Distributary — River branching out from the main river.
- Delta — Triangular landform at a river’s mouth formed by deposition.
- Floodplain — Flat land along a river created by flooding.
- Perennial River — Flows throughout the year.
- Lagoon — Shallow body of water separated from a sea by barriers.
Action Items / Next Steps
- Revise NCERT Class 9 Geography Chapter on Drainage System.
- Review maps of Indian river systems and major lakes.
- Complete assigned textbook questions on drainage patterns and river features.
- Prepare notes on differences between Himalayan and Peninsular river systems.