Detailed Summary
The term drainage refers to the collective river systems in a given area. A physical map shows how smaller streams converge to form a main river, which ultimately drains into larger bodies of water like lakes or oceans. The section introduces the concept of drainage basins—the area drained by a single river system—and water divides, which separate two drainage basins.
In India, the drainage systems are categorized primarily into Himalayan rivers and Peninsular rivers. Himalayan rivers are predominantly perennial, nourished by rainfall and melting snow, and they sculpt deep gorges through their erosive actions. Key rivers include the Indus and Ganga, both of which have vital tributaries.
Peninsular rivers, in contrast, are often seasonal and have shorter courses, predominantly flowing toward the Bay of Bengal. This section also discusses the economic significance of rivers and lakes, emphasizing irrigation, navigation, and hydropower generation. It highlights the major river systems of both regions and their tributaries, along with the ecological importance of lakes and the hazards of river pollution.