Overview
This lecture explains the drainage system of India, covering major river systems, lakes, their economic roles, causes of river pollution, and important comparative features.
Drainage Basics
- Drainage refers to the river system of an area.
- A drainage basin is the area drained by a single river system.
- A water divide is an elevated area separating two drainage basins.
India's Drainage Systems
- Indian rivers are categorized as Himalayan (perennial) and Peninsular (mainly seasonal).
- Himalayan rivers are long, cut gorges, and create large deltas; Peninsular rivers are shorter and have shallower courses.
- Most Peninsular rivers flow east towards the Bay of Bengal, with notable exceptions like Narmada and Tapi flowing west.
Major Himalayan Rivers
- Indus: Originates near Lake Mansarowar (Tibet), passes Ladakh, joined by several tributaries, flows into the Arabian Sea.
- Ganga: Formed by Bhagirathi and Alaknanda at Devaprayag, joined by Yamuna and others, creates the Sundarban Delta.
- Brahmaputra: Rises east of Mansarowar, called Tsang Po in Tibet, enters India as Dihang, causes annual floods due to high rainfall.
Main Peninsular Rivers
- Narmada: Rises in Amarkantak hills, flows through a rift valley to the Arabian Sea.
- Tapi: Originates in Satpura range, shorter in length, also flows westward.
- Godavari: Largest Peninsular river, also known as Dakshin Ganga.
- Mahanadi, Krishna, Kaveri: Flow eastwards, form deltas, important for regional drainage.
Lakes in India
- Lakes are formed by glacial, tectonic, river, wind, or human actions.
- Himalayan freshwater lakes (e.g., Wular, Dal) are glacial; some like Wular are tectonic.
- Saltwater lakes (e.g., Sambhar) are found in semi-arid regions.
- Artificial lakes are often created by damming rivers.
- Lakes regulate river flow, prevent floods, support power generation, tourism, and climate moderation.
Economic Role of Rivers
- Rivers supply water for irrigation, industry, domestic use, navigation, and hydroelectricity.
- Many major cities have developed on riverbanks due to these resources.
River Pollution
- Increased human activity and pollution from untreated sewage and effluents degrade river water.
- Initiatives like the Ganga Action Plan and National River Conservation Plan aim to clean major rivers.
Key Terms & Definitions
- Drainage basin — Area drained by a river system.
- Water divide — Elevated land separating drainage basins.
- Perennial river — River with year-round flow.
- Delta — Landform at river mouth formed by deposited sediment.
- Estuary — Tidal mouth of a river where it meets the sea.
- Rift valley — A lowland formed by faulting, where rivers like Narmada flow.
- Braided channel — River channel with multiple, intertwining streams.
Action Items / Next Steps
- Complete map exercises labeling key rivers and lakes of India.
- Answer and review chapter questions on drainage patterns, river systems, and their characteristics.
- Research on Namami Gange and Namami Devi Narmade river conservation projects.
- List natural and artificial lakes using an atlas.