Drainage Systems (Rivers and Lakes) for UPSC Prelims
1. Introduction to Drainage Systems
India’s drainage systems, comprising rivers and lakes, are vital for its geography, economy, and ecology. Rivers, originating from the Himalayas and Peninsular Plateau, form extensive drainage basins, supporting agriculture, hydropower, and urban centers. Lakes, both natural and man-made, contribute to water storage, biodiversity, and tourism. Understanding drainage patterns and their significance is crucial for UPSC Prelims, as they influence India’s climate, livelihoods, and environmental challenges.
Key Facts
- Major Rivers: Ganga, Indus, Brahmaputra (Himalayan); Godavari, Krishna (Peninsular)
- Lakes: Natural (e.g., Dal, Wular), man-made (e.g., Bhakra Nangal)
- Drainage Basins: Cover ~90% of India’s land area
- Significance: Supports 1.4 billion people through water and resources
Important Facts for UPSC
- The Ganga basin is India’s largest, supporting 43% of its population.
- Himalayan rivers are perennial; Peninsular rivers are mostly seasonal.
- Lakes like Chilika are critical for biodiversity and fisheries.
2. Types of Drainage Patterns
Overview
Drainage patterns are the spatial arrangements of rivers and streams, shaped by topography, geology, and climate.
Major Patterns
| Pattern |
Description |
Examples in India |
| Dendritic |
Tree-like, common in flat terrains |
Ganga, Yamuna |
| Trellis |
Rectangular, in folded mountains |
Indus tributaries in Himalayas |
| Radial |
Outward from a central high point |
Narmada from Amarkantak |
| Parallel |
Streams flow parallel to each other |
Rivers in Western Ghats |
Significance
Drainage patterns determine river flow, sediment deposition, and land use patterns.
Important Facts for UPSC
- Dendritic patterns dominate the Northern Plains due to flat alluvium.
- Trellis patterns are common in the Himalayas due to folded rocks.
- Radial patterns are seen in Peninsular hills like Amarkantak.
3. Himalayan Rivers
Overview
Himalayan rivers, originating from glaciers and snowfields, are perennial, with large drainage basins and significant sediment loads.
Major Rivers
| River |
Origin |
Length (km) |
Drainage Basin |
| Ganga |
Gangotri Glacier, Uttarakhand |
2,525 |
Northern Plains, Bay of Bengal |
| Indus |
Mansarovar Lake, Tibet |
3,180 |
Punjab, Arabian Sea |
| Brahmaputra |
Angsi Glacier, Tibet |
2,900 |
Northeast India, Bay of Bengal |
Characteristics
- Perennial Flow: Fed by snowmelt and monsoon rains.
- High Erosion: Carries heavy silt, forming fertile deltas.
- Large Basins: Ganga basin covers ~26% of India’s land area.
Important Facts for UPSC
- The Ganga-Brahmaputra Delta is the world’s largest, in West Bengal.
- The Indus Water Treaty (1960) governs Indus sharing with Pakistan.
- Brahmaputra is called Tsangpo in Tibet and Dihang in Arunachal.
4. Peninsular Rivers
Overview
Peninsular rivers, originating from the Peninsular Plateau, are mostly seasonal, with smaller basins and less sediment load compared to Himalayan rivers.
Major Rivers
| River |
Origin |
Length (km) |
Drainage Basin |
| Godavari |
Trimbakeshwar, Maharashtra |
1,465 |
Deccan, Bay of Bengal |
| Krishna |
Mahabaleshwar, Maharashtra |
1,400 |
Deccan, Bay of Bengal |
| Narmada |
Amarkantak, Madhya Pradesh |
1,312 |
Central India, Arabian Sea |
Characteristics
- Seasonal Flow: Dependent on monsoon rains, dry in summer.
- Smaller Basins: Godavari is the largest, covering ~10% of India.
- Estuaries: Form smaller estuaries, unlike Himalayan deltas.
Important Facts for UPSC
- Godavari is called the “Ganga of the South” due to its large basin.
- Narmada and Tapi are the only major Peninsular rivers flowing westward.
- Krishna forms a fertile delta in Andhra Pradesh, supporting rice cultivation.
5. Comparison of Himalayan and Peninsular Rivers
| Aspect |
Himalayan Rivers |
Peninsular Rivers |
| Origin |
Glaciers, snowfields |
Peninsular hills |
| Flow |
Perennial |
Seasonal |
| Basin Size |
Large (e.g., Ganga) |
Smaller (e.g., Godavari) |
| Landforms |
Deltas (e.g., Sundarbans) |
Estuaries (e.g., Narmada) |
| Sediment Load |
High, fertile alluvium |
Low, less fertile |
Important Facts for UPSC
- Himalayan rivers support larger populations due to fertile plains.
- Peninsular rivers are vital for hydropower (e.g., Sardar Sarovar on Narmada).
- Himalayan rivers cause frequent floods; Peninsular rivers face water scarcity.
6. Major Lakes of India
Overview
India’s lakes, both natural and man-made, play key roles in water supply, biodiversity, and tourism.
Types and Examples
| Type |
Lake |
Location |
Features |
| Natural (Freshwater) |
Wular |
Jammu & Kashmir |
India’s largest freshwater lake |
| Natural (Saltwater) |
Chilika |
Odisha |
Largest brackish water lagoon, Ramsar site |
| Man-made |
Bhakra Nangal |
Himachal Pradesh |
Formed by Bhakra Dam, hydropower |
| Glacial |
Tsomgo |
Sikkim |
High-altitude lake, tourism |
Characteristics
- Natural Lakes: Formed by tectonic, glacial, or coastal processes.
- Man-made Lakes: Created by dams for irrigation, hydropower, and water supply.
- Biodiversity: Lakes like Chilika host migratory birds (e.g., flamingos).
Important Facts for UPSC
- Chilika Lake is Asia’s largest brackish water lake, a Ramsar site since 1981.
- Wular Lake is shrinking due to siltation and encroachment.
- Loktak Lake (Manipur) has floating islands (phumdis), unique globally.
7. River Basin Management and Interlinking
Overview
Effective management of river basins is critical for water security, flood control, and sustainable development.
Key Initiatives
- National River Linking Project (NRLP): Aims to transfer water from surplus to deficit basins (e.g., Ken-Betwa link).
- Namami Gange: Focuses on cleaning and conserving the Ganga River.
- Dam Projects: Bhakra, Sardar Sarovar for irrigation and power.
Challenges
- Floods in Himalayan rivers (e.g., Brahmaputra).
- Water scarcity in Peninsular rivers (e.g., Krishna).
- Interstate disputes (e.g., Cauvery between Karnataka and Tamil Nadu).
Important Facts for UPSC
- Namami Gange, launched in 2014, is a ₹20,000 crore project.
- The Ken-Betwa link is India’s first river interlinking project.
- Cauvery Water Dispute Tribunal was set up in 1990.
8. Geographical Significance of Drainage Systems
Climatic Influence
Rivers distribute monsoon waters, while lakes moderate local climates (e.g., Dal Lake in Srinagar).
Landform Creation
Rivers carve valleys, deltas, and plains; lakes form basins and wetlands.
Biodiversity
River basins and lakes support ecosystems, e.g., Sundarbans (Ganga-Brahmaputra) and Chilika (Irrawaddy dolphins).
Important Facts for UPSC
- The Ganga-Brahmaputra system carries 25% of India’s water flow.
- Peninsular rivers shape the Deccan’s topography through gorges.
- Lakes like Vembanad (Kerala) support unique backwater ecosystems.
9. Socioeconomic and Environmental Impact
Socioeconomic Role
- Agriculture: Rivers irrigate 60% of India’s farmland (e.g., Punjab).
- Hydropower: Dams like Bhakra generate 14% of India’s electricity.
- Tourism: Lakes (e.g., Dal) and rivers (e.g., Ganga at Varanasi) attract millions.
Environmental Challenges
- Pollution: Ganga receives 3,000 million liters of sewage daily.
- Siltation: Reduces lake and reservoir capacity (e.g., Wular).
- Climate Change: Alters river flows and lake levels.
Important Facts for UPSC
- The Ganga supports 10% of the world’s population in its basin.
- Over-extraction of groundwater threatens Peninsular river flows.
- Chilika’s restoration boosted fish production by 400% since 2000.
10. Significance for Geography
Geographical Significance
Drainage systems shape India’s topography, climate, and ecosystems, creating diverse geographical regions.
Environmental Significance
Rivers and lakes sustain biodiversity but face threats from pollution and overuse.
Socioeconomic Significance
They drive agriculture, industry, and cultural practices, requiring sustainable management.
UPSC Relevance
Drainage systems are a core topic in Indian geography, tested for their geographical, economic, and environmental roles.
Important Facts for UPSC
- India has 12 major river basins and 46 medium basins.
- River disputes are governed by the Inter-State River Water Disputes Act, 1956.
- Lakes are protected under the Wetlands (Conservation and Management) Rules, 2017.
UPSC Preparation Tips
- Memorize major rivers (origins, lengths, basins) and lakes (types, locations).
- Understand drainage patterns (dendritic, trellis) and their formation.
- Focus on Himalayan vs. Peninsular river differences (flow, landforms).
- Link drainage to agriculture, hydropower, and environmental issues.
- Practice map-based questions on river courses and lake locations.
- Revise key terms (delta, estuary, phumdi) and initiatives (Namami Gange).