Drainage
'Rivers are the LIFEBLOOD of India — they shape agriculture, economy, culture, and civilisation. The Ganga is not just a river but a SYMBOL of India's spiritual and cultural heritage.'
1. What is Drainage?
Drainage refers to the river system of an area — the network of rivers, streams, and lakes that drain the land. Drainage Basin or Catchment Area: The area drained by a river and its tributaries. Water Divide (or Watershed): The boundary separating two drainage basins — usually an elevated area like a mountain or plateau.
'India's drainage systems are classified into TWO major groups based on their ORIGIN — the HIMALAYAN rivers and the PENINSULAR rivers. This classification is fundamental to understanding India's geography.'
| Feature | Himalayan Rivers | Peninsular Rivers |
|---|
| Origin | Himalayas (snow-fed) | Peninsular Plateau (rain-fed) |
| Nature | PERENNIAL (flow throughout the year) | SEASONAL (depend on monsoon) |
| Length | LONG (hundreds to thousands of km) | SHORTER (few hundred km) |
| Course | Young, youthful — meanders, gorges | Mature — broad valleys, lower gradients |
| Drainage pattern | Antecedent/trellis | Dendritic/radial |
| Deltas | Large, highly fertile (Sundarbans) | Smaller but fertile (Godavari, Krishna deltas) |
2. The Himalayan Rivers
2.1 The Indus River System
- Origin: Near Mansarovar Lake in Tibet (Kailash range, ~5,100 m elevation).
- Length: ~2,900 km (total), ~1,140 km in India.
- Flow: Tibet → Ladakh (India) → Pakistan → Arabian Sea.
- Major Tributaries: Sutlej (largest tributary in India), Beas, Ravi, Chenab, Jhelum.
- Key fact: The Indus flows through Ladakh only in India. The other five Punjab rivers (Sutlej, Beas, Ravi, Chenab, Jhelum) flow through Punjab and Haryana.
- The Indus Waters Treaty (1960): Divided the Indus system between India (eastern rivers — Sutlej, Beas, Ravi) and Pakistan (western rivers — Indus, Chenab, Jhelum).
2.2 The Ganga River System
- Origin: Gangotri Glacier (Gaumukh, Uttarakhand) — known as Bhagirathi at source.
- Length: ~2,525 km (longest in India).
- Flow: Uttarakhand → UP → Bihar → Jharkhand → West Bengal → Sunderbans Delta (world's largest delta) → Bay of Bengal.
- Major Tributaries:
- Right bank: Yamuna (largest tributary), Son, Tons.
- Left bank: Ghaghara, Gandak, Kosi (known as the 'Sorrow of Bihar' because of frequent floods), Gomti.
- Key fact: The Ganga has the largest river basin in India — covering ~8.6 lakh sq km (26% of India's total area).
- Pollution: The Ganga is one of the most polluted rivers in the world. The Namami Gange Programme (2014) is the flagship conservation initiative.
'Yamuna: The Yamuna originates from the Yamunotri Glacier (Uttarakhand). It joins the Ganga at Triveni Sangam, Prayagraj — the site of the Kumbh Mela. The Yamuna is the most polluted river in India, especially after entering Delhi.'
2.3 The Brahmaputra River System
- Origin: Chemayungdung Glacier (Tibet, near Mansarovar Lake, ~5,150 m elevation).
- Length: ~2,900 km (total), ~916 km in India.
- Flow: Tibet (where it is called Tsangpo) → Arunachal Pradesh (where it enters India as Dihang) → Assam (as Brahmaputra) → Bangladesh (as Jamuna) → Bay of Bengal.
- Unique feature: The Brahmaputra flows through a deep gorge (the Yarlung Tsangpo Grand Canyon) in Tibet — one of the deepest canyons in the world.
- Key fact: The Brahmaputra carries the largest volume of water among Indian rivers — and causes the most devastating floods in Assam.
3. The Peninsular Rivers
Peninsular rivers are rain-fed and seasonal — they depend on the monsoon for their water flow. Most of them flow west to east (into the Bay of Bengal) except Narmada and Tapi (west-flowing into the Arabian Sea).
| River | Origin | Length | Mouth | Key Features |
|---|
| Godavari | Triambakeshwar, Nashik (Maharashtra) | 1,465 km (largest peninsular) | Bay of Bengal (into AP) | Dakshin Ganga. Largest drainage basin in peninsular India. Flows through Maharashtra, Chhattisgarh, Telangana, AP. |
| Krishna | Mahabaleshwar (Maharashtra) | 1,400 km | Bay of Bengal (into AP) | Second largest peninsular river. Flows through Maharashtra, Karnataka, Telangana, AP. |
| Mahanadi | Sihawa, Chhattisgarh | 858 km | Bay of Bengal (Odisha) | Known as the 'Sorrow of Odisha' due to floods. Hirakud Dam — one of the longest dams in the world. |
| Kaveri | Brahmagiri Range, Karnataka | 770 km | Bay of Bengal (Tamil Nadu) | Known as 'Ganga of the South'. Forms the Kaveri delta — one of the most fertile regions in India. |
| Narmada | Amarkantak (MP) | 1,312 km | Arabian Sea (Gujarat, Gulf of Khambhat) | West-flowing. Rift valley river — flows between the Vindhya and Satpura ranges. |
| Tapi | Betul, MP | 724 km | Arabian Sea (Surat, Gulf of Khambhat) | West-flowing. Rift valley river. |
| Penna | Nandi Hills, Karnataka | 597 km | Bay of Bengal (Nellore, AP) | Seasonal river. Flows through Rayalaseema region of AP. |
4. Godavari — The Dakshin Ganga (AP Focus)
'The Godavari is ANDHRA PRADESH's lifeline — the largest peninsular river, it flows through the state for ~500 km before emptying into the Bay of Bengal through a WIDE delta.'
| Godavari Fact | Detail |
|---|
| Total length | 1,465 km (largest peninsular river) |
| Origin | Triambakeshwar (Nashik, Maharashtra) |
| AP length | ~500 km |
| Major dams in AP | Polavaram Project (on Godavari, under construction) — controversial, will irrigate 7.2 lakh acres. Dowleswaram Barrage (Rajahmundry). |
| Delta | Godavari delta in East and West Godavari districts — very fertile, known for paddy cultivation |
| Tributaries in AP | Sabari, Purna, Manjira (joins before entering AP) |
| Water disputes | Godavari Water Disputes Tribunal (1969) — between Maharashtra, Chhattisgarh, Telangana, AP, Odisha, Karnataka |
5. Krishna River (AP Focus)
| Krishna Fact | Detail |
|---|
| Total length | 1,400 km (second largest peninsular) |
| Origin | Mahabaleshwar (Maharashtra) |
| AP length | ~400 km |
| Major dams in AP | Srisailam Dam (on Krishna, also in Telangana) — hydroelectric + irrigation. Nagarjunasagar Dam (one of the tallest masonry dams in the world — 124 m). Prakasam Barrage (Vijayawada). |
| Delta | Krishna delta in Guntur and Krishna districts — second major delta in AP |
| Tributaries | Tungabhadra (largest), Bhima, Musi, Koyna, Ghataprabha |
| Water disputes | Krishna Water Disputes Tribunal — between Maharashtra, Karnataka, Telangana, AP |
6. Lakes
| Lake | Location | Type | Key Features |
|---|
| Chilika Lake | Odisha | LAGOON — largest brackish water lake in India. Connected to Bay of Bengal. Ramsar site. | |
| Kolleru Lake | AP (between Godavari and Krishna deltas) | FRESHWATER lake (shallow). Ramsar site. Important bird sanctuary. | |
| Sambhar Lake | Rajasthan | SALTWATER — India's largest inland salt lake. | |
| Loktak Lake | Manipur | FRESHWATER — famous for Phumdis (floating islands). Keibul Lamjao National Park — only floating national park in the world. | |
| Dal Lake | Jammu & Kashmir | FRESHWATER — famous for houseboats, Shikaras, Mughal Gardens. | |
| Wular Lake | Jammu & Kashmir | FRESHWATER — one of the largest freshwater lakes in Asia. | |
| Pulicat Lake | AP-TN border | LAGOON — second largest brackish water lake in India. Sriharikota (ISRO launch site) on the barrier island. | |
7. River Pollution and Conservation
| Issue | Detail |
|---|
| Domestic sewage | Major source — untreated sewage from cities flows directly into rivers (Ganga, Yamuna). |
| Industrial effluents | Tanneries (Kanpur — Ganga), chemical plants (Delhi — Yamuna). Heavy metals, toxins. |
| Agricultural runoff | Pesticides, fertilisers, herbicides. Eutrophication (algal blooms, oxygen depletion). |
| Fertiliser overuse | Excess nutrients (nitrogen, phosphorus) → algal blooms → fish kills. |
| Plastic waste | Non-biodegradable. Blocks drainage, harms aquatic life. |
Conservation Initiatives
- Namami Gange Programme (2014): Flagship programme for Ganga rejuvenation. Budget: ~₹20,000 crore. Focus on sewage treatment, riverfront development, biodiversity conservation.
- National River Conservation Plan (NRCP) : Earlier programme covering 190 towns on 40 rivers.
- National Green Tribunal (NGT): Has passed strict orders against polluting industries.
- AP-specific: Godavari and Krishna Action Plans — similar to Ganga Action Plan.
8. Common Mistakes
- 'All peninsular rivers flow into the Bay of Bengal' — CORRECTION: Narmada and Tapi flow into the Arabian Sea (west-flowing). Most others flow into the Bay of Bengal (east-flowing).
- 'The Indus originates in India' — CORRECTION: The Indus originates in Tibet (Mansarovar Lake). It flows through Ladakh, India, and then into Pakistan.
- 'Godavari is the longest river in India' — CORRECTION: Ganga (2,525 km) is the longest river in India. Godavari (1,465 km) is the longest PENINSULAR river.
- 'Kolleru Lake is in Odisha' — CORRECTION: Kolleru Lake is in Andhra Pradesh (between Godavari and Krishna deltas). Chilika Lake is in Odisha.
- 'The Brahmaputra carries the smallest volume of water among Indian rivers' — CORRECTION: The Brahmaputra carries the LARGEST volume of water among Indian rivers.
9. Exam Focus
| Topic | Marks (approx.) |
|---|
| Himalayan vs Peninsular rivers comparison | 3-4 |
| Indus, Ganga, Brahmaputra — origin, length, tributaries | 4-5 |
| Peninsular rivers — Godavari, Krishna, Kaveri, Mahanadi | 4-5 |
| Lakes — location and features | 2-3 |
| River pollution and conservation | 2-3 |
| AP rivers — Godavari and Krishna deltas | 3-4 |
Key Facts for Quick Revision
- HIMALAYAN rivers: Snow-fed, PERENNIAL. PENINSULAR rivers: Rain-fed, SEASONAL.
- Largest river basin in India: Ganga (~8.6 lakh sq km).
- Longest peninsular river: Godavari (1,465 km — Dakshin Ganga).
- West-flowing peninsular rivers: Narmada, Tapi (flow into Arabian Sea).
- Largest lake in India: Wular Lake (J&K) — if by area. Chilika (Odisha) — largest brackish water.
- AP lakes: Kolleru (freshwater, Ramsar), Pulicat (brackish, AP-TN border).
10. Quick Self-Test
- Distinguish between Himalayan and Peninsular rivers (3 points). (Answer: Snow-fed vs rain-fed. Perennial vs seasonal. Long vs short. Young vs mature course.)
- Name the three river systems of the Northern Plains. (Answer: Indus, Ganga, Brahmaputra.)
- Where does the Godavari originate and why is it called Dakshin Ganga? (Answer: Triambakeshwar, Nashik. It is the longest peninsular river.)
- Which rivers flow into the Arabian Sea? (Answer: Narmada and Tapi — west-flowing. Also Indus through Pakistan.)
- Name two major lakes in Andhra Pradesh. (Answer: Kolleru Lake — freshwater, Pulicat Lake — brackish/lagoon.)
- What is the difference between a lagoon and a freshwater lake? (Answer: Lagoon is connected to the sea, brackish water. Freshwater lake has no direct sea connection, freshwater.)
- Why is the Kosi known as the 'Sorrow of Bihar'? (Answer: It causes devastating floods in Bihar due to its unstable course carrying heavy silt.)
- Name the major dam on the Krishna River in AP. (Answer: Nagarjunasagar Dam — one of the tallest masonry dams in the world.)
- What is the Polavaram Project? (Answer: A multi-purpose irrigation project on the Godavari in AP — under construction, controversial due to submergence and displacement.)
- What is the significance of the Indus Waters Treaty (1960)? (Answer: Divided the Indus rivers between India (eastern: Sutlej, Beas, Ravi) and Pakistan (western: Indus, Chenab, Jhelum).)
