Book: India: Physical Environment | Chapter 3
Drainage System
1. Learning Objectives
After reading these notes, you will be able to:
1
Explain what drainage, drainage system, catchment area, and watershed mean.2
Identify the four types of drainage patterns with examples.3
Classify Indian drainage on the basis of direction, size, and origin.4
Describe the features and major rivers of the Himalayan drainage system.5
Describe the Peninsular drainage system and compare it with Himalayan rivers.2. Introduction
During the rainy season, water flows through rivers, nalas, and channels — draining away excess water to prevent flooding. Drainage means the flow of water through well-defined channels. The network of such channels is called a Drainage System. The drainage pattern of an area depends on geological history, rock structure, topography, slope, and the amount of water flowing.
- Catchment Area: The specific area from which a river collects its water.
- Drainage Basin: The entire area drained by a river and all its tributaries together.
- Watershed: The boundary line separating one drainage basin from another. Watersheds are small in area; river basins are large.
- Rivers can be Perennial (water all year round) or Ephemeral (water only in rainy season).
- River basins and watersheds are treated as the best units for micro, meso, or macro planning because what happens in one part affects the whole basin.
🗺️ Mind Map — Types of Drainage Patterns
Drainage Patterns🌳 Dendritic
Like tree branches
Ex: Northern Plains rivers
Like tree branches
Ex: Northern Plains rivers
🌸 Radial
From hill → all directions
Ex: Amarkantak range
From hill → all directions
Ex: Amarkantak range
🔲 Trellis
Parallel rivers + right-angle
secondary tributaries
Parallel rivers + right-angle
secondary tributaries
🎯 Centripetal
All rivers flow inward
into a lake/depression
All rivers flow inward
into a lake/depression
3. Drainage Systems of India
📌 A — Based on Direction of Flow (Towards Sea)
- Bay of Bengal Drainage — 77% of total drainage area. Includes: Ganga, Brahmaputra, Mahanadi, Krishna, etc.
- Arabian Sea Drainage — 23% of total drainage area. Includes: Indus, Narmada, Tapi, Mahi, Periyar.
- The water divide between the two is formed by: Delhi Ridge → Aravali → Sahyadri (Western Ghats).
📌 B — Based on Size of Catchment Area
Three Categories
Major Basins — More than 20,000 sq. km (14 basins: Ganga, Brahmaputra, Krishna, Narmada, Tapi, etc.)Medium Basins — 2,000–20,000 sq. km (44 basins: Kalindi, Periyar, Meghna, etc.)
Minor Basins — Less than 2,000 sq. km (rivers in low rainfall areas)
📌 C — Based on Origin (Most Used Classification)
- Himalayan Drainage — younger rivers; perennial; include Ganga, Indus, Brahmaputra systems.
- Peninsular Drainage — older rivers; mostly non-perennial; include Godavari, Krishna, Kaveri, Narmada, etc.
4. The Himalayan Drainage
💡 Key Features
Himalayan rivers are perennial — fed by both glacial melt and rainfall. They pass through giant gorges carved during the uplift of the Himalayas and form V-shaped valleys, ox-bow lakes, flood plains, braided channels, and deltas.- In mountain areas, the rivers have a tortuous (winding) course; in plains, they develop a strong meandering tendency and frequently change their course.
- River Kosi — called the “Sorrow of Bihar”. It brings huge sediment from upper reaches → blocks its own course → floods and changes direction repeatedly.
- Damodar — formerly the “Sorrow of Bengal”, now tamed by the Damodar Valley Corporation (DVC).
🌍 Evolution of the Himalayan Drainage
- Geologists believe an ancient river called Shiwalik or Indo-Brahma once flowed across the entire Himalaya from Assam to Punjab, draining into the Gulf of Sind (Miocene period, 5–24 million years ago).
- Due to Pleistocene upheaval, this river was split into three: (i) Indus system (west) (ii) Ganga system (centre) (iii) Brahmaputra system (east).
- The Potwar Plateau (Delhi Ridge) uplift acted as the water divide between Indus and Ganga.
5. The River Systems of the Himalayan Drainage
🔵 The Indus System
- One of the largest river basins in the world — total length 2,880 km (1,114 km in India).
- Originates near Bokhar Chu glacier, Kailash range, Tibet (4,164 m). Called ‘Singi Khamban’ (Lion’s mouth) in Tibet.
- Flows through Ladakh, Baltistan → enters Pakistan near Chilas → discharges into Arabian Sea east of Karachi.
- Five rivers of Punjab (Panjnad): Satluj, Beas, Ravi, Chenab, Jhelum — all join the Indus.
🔵 Jhelum
- Rises from Verinag spring (foot of Pir Panjal), Kashmir
- Flows through Srinagar & Wular Lake
- Joins Chenab near Jhang, Pakistan
🟢 Chenab
- Largest tributary of Indus
- Formed by Chandra + Bhaga at Tandi — also called Chandrabhaga
- Flows 1,180 km before entering Pakistan
🟡 Beas & Ravi
- Beas: Originates from Beas Kund near Rohtang Pass (4,000 m); meets Satluj at Harike
- Ravi: Rises west of Rohtang Pass; drains between Pir Panjal and Dhauladhar
🟠 Satluj
- Originates from Raksas tal near Mansarovar, Tibet (4,555 m)
- An antecedent river
- Feeds the Bhakra Nangal canal system
🟠 The Ganga System
- Most important river — basin + cultural significance. Length: 2,525 km; Basin area: 8.6 lakh sq. km.
- Rises in Gangotri glacier near Gaumukh (3,900 m), Uttarakhand — known as Bhagirathi here.
- At Devprayag, Bhagirathi meets Alaknanda → becomes Ganga. Enters plains at Haridwar.
- Discharges into Bay of Bengal near Sagar Island.
📌 Key Left Bank Tributaries of Ganga
Yamuna (longest, from Yamunotri glacier, meets at Prayag) · Ramganga · Gomati · Ghaghara · Gandak (Nepal, joins at Sonpur, Patna) · Kosi (antecedent, “Sorrow of Bihar”) · Mahananda (last left bank tributary, West Bengal)
Right bank: Son (major, from Amarkantak) · Chambal (famous for ravines, from Malwa plateau, MP)
🔷 The Brahmaputra System
- One of the largest rivers in the world. Originates from Chemayungdung glacier, Kailash range near Mansarovar lake.
- Flows eastward ~1,200 km in Tibet — called Tsangpo (meaning ‘the purifier’). Enters India as Siang / Dihang in Arunachal Pradesh.
- After receiving Dibang and Lohit rivers → becomes Brahmaputra in Assam.
- Enters Bangladesh near Dhubri → called Jamuna → merges with Padma → Bay of Bengal.
- Famous for floods, channel shifting, and bank erosion due to heavy rainfall and large, sediment-heavy tributaries.
6. The Peninsular Drainage System
The Peninsular drainage is older than the Himalayan drainage, evident from its broad, shallow, graded valleys. Most major Peninsular rivers flow west to east and drain into the Bay of Bengal. Exceptions are Narmada and Tapi, which flow into the Arabian Sea through rift valleys.
- Western Ghats act as the main water divide between Bay of Bengal rivers and small rivulets joining the Arabian Sea.
- Peninsular rivers have fixed course, no meanders, non-perennial flow (except Kaveri, Narmada, Tapi).
- Three geological events shaped Peninsular drainage: (i) Subsidence of western flank below the sea; (ii) Himalayan upheaval + trough faulting (Narmada & Tapi flow in rift valleys); (iii) Tilting of the Peninsula NW → SE, orienting rivers towards Bay of Bengal.
🌊 River Systems of the Peninsular Drainage
🟢 Godavari
- Largest Peninsular river — called Dakshin Ganga
- Rises in Nasik, Maharashtra
- Length: 1,465 km | Basin: 3.13 lakh sq. km
- Discharges into Bay of Bengal
🔵 Krishna
- Second largest east-flowing river
- Rises near Mahabaleshwar, Sahyadri
- Length: 1,401 km
- Major tributaries: Koyna, Tungbhadra, Bhima
🟡 Kaveri
- Rises in Brahmagiri hills (1,341 m), Karnataka
- Carries water throughout the year — upper: SW monsoon; lower: NE monsoon
- 56% basin in Tamil Nadu, 41% in Karnataka
🔴 Narmada
- Originates from Amarkantak plateau (1,057 m)
- Flows in a rift valley between Satpura and Vindhyan ranges
- Forms Dhuandhar waterfall near Jabalpur
- Length: 1,312 km → Arabian Sea. Sardar Sarovar Project on this river
🟣 Tapi
- Originates from Multai, Betul district (MP)
- Flows in a rift valley — another exception
- Length: 724 km → Arabian Sea
🟠 Mahanadi & Luni
- Mahanadi: Rises near Sihawa, Chhattisgarh; 851 km; Bay of Bengal
- Luni: Largest river of Rajasthan (west of Aravali); ephemeral; joins Rann of Kuchchh
7. Himalayan vs Peninsular Rivers — Key Differences
| Feature | 🏔️ Himalayan Rivers | 🌿 Peninsular Rivers |
|---|---|---|
| Origin | Himalayan glaciers & snowfields | Western Ghats / Central highlands |
| Age | Younger | Older |
| Water Flow | Perennial (all year) | Mostly non-perennial |
| Valley | Deep gorges, V-shaped valleys | Broad, shallow, graded |
| Course | Tortuous → meanders | Fixed, no meanders |
| Flow Direction | Mostly east → Bay of Bengal | West to east (exceptions: Narmada, Tapi) |
| Deposition | Form large deltas | Narmada & Tapi form estuaries |
8. Extent of Usability of River Water
- India’s rivers carry huge water but distribution is uneven in time and space.
- In rainy season, much water is wasted in floods; when one part floods, another part has drought.
- Solution: Inter-basin transfer — moving surplus water to deficit basins through canals.
⚠️ Key Problems in Using River Water
(i) Insufficient quantity | (ii) River water pollution | (iii) High silt load(iv) Uneven seasonal flow | (v) Inter-state disputes | (vi) Shrinking of channels due to encroachment
✅ Important Schemes & Programmes
Namami Gange Programme (2014) — Flagship scheme for cleaning, conserving, and rejuvenating the Ganga. Pillars: Sewerage Treatment, River-Front Development, Bio-Diversity, Afforestation, Public Awareness, Ganga Gram.Namami Devi Narmade — Narmada river conservation mission.
Inter-Basin Examples: Periyar Diversion · Indira Gandhi Canal · Kurnool-Cuddapah Canal · Beas-Satluj Link · Ganga-Kaveri Link
Summary — Quick Revision
1
Drainage = water flowing through well-defined channels. Network = Drainage System. Depends on geology, topography, slope, and rainfall.
2
4 drainage patterns: Dendritic (tree-like) · Radial (from hill) · Trellis (right angles) · Centripetal (into depression).
3
77% of India’s drainage flows to Bay of Bengal; 23% to Arabian Sea. Divide = Delhi Ridge + Aravali + Sahyadri.
4
Himalayan rivers are perennial, fed by glaciers + rain. They meander in plains, form deltas. Ancient river Indo-Brahma split into Indus, Ganga, Brahmaputra.
5
Kosi = “Sorrow of Bihar”; Damodar = formerly “Sorrow of Bengal” (tamed by DVC). Both notorious for floods.
6
Ganga (2,525 km) — most important; rises at Gangotri. Brahmaputra — rises near Mansarovar; called Tsangpo in Tibet, Jamuna in Bangladesh.
7
Peninsular rivers are older, have fixed course, no meanders, mostly non-perennial. Western Ghats = water divide.
8
Godavari = largest Peninsular river (Dakshin Ganga). Kaveri is unique — carries water all year due to two monsoon seasons.
9
Narmada & Tapi are exceptions — they flow in rift valleys, westward into Arabian Sea, and form estuaries, not deltas.
10
River water is unevenly distributed → floods + drought simultaneously. Solution: better management, inter-linking of rivers, and conservation schemes like Namami Gange.
Important Terms to Remember
- Drainage: Flow of water through well-defined channels.
- Drainage System: Network of channels (river + tributaries) that drain a region.
- Catchment Area: Specific area from which a single river collects water.
- Drainage Basin: Area drained by a river and all its tributaries. Larger than a watershed.
- Watershed: The boundary line separating two drainage basins. Smaller than a river basin.
- Perennial River: River that carries water throughout the year (fed by glaciers + rain). E.g., Ganga.
- Ephemeral River: River that has water only during the rainy season. E.g., Luni.
- Antecedent River: A river that is older than the mountains it crosses — it carved its course before the mountains rose. E.g., Satluj, Kosi.
- Rift Valley: A valley formed by faulting (land sinking between two faults). Narmada and Tapi flow through rift valleys.
- Estuary: A funnel-shaped river mouth where fresh water meets the sea — no delta is formed. E.g., Narmada.
- Delta: A fan-shaped deposition at the river mouth formed when a river deposits sediment before meeting the sea. E.g., Ganga-Brahmaputra delta.
- Meander: A curve or loop in a river’s path, formed in plains where rivers swing from side to side.
- Ox-bow Lake: A lake formed when a river meander gets cut off from the main river.
- Panjnad: The name given to the five rivers of Punjab — Satluj, Beas, Ravi, Chenab, Jhelum — that join the Indus.
- Tsangpo: Name of the Brahmaputra in Tibet, meaning ‘the purifier’.