
Complete Geography Notes on Major River system of Bihar for BPSC and Other Competitive Exams in 2025
Geography-4
Here’s a comprehensive and detailed explanation of the topic “Major River System of Bihar” aligned with the BPSC Prelims Syllabus. This includes the Ganga River, its northern and southern tributaries, as well as river basins and flood-prone areas.
Major River System of Bihar
Bihar is a riverine state with the Ganga River as its lifeline. The state is crisscrossed by several rivers, which are broadly categorized as:
- Northern tributaries (originating in the Himalayas, prone to floods)
- Southern tributaries (originating in the Chotanagpur Plateau, mostly seasonal)
A. The Ganga River – The Main River of Bihar
Key Details:
- Enters Bihar: Near Chausa, Buxar district
- Exits Bihar: Near Manihari, Katihar district
- Length in Bihar: ~445 km
- Flow Direction: West to East
- Divides Bihar into:
- North Bihar – flood-prone, fertile
- South Bihar – drier, old alluvium plains
Importance:
- Supports agriculture, inland navigation, drinking water, and hydroelectric power.
- Receives both Himalayan (perennial) and Peninsular (seasonal) tributaries.
B. Northern Tributaries (from the Himalayas)
Originating from Nepal, these rivers are perennial and flood-prone.
1. Gandak River
- Origin: Nepal Himalayas (Dhaulagiri range)
- Enters Bihar: West Champaran district
- Joins Ganga: Near Hajipur (Vaishali)
- Known as: Narayani in Nepal
- Features: Causes floods in East & West Champaran, Gopalganj, Saran
- Gandak Canal System: Important for irrigation
2. Burhi Gandak River
- Origin: Chautarwa Chaur, West Champaran
- Flow Path: Passes through Muzaffarpur, Samastipur, Begusarai
- Joins Ganga: Near Khagaria
- Features: Runs parallel to Gandak; known for causing waterlogging and floods
3. Kosi River
- Origin: Tethys Himalayas, Nepal
- Entry into Bihar: Supaul District
- Joins Ganga: Near Kursela (Katihar)
- Also Called: “Sorrow of Bihar” – due to frequent course changes and floods
- Tributaries: Arun, Tamor, Sun Kosi (in Nepal)
- Kosi Project: Dams and embankments built to control flooding
4. Bagmati River
- Origin: Kathmandu Valley, Nepal
- Entry into Bihar: Sitamarhi district
- Joins Kosi: Near Khagaria
- Flood-Prone Districts: Sitamarhi, Darbhanga, Muzaffarpur
- Features: Unpredictable river; often breaches embankments
5. Kamla-Balan River
- Origin: Mahabharat range, Nepal
- Entry into Bihar: Madhubani district
- Joins Bagmati
- Features: Short but highly flood-prone
6. Mahananda River
- Origin: Darjeeling hills (West Bengal)
- Enters Bihar: Through Kishanganj district
- Joins Ganga: Near Manihari (Katihar)
- Features: Important for northeast Bihar; less flood-prone than others
C. Southern Tributaries (from the Chotanagpur Plateau)
These rivers are seasonal, rain-fed, and flow northward into the Ganga.
1. Sone (Son) River
- Origin: Amarkantak Plateau, Madhya Pradesh
- Flow Path: Through Rohtas, Aurangabad, Arwal
- Joins Ganga: Near Maner (Patna)
- Features:
- Second-largest southern tributary after Yamuna
- Wide riverbed, often dry in non-monsoon seasons
- Sone Canal System – a major irrigation project
2. Punpun River
- Origin: Palamu Plateau (Jharkhand)
- Flow Path: Through Gaya, Jehanabad, Patna
- Joins Ganga: Near Fatuha (Patna)
- Features: Flash floods in monsoon, dry otherwise
3. Phalgu (Falgu) River
- Origin: Confluence of Lilajan and Mohana rivers near Bodh Gaya
- Passes through: Gaya
- Joins Punpun
- Religious significance: Pitru Paksha rituals at Vishnupad Temple in Gaya
4. Karmanasha River
- Origin: Kaimur Hills, Sonbhadra (UP)
- Flows along: Bihar–UP border
- Joins Ganga: Near Chausa (Buxar)
- Mythological Reference: Believed to be inauspicious, hence the name “Destroyer of Karma”
D. River Basins and Flood-Prone Areas
Major River Basins in Bihar:
Basin | Major Rivers | Districts Covered |
Ganga Basin | Ganga + all tributaries | All central districts |
Kosi Basin | Kosi, Bagmati, Kamla-Balan | Supaul, Saharsa, Madhepura, Khagaria |
Gandak Basin | Gandak, Burhi Gandak | West Champaran, Gopalganj, Muzaffarpur |
Sone Basin | Sone, Punpun, Phalgu | Rohtas, Aurangabad, Gaya, Patna |
Flood-Prone Areas
- Districts Severely Affected Annually:
- North Bihar: Supaul, Saharsa, Madhepura, Darbhanga, Muzaffarpur, Sitamarhi, Khagaria, Purnia
- Causes:
- Rivers entering from Nepal with heavy monsoonal discharge
- Riverbed siltation
- Breaching of embankments
- Projects for Control:
- Kosi Project
- Gandak Barrage
- Embankment schemes
Quick Reference Table: Major River System of Bihar
River | Origin | Joins | Flood-Prone? | Region |
Ganga | Gangotri (Uttarakhand) | Flows E across Bihar | Moderate | Central Bihar |
Gandak | Nepal (Dhaulagiri) | Ganga at Hajipur | Yes | North |
Burhi Gandak | West Champaran | Ganga at Khagaria | Yes | North |
Kosi | Nepal | Ganga at Kursela | Highly | North |
Bagmati | Nepal | Kosi | Yes | North |
Kamla-Balan | Nepal | Bagmati | Yes | North |
Mahananda | Darjeeling | Ganga at Manihari | Low | NE Bihar |
Sone | MP (Amarkantak) | Ganga at Maner | No | South |
Punpun | Jharkhand | Ganga at Fatuha | Yes (flash) | South |
Phalgu | Gaya | Punpun | Low | South |
Karmanasha | UP | Ganga at Buxar | Low | SW Bihar |

Law of motion