Rivers of Bihar: Drainage System, Ganga Tributaries, Kosi, Gandak & Son
Comprehensive geography guide to the river systems of Bihar. Course of the Ganga (445 km in Bihar), North Himalayan tributaries (Ghaghra, Gandak, Bagmati, Kosi, Mahananda), and South Peninsular rivers (Karmnasa, Son, Punpun, Falgu).
1. The Ganga: Master Drainage Stream of Bihar
The Ganga river traverses 445 km across Bihar, dividing the state into North Bihar Plain and South Bihar Plain. It enters Bihar at Chausa (Buxar district) and exits near Sahebganj (Jharkhand border) passing through 12 Bihar districts: Buxar, Bhojpur, Saran, Patna, Vaishali, Samastipur, Begusarai, Lakhisarai, Munger, Khagaria, Bhagalpur, and Katihar.
Patna district records the longest shoreline along the Ganga river (~99 km).
| River | Origin Location | Entry in Bihar | Confluence with Ganga | Perennial / Seasonal |
|---|---|---|---|---|
| Ghaghra (Saryu) | Gurla Mandhata peak (Tibet) | Gopalganj | Near Revelganj / Chhapra | Perennial (Himalayan) |
| Gandak | Narayani / Saligrami (Nepal) | Valmikinagar (West Champaran) | Pahleja Ghat (near Sonpur/Hajipur) | Perennial (Himalayan) |
| Burhi Gandak | Someshwar Hills (W. Champaran) | Chautarwa (W. Champaran) | Near Khagaria | Perennial (High silt load) |
| Kosi | Saptakoshi (Nepal/Tibet) | Near Birpur (Supaul) | Kursela (Katihar district) | Perennial ("Sorrow of Bihar") |
| Mahananda | Mahaldiram Hills (Darjeeling) | Kishanganj | Malda (West Bengal boundary) | Perennial (Easternmost tributary) |
| Son | Amarkantak Plateau (MP) | Rohtas district | Near Maner / Danapur (Patna) | Seasonal (Rainfed plateau) |
| Punpun | Chhota Nagpur Plateau (Palamu) | Gaya district | Fatuha (Patna district) | Seasonal (Sacred river) |
| Falgu (Niranjana) | Formed near Bodh Gaya | Gaya district | Tal region (Mohane confluence) | Seasonal (Pitrapaksha rites) |
2. Kosi River ("Sorrow of Bihar") & Channel Shifting
The Kosi river is notorious for its rapid course shifting, having migrated over 120 km westward across North Bihar over the past two centuries due to extreme sediment deposition from the young fold Himalayas.
BPSC consistently tests Kosi entry point (Supaul), confluence point (Kursela in Katihar), and barrage location (Bhimnagar).