In this guide
For Bihar, rivers are everything — the source of its fertile soil, the highways of its ancient trade, the sites of its holiest rituals, and the cause of its most devastating disasters. At the centre is the Ganga, which crosses the state from west to east. Its tributaries from the Himalaya bring water and silt — and floods; its tributaries from the plateau are seasonal and gentler.
The Ganga in Bihar
- The Ganga enters Bihar near Chausa (Buxar district), where the Karmanasa meets it at the Bihar–UP border.
- It flows eastward past Buxar, Patna, Mokama, Munger and Bhagalpur, and leaves Bihar near Kahalgaon / the Rajmahal hills towards Jharkhand and West Bengal.
- It divides Bihar into north Bihar and south Bihar.
- Major bridges include the Mahatma Gandhi Setu (Patna–Hajipur), the Rajendra Setu (Mokama, rail-cum-road) and the Vikramshila Setu (Bhagalpur).
North bank tributaries (from the Himalaya)
These rivers are perennial, fed by rain and snowmelt, carry heavy sediment and cause floods.
| River | Origin | Course / notes |
|---|---|---|
| Ghaghara | Tibet / Nepal Himalaya | Joins the Ganga near Chhapra; forms part of the Bihar–UP border |
| Gandak (Narayani) | Nepal Himalaya | Enters Bihar at Valmikinagar; joins the Ganga at Hajipur (opposite Patna); Sonepur at the confluence |
| Burhi Gandak | Near Someshwar hills, West Champaran | Flows parallel to the Gandak through Muzaffarpur, Samastipur; joins the Ganga near Munger |
| Bagmati | Nepal (near Kathmandu) | Flows through Sitamarhi, Muzaffarpur, Darbhanga; flood-prone |
| Kamla | Nepal | Flows through Madhubani and Darbhanga |
| Kosi | Nepal Himalaya (Sapta Kosi — seven streams) | Enters near Bhimnagar; notorious for shifting course and floods; joins the Ganga near Kursela (Katihar) |
| Mahananda | Darjeeling Himalaya | Flows through Kishanganj, Purnia, Katihar, then Malda (West Bengal); joins the Ganga (Padma) at Godagari in Bangladesh |
South bank tributaries (from the plateau)
These rivers are mostly seasonal, carry less sediment and are shorter.
| River | Origin | Course / notes |
|---|---|---|
| Karmanasa | Kaimur hills | Forms the Bihar–UP boundary; joins the Ganga near Chausa |
| Son | Amarkantak (Madhya Pradesh) | The largest south-bank tributary; joins the Ganga near Patna (west of the city); Indrapuri barrage at Dehri-on-Sone feeds the Son canal system |
| Punpun | Chotanagpur plateau | Joins the Ganga near Fatuha (Patna) |
| Phalgu | Formed by the Lilajan (Niranjana) and Mohana | Flows past Gaya and Bodh Gaya; sacred for pind daan; mostly dry, with water flowing under its sandy bed |
| Kiul | Chotanagpur plateau | Joins the Ganga near Surajgarha (Lakhisarai) |
| Chandan | Jharkhand | Flows through Banka and Bhagalpur |
Barrages and projects
| Project | River | Notes |
|---|---|---|
| Kosi barrage | Kosi | At Bhimnagar (on the Indo-Nepal border); built under the Kosi Agreement (1954) with Nepal |
| Gandak barrage | Gandak | At Valmikinagar; built under the Gandak Agreement (1959) with Nepal |
| Indrapuri barrage | Son | At Dehri-on-Sone; feeds the Son canal system, one of the oldest irrigation systems in the region |
| Farakka barrage | Ganga | In West Bengal, downstream of Bihar; Bihar has long argued that it increases siltation and flooding upstream |
| Kosi–Mechi link | Kosi–Mechi | A proposed river-linking project to divert Kosi water to the Mahananda basin |
The Vikramshila Gangetic Dolphin Sanctuary
- A stretch of the Ganga near Bhagalpur (from Sultanganj to Kahalgaon) is protected as the Vikramshila Gangetic Dolphin Sanctuary — the only sanctuary in India dedicated to the Gangetic river dolphin.
- The Gangetic dolphin is India's national aquatic animal (declared in 2009).
- The National Dolphin Research Centre has been set up in Patna.
Problems
| Problem | Explanation |
|---|---|
| Floods | North Bihar floods almost every year (see our guide on the Kosi and on disasters) |
| Siltation | Himalayan rivers deposit silt, raising beds; embankments trap silt between them |
| Shifting courses | The Kosi has shifted westward by over a hundred kilometres over two centuries |
| Pollution | Untreated sewage from towns into the Ganga; the Namami Gange programme addresses this |
| Water-sharing and cooperation | Many rivers originate in Nepal; flood management depends on cooperation |
| Seasonality | South Bihar rivers dry up in summer, causing water scarcity |
Rivers and culture
- Chhath is celebrated on riverbanks.
- Sonepur Mela — at the Gandak–Ganga confluence.
- Gaya — rituals on the Phalgu.
- Bodh Gaya — on the Niranjana.
Practice
Prelims-style:
- Where does the Gandak meet the Ganga?
- Where is the Kosi barrage?
- Which river flows past Gaya and Bodh Gaya?
- Where is the Vikramshila Gangetic Dolphin Sanctuary?
- Where does the Son originate?
Mains-style:
- Compare the characteristics of the north and south bank tributaries of the Ganga in Bihar.
- "Bihar's rivers are its lifeline and its peril." Discuss.
Map exercise
Draw the Ganga across Bihar and mark all the tributaries, the Kosi and Gandak barrages, the Indrapuri barrage, the dolphin sanctuary, and the towns of Buxar, Patna, Hajipur, Munger, Bhagalpur and Gaya.
A note on dates and numbers. Exam patterns, vacancies and schedules change from year to year. Always confirm the current details in the latest notification on the Bihar Public Service Commission website .
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