Physical Geography of Bihar – Rivers, Plains, Hills, Climate and Natural Resources
Explore the Physical Geography of Bihar, including rivers, plains, hills, climate, soils, forests and natural resources that shape the state’s landscape.
Physical Geography of Bihar
Bihar, located in the eastern part of India, is one of the country’s most historically and geographically significant states. The physical geography of Bihar has played a major role in shaping its civilization, agriculture, economy, and culture. The fertile plains formed by the Ganga River and its tributaries have made Bihar one of India’s most productive agricultural regions since ancient times. The state’s landscape is characterized by vast alluvial plains, a network of perennial and seasonal rivers, low hills in the southern region, and a subtropical climate that supports diverse agricultural activities.
Covering an area of approximately 94,163 square kilometers, Bihar shares its borders with Nepal to the north, Uttar Pradesh to the west, Jharkhand to the south, and West Bengal to the east. Despite having a relatively small geographical area, Bihar possesses remarkable physical diversity that makes it an important subject in geography and general knowledge.
Table of Contents
Location and Extent
Bihar lies between 24°20’N to 27°31’N latitude and 83°19’E to 88°17’E longitude. The Tropic of Cancer does not pass through Bihar, placing the state entirely within the subtropical climatic zone.
The state is divided naturally by the Ganga River, which flows from west to east across Bihar. This river separates the state into:
- North Bihar Plain
- South Bihar Plain
Both regions differ slightly in terms of topography, drainage, and agricultural patterns.
Physiographic Divisions of Bihar
The physical landscape of Bihar can be divided into three major physiographic regions.
1. North Bihar Plain
The northern plain extends from the Nepal border to the Ganga River. It is one of the most fertile alluvial plains in India.
Key features include:
- Formed by rivers originating in the Himalayas.
- Rich alluvial soil suitable for agriculture.
- Frequent flooding during the monsoon.
- Dense river network.
- Extensive cultivation of rice, maize, sugarcane, and jute.
Major districts in this region include Muzaffarpur, Darbhanga, Sitamarhi, Supaul, Purnia, Katihar, and Madhubani.
2. South Bihar Plain
The southern plain lies between the Ganga River and the Chotanagpur Plateau.
Characteristics include:
- Slightly higher elevation than North Bihar.
- Less prone to floods.
- Presence of older alluvial soil.
- Suitable for wheat, pulses, oilseeds, and paddy cultivation.
Important districts include Patna, Nalanda, Gaya, Bhojpur, Buxar, and Nawada.
3. Southern Hills
The southern edge of Bihar contains isolated hills that are extensions of the Chotanagpur Plateau.
Major hill areas include:
- Rajgir Hills
- Kaimur Hills
- Rohtas Plateau
- Barabar Hills
These hills are composed mainly of ancient rocks and contribute to the state’s scenic beauty and biodiversity.
River System of Bihar
The river system forms the backbone of Bihar’s physical geography. Most rivers flow from north to south before joining the Ganga.
The Ganga River
The Ganga is the most important river of Bihar. It enters the state near Buxar and flows eastward before entering West Bengal.
Importance of the Ganga:
- Divides Bihar into northern and southern regions.
- Provides irrigation for agriculture.
- Supports fisheries.
- Acts as an important waterway.
- Enriches the plains with fertile alluvium.
Major Northern Rivers
Several Himalayan rivers flow through North Bihar.
These include:
- Gandak
- Kosi
- Bagmati
- Kamla
- Mahananda
- Burhi Gandak
Among these, the Kosi River is famously known as the “Sorrow of Bihar” because of its frequent floods and changing course.
Major Southern Rivers
Important rivers flowing from the southern plateau include:
- Son River
- Punpun River
- Kiul River
- Falgu River
The Son River is the largest southern tributary of the Ganga in Bihar.
Soil of Bihar
The state is blessed with fertile soils that support intensive agriculture.
New Alluvial Soil
- Found mainly in North Bihar.
- Rich in nutrients.
- Highly fertile.
- Ideal for paddy, sugarcane, maize, and vegetables.
Old Alluvial Soil
- Common in South Bihar.
- Slightly less fertile than new alluvium.
- Suitable for wheat, pulses, and oilseeds.
Sandy Soil
Occurs along riverbanks where floods deposit sand.
Clayey Soil
Found in low-lying waterlogged areas and retains moisture for long periods.
Climate of Bihar
Bihar experiences a humid subtropical climate with three distinct seasons.
Summer (March to June)
- Temperature ranges from 30°C to 45°C.
- Hot and dry weather.
- Dust storms occasionally occur.
Monsoon (June to September)
- Southwest monsoon brings most of the annual rainfall.
- Average annual rainfall ranges between 1,000 mm and 1,500 mm.
- Northern districts generally receive more rainfall than southern districts.
Winter (November to February)
- Pleasant and cool.
- Temperature ranges from 8°C to 20°C.
- Fog is common during December and January.
Natural Vegetation
Although Bihar has relatively limited forest cover, several forest types are found across the state.
Major vegetation includes:
- Tropical deciduous forests
- Sal trees
- Bamboo
- Teak
- Mahua
- Neem
- Mango
- Peepal
The largest forested regions are located in Kaimur, Rohtas, West Champaran, Banka, and Jamui districts.
Wildlife
Bihar is home to a variety of wildlife species protected in national parks and wildlife sanctuaries.
Notable wildlife includes:
- Bengal tiger
- Leopard
- Sloth bear
- Nilgai
- Deer
- Wild boar
- Crocodile
- Gangetic dolphin
- Numerous migratory birds
The Gangetic Dolphin is the State Aquatic Animal of Bihar.
Natural Resources
Compared to many Indian states, Bihar has limited mineral resources because the mineral-rich plateau became part of Jharkhand after its formation in 2000.
Available resources include:
- Limestone
- Quartz
- Sand
- Clay
- Minor stone deposits
The state’s greatest natural resource remains its fertile agricultural land and abundant water resources.
Agriculture and Physical Geography
Bihar’s geography strongly supports agriculture.
Major crops include:
- Rice
- Wheat
- Maize
- Sugarcane
- Pulses
- Mustard
- Potato
- Litchi
- Banana
- Mango
The fertile plains, adequate rainfall, and extensive river network make agriculture the backbone of Bihar’s economy.
Natural Hazards
The state’s geography also exposes it to several natural hazards.
Floods
North Bihar experiences severe flooding almost every year due to rivers like:
- Kosi
- Gandak
- Bagmati
- Kamla
Drought
Some southern districts occasionally face drought due to uneven rainfall.
Riverbank Erosion
Continuous erosion affects agricultural land and settlements along major rivers.
Importance of Physical Geography of Bihar
The physical geography of Bihar influences every aspect of life in the state. The fertile plains support millions of farmers, while rivers provide irrigation, drinking water, transportation, and fisheries. The hills contribute to biodiversity, tourism, and environmental balance. Climate determines cropping patterns and agricultural productivity, making geography a vital component of Bihar’s economy and development.
Understanding Bihar’s physical geography also helps explain the state’s historical significance. Ancient civilizations flourished here because of fertile land and reliable water sources. Even today, geographical features continue to shape settlement patterns, transportation, industries, and economic activities across the state.
Summary
The physical geography of Bihar is defined by its fertile alluvial plains, mighty rivers, isolated hills, subtropical climate, and rich agricultural landscape. The Ganga River serves as the lifeline of the state, while the Himalayan tributaries enrich the northern plains with fertile soil. Despite facing challenges such as floods and limited mineral resources, Bihar’s geographical features have made it one of India’s most important agricultural regions. A clear understanding of Bihar’s physical geography provides valuable insight into its natural environment, economic development, and historical importance.
Also Check: Bihar GK
