BPSC Bihar Geography Complete Notes: River Systems, Agro-Climatic Zones, Minerals & Forest Survey
Definitive Bihar Geography revision notes for 72nd BPSC Prelims. Ganga river basin and north/south tributaries (Ghaghara, Gandak, Kosi, Son, Punpun), soil classifications, 3 agro-climatic zones, minerals in southern plateau, and ISFR Forest Survey.
1. Bihar Physiographic Divisions & Spatial Extent
Bihar occupies an area of 94,163 sq km (2.86% of India's total geographic area), ranking 12th in size and 3rd in population.
The state is geographically partitioned into three distinct physiographic realms:
1. Terai / Sub-Himalayan Foothills (Shivalik Range): Confined to West Champaran district (Someshwar range, highest peak Someshwar Fort at 880 meters).
2. The Great Bihar Alluvial Plains: Constitutes roughly 95% of the state's surface, bisected from west to east by the holy River Ganga into North Bihar Plains and South Bihar Plains.
3. Southern Plateau / Marginal Hills: Ancient Precambrian granite and gneiss formations spanning Kaimur, Rohtas, Gaya, Nawada, Jamui, and Banka along the Jharkhand border.
2. The Lifeline River Ganga & North / South Drainage Systems
River Ganga enters Bihar at Chausa (Buxar district) and departs the state at Manihari (Katihar district). It flows for 445 km through 12 Bihar districts (Patna has the longest stretch at 99 km).
| River Name | Origin / Source | Bank of Confluence | Confluence Point with Ganga | Key Characteristics |
|---|---|---|---|---|
| Ghaghara (Saryu) | Gurla Mandhata peak (Tibet) | North (Left) Bank | Doriganj (Saran / Chapra) | Forms border between Bihar and UP |
| Gandak (Narayani) | Dhaulagiri (Nepal Himalayas) | North (Left) Bank | Pahleza Ghat (Near Hajipur / Sonepur) | Source of Triveni Canal system |
| Burhi Gandak | Someshwar Hills (Chautarwa Chaur) | North (Left) Bank | Khagaria district | Fastest flowing river of North Bihar |
| Bagmati | Shivpuri Range (Nepal) | North (Left) Bank | Joins Kosi near Badlaghat | Notorious for devastating flash floods |
| Kosi (Sorrow of Bihar) | Triveni / Saptakoshi (Nepal) | North (Left) Bank | Kursela (Katihar district) | Known for radical channel shifting (210 km shift in 250 yrs) |
| Mahananda | Darjeeling Hills (West Bengal) | North (Left) Bank | Godagiri (Nawabganj, Bangladesh) | Easternmost northern tributary of Ganga in Bihar |
| Son | Amarkantak Plateau (MP) | South (Right) Bank | Near Maner (Danapur, Patna) | Main southern tributary; Son Canal built in 1874 |
| Punpun | Palmu district (Jharkhand) | South (Right) Bank | Fatuha (Patna district) | Sacred river for Pind Daan rituals |
| Phalgu (Niranjana) | Formed near Bodh Gaya by Lilajan & Mohana | South (Right) Bank | Disappears in Tal region near Ganga | Gayaji Dam (India's longest rubber dam) built over it |
| Karmanasa | Kaimur Hills | South (Right) Bank | Chausa (Buxar) | Considered inauspicious; forms Bihar-UP southern boundary |
3. Soil Profiles & 3 Agro-Climatic Zones of Bihar
• Agro-Climatic Zone I (North-West Alluvial): 13 districts (Champaran, Saran, Siwan, Muzaffarpur, Darbhanga). Average rainfall 1040–1450 mm. Major crops: Paddy, wheat, sugarcane, maize.
• Agro-Climatic Zone II (North-East Alluvial): 8 districts (Purnea, Katihar, Saharsa, Kishanganj). High rainfall (1200–1700 mm). Major crops: Jute, makhana, maize.
• Agro-Climatic Zone III (South Bihar Alluvial): Divided into IIIA (South-East: Bhagalpur, Munger, Banka) and IIIB (South-West: Patna, Nalanda, Rohtas, Bhojpur, Gaya). Lowest rainfall (990–1200 mm). High pulse and oilseed concentration.
• Distinct Soils: Karail-Kewal soil (heavy clayey soil found in South Bihar plains ideal for rabi crops), Balal soil (coarse sandy soil of Kaimur-Rohtas), and Tal soil (submerged land along the southern bank of Ganga from Fatuha to Lakhisarai).
4. Mineral Resources in Bihar's Southern Plateau
Following Jharkhand's bifurcation in 2000, Bihar retained vital mineral deposits concentrated along its southern districts:
• Pyrites: Rohtas district (Amjhore) holds 95% of India's total pyrite reserves.
• Limestone: Rohtas and Kaimur districts supply major cement industrial clusters (Banjari, Dalmianagar).
• Mica: Nawada, Jamui, and Gaya districts represent the northern fringe of the Chota Nagpur mica belt.
• Gold Reserves: Karmatia and Sonu regions in Jamui district house estimated 44% of India's prospective primary gold ore reserves according to the Geological Survey of India (GSI).
• Quartzite & Silica Sand: Abundantly quarried in Munger and Nalanda.
5. India State of Forest Report (ISFR) Bihar Data
Based on the India State of Forest Report (ISFR):
• Total Forest Cover: 7,380.79 sq km, representing 7.84% of Bihar's geographical area.
• Tree Cover: 2,341 sq km (2.48% of geographical area). Total Forest + Tree cover = 10.32%.
• District with Maximum Forest Cover (Area): Kaimur (1,051.56 sq km), followed by West Champaran and Rohtas.
• District with Maximum Forest Percentage: Kaimur (31.56%), followed by Jamui (21.34%) and Nawada (20.72%).
• District with Minimum Forest Area & Percentage: Sheikhpura (only 1.19 sq km, 0.17%).
• Valmiki National Park: Located in West Champaran, it remains Bihar's only National Park and Tiger Reserve (Kaimur Wildlife Sanctuary notified as the state's 2nd tiger reserve).