Bihar, a state in eastern India, is rich in groundwater resources due to its geographic location in the fertile Indo-Gangetic plains. Groundwater plays a crucial role in meeting the water demands for agriculture, domestic use, and industry. However, these resources are under pressure from over-extraction, pollution, and climatic changes.

Key Features of Groundwater in Bihar

1. Geographical Context:
   • Bihar is divided into two major regions:
     • North Bihar Plains: Comprising fertile alluvial plains formed by rivers like the Ganga, Kosi, Gandak, and Bagmati.
     • South Bihar Plateau: A region with hard rock formations and limited groundwater availability.
   • Total geographical area: 94,163 sq. km.
2. Groundwater Aquifers:
   • The state predominantly has alluvial aquifers in the plains.
   • In the plateau regions, groundwater is stored in fractured and weathered rock formations.
   • Aquifers are classified as:
     • Shallow Aquifers: Found at depths of 5–50 meters.
     • Deep Aquifers: Found at depths beyond 50 meters, often used for irrigation and urban water supply.

Availability of Groundwater in Bihar

1. Recharge Potential:

   • Annual rainfall: 1,000–1,500 mm, with high variability.
   • Rainwater infiltration and river recharge contribute significantly to groundwater reserves.

2. Estimated Groundwater Resources (CGWB Data, Approximate):

   • Total Annual Replenishable Groundwater: ~29.19 billion cubic meters (BCM).
   • Net Annual Groundwater Availability: ~27 BCM.
   • Groundwater Draft (Utilization): ~13–15 BCM (varies by year).
   • Groundwater Development (Utilization as % of Availability): ~45–50%, indicating moderate exploitation.

3. Regional Variations:

   • North Bihar: Higher groundwater availability due to abundant alluvial deposits and river recharge.
   • South Bihar: Limited resources due to hard rock terrain and lower rainfall.

Uses of Groundwater in Bihar

1. Agriculture:

   • Bihar's economy heavily depends on agriculture.
   • Groundwater is the primary source for irrigation, especially during the Rabi and Kharif seasons.
   • Popular irrigation systems include tube wells and hand pumps.

2. Domestic Use:

   • Most rural and urban households rely on groundwater for drinking and domestic purposes.

3. Industrial Use:

   • Industries, especially sugar, leather, and food processing, utilize groundwater extensively.

Challenges in Groundwater Management

1. Over-Exploitation:

   • High dependency on groundwater for irrigation leads to over-extraction in some districts.

2. Pollution:

   • Arsenic Contamination: Found in groundwater in districts like Patna, Bhojpur, Bhagalpur, and Samastipur.
   • Fluoride Contamination: Detected in parts of Gaya and Nawada.
   • Nitrate Pollution: Due to agricultural runoff and improper waste disposal.
   • Iron Contamination: Common across several districts, affecting drinking water quality.

3. Waterlogging:

   • Areas in North Bihar suffer from waterlogging due to poor drainage and excessive irrigation.

4. Declining Water Tables:

   • Urban areas like Patna are witnessing a gradual decline in groundwater levels due to over-extraction and urbanization.

Steps for Sustainable Groundwater Management

1. Rainwater Harvesting:

   • Promote rooftop rainwater harvesting in urban areas.
   • Develop recharge structures in rural and semi-urban regions.

2. Irrigation Efficiency:

   • Encourage efficient irrigation techniques like drip and sprinkler systems to reduce groundwater use.

3. Pollution Control:

   • Implement stricter regulations for industrial effluents and agricultural chemicals.
   • Provide safe drinking water through treatment plants in arsenic and fluoride-affected areas.

4. Public Awareness:

   • Conduct awareness campaigns about sustainable water use and pollution prevention.

5. Government Initiatives:

   • Programs like the Jal-Jeevan-Hariyali Mission focus on water conservation and recharging groundwater in Bihar.

Conclusion

Bihar's groundwater resources are vital for its agricultural and economic development. While the state has significant groundwater reserves, challenges like over-extraction, pollution, and waterlogging necessitate sustainable management practices. Integrating traditional knowledge with modern water conservation techniques can ensure long-term groundwater sustainability in Bihar.