Seawater intrusion in the coastal aquifers is a major concern in India. What are the causes of seawater intrusion and the remedial measures to combat this hazard? (150 words)

Seawater intrusion in the coastal aquifers is a major concern in India. What are the causes of seawater intrusion and the remedial measures to combat this hazard?

Introduction

Seawater intrusion is the landward movement of seawater into freshwater aquifers due to excessive groundwater extraction or natural processes. In India, with over 7,500 km of coastline, this phenomenon threatens drinking water security, agriculture, and ecosystems in states like Gujarat, Tamil Nadu, Andhra Pradesh, Odisha, and Kerala.

 

Causes of Seawater Intrusion

1. Over-extraction of Groundwater
• Intensive pumping for irrigation and industry lowers the water table, reversing the hydraulic gradient.
2. Urbanisation and Industrialisation
• Coastal cities like Chennai and Visakhapatnam face heavy groundwater demand, accelerating intrusion.
3. Reduced Recharge
• Paving of coastal areas, deforestation, and reduced monsoon recharge limit natural replenishment.
4. Sea Level Rise due to Climate Change
• Thermal expansion and melting ice caps increase seawater pressure on coastal aquifers.
5. Geomorphology and Soil Conditions
• Sandy coastal formations with high permeability allow faster seawater intrusion.
6. Saltwater Upconing
• Excessive pumping causes deeper saline water to move upward into freshwater zones.

 

Remedial Measures

1. Groundwater Regulation
• Enforcing limits on pumping, licensing of wells, and community-based management.
2. Artificial Recharge and Conservation
• Check dams, percolation tanks, recharge wells, and rainwater harvesting to maintain groundwater levels.
3. Subsurface Barriers
• Physical barriers (subsurface dams, cutoff walls) and hydraulic barriers (recharge trenches) to block seawater intrusion.
4. Use of Alternative Water Sources
• Desalination plants (e.g., Chennai), treated wastewater, and surface water substitution.
5. Crop Diversification and Demand Management
• Promoting less water-intensive crops in coastal agriculture.
6. Monitoring and Modelling
• Remote sensing, GIS-based aquifer mapping, and early warning systems for salinity ingress.

 

Conclusion

Seawater intrusion in India’s coastal aquifers is a hydro-environmental hazard aggravated by over-extraction and climate change. A combination of regulation, recharge enhancement, technological solutions, and sustainable water use is necessary to safeguard freshwater reserves and ensure long-term water security for coastal populations.

 Note: This model Answer for Reference Purpose only