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?
Subtopic: Environmental Pollution · Groundwater & coastal aquifers
How to structure your answer
Introduction: Define seawater intrusion as saline water displacing fresh groundwater in coastal aquifers.
Body: Causes (over-extraction, reduced recharge, sea-level rise) and remedial measures (managed recharge, regulation, barriers, alternative supply).
Conclusion: Sustainable coastal groundwater management.
Written within the word limit
147 words · target 150 words · 9 min
Introduction: Seawater intrusion is the inland movement of dense, saline seawater into freshwater coastal aquifers, contaminating wells and soils with salt and disturbing the natural freshwater-saltwater balance.
Causes:
- Over-extraction of groundwater lowers the freshwater table below sea level, so denser seawater pushes inland — as near Minjur, Chennai.
- Reduced natural recharge from urban concreting, falling rainfall and reduced river flow to the coast.
- Sea-level rise and storm surges, plus canals and salt pans that channel saline water inland.
Remedial measures:
- Regulate and cap coastal pumping under the Central Ground Water Authority.
- Managed aquifer recharge — check dams, recharge wells and rooftop harvesting to lift the freshwater head.
- Engineered subsurface barriers or freshwater injection to repel the saline wedge.
- Alternative supply through desalination and treated-wastewater reuse to cut groundwater dependence.
Conclusion: Demand control paired with active recharge can restore the freshwater balance and safeguard coastal aquifers for the long term.
What an examiner expects to see
- Seawater intrusion = inland movement of dense saline water into freshwater coastal aquifers, salinising wells and soil
- Primary cause is over-extraction lowering the freshwater table below sea level (the Ghyben-Herzberg balance is disturbed)
- Reduced recharge from urbanisation/impervious cover and declining rainfall aggravates it
- Sea-level rise, storm surges, and canals/salt pans channel saline water inland
- Minjur well-field near Chennai is a documented Indian case of intrusion from over-pumping
- Remedies: regulate coastal pumping via the Central Ground Water Authority; managed aquifer recharge (check dams, recharge wells)
- Engineered subsurface barriers or freshwater injection to repel the saline wedge
- Reduce dependence through desalination and treated-wastewater reuse
Concrete cases, schemes and judgments
- Minjur well-field, north Chennai (Tamil Nadu) — intrusion after over-pumping for city supply
- Saurashtra and Kachchh coast, Gujarat — salinity ingress in over-exploited coastal blocks
- Central Ground Water Authority regulation of notified over-exploited coastal areas
- Atal Bhujal Yojana — community-led sustainable groundwater management
- Desalination plants supplying Chennai to ease groundwater pressure