Revision summary
A coastal aquifer holds a freshwater lens in balance with seawater. Pumping, sea-level rise, storms and lost recharge let the salt water move inland. Gujarat, Tamil Nadu and other coasts already report saline wells. Remedies start with less pumping and more recharge, then barriers and, where needed, desalination. Mangroves and open recharge land are part of the same defence.
Model answer
Copper italics in this answer — like this — are the key facts. Each one is unpacked in the Facts & figures rail.
Introduction
Seawater intrusion is the movement of saline seawater into freshwater coastal aquifers, making groundwater brackish or saline. In India, excessive groundwater extraction, reduced recharge and climate-induced sea-level changes disturb the natural freshwater–seawater balance, threatening drinking water, agriculture and coastal ecosystems.
Body
Causes of Seawater Intrusion
- Over-extraction of groundwater: Excessive pumping for agriculture, industries and cities lowers the freshwater table and reduces hydraulic pressure towards the sea, allowing saline water to move inland.
- Reduced groundwater recharge: Urbanisation, paved surfaces and degradation of traditional water bodies reduce infiltration and weaken the freshwater head that keeps seawater offshore.
- Sea-level rise and extreme events: Climate change increases sea levels, while storm surges and cyclones can push saline water into low-lying coastal areas and aquifers.
- Coastal sand mining: Excessive extraction alters coastal and riverine hydrology, disturbing natural barriers and facilitating salinity ingress.
- Degradation of mangroves and wetlands: Loss of these natural buffers due to coastal development, pollution and aquaculture reduces protection against tidal and saline-water intrusion.
- Unsustainable coastal land use: Shrimp aquaculture and poorly planned coastal development can increase local salinisation and disturb coastal groundwater systems.
Remedial Measures
- Regulate groundwater extraction: Restrict groundwater abstraction and drilling in vulnerable coastal zones, while promoting water-efficient crops and demand management.
- Enhance aquifer recharge: Promote rainwater harvesting, restoration of tanks and recharge structures, and Managed Aquifer Recharge to rebuild freshwater pressure.
- Artificial recharge and freshwater barriers: Use treated wastewater through recharge dams and injection wells, as demonstrated by Gujarat's Salinity Ingress Prevention approach.
- Control sand mining: Strictly regulate coastal and riverbed sand mining through CRZ compliance, EIA enforcement and satellite/GIS-based monitoring.
- Restore natural coastal buffers: Protect and regenerate mangroves, wetlands and shelterbelts to reduce tidal impacts, erosion and saline ingress.
- Desalination: Deploy Reverse Osmosis (RO) for drinking water where aquifers are already severely salinised, while treating it as a supplementary rather than primary solution.
- Integrated monitoring: Regularly map groundwater levels and salinity to identify vulnerable zones and guide location-specific extraction and recharge policies.
Flow diagram
Conclusion
Seawater intrusion is fundamentally a groundwater-balance problem requiring demand management alongside supply augmentation. A combination of regulated extraction, aquifer recharge, CRZ enforcement and nature-based coastal protection, supported by measures such as Gujarat's salinity-ingress approach, can strengthen India's coastal water security and climate resilience.
Quick related
Students also ask
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Examine the factors responsible for depleting groundwater in India. What are the steps taken by the government to mitigate such depletion of groundwater?
Next question on this syllabus topic (2025 · Q13). View answer →
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Can a concrete sea wall stop intrusion?
It may stop a storm wave. Underground salt still moves if the well field is over-pumped.
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Is bottled water a remedy?
It is a private escape. It is not an aquifer policy.
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