Seawater intrusion in the coastal aquifers is a major concern in India. What are the causes of seawater…

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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 ?

Ghissu Editorial · Accepted Answer

Seawater intrusion is driven mainly by over-pumping of coastal groundwater, worsened by falling recharge, aquaculture, sand mining, sea level rise and storm surges. Under the Ghyben-Herzberg relation, each metre of water-table drawdown lets the saline interface rise about 40 metres.

**Introduction**

Seawater intrusion is the movement of saline water into coastal aquifers when fresh groundwater outflow weakens. Since groundwater meets about 62% of India's irrigation needs (PIB, 2026), salinisation of coastal aquifers threatens food and water security.

**Causes of Seawater Intrusion in Coastal Aquifers**

SKETCH: flow | How Over-Pumping Pulls the Sea In
- Excess pumping
- Water table falls
- Interface rises 40x
- Wells turn saline

1. **Over-extraction**: Under the Ghyben-Herzberg relation, each metre of water-table drawdown lets the saline interface rise about 40 metres, as on the Saurashtra coast and in Chennai's Minjur aquifer.
2. **Falling recharge**: Paved cities, filled wetlands and dams that cut river flow to deltas such as the Krishna weaken the freshwater push that holds the sea back.
3. **Land use and climate**: Shrimp ponds in Andhra Pradesh, sand mining, rising seas and storm surges like Cyclone Amphan (2020) drive salt water inland.

**Remedial Measures to Combat the Hazard**

1. **Regulate pumping**: Central Ground Water Authority permits, NAQUIM aquifer maps and 43,228 monitoring stations (PIB, 2026) enable pumping caps near the shore.
2. **Recharge and barriers**: Recharge and injection wells, and tidal regulators and bandharas as in Gujarat's salinity ingress prevention works, hold the sea back.
3. **Cut demand**: Atal Bhujal Yojana's water budgeting, micro-irrigation and desalination at Minjur and Nemmeli ease pressure on aquifers.
4. **Coastal ecosystems**: Mangroves under MISHTI (2023) and Coastal Regulation Zone curbs on aquaculture and sand mining blunt surges.

**Conclusion**

Seawater intrusion is largely a human-made hazard magnified by climate change. Measurement, managed recharge and community regulation can keep coastal aquifers fresh and secure SDG 6.

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 ?

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