According to Environmental Science and Pollution Research, 7% of India's coastal area faces seawater intrusion, with groundwater levels dropping below mean sea level.

This phenomenon occurs when saltwater displaces freshwater in coastal aquifers due to various natural and human factors.

Seawater Intrusion

Seawater Intrusion

Causes of Seawater Intrusion

Natural Factors:

• Climate Change: Sea-level Rise due to Climate Change accelerates landward movement of the saltwater-freshwater interface.
• Geological Structure: Natural fractures and permeable rock formations facilitate saltwater movement.
• Tidal Action: Regular tidal movements create pressure gradients pushing seawater inland.
• Topographic Features: Low-lying coastal plains with minimal elevation gradients.
• Storm Surges: Cyclonic events temporarily raising sea levels and accelerating intrusion.

Anthropogenic Factors:

• Excessive Groundwater Extraction: In Chennai and Nagapattinam, over-pumping for agriculture and urban needs has led to salinity in borewells.
• Coastal Development: Infrastructure projects disrupting natural recharge patterns.
• Destruction of Natural Barriers: Mangrove clearing reducing natural protection (40% loss in Sundarbans).
• Agricultural Practices: Intensive irrigation depleting freshwater aquifers.
• Industrial Activities: Heavy water consumption by coastal industries.

Remedial Measures to Combat Seawater Intrusion

Policy and Planning Measures:

• National Aquifer Mapping (NAQUIM 2.0): Detailed mapping of 256 priority coastal districts.
• Atal Bhujal Yojana: Empowers local communities to manage groundwater resources by preparing Gram Panchayat-wise Water Security Plans (WSPs).
• Coastal Regulation Zone (CRZ) Guidelines: Restricting development within 500m of high tide line.
• Water User Associations: Involving local communities in water budgeting, groundwater monitoring, and rainwater harvesting.

Technical Solutions:

• Artificial Recharge Structures: Construction of percolation tanks, recharge wells, and check dams.
• Injection Wells: Creating freshwater barriers using treated wastewater.
• Strategic Well Relocation: Moving pumping stations inland (successful in Andhra Pradesh).
• Desalination Plants: Chennai's 100 MLD plant reducing groundwater dependency.
• Managed Aquifer Recharge: Controlled injection of freshwater during monsoons. Example: Managed Aquifer Recharge (MAR) pilot projects in Gujarat and Andhra Pradesh.

Addressing seawater intrusion requires integrated coastal zone management combining technological solutions with policy reforms.

The success of Gujarat's water grid system demonstrates how strategic planning can effectively combat this growing environmental challenge.