Q8. 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?
Possible Introductions
Definitional framing:
Seawater intrusion refers to the process where saline seawater encroaches into freshwater aquifers, making groundwater unsuitable for drinking or irrigation. It is one of the most pressing hydro-geological hazards in India’s coastal regions.
Contextual framing (India):
With over 7,500 km of coastline and dependence of millions on groundwater for drinking and farming, seawater intrusion poses severe risks in states like Gujarat, Tamil Nadu, Kerala, and Andhra Pradesh.
Current affairs framing:
The Central Ground Water Board (CGWB) has flagged seawater intrusion as a major concern in several districts, and NITI Aayog’s Composite Water Management Index (2018) highlighted coastal aquifer salinization as a key sustainability challenge.
Directive Analysis
“What are the causes” → requires explaining both natural and human-induced drivers.
“What are the remedial measures” → requires suggesting technical, ecological, and policy solutions to address seawater intrusion.
Body of the Answer
1. Causes of Seawater Intrusion
-
- Over-extraction of Groundwater: Excess pumping of freshwater lowers the water table below sea level, drawing in saline water. This is common in coastal Tamil Nadu and Gujarat.
- Urbanisation and Industrialisation: High water demand from cities, ports, and industries reduces aquifer pressure and worsens intrusion.
- Climate Change and Sea-level Rise: Global warming-driven sea-level rise increases hydraulic pressure of seawater on coastal aquifers. Low-lying areas like Sundarbans and Kerala backwaters are highly vulnerable.
- Reduced Natural Recharge: Loss of wetlands, mangroves, and surface water bodies reduces aquifer recharge, creating a vacuum filled by seawater.
- Geological Factors: Porous coastal sediments and fractured rocks naturally allow faster saline ingress in certain regions.
X-Factor: The Gujarat coast (Saurashtra, Kachchh) and Minjur aquifer near Chennai are classic Indian examples of seawater intrusion.
2. Remedial Measures to Combat Seawater Intrusion
-
- Managed Aquifer Recharge & Artificial Recharge: Structures like percolation ponds, rooftop rainwater harvesting, and injection wells help raise groundwater tables and build hydraulic resistance to seawater.
- Subsurface and Physical Barriers: Installation of subsurface dams, cutoff walls, or impermeable liners can block seawater intrusion at strategic coastal locations.
- Sustainable Pumping and Conjunctive Use: Regulating groundwater withdrawal, promoting surface water use, and shifting to treated water sources (like desalination in Chennai) reduce intrusion pressure.
- Protecting Geomorphic Recharge Zones: Identifying and preserving natural features like paleochannels or sand dunes that retain freshwater can provide resilient recharge buffers.
- Technological Tools & Monitoring: Use of salinity sensors, satellite remote sensing, and modelling tools enables continuous monitoring and proactive management.
- Policy and Regulation: Effective coastal zone regulations, groundwater usage limits, and integrated water resource management are critical to maintaining aquifer balance.
Possible Conclusions
Future-oriented:
Sustainable aquifer management combining recharge, regulation, and restoration is essential to securing freshwater for coastal communities amid climate pressures.
Policy-oriented:
National programs under Jal Shakti Ministry, with state-specific intrusion action plans and funding incentives, can offer vital long-term resilience to coastal freshwater systems.
Philosophical:
Preserving freshwater from the inexorable advance of seawater is not merely a technical challenge—it’s about safeguarding livelihoods and heritage for future coastal generations.
