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
Introduction
A coastal well should taste of fresh groundwater that has slowly filled from rain. When it tastes of the sea, the freshwater lens has been invaded. That is seawater intrusion. In India it is already a fact on stretches of Gujarat, Tamil Nadu, Andhra, Odisha and the islands, not a textbook drawing.
Body
Causes
Fresh water in a coastal aquifer floats in a balance with denser seawater (the Ghyben-Herzberg idea). Heavy pumping for cities, industry and monsoon-failure irrigation lowers the freshwater head, and the salt water creeps inland. Sea-level rise and storm surge push the same interface. Reduced recharge — paved cities, dying tanks — weakens the freshwater side. Aquaculture ponds, poorly lined canals, and tsunami or cyclone floods can salt a shallow lens in a week. Sand mining and lost mangroves remove buffers.
Remedies
- The first remedy is less greed at the pump: licensing, electricity reform so that free power does not mean a dry, salty well, and shifting water-hungry crops. The second is recharge: check dams, spreading basins, and injection wells of treated water where geology allows. The third is engineering: subsurface barriers, and in extreme cases desalination for drinking (costly, energy-heavy). The fourth is land: protect recharge areas, restore mangroves, stop building on every dune. Monitoring — a salinity map that a panchayat can see — is the unglamorous core.
Without cutting extraction, a barrier is a delay. With only lectures, the next summer still tastes of the tide.
Flow diagram
flowchart TD P[Over-pumping] --> I[Intrusion] S[Sea-level rise storms] --> I R[Lost recharge] --> I REG[Regulate pump] --> F[Fresh lens] REC[Recharge barriers] --> F
Conclusion
Seawater intrusion is salt water replacing fresh coastal groundwater, mainly because of over-pumping, weaker recharge and a rising sea. Remedies are regulated pumping, recharge, careful barriers and honest land use, not a single wall.
Quick related
Students also ask
-
Terrorism is a global scourge. How has it manifested in India? Elaborate with contemporary examples. What are the counter measures adopted by the State? Explain.
Next question in the 2025 paper (Q9). View answer →
-
Can a concrete sea wall stop intrusion?
It may stop a storm wave. Underground salt still moves if the well field is over-pumped.
-
Is bottled water a remedy?
It is a private escape. It is not an aquifer policy.
PYQ trend
When UPSC asked this
Related PYQs from other years, newest first. Open a question to read it.
-
2025 · Q7 · GS III · 10 marks
What is Carbon Capture, Utilization and Storage (CCUS)? What is the potential role of CCUS in tackling climate change? -
2025 · Q13 · GS III · 15 marks
Examine the factors responsible for depleting groundwater in India. What are the steps taken by the government to mitigate such depletion of groundwater? -
2025 · Q17 · GS III · 15 marks
Mineral resources are fundamental to the country's economy and these are exploited by mining. Why is mining considered an environmental hazard? Explain the remedial measures required to reduce the environmental hazard due to mining. -
2025 · Q18 · GS III · 15 marks
Write a review on India's climate commitments under the Paris Agreement (2015) and mention how these have been further strengthened in COP26 (2021). In this direction, how has the first Nationally Determined Contribution intended by India been updated in 2022? -
2024 · Q7 · GS III · 10 marks
Industrial pollution of river water is a significant environmental issue in India. Discuss the various mitigation measures to deal with this problem and also the government's initiative in this regard. -
2024 · Q8 · GS III · 10 marks
What role do environmental NGOs and activists play in influencing Environmental Impact Assessment (EIA) outcomes for major projects in India? Cite four examples with all important details. -
2023 · Q8 · GS III · 10 marks
What is oil pollution? What are its impacts on the marine ecosystem? In what way is oil pollution particularly harmful for a country like India? -
2023 · Q15 · GS III · 15 marks
The adoption of electric vehicles is rapidly growing worldwide. How do electric vehicles contribute to reducing carbon emissions and what are the key benefits they offer compared to traditional combustion engine vehicles?
More from this paper
Q1 · UPSC Mains 2025 · GS III · 10 marks
Distinguish between the Human Development Index (HDI) and the Inequality-adjusted Human Development Index (IHDI) with special reference to India. Why is the IHDI considered a better indicator of inclusive growth?
Inclusive Growth
HDI combines life expectancy, education and GNI per capita into one average. India’s recent HDI is in the medium band, around 0.64, with a rank still in the 130s. IHDI reduces that score for inequality; India has often lost about thirty per cent of HDI to uneven shares. Inclusive growth needs the extra income and services to reach the bottom, which HDI alone can hide. IHDI is therefore the better national test, alongside the multidimensional poverty index.
Q2 · UPSC Mains 2025 · GS III · 10 marks
What are the challenges before the Indian economy when the world is moving away from free trade and multilateralism to protectionism and bilateralism? How can these challenges be met?
Indian Economy
The world is shifting from a single WTO bargain toward tariffs, subsidies, friend-shoring and carbon border taxes. India’s risks are weaker Western demand, costly Chinese intermediates, technology denial and rupee shocks. Goods exports in textiles, engineering and chemicals are exposed. Responses include wider FTAs, PLI with quality, destination diversification, forex buffers and a defence of WTO rules. A large domestic market is India’s shock absorber, not a reason to close the border entirely.
Q3 · UPSC Mains 2025 · GS III · 10 marks
Explain the factors influencing the decision of the farmers on the selection of high value crops in India.
Crops, Irrigation and Marketing
High-value crops are horticulture, spices, flowers and similar bets that can earn more than grain. Farmers weigh expected price and a real buyer against water, labour, credit and the chance of a price crash. MSP rice and wheat remain the safer default where they exist. Horticulture tonnage in India has already overtaken foodgrain, which shows the shift is underway. Policy must cut risk with storage, processing and insurance, not only cheer diversification.
Toppers' copies
Toppers' copies for this question will be uploaded soon.