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?
Approach · directive: “what”
What it asks · Explain why and how seawater moves into India’s coastal aquifers, and suggest engineering, management and regulatory remedies.
It asks 2 things — answer each
- Explain the causes of seawater intrusion into India's coastal aquifers
- Suggest remedial measures — engineering, demand management, nature-based and regulatory — to combat the hazard
Open with · Seawater intrusion is the landward movement of saline water into freshwater aquifers when groundwater's seaward flow weakens; at Minjur near Chennai, heavy pumping since the 1970s reversed the hydraulic gradient and let the sea in (CGWB).
Cover
- Over-pumping for irrigation, industry and cities lowers the water table and reverses the hydraulic gradient (Saurashtra coast, Minjur near Chennai, Vasai–Virar).
- Reduced recharge: paved urban surfaces, erratic monsoon, and dams that cut river flows to deltas.
- Sea-level rise, storm surges and cyclones flood low-lying coasts; tides push saline water up creeks and estuaries.
- Land use: aquaculture ponds, salt pans, sand mining, dredging and loss of mangroves and dunes.
- Impacts: saline drinking water, soil salinity and falling yields, health stress and out-migration from coastal villages.
- Engineering remedies: tidal regulators and bandharas, check dams, recharge wells, subsurface barriers, managed aquifer recharge.
- Management: regulate extraction (CGWA), aquifer mapping, micro-irrigation, mangrove and dune restoration, a coastal monitoring-well network.
Close with · Managing coastal aquifers as a recharged commons — balancing extraction with recharge and restoring natural buffers — secures SDG 6, availability and sustainable management of water and sanitation for all.
Add value (verified)
- CGWB studies of the Mangrol–Chorwad coast of Saurashtra found salinity ingress in groundwater and linked it to local geology, coastal depressions and tidal flooding.PIB, Ministry of Jal Shakti — Salinity in Coastal Areas (21 March 2022) ↗“The presence of salinity in ground water along coastal Gujarat may be due to various reasons viz. prevailing hydro-geological settings, presence of physiographic depression in the coastal areas, inundation of sea water in low lying areas due to tidal fluctuation”
- CGWB (quoted by the NGT): heavy pumping at Minjur since the 1970s reversed the hydraulic gradient and caused saline intrusion; the Buckingham Canal and salt pans added to it.National Green Tribunal order citing CGWB's District Ground Water Brochure, Tiruvallur (2007) ↗“The heavy pumping of ground water for drinking water supply to Chennai city since 1970s from the well field at Minjur has been primarily responsible for the reversal of hydraulic gradient and consequent saline water intrusion in the eastern part of Minjur block. Recharge of saline water from the Buckingham canal and the presence of a few salt pans along the coast have also contributed”
- CAG performance audit (Gujarat, 2010): of 53 tidal regulators recommended by the High Level Committees for salinity ingress prevention in Saurashtra, only 11 were completed by March 2010; 64 of 127 bandharas.CAG, Audit Report (Civil) Gujarat 2009-10, Chapter 1 — Salinity Ingress Prevention ↗“Works suggested by No. of works No. of works Percentage No. HLCs and accepted by to be taken up completed of completed Government (1978-1992) (March 2010) work 1 Tidal Regulators 53 11 21 2 Bandharas 127 64 50”
- The Chennai Metropolitan Area Groundwater (Regulation) Act, 1987 works through permits to sink wells and registration of existing wells in the scheduled area.Chennai Metropolitan Water Supply and Sewerage Board — text of the Chennai Metropolitan Area Groundwater (Regulation) Act, 1987 ↗“THE CHENNAI METROPOLITAN AREA GROUNDWATER (REGULATION) ACT, 1987. Section Page 1. Short title, extent and commencement”
- SDG 6 in the UN's official wording.United Nations, Sustainable Development Goals — Goal 6 ↗“Ensure availability and sustainable management of water and sanitation for all”
Question: UPSC's CS (Main) 2025, GS Paper III — paper ↗. Approach: Minimalist IAS, checked 3 Oct 2026 (how we verify) — UPSC publishes no model answers. ·
Model answer· 224words · Minimalist IAS
Seawater intrusion is the landward movement of saline water into freshwater aquifers when groundwater's seaward flow weakens. At Minjur near Chennai, heavy pumping since the 1970s reversed the hydraulic gradient and let the sea in (CGWB).
Causes of seawater intrusion
- Over-pumping: irrigation, industry and city wells lower the water table and reverse the gradient.
- Reduced recharge: paved surfaces, erratic monsoons and dams cutting river flows to deltas.
- Sea and tides: sea-level rise, surges and cyclones flood low coasts; tidal canals and salt pans push salt inland.
- Land use and geology: aquaculture ponds, sand mining and lost mangroves; porous formations and coastal depressions worsen it in Saurashtra (CGWB).
| Cause | Mechanism | Remedy |
|---|---|---|
| Over-pumping | Gradient reverses | Regulate, recharge |
| Tidal creeks | Salt pushes inland | Regulators, bandharas |
Remedial measures to combat the hazard
- Engineering: tidal regulators, bandharas, check dams, recharge wells and spreading channels, as Gujarat's High Level Committees prescribed for Saurashtra; the CAG (2010) found only 11 of 53 tidal regulators built.
- Regulation: well permits and registration under the Chennai Metropolitan Area Groundwater (Regulation) Act, 1987; CGWA controls elsewhere.
- Demand management: micro-irrigation, salt-tolerant crops, metered bulk use.
- Nature-based and monitoring: mangrove, dune and wetland restoration; aquifer mapping and monitoring wells.
Managing coastal aquifers as a recharged commons, balancing extraction with recharge and restoring natural buffers, secures SDG 6, 'availability and sustainable management of water and sanitation for all'.
Prepared by Minimalist IAS to the answer standard of Shivam Singh (mentor, 7 years) · facts checked against official sources (how we verify) · updated 3 Oct 2026. UPSC publishes no model answers: compare your structure and coverage with this, then write your own.
