Salinity: Coastal Ingress, Irrigation and Effluent
Chapter Thirty-Six
Syllabus topic 1, "Water"
Pages 148 to 151 of 885
In one line
Fresh water floats on sea water, and if you pump the fresh layer too hard the salt comes up to meet you, and it does not go back.
In the wording a student can write in an exam: salinity in a coastal aquifer is caused by saline ingress, the landward and upward movement of sea water into a fresh water aquifer when the fresh water head is lowered by over-extraction; inland it is caused by water-logging and evaporation in irrigated tracts and by the discharge of saline effluent; it is very largely irreversible, and Indian law addresses it through the notification and regulation of extraction, through the protection of drinking water sources, through artificial recharge, and through the polluter pays principle where it is caused by effluent.
The physical explanation, in four sentences
Fresh water is lighter than sea water, so in a coastal aquifer it floats as a lens on the salt water beneath.
The lens is held down by its own head. The Ghyben-Herzberg relation says that for every metre the fresh water table stands above sea level, roughly forty metres of fresh water stand below it. So one metre of drawdown at the surface lifts the salt water interface by about forty metres.
Pumping lowers the head, and the interface rises. A well that was fresh becomes brackish and then salt, and this is called upconing where it happens beneath a single well.
And it does not reverse. Once salt is in the pores of an aquifer it takes decades of natural flushing to remove, and in a hard rock aquifer with little storage it may never be removed. That irreversibility is the legal point: this is not pollution that can be cleaned up, it is destruction of the resource.
The three Indian salinity problems
Coastal ingress. The whole of the Indian coastline is at risk where extraction is heavy, and the case law is the Lakshadweep decision. Attakoya Thangal v. Union of India, a decision of the Kerala High Court of 1990. Facts. The administration proposed to augment the water supply of the coral islands by digging wells and pumping; the petitioners said the fresh water lens was only 0.6 to 0.75 metres deep, that the potential for recharge was limited, and that pumping would lower the hydraulic head and let sea water penetrate. Held. No administrative agency may function so as to make inroads into the fundamental right under article 21; the right to life is much more than the right to animal existence; the right to sweet water and the right to free air are attributes of the right to life; a methodology must be evolved for the extraction of ground water and over-exploitation must be contained; the matter was referred to the Ministries with a direction to issue appropriate directions and, if necessary, to make statutory regulations and set up a monitoring agency. Why it matters here. It is the Indian authority that ties salinity to article 21, and it is the answer to MU's whole question of 2026.
Salinity: Coastal Ingress, Irrigation and Effluent
Inland salinisation from irrigation. Canal irrigation without drainage raises the water table; the water evaporates from near the surface and leaves its salts behind; the soil goes white and stops growing. The remedy is drainage and conjunctive use, not more water.
Salinity from effluent. A dyeing or tanning industry discharges a high total dissolved solids effluent, and the receiving water and the land irrigated from it become saline. Tirupur Dyeing Factory Owners Association v. Noyyal River Ayacutdars Protection Association, AIR 2010 SC 3645, is the case. Facts. Bleaching and dyeing units at Tirupur discharged effluent into the Noyyal, which was impounded at the Orathupalayam dam for irrigation. An inspection committee found high pH, very high total dissolved solids, excess chloride and a high percentage of sodium in the river, and the farmers could not cultivate their land. Held. The polluter pays principle and the precautionary principle have to be read with the doctrine of sustainable development; the units, having polluted unabated, cannot escape the responsibility to meet the expenses of reversing the ecology, by removing the sludge from the river and cleaning the dam, and the farmers whose losses a committee had assessed were to be compensated. The association was given three months to make the common effluent treatment plants functional, pay the balance for cleaning the dam and the river and pay the compensation, and the Pollution Control Board was directed to ensure that no pollution is caused. Why it matters here. It is the money remedy for a salinity that has already happened.
The legal responses, and what each can and cannot do
Notification and regulation of extraction. The Central Ground Water Authority notifies over-exploited assessment units; the Maharashtra Act notifies areas under section 4 and prohibits deep wells under section 8. This is the only response that can prevent ingress, because ingress is caused by the head, and the head is caused by the draft.
Protection of drinking water sources. Sections 20 to 23 of the Maharashtra Act, and in particular section 23, which protects a source against contamination. Saline water is contamination for this purpose.
Artificial recharge. Section 9 of the Maharashtra Act, rooftop harvesting, percolation tanks, check dams and injection wells, and on a coast a fresh water recharge barrier which raises the head deliberately to hold the interface down.
Salinity: Coastal Ingress, Irrigation and Effluent
Regulation of the aquifer as a unit. Section 41 of the Maharashtra Act, which allows the basic watershed or aquifer to be declared, is what makes an ingress response possible at all, because ingress is a property of the aquifer and not of any well.
And polluter pays where the cause is effluent, on the authority of Tirupur and of Indian Council for Enviro-Legal Action v. Union of India, AIR 1996 SC 1446, in which the Court held that a person carrying on a hazardous activity is absolutely liable and that the cost of remedying the damage is part of the cost of the activity.
Worked example
A coastal taluka has five hundred bore wells within three kilometres of the shore. Chloride in the wells nearest the sea has risen year on year for a decade.
Step one, what is happening? The fresh water head has fallen, the interface has risen, and the wells nearest the sea are drawing brackish water.
Step two, what will more wells do? Make it worse and faster. Deepening the wells makes it worse still, because a deeper well is closer to the interface.
Step three, what does the law offer? Notification under section 4 of the Maharashtra Act and prohibition of deep wells under section 8; protection of the drinking water sources under sections 20 to 23; artificial recharge under section 9; and declaration of the aquifer under section 41 so that the whole unit can be planned.
Step four, is there a right? Yes. Attakoya Thangal: the right to sweet water is an attribute of the right to life, and the State may not itself pump the lens away.
Step five, and what if a saltworks or a shrimp farm is drawing sea water inland? Then the Coastal Aquaculture Authority Act, 2005, as amended in 2023, and the Coastal Regulation Zone Notification apply, a shrimp farm registered under that Act being a permitted activity under the Notification, and the chapter on aquaculture takes it up.
Step six, the honest conclusion. Every legal instrument here is preventive. There is no remedy that restores a salinised aquifer, and an answer that says so is stronger than one that lists remedies as though there were.
Distinctions
| Coastal salinity | Inland salinity | Effluent salinity | |
|---|---|---|---|
| Cause | Over-draft lowering the fresh water head; sea water rises | Irrigation without drainage; evaporation concentrates salts | Discharge of high dissolved solids effluent |
| Where | The coastal belt and islands | Canal commands, especially in arid tracts | Below an industrial cluster |
| Legal response | Notification, prohibition of deep wells, recharge barriers | Drainage, conjunctive use, cropping change | Polluter pays, closure, restoration cost |
| Case | Attakoya Thangal | Tirupur Dyeing | |
| Reversible | Very largely not | Slowly, with drainage | The water, yes; the soil, slowly |
Salinity: Coastal Ingress, Irrigation and Effluent
What it does NOT mean
It does not mean salinity is only a coastal problem. Rajasthan, Haryana and Punjab have extensive inland salinity, and the cause there is irrigation, not the sea.
It does not mean a treatment plant answers it. An effluent treatment plant removes organic load and colour; total dissolved solids pass through unless there is a reverse osmosis stage with a plan for the reject, and the reject is itself brine.
And it does not mean deepening the well helps. In a coastal aquifer a deeper well is nearer the salt, and deepening accelerates the failure.
Quick revision
Saline ingress: the landward and upward movement of sea water when the fresh water head falls. Ghyben-Herzberg: roughly forty metres of fresh water below sea level for every metre above it, so one metre of drawdown lifts the interface about forty metres. Upconing is the local form beneath a well.
Three Indian problems: coastal ingress; inland salinisation from irrigation without drainage; and effluent salinity.
Attakoya Thangal, Kerala High Court, 1990: the right to sweet water is an attribute of the right to life under article 21; over-exploitation must be contained.
Tirupur Dyeing, AIR 2010 SC 3645: polluter pays and the precautionary principle, read with sustainable development; the units must meet the expenses of reversing the ecology, removing the sludge and cleaning the dam, and compensate the farmers.
Legal responses: notification and prohibition of deep wells; protection of drinking water sources; artificial recharge; declaration of the aquifer as a unit; and polluter pays where effluent is the cause. All preventive; none restorative.
Test yourself
1. Explain in two sentences why over-pumping a coastal aquifer makes it salty. Fresh water floats as a lens on denser sea water and is held down by its own head. Pumping lowers the head, so the salt water interface rises, and by the Ghyben-Herzberg relation one metre of drawdown lifts it about forty metres.
2. Why is salinity a worse legal problem than most pollution? Because it is very largely irreversible: salt in the pores of an aquifer takes decades of flushing to remove and in a low-storage aquifer may never be removed, so no restoration remedy exists and only prevention works.
3. What did the Kerala High Court hold in Attakoya Thangal? That the right to sweet water and the right to free air are attributes of the right to life under article 21, that an administrative agency may not function so as to make inroads into that right, and that a methodology must be evolved for extraction so that over-exploitation is contained.
4. Which principle answers salinity caused by industrial effluent, and what does it require? Polluter pays, applied in Tirupur Dyeing, where it was read with the precautionary principle and the doctrine of sustainable development: the polluters cannot escape the expenses of reversing the ecology, which meant removing the sludge from the river, cleaning the dam and compensating the farmers whose losses had been assessed.
The rest of this subject
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