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November 02

 

When water turns salty

- by Emmanuelle


Seawater intrusion in the aquifer threatens Auroville beach communities

 

The hand pump of Repos gives salty waterThe beach communities of Auroville are under threat. In mid-July, the dozen residents of the Repos community were greatly alarmed to find seawater had infiltrated their bore-well. The situation rapidly worsened. Soon, even the water from the hand pumps had turned salty. Other Auroville beach communities like Gokulam and Quiet and the beach villages Chinnamodeliarchavady, Perrya-modeliarchavady and Bommarpalayam too have witnessed seawater intrusion in some of their wells and hand pumps. It appeared that the entire coast from Pondicherry to Chennai is suffering from the same problem, a problem which has also affected parts of Kerala on the western coast.

Saline intrusion happens when the underground water level is lower than the sea level. This creates a vacuum and allows seawater to come in. Manfred, who has done a lot of research on the subject, explains, "When the water level of a well is below sea level, then the pressure of the sea water opens small channels, through which the sea water enters. Once the connection has been made, the channels will never close again. The situation is irreversible; the well can not be used anymore."

The problem is the extremely low level of the underground water table. This is only in small part due to the near failure of the summer monsoon this year. The root cause is prolonged over exploitation of ground water, mainly because of free electricity for farming. Farmers, however, are not the only ones guilty of overexploiting the ground water. Individuals too, though to a lesser extent, contribute to the lowering of water levels. Auroville residents are no exception; Auroville's average consumption per capita per day being extremely high as compared to the average in India.

The residents of Repos, in order to remedy the situation, have tried to solve the problem by deepening the bore well by some twenty-five feet. However, this failed, and the water in the well continues to be salty. "This leaves no other solution than seawater desalination," says Myriam, a Repos community member since many years. "There is already a desalination system in place in Repos, but that can only desalinate a hundred liters per day. The Auroville unit Aquadyn has proposed a 'Reverse Osmosis' device whereby sea water is pressurized through a micro-filter membrane in which the minerals are caught. The water coming out is then free of salinity. We would need a system that can filter five hundred liters per day, which would cost fifty thousand rupees (US $ 1,000) plus operating charges. These are high as desalination takes a lot of electricity. We have approached the Auroville community for financial support."

Fortunately, after some unexpected but long-awaited pre-monsoon rains, the water from one hand pump has turned sweet again, due to the run-off water from inland on its way to the ocean. Until today, this water is enough for the basic needs of the residents, drinking and washing, and, thanks to the rains, the coconut palm trees and garden plants are still alive. But nobody knows for how long the water will remain sweet, and if it will continue to rain.

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