India’s first Aquifier Atlas, released by the Central Ground Water Board (CG-WB) recently, has further reiterated what other studies have shown about Chennai city. Over exploitation of groundwater has rendered it vulnerable to sea intrusion in different pockets, putting to danger sensitive aquifers on which a major chunk of the population depend for water needs.
According to the atlas, Chennai is one of the districts classified as “Over Exploited”, with parts having salinity content higher than permissible limits. However, what is striking is the fact that the “Aquifer Vulnerable Map”, which is part of the document, shows that the north of Chennai as one of only four pockets in entire Tamil Nadu, which has seen significant sea-water intrusion, with the other two being pockets of Cuddalore, Ramanathapuram and Kanyakumari.
Sources said as early as in 2007, the Public Works Department (PWD) had initiated a study of the aquifer systems in Minjur, the area in Chennai worst affected by groundwater exploitation.
“The industry there had extracted so much that we estimated the intrusion could have been as much as 15 km into the aquifer during the study,” said a senior official. Such intrusion made the water unfit for potability in pockets.
What raised alarm about the Minjur experience was the fact that no aquifer functions in isolation. CGWB officials pointed out that if one aquifer gets contaminated by sea water, chances of the adjoining one facing the same threat would be high. “Such aquifers are always linked. This is why, once intrusion is noticed, careful management plan had to be in place. Once a aquifer is contaminated, it is very hard to reclaim it,” one official told Express.
However, recent observations have shifted their focus to South of Chennai in areas such as Adyar and Besant Nagar, where officials pointed out that signs of intrusion are already showing. “While the studies are still going on, there is no denying the fact that South Chennai is seeing high exploitation of ground water resources owing to over development and increasing fresh water demand,” said a PWD official.
Chennai has also been designated as a district where groundwater showed Nitrate levels higher than the permissible limit of 45 mg/l.
Highly placed sources said there was no stringent monitoring of mechanised water withdrawal close to the coast, though regulations place restrictions on setting up of mechanical tube wells in the Coastal Regulation Zones (CRZs). “If you read the regulations, you would know that there are restrictions placed on how you withdraw water in the CRZ. Whether people get booked for violation is the big question,” observed one official.
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