Sewage in Coimbatore’s tanks threatens to pollute groundwater

March 22, 2013 12:00 am | Updated 05:08 am IST - COIMBATORE:

Siruthuli’s study findings to be released today

It is 10 years now since a citizens’ initiative to rejuvenate water bodies began in the city. Eight tanks in the city and another in the periphery were desilted. So were the canals that brought water to these tanks. The efforts proved to be good in 2004 when a good monsoon filled up the tanks.

But, 10 years down the line – after Siruthuli’s launch in 2003 – the tanks and canals present a sordid sight: some are bone dry while the others hold more of sewage.

All along, the desilting and removal of hyacinth has gone on without being complemented by the necessary infrastructure for sewage treatment. In fact, the tanks that hold water now pose greater threat than those that are dry, because the sewage only contaminates groundwater. Two major canals – Sanganur Canal and the Karuparayan Canal (near Vadavalli) – are filled with sewage. Heavy rain will flush the sewage into a couple of tanks. But, throughout the year small rivulets of sewage empty into Valankulam, Big Tank, Muthanankulam, Kurichi Tank, Krishnampathy Tank, Selvachinthamani Tank and Selvampathy Tank.

Unauthorised tenements with poor sanitation have come up around the tanks and the sewage from these areas finds its way into the water bodies.

Siruthuli’s Managing Trustee Vanita Mohan says the organisation has done a study of the ground water quality in all the 100 wards of the city and has come up with results that reveal heavy groundwater pollution. If this situation were to continue for long, the city’s groundwater will be rendered totally unusable. The study findings will be released on Friday as part of the World Water Day observance.

The present situation points out that unless the city has a comprehensive underground drainage system and sewage treatment facility, the purpose of rejuvenating tanks will be defeated by discharge of untreated sewage.

The Coimbatore Corporation has drawn up a Rs. 130 crore rejuvenation programme under the Jawaharlal Nehru National Urban Renewal Mission. But, its drainage and sewage treatment projects under the same mission will have to be in place first.

At present, the tanks that do have water are covered with hyacinth. And, the hyacinth feeds only on sewage.

Over the last 10 years, rainwater harvesting structures across the city too have helped in recharging the aquifers. At many places, the static level of groundwater has risen from 200 ft to 60 ft. But, the sewage in the tanks percolates and contaminates groundwater, defeating the very purpose of recharging the aquifers, Ms. Mohan points out.

Siruthuli’s progress seems to have been hampered by lack of sustainability. “We have the plan and expertise, but there is no go ahead from the Government department concerned. The Kurichi Tank is dry and this is the right time to desilt the tank and prepare it to hold more water during monsoon. Besides, the discharge of untreated sewage must also be prevented,” says Ms. Mohan.

Details of study of the tanks show that their water-holding capacity has shrunk because of silting and encroachments. Adding further agony is the sewage.

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