If there’s one city that probably relies more on groundwater than any other, it’s Chennai. That isn’t surprising, considering how in June 2003, J Jayalalithaa, then Chief Minister of Tamil Nadu, signed an ordinance making it mandatory for all public and private buildings to have rain-water harvesting systems. The ordinance gave all of Tamil Nadu just two months to build workable RWH systems.

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Today, over 90% of Chennai’s completed buildings may have fully functioning RWH systems. Yet, the recent Niti Aayog report on India’s water situation, picks Chennai as one of the city’s expected to run out of groundwater by 2020.

Is Chennai’s Zero Day Here?

“While I respect Niti Aayog’s findings, I differ with the point where it says Chennai will see its Zero Day by 2020,” says Arun Krishnamurthy, Founder of the Environmentalist Foundation of India (EFI).

He adds, “When you compare Chennai to other metropolises in the country, the way Chennai, Pune, Bangalore, Hyderabad, Coimbatore or any city in this country, is exploiting groundwater is one and the same. But the rate at which Chennai is recharging is at a better level when compared to other cities.”

Arun’s contention is to do with the city’s traditionally high water-recharge potential — evident since 2005 when Chennai has had good or higher-than-normal rainfall. But there is a problem: too much dependency on ground water.

Sources from the Chennai Metropolitan Water Supply estimate that the city draws anywhere between 200 and 300 MLD of ground water. ‘MLD’ stands for Million Litres per Day — a unit of measurement used by municipalities to gauge water consumption.

With such a heavy dependency on ground water, salinity levels from an extensive coastline are bound to rise. Added to the ever-present risk of sewage contamination, Chennai’s ground water reserves may not last long.

Even large residential townships, typically spend up to 35 percent of a home-owner’s maintenance charges towards buying water when ground water either depletes during summer months — or gets too saline for usage.

Conservation Measure #1: De-silt Lakes

The over-dependency on ground water has prompted organisations like EFI and a number of citizens’ groups to look for alternatives — or in other words, clean up Chennai’s lakes, and revive their storage potential.

At present, 19 lakes around the city are being de-silted, in time for the Monsoons later this year. If all goes to plan, these lakes will serve as vast reservoirs for rainwater, without relying too much on groundwater recharge.

“For a city with three rivers and over 300 lakes, there is massive recharge potential here,” says Arun.

Conservation Measure #2: Harvest In-House

While Chennai’s residential buildings have Municipality-mandated RWH systems, some townships have gone the extra mile to conserve more than mandated.

For instance, rain water collected from the House of Hiranandani’s Chennai township at Egattur, is being used to recharge ground water, while rain water from the roof tower is stored in the recharge pit for domestic water supply.

“This reduces the water extraction from other sources,” says Surendra Hiranandani, Chairman and MD, House of Hiranandani, “The project spends only between 15 and 20 percent of maintenance charges towards the procurement of water, if we rely on external sources alone. It’s lower than the city average since we adopt these conservation techniques.”

Conservation Measure #3: Eco-Friendly Real Estate

Sources from the Chennai Metropolitan Water Supply say that the next five years could see the city supply 550 million litres per day of desalinated sea water from two desalination plants. This should bring down the 300 million litres per day currently drawn out as groundwater.

But until then, urban planners have already begun acknowledging the importance of conserving lakes — even compromising on economics.

“We have to ensure that water channels are not blocked. If there are water bodies, we have to ensure that they’re recharged, or they become part of the landscape,” says urban planner, Shripal Munshi, “Once they get integrated into the design, and even if you have to take a hit on the FSI, so be it.”

The facts are as clear as daylight — Chennai’s groundwater isn’t going to be around for long. But conserving lakes, desalinating seawater, and saving more at home, could keep Chennai’s Zero Day at bay.

First Published:Jul 25, 2018 8:05 AM IST