Chennai: The record rainfall that led to the devastating deluge in the city has helped increase groundwater table by two metres to 10.5 metres across the city. According to the Chennai Metropolitan Water Supply and Sewerage Board (CMWSSB), in areas like Puzhal, Parry’s Corner, Ambattur (Balaji Nagar), Ayanavaram, Villivakkam, Anna Nagar (West), Koyambedu, West Mambalam, Saidapet and St Thomas Mount, the water level has risen by five metres on an average. In other areas, the increase in water levels is in the range of two to five metres.
As per the latest data of the Chennai metro water, which monitors groundwater level and quality through 145 observation wells in the city, the ground water level in Ambattur (Balaji Nagar) rose from 10.60 metres before the onset of the northeast monsoon to 0.10 mbgl (metres below ground level) after the rain.
Parry’s Corner and Saidapet witnessed increase in the water table by 8.05 mbgl and 7.40 mbgl. “Unlike rural areas, there is no question of natural percolation in the city. If the groundwater level goes up in the city where all the areas are paved, it means the rainwater harvesting structures have played a major party,” said Sekhar Raghavan, director, Rain Centre.
In 2005, when the city witnessed heavy rain and flooding, the water level increased by six metres after rain water harvesting structures were made compulsory in the buildings in 2003, he recalled.
Despite heavy rain, water table at Ayanavaram, Tiruvottiyur and Tondiarpet still remain at 5.50 mbgl, 4.20 mbgl and 3.10 mbgl. Raghavan said a reason for low ground water table in these areas was due to presence of more number of street houses.
“Street houses which are fully built with main doors on the street have no space for rain harvesting structures. In those houses, the rain water collected in rooftops is mostly let out in the streets,” he said.
He said Kasi Viswanathar temple tank at Ayanavaram remains dry despite heavy rain. The water table in the area remains at 5.50 mbgl shows that inadequate recharge of ground water. “We want the city corporation to intervene and build rain harvesting structures on the roads and divert run off water in the streets to the temple tanks. This will help improve the ground water table,” he said.
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