Groundwater down by half a metre as scanty rains fail to fill up aquifers in Chennai

Chennai:

The groundwater table in Chennai has seen a dip of 0.6 metres in the last one year owing to the lack of adequate rain coupled with heavy extraction, according to Chennai Metro Water.

Metro Water sources told Express the groundwater table came down by as much as 0.30 metres in the last one month alone due to lack of rains and heavy use.

The city has sandy, clay-filled and rocky terrains and the water table is different in each of the areas, the sources said.

The sandy area comprises Tiruvatiyur, Tondiarpet, Triplicane, Mylapore, Tiruvamiyur, Sowcarpet among others. Sources said that in these areas one can strike water at a maximum of 6.20 to 7.20 metres.

In areas like Triplicane, Mylapore and Besant Nagar one can get water from depth of 3 to 4.5 metres, the sources said.

In the clay-filled areas like Kolathur, Vadapalani, T Nagar and Chetpet the maximum level of groundwater is 8.05 metres while the minimum level is six to seven metres.

Similarly, in the rocky areas like Guindy, Saidapet, Alandur and Velachery, water is found at a depth of nine metres.

“The rainwater harvesting structures installed during the AIADMK regime in 2003 has helped increase the groundwater level in the city. As per a Metro Water monitoring report in 2011, compared to July 2003, the groundwater level and quality have increased after June 2011 in the city,” the official said, adding that the government is also planning an audit of rain water harvesting systems in the city.

Giving out figures, the official said the city currently has 7.20 million buildings and an estimated eight lakh rain water harvesting structures. Asked about the higher number of structures than the number of buildings, the official said many houses have two to four structures. “These have the potential to charge 60 per cent of the groundwater. In 2003, after the rain water harvesting was introduced, the water level increased by 20 to 30 feet,” he said. The main cause of depletion is heavy extraction of groundwater which can be resolved once the whole city gets piped water.

 “The city requires 1,100 million litres a day (mld) while Metro Water supplies around 800 million litres. As such 300 million litres of water is extracted from the ground,” he said.

Interestingly, even the urban development is also resulting in bigger challenges for the city. The urban growth has resulted in the government opening up East coast Road for development purposes, which was banned till 2007 to preserve aquifer potential in this area.

The government is of the opinion that in these areas aquifer recharge could be achieved by rainwater harvesting as such the proposal to lift the ban was taken, Metro Water sources said.