Chennai’s deep aquifers are being sucked dry. In 2023, the city extracted 127.5% of its groundwater, against the national extraction average of 59.3%, say the latest central government statistics. Since 2009, the city has always drawn more groundwater from deep aquifers than the recharge. The rate of exploitation has, however, been falling.
In 2009, 400% of the potential recharge was extracted and 226% was extracted in 2011. This has gradually decreased to 133% in 2022 and 127.5% in 2023, say data with the Central Ground Water Board (CGWB).
The CGWB’s 2023 National Compilation on Dynamic Ground Water Resources of India said over-exploitation was more in core areas of Chennai than added areas. Over-exploitation was recorded in Perambur, Guindy, Ambattur, Velachery, Purasaiwakkam, Tiruvottiyur, Egmore, Mambalam, Mylapore, Aminjikarai, Ayanavaram, Maduravoyal and Tondiarpet.
“This is because the density is higher in core areas than added areas, hence the water demand is also high. There are around 26,000 people per kilometre in the core city,” said former Anna University urban engineering professor K P Subramanian.
Groundwater aquifers in Alandur were in a semi-critical state. Those in added areas such as Sholinganallur, Madhavaram and Pallikaranai were in better shape.
“Added areas are not completely covered with piped water supply, and their dependence on groundwater is high. However, their cumulative water demand is relatively less due to less density in population. Also, there are more unpaved places in added areas, enabling more recharge,” said hydrogeologist J Saravanan.
“If shallow aquifers are recharged via working rainwater harvesting wells and then used through open wells and slotted borewells, the groundwater extraction would come down. Many tap into the deep aquifers through borewells, exploiting the water, which took years to recharge,” said Sekhar Raghavan, director, Rain Centre.
The city extracts more groundwater than its other three neighbouring districts, which are part of the Chennai Metropolitan area. Chengalpet, Tiruvallur and Kanchipuram have not over-exploited groundwater. While Tiruvallur district had the highest safe groundwater resources at 91.4%, Chennai had the least at 22%.
“Less urbanisation and population could keep the water demand low in the other districts,” said Subramanian.
In Chennai, the dependence on groundwater will decrease when Metrowater improves the quality and quantity of piped water supply, said Saravanan.
Metrowater has increased water supply but has not met the Ministry of Housing and Urban Affairs’s standard of 135litres per head every day. It supplies a total of 1,040 million litres a day to 88 lakh people in the city.
“Metrowater has increased its supply from 650 MLD in 2018 and this has reduced groundwater dependence in the city,” said Metrowater’s hydrogeologist, P Subramanian.
In 2009, 400% of the potential recharge was extracted and 226% was extracted in 2011. This has gradually decreased to 133% in 2022 and 127.5% in 2023, say data with the Central Ground Water Board (CGWB).
The CGWB’s 2023 National Compilation on Dynamic Ground Water Resources of India said over-exploitation was more in core areas of Chennai than added areas. Over-exploitation was recorded in Perambur, Guindy, Ambattur, Velachery, Purasaiwakkam, Tiruvottiyur, Egmore, Mambalam, Mylapore, Aminjikarai, Ayanavaram, Maduravoyal and Tondiarpet.
“This is because the density is higher in core areas than added areas, hence the water demand is also high. There are around 26,000 people per kilometre in the core city,” said former Anna University urban engineering professor K P Subramanian.
Groundwater aquifers in Alandur were in a semi-critical state. Those in added areas such as Sholinganallur, Madhavaram and Pallikaranai were in better shape.
“Added areas are not completely covered with piped water supply, and their dependence on groundwater is high. However, their cumulative water demand is relatively less due to less density in population. Also, there are more unpaved places in added areas, enabling more recharge,” said hydrogeologist J Saravanan.
“If shallow aquifers are recharged via working rainwater harvesting wells and then used through open wells and slotted borewells, the groundwater extraction would come down. Many tap into the deep aquifers through borewells, exploiting the water, which took years to recharge,” said Sekhar Raghavan, director, Rain Centre.
The city extracts more groundwater than its other three neighbouring districts, which are part of the Chennai Metropolitan area. Chengalpet, Tiruvallur and Kanchipuram have not over-exploited groundwater. While Tiruvallur district had the highest safe groundwater resources at 91.4%, Chennai had the least at 22%.
“Less urbanisation and population could keep the water demand low in the other districts,” said Subramanian.
In Chennai, the dependence on groundwater will decrease when Metrowater improves the quality and quantity of piped water supply, said Saravanan.
Metrowater has increased water supply but has not met the Ministry of Housing and Urban Affairs’s standard of 135litres per head every day. It supplies a total of 1,040 million litres a day to 88 lakh people in the city.
“Metrowater has increased its supply from 650 MLD in 2018 and this has reduced groundwater dependence in the city,” said Metrowater’s hydrogeologist, P Subramanian.