The average groundwater table in Chennai has marginally increased in the past one year. However, there has been a dip in some areas of the city, indicating excessive groundwater extraction.
According to data compiled by Chennai Metrowater, the average groundwater level is now at a depth of 4.22 metres below ground level, which has increased by 0.26 metre since February last year.
Groundwater level varied from a depth of 3 metres to 6 metres across various zones depending on the soil layer and quantum of water extraction.
However, zones like Anna Nagar and Alandur have witnessed a drop in their water table close to one metre over the past one year. Merged localities like Manali, Madhavaram and Ambathur too have experienced a slight decrease in their water table. Water table fell by nearly 0.20 metre in these added areas.
Thiru.Vi.Ka.Nagar has recorded a considerable rise by nearly 1.74 metre in its water level followed by Tondiarpet zone. Besides zones in core parts of the city like Teynampet, Royapuram and Adyar that have also registered a marginal rise, merged areas like Perungudi and Sholinganallur have a rich groundwater table at a depth of 3 metres.
The city’s water table, which rose to an average of 3.46 metres in January after northeast monsoon, stabilised at a depth of 4.22 metres last month, said sources.
Chennai Metrowater collated data on the groundwater table through its real-time online monitoring system and digital water level recorders in borewells sunk at 200 locations in the city.
Sources said the water table was stable in core areas compared to those in merged areas due to sufficient daily water supply by Metrowater and sandy layer that enables quicker rainwater percolation. The water agency supplied nearly 1,070.64 million litres of water a day (mld) and of this, nearly 1,023,50 mld of drinking water is being provided to domestic consumers through pipelines and tankers.
The dip in water table, particularly in merged areas, indicated excessive groundwater extraction as some of them are yet to be covered with drinking water network and due to impervious soil layer or hard rock region, sources said.
Experts noted that there was a dire need for restricting groundwater extraction to protect resources. A groundwater resources assessment carried out by the Water Resources Department last year has categorised 26 firkas in the city as over-exploited with extraction exceeding 100%. Of the total 30 firkas in the city, Madhavaram, Alandur and Pallikaranai fall in semi-critical category with 70%-90% of groundwater extracted and Sholinganallur has been identified as safe zone.
