Most of Chennai’s groundwater units over-exploited, says Central Ground Water Authority report

According to a report from the Central Ground Water Authority (CGWA) of India, Chennai’s groundwater crisis remains acute, with over 80% of its assessed units falling into the ‘over-exploited’ category.

Of the 16 groundwater assessment units in the city, 13 are classified as over-exploited, meaning that extraction far exceeds recharge. while only two are considered safe. Despite previous efforts to augment surface water sources, the city still relies heavily on groundwater, particularly in peripheral areas and commercial zones.

The situation in Chengalpattu a rapidly urbanising district carved out of the former Kancheepuram region also shares the same fate. Of the eight groundwater assessment units, five are categorised as over-exploited, and the rest fall under the semi-critical or critical categories. With large-scale real estate developments, industrial corridors, and limited surface water sources, the district has seen a significant increase in groundwater use.

The CGWA submitted this report in response to a suo motu case taken up by the principal bench of the National Green Tribunal (NGT). The case was based on an article highlighting that groundwater levels in India are expected to fall to ‘low’ levels by 2025.

Kancheepuram district presents a slightly better scenario. Out of the five assessment units, all are classified as safe. Meanwhile, Nagapattinam stands out not for over-extraction, but for salinity issues. All four groundwater assessment units in the district have been classified as saline, indicating that the available groundwater is not suitable for drinking or irrigation without treatment.

In Tamil Nadu, 313 groundwater assessment units have been evaluated. Of these, 106 units, approximately 33.87%, have been classified as over-exploited, where groundwater extraction has significantly exceeded the recharge capacity.

As part of enforcement efforts, 492 illegally operating groundwater extraction units have been sealed following directions from the Madras High Court, the CGWA report said. 

However, the current regulatory framework notably lacks provisions for pricing, penalties, or the collection of environmental compensation. As a result, there has been no use of such funds for constructing groundwater recharge structures, check dams, water purification systems, or other interventions in contamination- or salinity-affected areas at either the State or district level.