A CGWB study has warned that nearly 35% of Mumbai is highly vulnerable to seawater intrusion into freshwater aquifers (Img: Pinterest)
Mumbai: Nearly 35% of Mumbai’s geographical area is highly vulnerable to seawater entering freshwater aquifers, raising concerns about groundwater quality and long-term water security as parts of Maharashtra experience drought like conditions.
The findings come from the Central Ground Water Board’s (CGWB) 2025 Aquifer Management Plan, which assessed groundwater conditions across 603 square kilometres covering Mumbai city and its suburban districts.
The assessment identified significant salinity in groundwater at Fort, Shivaji Park in Dadar, Mulund East and Mahim. In the most affected locations, electrical conductivity a measure of dissolved salts in water exceeded 10,000 microsiemens per centimetre.
According to the report, shallow aquifers along Mumbai’s western and southern coastline are particularly susceptible to seawater intrusion. Deeper aquifers near creeks in the eastern parts of the city also face considerable risks. The problem was especially noticeable during the pre-monsoon period.
Although groundwater extraction remains at 46% in Mumbai city district and 26% in the suburban district, the report cautioned that these figures do not eliminate the possibility of localised saltwater contamination.
Seawater can enter freshwater reserves when excessive groundwater extraction reduces the pressure that normally prevents saline water from moving inland. Once contaminated, groundwater can become unsuitable for many uses.
Mumbai primarily relies on seven surface reservoirs replenished by monsoon rainfall between June and September. Groundwater now largely supplements the city’s water supply.
The CGWB has recommended limiting groundwater development in Fort to depths of up to 60 metres and imposing a complete ban on groundwater extraction in Shivaji Park, where highly saline water was detected at shallow depths.
The report also proposes filtered recharge pits, recharge shafts and percolation ponds in vulnerable parks and gardens. Regular monitoring of coastal observation wells and detailed investigations before approving new deep borewells have also been recommended.
Separately, the Brihanmumbai Municipal Corporation has commissioned the All India Institute of Local Self Government to collect well-water samples and assess the extent of groundwater salinisation across the city.
