The city’s natural groundwater reservoirs (aquifers), depleted through the years because of rampant use of tubewells, are being gradually filled with a cocktail of toxic pollutants. Polluted water is now seeping into these reservoirs to fill up the vacuum, experts of the Centre for Science and Environment have said.
“Over exploitation of water from the underground aquifers has resulted in a vacuum in some parts of the city, particularly in central and south-central Kolkata. Polluted water is seeping through the soil to fill up this empty space,” said Sunita Narain, director of the CSE.
Governor MK Narayan an launched an environment report brought out by CSE titled ‘Excreta Matters’ last Saturday. Minister of state for urban development Saugata Roy was also present.
The report claims that the city had a rich reserve of groundwater starting from just three metres deep. But a large number of tube-wells by private industries, business establishments, housing estates, high-rise apartments and households have been extracting water from the groundwater aquifers. “According to KMC, tube-wells and private tankers had been lifting 136 million litres a day from the groundwater aquifers till five years ago. This has increased over the years,” said Nitya Jacob, programme director (water) of CSE.
The result: Groundwater level in central and south-central parts of the city indicates a falling trend in both the pre and post monsoon period. There is fall of 7metres to 11metres in groundwater level from 1958 to 2003.
This extraction has developed a 6-8 metres conical depression in central and south central Kolkata. This trough has reversed the natural direction of groundwater flow towards the Bay of Bengal. Instead, polluted water flowing was seeping in, Jacob added.
“Water discharged from citybased tanneries and untreated waste water is seeping in. In addition, there is the problem of naturally occurring arsenic, which was earlier found in the fringes. Now this are found in Kolkata, too,” Jacob said.