supply officials say that since 2010 partly due to concerns about arsenic contamination new and expanded treatment plants have helped reduce their groundwater supply from 45 million gallons a day to 25 million gallons a daythe government is trying to take care that a situation does not develop agrees sinha ray the problem is that private extraction has gone up balancing out the citys increased surface water supply says sikdar with all this real estate coming up where is the water coming from he asksthe corporation banned new borewells in 2010 but has not been able to fully implement it sources in the kmc say there could be as many as 800 borewells in apartment blocks sinha ray estimates that total groundwater withdrawal today may be 75100 million gallons a daythe corporation says it plans to add another 70 million gallons to its filtered freshwater supply including to the highrises off em bypass by the end of this month itself the capacity of the garden reach water treatment plant will go up by 50 million gallons and the dhapa plant by 20 million gallons by 2022corporation sources said that the construction of small or capsule water booster pumping stations has also been given a lot of importance these would ensure drinking water supply to neighbourhoods that are heavily dependent on groundwaterscientist sinha roy believes that while the subsidence threat is not immediate certain steps are required to ward off the potential threat recharging groundwater putting a stop to the practice of withdrawing groundwaterhe praised kmcs initiative of augmenting surface water at its treatment plants it is encouraging that the corporation recognized the threat 10 years ago and accordingly arranged for augmentation of surface water at its treatment plants this will go a long way in minimizing groundwater depletion he addselango agrees that groundwater recharge is an important remedial measure and because kolkatas aquifers are charged at a distance from the city in areas that are also developing sikdar believes mandatory rainwater harvesting is also needed the city receives an average of 160cm of rainfall annuallyrules currently mandate rainwater harvesting for rooftops 20000 square feet but few building have such a large footprint he says these huge towers are taking out water from the ground and returning nothing back says sikdar what we need is a mass rainwater harvesting movement with inputs from saikat raythis story was supported by the pulitzer center