Lucknow, April 22 : Lucknow leads in overexploitation of groundwater in Uttar Pradesh with an average of 3.5 million litres of groundwater extracted per one square km which is alarming, to put it rather mildly. Scientists feel that over-exploitation of groundwater may turn the earth water deficient in the coming years. According to a survey conducted by a former hydrologist of the UP groundwater department, R S Sinha, "A total of 1,391 million of litre per day (mld) of groundwater is extracted, of which 356 mld is extracted by tubewells as per the data of UP Jal Sansthan, while the rest of the extraction of about 1,035 mld is for use in commercial buildings, hospitals, flats and others which are not mapped." Sinha underlined the need for developing techniques for groundwater recharge and water conservation. He said that making the existing rooftop rainwater harvesting systems more efficient is also a must. "The biggest solution is to reduce groundwater extraction and shift tubewells outside the city," he added. He said that "Excessive groundwater extraction in the city will eventually lead to salinity of water and excess of harmful arsenic and fluorides in water." /IANS