NEW DELHI: Even as the capital grapples with the problem of its fast depleting groundwater, there’s another cause for al
arm regarding the city’s underground resource — contamination by lethal toxins such as arsenic, nitrates and fluorides in parts of Delhi.
A recent Lok Sabha secretariat report reveals that east and northeast districts of Delhi suffer from arsenic contamination of groundwater while other districts have recorded nitrate and fluoride pollution.
The report also quantifies how much the city is overdrawing its groundwater. The overexploitation was to the extent of 27% — that is, for every 100 litres that gets replenished, Delhiites draw out 127 litres. It’s based on analysis of groundwater use between 2011 and 2013, the latest year for which data is available.
The arsenic contamination is not widespread, but it may point to unacceptable ground pollution in the city.
“Arsenic contamination has been found in some parts of the Yamuna flood plains but it’s still a rare occurrence. Though arsenic pollution is considered geogenic (naturally occurring) in other parts of India, some papers have attributed arsenic contamination to fly ash from thermal power plants in Delhi,” said Shashank Shekhar, assistant professor of geology at Delhi University.
Shekhar said nitrate pollution in Delhi may be linked to sewage seepage, runoff from landfills into groundwater aquifers in different parts of the city.
Fluoride contamination is restricted to the western part of Delhi where there is high groundwater salinity. Some studies have linked fluoride contamination to brick kiln activity while some say it is geogenic,” he said.
All three pollutants have severe health impacts. While arsenic is carcinogenic, high nitrate levels are known to cause methemoglobinemia, or “blue baby” disease. Shekhar said one of the reasons for high groundwater depletion is large scale concretisation.
“Most parts of the city have been concretised by way of urbanisation. There are very little recharge options. The focus should be on recharge, recycle and reuse in the city, otherwise it may be too late,” he said.
“The overexploite (groundwater) areas are mostly concentrated in three parts of the country — northwestern part of the country including Punjab, Haryana, Delhi and western Uttar Pradesh where although replenishable resources are abundant, there has been indiscriminate withdrawal of groundwater leading to over-exploitation,” says the report.
In its recent report called “Hydrogeological Framework and Groundwater Management Plan of NCT Delhi,” the Central Ground Water Board (CGWB) had recommended zone wise groundwater extraction criteria.
Out of the four zones it had made, CGWB recommended stopping extraction of groundwater in a 1km-zone on either side of the Najafgarh drain and from landfill and industrial sites because of the water there being highly polluted.
