Here’s more bad news. Delhi’s groundwater table is not just depleting, but also becoming a cocktail of toxins, including rising levels of nitrate and fluoride.
An analysis of Delhi’s groundwater has found that almost 30 per cent samples — mostly from South-West, West and North-West districts — contain high concentrations of fluoride beyond the prescribed maximum permissible limit.
The nitrate concentration in groundwater too shows a wide range, i.e., less than 1mg/l to 1,500 mg/l, with the concentration in groundwater being generally spread out over the entire State. The nitrate concentration is more significant in parts of West, South-West and some pockets of New Delhi districts. Nitrate pollution in groundwater is mostly anthropogenic and maybe a result of improper disposal of sewage and unhygienic conditions around the well.
According to the Central Ground Water Board’s year book 2011-12 for Delhi, the chemical quality of groundwater varies with depth and space.
“Fresh groundwater aquifers mainly exist up to a depth of 25 metre to 35 m in North-West, West and South-West districts, and in minor patches in North and Central districts. In South-West district, especially Najafgarh [Jheel area], fresh water occurs up to a depth of 30 m to 45 m,” noted the report.
A localised area situated just north of Kamala Nehru Ridge (part of Delhi Ridge falling in Central District), covering Dhirpur, Wazirabad and Jagatpur, is characterised by shallow depth of fresh water aquifers that is in the range of 22 m to 28 m, regardless of proximity to the Yamuna. The groundwater is fresh at all depths in areas around the ridge falling in Central, New Delhi, South and eastern part (ridge area) of South-West districts and also Chhattarpur basin.
“The findings are important because the Delhi Jal Board is unable to provide safe piped water network to several parts of Delhi. Those then dependent on private abstraction wells or tankers that supply untreated groundwater are the worst affected by contaminated water. Delhi has 162 hydrograph monitoring stations,” noted environmentalist Vinod Jain.