Bangalore: For many residents of the new layouts, it is their only source of water. In other neighbourhoods and in most apartment complexes, the water from Cauvery has to be supplemented with water from borewells.

Groundwater levels have not only steadily gone down — 200 to 300 metres in many places — but may be getting heavily contaminated. The time when "well water" was considered superior to that piped into homes is long past. The Department of Mines and Geology, which takes samples across the city and regularly tests them and residents association who periodically get water samples tested, have found the concentration of nitrates on the increase.

A concentration of 50 mg per litre can cause more than upset stomach, it can seriously damage health and more so in the case of children. In adults, chronic acidity can be a warning sign that they need to check the quality of the water they drink.

Cess on borewell

Bangalore Water Supply and Sewerage Board which supplies the city with 850 MLD of water has started levying a cess for large-scale use of groundwater but has no regular monitoring mechanism in place to assess the quality of groundwater.

In most of the apartment complexes, water purifiers in individual flats are the norm. In some of the ongoing residential developments, the promoters have planned for a central water purifying plant in addition to recycling plants for water to be used for no drinking purposes.

The BWSSB has cautioned people to conserve water in the weeks ahead as consumption will be higher during hot weather. The Department of Mines and Geology, which recently tested 1,000 samples of groundwater from the city and suburbs and some from the just developed semi-rural areas has reported that the water may not be fit for human consumption.

"Nitrate levels have gone up to 150 mg/litre which makes it unsafe to drink. At the depths of 500 ft and more from where water is pumped up, salinity is much possible," the scientists say.

Boiling the water does not really help because the nitrate content increases under heat. Water purifiers help to some extent. Infants and children who regularly drink water with high nitrate content suffer frequently from respiratory disorders, leading to dangerous consequences.

Many paediatricians now routinely ask parents of children with chronic breathing problems to get their drinking water checked. Bacteria in the stomach convert nitrates into nitrites and in heavy concentration it can be fatal.

According to geologists, one reason why groundwater is getting more contaminated is because the underground aquifers are getting polluted from leaking drains. In the outer suburbs, ammonia and nitrate-based fertilisers used in nearby farms may be polluting the water too. There are no effective laws to prevent this, unlike the laws governing effluents discharged from industries, which are now enforced more strictly.

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