More than half of Delhi’s groundwater samples tested between 2017 and 2022 have been found unfit for drinking, pointing to growing concerns around water quality and public health in the national capital. A report by the Comptroller and Auditor General (CAG) of India shows that 8,933 of the 16,234 samples analysed by eight zonal laboratories of the Delhi Jal Board (DJB) did not meet potable standards.
The report, titled “Functioning of Delhi Jal Board”, stated, “Quality testing of groundwater was carried out on 16,234 samples by the eight zonal laboratories of the DJB during the period 2017-18 to 2021-22. Out of the total samples tested, 8,933 samples (55 per cent) were found unfit for potable purposes.” The proportion of failed samples remained high throughout the audit period, varying between 49% and 63%. “Supplying groundwater from areas where samples were found unfit poses serious health risks to the public,” it added.
Untreated water supply raises concerns
The audit also highlighted cases where groundwater was supplied without any treatment, raising serious safety concerns. “During test check of records and information furnished by the DJB projects division and laboratories, it was found that 80 MGD to 90 MGD raw water from borewells/ranney wells was supplied to UGRs/consumers directly without treatment by DJB during 2017-18 to 2021-22, thus compromising water quality, which could be hazardous to the health of the people,” the report noted.
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Delhi continues to depend heavily on groundwater to meet its daily demand, with nearly 135 MGD of its total 1,000 MGD supply coming from sources such as tubewells.
Testing gaps and missing parameters
The CAG report points to significant gaps in how water quality is being assessed. While 43 parameters are required to be tested during treatment, only 12 were actually being checked by DJB. In some instances, water drawn from borewells was examined against just four out of 46 prescribed parameters. Critical checks, including “toxic substances”, “radioactive substances”, “biological tests”, and “virological tests” were not carried out. Testing for heavy metals such as arsenic, copper, and lead was also missing.
“The presence of radioactive substances and heavy metals in drinking water can be fatal as these substances may cause damage to the liver, kidney, and intestine, and also cause anaemia and cancer in humans,” the report added.
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Infrastructure gaps and rising losses
The audit further flagged operational shortcomings, including shortages of staff and essential equipment at testing facilities. It also noted that banned polyelectrolytes continued to be used at the Haiderpur plant despite prior restrictions. At the same time, water transmission losses increased from 16% to 21% between 2017 and 2022, indicating inefficiencies in distribution.
Non-Revenue Water levels remained consistently high, ranging between 51% and 53% of the total supply. This translated into an estimated revenue loss of over ₹4,988 crore during the audit period.
