The river, however, has still not met the ‘water quality criteria’, reveals study
The quality of water in the Yamuna has improved along the Delhi stretch during the nationwide lockdown, compared to April last year, according to a report by the Delhi Pollution Control Committee (DPCC).
An increased flow of water in the river has also contributed to less pollution, the report said. But the report noted that the Yamuna has still not met the “water quality criteria”.
Also, pollution has reduced in five out of the six major drains, which flow into the Yamuna, that the DPCC measured.
A National Green Tribunal (NGT)-appointed monitoring committee had earlier this month asked the DPCC and the Central Pollution Control Board (CPCB) to measure the quality of water in the Yamuna.
Water from Haryana
Last week, a report by the Delhi Jal Board (DJB) had also shown the quality of water has improved during the lockdown and DJB officials had said that it was also due to increased discharge of water from Haryana.
On April 6, the DPCC had collected water samples from nine locations along the Yamuna and 20 locations of drains and compared the different parameters with values from April 2019.
Of the nine locations of the river, an increase in pollution was observed only in Khajuri Paltoon Pool, according to the report.
“In April 2019, the average flow was 1,000 cusecs compared to the average flow of 3,900 cusecs in April 2020. Therefore, the dilution is also contributing to the improvement of water quality,” the report noted.
Of the nine locations from where the DPCC took samples, five have shown 18%-33% reduction in biochemical oxygen demand (BOD) levels. The rest of the four locations have shown slight to considerable increase in BOD levels.
BOD is the amount of oxygen needed by microorganisms to decompose organic matter (waste or pollutants) under aerobic reaction (in the presence of oxygen).
A higher BOD level means that more oxygen is needed to decompose a large quantity of organic matter (waste or pollutants) present in the water. So, a higher value of BOD means that the water is more polluted.
Dissolved oxygen
According to the report, four of the nine locations where dissolved oxygen (DO) was nil in 2019 showed DO levels of 2.3-4.8 mg/l.
Dissolved oxygen is the amount of dissolved oxygen present in the water which is needed for aquatic life to survive. The quality of water increases with an increase in DO levels.
A DO level of 5 mg/l or above is the recommended level for bathing in a river and DO levels over 5 mg/l were found only in two locations closer to where the river enters Delhi, as per the report.
