Has the COVID-19 lockdown cleaned up the Yamuna?

Despite the lockdown due to the novel coronavirus disease (COVID-19), water quality at major locations of the Yamuna river do not meet the primary water quality criteria at two out of the three locations from where samples were collected and at the two major drains that flow into the river. 

The Central Pollution Control Board (CPCB) did an analysis to assess whether the lockdown significantly improved Yamuna water.

However, while for the pre-lockdown phase, monthly average samples from March and April 2018 and 2019 and March 2020 were analysed, the assessment for the lockdown period was based on a single-day sample that was collected on April 6, 2020, from three locations — Palla, Nizamuddin and Okhla as well as the Najafgarh and Shahdara drains that carry wastewater into the river. 

Important parameters like BOD (Biochemical Oxygen Demand) and Dissolved Oxygen (DO) did see a decrease during the lockdown but were still well above permissible limits according to the primary water quality criteria for bathing standards, the analysis revealed. 

BOD levels, which indicate the amount of oxygen required by the river to maintain its flow, were more than the prescribed standard of 3 mg/l (milligrams per litre) at Nizamuddin Bridge (5.6 mg/l) and Okhla upstream (6.1 mg/l). At Palla, it was 2 mg/l.

The lower the BOD, the better the water quality. However, there has been a considerable decrease when compared with data from last month and also from the last two months. 

DO, which is an indicator of how much oxygen is present in the river for the survival of aquatic life, was also less than the desired limit. DO should be 5 mg/l or more.

The higher the DO, the better the health of the river. At Nizamuddin and Okhla, the levels were less than 5 mg/l and even at Palla, while it was 8.3 mg/l, it had come down from 17.1 mg/l recorded in March 2020, despite the lockdown. 

At the Najafgarh and Shahdara drains, the BOD value was as high as 55 mg/l and 89 mg/l respectively. According to the CPCPB's own admission, discharge of partially-treated and untreated domestic wastewater continues to be in the same proportion as in normal days and it is being discharged through these drains.  

Meanwhile, COD (Chemical Oxygen Demand), the value that indicates the presence of industrial effluents in a water body, has shown a significant reduction in all monitored areas. This signifies that industrial discharge into the river has come down as a result of industries being shut during the lockdown. 

However, shutting down of industrial activity will only result in reduction of 35.9 MLD of industrial effluent and domestic sewage contributes to 80-90 per cent of the pollution load. 

The decrease in discharge of industrial effluents and minimised human activity like throwing of 'pooja' materials, solid waste disposal, bathing, washing of clothes due to ongoing lockdown has had a positive impact overall.

But the improvement was also attributed to release of fresh water into the river from the Wazirabad barrage due to non-availability of adequate storage capacity at the barrage, more discharge of fresh water from Hathnikund Barrage and unexpected or unseasonal rainfall. About 4,145 cusec (hourly average) of fresh water is being released.