Divya Mehra and Shiwani

The Coronavirus pandemic which has affected almost every part of the world is considered to be the biggest economic and health crisis of the present time. To contain the spread of the Covid-19 disease, in the initial phases of the pandemic, many countries went into lockdown, resulting in the temporary suspension of all economic and non-essential activities. India also went into a nationwide lockdown on 24 March 2020. For more than two months people were confined to their homes, and industries, markets, offices, business centres, etc. were temporarily shut down. According to several articles and news reports, the lockdown provided nature with a brief break from the effects of anthropogenic activities, giving it a chance to rejuvenate. The most immediate effects were observed in the water quality of the river Yamuna. As per the reports submitted to the Yamuna Monitoring Committee (YMC) by the Central Pollution Control Board (CPCB) and the Delhi Pollution Control Committee (DPCC), the water quality of the river at several places along the Delhi stretch had improved considerably, and the major reasons were attributed to the freshwater released into the river upstream of the Delhi stretch, absence of industrial effluents, reduction in extraction of water for industrial use, and less human activities along the river.

The Yamuna, the fifth-longest river in India and the largest tributary of the river Ganges is known to be one of the most polluted rivers in the world. Originating in the Yamunotri glacier in the Uttarkashi district of Uttrakhand, the river traverses through some high population density areas. The river flows through states like Uttarakhand, Uttar Pradesh, Haryana, and passes through world-famous historical cities like Delhi, Agra, and Mathura, before merging with the Ganges at Triveni Sangam in Prayagraj, Uttar Pradesh. The total length of the river is 1,370 kilometres and is divided into 5 segments: Himalayan Segment, Upper Segment, Delhi Segment, Eutriphicated Segment, and Diluted Segment. Table 1 and Figure 1 show the area covered under these segments.

Himalayan SegmentFrom origin to Tajewala Barrage(172 kms)
Upper SegmentTajewala Barrage to Wazirabad Barrage(224 kms)
Delhi SegmentWazirabad Barrage to Okhla Barrage(22 kms)
Eutriphicated SegmentOkhla Barrage to Chambal Confluence(490 kms)
Diluted SegmentChambal Confluence to Ganga Confluence(468 km)
Table 1: Different Segments of Yamuna river (Source: Yamuna Basin Organization)
Figure 1: Segments of river Yamuna. (Misra. 2010)

The Delhi Segment

As per the Yamuna Action Plan, the Delhi segment of the river is only a 22 km long stretch from Wazirabad to Okhla barrage covering only 2 per cent of the total area of the river. At the Wazirabad barrage, the water is diverted for domestic supply to the residents of Delhi. From here very little or no water is allowed to flow downstream during lean seasons (Misra, 2010). The only water that flows downstream is received from the 22 sewage drains that flow directly into the river. This segment is the shortest but carries 70 per cent of the total pollution load of the river. Some of the major reasons as discussed in the Yamuna Action Plan for this pollution load are due to sewage drains such as Najafgarh, Shahadra, and supplementary drains that are the main contributors of sewage in the river. Delhi’s 45 per cent area is un-sewered, and the untreated waste is often released into open storm-water ditches/drains, which eventually merge into the river.  Around 28 industrial clusters and more than 51,000 estimated industries in non-conforming/residential areas are the major contributors of industrial effluents. According to the CPCB, the water quality of the Yamuna falls under the category “E” which makes it fit only for recreation and industrial cooling, completely negating the possibility for underwater life and human consumption such as drinking and cleaning.

Yamuna during Lockdown

Within a few days of the nationwide lockdown, induced by Covid-19, social media and news reports flooded with pictures of visible improvements in the water quality of river Yamuna. Several residents reported that the watercolour of the river is appearing to be blue and there is a reduction in the foul smell of the river. To understand this change in detail, the Yamuna Water Committee formulated by the National Green Tribunal asked the CPCB and DPCC to undertake testing of water quality in the river as well as the main drains joining the river. Both CPCB and DPCC carried out testing at different locations and assessed the water quality using parameters like Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), and Chemical Oxygen Demand (COD).

Water Quality Assessment for Delhi Segment

To determine the change in water quality before, during, and after the lockdown, using the data provided by DPCC, we have analysed the change in BOD, COD, pH, and DO levels in the river at 9 different locations for March, April, and June 2020. These locations are represented in Figure 2. For the analysis, we have considered the data for March as ‘before lockdown’; data for April as ‘during lockdown’; and the data for June as ‘after lockdown’, taking into consideration the date for the first unlock (01 June 2020), which focussed on reopening of economic activities in a phased manner.

Figure 2: Water monitoring locations for Delhi Segment. (Water quality trend of river Yamuna in Delhi. 2015-2019)

Biological Oxygen Demand

Graph 1
Graph 2

The above two graphs (1 & 2) represent BOD values and the percentage change during, before, and after the lockdown period. For places like Palla, Surghat, and Palton Pool, the BOD values have increased by 12, 26.6, and 10 per cent, respectively, in the period from March to April. For the rest of the places, the BOD values have decreased in this period. The highest decrease, which is 70 per cent, can be seen downstream of Okhla Barrage after meeting the Shahadra drain. A 61.9 per cent decrease is seen at the Agra Canal (Okhla) followed up by a 28 per cent decrease at the Agra Canal (Jaitpur) and a 33.3 per cent decrease at the Nizamuddin Bridge. Although the data represents a decrease in BOD levels at several locations, the values remain above the permissible limit of 3mg/l. In total, the BOD value decreased in 6 locations and increased in 3 locations from March to April.

Interestingly, in the time from April to June, the percentage change in BOD values has increased significantly. Out of the total 9 locations from where the samples were collected, 8 of them showed an increase in the BOD value while one of them had no change.  A 100 per cent increase can be seen at the Agra Canal (Okhla) location followed by 76.4 per cent at the Agra Canal (Jaitpur).

Chemical Oxygen Demand

Graph 3
Graph 4

The above two graphs (3 & 4) represent COD values and their percentage change, respectively, before and during the lockdown period. For places like Palla, Surghat, Palton Pool and Kudesia Ghat, the COD values have increased in the period between March to April. The highest increase of 60 per cent is seen at Surghat followed by Palla with 50 per cent, Palton Pool with 38.1 per cent, and Kudesia Ghat with a 25 per cent increase in the values.  For the rest of the places, the COD values have decreased in the lockdown period. The highest decrease which is 68.4 per cent can be seen downstream of Okhla Barrage after meeting the Shahadra drain. A 68.2 per cent decrease is seen at the Agra Canal (Okhla) followed by a 57.9 per cent decrease at the ITO Bridge and a 44.7 per cent decrease at the Nizamuddin Bridge. Interestingly, these same places which experienced a sharp decrease during March to April had a steep increase in the COD concentration during the April – June period, with ITO Bridge and Agra Canal (Okhla) marking the highest increase of 137.5 per cent and 133.33 per cent respectively. In total, 4 places had an increase and 5 places had a decrease in the COD value during March to April; and 7 places had an increase and 2 places had a decrease in the COD value from April to June.


Graph 5

All the values of pH recorded (Graph 5) at different segments of Yamuna are within the primary water quality criteria for bathing water limit (‘C’ Class) which ranges from 6.5-8.5, although a slight increase and decrease can be seen within the permissible limit.

Dissolved Oxygen

Graph 6

Data for the DO variable was only available for three locations in river Yamuna. Those places are Palla, Surghart, and Nizamuddin Bridge. The above graph (6) represents the comparison in DO levels from March to June.

The required amount of DO for a healthy river should be above 5 mg/l. From the above graph, it can be seen that the Palla region meets this criterion, although a decrease is seen in the value during the April month followed by an increase in the value in June.  Surghat did not meet this criterion before the lockdown but subsequently met the required limit during the lockdown, and later saw an increase in the value in June. At Nizamuddin Bridge, the DO remained below the required value for a healthy river throughout, even after seeing a slight increase during the lockdown period, that is April. 


The data represent a considerable change in the water quality at several locations in the infamous segment of the river. According to the CPCB report, Najafgarh and Shahadra drain which share two-thirds of the hydraulic load of all the drains have also shown a 30-40 per cent improvement in BOD levels. This improvement is majorly attributed to the availability of freshwater being released into the river from the Wazirabad barrage. As notified by the Delhi Jal Board in early April 2020, about 4,145 cusec (hourly average) of freshwater is being released due to the non-availability of adequate storage capacity at Wazirabad Barrage, and more discharge of freshwater from the Hathnikund Barrage in the Himalayan Segment. Unseasonal and unexpected rains during late March and early April have also contributed to the availability of freshwater resulting in dilution of the river. This enabled washing out of bottom sediments as well as the colloidal form of pollutants in the river resulting in good penetration of solar radiation in the water body.

The other important reasons for the improvement of water quality can be ascribed to the temporary closure of industries during the nationwide lockdown because of which the extraction of freshwater from the river was reduced and industrial effluents and toxic wastes were not discharged into the river. As people were confined to their homes, activities like disposing of puja waste, solid waste disposal, bathing, washing of clothes, etc. also minimised. However, discharge of partially treated and untreated domestic wastewater continued to be in the same proportion as in pre-lockdown days.

The Covid-19 induced lockdown allowed nature to demonstrate its ability to restore and rejuvenate itself. The two months of closing down of most anthropogenic activities did what the authorities had been struggling to do for the last 25 years.  This improvement in the water quality has provided a road map or a starting point to work towards cleaning the river by controlling the amount of toxic and organic waste that is being dumped into the river by creating sewage treatment plants, establishing interceptors, and reviving traditional water bodies along the river that would support in improving the health of the river.


Featured Image by Ichattopadhyaya

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