How the Yamuna appeared relatively ‘cleaner’ during Chhath Puja in Delhi last year

Every year, during the preparations for and festivities of Chhath Puja in Delhi, there is a rise in discourse around the pollution that plagues the holy Yamuna river as it passes through Delhi. Visuals of people standing in the river while surrounded by toxic foam on river create a temporary uproar which also fuels political parties like the Bharatiya Janata Party (BJP) and Aam Aadmi Party (AAP) to point fingers at each other.

Yamuna’s passage across Delhi, especially the 22-kilometre stretch between Wazirabad and Okhla (which constitutes under 2% of the rivers total length of 1,400 kilometres) contributes to around 76% of the pollution load of the river, as per official data, majorly due to the several drains that merge into the river in this stretch. The discolouration of the river water, from being almost transparent at the northernmost sampling location (Palla) to severely discoloured along with foam at Okhla, is also evident as The Hindu reported earlier this month.

Just before the commencement of the Chhath Puja festivities on October 25, the Haryana government diverted nearly all the water from the Hathnikund Barrage towards Yamuna, thereby, diluting the holy river water’s pollutants, as reported by The Hindu in October 2025. This “unprecedented” step by the newly-formed BJP government, that came back to power in Delhi after 27 years, was met with backlash by AAP, did improve the water quality, as the data shows.

Every month, the water quality is sampled across eight locations by the Delhi Pollution Control Committee (DPCC) as shown in the map below. The water enters Delhi at Palla, where the quality of the water meets the standards set by the Central Pollution Pollution Control Board (CPCB) as the highly polluting Najafgarh drain flows into the Yamuna downstream of the Wazirabad bridge.

In the chart below, the readings taken during or the period immediately before and after Chhath festivities since 2019 are shown (readings of fecal coliform before November 2019 are not available). Readings taken on October 20, 2025 across different sampling stations are highlighted in red. Even in October, the levels of pollutants (fecal coliform) was still higher than bathing standards put forth by the CPCB.

The river has been the least polluted during Chhath Puja in 2025 when compared to similar periods in the past 7 years. In fact, from January to October last year, the data shows that, barring September, the river was least polluted in October (highlighted in red).

Measures like Biological Oxygen Demand (BOD) and Dissolved Oxygen (DO) showed a slight improvement when compared with most readings from previous years. However, even in October 2025, they didn’t meet the set standards for outdoor bathing.

The readings in September 2025, which were sampled by the DPCC on September 3, were less because the pollutants were diluted due to very heavy rainfall in the area in the period between late August and early September. Receiving excess discharge from the Hathnikund Barrage in Haryana, water levels of the holy river surged past the danger mark early September, just around the time of sampling, as shown in the chart below.

Temporary measures

However, just towards the end of Chhath Puja, the Haryana government scaled back the volume of water released from the Hathnikund Barrage by nearly 96%, The Hindu reported on October 29, 2025.

Thus, in the subsequent months, the Yamuna’s water quality in Delhi has degraded, with fecal coliform levels rising steadily to almost 40 times the maximum permissible limit as shown in the chart below.

Data from all sampling locations after Wazirabad show an increase in the level of fecal coliform following Chhath Puja in October 2025, as shown in the chart below.

The measures taken during Chhath Puja in October last year were temporary. AAP’s Delhi President Saurabh Bharadwaj did term the move as a “temporary illusion” to showcase a cleaner Yamuna during Chhath Puja,The Hindu reported on October 24, 2025.

Out of the 20-plus drains that merge into the Yamuna after Wazirabad, two drains cause over 80% of the pollution load: Najafgarh (70%) and Shahdara (14%), as per a report by the Centre for Science and Environment.

(With inputs from Nikhi M. Babu)