Monsoon flow improves Yamuna water quality in August

Water quality in the Yamuna improved in August compared with the previous month as increased monsoonal flow diluted pollution in the river, according to the Delhi Pollution Control Committee’s (DPCC) latest monthly assessment

Water quality in the Yamuna improved in August compared with the previous month as increased monsoonal flow diluted pollution in the river, according to the Delhi Pollution Control Committee’s (DPCC) latest monthly assessment.

Despite the improvement, levels at several locations remained above the Central Pollution Control Board (CPCB) standard (HT)

The report, dated September 9, showed a sharp decline in faecal coliform levels at several monitoring points. At Asgarpur, where the river exits Delhi, faecal coliform levels fell from 320,000 MPN/100ml in July to 3,600 MPN/100ml in August. At Okhla Barrage, the count declined from 110,000 MPN/100ml to 23,000 MPN/100ml during the same period.

Faecal coliform levels are an indicator of sewage contamination in the river.

Despite the improvement, levels at several locations remained above the Central Pollution Control Board (CPCB) standard of less than 2,500 MPN/100ml.

The river met the standard only in its upper stretch, with faecal coliform levels of 1,400 MPN/100ml at Palla, where the Yamuna enters Delhi, and 1,100 MPN/100ml at Wazirabad. In July, the count at Wazirabad — from where Delhi draws drinking water — was 3,500 MPN/100ml.

The improvement was also reflected in dissolved oxygen (DO) levels. In July, DO had fallen to zero along the stretch from ISBT to Asgarpur. In August, however, measurable oxygen levels were recorded across the stretch.

DO, which is essential for sustaining aquatic life, should ideally be above 5mg/L. In August, it was recorded at 6.8mg/L at Palla and 5.7mg/L at Wazirabad. The level stood at 3mg/L at ISBT, 5mg/L at ITO bridge, 4.6mg/L at Nizamuddin, 4mg/L at Okhla and 2.6mg/L at Asgarpur.

Biochemical oxygen demand (BOD), however, remained high across most of the river stretch. Palla was the only location to record an acceptable BOD level of 3mg/L, while all other monitoring points recorded higher levels.

BOD measures the amount of dissolved oxygen consumed by microorganisms while breaking down organic matter in water, with higher levels generally indicating a greater pollution load.

During the monsoon, increased environmental flow, or e-flow, in the Yamuna helps dilute pollutants and generally leads to an improvement in water quality.

HT had earlier reported that the Delhi stretch of the river was largely running dry in May and June, contributing to poor water-quality indicators in July.

The August figures also showed an improvement compared with the corresponding period last year. In August 2025, faecal coliform levels at Okhla Barrage stood at 54,000 MPN/100ml, compared with 23,000 MPN/100ml this August.

However, Asgarpur continued to record the highest levels of BOD, chemical oxygen demand (COD), phosphate and faecal coliform among the monitoring points, indicating the accumulation of sewage and other pollutants as the river flows through Delhi.

Between Wazirabad and Okhla, 22 drains discharge into the Yamuna, significantly adding to the river’s pollution load.