Why does the Yamuna froth in Delhi?

Not just synthetic compounds, invasive aquatic plants as well as turbulence in the water also cause the phenomenon

A man lies within sight of a veritable sea of froth at the Okhla Barrage on the Yamuna in Delhi.Photo: Vikas Choudhary/CSE

Published on:

31 Jul 2026, 11:47 am

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The Yamuna is notorious for its iceberg-like clusters of white foam that drift across the water’s surface, especially in Delhi’s Okhla Barrage.

But what causes this phenomenon that stays on even during the monsoon?

According to the Delhi government, synthetic compounds, water hyacinth, plankton blooms, nitrogen and even proteins cause the froth.Photo: Vikas Choudhary/CSE

According to a study by the Delhi government, foam formation in the Yamuna is not solely due to synthetic ‘surfactants’ but may also be influenced by biogenic inputs, especially from invasive aquatic species like Eichhornia crassipes (water hyacinth).

Eutrophication-induced plankton blooms, longchain fatty acids, nitrogen gases, and even proteins enhance foam stability.

Lastly, the turbulence of the water at the barrage also plays a role. Clearly, this is a formidable environmental challenge faced by Delhi and one that has not been solved yet. Photo: Vikas Choudhary/CSE

According to the study, turbulence caused by the Okhla Barrage also plays a physical role in promoting foam generation by injecting gas bubbles into the surfactant-laden water column.

“Despite policy-level interventions under the Yamuna Action Plan and Namami Gange Programme, gaps remain in enforcement and integrated watershed management,” the report concludes.

The froth is one of Delhi’s most visible environmental challenges and is yet to be vanquished.

Delhi