India, Oct. 22 -- A thick layer of toxic white froth has once again covered stretches of the Yamuna near Kalindi Kunj as falling temperatures and churning of water intensify foaming on the river's surface.

As the wind blows, cloud-like segments of froth roll over the surface, while devotees could be seen praying along the banks of the highly polluted river on Wednesday, once again highlighting the plight of the dying river. Over the next month, froth formation, as well as the politics around the phenomenon, will intensify as Delhi approaches Chhath festival.

What causes it?

The froth bubbles are caused by surfactant (soap-like) molecules. When water falls from a height at the nearby Okhla barrage, it leads to the churning of polluted w...