NEW DELHI: Indian environmentalists are aghast that a huge cultural festival is to be held on the floodplain of Delhi’s main river from Friday, warning that the event, and the 3.5 million visitors expected, will devastate the area’s biodiversity.

The “World Culture Festival,” organized by one of India’s best-known gurus, Sri Sri Ravi Shankar, spreads across 1,000 acres (400 hectares) on the banks of the Yamuna. It features a 7-acre stage for 35,000 musicians and dancers, newly built dirt tracks and 650 portable toilets.

Green groups accuse organizers of ripping up vegetation and ruining the river’s fragile ecosystem by damaging its bed and disrupting water flows.

They want authorities to cancel the event and avert further harm.

“This land is not meant for any of those things. The biodiversity of the land has been completely destroyed,” said Anand Arya, one of several environmentalists who petitioned India’s top green court.

“Where will the sewage and the excrement go? All across the floodplains!” he said, adding that the waste left by visitors would endanger a nearby bird sanctuary.

The National Green Tribunal on Wednesday ruled that the event could go ahead but fined Ravi Shankar’s Art of Living Foundation 50 million rupees ($744,000).