India, Oct. 25 -- The afternoon sun glints off the Yamuna at ITO ghat, scattering light across bamboo barricades and freshly raised sand embankments. Loudspeakers hum devotional songs as workers rush to set up tents and women in bright saris check the arrangements. Young men wade into the shallows to tie bamboo poles as dredging machines work on the riverbed.

Preparations are underway in full steam for Chhath Puja. From Saturday, the riverbanks will be taken over by thousands of devotees marking a festival celebrates the Sun God and nature itself. But this year's celebrations carry a different weight.

After a gap of four years, the Delhi government has reopened 17 ghats along the Yamuna for immersions and prayers, alongside 1,300 smalle...