Just weeks before Ganesh Chaturthi, one of India's biggest religious festivals, sculptor Dilip Mhatre stands amid the ruins of his workshop in Raigad district, Maharashtra. Six months of work—around 500 clay idols of the elephant-headed god, worth 800,000 rupees ($8,300)—have been destroyed by floods. "The flood washed everything away," he says. "We have no idols, no moulds and no raw material."Mhatre's loss reflects a wider crisis. Raigad is the heart of India's Ganesh idol industry, with some...