The ruling was the latest in a series of decisions by the court that have stopped giant construction projects in the Ganges floodplain and mandated the construction of new waste treatment plants in cities along its banks.

"It's the great achievement of my life, if it succeeds," says public interest attorney Arun K. Gupta, who took part in the litigation.

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Three sacred rivers meet at Allahabad: The Ganges, born of clear Himalayan tributaries that first trickle and then rage down from India's border with Tibet; its sister, the Yamuna, which shadows the Ganges to the west before curving past Delhi and the Taj Mahal to join her; and the mythical Saraswati, ancient and invisible,