LUCKNOW, Feb. 20 -- The Gomti flows clear on the outskirts of Lucknow but as it moves deeper into the city, the river begins to change. The transformation is drastic by the time it reaches the city centre (Gomti Barrage).

Only about 30 kilometres of the river's 940-km journey across Uttar Pradesh - from Gomat Taal in Pilibhit to its merger at Kaithi in Ghazipur district - falls within Lucknow.

Yet, this relatively short stretch witnesses one of the sharpest declines in water quality.

The transformation raises the question: Among the four major urban settlements on the river banks (Sitapur, Lucknow, Sultanpur and Jaunpur) is the state capital segment among the biggest contributors to the Gomti's pollution? A ground investigation by Hind...