An 82-year-old retired government employee, Kakut Tayeng has lived by the blue waters of Siang river in Arunachal Pradesh all his life. So when about two months ago, the water of the started turning black, muddy and turbid, Mr Tayeng was in for a shock. Known as the Yarlung Tsangpo River in China, the river enters India at Shuomatan Point, becoming the Siang. At Pasighat, the Siang spreads out to flow downstream into Assam and becomes the mighty Brahmaputra.