Sankosh (also Gadadhar and Svarnakosha) is a river that rises in northern
Bhutan and empties into the
Brahmaputra in the state of
Assam in
India. In Bhutan, it is known as the Puna Tsang Chu below the confluences of several tributaries near the town of
Wangdue Phodrang. The two largest tributaries are the
Mo Chhu and Pho Chhu, which flow together at
Punakha. The Punakha
dzong, which is situated immediately above the confluence of the two rivers, is one of the most beautiful dzongs in Bhutan and the winter residence of the
Dratshang Lhentshog. The upper reaches of the Pho Chhu are susceptible to ice blockages, and the dzong has been damaged on several occasions by
glacial lake outburst floods. At Wangdue Phodrang, elevation , the river is joined by the west flowing
Tang Chuu and it enters a precipitous gorge. The highway running south from Wangdue Phodrang to Dagana follows the river for much of its course. Near the town of Takshay is the confluence with the west flowing Hara Chhu. The last major Bhutanese tributary is the Daga Chhu.