Newsletter No. 62; IRBMS into River Brahmaputra in the State of Assam. In Bhutan, it is known as the Puna Tsang Chhu. It is a major river which drains West Central Bhutan. It rises as Mo Chu River from the snowy wastes at the base of the main Himalayan Range of northern Bhutan. Thereafter it flows in a general direction towards south to enter the plains. The two largest tributaries of River Sankosh are Mochhu and Phochhu. These tributaries flow together at Punakha. The upper catchment of the Mo Chu River is glaciated. The high mountain tops are under a permanent cover of snow. The middle and lower courses flow along V-shaped valleys have been carved by running water. The main geomorphic features of this tract include river terraces, interlocking spurs, cliffs and ridges. It has cut deep gorges across the lower Himalaya and the outer foothills. A number of large snow-fed streams including Pho Chhu join the Mo Chu River at Punakha Dzong and Wangdu Phodrang1. The Punakha Dzong, which is situated immediately above the confluence of the two rivers, is one of the most beautiful dzongs in Bhutan. The upper reaches of the Pho Chhu are susceptible to ice blockages, and the dzong has been damaged on several occasions by glacial outburst floods. At Wangdue Phodrang,( altitude 1364 m), the river is joined by the west flowing Dang Chhu 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.
The entire catchment of the Puna Tsang Chhu is covered by forests. These range from alpine meadows in the upper tracts to sub-tropical forests at lower elevations. Sankosh crosses over to India and flows through region bordering the West Bengal district of Jalpaiguri and the districts of Dhubri and Kokrajhar in Assam.
Dibang River: It originates near Keija pass on the Indo-Chinese border in the Dibang valley dist. of Arunachal Pradesh. The drainage basin covers districts of Dibang Valley and Lr. Dibang Valley. The Mishmi Hills lie in the upper course of the Dibang which enters the plains of Nizamghat. The river often changes its course, resulting in flooding and destruction of cultivable land and forests along its banks. The Dibang with a total length of 195 km. enters the river Lohit, north of Dibru- Saikhowa sanctuary, near Sadiya in Assam. The proposed Dibang dam for 3000 MW on completion would be among the largest dams in India and among the World’ s tallest gravity dams. This has run into opposition from the Mishmi people and Assamese who live downstream of the Project.
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Integrated River Basin Management Society