Project Location and Accessibility

Gamri-I hydropower project is a pure run-off the river scheme planned across Gamri which is a tributary of Gongri. The dam complex for Gamri I HPP is located approximately 700 m downstream from the Sakteng village. The Intake is located at the left bank of Gamri about 120 m below the road point near the Sakteng village view point. It is accessible with about 10 minutes’ walk from the nearest road point. The intake site for Bamukparongchhu is located below the Borangthi, a pasture land located behind the ridge (ridge between Gamri and Bamukparongchhu) to the south of the Sakteng village which is approximately 1.5 hour walk from the village.

The powerhouse structure is common for both Gamri I and Bamukparongchhu and it is located approximately 70 km from Trashigang town on the way to Sakteng Dungkhag. It is about 13 km to reach dam site from the powerhouse area. The powerhouse complex is located about 200 m below the road point near the Gamri-Bamukparongchhu confluence. The nearest village to the powerhouse complex is Thrakthri village under Sakteng Gewog which is about 2 km away from the powerhouse complex.

Field Investigations

Topography survey and mapping was carried out at 1:5000 scale at 5 m contour interval for the whole project area and along the main project components topography survey was carried out at a higher resolution of 1:1000 scale at 1 m contour interval. Geological mapping and geophysics surveys were carried out for ascertaining the geological conditions of the project area. Several stages of field visits were carried out to assess the topographical, geological and environmental & social impact assessment of the project layout.

Project Layout & Features

The project layout has been proposed on the left bank of Gamri and on the right bank of Bamukparong. It envisages a design discharge of 7.47 cumecs for Gamri I and 4.89 cumes for Bamukparong with respective net heads of 605.46 m and 324.00 m respectively. The corresponding installed capacities are 40 MW and 14 MW, which will generate annually of161.94 GWh & 66.40 GWh respectively.

A concrete gravity dam of 28 m high above the river bed level at Gamri I and Weir of 0.6 m at Bamukparongchhu with respective lengths at top of 44.83 m and 15 m will be constructed across the rivers. HRT of 2,470 m length of 4.5 m diameter for Gamri I at a gradient of 1 in 105 with 2 construction Adits will be constructed. The HRT will then be linked to surface HRP through a 25 m link HRP. On the Bamukparongchhu side, HRP of 2,494 m length will be laid along the road alignment at a gradient of 1 in 109. The surface powerhouse complex is proposed on the right bank of Gamri river just downstream of the Gamri and Bamukparongchhu confluence.  The powerhouse of dimension 69 m (L) x 20 m (W) x 26 m (H) shall be founded on 200 m long and 40 m wide flat area which is approximately 7 m above from the river bed level. Two units of (2x20 MW) and (2x7 MW) for Gamri I HPP and Bamukparongchhu respectively have been planned to accommodate in the powerhouse and the turbine water from the powerhouse is discharged into the river through a tail race channel. About 13.16 km of new roads are required to be constructed to access the various project components.