The Bhutanese Leading the way.
The 1020 MW Tala project which had seen overtopping has no major damage on the dam as it is intact with its integrity not impacted. There is also no scouring of the dam in the visible areas and so it is likely that there will not be scouring in areas that cannot be accessed like the plunge pool area.
The plan is to get the gates to be operational one by one but they do not intend to open them as the river flows are receding and they want to continue to generate. In terms of the damaged power packs connected to the five gates the assessment is that most of them can be repaired and for some spares will have to be procured.
The Logboom that prevents the entry of logs into the Head Race Tunnel intake was totally washed away and so it has been replaced.
While the turbines are a bit worn down the Druk Green Power Corporation (DGPC) said this is an occurrence every summer.
Dagachu
3D survey targets have been installed along the Head Race Conduit (HRC) at the Dagachu Hydropower Project to monitor the slope through regular survey measurements and visual inspections.
The immediate focus is on the construction of riprap at the slope toe to prevent further displacement according to sources. Detailed geotechnical and stability studies are planned to determine long-term remedial measures. To stabilize the area, the river has been diverted away from the slope, and riprap protection works are underway. The power plant remains under shutdown pending stabilization of the slope and completion of mitigation works.
The flood caused by incessant rainfall on 4th and 5th October, resulted in an extraordinary discharge of over 1,300 cubic metres per second. This flow far exceeded the project’s design flood capacity of approximately 850 cubic metres per second, which corresponds to a 1-in-10,000-year return period event.
This unprecedented event caused toe erosion of the slope below the HRC alignment, leading to continuous slope displacement.
As the slope has been completely eroded, long-term stabilization solutions are currently being discussed with experts. At present, temporary measures such as river diversion and riprap placement are being implemented to minimize further movement. Repair of the HRC will begin only after the slope has been stabilized.
Dagachhu Hydropower Project (125 MW) in Dagana had resumed operation at full capacity at 6:10 PM on 6th October, following the heavy rains, but undertook an emergency shutdown at 10:27 AM on 9th October to assess the HRC. Experts from Druk Green Consultancy, including hydropower and geology specialists, are conducting assessments and recommending protective measures at the site.
Officials said there is no damage to the water conductor system or the power plant itself, and that the shutdown is solely due to the erosion of the HRC slope. Operating the machines without proper assessment could impose additional loads on the channel, which needs to be filled with water carefully to prevent disturbances. The project is expected to make a decision within the next two to three days on whether it is safe to fill the HRC with water.
Suchhu
Repair and restoration works at the Suchhu Hydropower Project are expected to take approximately a month, after which power generation is expected to resume. The damage will impact the power generation targets for the year, according to the Ministry of Energy and Natural Resources (MoENR).
Access to the Suchhu power plant was blocked after multiple landslides occurred due to incessant rainfall on 4th to 5th October this year. Road access to the powerhouse was restored only on 16th October. A temporary bypass arrangement had been made at the location of the Sheychhu Bailey Bridge, located about 2 km before the powerhouse, which was also washed away by the floods. However, the intake site remains inaccessible.
A 5.8-meter section of the Glass Reinforced Pipe (GRP) Head Race Pipe (HRP) was damaged by the flood in the early morning hours of 5th October, and portions of the steel penstock above the powerhouse were exposed due to erosion of the earth fill materials. No further erosion has been observed since the last assessment.
A dedicated team from the DGPC O&M Service Centre was deployed to the site on 11th October. In addition, design teams from DGPC and DHyE visited the site on 12th October to assess the situation and plan restoration activities, particularly for the damaged GRP section. Restoration will be undertaken by M/s Vajra Builders Pvt. Ltd., the original civil works contractor for the Suchhu Project. Adequate GRP pipes are already available at the site, and the necessary repair materials and skilled workforce will be mobilized from other power projects.
Repair materials, machinery, and skilled manpower are being arranged by the contractor. They are expected to arrive at the site on 19th October to commence restoration works.
There are no major safety concerns, as the repair of the GRP pipes will be carried out on a stable and flat surface area.
The assessment of repair costs, including the restoration of access roads and affected project components, is currently underway. The final cost estimate will be determined upon completion of detailed evaluations.
