Upper Tamakoshi Shutdown Alert: 456 MW Plant Halts for 10 Hours

The Upper Tamakoshi Hydropower Project in Bigu Rural Municipality of Dolakha has completely halted electricity generation for around 10 hours on Sunday to clean its reservoir, which has accumulated a large volume of sediment, including rocks, sand and silt brought by recent floods and heavy rainfall. The shutdown was initiated to prevent technical problems and potential damage to the plant’s equipment, as the accumulated debris could clog the trash racks and allow sand and sediment to reach the turbines. According to acting project manager Purnagopal Ranjit, two large reservoir gates were opened from Sunday morning to release the accumulated sediment through a process known as reservoir flushing, which involves draining the reservoir and using high-velocity water to carry sediment away. The project aims to complete the cleaning process during the day and resume electricity generation after around 6 p.m., with all six units expected to operate at full capacity. Although reservoir flushing is normally carried out twice a year, unusually heavy monsoon floods caused sediment to accumulate earlier than expected, forcing the project to undertake the operation ahead of schedule. The opening of the reservoir gates could cause sudden fluctuations in water flow downstream, potentially creating flood-like conditions along the Tamakoshi River. The project has therefore issued a public safety notice urging residents from Dolakha to Ramechhap and Sindhuli to stay away from the river, avoid fishing, bathing and washing clothes, and keep livestock away from the riverbanks. The 456 MW Upper Tamakoshi project, Nepal’s largest hydropower plant built with domestic investment, has repeatedly faced sediment-related challenges during the monsoon due to heavy rainfall, fragile terrain and sediment carried by tributaries feeding the Tamakoshi River. If sediment is not removed in time, it could cause serious damage to turbines and other machinery, potentially forcing the plant into a prolonged shutdown. Although the 10-hour generation halt is expected to temporarily reduce electricity available to the national grid, the Nepal Electricity Authority has said that supply will be balanced through alternative arrangements. Project technicians are continuously monitoring the flushing operation, with the reservoir expected to be refilled after cleaning and power generation restored in the evening.