The national pride project, located in Bigu Rural Municipality, was forced to execute a total shutdown after incessant rains and upstream floods choked its reservoir with massive amounts of stones, sand, and mud.
According to Purna Gopal Ranjit, officiating manager of the project, two reservoir gates were opened starting Sunday morning to purge the accumulated debris. During the process, the water tank was completely emptied to leverage high-velocity water currents, a technical procedure known as reservoir flushing. The emergency measure aims to clear heavy sedimentation that posed a severe risk to the trash racks and could potentially damage the plant's turbines. Project authorities set a target to wrap up the maintenance throughout Sunday and resume power generation from all six units at full capacity after 6:00 PM.
While reservoirs are typically scheduled for cleaning twice a year, manager Ranjit noted that early monsoon floods filled the basin much faster than anticipated, forcing an unscheduled intervention.
With the opening of the dam gates, downstream water levels in the Tamakoshi River experienced sudden fluctuations.
The project issued an urgent public notice warning residents living along the riverbanks across Dolakha, Ramechhap, and Sindhuli districts to exercise extreme caution. The public was strongly advised to stay away from the riverbanks and avoid activities such as fishing, bathing, washing clothes, and watering livestock throughout Sunday.
As Nepal's largest domestically funded hydropower project, Upper Tamakoshi plays a crucial role in the national energy grid. However, the mountainous region's weak topography and heavy seasonal rainfall make the facility highly vulnerable to mudslides and heavy sedimentation during the monsoon.
Experts note that if left unaddressed, abrasive silt reaching the turbines can cause catastrophic machinery failure and lead to prolonged plant shutdowns.
Despite the temporary loss of generation during Sunday's 10-hour window, the Nepal Electricity Authority (NEA) reported that overall power supply to the national grid remained stable through alternative management. Project technicians continuously monitored the flushing operation to ensure the plant could safely return online by evening.
