Water supply from the Melamchi Drinking Water Project to Kathmandu Valley has been suspended after flooding damaged a temporary intake dam at the project's headworks in Helambu, Sindhupalchok.

According to technical staff at the Melamchi site, the water first turned heavily turbid at around 9pm on Thursday. Soon afterwards, floodwaters damaged the temporary diversion structure at the intake, forcing officials to stop sending water into the 26-kilometre tunnel the same night.

The flooding was triggered by heavy rainfall in the upstream catchment around the intake area in Helambu.

“The river flow has not subsided yet,” a project technician said. “There is no immediate possibility of resuming water diversion.”

Madhu Timilsina, senior division engineer and spokesperson for the Melamchi Water Supply Project, said no formal decision had yet been made to suspend operations. He said officials were assessing the situation after the water became highly turbid and flood risks increased.

The Melamchi intake has remained vulnerable since devastating floods in June 2021 destroyed the original headworks. The disaster, triggered by a massive debris flow from the Bhemathang area in the Himalayas, caused widespread destruction from Helambu through Melamchi to Dolalghat in Kavrepalanchok.

Although authorities later decided to relocate the intake to a safer site, the project said the final design and report have yet to be completed.

As a result, Melamchi water has generally been supplied to Kathmandu only during the dry season using temporary infrastructure. Project officials said the latest damage to the temporary intake could delay the restoration of supply for an extended period.

The Melamchi project currently supplies around 170 million litres of water a day to Kathmandu Valley. The suspension is expected to affect water distribution across the capital.

To improve resilience during the monsoon, engineers had built a system to divert water from the nearby Ribarma stream whenever flooding made the Melamchi River unsuitable. However, officials said water in the Ribarma stream also turned heavily turbid on Thursday night, forcing them to halt its diversion into the tunnel as well.