Environment

With the monsoon officially over, engineers are working to re-divert waters of the Melamchi River into the tunnel to resume supply to Kathmandu Valley.

They hope to complete the tunnel work in a few weeks so that Kathmandu Valley residents can use the water for a couple of months.

But the arrival of the monsoon will mean the closure of Melamchi again.

The tunnel was closed just before the monsoon to avoid potential damage to the 26.5km tunnel.

The project, developed to supply 170 million litres of water per day to around 5 million population in the valley, was damaged by a massive debris flow on June 15, 2021.

'Melamchi mirage'

The debris severely damaged the project's head works, leaving the engineering scratching their heads for a permanent solution to the problem.

Two more rivers - the Yangri and the Larke - will be diverted into the tunnel as part of the $800 million project.

But the 2021 disaster has left a big question mark hanging over the project's vitality. 

Several experts have blamed climate change for the disaster which turned Melamchi into a mirage with no guarantee of year-round water supply to the valley.

Yet to protect the 26.5km tunnel from debris flow and flooding, which is the most expensive part of the project, officials pre-emptively shut down the tunnel just before the monsoon.

The Melamchi Water Supply Development Board has started working to rechannel the waters into the tunnel.

Challenges

But it is easier said than done, said Senior Engineer and Information Officer on the board, Rajendra Prasad Pant. 

He said: "To repair the project, we made temporary roads and bridges along the river banks last year. But they were all washed away by floods this monsoon.

The board is now faced with a challenge to repair the road and bridges along the 8-km stretch. 

"With the end of monsoon, the water level in the river has receded. That has helped us get repair works up to the speed," he added.

The project has set a timeline to reopen the tunnel by mid-November, but it will only work if the tunnel is unaffected by recent monsoon floods. 

Pant said: "We need a road to get those cranes in place to lift those metal shutters."

The board has yet to conduct a thorough inspection to ascertain the tunnel is free from any damage. 

According to him, this monsoon flood cleared a lot of debris dumbed by flooding on June 15 last year. The board is hopeful that clearing the remaining debris will be easier. 

Unlike last year when the project only started working in mid-December, works began earlier this year to divert water to the valley early.

Pant added: "We won't be diverting the water at full capacity right away, but will instead increase gradually over time.

"But everything hinges on the condition of the tunnel. If it's flooded, it may take longer to repair the damage."

The end of the monsoon has cleared the way for the Melamchi project to resume repair work. But it brings along a long dry season. Kathmandu Valley routinely faces a water crisis in the dry season when water tables and water flow in the valley's rivers drop.

Also read: Melamchi shutdown compels engineers to find other water sources