Dam dangerous

The Nepal government is all set to launch a Rs25 billion project to build a dam inside Shivapuri National Park to flush the Bagmati, wash away its waste and stanch its stench as it flows through Kathmandu.

However, critics say it is an extravagant undertaking that carries financial, seismic and environmental risks, and that the Bagmati can be more effectively cleaned with a sewage network, water treatment plant and better urban solid waste management.  

The Department of Water Resources and Irrigation is planning to build the 95m high dam on the Nagmati stream to also augment Kathmandu Valley’s drinking water supply and generate some electricity. The scheme is an extension of a project funded by the Asian Development Bank (ADB). 

Engineer Nishchal Chhatkuli of the ADB-supported Bagmati River Basin Improvement Project says the environmental impact assessment is awaiting approval and clearing trees and construction of an access road will begin soon. The project is expected to be completed by 2032 by when the reservoir will be capable of storing 9.4 billion litres of monsoon runoff and releasing 450 l/s into the Bagmati River as it starts to flow through Kathmandu 18km downstream. 

The primary purpose of the dam is said to be to flush out the polluted Bagmati River, although some of the water will also be added to the mains connected to the Melamchi tunnel, as well as generate 1.86MW of electricity. 

The Project started in 2013 to improve Kathmandu’s river system under which another 24m high dam has already been built at Dhap, upstream from the proposed dam. 

But the Dhap reservoir was deemed to have insufficient storage to flush the Bagmati all year round, and the ADB supported a detailed feasibility study completed by an Australian company in 2017 that endorsed a higher dam downstream near Mulkharka, 3km above the confluence of the Nagmati and Bagmati. 

“Since water cannot be brought from elsewhere, stored rainwater drained from this lake is the only way to deliver it to Bagmati during winter and take the river back to how it was three decades ago,” Chhatkuli explains. 

The dam construction itself will cost Rs19 billion, and additional money will be spent on protecting the watershed, construction of the power house, drinking water use and building tourism facilities.  

Although the Nagmati project’s stated aim is to protect the river basin, critics say it will come at significant ecological cost to the national park. The environment impact assessment itself says more than 80,000 trees will have to be cut, and the access road will add to human disturbance in the wilderness area. 

‘Permanent effects of the project include loss of local biodiversity, destruction of wildlife habitat, and construction activities that will alter local topography, increase soil erosion, and increase turbidity in the river,’ the report states. 

Nature activist Shrawan Sharma argues that impounding a reservoir of this size will harm the already fragile ecosystem of the Shivapuri- Nagarjun National Park and the Bagmati watershed. 

The current government policy is to replace every tree cut with 10 saplings, which would mean that 800,000 saplings would need to be planted. But there is no land area for so many trees in Shivapuri.

D P Jaisi, an engineer formerly with the Department of Irrigation says the construction of a big dam in an area with high seismic risk directly upstream from a densely populated city is a bad idea. Climate change adds to the risk. 

“Large infrastructure projects need to be future-proofed to withstand major disasters, but such structures are always a risk,” says Jaisi. “If the Nagmati Dam were to collapse, it would be catastrophic for Kathmandu.”

The project’s detailed report does look at a potential dam collapse, and shows that 3.47 million litres per second would rush down to Kathmandu, reaching Sundarijal in 15 minutes and Pashupati within 90 minutes.

“The debris flow in the event of a Nagmati Dam collapse will affect 500,000 people all the way down to Chobhar and even change the course of the Bagmati as it flows through Kathmandu,” Jaisi warns.

Water resources professor at Pulchok Engineering Campus Hari Pandit says the damage would be large-scale and long-lasting. “We simply cannot rely on dam design in a country like ours with its weak governance and weak construction,” he adds.  

Project officials like Chhatkuli say all this is scare-mongering and there is no reason to be alarmed because the dam is designed with the worst-case scenario for seismic and cloudburst risk in mind.

But critics are not assuaged, especially considering the disaster that struck the Melamchi water supply scheme in 2021, Nepal’s biggest infrastructure project so far. An investigation showed that Melamchi headworks and tunnels did not take into account clear and present danger from climate change in the river's headwaters.

Hydraulic structures expert Ravi Rajbhandari with Cemat Consultants says the dam, which will have concrete slabs on one side and rock-fill on the other, will be "like a sword hanging over Kathmandu’s head". He says we should learn lessons from last year’s catastrophic dam breaches in Libya and Sikkim.

Experts also question why the Department of Irrigation is involved when the project has nothing to do with agriculture, and when the Rs25 billion lavished on another big project in Kathmandu could have been spent to irrigate rain-fed farms in rural areas and increase harvests. 

Some experts say the Nagmati project will mire Nepal in another debt trap. The country’s public debt has reached Rs2.38 trillion and now accounts for more than 44% of the country’s GDP. Pouring money into a low-return project like Nagmati will push generations of Nepalis into indebtedness.

Ravi Rajbhandari and Hari Pandit also doubt whether water released from the dam will actually make the Bagmati cleaner if sewage and garbage continue to be dumped into the river. The money could have been spent on extending the Melamchi tunnel to Larke and Yangri to increase water volume.

But the project’s Nishchal Chhatkuli argues that the return on investment from the Nagmati Dam should not be measured only from an economic standpoint. “The price that locals have had to pay for living and being in proximity to the polluted Bagmati is incalculable,” he says. “The advantage of a cleaner Bagmati goes beyond purely financial benefit.”