Nagmati won't clean Bagmati

An expensive reservoir upstream is not the way to clean up Kathmandu's polluted river.

The Nagmati inside the national park near the proposed dam site is a boulder-strewn stream. Photo: KUNDA DIXIT

Over the last three decades, Nepal’s national government has spent Rs2.1 billion to beautify the holy river that flows through the capital. The Bagmati is still a cesspool. Now, the government wants to take a big loan to build a 95m high dam inside the Shivapuri-Nagarjun National Park to flush the river.

As we reported last week, it is an expensive bad idea. The reservoir carries seismic, ecological and financial risk.

So far, attempts to rehabilitate the river have resulted in constricting its flow into narrow canyons, building walkways and planting trees along its banks. To be fair, the Bagmati would be uglier without these half-complete measures. But storing monsoon water to regulate the flow of the Bagmati will not clean it up if we keep on dumping the city’s sewage and garbage into it.

The new Rs25 billion project funded by the Asian Development Bank (ADB) to build the dam is being justified because ‘there is no other viable option to preserve the Bagmati civilisation’.

The proposed dam on the Nagmati stream which is a tributary of the Bagmati in the dense forest of the national park will be just 18km upstream from the city centre. It will create a reservoir 50 hectares in area. 

When released in the dry season, the stored water is supposed to wash away the waste, flush the stench of sewage, and raise the level of the aquifer. However, no amount of water released into the Bagmati will clean it as long as it continues to be a sewage canal and a dumping ground for solid waste. 

Even the project's Environmental Impact Assessment (EIA) report concedes that the quality of water in Bagmati can only be restored by blocking the direct discharge of sewers into the river. 

We talked to engineer and former joint secretary at the Ministry of Drinking Water Rajan Pandey. He has calculated that even when 450 l/s of water is released from the reservoir, it will only raise the water level in the river by 3cm. 

Officials directly involved admit that water released from the dam will not be sufficient to purify the Bagmati, but argue that it will “dilute the pollution” and buy time to divert sewers to wastewater treatment plants. But the construction of that system has already been delayed by more than 30 years.

As Nagendra Sitoula of Tribhuvan University Institute of Engineering Studies told us, “The Nagmati dam is like pouring a bucket of clean water into a tank full of dirty water in an attempt to clean it up. It is pointless.”

Pollution in water bodies is measured with a unit called Biological Oxygen Demand (BOD) representing the amount of biodegradable organic matter in the water. The higher the BOD, the more polluted the water.

Drinking water has a BOD of 1 ppm (parts per million). At Sundarijal, the Bagmati has a BOD of 2 ppm, and a dry season measurement of the river after it has flowed through the city at Chobhar last year showed 340 ppm. It is clear that no amount of water released from the proposed dam will dilute the Bagmati’s contamination.  

The Nagmati Dam will be a white elephant nearly as expensive as Pokhara airport, and similarly will have no immediate economic return. The Rs25 billion ($189 million) loan to finance this project will increase the inter-generational debt burden of Nepalis.

Rs25 billion could build 500km of two-lane black-topped highways connecting Nepal’s remote districts, or irrigate one-third of Nepal’s arable land increasing food production. Instead, the money is being lavished on an already pampered capital.  

The disaster in 2021 that nearly destroyed the $800 million Melamchi project supplying drinking water to Kathmandu should have been a lesson that such mega schemes are at increased risk from the impact of climate breakdown in the Himalaya. Weak governance and unreliable construction practices make large-scale development projects even more risky.

A collapse of the Nagmati Dam would wash away Pashupati, roads, bridges and houses all the way down to Chobhar directly impacting 500,000 people in Kathmandu Valley. Then there is the ecological cost of submerging a large area of the carefully protected Shivapuri watershed. 

The Nagmati Dam also exposes the inequity of yet another expensive Kathmandu-centric project when less than 25% of Nepalis have clean drinking water, and much of the Karnali suffers chronic food insecurity. It also lays bare the misguided priority of international lenders just out to expand their portfolios.

Ramesh Kumar