In Nepal’s next big quake, hydropower dams threaten catastrophe

Michael Buckley writes in the Ecologist.

A spate of hydroelectric dam building in Nepal means that future earthquakes could send inland tsunamis flooding down the steep mountain valleys, writes Michael Buckley. Disaster was averted in last month’s quake – a badly damaged dam was not yet filled. But despite the risks and the damage to river ecology, tourism and rural livelihoods, there’s no sign of any policy shift.

After the 25th April earthquake in Nepal, China sent in large teams to rescue quake victims. But it was also intent on rescuing its own people.

A delicate operation got under way to reach 280 Chinese construction workers trapped at a dam construction site around 40 miles from the earthquake epicentre.

Two workers were killed by the quake, and others were injured. The 110-MW Rasuwagadhi Dam was being built on the upper Trishuli River in a very remote corner of Nepal near the Tibetan border.

China imports its own construction workers to build these megadams, though locals are used for manual labour tasks. This is one of three megadams currently being built in Nepal by Chinese state-run Three Gorges Corporation, with a dozen more on the horizon for a dam cascade on the Trishuli River.

Three Gorges Corporation has mastered the technology for building behemoth dams, and the projects in Nepal are growing larger: West Seti Dam is slated to generate 750 MW of power.

And underlining the risks it will create, the dam’s reservoir is to stretch back 16 miles (25km), holding back 1,200,000 acre-feet (1.5 cubic kilometres) of water. Just imagine the devastation that would cause if an earthquake let it all go at once!

Three Gorges Corporation has projects around the world, particularly in third-world nations – many of them highly controversial because of environmental concerns. The company itself has been implicated in scandals in China involving corruption and shady practices.

At Rasuwagadhi Dam site, huge rockslides and falling debris hampered rescue attempts: Chinese engineers and construction workers were eventually helicoptered out across the border into Tibet, with assistance from the People’s Liberation Army. A handful of Chinese engineers remained to supervise the damaged site.

Nepalese workers were left to fend for themselves, and trek out.

How long before Nepal’s ‘Fukushima Moment’?

Here’s a statistic: the gigantic Three Gorges Dam in China was built to withstand the forces of a 7-magnitude earthquake, and is able to withstand an 8-magnitude earthquake for a short time, according to the company. That is where the engineering problems lie: the quake in Nepal was 7.9 magnitude.

Rasuwagadhi Dam was described as severely damaged by the quake. And that brings up a nightmare scenario. What if that dam were up and running, with a huge reservoir sitting behind it?

If an earthquake topples such a dam, that would unleash a massive torrent of water and rubble, taking out scores of villages downstream. It would be a Fukushima moment – earthquake followed by tsunami.

Only in this case, an inland tsunami would be unleashed on a river. The megadam becomes a lethal hydro-bomb, piling horror upon horror.

Increasingly, as more dams are built on Himalayan rivers, this nightmare scenario is given more chance of playing out. With the highest mountains in the world on its northern borders, Nepal is particularly rich in hydropower potential.

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