Seismic impact on Himalyan hydropower development

The huge earthquake that rocked Nepal this week and killed more than 4000 people has had a profound impact on the national infrastructure. One of the worst ‘quakes to hit the region for the better part of a century, images of the damage to roads, bridges and buildings are dramatic.

Already one of the world’s poorest developing nations prior to the 7.9 magnitude event, perhaps more significant for the country’s longer-term future is the potential impact on hydropower development.

Certainly, reports are already emerging that suggest hydropower installations may have been affected by the seismic event, though no outright failures have been revealed so far.

For example, according to Reuters, more than 250 workers have been trapped at the Rasuwagadhi Hydropower site, located in northern Nepal some 70 km from the epicentre of the earthquake.

One of three projects in the country under development by the China Three Gorges Corp, roads to the dam have been cut off and the project has reportedly been damaged by the event. A number of deaths at the site have also been reported, though considerable uncertainty remains regarding the extent of the damage to the nation’s numerous hydro plants.

Whatever damage to existing projects may ultimately be revealed, there is no doubt that the national economy has been set back. Nepal already operated under a system of rolling blackouts as the Nepal Electricity Authority struggled to meet power demand. Nepal has an installed generating capacity of just 800 MW or so, significantly lower than its 1400 MW peak demand. If any hydropower projects are damaged – as seems likely – power capacity will undoubtedly fall further while repairs or rebuilding takes place.

Furthermore, hydropower had been widely tipped as a route to future economic development for the Himalayan nation. Nepal has an estimated 42,000 MW of economic hydropower potential provided by its mountainous geography. And, sitting between India and China, much of its power generation potential was slated for export to its power-hungry neighbours. This strategy was expected to bring in much-needed cash flow.

Indeed, just two weeks prior to the earthquake, Nepal's investment board cleared China Three Gorges Corp to build a $1.6 billion new hydropower project on the West Seti River with a rated capacity of 750 MW. This project is the latest in a series of major infrastructure investments in the country backed by its powerful bordering nations.

However, the future of Nepal’s hydropower development will inevitably now demand significantly greater attention to structural integrity in the face of seismic events.

As Martin Wieland, Chairman of the ICOLD Committee on Seismic Aspects of Dam Design, noted in his 2012 paper: “In view of the short earthquake catalogues and the incomplete information on seismicity, the estimate of the seismic hazard is very difficult and involves major uncertainties especially for earthquakes with long return periods”.

But Wieland also observes that “the history of earthquake engineering has shown that the earthquake design criteria have always increased either as a result of new seismological information but also due to increasing safety demands of the people affected by strong earthquakes”.

This suggests that in the wake of this event, Nepal’s hydropower development plans must be reassessed for more rigorous seismic safety and this may infer additional costs. Nonetheless, Wieland concludes that though dams are not inherently safe against earthquakes, the “technology for designing and building dams and appurtenant structures that can safely resist the effects of strong ground shaking is available”.

It is crucial for the economic development of Nepal and its neighbours that this technology is applied to future hydropower projects in this - infrequently - geologically active region.

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