Heavy rains preceded the Laos dam collapse. Was climate change a factor?

Two weeks after a dam in the Xe-Pian Xe-Namnoy hydropower facility collapsed in southern Laos, sending millions of tonnes of water crashing through villages downstream, authorities are still counting the dead. The official death toll is at least 31, but at least 130 people remain unaccounted for, which could push the final figure much higher. Rescue teams are still searching for survivors, while thousands of villagers reside in emergency shelters, not knowing if they will ever be able to return to their homes now submerged in floodwaters.

Authorities are now looking into why the dam burst. The initial scrutiny is focused on the dam’s structural integrity. Laotian Energy and Mines Minister Khammany Inthirath echoed a chorus of observers when he blamed the accident on the project developers: two companies from South Korea, and one each from Laos and Thailand. “I am fairly certain that the construction technique for the dam was poor, which led to a collapse during heavy rainfall,” he said.

The companies building the dam say it is too early to say why the accident happened, and have emphasized the monsoon rains that inundated the structure in the days leading up to its collapse. But Ian Baird, a geography professor at the University of Wisconsin, Madison, who has studied the hydropower project, wasn’t convinced. “When at the end of July do we not get rain in this part of the world?” he asked. The companies are “trying to play this out as a natural disaster that wasn’t their fault.”

But in the long run, another question may prove just as significant: To what extent was the heavier-than-usual rainfall that pushed the dam past its breaking point a result of climate change?

Globally, the evidence suggests climate change is altering weather patterns, increasing the frequency of extreme events like drought and heavy rains, according to Donald J. Wuebbles, a professor of atmospheric science at the University of Illinois at Urbana–Champaign. “Basic physics tell us that a warmer atmosphere can hold more water vapor and this leads to larger precipitation events when the weather pattern is right for it to rain or snow,” he told Mongabay. The latest report by the U.N. Intergovernmental Panel on Climate Change, he added, shows that “most of the world is seeing an increasing trend in severe precipitation that is directly related to the changing climate.”

In the Mekong Basin region, where Laos is located, there has long been evidence that climate change is resulting in more intense rain events. And this summer, the Laos dam breach was not the only disaster in Asia preceded by unusually heavy rains. In early July, “historic” rainfall in Japan caused massive flooding and landslides, killing at least 155 people and displacing hundreds of thousands more.

When it comes to Laos itself, though, the question of changing rainfall patterns is a little less clear. This is due to gaps in the data from observation stations in the country, according to Colin Kelley, senior research fellow with the Washington, D.C.-based Center for Climate and Security. “The problem with Laos is that we don’t have great observation tape, or [there is a] gap in the observation records for some of the observation stations that we have, or maybe we have a record that goes back only 20 or 30 years,” he said.

“That doesn’t mean it’s not happening,” he added. “But we just can’t say it with any kind of confidence.”

David R. Johnson, a Purdue University assistant professor who studies climate change and infrastructure risks, agreed. “It would be very difficult to detect changes in the likelihood of extreme rainfall events with only 20-30 years of spotty records,” he said. In Harris County, Texas, where Houston is located, for example, “We have multiple rain gauges with fairly continuous records stretching back 50 to 80 years or more.”

Climate models already indicated that “heavy rainfall events will increase in intensity over the century as a result of increasing greenhouse gases, both in the Mekong region and in many other parts of the world,” said Michael Previdi, an assistant research professor at Columbia University, who studies climate change and the hydrologic cycle. In general, though, “any individual severe weather event cannot be attributed to climate change,” he said. “The more appropriate question to ask is: did climate change increase the likelihood that such an event would occur? It’s often said that climate change in essence ‘loads the dice’ and makes certain types of severe weather events — such as heavy rainfall events — more likely.”

Maureen Harris, Southeast Asia program director at International Rivers, said she believed the Laos dam collapse was a “human-made disaster and not a natural disaster, and that the developers of the project are responsible for the damage and loss.” However, she added, “There is a major concern that dams are not being designed — and potentially cannot be designed — in a way that adequately addresses future climate patterns.

“Dam design standards rely on historical climate trends, however in an era of climate change, previous weather patterns have less and less predictive value. This raises questions about safety issues and whether dams — which often have a lifespan of over fifty years — are being built in a way that can handle these increased risks.”

For Laos, whose government has embarked on a dam-building spree in hopes of transforming the country into the “battery” of Southeast Asia, the question is a pertinent one.

It’s also a question the rest of the world has to deal with, says Kelley of the Center for Climate and Security, amid an increase of infrastructure “shocks” linked to extreme weather as the planet warms. “Obviously this dam had some kind of a threshold of vulnerability and that was exceeded,” he said. “So [as we’re] starting to see more of these kinds of things, extreme events that are causing some kind of an abrupt shock, it’s due to exceeding some level of vulnerability.”