A July night had just fallen over the tiny fishing village of Sdao, on the Sekong River in northern Cambodia, when a man on a motorcycle appeared with an urgent message, delivered by loudspeaker: “Evacuate now,” he called out to the few hundred families living here. “A flood is coming.”
A dam under construction some 155 miles (250 kilometers) upstream, in neighboring Laos, had collapsed the day before after heavy monsoon rains, sending a deluge of water down the already swollen, swirling Sekong. The floodwaters, villagers were told, could reach as far as Stung Treng, the provincial capital in northern Cambodia where the Sekong joins the even larger Mekong River.
Ey Bun Thea, a 24-year-old fisherman and farmer, had no idea that a dam was being built farther up the same river where he fishes every day. But he knew he had to get out quickly. He pulled together some valuables—rice, blankets, mosquito nets, some cash—and after releasing his animals he escaped with his wife and young child into the dark, in search of higher ground. “It was very scary,” he said. “We didn’t know what was going to happen.”
As it turned out, the floodwaters did arrive and filled Thea’s house a meter deep. But the waters soon receded and after a few days the family was able to move back home from the nearby village where they and most of their neighbors had taken shelter. Thea found the animals safe, though his family’s entire vegetable garden had been destroyed.
Closer to the collapsed Lao Dam, part of a hydropower project on the Xepian River, a tributary of the Sekong, the destruction was far more extensive. Inside Laos, several villages downstream from the failed dam were left completely flooded, leaving at least 39 people dead and up to 100 went missing, as well as thousands of people homeless.
The disaster has brought into focus the ambitious agenda of Laos, one of the region’s poorest countries, to turn itself into “the battery of Southeast Asia” by building dozens of hydroelectric dams on the Mekong River and its tributaries and selling power to neighboring countries. Last year, Laos had 46 such power plants operating and 54 more planned or under construction.
But the dam collapse in July has amplified calls for Southeast Asian countries, particularly Laos, to reconsider their heavy investment in hydropower, and there are signs that the tide may be turning in favor of alternative energy sources.
Last week, the Lao government announced that it would suspend approval of new dams while reviewing those currently under construction, a move that was welcomed by the Mekong River Commission. Thailand, meanwhile, is said to be reconsidering its decision to purchase large amounts of hydropower from Laos, as it seeks to instead develop its own solar energy sector.
Zeb Hogan, a fish biologist with the University of Nevada, Reno, who has worked in the region for 20 years, said he was encouraged by the developments.
“If the failure leads to more oversight for dams, better dam design, operation, and placement, as well as quicker moves to alternatives like solar, then there will be less long-term impact on Mekong fisheries and biodiversity,” he said. “This means the Mekong River, as the most productive river on Earth, can continue to provide for future generations as it has for past civilizations.”
The Attraction of Hydropower
Southeast Asia's electricity shortage makes hydropower an attractive energy source. Advocates see the Lao dam scheme as an environmentally friendly solution to reduce poverty in the region. But many experts have claimed that at least some of the dams may be poorly constructed and could fail in a way similar to what happened in July. About one year ago, another dam under construction in northern Laos also broke after heavy rains. Scientists warn that unpredictable and extreme weather events are likely to become more frequent due to climate change.
Environmentalists have long warned that these projects carry environmental costs that are not fully appreciated or factored in to the decision-making. Dams are known to threaten fish populations, cause major soil erosion and alter natural river hydrology, jeopardizing the future of the entire lower Mekong River basin as a life-sustaining ecosystem.
“This tragedy has really placed a spotlight on the security risks of these dams to local populations, and it’s also opened up a broader discourse on the negative environmental impact that we know they will have on the entire region,” said Maureen Harris, who is the Southeast Asia program director of International Rivers, a U.S.-based advocacy group.
Shrouded in Secrecy
The Mekong River originates in the Tibetan highlands and runs through China, Myanmar, Thailand, Laos, Cambodia, and Vietnam before flowing into the South China Sea. It is home to the world’s largest inland fishery, with an estimated 25 percent of the global freshwater catch. Sixty million people make an income off the fish, as well as crops grown along the Mekong River and its tributaries.
China started damming the Mekong in the early 1990s, but the main river has stayed undammed largely due to regional cooperation between the four member nations of the Mekong River Commission, which was established in 1995.
Energy needs and the financial incentives of hydropower, however, caused land-locked Laos to announce more than a decade ago that it would build nine dams on the main river, as well as dozens of new dams on Mekong tributaries. Cambodia and Vietnam soon launched their own dam projects.
Many of the tributary dams are now up and running, with Laos exporting close to $1 billion in electricity in the first nine months of 2017. The first of the new projects on the main stem of the Mekong—the Xayaburi dam in northern Laos—is expected to go online next year.
Critics have complained that the projects are shrouded in secrecy, and independent observers and media representatives are generally not allowed to visit dam sites. There have been many allegations of corruption tied to the awarding of construction contracts.
The Communist government in Laos has also come under heavy criticism for its handling of the dam break last month. Officials initially blamed the flooding on natural causes, and it took several hours for villages downstream to learn what happened. Since no built-in warning system for flood or disaster management between Laos and Cambodia exists, the Cambodian authorities were also left scrambling to inform people of impending danger.
Environmental impact reports done on behalf of dam developers in Laos have routinely downplayed any environmental damage the dams will cause. But independent researchers say the reports do not take into account the transboundary effects and warn that the impact on fish populations in the entire Mekong River basin could be devastating.
Dams may block migrating fish from reaching crucial spawning habitat. They also inevitably alter the hydrology of the river system, which in the case of the Mekong has been fine-tuned over millennia to accommodate one of the most diverse assemblages of fish species anywhere in the world.
“Fish in the Mekong have strongly adapted to the flow regimes of the river,” said Peng Bun Ngor, a fish ecologist with the Cambodian Fisheries Administration. “If the fish cannot adapt to the new system, they’re gone.”
A study by the Mekong River Commission released earlier this year showed that Mekong fish stocks could fall by up to 40 percent as a result of the dam projects. It also predicted a 97 percent reduction in the amount of sediment flowing downstream, which would lower soil fertility and hamper agriculture.
“Study after study has shown the economic and ecological costs associated with hydropower in the Mekong River basin,” said Hogan. “These costs are often ignored, while the benefits of dams are overstated.”
Still, dams may actually boost fish catches in the short term, something Hogan, who spearheads a USAID research project called Wonders of the Mekong, was able to glean for himself on a recent trip up another Mekong tributary, the Sesan River, which originates in Vietnam and flows into Cambodia.
Last year, a new hydropower dam built on the Sesan not far from Stung Treng became operational. The project, which forced the resettlement of 5,000 people, was mired in controversy for years, with conservationists warning of severe ecological consequences. So far, however, fishermen say they’ve been catching more fish near the dam than before it was built.
In the large reservoir created above the dam, “You just have to put the net in for five minutes to get a lot of fish,” said 73-year-old Keo Lut, while admitting that many species are “very fatty,” something researchers say would not be surprising to find in fish living in more stagnant water.
Below the dam, fishermen also say they are catching more fish, such as black sharkminnow and Mekong honey sucker.
“I’m very happy,” said 64-year-old Sing Sathan with a big smile.
But there's reason to think the fishing boom won't last long.
“The increase in fish yields is because the fish are trapped and cannot complete their life cycles," says Hogan, the fish biologist. "Some fish species will adapt to the new conditions created by the dam, many will not."