CHAMPASAK PROVINCE, Laos – Beneath a small wooden house in southern Laos, sits a makeshift laboratory a short walk from the bank of the Mekong River.
Small plastic containers were stacked on a table during a recent visit, each individually labeled with the name of the species inside: monotreta fangi, puntius brevis, pangasius.
By collecting the larvae of fish species native to the Mekong River here, in an area known as the Si Phan Don, or “4,000 Islands,” Malaysian investment company Mega First Corporation Bhd. hope to learn more about fish migration routes in an area slated to host the 240-megawatt Don Sahong hydropower dam.
It will be the first dam on the Mekong’s mainstream, and debate has intensified over the potential damage to fisheries for downstream countries—the project is located just a few kilometers from the Cambodian border.
“There’s a myth that the impacts cannot be mitigated… The final myth is that everyone who relies on fisheries would suffer if this project proceeds,” Peter Hawkins, a senior environmental manager for Mega First—which is building the dam —said a day before he led a group of Cambodian and Vietnamese government officials to the makeshift laboratory to show them the company’s efforts to identify fish species.
“All of these statements assume that success of mitigation is impossible but we are arguing it is possible, that there are existing channels that offer alternative pathways.”
Yet his efforts to convince his visitors that the company’s fish research was thorough left the two delegations unimpressed, as did much of the three-day public relations stunt.
Mr. Hawkins said Mega First had contracted a fisheries expert from Cambodia to help identify the fish larvae species that the company has caught in the water channels. But the Cambodian expert was absent, and when Te Navuth, secretary-general of the Cambodian National Mekong Committee, asked him where the “expert” had worked in Cambodia, Mr. Hawkins said he couldn’t remember.
“Maybe the Ministry of Fisheries,” Mr. Hawkins added.
Though admitting to having no expertise in such matters, Mr. Hawkins repeated throughout the trip that the Don Sahong dam’s mitigation methods would work because of its “location, location, location.”
As the Mekong winds through southern Laos, it splinters into numerous water channels before they merge near the Laos-Cambodian border.
The Hou Sahong channel—on which the dam will be built—is one of seven channels near the border, and Mega First believes that by mimicking the physical characteristics of the Hou Sahong, the two nearest river channels, the Hou Xang Pheuak and Hou Sadam, can be used to divert fish away from their traditional migration route.
“The Hou Sahong is by far the main pathway for fish in the dry season,” said Garry Thorncraft, a fish passage consultant for Mega First.
“There are certain characteristics in the Sahong channel that allow fish to move through it—it has a large amount of water flowing through it and a relatively gentle gradient so fish can swim up and through,” Mr. Thorncraft said.
To mimic the Hou Sahong will involve either widening the Hou Xang Pheuak and the Hou Sadam or making their river floors less steep so that fish would be able to travel through more easily.
“What the project needs to do is provide the same conditions that exist in the Sahong,” Mr. Thorncraft said. “It’s not a matter of inventing a new fish [passage] way or a new design. It’s copying what nature has already shown to be effective.”
But the volume and speed of the water flowing down the Hou Sahong channel is markedly different from its neighboring channels, with their tepid currents and narrow passages.
To generate more electricity, Mega First also plans to maximize the dry-season water flow through the Hou Sahong by excavating rocks in the river’s bed to deepen the northern inlet and removing islands that block parts of the channel.
That will ensure that 40 to 50 percent of the dry season water flowing in the Mekong would be diverted down the channel toward the dam’s four enormous hydropower turbines.
And even Mr. Thorncraft said it would be logical to assume that this would mean a large portion of the migratory fish traveling in the dry season would have to pass through the Hou Sahong channel and try and bypass what he described as “fish-friendly” turbines.
“From there, you could assume that of the fish coming up to migrate, maybe 40 percent would come to the Sahong straight away, and the other 60 percent may go to the other channels,” Mr. Thorncraft said.
The turbines, in theory, will prevent fish from getting killed while passing through because they spin at a slower rate than traditional turbines.
Many are not convinced by Mega First’s and the Lao government’s sales pitch.
While Laos claims that the Don Sahong dam will only be a “tributary dam,” the developer plans to divert almost 50 percent of the Mekong’s waters down the Hou Sahong, which means that it is not merely a tributary anymore, said Stew Motta, a representative for research group Challenge Program on Water And Food, who also attended the trip.
“If you are going to say that 45 to 50 percent of the Mekong is going down the Hou Sahong during the dry season, to me, that would qualify [as a mainstream dam],” Mr. Motta said.
According to the Mekong Agreement—a non-binding document governing all development on the mainstream Mekong River that was signed by the Mekong River Commission’s (MRC) member countries Cambodia, Laos, Vietnam and Thailand in 1995—any hydropower projects on the river’s mainstream must submit to a lengthy consultation process between the countries.
“I think the agreement leaves a lot of things open to interpretation but in general, the spirit of this agreement would suggest that they should do consultation with the MRC countries,” Mr. Motta said.
Viraphonh Viravong, deputy minister of the Lao Ministry of Energy and Mines, disagreed with that interpretation.
“[Lawyers] would all agree that nothing is that clear in…the agreement,” Mr. Viravong said.
“If I want to develop a small development in a small channel in our country, we have to ask other member countries? Is it fair?” he asked.
“There is our sovereignty…. That is why in principle I cannot agree to that” consultation, he said.
There are more than 200 fish species in that area, and the dam will take a toll on them, said Ian Baird, assistant professor of geography at the University of Wisconsin-Madison and one of foremost scientists specializing in fisheries in the Khone Falls area of Laos.
“The dam will definitely impact fish in Cambodia, Thailand and Vietnam. Even the [environmental impact assessment] acknowledges that fish moving downstream will be impacted and the impacts on fish moving upstream remains uncertain,” Mr. Baird said in an email.
“[The dam developers] may not be able to fully solve problems as they go along, and if not, the local people throughout the region will have to pay the price,” he said.
Mega First’s fish passage consultant Mr. Thorncraft was also not entirely convinced given the uncertainties behind the mitigation methods his company plans to test.
“I’m a researcher by profession, so yes, give me another 20 or 30 years of research and I would be much happier at the end of the day,” Mr. Thorncraft said of his abilities to prevent disaster for downriver communities.
Nevertheless, he said, you have to experiment.
“It is a decision you have to make…. The only way to improve these projects sometimes is to work in these projects rather than standing outside and throwing rocks.”
Long Sochet, a Tonle Sap community fishery representative from Cambodia, is one of those who believe such a grand experiment with peoples’ lives is “unacceptable.”
“There is nothing to guarantee the fishes will not be affected,” he said. “Who will be responsible to the fishermen relying on fishing to make a living in the Lower Mekong region, and the river where the fish stocks are affected?”
(Additional reporting by Kuch Naren)
