BANGKOK – The Xayaburi hydro dam that blocks the Mekong River in Laos includes a system of passages and locks intended to keep fish moving up and down Southeast Asia’s longest river.
Six years after the dam began operating and despite research funded by Australian aid, there are still doubts this system, intended to protect freshwater fisheries that are crucial to millions of people, works.
What is Xayaburi dam?
The Xayaburi dam is the first of numerous major dams planned for the Mekong, mostly in Laos. Some research has predicted the Mekong fishery – a chief source of protein and livelihoods for tens of millions of people in Southeast Asia – will decline by half if all are built.
It is well established globally that hydro dams destroy fisheries because they prevent migratory species of fish from reaching feeding, spawning and nursery habitats.
Arguments and activism against more dams could be strengthened if it is shown the Xayaburi fish passage is ineffective.
What is the research about?
Since 2019, fisheries experts from New South Wales-based Charles Sturt University have received Australian government funding to study the Xayaburi fish passage. Last year, they got further funding to extend the research until 2029.
The researchers have a confidentiality agreement with the dam operator, Xayaburi Power Company Ltd., which has a final say about what information is released and how it is portrayed.
The experts have published some research but not responded to questions on the record because of the confidentiality agreement.
They, in funding proposals obtained under Australia’s Freedom of Information Act, say it’s inevitable more dams will be built on the Mekong. They also point out that the economic and social case for the hydro dams is tenuous.
Citing Xayaburi, they pointed out it is projected to generate only modest profits whereas the potential damage to Mekong fisheries, which have an annual value of US$7-$8 billion, and the economies of Thailand, Laos, Cambodia and Vietnam is high.
Still, the researchers say their work could help improve the performance of fish passages and influence the design of future dams. They say they have a narrow window of opportunity this decade to mitigate damage to the Mekong.
How did they conduct research?
The Australian researchers working with Lao counterparts and Xayaburi Power Company staff used electroshock fishing to stun and capture several thousand Mekong fish.
They are implanted with a microchip encased in a glass tube and released back to the river – many in the vicinity of the Xayaburi dam. Between 2019 and April 2024, nearly 4,900 microchipped fish were released into the Mekong.
Antennae at the entrance and exit of the 480-meter long fish passage that extends from the right of the dam detect the microchips.
The researchers said the results are “promising” because over a three-year period more than 80% of the 1,290 fish that were detected at the entrance were also eventually detected at its exit.
That figure is less promising in another light – only some of the microchipped fish ever find their way into the fish passage. And once at its exit there’s another step to get beyond the dam – moving through intermittently operating locks.
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In September 2022, another antennae array was installed to detect microchipped fish that had moved through either of two locks and got past the dam.
Researchers said 400 microchipped fish were detected beyond the dam over nearly two years. That appears to be only a small proportion of the fish released at the dam.
The researchers calculated that percentage, but have not released it nor the number of fish released near the dam.
They noted it was challenging to calculate an “unbiased estimate” of the locks’ effectiveness because their antennae were installed three years after the research program began and they also had outages.
As the research has continued, there is now likely more comprehensive data but because of the confidentiality agreement it is not clear it will be published.
Did the researchers face constraints?
The Australian researchers stressed the importance of studying whether fish can get past the dam in both directions — moving up the river and down it.
However, for the first five years of the research, they lacked a sufficient budget to do that and Xayaburi Power Company had requested they only study upstream migration. It’s unclear why the company imposed that condition.
A major shareholder in the dam, Thailand’s CK Power, did not respond to RFA’s questions.
The researchers suggested there were political advantages to a limited scope of research even though it would limit the applicability of their work to other dams.
“Focusing on upstream migration, at least initially, effectively mitigates a series of risks because our team is only focusing on one aspect,” they said. “The political pressure to provide answers to all migration questions is significantly reduced by this focused scope.”
How do other experts view the research?
According to a study published last year, the researchers released more than 230 microchipped fish into the Mekong River in April 2022 some 350 kilometers (217 miles) downstream of the Xayaburi dam.
More than a year later, five of those fish were detected in the dam’s fish passage.
The study said the results showed the importance of including fish passages like that at Xayaburi in future Mekong dams.
Other experts said the data underlined the dangers since the fish had migrated through locations where planned dams would block the river.
Another point critics of Mekong dams make is that they’ll have compounding negative effects on fisheries.
Even if something like 50% or 60% of fish could get past a dam, each successive dam would quickly whittle down the proportion that completes the entire journey to a single-digit percentage.
Edited by Taejun Kang.