Will Lower Sesan 2 Dam Be a Food-Security Catastrophe?

Unknown to many Cambodians, damaging environmental changes that may affect the whole country are currently occurring. This is being caused by just one dam, the Lower Sesan 2.


According to one survey, the average Cambodian consumes nearly 64 kg of fish per year, of which 40.3 kg is freshwater fish. The paper “Trading-Off Fish Biodiversity, Food security, and Hydropower in the Mekong River Basin,” published in 2012 in the Proceedings of the National Academy of Sciences, a preeminent US scientific journal, predicts that the dam’s construction will reduce fish resources by 9.3 percent in the Lower Mekong River Basin.

The dam is being built on the Sesan River, one of the Mekong’s tributaries, but the construction site is a mere 1.5 km from the confluence of the Sesan and Srepok rivers. The construction site is also 25 km from the confluence of the Sekong and Mekong rivers. In short, the dam will impact four rivers.

The annual fish run on the Srepok and Sesan rivers, typically seen in May and June, was almost totally absent from both rivers in May last year, according to local residents, possibly because the dam construction has already diverted the Sesan’s flow.

When we visited Ratanakkiri province in September, a man living in Kon Mom district said of the Srepok River: “Until now, if we placed our nets in the morning, there would be fish caught by the evening. About 5 kg would be caught at one time, but now it is only half that.”

Another man living in Lumphat district told us that Mekong River migratory fish that are usually seen in May did not come up the Srepok River. Since then, it “has been very hard to live” as there are no fish to be caught, he said.

It appears the hydropower company that operates the Lower Se­san 2 plans to construct a fish pass to help fish reach spawning grounds, but its effectiveness is in doubt.

Even if fish are able to swim upstream and access the spawning ground, some newly-hatched fry would be unable to swim by themselves and would be carried by the flow of the river to downstream habitats. The huge artificial reservoirs will hinder the movement of the fry. Dam reservoirs destroy shallow areas, sandy beaches and rapids, which form the spawning grounds and fish habitats.

Furthermore, the habitats where more than 200 species of fish live and spawn in the Se­san, Sekong and Srepok rivers have not been carefully studied. Fish born in the region may be migrating through the Tonle Sap lake. If so, the amount of fish caught on the lake may also ­decline.

It has been reported that construction on the Lower Sesan 2 dam is 40 percent complete. Fish survival is already being threatened by dam construction in the upper reaches of the Mekong River and its tributaries, and by the two mainstream dams being built in Laos (the Xayaburi and Don Sahong). The Lower Sesan 2 will further accelerate this downward spiral. The dam will not only block the flow of water, but also sediment, and there is a concern that the dam’s huge reservoir will reduce the flow of fertile soil to the Tonle Sap lake and Vietnam’s Mekong Delta. Almost nothing is known about the implications of this projection.

We understand that the most important local issue when it comes to the Lower Sesan 2 is the relocation of communities that would be inundated and the recovery of their residents’ livelihoods. While the lives of about 5,000 indigenous ethnic minorities will be adversely affected, the dam’s overall impact is likely to be far greater.

Residents affected upstream from the dam’s construction, mostly in Ratanakkiri province, are thought to number around 78,000. Additionally, as many as 1.2 million people estimated to be engaged in the fishing industry in the area surrounding the Tonle Sap lake will be directly affected. If there are serious effects on the lives of these people, who is going to take care of them? Who is going to provide the cheap and high-quality protein that will be needed as a substitute for fish? Will the organizations that are funding the dam—Royal Group, China’s Hydrolancang International Energy, Chinese banks and Vietnam’s EVN International Joint Stock Company—be able to do this?

The Cambodian government and the implementing organizations should pay attention to the concerns of the people who live both upstream and downstream of the Lower Sesan 2—especially with the food security issue in mind.

Yuka Kiguchi is the director of Mekong Watch.

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