Large hydropower dams are controversial across the world, but if the experts are right, this dam will be far more damaging than most.
Reporter: Robert Carmichael
Speakers: Pa Tou, resident of Srekor village; Dr Eric Baran, Senior Research Scientist at the WorldFish Centre
CARMICHAEL: A small herd of water buffalo beats the afternoon heat in the cool waters of the Se San River. Nearby Srekor village is a tranquil place of 400 families that has stood on the southern bank of the Se San River for as long as anyone here can remember. It won't be here much longer: in the next year or so, the residents will have to leave.
The reason? A vast hydropower dam with an 8-kilometre-long wall will be built downstream. Its reservoir will cover more than 300 square kilometres, and once the waters rise, Srekor village with its stilted, wooden houses, its well-established garden compounds and its mature fruit trees will be swallowed up.
Pa Tou, a 37-year-old father of three, has lived in Srekor village all his life.
(PA TOU ACTUALITY) I spoke to him earlier this year. Like most residents Pa Tou is from the ethnic Lao minority, he farms rice on a small plot of land and he knows a lot about the river and fishing. Pa Tou says all of the villagers fear for the future and none wants to leave.
Pa Tou says the dam will deprive them of everything - homes, crops, fruit trees and their livelihoods. Later he tells me that the relocation site the authorities have offered
CARMICHAEL: The 400-megawatt Lower Se San 2 Dam, which will cost around 800 million dollars and take five years to build, is a joint project involving companies from Cambodia, China and Vietnam.
An estimated 10,000 people will be moved for it, and there are more dams to come on the Cambodian side: at least two more are planned upstream on the Se San River; another two are scheduled for the neighbouring Sre Pok River; and one on the Se Kong River. Collectively these rivers, known as the 3S network and which empty into the Mekong, constitute a vital regional breeding ground for fish.
Conservationists warn such mega-projects represent a huge risk. A study published last year in the US Proceedings of the National Academy of Sciences found that plans to build more than 70 dams in the Mekong River Basin would have a "catastrophic" impact on the world's richest freshwater fishery.
Dr Eric Baran is one of the authors of that study. His team assessed 27 dams that regional governments plan to build on tributaries of the Mekong. He says the Lower Se San 2 Dam will be by far the most detrimental for fish.
BARAN: We found that the fish yield loss due to this dam would represent 9.3% of the total fish yield of the Mekong Basin. So it's 9.3% of 2.1 million tons - which is a gigantic amount. In other words, this expected loss represents around 200,000 tons per year, which is much more than the whole marine sector of Australia.
CARMICHAEL: The Lower Mekong Basin is shared by 65 million people in four countries. Given that many of those people are poor and rely overwhelmingly on freshwater fish, there are well-founded fears that hydropower dams will cause many to go hungry. Take Cambodia, for instance, whose 15-million-strong population eats more freshwater fish per capita than any other in the world.
BARAN: People have become very reliant on this source of animal protein. It represents 81 percent of the animal protein consumption in the country.
CARMICHAEL: Hydropower is a central part of this region's scramble for electricity. Cambodia imports much of its electricity from Vietnam and Thailand, yet there is seldom enough.
Opponents of large power projects say the focus should be small and local - generate electricity where it is needed. The argument is that such local projects are cheaper, quicker, and more efficient…and do far less environmental and social damage.
Government officials declined to speak with Radio Australia for this story. However, Prime Minister Hun Sen's comments earlier this year make it clear that the preference is for large schemes - such as hydropower dams and coal-fired plants. The Lower Se San 2 Dam is unlikely to be the last of its kind.
Back in Srekor village, Pa Tou's concerns extend beyond how he will provide for his family. He worries too about the village graveyard that lies a mile downstream. He took us to see it, weaving expertly through the rapids on the Se San River in his low, wooden boat.
Within this bamboo thicket are several small spirit houses containing bones and ashes with offerings of food laid out. Villagers come here regularly to pray and leave offerings for the deceased.
(PA TOU ACTUALITY) Pa Tou says the villagers of Srekor have asked the authorities for permission to take the remains of their dead with them, but worry they won't be allowed to. This is important to them, he explains, because when he and the other villagers eventually die, they want to be reunited with their ancestors.
CARMICHAEL: With that, it was time to leave, and we clambered back into Pa Tou's narrow boat. He sparked the motor into life and guided us upstream through the tangle of rapids and back to Srekor village, a vista of rural life in Cambodia that in a few years will have entirely disappeared.