SIEM PANG, Cambodia — Kang Ngan isn’t sure what a dam is. She doesn’t know how old she is, although she thinks “over 30” is a good guess. But she has lived long enough to know that something is terribly wrong along the Sekong River.
The rhythms of life here in Siem Pang, Cambodia, are tightly bound to this sleepy, brown tributary of the Mekong, which swells annually during the monsoon season, then gently spills its banks in October.
But last week, the waters rushed up three months early. Thousands of people in this remote northeastern district were displaced, including Ms. Kang Ngan and her community, who are members of the Kavet minority.
The deluge was caused by the failure of a dam in neighboring Laos, about 50 miles north. The accident devastated a large swath of that country’s Attapeu Province, drawing international media attention, but few noticed when the floodwaters rushed downstream and into Cambodia.
Nobody has explained to Ms. Kang Ngan and her neighbors exactly what happened, although some have heard rumors that the water came from Attapeu. She interprets the flood as a terrifying natural disaster, just the latest stroke of bad luck in an already unlucky life, lived on the margins of an already poor country.
“It was difficult then and now it’s double — triple — difficult,” she said.
Her family’s vegetable garden and small rice field are now ruined, leaving them with only the rice they had stored and no new harvests for the foreseeable future.
“It’s all flooded, it’s finished,” she said quietly. “I barely have anything to eat. I have nothing.”
Events like this may become more common as Southeast Asia embraces lucrative hydroelectric projects that harness the same natural resources its people depend on for survival.
Siem Pang sits in what is known as the 3S Basin, where the Sekong, Sesan and Srepok rivers flow in a tangle of silt and lush greenery into the Mekong. The 3S basin is one of the biggest and most important Mekong watersheds, described by the International Union for the Conservation of Nature as “a bread basket for over three million people.”
But it is increasingly dotted with dams. More than 60 have been built on the basin’s rivers in the past 25 years, altering water and sediment flows and depleting fish stocks. About 50 more are planned or under construction.
Forty miles south of Siem Pang, a Chinese-funded dam called Lower Sesan 2, which started producing electricity late last year, has already displaced 5,000 Cambodians and could devastate fish stocks that feed tens of thousands more.
Ian Baird, a professor of geography at the University of Wisconsin-Madison who has done research in the area, said the 3S basin was highly multiethnic, with most villagers subsisting on food from rivers and forests.
“These are places with relatively poor people who rely heavily on what have historically been very abundant natural resources, which are now being damaged,” he said.
Rivers also have little respect for national boundaries. The Mekong tumbles through six countries before emptying into the South China Sea. The 3S rivers wind more daintily through Vietnam, Cambodia and Laos. But cross-border cooperation here is severely lacking.
The Mekong River Commission, established in 1995, was meant to ensure that dams did not harm the river’s fragile ecosystem or affect villagers downstream, but its provisions are nonbinding and its consultation process has been criticized as toothless. It has essentially no say over dams built on key tributaries like the Sekong.
“There is currently no single standard or set of requirements in the Mekong basin for assessing and compensating transboundary impacts,” said Maureen Harris, Southeast Asia program director for the conservation group International Rivers.
Dr. Baird, the geography professor, said there were also no formal cross-border emergency communications systems in place, even though it was obvious that water released in Laos would quickly reach Cambodia.
“It is a really big problem and weakness,” he said.
The Xe-Pian Xe-Namnoy Power Company, the joint venture behind the failed dam, has an agreement with the Lao government that was not made public but seems to include no provisions for cross-border compensation.
One of the two South Korean firms involved in the joint venture, SK Engineering and Construction, declined to comment on whether it would take responsibility for the flooding in Cambodia.
This will not surprise many people in Siem Pang. While they have received some food aid, nobody interviewed said they even dreamed of compensation. They assume they have been forgotten, even by their own government.
“It’s hard when they don’t help us,” said Chhum Pang, who thinks she is over 60.
“All the plants died. The vegetables that I grow are gone,” she said. “I don’t know what to do. I’m out of hope now and have only regret.”
When the flood hit last week, Cambodia was in the midst of preparations for its national election, in which victory was assured for Prime Minister Hun Sen, the country’s increasingly authoritarian leader. Despite the chaos, the authorities in Siem Pang ensured that as many people as possible still turned out to vote on Sunday.
Siem Pang’s governor, Phann Yuth, a member of Mr. Hun Sen’s party, said Sunday that the government had distributed noodles and drinking water, as well as deployed soldiers to evacuate and transport villagers by boat, but lacked the funds to do more.
That same afternoon, a group of displaced pregnant women was sheltering in the district hall, seemingly unsupervised.
“They said they were busy with the election, and if we need any help we can call them,” said Meuy Lah, 60, who was there with her pregnant daughter and said she was low on food. “But they don’t pick up.”
Ms. Kang Ngan and her husband, Phlen Dinh, were hunkered down by the banks of the Sekong earlier on Sunday with their 3-year-old daughter, Losh, prepared to wait up to 12 hours for a boat that would allow them to cross. The family had not eaten since the previous day, and did not expect to until sundown.
They were trying to reach home after a visit to the district health clinic, which ended abruptly after they ran out of money.
Once they got started, the nine-mile journey took seven hours by boat and foot through muddy floodwaters, with Ms. Kang Ngan balancing nearly 20 pounds of rice, blankets and clothing on her head. When they arrived home, the only food there was a packet of Vietnamese instant noodles.
A group of neighbors crowded around and began reminiscing about what meals had been like just a week earlier, when they included potatoes, eggplant and pumpkin. Asked if they ever ate meat, they laughed.
“Not for us,” said Chhim Bunhong, 31. “For us, maybe we’d go to the river and catch a fish. But now there are not so many fish.”
They said they were eating mostly rice seasoned with salt and chiles, supplemented by government-distributed dry noodles.
“Without more rice, we are going to die soon,” Mr. Phlen Dinh said.
Like many people here, they could not imagine a world in which they did anything but subsist on the land and water, and in which their fortunes did not rise and fall with the Sekong.
“What can we do? We’re ethnic,” Ms. Kang Ngan said. “We don’t know how to earn money like the Khmer and the Lao. We only know how to farm rice, and now there is nothing.”