The Yali Falls Dam sits on the Krong Poko River, a tributary of the Se San, in a narrow gorge about 70 kilometers upstream of the Cambodian border. Construction began in 1993, a time when Vietnam was pressing hard into economic development after decades of war and embargo. By 1996 the dam was sealed; by 1998 the 64.5 square kilometer reservoir had filled, submerging the valley upstream — displacing more than 8,500 people, the majority of them Jarai and Bahnar indigenous communities whose villages and ancestral lands disappeared under the water.

The site takes its name from the Yali Falls, a natural cataract on the Krong Poko that once drew visitors to the highlands. The dam replaced the falls with a placid reservoir and a concrete intake structure. In the Vietnamese national energy accounting, the project is a success: 720 megawatts of installed hydropower capacity, clean and reliable. In the accounting kept by Cambodian fishing communities downstream, the ledger reads differently.

What makes the Yali Falls Dam unusual among large infrastructure projects is the geography of its consequences. The Krong Poko flows into the Se San, which crosses into Cambodia and eventually joins the Mekong. The reservoir, the flood pulses from releases, the changed sediment loads — all of these travel downstream across an international border, affecting communities that had no say in the dam's construction and receive none of its electricity.

Cambodian authorities were not formally consulted before construction began. This was the central complaint raised by the Sesan-Srepok-Sekong Protection Network, known as 3SPN, a coalition of 59 villages in northeastern Cambodia organized to advocate for the three river basins. Their backing came in part from Oxfam, which documented the downstream effects in the early 2000s. The pattern was consistent: unexpected releases caused sudden floods, drowned livestock, destroyed fishing equipment, and on at least several occasions endangered people who had no warning the water was coming.

The dam's most-documented incident came in July 2008, when a heavy release flooded communities in northeastern Cambodia. Probe International, a Canadian environmental watchdog, issued a press release documenting the event — one in a series of such releases over the years since the reservoir filled. Fishing communities along the Se San described losing not only their catches but the physical infrastructure of their livelihoods: nets, boats, landing platforms, riverside gardens.

Fisheries decline along the Se San has been documented by researchers since the late 1990s. The combination of altered flood pulses, changed sediment transport, and blocked fish migration routes created conditions in which traditional fishing practices became increasingly unviable. For communities that had fished the river for generations, the dam represented an economic transformation they did not choose and could not easily survive.

The Yali Falls Dam is not unique in this respect — large dams on international rivers create transboundary effects that regulatory frameworks rarely handle well. The Mekong River Commission exists partly to address such issues, but Vietnam and Cambodia's bilateral relationship on water sharing has moved slowly. As of the dam's operation through the 2020s, formal compensation mechanisms for downstream Cambodian communities remained limited.

The dam itself continues generating power, now part of a larger cascade of hydroelectric projects on the Se San and its tributaries. Vietnam's energy needs have grown considerably since 1993, and the Central Highlands' river systems have become central to meeting them. The question that the Yali Falls Dam raised — who bears the cost when infrastructure benefits one country and burdens another — remains as live today as when the first water backed up behind the concrete in 1996.