The Lower Mekong Basin ranks third in the world in fish biodiversity, behind only the Amazon and Congo River Basins, with 1,148 species reported, according to the MRC. It is also the world’s largest inland capture fishery, generating an estimated 2.3 million tonnes of fish and US$11 billion annually, and supporting millions of people. Photo: Sayan Chuenudomsavad

PHOTO ESSAY: Phou Ngoy Dam, The Recurring Fear

Fear is spreading downstream. It is now recurring in communities along the Mun and Mekong Rivers in Ubon Ratchathani province in the northeast as well as in southern Laos, especially Champasak Province, where the latest hydropower dam project on the Lower Mekong mainstream is being advanced toward the Mekong River Commission’s official Prior Consultation process — Phou Ngoy.

At 76, Sompong Viengchan cannot yet retire.

Mae Sompong (Mother Sompong) was once a villager-turned-community leader of “Pak Mun” protests, who had rallied along with hundreds of villagers in the 1990s to protest against the 136 MW Pak Mun hydropower dam built near the mouth of the Mun River, the Mekong’s major tributary in the Lower Northeast.

The protests reached their height in the late 1990s when they set up “Mae Mun Man Yuen” (Relentless Mun) village at the dam site and had camped there for nearly two years to demand alternative dam operation to relieve their suffering and compensation for the losses of their fishing occupation and livelihoods.

Mae Sompong had since become an iconic villager-turned-leader, representing the first relentless mass social movement against unsound development in the country. The movement later turned into the country’s biggest grassroots gathering, named “Assembly of the Poor”.

But just last year, in a meeting with the Ombudsman, she found herself voicing opposition to another dam — Phou Ngoy.

“We have fought with Pak Mun Dam for many years, but up until now we have not received proper compensation for the livelihoods we have lost yet. This is despite the fact that it’s in our soil and under our law. 

“And then you are going to build Phou Ngoy, which is located in Laos’ territory. May I ask: how can we fight with it to protect what we have left?” questioned Mae Sompong.

Phou Ngoy Dam is the seventh hydropower project proposed for the MRC’s Prior Consultation (PC) process since 2020, but the commencement PC date has not yet been determined, pending additional data collection and studies, as well as the completion of the PC process for the sixth proposed project, Sanakham. 

According to the 2022 Environmental Impact Assessment report for the project, Phou Ngoy, developed by Charoen Energy and Water Asia (CEWA), will be a 728 MW run-of-river dam with a height of around 98 metres, stretching across the Mekong River. It will be part of a system of 11 cascade dams planned on the Lower Mekong mainstream, approximately 1,360 km downstream from the first dam, Xayaburi, and around 130 km upstream from the second dam, Don Sahong.

Designated around 18 kilometres downstream of Pakse Town in Champasak, the dam will be only around 60 kilometres downstream from the Mun-Mekong River confluence in Khong Chiam District in Ubon Ratchathani. This proximity has prompted local residents along the distance to become concerned about the possible impacts it may have caused.

According to the Ubon Monitoring Group on Flood and Mekong Dams (UMFD), in which Mae Sompong is taking part, the residents in the area are particularly concerned about the transboundary backwater caused by the impoundment of the dam. They are concerned that this backwater could worsen prolonged flooding in the area.

As explained by the group, Ubon Ratchathani Province is a major basin in the northeastern region that receives an enormous volume of water from watersheds and from various dams in the Mun and Chi River basins — be they Ubolratana, Lam Pao, Rasi Salai, and Huai Na. This amount of water is usually released into the Mun River during the rainy season and then into the Mekong River at Khong Chiam District. 

In some past years, the situation worsened as the sluice gates of the Pak Mun dam had obstructed the flows of the floodwaters, as happened in 2022. In that year, the province faced the most severe flooding that had extensively damaged homes, caused economic hardship, and disrupted educational opportunities for children and youth for more than three months. The cost of the damage was estimated to have exceeded ten billion baht.

With the backwater from the new dam, their situation could become gravely exacerbated as it will impede the drainage of those floodwaters, the group said. More critically, the dam could cause other transboundary impacts that affect fishing communities and livelihoods along the Mun and Mekong Rivers, which have already worsened as a result of the Pak Mun dam. 

Aside from the change of the river flow regime and sediment flow of the Mekong River, the dam could disrupt fish migration and the aquatic ecosystems along the river, depleting their populations and biodiversity there over time. 

The dam’s location is just around 130 kilometres upstream from the unique and complex braided channels system, Siphandone (Four Thousand Islands), locally dubbed as the “capital of Mekong fish.” It would permanently block the migration of the fish from Siphandone up and down the stretch of the river, affecting communities and their livelihoods on both the Thai and Lao sides of the border, the group noted.

Their concerns have grounds. According to the examination by the National Human Rights Commission and the EIA of the project itself, the project could trigger transboundary impacts, as expressed by the residents.

For instance, the EIA noted that the pondage area of the dam could stretch up to 80 km. Therefore, the operation of Phou Ngoy would cause submergence of the Mekong River and tributaries along the pondage area, including the Mun River in Thailand and around the Kaeng Tana rapids nearby.

The EIA also addressed that the dam site is situated at the lower part of the “Middle Mekong migration zone”, and just above the boundary of the “Lower Mekong migration zone”. The project will significantly obstruct fish migration of the Middle zone to the tributaries and the mainstream to some extent, the EIA noted.

“There will be a transboundary impact issue,” the EIA noted.

Phairin Sohsai, a campaign manager of the Rivers and Rights Foundation, campaigning for river rights and sustainable development projects in the Lower Mekong, said regarding the necessity of the project, Phou Ngoy Dam will not be needed to help Thailand meet the demand for the next seven years. 

In the next five years, she said, the Mekong dams with ongoing construction, including Luang Prabang, Pak Lay, Pak Beng, Sekong 4A, and 4B, will contribute more than 3,395 megawatts to the grid, and this volume of electricity capacity will far exceed the country’s electricity demand. Furthermore, alternative energy like solar power and wind power becomes cheaper, compared with hydropower dams that cannot generate electricity all year-round, Ms. Phairin said.

As of last year, electricity purchased from foreign countries already accounted for 6,235 MW, or 12% of the country’s installed capacity, according to the Energy Policy and Planning Office (EPPO). In 2024, the country planned to increase this share from 7% to 15%.

As noted by the EPPO, the maximum electricity demand recorded this month was about 34,620 MW. By the end of last year, the country’s installed capacity had already reached 54,336 MW, indicating a significant excess of the power reserve margin, which typically stands at 15–20%.

“Villagers around Pak Mun say even with a dam located in our own country, the government hasn’t resolved the problem. So, what legitimacy will it have to demand that the dam developers take care of transboundary impacts that may arise from their projects outside our territory?” Ms. Phairin lamented.

Mae Sompong just asked: “What would you (the government) do to resolve the problem for us if Phou Ngoy is built?”

(Read: SPECIAL REPORT SERIES: Mekong in Peril)

The 2010 SEA noted that the Lower Mekong migration zone, where the iconic Siphandone and Khone Falls are located, is by far the area that exhibits the highest species diversity of the Mekong’s fish, with 669 species recorded. The study stated that this high diversity is largely due to the conjunction of freshwater, estuarine, and marine fish faunas, particularly due to the incursion of coastal species into freshwater areas, as far as the Tonle Sap or even further upstream.
Photo: Sayan Chuenudomsavad

Every morning, fishermen from the Siphandone area bring their fish to be sold to middlemen in Nakasang village, which hosts a major local fish market. Large quantities of various fish species are collected and then transported to Pakse and other locations, thereby forming a substantial local economic system that sustains communities in the region.
Photo: Sayan Chuenudomsavad
Fish trading at Nakasang involves both small- and large-scale transactions, with local traders and buyers coming from different places. The market is bustling every morning.
Photo: Sayan Chuenudomsavad
November is when the Mekong River begins to recede and the dry season starts, so it is not a particularly good time for fishing. However, at Nakasang, there are still large fish and relatively high catches compared to other areas.
Photo: Sayan Chuenudomsavad
Don Sahong, the second dam on the Lower Mekong mainstream, was constructed in 2016 and became operational in 2019. Its infrastructure and capacity expansion plan, which increased capacity from 260 MW to 325 MW, was completed in 2024. The dam is among the most criticised projects on the Mekong River, as it has a significant impact on fishery resources by blocking fish migrations in Hou Sahong, a channel between the islands of Don Sadam and Don Sahong and the only channel that fish can pass through to migrate past Khone Falls in Siphandone during the dry season, just upstream of the Lao PDR–Cambodia border.
Photo: Sayan Chuenudomsavad
Villagers herd their cattle onto boats to cross the braided channels and bring them back in the evening after grazing on islands in the middle of the Mekong River. Beyond fisheries, local people along the Mekong also depend on its ecosystems, using seasonally exposed islands and sandbars as grazing land for their livestock. They said that since the construction of the Don Sahong dam, grazing land for their cattle has decreased due to large-scale construction and changes in river flow patterns. During certain times of the year when food is scarce, they must transport their cattle across the river by boat to reach available grazing areas on the islands.
Photo: Sayan Chuenudomsavad
Noo, a fisherman in Muang Khong, prepares his large-mesh nets to catch the Jullien’s golden carp, a critically endangered Southeast Asian freshwater fish. Fishermen here said in late November, when Bangkok Tribune visited them, that the fish’s migration through Muang Khong was significantly delayed because water levels had not receded and conditions remained muddy. A year earlier, at the same time, water levels had receded and the water had cleared. Mr. Noo caught hundreds of kilograms of the fish on his own within a few days, as the fish usually surfaced in Muang Khong. Last November, however, there was no sign of their arrival.
Photo: Sayan Chuenudomsavad
The project’s Environmental Impact Assessment (EIA) noted that Phou Ngoy is planned to be located about 18 km downstream of Pakse Town in Champasak Province, Lao PDR. Local sources told Bangkok Tribune that the latest proposed site is near Morphou village (Ban), which has reportedly been redesignated for the project. The dam site has reportedly been relocated from Phou Lat Suea and Phou Ngoy to Phou Malong (shown in the photo). Ban Morphou is a long-established village and is one of seven villages slated for relocation.
Photo: Sayan Chuenudomsavad
Farmers in Ban Morphou, who live along the Mekong River, cultivate their crops in accordance with the seasonal ebb and flow of the river. Many villagers said they had learned that the construction of a dam near Veun village, located about 4–5 km upstream, opposite Phou Ngoy, but they do not know why the dam embankment has reportedly been shifted to their village, Ban Morphou.
Photo: Sayan Chuenudomsavad
Life continues in Ban Morphou. Children go to school and play as usual. Ban Morphou is a large, long-established village where livelihoods are passed down from generation to generation.
Photo: Sayan Chuenudomsavad

Near the dam site, many tree species on the islands and sandbanks of the Mekong River are adapted to withstand strong currents because they are submerged during high water. These trees can withstand flooding for extended periods, but changes in water levels due to dam construction and operation, as well as climate change, have led to significant loss of trees and ecosystem integrity. Photo: Sayan Chuenudomsavad

Phou Ngoy Mountain, from which the name “Phou Ngoy Dam” is derived, is located in Ban Veun, around 4–5 km upstream of Ban Morphou.
Photo: Sayan Chuenudomsavad

A Jullien’s golden carp (Probarbus jullieni), weighing approximately 15 kg, was caught in the Mekong River near Pakse and sold for around 2–2.5 million kip (US $93–115) in late November. Fishers can still catch specimens of this size in southern Laos, but their abundance has declined due to physical barriers created by dams across the river. Inland capture fisheries support the local economy of the Mekong region and serve as a primary occupation for riverine residents along the Mekong.
Photo: Sayan Chuenudomsavad

Upstream, the mouth of the Mun River in Khong Chiam District, Thailand, can be seen from a vast sandy bar at Sing Sam Phan village in Laos. The dam’s pondage area is reported to extend to this area and create backwater effects that could complicate floodwater drainage in the Mun River system. The Pak Mun Dam is also reported to be affected by hydrological changes associated with Phou Ngoy.
Photo: Sayan Chuenudomsavad
Mae Sompong Viengchan (Mother Sompong) was once a villager who became a community leader in the Pak Mun protests, where she led protests with hundreds of villagers in the 1990s against the 136 MW Pak Mun hydropower dam. In the 2020s, she continues to oppose another Mekong dam project, Phou Ngoy.
Photo: Sayan Chuenudomsavad
The 136-MW Pak Mun dam stands on the Mun River, around five km from its mouth in Khong Chiam District, Ubon Ratchathani Province. The dam triggered a fierce conflict over water resource development and conservation as it jeopardised the Mun River’s ecosystems and the livelihoods of local communities once dependent on it. Its critical component — the fish ladder or fish passage facilities (Bandai Pla Jone in Thai) — is no less controversial. The fish ladder was allegedly built without sufficient studies of the Mun River’s ecosystems and fish cycles, resulting in the ladder largely failing to restore the deteriorating ecosystem. The dam is also now affected by another downstream project, Phou Ngoy.
Photo: Sayan Chuenudomsavad
Kaeng Tana Rapids are among the iconic rapids in the area, left after blasting to make way for the Pak Mun dam. They are now a protected tourist attraction in the province and the wider region, located within Kaeng Tana National Park. However, the project’s Environmental Impact Assessment (EIA) noted that if the Phou Ngoy dam is built, Kaeng Tana would be submerged by backwater effects.
Photo: Sayan Chuenudomsavad
Wisut Kodkaew, a 53-year-old fisher from Ban Veun Buek (known for its grounds for giant catfish), is from the first village in Thailand to be affected by backwater effects from Phou Ngoy. Ban Veun Buek has approximately 140 households, and more than 50 of them primarily rely on fishing for their livelihoods. Because the surrounding area lies within a national park, farming is not permitted. As a result, villagers are largely dependent on fishing. For about four months each year, fishing is not possible, so they take on temporary work to make a living and save money.
Photo: Sayan Chuenudomsavad

At Ban Veun Buek, children still enjoy swimming in the Mekong River without knowing that their village may one day be submerged by a dam far downstream.
Photo: Sayan Chuenudomsavad

This photo essay is part of the SPECIAL REPORT SERIES: Environmental Challenges under the Great Power’s Influences.