Fourteen dams on the Mekong, and a river 4 meters higher in March at Luang Prabang

How many dams are there on the Mekong River?

On the main stem, the Mekong River Commission counts twelve dams in operation in China, where the river is called the Lancang^[1]. The most recent to come online is Tuoba^[1]. Further down, two dams operate in Laos: Xayaburi since October 2019 and Don Sahong since January 2020^[3]. They are the only main-stem dams downstream of China.

Then come the tributaries. In the lower basin (Laos, Thailand, Cambodia, Vietnam), the MRC lists 88 hydropower plants in operation, 20 under construction and 14 planned, main stem included^[1]. Laos accounts for most of them: over a hundred dams including tributaries^[5].

Mekong dams under construction and planned

In Laos, the Luang Prabang dam (1,460 MW) was 72% complete in July 2026, due to start operating in 2030^[4]. UNESCO is not asking for it to be halted, but is monitoring its effects on the World Heritage town, about 25 kilometers downstream^[14]. The Pak Beng project (912 MW) is in preparatory works, with operation announced for 2033^[5]. Sanakham, near the Thai border, is the only project still under consultation at the MRC^[2].

In July 2026, Laos and Myanmar signed an agreement to study a 2,790 MW dam on the stretch where the river divides them^[7]. Cambodia, for its part, suspended all main-stem dams in 2020 until 2030, freezing the Stung Treng and Sambor projects^[6].

Why build dams on the Mekong?

For Laos, hydropower is first of all an export. The country sells about 80% of its electricity to its neighbors, earning around 2.6 billion dollars, a major resource for one of the poorest countries in the region^[19]. The main-stem dams sell mostly to Thailand^[5].

Demand next door is growing. Vietnam, which imported about 1.5 GW from Laos in 2025, aims for at least 8 GW by 2030. Cambodia imports about 200 MW, produced by Don Sahong, and plans to reach 3 GW by 2030. Singapore has received 200 MW of Lao power since January 2026^[19]. For these countries, it is electricity that burns neither coal nor gas; for people along the river, it comes with the effects described below.

Mekong dams hold back the river's sediment

Dams hold back the silt the river carries. At the head of the delta, the suspended load fell from 100 to 160 million tonnes a year before the dams to about 43 million tonnes, and the Chinese cascade alone traps around 86%^[8]. That silt feeds the rice fields and offsets the delta's natural sinking.

Did China's dams worsen the Mekong droughts?

From 2019 to 2021, the Mekong fell to its lowest flows in more than sixty years^[9]. In 2020, a US-funded study by the firm Eyes on Earth concluded that Chinese dams had held back water during the drought; the MRC questioned its method^[10]. In its 2022 report, the MRC blamed the crisis mainly on low rainfall, while acknowledging that upstream dams change the river's regime: more water in the dry season, less in the rainy season^[9].

Since November 2020, China has shared water levels from two of its stations with the MRC all year round, not just during the monsoon^[13].

Have dams changed the Mekong's water level?

Yes, and the MRC's own readings show by how much. Its stations have recorded the river's level for decades: we compared the monthly averages of three of them before and after the big dams^[20]. These are gauge heights at each station, so they compare from one period to another, not from one station to another.

The clearest change is at Luang Prabang. From 2010 to 2018, the river there dropped to around 4.5 m in March; from 2020 to 2025 it stays near 8.8 m, 4.4 m higher, while the August flood has barely moved, at around 12 m. The gap between low and high water has shrunk from 7.4 m to 3.3 m^[20]. The Xayaburi reservoir, filled in 2019 downstream, now backs up to the town: as early as February 2020, the MRC noted that the level at Luang Prabang stayed close to its maximum because of the dam^[21].

Upstream, at Chiang Saen, the Thai station closest to China, the Chinese cascade is at work. Its two largest reservoirs, Xiaowan and Nuozhadu, came into service in 2010 and 2014; they store monsoon water and release it in the dry season, according to Chinese state television^[22]. At Chiang Saen, the river in March is 1.1 m higher than in 1990-2009, and the August flood 1.7 m lower: the yearly range has been halved, from 4.7 m to 2.3 m^[20]. This is the “more water in the dry season, less in the wet season” the MRC describes^[9].

In Cambodia, the effect fades. At Kratie, the September flood peaks at 17.3 m on average in 2020-2025, against 19.2 m in 1990-2009, and the March low is slightly higher, 7.2 m against 6.4 m: the yearly range is still more than 10 m^[20]. Over these six years, which include the 2020 and 2021 droughts, the share of the dams cannot be separated from that of the missing rain^[9].

What dams and sand mining change for the Tonle Sap

The Tonle Sap fills when the flooding Mekong pushes up the river toward the lake. In 2020 and 2021, that volume reached only 58% and then 51% of the average^[9]. A study published in November 2025 blames most of the decline not on dams alone, but on the lowering of the riverbed, dug out by sand mining and starved of the sediment held back upstream: the volume flowing back to the lake fell by 40 to 50% between 1998 and 2018^[11].

Dams and fishing on the Mekong

Dams block the routes of migratory fish. According to a study quoted by the WWF, dams in the basin could cut capture fisheries by 23 to 39%; with the eleven dams planned on the lower Mekong main stem, losses would reach about 44% in Cambodia and 42% in Vietnam^[12]. These are projections, which depend on the dams actually built.

What the dams change for a trip on the Mekong

The slow boat from Huay Xai to Luang Prabang travels the stretch where the Pak Beng and Luang Prabang dams are planned. The Pak Beng project includes a ship lock and a fish passage^[5]. At Luang Prabang, the dam is being built about 25 kilometers (15 miles) north of the town: passenger boats and cargo vessels of up to 500 tonnes will pass its lock in about forty minutes, and the reservoir is to stay below 310 meters above sea level to spare the World Heritage town^[4].

Farther south, Don Sahong blocks one of the river's channels in the 4,000 Islands, in Laos^[17]. Cambodia has no dam on the main stem: from Stung Treng to the delta, the river stays free-flowing until at least 2030^[6].

Who decides on Mekong dams?

Cambodia, Laos, Thailand and Vietnam created the Mekong River Commission in 1995. Any project on the lower Mekong main stem goes through a prior consultation among these four countries. It is not meant to approve or reject the project, but to seek agreement on its conditions^[15]. Five consultations have been concluded, for Xayaburi, Don Sahong, Pak Beng, Pak Lay and Luang Prabang; Sanakham's is ongoing^[2]. China and Myanmar are not members.

Pierre-Marie Coupry

Editor-in-chief of the French travel site Bon Plan Voyage, where he has published since 2012. He checks every practical detail against official sources and proofreads everything before it goes live.

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