Mekong River Dams: Thailand’s Complex Regional Challenge

There are now more than 1,000 dams across the Mekong basin, and Thailand sits downstream of most of them (Earth System Science Data (Copernicus/ESSD) — peer-reviewed journal). Every one of those structures changes how much water, sediment, and fish reach Thai communities along the river — and Thailand itself buys a large share of the electricity those dams produce.

This is not a simple “upstream villain, downstream victim” story. Thailand’s grid depends on Lao hydropower even as Mekong dams squeeze the fisheries and farmland that river communities in the northeast rely on. Both things are true at once, and the tension between them shapes Thai energy policy right now.

TL;DR: The Mekong basin has 1,055 dams, with China’s Lancang cascade alone generating 21,250 MW (Earth System Science Data (Copernicus/ESSD) — peer-reviewed journal). Thailand imports roughly 15% of its electricity from Laos (Earth Journalism Network — Locked In: Why Thailand Buys Electricity from Laos), even as upstream dams have cut sediment reaching Thailand by up to 84% (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)) and Lower Mekong fish catches by nearly a third since 2010 (MRC — Assessment of Fisheries Yield in the Lower Mekong River Basin 2020 (published 2023)).

How Many Dams Are on the Mekong River Today?

A 2024 basin-wide database counted 1,055 dams on the Mekong system — 661 already operating, 54 under construction, and 331 planned (Earth System Science Data (Copernicus/ESSD) — peer-reviewed journal). That’s more than double the number tracked in earlier surveys, largely because tributary dams were undercounted for years.

China operates 11 dams on its stretch of the upper Mekong, known there as the Lancang, with a combined capacity of 21,250 MW (Earth System Science Data (Copernicus/ESSD) — peer-reviewed journal). A twelfth mainstream dam, Tuoba, came online in early 2024 (Mekong River Commission (MRC)). Downstream, Laos runs 98 hydropower projects — about 64% of all installed capacity in the Lower Mekong Basin (Mekong River Commission (MRC)).

The two countries build differently: China concentrates capacity in a handful of very large mainstream dams, while Laos spreads it across dozens of smaller tributary and mainstream projects. Both approaches change how much water Thailand sees downstream, just on different timescales — China’s dams can hold back or release large single pulses, while Laos’s cluster produces smaller, more frequent fluctuations.

Altogether, the Lower Mekong Basin has 88 operating hydropower projects generating 13,257 MW, with another 20 under construction (Mekong River Commission (MRC)). For Thai communities along the river in Chiang Rai, Nong Khai, and further downstream, that means the river’s behavior is now shaped almost as much by dam operators as by rainfall.

How Do Upstream Dams Change Water Flow Reaching Thailand?

Upstream dam restrictions held back roughly 8.2 billion cubic metres of water in a single month, pushing Mekong river levels about 10% lower than normal by August 2024 (Stimson Center — Mekong Dam Monitor 2024 Progress Report). That single number explains a lot of what Thai river communities report anecdotally: water levels that no longer track the seasons the way they used to.

The swings can run the other direction too. In February 2024, China’s Tuoba Dam restricted 1.215 billion cubic metres of flow while filling its reservoir (Stimson Center — Mekong Dam Monitor 2024 Progress Report). Then, over just 11 days in August 2024, flow at Chiang Saen on the Thai-Lao border jumped from 5,200 to 8,900 cubic metres per second (Mekong River Commission (MRC) — Official Media Release) — a swing large enough that Nong Khai’s water level hit 12.69 metres, above the 12.2-metre flood threshold, on August 29, 2024 (Mekong River Commission (MRC) — Official Media Release).

What this means: Isn’t the Mekong supposed to follow a predictable wet-dry cycle? It used to. Now a village downstream can see a flood spike triggered by a dam release hundreds of kilometers upstream, with little warning tied to local rainfall. Farmers who plan planting around the traditional flood pulse are increasingly planning around dam operator schedules instead.

The 2024 dry season was itself unusual: the lowest hydropower releases from China in three years, combined with temperatures 5-7°C above normal across northeast Thailand (Stimson Center — Mekong Dam Monitor 2024 Progress Report). Reduced upstream releases compound naturally low rainfall years, making droughts in Isaan sharper than they would be from weather alone.

What’s Happening to Mekong Sediment and Fisheries?

Sediment reaching Chiang Saen, Thailand, has dropped 84% compared to historical levels — a 1965-1991 baseline versus 2010-2019 measurements (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)). Further downstream, monitoring stations between Luang Prabang and Nong Khai show sediment reductions of 53-62% over the same period (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)). Dams trap the sediment that used to rebuild Thai riverbanks and farmland every year.

Less sediment means fewer nutrients feeding the food chain that Lower Mekong fisheries depend on. Those fisheries produce 2.3 million tonnes of fish per year worth roughly $11 billion, supporting an estimated 70 million people basin-wide (Mekong River Commission (MRC) — Fisheries page). By 2020, that catch had already fallen to between 1.51 and 1.71 million tonnes — down from 2.3 million tonnes just a decade earlier (MRC — Assessment of Fisheries Yield in the Lower Mekong River Basin 2020 (published 2023)). Near Xayaburi specifically, local catch reportedly dropped as much as 70% after the dam opened in 2019 (The Diplomat — Where Have All the Mekong River’s Fish Gone? (Feb 2024)).

Researchers modeling full basin dam development project total fish catch could fall a further 40-80% by 2040 (International Rivers — Tragic Trade-Offs: The MRC Council Study and the Impacts of Hydropower Development).

Practical implication: For riverside communities in Nong Khai, Nakhon Phanom, and Ubon Ratchathani, fish catch decline isn’t an abstract statistic — it’s a shrinking income source that pushes households toward aquaculture, migration for work, or dependence on remittances instead of the river itself.

Why Does Thailand Import So Much Hydropower From Laos?

Laos supplied about 15% of Thailand’s electricity demand in 2024, delivered almost entirely as hydroelectric power flowing south from dams on the same river system that’s straining Thai fisheries (Earth Journalism Network — Locked In: Why Thailand Buys Electricity from Laos). That’s the uncomfortable part of this story: Thailand isn’t only a downstream victim of upstream dam-building — it’s also a major financier and customer.

EGAT, Thailand’s state utility, bought around 4,000 MW of Lao hydropower in 2019 alone — about 10% of the country’s total installed generating capacity (Southeast Asia Globe — Locked in: Why Thailand buys electricity from Laos). Under a long-running bilateral agreement, Thailand committed to purchasing up to 10,500 MW from Laos over time (Radio Free Asia). Xayaburi, the dam most linked to fisheries decline near its site, sends 95% of its output straight to EGAT (EarthRights International).

More is coming. EGAT signed a 29-year power purchase agreement for the 912 MW Pak Beng dam in September 2023, worth $2.37 billion, with construction beginning in October 2025 (Bangkok Tribune — Power purchase agreement for Pak Beng dam signed: EGAT). Contracts for the 1,460 MW Luang Prabang dam and the 770 MW Pak Lay dam were signed in November 2022 and March 2023 (International Rivers — Sites of Struggle and Sacrifice: Mapping Destructive Dam Projects along the Mekong River).

According to Earth Journalism Network reporting, Lao hydropower imports reached 15.7% of Thai electricity demand — 38,146 GWh — in 2025 (Earth Journalism Network — Locked In: Why Thailand Buys Electricity from Laos). That’s a real and growing share of Thailand’s grid, sourced from a river system Thailand’s own researchers acknowledge is under severe ecological strain.

Is Thailand Pushing Back on New Mekong Dams?

Not always quietly. Thailand postponed its power purchase agreement for the 684 MW Sanakham dam — sited just 2 km from the Thai border — pending better transboundary impact data (Bangkok Tribune — Thailand openly calls for transboundary impact assessments from Laos’ Sanakham dam). That single decision shows Thailand isn’t simply rubber-stamping every new project EGAT could buy from.

Comparing the five major dams in Thailand’s current pipeline shows a pattern: three of five (Xayaburi, Luang Prabang, Pak Beng) moved from contract to construction within roughly a year of signing, while Sanakham has stalled for years over unresolved impact assessment. Contract speed appears to track how contested the transboundary data is, not just project size.

The Mekong River Commission, the intergovernmental body Thailand belongs to alongside Laos, Cambodia, and Vietnam, continues publishing flow and dam-operation monitoring data that regional governments and independent researchers both cite (Mekong River Commission (MRC) — Official Media Release). China and Myanmar participate as dialogue partners rather than full members, which limits how much leverage the Commission has over the two upstream dams contributing the most to flow disruption.

How this compares: Vietnam, at the very bottom of the basin, has pushed the hardest publicly for upstream data-sharing, since it absorbs the compounded effects of every dam upstream. Thailand’s position is more mixed — vocal on specific high-risk projects like Sanakham, but a steady buyer of power from dams with documented downstream harm elsewhere.

What’s Next for Thailand’s Mekong Power and Water Strategy?

Thailand’s Lao hydropower pipeline alone adds more than 5,000 MW of new contracted capacity through the early 2030s (Bangkok Tribune — Power purchase agreement for Pak Beng dam signed: EGAT)(International Rivers — Sites of Struggle and Sacrifice: Mapping Destructive Dam Projects along the Mekong River). Each new dam locks in another multi-decade relationship between Thailand’s grid and a river system already showing measurable strain in sediment, fisheries, and flow stability.

The realistic path forward isn’t Thailand walking away from Lao hydropower — the country’s own tiered electricity pricing and demand growth make that unlikely soon. It’s closer scrutiny per project, the kind Sanakham already got, paired with continued investment in solar energy and other domestic renewable capacity that doesn’t carry the same transboundary cost. The Sanakham delay suggests Thailand has more leverage as a buyer than it typically uses — EGAT’s purchase decisions are one of the few points where Thai policy can directly shape upstream dam economics, since projects without a buyer don’t get built.

Frequently Asked Questions

How many dams are currently on the Mekong River?

The basin has 1,055 dams total: 661 operational, 54 under construction, and 331 planned as of 2024 (Earth System Science Data (Copernicus/ESSD) — peer-reviewed journal). China’s Lancang cascade and Laos’s Lower Mekong Basin projects account for the largest share of installed capacity.

Does Thailand rely on hydropower from the Mekong?

Yes. Laos supplied about 15% of Thailand’s electricity demand in 2024, rising to 15.7% (38,146 GWh) in 2025 (Earth Journalism Network — Locked In: Why Thailand Buys Electricity from Laos). Thailand has committed to purchasing up to 10,500 MW from Laos under long-term agreements (Radio Free Asia).

How much has the Mekong’s sediment declined because of dams?

Sediment reaching Chiang Saen, Thailand, has dropped 84% compared to historical baselines (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)). Stations between Luang Prabang and Nong Khai show reductions of 53-62% over the same period (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)), reducing nutrients that support downstream fisheries and farmland.

Has any Mekong dam project been stopped or delayed because of Thailand?

Thailand postponed its power purchase agreement for the Sanakham dam, located 2 km from the Thai border, over unresolved transboundary impact data (Bangkok Tribune — Thailand openly calls for transboundary impact assessments from Laos’ Sanakham dam). It’s one of the clearer examples of Thailand using its position as a buyer to push back on a specific project.

What is happening to Mekong fisheries that Thai communities depend on?

Lower Mekong Basin fisheries, worth about $11 billion a year and supporting 70 million people, saw catch fall from 2.3 million tonnes in 2010 to as low as 1.51 million tonnes by 2020 (MRC — Assessment of Fisheries Yield in the Lower Mekong River Basin 2020 (published 2023)). Researchers project a further 40-80% decline by 2040 under full dam development (International Rivers — Tragic Trade-Offs: The MRC Council Study and the Impacts of Hydropower Development).

Conclusion

Mekong dams put Thailand in an unusual position: a country simultaneously buying power from a river system and absorbing the ecological cost of that same system’s development. Sediment reaching Thai border stations has fallen as much as 84% (ScienceDirect — Sediment load crisis in the Mekong River Basin (peer-reviewed)), Lower Mekong fish catches are down nearly a third since 2010 (MRC — Assessment of Fisheries Yield in the Lower Mekong River Basin 2020 (published 2023)), and river levels now swing on dam-operator schedules as much as rainfall (Stimson Center — Mekong Dam Monitor 2024 Progress Report).

At the same time, roughly 15% of Thailand’s electricity now comes from Lao hydropower (Earth Journalism Network — Locked In: Why Thailand Buys Electricity from Laos), with thousands more megawatts under contract through the 2030s (Bangkok Tribune — Power purchase agreement for Pak Beng dam signed: EGAT)(International Rivers — Sites of Struggle and Sacrifice: Mapping Destructive Dam Projects along the Mekong River). Sanakham shows Thailand can slow a project when the data doesn’t hold up (Bangkok Tribune — Thailand openly calls for transboundary impact assessments from Laos’ Sanakham dam) — the open question is whether that scrutiny becomes standard practice or stays the exception.

• China and Laos together operate over 100 dams generating more than 34,000 MW on the Mekong system
• Thailand imports roughly 15% of its electricity from Lao hydropower, a share still growing
• Sediment and fish catch reaching Thailand have both fallen sharply since major dam construction began
• Thailand has leverage as a buyer, demonstrated once at Sanakham, but rarely uses it