Chinese-Funded Dams in Laos Are Changing Water Levels Downstream in Cambodia—and ASEAN Isn't Talking About It
Eleven hydropower dams on the Mekong mainstream are altering river flows that millions depend on. Cambodia's fisheries are collapsing, rice fields are drying up, and regional diplomacy stays silent.
The Mekong River doesn't follow election cycles or diplomatic calendars. It follows gravity and upstream infrastructure decisions—and right now, those decisions are being made in Laos with Chinese financing, while the consequences show up hundreds of kilometers south in Cambodia's rice fields and fishing communities.
By Carmen Villanueva
Eleven dams now operate on the Mekong mainstream in Laos, most built with loans and engineering from Chinese state firms including Sinohydro and China Southern Power Grid. The Xayaburi Dam, operational since 2019, cost $3.8 billion. The Don Sahong Dam, completed in 2020, sits directly on a critical fish migration route. Together with nine others, they generate power primarily for export to Thailand and Vietnam under long-term purchase agreements.
Downstream, Cambodia's Tonle Sap Lake—Southeast Asia's largest freshwater lake and a protein source for 1.2 million people—is experiencing unprecedented low-water events during what should be high-flow seasons. Fisheries data from the Mekong River Commission show fish catches in Cambodia dropped 40 percent between 2010 and 2022. The 2023 dry season saw water levels at the Tonle Sap fall to near-record lows in March, when seasonal flooding typically begins.
Rice farmers in Kampong Cham and Prey Veng provinces report irrigation canals running dry weeks earlier than historical patterns. A 2024 study from Cambodia's Ministry of Water Resources attributed irregular flows to "upstream water management," diplomatic language for dam operations in Laos and China's Yunnan Province, where six additional dams regulate the upper Mekong.
ASEAN has held four summits since 2022. Mekong water management appeared on none of the official agendas. The Mekong River Commission—which includes Cambodia, Laos, Thailand, and Vietnam but not China—issued technical reports documenting flow alterations but has no enforcement mechanism. Laos, which earns $2.4 billion annually from hydropower exports, has not modified dam release schedules in response to Cambodian complaints.
Cambodia's government, which received $4.2 billion in Chinese infrastructure loans between 2016 and 2023, has not escalated the issue bilaterally with Beijing or Vientiane. Prime Minister Hun Manet visited Laos in February 2025 for trade discussions; water security was not on the published agenda.
The political silence doesn't change the hydrological reality. The Mekong mainstream now operates as a regulated system, with discharge controlled by turbine schedules set in Vientiane and Kunming, not by monsoon patterns. Fishing communities at Tonle Sap and rice farmers along the Cambodian floodplain are adapting to a river whose behavior no longer matches the climate they know. ASEAN's mutual non-interference principle, designed to prevent political disputes, now also prevents member states from discussing the infrastructure that controls the region's largest shared water system.
