Cambodian Journalists Alliance Association

Uncoordinated Dam Operations Threaten Mekong Basin, Residents’ Livelihoods, Report Warns

Throngs of people make their way to Tonle Sap river to buy fresh fish to make Prahok during the fish season, in December 2021. (CamboJA)
Throngs of people make their way to Tonle Sap river to buy fresh fish to make Prahok during the fish season, in December 2021. (CamboJA)

After the Mekong Basin’s hottest and driest dry season on record this year, and amid changing climate conditions, Cambodia’s Tonle Sap Lake – and other inland fisheries – face growing threats from uncoordinated upstream dam operations.

But a recent report from the Mekong Dam Monitor, an open-source platform tracking dam impacts in near real-time, says strategic management and regional cooperation could protect the lake and benefit flood-dependent communities.

The Tonle Sap, Cambodia’s most productive fishery and vital to its food security, once swelled five fold during the wet season, becoming the world’s largest inland fishery. According to the report, irregular flood pulses may worsen without coordinated efforts to use climate forecasting for optimal dam restrictions that balance fisheries, conservation, and hydropower production.

​​“Sharing dam data with a centralized body like the Mekong River Commission helps it understand how dams affect the Mekong’s ecological benefits, such as fisheries,” the Mekong Dam Monitor (MDM) reported. 

The Mekong River Commission, or the MRC, is the intergovernmental group, made up of Laos, Thailand, Vietnam, and Cambodia, which coordinates sustainable management of the Mekong Basin but has struggled in recent years to address these impacts and even track the number of dams.

Currently, Vietnam, Thailand, and Laos share data for only a limited number of dams on public websites, while Cambodia has yet to establish such a portal.

China, which has built some of the Mekong’s largest hydroelectric projects on its upper reaches, known as the Lancang River, pledged in September 2023 to share dam operations data with the Mekong River Commission by the end of that year. As of late 2024, it has yet to deliver.

​​The MRC estimates there are 61 water diversion projects along the Mekong and its tributaries. 

In large disparity with the commission’s reporting, the Stimson Center – who maintains the Mekong Dam Monitor, has registered a total of 745 dams operating or under construction on the mainstream and tributaries of the Mekong Basin, 40 of which are in Cambodia. 

While monitoring organizations debate data gaps, riparian communities feel the strain.

Phin Mithona, who lives near the Lower Sesan II Hydropower Dam on the Tonle Srepok River, a Mekong tributary in Cambodia, told CamboJA News the dam has brought hardships to her community. When water levels drop, fish vanish; when they rise, floods submerge houses and crops every year.

“The dam blocks the water, and fish can’t migrate upstream. No one wants to fish anymore,” she said. “People are sinking into debt after investing in farming, but getting no returns. Even teens, 17 or 18, are dropping out of school to work on banana plantations.”

The Lower Sesan 2 dam in Stung Treng province was inaugurated in 2017. The dam's construction displaced nearly 5,000 people. CamboJA/ Panha Chhorpoan
The Lower Sesan 2 dam in Stung Treng province was inaugurated in 2017. (CamboJA)

Despite testimony from riparian communities, Khim Finan, spokesperson for the Ministry of Agriculture, Forestry, and Fisheries, insisted Cambodia’s fisheries productivity has not declined.

According to the ministry’s forecasts, annual fish catches increased by 5% in 2023 and are expected to rise by 10% by year’s end.

“The ministry’s working group is also engaged with fishermen in local communities, who reported similar observations,” he added.

The Fisheries Administration previously reported 426,750 metric tons of freshwater fish caught in Cambodia in 2023. While this surpassed yields from 2019, 2021, and 2022, the 2019-2021 stretch marked the driest years on record for the Tonle Sap – until 2024, when a low flood pulse further limited output from Cambodia’s top fishery.

Data on 2024 fish yields has yet to be released.

Alongside concerns about the new reality of scheduled dam restrictions and their impact on fishing communities, calls for better warning systems have grown.

While the MDM provides early alerts for sudden water releases or restrictions from China’s dams, these alerts mostly benefit communities in Thailand and Laos. 

Cambodian communities, particularly in Ratanakiri and Mondulkiri provinces, have little warning about changes to the Sekong, Sesan, and Srepok Rivers (the 3S Rivers), which are vital to their livelihoods. 

Dams in Laos and Vietnam disrupt these rivers, worsening the Tonle Sap’s shrinking flood cycle. While monitoring of 20 new dams in the 3S Basin has improved understanding of their impacts, experts call for a Vietnam-Cambodia warning system and better tools to monitor water flow to protect communities and ecosystems.

This push for better data sharing between the neighboring countries gained momentum after the groundbreaking of Cambodia’s $1.7 billion Funan Techo Canal project, which will divert water from the Mekong and is expected to have negative environmental consequences, according to experts.

“The MRC, along with national agencies, could organize the data they have to create a more effective warning system, helping people prepare and protect themselves from floods in a timely way,” said Alan Basist, president of Eyes on Earth, during a Dec. 17 webinar on the MRC report.

Srey Lakh Mech, Technical Climate Resilience Coordinator for Oxfam Cambodia’s Mekong Regional Water Governance Program, backed Basist’s call for a regional system to track seasonal inundations and account for changing climate conditions.

Srey also stressed that communication networks must reach indigenous populations in northern Cambodia, many of whom have limited literacy.

At the moment, Cambodia’s system for receiving notifications from Laos and Vietnam when hydroelectric dams are opened is limited, relying on Telegram channels in areas with poor cellular service and emergency alert systems, according to Soth Kimkolmony, spokesperson for the National Committee for Disaster Management.

Kimkolmony also noted there have been no serious incidents caused by dam operations since 2018. That year, thousands of northern Cambodian residents were displaced after a major hydropower dam collapsed in Laos, highlighting the potential for disasters beyond the dams’ impacts on waterway health and community livelihoods.

A spokesperson for the Ministry of Water Resources and Meteorology and Heng Kunleang, director-general of the General Department of Energy, did not respond to questions about collaboration with the MRC and neighboring countries on sharing dam restriction data.

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