Sand Mining Threatens Collapse of Southeast Asia’s largest Freshwater Lake
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Published: 2025-11-11 10:23:00
!Sand mining on the Mekong river at Phnom Penh, Cambodia. Credit: Andy ball / University of Southampton
Sand mining on the mekong River at Phnom Penh, Cambodia.Credit: Andy Ball / University of Southampton
Intense sand mining is putting the largest freshwater lake in Southeast Asia at risk of collapse with catastrophic consequences, a new study has found.
The huge Tonlé Sap Lake in Cambodia,a UNESCO Biosphere Reserve, is one of the world’s most ecologically diverse lake ecosystems, home to endangered amphibians, reptiles, mammals and birds, with a diverse array of 885 species. It provides livelihoods for almost two million fishers,and its fish feed millions more.
But its future is in danger as the intensity of the unique ‘reverse flow’ that feeds water into the lake has been declining year-on-year.
Scientists have now conclusively determined the cause of this decline to be sand mining in the Mekong River in Cambodia and Vietnam.
Sand mining is the practice of extracting sand from the riverbed, with the majority used in the construction industry.
Rates of sand mining in the Mekong have rapidly increased, with over 100 million tonnes of sand now being removed every year.
Riverbank collapses triggered by lowered riverbed levels on the Mekong River in Cambodia. Credit: Andy Ball / University of Southampton
Steve Darby, professor of Physical Geography at the University of Southampton and co-author of the new research, said: “There has been lots of speculation as to why the intensity of the reverse flow has been declining, with climate change and damming on the Mekong upstream in China and Laos previously being identified as possible causes.
“Our work demonstrates that, while climate change and damming are minor contributory factors, by far the dominant driver has been riverbed incision caused by largely rampant sand mining on the Mekong.”
The reverse flow system
Tonlé Sap Lake is sustained by an unusual reverse flow system. The Tonlé Sap River normally drains the lake,flowing downstream to Phnom Penh,where it joins the Mekong river.
Sand Mining Threatens Food Security and Livelihoods Around Cambodia’s Tonlé sap Lake
A growing body of research highlights the devastating impact of sand mining on the environment and communities surrounding Cambodia’s Tonlé Sap Lake, a critical resource for the region. Scientists are investigating the ecological consequences, including declining fish populations, threatening food security for millions and driving fishing communities into debt.
The Importance of Tonlé Sap Lake
Tonlé Sap Lake is Southeast asia’s largest freshwater lake and a vital ecosystem.It’s estimated to provide around 60% of Cambodia’s protein and feed approximately six million people. https://www.southampton.ac.uk/news/2024/01/tonle-sap-lake-cambodia-sand-mining-fish-stocks The lake’s unique hydrological cycle, reversing direction during the monsoon season, supports an incredibly diverse and productive fishery. However, this delicate balance is increasingly threatened by a combination of factors, with sand mining emerging as a significant driver of ecological damage.
The Impact of Sand Mining
Sand mining, often illegal and unregulated, involves dredging sand from the lakebed and river systems that feed into Tonlé Sap. This practice has far-reaching consequences:
* Disrupted Lake Levels: Excessive sand extraction alters the natural flow of water, impacting the lake’s ability to regulate water levels during the wet and dry seasons. https://www.southampton.ac.uk/news/2024/01/tonle-sap-lake-cambodia-sand-mining-fish-stocks
* Habitat Destruction: Dredging destroys critical fish spawning grounds and breeding habitats, reducing fish populations.
* Water Quality Degradation: Sand mining stirs up sediment, increasing turbidity and reducing light penetration, harming aquatic plants and impacting water quality.
* Increased Salinity: In coastal areas, sand mining can lead to saltwater intrusion, further damaging freshwater ecosystems.
Pesticide sheen on the surface of Tonlé Sap Lake. Credit: Edward Bellomy
Several research projects are underway to better understand and address the crisis.
* Hidden Sands: Led by Professor Julian Leyland at the University of Southampton,the Hidden Sands project investigates the environmental and social impacts of sand mining in Cambodia. https://www.southampton.ac.uk/news/2024/01/tonle-sap-lake-cambodia-sand-mining-fish-stocks The team is also collaborating with agencies in Vietnam to develop a more risk-based approach to sand mining governance.
* Ecological Impact Assessment: A new project involving Professor Craig Hutton (Sustainability Science) and Professor Paul Kemp (Ecological Engineering) from the University of Southampton is focused on fully understanding the ecological impact on Tonlé Sap lake, with a particular emphasis on fish populations.
Voices from the fishing Communities
Recent interviews conducted by Professors Hutton and Kemp with fishing communities reveal a dire situation. Fisherfolk report significant declines in both aquaculture and wild fish catches, with some experiencing up to 80% mortality in farmed fish. https://www.southampton.ac.uk/news/2024/01/tonle-sap-lake-cambodia-sand-mining-fish-stocks This decline is leading to mounting household debt and a loss of livelihoods. As one interviewee poignantly stated, “We just want another life for our children now. Anything but fishing.”
Compounding Factors
The decline in fish production isn’t solely attributable to sand mining.Professor Hutton emphasizes that deforestation, illegal fishing practices, and