Case study on sediment in the Mekong River Basin: Current state and future trends

The report analyzes the critical role of sediment in the Mekong River Basin and the threats posed by human activity and climate change. It finds that hydropower dams and riverbed mining are drastically reducing sediment loads, which threatens the productivity of the Mekong Delta and Tonle Sap, impacts fisheries and agriculture, and increases coastal erosion. The authors recommend enhanced regional monitoring, better data sharing between China and Lower Mekong countries, and the integration of sediment management into the entire hydropower lifecycle.

• Hydropower development in the Upper Mekong/Lancang River and its tributaries, alongside riverbed mining in the Mekong Delta, has caused sediment load reductions greater than previously estimated. Monitoring data from the Mekong River Commission (MRC) shows average suspended loads decreased from 60 to 10 Mt at Chiang Saen (83% reduction), 120 to 60 million tonnes/year at Pakse (50% reduction), and 160 to 90 million tonnes per year at Kratie (43% reduction) between the periods before 2003 and after 2009.
• Under a 'full hydropower development scenario' where all proposed dams in the Lower Mekong Basin (LMB) are built, approximately 96% of the sediment load would be trapped, leaving only 4% to reach the delta region.
• The reduction of sediment and nutrients due to mainstream dams is projected to decrease the primary productivity of aquatic systems in the delta region by 12-27%. Specifically, at Kratie, the total transport of phosphorus is projected to reduce by 47-53% and nitrogen by 57-62% under full hydropower development.
• Sediment loss is expected to significantly impact agriculture and fisheries. In a 10-year impact scenario, rice production could decline by approximately 552,500 tonnes in Viet Nam and 203,300 tonnes in Cambodia. Certain fish species, including Lithophils, Psammophils, and Pelagophils, are specifically dependent on bedload and wash load for reproduction and may fail to adjust to changes in spawning grounds.
• Riverbed mining for construction and landfill, particularly for roads in the delta and exports to Singapore and China, is a major source of sediment loss. In 2011, an estimated 55.2 million tonnes of sediment were extracted from the mainstream in Lao PDR, Thailand, Cambodia, and Viet Nam, with Cambodia accounting for 60% of the extraction.
• Climate change is expected to increase uncertainty and variability in sediment transport. Projections suggest annual sediment yield could range from a 27% decrease to a 160% increase. Additionally, a shift in tropical cyclone climatology away from the Indochina peninsula is projected to further reduce suspended sediment delivery to the Mekong Delta.
• The decline in sediment delivery is causing morphological changes, including riverbed scouring and bank erosion. In the Mekong Delta, this contributes to the slow sinking of the delta and increased vulnerability to erosion at river mouths, with some estimates suggesting an increase of 4-12 metres/year in erosion at river mouths due to mainstream dams.
• There is a critical lack of consensus on sediment baselines due to limited spatial and temporal resolution of monitoring data for suspended and bed loads in the Lancang and Mekong rivers and their tributaries.

APA

Piman, T., & Shrestha, M. (2017). Case study on sediment in the Mekong River Basin: Current state and future trends. Stockholm Environment Institute. https://www.sei.org/mediamanager/documents/Publications/Bangkok/SEI_2017_Report_Mekong_sediment_LoRes.pdf

Chicago

Piman, Thanapon, and Manish Shrestha. Case study on sediment in the Mekong River Basin: Current state and future trends. Stockholm Environment Institute, 2017. https://www.sei.org/mediamanager/documents/Publications/Bangkok/SEI_2017_Report_Mekong_sediment_LoRes.pdf.

Wikipedia

{{cite report |last1=Piman |first1=Thanapon |last2=Shrestha |first2=Manish |title=Case study on sediment in the Mekong River Basin: Current state and future trends |publisher=Stockholm Environment Institute |date=November 2017 |url=https://www.sei.org/mediamanager/documents/Publications/Bangkok/SEI_2017_Report_Mekong_sediment_LoRes.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{piman2017case, author = {Piman, Thanapon and Shrestha, Manish}, title = {{Case study on sediment in the Mekong River Basin: Current state and future trends}}, institution = {Stockholm Environment Institute}, year = {2017}, month = nov, url = {https://www.sei.org/mediamanager/documents/Publications/Bangkok/SEI_2017_Report_Mekong_sediment_LoRes.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }