Mekong Research Articles

In and Out of Plain Sight: Interrogating Power in the Mekong Riverscape

The Mekong River has long conjured images of power: cascading waterfalls, impenetrable rapids, and pervading spirits. But power is always malleable and shifting, a fact not lost on the human and nonhuman agents who live with the river and its tributaries. Rises and drops in water levels that once fluctuated in accordance with the seasons have now become beholden to the electricity needs of urban centres like Bangkok: a shift from watershed to powershed. The emerging techno-political realities of the Mekong give rise to new ways of seeing and managing the river, often at the cost of long- held local understandings and configurations of power. The recent boom in hydropower development in the Mekong Basin has been alarming, and rapid change has had adverse impacts on the riparian peoples who depend on the river for their livelihoods. Despite the countless negative social and ecological impacts from dams, especially on the mainstream Mekong, hydropower investments and construction continue. New hegemonic scales and configurations of power have emerged in the Mekong Basin, but older local ones have not simply disappeared. Rather, power shifts in and out of plain sight. In this special issue, we trace the flows, scales, and reconfigurations of power from the management of Mekong water flows and the financing of hydropower projects through to the ruptures and (un) intended consequences of hydropower dam projects on living human and nonhuman worlds in the region. Through a multi-scaled and multi-sited lens, we bring to light emerging worlds in the Mekong Basin.

The Don Sahong Dam in Laos: Political Ecology, Infrastructure, and the Changing Spatialities of Impacts on Fish and People

The Don Sahong Hydropower Project (DSHPP), located in the Khone Falls area of Khong District, Champasak Province, southern Laos, near the border with Cambodia, has been amongst the most controversial hydropower dams in the Mekong River Basin. Despite considerable regional and international opposition, the dam was finally constructed, becoming commercially operational in 2020. In 2011, I expressed serious concerns about the project's potential impacts on long-distance migratory fish and associated fisheries, especially fish that migrate from Cambodia and Vietnam up the Mekong River to Laos and Thailand. However, my concerns have somewhat changed along with the circumstances, although they continue to focus on dam impacts on migratory fish. I am now particularly concerned about the indirect impacts of the DSHPP on the fishing livelihoods in the Khone Falls area, and the impacts of the dam on fish larvae and fish passing through the dam's turbines when migrating downstream. Using a political ecology approach, this paper considers how infrastructure, in this case a large hydropower dam located on the Mekong River, has altered the spatialities associated with the project in particular ways.

A Politics of Mobility and B/ordering in a Changing Riverscape in Cambodia

Hydropower development taking place on the Mekong River's mainstream and tributaries across the river basin, including Cambodia, is threatening livelihoods and food security by altering critical mobilities associated with the unique ecosystems of the Mekong River. In this paper, we seek to understand how a politics of mobility around hydropower development links both human and nonhuman entities along the Mekong River in Cambodia. We examine how dams transform myriad localized cross-border and riparian political geographies of the physical-human landscape through partial enclosures, up-downstream reorderings and b/orderings of hydrosocial relations. To explain these transformations, we posit that it is necessary to pay attention to the politics of human and nonhuman (such as water, sediment, and fish) mobilities that are shaped by hydropower dams and the new forms of mobilities engendered as a result. We examine how hydropower development renders water, fish, and sediment immobile, or alters their routes and rhythms in ways that optimize the generation of hydropower but which create new concerns around these changing nonhuman mobilities for riparian communities in Cambodia. There is a tension that exists between technical representations and community experiences of these nonhuman mobilities, which raise implications for the exacerbation of vulnerabilities among Cambodian Mekong communities. In this paper, we focus our analysis on selected sites in Cambodia: 1) Stung Treng Province, downstream of Laos' Don Sahong Dam and the Cambodia-Lao border riverscape, and 2) the Tonle Sap Lake (water-based and floodplain areas), to highlight these changing mobilities and the critical processes of b/ordering.

Silences of the Dam: The Intimate Geographies of Ethnic Lao Well-Being on the Sesan River

In the locales where hydropower dams in the Mekong River Basin have been constructed, ethnically and economically marginalized groups who depend on rivers and their tributaries for well-being often bear the greatest burdens: loss of fisheries and river-based livelihoods, riverbank gardens, and sacred sites, to name a few. In December 2018, the controversial Lower Sesan 2 Dam in northeastern Cambodia started operations, exacerbating old challenges and creating new ones for the riverine communities along the Sesan and Srepok Rivers. In this article, I employ a feminist political ecology framework to explore the varying ways that personal and community well-being are impacted in two ethnic Lao locales of Sre Kor (Na Kor in Lao language) commune and Phluk village as a result of the Lower Sesan 2 Dam. While the dam has disrupted flows of water and fish habitats and migrations, rendering new ecological circumstances, I argue that infrastructural violence can variably hide intimate geographies of well-being and un-wellness. Only by interrogating the silences of intimate geographies of the body and home in local villages and communal ethnic spaces will such impacts of violence become visible.

澜沧江流域糯扎渡水库沉积物有机质来源的定量研究

澜沧江流域糯扎渡水库沉积物有机质来源的定量研究

Hydraulic River Models From ICESat‐2 Elevation and Water Surface Slope

AbstractForecasting flood and drought events requires accurate modeling tools. Hydraulic river models are based on estimates of riverbed geometry which are traditionally collected in situ. The novel Ice, Cloud and Land Elevation Satellite 2 [ICESat‐2] lidar altimetry mission with 6 simultaneous high‐resolution laser beams provides the opportunity to define river cross‐section geometries as well as observe water surface elevation [WSE] and water surface slope spatially resolved along the river chainage. This paper describes a method to utilize terrain altimetry and water surface slope estimates to define complete river geometries from ICESat‐2 data products, using the diffusive wave approximation to calculate depth in the submerged section not penetrated by the lidar. Exemplifying the method, cross‐sections are defined for a stretch of the Mekong River. Hydrodynamic model results of the stretch are compared with ICESat‐2 WSE estimates and in situ gauging station time series. Insights in river characteristics from satellite imagery and the ICESat‐2 slope estimates allow for fine‐tuning of the cross‐sections using spatially varying Manning numbers. The final model achieves a root mean square error against the ICESat‐2 WSE of 0.676 m and average Kling‐Gupta Efficiency against gauging station time series of 0.880. The method is limited by the diffusive wave approximation resulting in inaccurate cross‐section estimates in sections with supercritical flow or significant acceleration. Errors can be identified from ICESat‐2 WSE estimates and reduced with additional cross‐sections. Combined with hydrological models, the method will allow for cross‐section definition without in situ data.

Squeezed between Land and Water: Rupture, Frontier-Making, and Resource Conflicts at Cambodia's Lower Sesan 2 Hydropower Dam

Hydropower dam projects in the Lower Mekong Basin are part of long-term and interactive land and water transformations, displacement, and violence. Within these ongoing processes, dams represent intense and adverse episodes of disruption that escalate nature-society transformations. Drawing on research at Cambodia's Lower Sesan 2 Hydropower Dam (LS2 Dam), we examine how such episodes of nature-society rupture catalyze new waves of frontier-making and mobility that further intensify land and resource struggles. 1 In this ethnically diverse landscape, the abrupt hydrological changes caused by the LS2 Dam have escalated land struggles among various ethnic groups, especially migrants intent on claiming land and water resources, and Indigenous/minority groups displaced by the dam. We show how historical relations with land and socio-political marginalization by the state have produced differentiated opportunities, risks, and frictions among the four main ethnic groups present in this landscape: Indigenous Bunong, Lao, Cham, and Khmer. The LS2 Dam case shows how nature-society rupture reifies frontier dynamics by disrupting existing land/water relations, which precipitates in-migration, new resource claims, and associated conflict along ethnic lines.

Plastic pollution affects ecosystem processes including community structure and functional traits in large rivers

Plastics in aquatic ecosystems rapidly undergo biofouling, giving rise to a new ecosystem on their surface, the 'plastisphere.' Few studies quantify the impact of plastics and their associated community on ecosystem traits from biodiversity and functional traits to metabolic function. It has been suspected that impacts on ecosystems may depend on its state but comparative studies of ecosystem responses are rare in the published literature. We quantified algal biomass, bacterial and algal biodiversity (16S and 18S rRNA), and metabolic traits of the community growing on the surface of different plastic polymers incubated within rivers of the Lower Mekong Basin. The rivers selected have different ecological characteristics but are similar regarding their high degree of plastic pollution. We examined the effects of plastics colonized with biofilms on ecosystem production, community dark respiration, and the epiplastic community's capability to influence nitrogen, phosphorus, organic carbon, and oxygen in water. Finally, we present conceptual models to guide our understanding of plastic pollution within freshwaters. Our findings showed limited microalgal biomass and bacterial dominance, with potential pathogens present. The location significantly influenced community composition, highlighting the role of environmental conditions in shaping community development. When assessing the effects on ecosystem productivity, our experiments showed that biofouled plastics led to a significant drop in oxygen concentration within river water, leading to hypoxic/anoxic conditions with subsequent profound impacts on system metabolism and the capability of influencing biogeochemical cycles. Scaling our findings revealed that plastic pollution may exert a more substantial and ecosystem-altering impact than initially assumed, particularly in areas with poorly managed plastic waste. These results highlighted that the plastisphere functions as a habitat for biologically active organisms which play a pivotal role in essential ecosystem processes. This warrants dedicated attention and investigation, particularly in sensitive ecosystems like the Mekong River, which supports a rich biodiversity and the livelihoods of 65 million people.

Triple burden of malnutrition among Vietnamese 0·5-11-year-old children in 2020-2021: results of SEANUTS II Vietnam.

SEANUTS II Vietnam aims to obtain an in-depth understanding of the nutritional status and nutrient intake of children between 0.5-11.9 years old. Cross-sectional survey. A multistage cluster systematic random sampling method was implemented in different regions in Vietnam: North Mountainous, Central Highlands, Red River Delta, North Central and Coastal Area, Southeast and Mekong River Delta. 4001 children between 6 months and 11.9 years of age. Prevalence of stunting and underweight was higher in rural than in urban children, whereas overweight and obese rates were higher in urban areas. 12.0% of the children had anemia and especially children 0.5-1-year-old were affected (38.6%). Low serum retinol was found in 6.2% of children ≥ 4 years old. Prevalence of vitamin D insufficiency was 31.1% while 60.8% had low serum zinc. For nutrient intake, overall, 80.1% of the children did not meet the estimated energy requirements. For calcium intake, ∼60% of the younger children did not meet the RNI while it was 92.6% in children >7 years old. For vitamin D intake, 95.0% of the children did not meet RNI. SEANUTS II Vietnam indicated that overnutrition was more prevalent than undernutrition in urban areas, while undernutrition was found more in rural areas. The high prevalence of low serum zinc, vitamin D insufficiency and the inadequate intakes of calcium and vitamin D are of concern. Nutrition strategies for Vietnamese children should consider three sides of malnutrition and focus on approaches for the prevention malnutrition.

Heavy Metals Content in the Bottom Sediment of the Lower Mekong River (Vietnam)

Heavy Metals Content in the Bottom Sediment of the Lower Mekong River (Vietnam)

Spatial Distribution Characteristics and Source Analysis of Ions in Lancang River and Yangtze River Source Region During Wet Period

Spatial Distribution Characteristics and Source Analysis of Ions in Lancang River and Yangtze River Source Region During Wet Period

An Innovative Correction–Fusion Approach for Multi-Satellite Precipitation Products Conditioned by Gauge Background Fields over the Lancang River Basin

Satellite precipitation products can help improve precipitation estimates where ground-based observations are lacking; however, their relative accuracy and applicability in data-scarce areas remain unclear. Here, we evaluated the accuracy of different satellite precipitation datasets for the Lancang River Basin, Western China, including the Tropical Rainfall Measuring Mission (TRMM) 3B42RT, the Global Precipitation Measurement Integrated Multi-satellitE Retrievals (GPM IMERG), and Fengyun 2G (FY-2G) datasets. The results showed that GPM IMERG and FY-2G are superior to TRMM 3B42RT for meeting local research needs. A subsequent bias correction on these two datasets significantly increased the correlation coefficient and probability of detection of the products and reduced error indices such as the root mean square error and mean absolute error. To further improve data quality, we proposed a novel correction–fusion method based on window sliding data correction and Bayesian data fusion. Specifically, the corrected FY-2G dataset was merged with GPM IMERG Early, Late, and Final Runs. The resulting FY-Early, FY-Late, and FY-Final fusion datasets showed high correlation coefficients, strong detection performances, and few observation errors, thereby effectively extending local precipitation data sources. The results of this study provide a scientific basis for the rational use of satellite precipitation products in data-scarce areas, as well as reliable data support for precipitation forecasting and water resource management in the Lancang River Basin.

Orbital global change drove fluvial aggradation and incision in Tibetan upper Mekong river: Chronological perspectives

The Tibetan Plateau (TP), often known as the “Asia Water Tower”, is the source region of several continental-scale rivers. However, due to the extremely difficult access and harsh living conditions in the interior plateau, fluvial processes in the headwaters of these large rivers and their connections to global climate changes remain unknown. In this study, the luminescence (using both quartz and K-feldspar) and AMS 14C dating techniques were employed to date the four terraces of the Zado Basin in order to elucidate the aggradation and incision history of the initial intermontane basin in the headwater of the Mekong River. One sample from the upper part of T4 terrace (which features a 12 m thick gravel layer, the base of which is unexposed) provides a K-feldspar pIR50IR225 age of 125 ± 10 ka, indicating that the initial deposition of this terrace could predate marine isotope stage (MIS) 5. Considering the margin of error, this age also suggests that the onset of incision on T4 terrace during the climate transition from MIS 6 (glacial) to early MIS 5 (interglacial). This incision likely occurred due to increased meltwater and precipitation, causing the Mekong carving into the bedrock for more than 50 m. Eight luminescence samples are collected from T3 terrace (26.5 m in thickness) with ages ranging from 83 ± 7.6 ka to 22.3 ± 1 0.2 ka, indicating T3 formation/aggradation from late MIS 5 to the Last Glacial Maximum (LGM), possibly owing to reduced precipitation and enhanced sediment supply from intensive glacial activities. At around 22 ka, the Mekong once again shifted towards incision, crafting the T3 terrace, situated roughly 28 m above the current floodplain. This incision event was recorded by two luminescence samples from a sandy lens located at the top of gravel layer of T3, with OSL ages of about 22 ka. Floodplain samples from T2 and T1, dated at 16 ka and 2.8 ka respectively, demonstrate that from the last deglaciation to the Holocene, the Mekong continued its downward incision. This erosion developed two cut and fill terraces at elevations of 22 m and 11 m above the present floodplain, likely due to increased precipitation and enhanced vegetation at that time. Overall, the glacial–interglacial climate changes were the most likely driving force behind fluvial processes in the upper Mekong basin since the Late Pleistocene, with aggradation occurring during the glacial period while incision in deglacial and interglacial periods, suggesting a close link between the fluvial geomorphic evolution and orbital-scale climate changes.

Staged SWAT calibration with bias-corrected precipitation product for enhancing flow data continuity in tributaries of the Mekong River

Accurate and continuous flow data are crucial for effective water management in large river basins worldwide. However, these catchments often face challenges regarding data continuity in the mainstream and their tributaries. This study proposes a methodological framework for enhancing flow data continuity that uses a staged calibration scheme of Soil and Water Assessment Tool (SWAT) modeling with an appropriate satellite precipitation product (SPP) for each watershed. This framework is successfully applied in the Mun-Chi River Basin, the largest tributary of the Lower Mekong River, over a 20-year period at 34 stations. The staged calibration involves partitioning the catchment into smaller sub-catchments, guided by the flow monitoring stations and flow discontinuity structures such as dams. The sequential calibration from upstream to downstream partitions the overall model calibration challenge into smaller problems and contributes to a more efficient and accurate calibration and validation. Alternative SPPs were considered to overcome monitoring gaps. Their bias was corrected using quantile mapping, and their performance was evaluated with flow simulations using the SWAT model. The assessment indicates that the CMORPH-CRT product, with a spatial resolution of 0.25°, demonstrates good suitability for hydrological modeling of the Mun-Chi River Basin. The proposed methodological framework provides a continuous time series of flow discharge at multiple stations within the watershed, offering valuable insights for sustainable water resource management strategies in river systems under changing climate and land use conditions, and supporting future studies on environmental issues.

Carbon Emissions and Vegetation Dynamics: Assessing the Spatiotemporal Environmental Impacts of Hydropower Dams in the Lancang River Basin

Recent decades in the Lancang River Basin have witnessed extensive construction of hydropower dams, profoundly impacting the local environment. Utilizing high-precision satellite data, we conducted a comprehensive analysis of vegetation cover and carbon emissions, integrating data-driven time series and spatial analysis models to capture both temporal and spatial dynamics. Our findings reveal that hydropower dam construction in the Lancang River Basin has significantly promoted vegetation restoration and growth, concurrently facilitating a reduction in regional carbon emissions. Employing deep learning models for time-series prediction, we observed a substantial increase in the sum of the local normalized difference vegetation index (NDVI) post-construction, with an average rise of from 16.15% to a maximum of 20.12% during the pivotal hydropower dams’ operational phase. Between 2001 and 2020, the construction of hydropower dams in the basin corresponded to notable changes in ecological and carbon metrics. Specifically, vegetation cover expansion intensity (VCEI) reversed from a negative mean of −0.009 to a positive mean of 0.008. Additionally, the carbon emission intensity (CEI) around these dams drastically reduced, shifting from an average of 0.877 to 0.052. Importantly, the Global Moran’s I for VCEI significantly increased from 0.288 pre-2016 to 0.679 post-2015, reflecting a stronger spatial autocorrelation in vegetation patterns. Accordingly, these findings illustrate the complex interplay between hydropower dams and environmental outcomes, underscoring the critical role of pivotal hydropower dam construction in ecological improvement. The research results have improved and complemented those of previous studies on the environmental impact of hydraulic engineering, providing valuable insights for the construction management and policy formulation of hydropower dams in other similar river basins around the world.

Mekong Multi-Cooperation Frameworks: States, Regional Institutions, Private Sectors and Elites

Conflict and cooperation are key governance challenges in transboundary river basin governance. Hydropower has been at the center of conflict and cooperation in the transboundary river basin governance. Over time, hydropower produces a sort of material geopolitics within regions. Technological changes and the changing regional geopolitics create different power relations over hydropower. One of the gaps in current research seems to be about how technological and material transformations of hydropower have affected the transboundary river cooperation in the post-Cold War era.The paper uses a literature review and a case study of the Lower Sasan 2 (LS2) Dam to to study the changing political dimensions of the Mekong region from a confronting platform to multi-regional cooperation frameworks; and how powerful actors such as states, regional institutions, private sectors, and elites shape regional cooperations and produce competing programs and projects in the Mekong region.. It concludes that hydropower has been politicized and technologically manipulated by powerful actors in the last five decades of the Mekong River Cooperation. Cambodia has positioned itself strategically in its relationships with these hydro-hegemons to compete for hydropower dam projects and protect its interests but runs a significant risk of increased social and environmental impacts along with local resistances.

Tides Effects on Short-Time Freshwater Habitat Modifications of Lower Mekong River Delta (SE Vietnam)

Tides Effects on Short-Time Freshwater Habitat Modifications of Lower Mekong River Delta (SE Vietnam)

Composition of Large Prey Species of Irrawaddy Dolphins (Orcaella brevirostris) in the Mekong River: Implications for Conservation of the Prey Resources

Information on the feeding habits of the critically endangered Irrawaddy dolphin (Orcaella brevirostris) in the Mekong River and how their diet overlaps with that of the species targeted by fisheries is limited. The information provided herein will be helpful for evaluating and protecting important dolphin food resources. The composition of large prey species of Irrawaddy dolphins and the extent of fish resources were surveyed in the Mekong River, Cambodia, using local ecological knowledge. The results showed that Irrawaddy dolphins fed on 13 species of large fish, with Pangasius conchophilus, Cyclocheilichthys enoplos, and Hemibagrus wyckii the most frequently consumed prey. Twelve of the 13 reported prey species were usually caught by fishers. The results also revealed that the average weight of fish caught daily by fishers was significantly lower in 2019 than about five years before that, regardless of the season. A significant decline in fish resources and a high overlap of dolphin diets with fishery target species indicate that Irrawaddy dolphins may also be threatened by prey depletion, especially during the dry season when dolphins are concentrated in deep pools.

Heavy Metal Concentrations in Surface Water of the Lower Mekong River Basin (Vietnam)

Heavy Metal Concentrations in Surface Water of the Lower Mekong River Basin (Vietnam)

Numerical simulation study on ship manoeuvrability in mountainous rivers: Comprehensively considering effects of nonuniform flow, shallow water, narrow banks, winds and waves

Ships navigating inland waterways, especially mountainous waterways, may encounter complex navigation environments. Under these circumstances, the force of the ship is extremely complex, the attitude of the ship may be unstable, and the control performance may decrease, possibly resulting in marine accidents. In this study, a modular-type manoeuvring model (MMG) is used to develop a ship manoeuvring model that comprehensively considers multiple factors. Based on this model, numerical simulations are conducted on the ship Seiun Maru, and Esso Osaka; the simulation results are found to be in good agreement with the results of real ship motions. Then, numerical simulations are conducted on the navigation of a 500-ton ship in a typical mountainous waterway, the Suoluo Rapids in the Lancang River, and the impact of the complex environment in this area on the safety of ship navigation is explored. The results reveal that ignoring the influence of environmental factors may put ships in dangerous situations when navigating mountain waterways. In addition, the model can effectively simulate the manoeuvring motion of a ship in a typical mountain waterway, and the calculation cost is negligible. This study provides valuable suggestions for long-distance ship manoeuvring in complex inland river environments.