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Kongmeng Ly
School of Biological Earth and Environmental Sciences, Faculty of Sciences, UNSW Sydney, Australia

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Journal article
Published: 23 August 2021 in Science of The Total Environment
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Transboundary river basins across developing countries, such as the Lower Mekong River Basin (LMB), are challenging to manage given frequent divergences on development and conservation priorities. Driven by needs to sustain economic performance and reduce poverty, the LMB countries are embarking on significant land use changes in the form of more hydropower dams, to satisfy growing energy demands. This pathway could lead to irreversible changes to the ecosystem of the Mekong River, if not properly managed. Given the uncertain environmental externalities and trade-offs associated with further hydropower development and operation in the LMB, this research develops four plausible scenarios of future hydropower operation, and assesses their likely impact on streamflow and instream total suspended solids and nitrate loads of the Mekong River. The findings suggest that further hydropower operations on either tributary or mainstream could result in annual and wet season flow reduction between 11 and 25% while increase dry season flows by 1 to 15%, when compared to a business-as-usual scenario. Conversely, hydropower operation on both tributary and mainstream could result in dry season flow reduction between 10 and 15%. Both instream TSS and nitrate loads are forecasted to reduce under all three scenarios by as much as 78 and 20%, respectively, compared to the business-as-usual one. These effects are predicted to magnify under extreme climate conditions with dry season flow, TSS, and nitrate levels reduced by as much as 44, 81 and 35%, respectively, during a projected extreme dry climate condition, but less severe under improved operational alternatives. With further hydropower development in the LMB being highly unavoidable, these findings can inform effective transboundary management pathways for balancing electricity generation and protection of riverine ecology, water and food security, and people livelihoods.

ACS Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. Transboundary river basins: Scenarios of hydropower development and operation under extreme climate conditions. Science of The Total Environment 2021, 149828 .

AMA Style

Kongmeng Ly, Graciela Metternicht, Lucy Marshall. Transboundary river basins: Scenarios of hydropower development and operation under extreme climate conditions. Science of The Total Environment. 2021; ():149828.

Chicago/Turabian Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. 2021. "Transboundary river basins: Scenarios of hydropower development and operation under extreme climate conditions." Science of The Total Environment , no. : 149828.

Journal article
Published: 06 July 2020 in Science of The Total Environment
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The management of LULC changes in transboundary river basins continues to challenge water resources managers due to the differences in development and conservation priorities of the countries sharing the basin. While various watershed models (WMs) exist to support decision making, basin-wide sustainable application of the instituted WM depends on the management priorities, resources, data availability, and knowledge gaps at national and sub-basin levels. Building on the results of our prior comparative analysis of WMs for a large transboundary river basin, we applied the ‘Source’ model to the Lower Mekong Basin (LMB). The constructed LMB-Source model was evaluated based on its streamflow and instream total suspended solids (TSS) and nitrate loads simulative performances. A combination of predictive performance metrics (PPMs) and sophisticated hydrologic signatures were used to calibrate model parameters and diagnose the model performance. Calibration results indicated strong similarity between the simulated and observed time series data and were further confirmed by the validation results. The successful model calibration generated parameters that represent hydrologic response characteristics (HRCs) and overland TSS and nitrate generation and removal dynamics (GRDs) previously not available for the LMB. The HRCs and GRDs can be regionalised with physical attributes of the LMB in future studies which can be used to support the management of ungauged sub-basins. This study confirms Source's capability as a decision support tool for the management of transboundary river basins, and provides basin-specific values of HRCs and GRDs that can be used for a better evaluation of the potential effects of LULC changes.

ACS Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. Simulation of streamflow and instream loads of total suspended solids and nitrate in a large transboundary river basin using Source model and geospatial analysis. Science of The Total Environment 2020, 744, 140656 .

AMA Style

Kongmeng Ly, Graciela Metternicht, Lucy Marshall. Simulation of streamflow and instream loads of total suspended solids and nitrate in a large transboundary river basin using Source model and geospatial analysis. Science of The Total Environment. 2020; 744 ():140656.

Chicago/Turabian Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. 2020. "Simulation of streamflow and instream loads of total suspended solids and nitrate in a large transboundary river basin using Source model and geospatial analysis." Science of The Total Environment 744, no. : 140656.

Journal article
Published: 08 April 2020 in Sustainability
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Population growth and economic development are driving changes in land use/land cover (LULC) of the transboundary Lower Mekong River Basin (LMB), posing a serious threat to the integrity of the river system. Using data collected on a monthly basis over 30 years (1985–2015) at 14 stations located along the Lower Mekong river, this study explores whether spatiotemporal relationships exist between LULC changes and instream concentrations of total suspended solids (TSS) and nitrate—as proxies of water quality. The results show seasonal influences where temporal patterns of instream TSS and nitrate concentrations mirror patterns detected for discharge. Changes in LULC influenced instream TSS and nitrate levels differently over time and space. The seasonal Mann–Kendall (SMK) confirmed significant reduction of instream TSS concentrations at six stations (p < 0.05), while nitrate levels increased at five stations (p < 0.05), predominantly in stations located in the upper section of the basin where forest areas and mountainous topography dominate the landscape. Temporal correlation analyses point to the conversion of grassland (r = −0.61, p < 0.01) to paddy fields (r = 0.63, p < 0.01) and urban areas (r = 0.44, p < 0.05) as the changes in LULC that mostly impact instream nitrate contents. The reduction of TSS appears influenced by increased forest land cover (r = −0.72, p < 0.01) and by the development and operation of hydropower projects in the upper Mekong River. Spatial correlation analyses showed positive associations between forest land cover and instream concentrations of TSS (r = 0.64, p = 0.01) and nitrate (r = 0.54, p < 0.05), indicating that this type of LULC was heavily disturbed and harvested, resulting in soil erosion and runoff of nitrate rich sediment during the Wet season. Our results show that enhanced understanding of how LULC changes influence instream water quality at spatial and temporal scales is vital for assessing potential impacts of future land and water resource development on freshwater resources of the LMB.

ACS Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. Linking Changes in Land Cover and Land Use of the Lower Mekong Basin to Instream Nitrate and Total Suspended Solids Variations. Sustainability 2020, 12, 2992 .

AMA Style

Kongmeng Ly, Graciela Metternicht, Lucy Marshall. Linking Changes in Land Cover and Land Use of the Lower Mekong Basin to Instream Nitrate and Total Suspended Solids Variations. Sustainability. 2020; 12 (7):2992.

Chicago/Turabian Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. 2020. "Linking Changes in Land Cover and Land Use of the Lower Mekong Basin to Instream Nitrate and Total Suspended Solids Variations." Sustainability 12, no. 7: 2992.

Review
Published: 05 June 2019 in Journal of Hydrology: Regional Studies
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The management of transboundary river basins is challenging given frequent divergences in political, cultural, developmental and conservation priorities of countries that make up the basin. In the Lower Mekong River Basin where multiple countries are beneficiaries of its water resources, ensuring good quality of the river waters is crucial for sustainable development, and for protecting the integrity of its ecosystems. The focus of this paper is on identifying an appropriate decision support tool for assisting the management of in-stream nutrients and sediment concentrations taking into account the abilities to (i) satisfactory simulate hydrological processes and pollutant loadings in a time continuous manner; (ii) simulate the effects of various land use change scenarios; (iii) handle issues of data scarcity and compatibility stemming from different development policies and priorities of each administrative jurisdiction; (iv) have a record of previous applications in a large transboundary river basin; and (v) have a track record of use by government agencies to support decision making. These criteria guide in-depth analysis of 250 peer-reviewed journal papers. Four models meet the pre-determined criteria, with eWater Source providing a comparative advantage of prior use in a transboundary catchment larger than the Lower Mekong River Basin.

ACS Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. Transboundary river catchment areas of developing countries: Potential and limitations of watershed models for the simulation of sediment and nutrient loads. A review. Journal of Hydrology: Regional Studies 2019, 24, 100605 .

AMA Style

Kongmeng Ly, Graciela Metternicht, Lucy Marshall. Transboundary river catchment areas of developing countries: Potential and limitations of watershed models for the simulation of sediment and nutrient loads. A review. Journal of Hydrology: Regional Studies. 2019; 24 ():100605.

Chicago/Turabian Style

Kongmeng Ly; Graciela Metternicht; Lucy Marshall. 2019. "Transboundary river catchment areas of developing countries: Potential and limitations of watershed models for the simulation of sediment and nutrient loads. A review." Journal of Hydrology: Regional Studies 24, no. : 100605.