IMPACTS ASSESSMENTS OF DAM DEVELOPMENT ON FLOW, SEDIMENT, AND SALINITY INTRUSION INTO VIETNAMESE MEKONG DELTA
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SAMEH KANTOUSH

IMPACTS ASSESSMENTS OF DAM DEVELOPMENT ON FLOW,

SEDIMENT, AND SALINITY INTRUSION INTO VIETNAMESE

MEKONG DELTA

 

SAMEH KANTOUSH

Water Resources Research Center,

Disaster Prevention Research Institute, Kyoto University, Kyoto, Japan,

kantoush.samehahmed.2n@kyoto-u.ac.jp

DOAN VAN BINH

Faculty of Water Resources Engineering,

Thuyloi University-Southern Campus, Ho Chi Minh City, Vietnam

Water Resources Research Center, Disaster Prevention Research Institute,

Kyoto University, Kyoto, Japan,

binhdv@tlu.edu.vn

NGUYEN PHUONG MAI

Faculty of Civil Engineering, Thuyloi University-Southern Campus,

Ho Chi Minh City, Vietnam,

maiswru@tlu.edu.vn

TETSUYA SUMI

Water Resources Research Center, Disaster Prevention Research Institute,

Kyoto University, Kyoto, Japan,

sumi.tetsuya.2s@kyoto-u.ac.jp

LA VINHTRUNG

Research Management Department,

Vietnamese-German University, Binh Duong Province, Vietnam,

trung.lv@vgu.edu.vn

 

 

Flow and sediment budgetof the Mekong River (MR)is of typical importance for the sustainability and survivability of the Vietnamese Mekong Delta (VMD) in the context of sea level rise due to climatic change. The VMD is sinking and shrinking due to rapidly morphologicaldegradation caused byaltered flow regime and reduced sediment supply from the MR as the result of upstream hydropower dams’ development.Dam-induced morphological degradation have further caused increasing salinity intrusion in the VMD. Within the framework of JASTIP project, Kyoto University research groups conducted several boat-based field surveys in 2017-2019 along main rivers and distributaries of the VMD to measure flow and sediment behaviors, river bathymetry, and salinity concentrations. We estimated that the riverbed of the target region near the Cu Lao Tay island in the Tien River was incised by -1.46 m (or -0.49 m/yr) over the period 2014-2017, which was nearly double that during the period 1998-2008, when the riverbed was incised by a rate of -0.25 m/yr. We revealed that rapid riverbed incision in the VMD was consistent with significant decrease of the sediment budget of the MR, which was decreased from 166.7 Mt/yr in the predam period (pre-1992) to 43.1 Mt/yr in thepostdam period (2012-2015), when 64 hydropower dams have been completed in the MR basin. Moreover, reduced high-flow discharges from the MR due to upstream hydropower dam operations - resulting in the reduction of the flow power necessary to transport the sediment - is more likely one of the drivers of the riverbed incision in the VMD. Due to riverbedincision and upstream dam developments, salinity intrusion in the VMDhas been significantly increased.Therefore, collaboratively integrated management of the MR among riparian countries is important for the sustainability and survivability of the VMD.

Keywords:Riverbed incision, Vietnamese Mekong Delta (VMD), Mekong River (MR), sediment budget, hydropower dams, salinity intrusion.

 

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