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,
[email protected]
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,
[email protected]
NGUYEN PHUONG MAI
Faculty of Civil Engineering, Thuyloi University-Southern
Campus,
Ho Chi Minh City, Vietnam,
[email protected]
TETSUYA SUMI
Water Resources Research Center, Disaster Prevention
Research Institute,
Kyoto University, Kyoto, Japan,
[email protected]
LA VINHTRUNG
Research Management Department,
Vietnamese-German University, Binh Duong Province,
Vietnam,
[email protected]
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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