Author(s): Doan Van Binh; Tetsuya Sumi; Sameh Kantoush; Nguyen Phuong Mai; La Vinh Trung
Linked Author(s): Tetsuya Sumi
Keywords: Mekong River (MR); Vietnamese Mekong Delta (VMD); Sediment budget; Flow regime
Abstract: Dams and reservoirs have been increasingly developed in the Mekong River basin where fifty dams have been built by 2015. Locating in the mainstream and having the largest reservoirs’ capacity, possible impacts of the six Lancang cascade dams (LCDs) on the flow regimes and sediment budgets of the Vietnamese Mekong Delta (VMD) were evaluated in this study. The results showed that the sediment responding to the constructions of the LCDs were faster than the flow regime. The first four dams in the cascade had no clear impact on the annual flow regime in the VMD; however, the impacts of all six existing LCDs were significant. The maximum and minimum discharges have decreased by 20.2% and increased by 93.2%, respectively. All 50 existing dams in the basin have caused a reduction of 73% of the sediment budget of the VMD. Among this, 48% has been directly caused by six existing LCDs, in which the first two dams of the cascade (Manwan and Dachaoshan) were the direct cause of 38 % reduction. Such changes of the flow regimes and sediment budget may consequently cause negative impacts on other various sectors such as agriculture, fisheries, river and coastal erosion, and ecosystem.
Year: 2018