Quantifying the impact of upstream dams on the sediment load in the Vu Gia Thu Bon river basin

Abstract

    The infrastructure works such as reservoirs and water transfer structures are considered as one of the causes of changes in streamflow and sediment in the Vu Gia Thu Bon River basin. This leads to increasingly serious saline intrusion downstream, affecting water supply and agricultural production. In this paper, we examined the effects of reservoirs using the semi-distributed hydrological model SWAT. The SWAT model has been established for the entire VGTB basin for the period 1990 to 2020 and considers the operation of eighteen hydropowers. We find that the average annual sediment load has decreased in Vu Gia and Thu Bon Rivers in the post-dam period compared with the pre-dam period.
In which, the average annual sediment load biggest decreased at Ai Nghia station on Vu Gia River (decreased 57.3%). At Giao Thuy station on Thu Bon River, the sediment load decreased by 1.58 million tons (23.8%). In upstream, the average annual sediment load also decreased in both Thanh My and Nong Son stations by 0.34, 1.41 million tons, respectively. The results of the study have provided additional useful insights into the effects of the dam on the flow regime, concentration, and sediment load in the Vu Gia Thu Bon River basin. The investigated sediment changes helped to better understand the changes in morphology, water level, and saline intrusion downstream