Assessment of Dam Impacts on Flow and Sediment in the Sai Gon-Dong Nai River Basin, Vietnam

Abstract

This paper examined the impact of dams on the long-term flow regime and suspended sediment alterations in the Sai Gon-Dong Nai River Basin from the 1980s to 2021 using various statistical methods. The results show that dams in the Dong Nai and La Nga sub-basins are the main drivers of the flow alteration downstream, given that there is a discrepancy in the flow discharge variation between the upstream and downstream hydrological stations. In the Be sub-basin, the Phuoc Hoa diversion reservoir controlled the dry-season discharge reduction in the post-dam period (2011-2021), while climate variability drove the flood-season discharge decrease, exacerbated by the Thac Mo reservoir. We also found that deforestation in the Dong Nai River was the main driving force of the SSC increase at Ta Lai, while dams had insignificant effects. Differently, rainfall reduction and dams led to the SSC reduction in the La Nga River.