Changes to long-term discharge and sediment loads in the Vietnamese Mekong Delta caused by upstream dams

Binh, Doan Van; Kantoush, Sameh A.; Takemon, Yasuhiro

doi:10.1016/j.geomorph.2019.107011

Cited by 121 publications

(67 citation statements)

References 39 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The LSS 2, for example, is actually ecologically critical due to its location just downstream of the confluence of the Srepok and Sesan Rivers and near the 3S rivers junction. Even though our results have shown comparatively low HA with respect to hydropower production, the LSS 2 dam will disconnect the upstream 3S ecological system from critical Mekong ecosystems [78,79] and thus could be one of the most ecologically damaging reservoirs of the basin. However, the IHA tool does quantify the relative changes in the hydrologic regime, and therefore, quantifications of HA will help in the broader analysis of ecological impacts.…”

Section: Ha Due To Reservoir Operations and Climate Changecontrasting

confidence: 57%

Development of a SWAT Hydropower Operation Routine and Its Application to Assessing Hydrological Alterations in the Mekong

Shrestha

Pahlow

Cochrane

2020

Water

View full text Add to dashboard Cite

Reservoir operations and climate change can alter natural river flow regimes. To assess impacts of climate and hydropower operations on downstream flows and energy generation, an integrated hydropower operations and catchment hydrological model is needed. The widely used hydrological model Soil and Water Assessment Tool (SWAT) is ideal for catchment hydrology, but provides only limited reservoir operation functions. A hydropower reservoir operation routine (HydROR) was thus developed for SWAT to analyze complex reservoir systems under different policies. The Hydrologic Engineering Center’s Reservoir System Simulation (HEC-ResSim) model, a well-established reservoir simulation model, was used to indirectly evaluate functionality of the HydROR. A comparison between HydROR and HEC-ResSim under a range of operation rule curves resulted in R2 values exceeding 0.99. The HydROR was then applied to assess hydrological alterations due to combined impacts of climate change and reservoir operations of 38 hydropower dams in the 3S basin of the Mekong River. Hydropower production under climate change varied from −1.6% to 2.3%, depending on the general circulation model chosen. Changing the hydropower operation policy from maximizing energy production to maintaining ecological flows resulted in a production change of 13%. The calculation of hydrological alteration indices at the outlet of the 3S basin revealed that over 113% alteration in the natural river outflow regime occurred from the combined impacts of climate change and reservoir operations. Furthermore, seasonal flows and extreme water conditions changed by 154% and 104%, respectively. Alterations were also significant within the basin, and, as expected, were larger for high-head and small-river reservoirs. These alterations will adversely affect ecological dynamics, in particular, habitat availability. HydROR proved to be a valuable addition to SWAT for the analyses of complex reservoir systems under different policies and climate change scenarios.

show abstract

Section: Ha Due To Reservoir Operations and Climate Changecontrasting

confidence: 57%

Development of a SWAT Hydropower Operation Routine and Its Application to Assessing Hydrological Alterations in the Mekong

Shrestha

Pahlow

Cochrane

2020

Water

View full text Add to dashboard Cite

show abstract

“…Although the larger part of the sediment inflow is accumulated in the reservoir, its sediment retention capacity over the half-century has dropped from 90% to 70-85%. Such trap efficiencies are common for most lowland reservoirs (Berkovich 2012;Le et al 2020;Piqué et al 2017;Suif et al 2017;Van Binh et al 2020). We attribute this to the progressing siltation of the reservoir, combined with an increased production of autochtonous particulate organic matter and its subsequent outflow from the reservoir due to its continuous eutrophication (Datsenko et al 2017), which creates additional biogenic sediment flux.…”

Section: Discussionmentioning

confidence: 80%

“…Reservoirs interrupt the transit of suspended sediment with river runoff, trapping up to 50-90% and more of the incoming sediment flux and altering the distribution between particles of different sizes (Hojan and Rurek 2017;Berkovich 2012;Le et al 2020;Piqué et al 2017;Suif et al 2017;Van Binh et al 2020). This effect is particularly evident in cascades of reservoirs and in large reservoirs located in mouth zones of rivers, where the sediment retention rate may reach 100% (Guo et al 2020;Huang et al 2018;Ibàhez et al 1996), although in the case of rivers with large sediment loads cascade reservoirs have lesser retention potential (Wu et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Impact Of Mozhaysk Dam On The Moscow River Sediment Transport

Соколов

Erina

Tereshina

et al. 2020

GES

View full text Add to dashboard Cite

Sediments are an essential part of the aquatic environment that define its transformation and development. The construction of dams results in severe changes in sediment fluxes. This study aims to assess how the sediment load of the upper Moskva River is affected by the Mozhaysk Dam flow regulation and to estimate its dynamics over the years of the reservoir’s existence. Our analysis of the 1968, 2012 and 2016 detailed field data shows a 20-40% decrease in the proportion of the spring flood in the annual sediment load into the reservoir, which is caused by changes in the streamflow regime of the inflowing rivers. The peak suspended sediment concentrations have decreased 5- to 10-fold, likely due to a significant decline in the watershed’s cultivated land area, which caused a decrease in the erosion rate. In the Moskva River below the dam, the seasonal dynamics of the suspended sediment concentration no longer corresponds to the natural regime. The annual suspended load of the Moskva River below the Mozhaysk Reservoir decreased up to 9-fold. The sediment retention in the reservoir has dropped from 90% to 70-85% and is to some extent restored by an outflow of the particulate organic matter produced in the reservoir. We also described the relationships between water turbidity and suspended sediment concentration of the reservoir’s tributaries, which allow for the first time to estimate the sediment load with higher accuracy than was previously possible.

show abstract

“…The daily suspended sediment loads were then estimated as the products of daily SSCs and the respective daily discharges. The details of the data sources and treatment of the sediment load data were described by Binh et al (2020).…”

Section: Flow Sediment and Salinity Datamentioning

confidence: 99%

“…However, the effects of riverbed incision on hydrological processes are poorly understood because of the complex interactions among the fluvial flows and tidal regimes. Recently, Binh et al (2020) examined the effects of upstream dams on the discharges, sediment loads and morphological changes in the VMD. They found that upstream dams have small effects on the annual daily mean discharge, although these dams are the main causes of sediment reduction and riverbed incision.…”

Section: Introductionmentioning

confidence: 99%

Effects of riverbed incision on the hydrology of the Vietnamese Mekong Delta

Binh

Kantoush

Takemon

et al. 2021

Hydrological Processes

Self Cite

View full text Add to dashboard Cite

The hydrogeomorphology of the Vietnamese Mekong Delta (VMD) has been significantly altered by natural and anthropogenic drivers. In this study, the spatiotemporal changes of the flow regime were examined by analysing the long-term daily, monthly, annual and extreme discharges and water levels from 1980 to 2018, supported by further investigation of the long-term annual sediment load (from the 1960s to 2015), river bathymetric data (in 1998, 2014 and 2017) and daily salinity concentration (from the 1990s to 2015) using various statistical methods and a coupled numerical model. Then, the effects of riverbed incision on the hydrology were investigated. The results show that the dry season discharge (i.e., in March-June) of the Tien River increased by up to 23% from the predam period (1980-1992) to the postdam period (1993-2018) but that the dry season water level at My Thuan decreased by up to −46%. The annual mean and monthly water levels in June at Tan Chau and in January and June-October at My Thuan in the Tien River decreased statistically, even though the respective discharges increased significantly. These decreased water levels instead of the increased discharges were attributed to the accelerated riverbed incision upstream from My Thuan, which increased by more than three times, from a mean rate of −0.16 m/year (−16.7 Mm 3 /year) in 1998-2014 to −0.5 m/year (−52.5 Mm 3 /year) in 2014-2017. This accelerated riverbed incision was likely caused by the reduction in the sediment load of the VMD (from 166.7 Mt/year in the predam period to 57.6 Mt/year in the postdam period) and increase in sand mining (from 3.9 Mm 3 in 2012 to 13.43 Mm 3 in 2018). Collectively, the decreased dry season water level in the Tien River is likely one of the main causes of the enhanced salinity intrusion.

show abstract

Changes to long-term discharge and sediment loads in the Vietnamese Mekong Delta caused by upstream dams

Cited by 121 publications

References 39 publications

Development of a SWAT Hydropower Operation Routine and Its Application to Assessing Hydrological Alterations in the Mekong

Development of a SWAT Hydropower Operation Routine and Its Application to Assessing Hydrological Alterations in the Mekong

Impact Of Mozhaysk Dam On The Moscow River Sediment Transport

Effects of riverbed incision on the hydrology of the Vietnamese Mekong Delta

Contact Info

Product

Resources

About