Sedimentation in the Manwan reservoir in the Upper Mekong and its downstream impacts

Fu, Kai; He, Daming; Lu, Xixi

doi:10.1016/j.quaint.2007.09.041

Cited by 119 publications

(71 citation statements)

References 10 publications

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“…Manwan Dam built in the Lancang-Mekong River changed the flow velocity and converted the river into a sedimentary environment because of the alteration of runoff (Fu et al, 2008). In this study, we further studied the effects of the dam on the physical and chemical profiles of the sediment and found that the dam may be associated with the spatial variations of Cd, Zn and Mg in the sediment profiles and the distribution of physical fractions.…”

Section: Resultsmentioning

confidence: 87%

“…At the same time, dams have influences on the development of riverine ecosystem (Bai et al, 2009). After dams begin to run, the flow speed decreases and more sediments deposit in reservoir because of changes in the hydrological regime (Fu et al, 2008). Sediments in river system are sinks and the potential sources of pollutions such as heavy metals and nutrients (DelValls et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Reservoir sedimentation, as an important hazard in hydroelectric construction in the Lancang-Mekong River basin, has been widely concerned by scholars in recent years. Fu et al (2008) found that the Manwan Reservoir lost approximately 21.5-22.8% of its total storage capacity because of the sediment trap. Kummu and Varis (2007) reported that the flux of sediment from the upper Mekong River basin has been decreasing as a reason of sediment trapping by dams.…”

Section: Introductionmentioning

confidence: 99%

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Spatial distribution and environmental risk of major elements in surface sediments associated Manwan Dam in Lancang River, China

Zhao

Dong

Sylvie

et al. 2015

EJSS

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Article Info Received : 13.07.2014 Accepted : 22.11.2014 Bulk elements and grain sizes in sediments collected at upstream and downstream of Manwan Dam were studied to demonstrate the spatial distribution of heavy metals in the sediments and to assess their risk. Correlation analysis showed that the spatial distribution of Cd, Zn and Mg were significantly affected by dam construction. PCA analysis demonstrate that Cd and Zn were both controlled by Ca, As, Pb, organic matter and clay. Mg was controlled by silt, Al, P and K. The risk assessment demonstrated that the pollution of Cd, As, Zn were more serious than other heavy metals. Fine-grained sediments with higher risk level were found in the section near the upstream of dam, while coarse-grained ones with lower risk level were found in the section far away from the downstream of dam. The sections in tributary were lower in risk than those in the main stream. Heavy metal concentrations in the mainstream sediments were influenced by dam construction and those in tributary were influenced by both dam construction and human activities in locality. Unusual high concentrations of Cd, As, and Zn in both sections implied that more pollution prevention measures are needed in the Manwan Dam in order to prevent increased heavy metal pollutions in the Lancang-Mekong River.

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Section: Resultsmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatial distribution and environmental risk of major elements in surface sediments associated Manwan Dam in Lancang River, China

Zhao

Dong

Sylvie

et al. 2015

EJSS

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“…3992 N. V. K. Triet et al: Dyke development and flood hazard in the VMD starvation as a consequence of massive hydropower development (Fu and He, 2007;Kummu and Varis, 2007;Fu et al, 2008;Kummu et al, 2010;Xue et al, 2011;Gupta et al, 2012;Manh et al, 2015). In a recent study, Manh et al (2015) estimated the delta sedimentation and the amount of sediment reaching the South China Sea to be diminished by 40-95 % considering hydropower development scenarios, climate change, sea level rise and the deltaic land subsidence.…”

Section: Introductionmentioning

confidence: 99%

Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream?

Triet

Dũng

Fujii

et al. 2017

Hydrol. Earth Syst. Sci.

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Abstract. In the Vietnamese part of the Mekong Delta (VMD) the areas with three rice crops per year have been expanded rapidly during the last 15 years. Paddy-rice cultivation during the flood season has been made possible by implementing high-dyke flood defenses and flood control structures. However, there are widespread claims that the highdyke system has increased water levels in downstream areas. Our study aims at resolving this issue by attributing observed changes in flood characteristics to high-dyke construction and other possible causes. Maximum water levels and duration above the flood alarm level are analysed for gradual trends and step changes at different discharge gauges. Strong and robust increasing trends of peak water levels and duration downstream of the high-dyke areas are found with a step change in 2000/2001, i.e. immediately after the disastrous flood which initiated the high-dyke development. These changes are in contrast to the negative trends detected at stations upstream of the high-dyke areas. This spatially different behaviour of changes in flood characteristics seems to support the public claims. To separate the impact of the highdyke development from the impact of the other drivers -i.e. changes in the flood hydrograph entering the Mekong Delta, and changes in the tidal dynamics -hydraulic model simulations of the two recent large flood events in 2000 and 2011 are performed. The hydraulic model is run for a set of scenarios whereas the different drivers are interchanged. The simulations reveal that for the central VMD an increase of 9-13 cm in flood peak and 15 days in duration can be attributed to high-dyke development. However, for this area the tidal dynamics have an even larger effect in the range of 19-32 cm. However, the relative contributions of the three drivers of change vary in space across the delta. In summary, our study confirms the claims that the high-dyke development has raised the flood hazard downstream. However, it is not the only and not the most important driver of the observed changes. It has to be noted that changes in tidal levels caused by sea level rise in combination with the widely observed land subsidence and the temporal coincidence of high water levels and spring tides have even larger impacts. It is recommended to develop flood risk management strategies using the high-dyke areas as retention zones to mitigate the flood hazard downstream.

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“…In total, 48 % of the local species have disappeared in this area in 20 years from 1987 to 2007 (Kang et al 2009). Moreover, Manwan Dam trapped about 60 % of sediments into its reservoir (Fu et al 2008), and Kummu and Varis (2010) predict the sediment trapping efficiency would reach as much as 94 % for the whole cascade of eight dams, which would dramatically reduce the amount of nutrients flowing to the Lower Mekong, further affecting fish biodiversity (Osmundson et al 2002).…”

mentioning

confidence: 99%

What Do the Occurrences of Migratory Fishes in the Upper Mekong Mean?

Kang

2013

AMBIO

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This paper examines the recent appearance of four migratory species in the Upper Mekong: Dasyatis laosensis, Anguilla bicolor, Anguilla marmorata, and Chitala ornata. Since 2006 these species have been continually sampled in an area below Jinghong Dam in Xishuangbanna, China. This region is far beyond their historical upstream distribution, and the reasons for these appearances and their subsequent impact on river ecosystem are considered.

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Sedimentation in the Manwan reservoir in the Upper Mekong and its downstream impacts

Cited by 119 publications

References 10 publications

Spatial distribution and environmental risk of major elements in surface sediments associated Manwan Dam in Lancang River, China

Spatial distribution and environmental risk of major elements in surface sediments associated Manwan Dam in Lancang River, China

Has dyke development in the Vietnamese Mekong Delta shifted flood hazard downstream?

What Do the Occurrences of Migratory Fishes in the Upper Mekong Mean?

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