Recent evolution of the Mekong Delta and the impacts of dams

Li, Xing; Liu, Paul; Saito, Yoshiki; Nguyen, Van Lap

doi:10.1016/j.earscirev.2017.10.008

Cited by 156 publications

(108 citation statements)

References 111 publications

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“…The measured net suspended sediment load over the period 2009-2016 as compared to previous estimates of sediment supply in the lower Mekong delta are consistent with such a scenario of a huge decrease in the 2000s, with a reduction from 145-160 Mt yr −1 to~40 Mt yr −1 (by~70-75%) in three or four decades. These estimates are consistent as well with the observed increase of shoreline erosion (with currently 66% of shorelines eroded) and the decrease of Mekong Delta area, since 2005 [42].…”

Section: Discussionsupporting

confidence: 88%

“…This decrease (of the order of −5% per year), accentuated in the wet season as compared to the dry season, was such that the difference between suspended sediment concentrations in dry and wet season kept going smaller so as to become almost equal in 2011. In another study of the shoreline change based on a 43-year Landsat image database (1973-2015), Li et al [42] showed that the 600-km of coasts shifted from mainly accreted (at 68% between 1973 and 1988) to mainly eroded (at 56%, during 2005-2015). While most of the shorelines was in accretion until 2005, most has become eroded after 2005.…”

Section: Looking For Breaking Pointsmentioning

confidence: 99%

“…While most of the shorelines was in accretion until 2005, most has become eroded after 2005. Currently, 66% of the delta is under erosion, and the Mekong Delta has undergone a shift from growth to shrinkage since 2005 [42].…”

Section: Looking For Breaking Pointsmentioning

confidence: 99%

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Water and Suspended Sediment Budgets in the Lower Mekong from High-Frequency Measurements (2009–2016)

Ouillon

Vinh³

2018

Water

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Based on a new dataset of high temporal resolution of water discharge (hourly frequency) and suspended sediment concentration (twice daily frequency at ebb and flood tides) at Can Tho and My Thuan stations during the 2009-2016 period, monthly and annual flow and suspended sediment flux of the lower Mekong River were calculated. The present water discharge of the Mekong River to the sea can be estimated to be 400 km 3 yr −1 , +/− 100 km 3 yr −1 depending on El Niño Southern Oscillation (ENSO), and the present sediment supply to the sea can be estimated to be 40 Mt yr −1 , +/− 20 Mt yr −1 depending on ENSO. The ENSO influence (proxied by the Southern Oscillation Index-SOI) on Q (water discharge) and Qs (sediment flux) is at maximum at a time lag of 8-9 months. The 2010-2011 La Niña event increased the water supply by almost 30% and the sediment supply by 55% in 2011. The 2015-2016 El Niño event decreased the water supply by 20% and the sediment supply by 50% in 2015-2016. The average net water discharge was 12,550 m 3 s −1 in neutral years. The Tien River at My Thuan accounted for~52%, and the Hau River at Can Tho for 48% of the total Mekong River discharge, with small variations (of the order 1%) amongst years. In terms of suspended sediment delivery to the sea, the Tien River accounted for a more variable portion of 55% in neutral years, 57.3% in 2015-2016 (El Niño) and 62% in 2011 (La Niña). 80% of water discharge occurred during the flood season (July-December) and 20% occurred in the low flow season (January-June), the proportion being 91% and 9% for the sediment supply. Previous estimates of annual sediment supplies to the sea (145-160 Mt yr −1) had been established before 2003. Possible origins of the recent reduction by~75% of sediment supply are presented and discussed.

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Section: Discussionsupporting

confidence: 88%

Section: Looking For Breaking Pointsmentioning

confidence: 99%

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Water and Suspended Sediment Budgets in the Lower Mekong from High-Frequency Measurements (2009–2016)

Ouillon

Vinh³

2018

Water

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“…On the Mekong, the construction of hydropower cascades upstream in Yunnan is altering the river's hydrology by averaging out the wet and dry season flows. This is highly problematic as it disrupts the ecological flow of the ecosystem and so places species and sensitive areas at risk (Räsänen et al 2017;Li et al 2017). This also has implications for food security due to disrupted fish migratory patterns, saline intrusion in the delta regions and loss of soil fertility from decreased sediment loads.…”

Section: Ecological Impacts and Climate Changementioning

confidence: 99%

The hydropower myth

Williams

2019

Environ Sci Pollut Res

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Hydropower has come to be treated as synonymous with sustainable economic development by many in the development arena. This is despite the adverse ecological and sociological impacts being widely recognised by those outside of decision-making. The prevalence of this 'hydropower myth' simplifies the complex trade-offs involved within hydropower development and often leads to inequitable situations and ecological damage. The Mekong River is used to demonstrate the strength of the hydropower myth-the disconnect with the social and ecological realities of the basin, and emerging and potential negative consequences. The attractiveness of the hydropower myth to decision-makers and developers is shown to lie largely in its political utility in bolstering national power and legitimacy as well as its ability to channel economic benefits towards states and developers.

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“…Upstream, flow patterns have become abnormally varied due to the construction of numerous dams [9,14,16,17]. The main streams of the Mekong River are now blocked by six mega-reservoirs, and 40 smaller reservoirs regulate flows on tributaries [18,19]. Moreover, that number of upstream reservoirs is set to double by 2030, according to the Ministry of Natural Resources and Environment of Vietnam.…”

Section: Introductionmentioning

confidence: 99%

Exploring Freshwater Regimes and Impact Factors in the Coastal Estuaries of the Vietnamese Mekong Delta

Dang

Tran

Pham

et al. 2019

Water

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Freshwater resources make an essential contribution to the livelihoods of millions of local people in the coastal estuaries of the Vietnamese Mekong Delta (VMD). However, coastal freshwaters currently face numerous threats, not least (i) changing tidal dynamics due to sea level rise and (ii) changes in river regimes due to dam construction upstream. This research explores the evolution of freshwater regimes in these coastal estuaries. Using process diagrams, freshwater distributions are mapped and analyzed. Application of statistical methods provides insight into freshwater flow cycles and variations in water regimes upstream at various measurement points within the estuaries. A previously calibrated and validated hydraulic model is used to simulate drought-year scenarios and spatial changes in freshwaters over time. Findings indicate decreasing river discharges in the flood season, but increasing discharges in the dry season, due to the impacts of hydropower dams. In addition, the driest months are shifting earlier. From this data, we derive rules of thumb regarding freshwater distributions in the coastal estuaries of the VMD. These relate to (i) the boundary beyond which freshwater is always found; (ii) the boundary where freshwater appears daily; (iii) the start of the freshwater season; (iii) the boundary where freshwater appears until February and until April; (iv) the end of the flood season; and (v) the number of days without freshwater per year. The trends discerned will help local freshwater users and decision makers formulate forward-looking, flexible strategies for freshwater exploitation, while also providing avenues for further research.

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Recent evolution of the Mekong Delta and the impacts of dams

Cited by 156 publications

References 111 publications

Water and Suspended Sediment Budgets in the Lower Mekong from High-Frequency Measurements (2009–2016)

Water and Suspended Sediment Budgets in the Lower Mekong from High-Frequency Measurements (2009–2016)

The hydropower myth

Exploring Freshwater Regimes and Impact Factors in the Coastal Estuaries of the Vietnamese Mekong Delta

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