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The Vietnamese Mekong Delta, its flood-prone areas and the location of measuring stations (red dots). The names in black indicate the provinces in the VMD.
Source publication
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 high-dyke system has...
Contexts in source publication
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... findings disagree with public and several officials' claims that the high-dyke development in the upper part of the MD is the main factor for the higher and longer floods in Can Tho and the central part of the Mekong Delta. For this region it is rather the combination of all three factors, with the lower boundary, or the timing of high flood levels and tidal levels that is dominating. The further downstream the station location, the higher the impact of the tidal water level. Hence, sea level rise and land subsidence are important fac- tors for future inundation dynamics in the central and coastal areas of the VMD. These findings are in line with Fujihara et al. (2016), who identified sea level rise and land subsidence as the main factors controlling alteration of minimum and Table 6. Contribution of each factor to the alteration of water level between the floods 2000 and 2011 for key gauge stations in the VMD. The stations are listed from upstream to downstream and from small to large distance to the main rivers to remote. Station numbers refer to Fig. 1
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... from the Tibetan Plateau, the Mekong River runs through the territories of China, Myanmar, Laos, Thai- land, Cambodia and Vietnam before it discharges into the South China Sea (termed the East Sea in Vietnam). With a mainstream length of almost 4100 km, drainage area of about 795 000 km 2 and annual mean discharge of 475 km 3 , the Mekong is ranked 10th in the list of the world's largest rivers. The basin is subjected to a monsoonal regime, in which the wet season lasts from June to November account- ing for 80-90 % of the total annual flow. During this period a huge amount of water is routed to the lowland areas, causing extensive inundation in the MD. The MD encompasses the Cambodian floodplains (CFP) downstream of Kratie ( Fig. 1) and the VMD, which differs considerably from the CFP due its enormous amount of man-made hydraulic structures like channels, dykes, sluice gates and pumps. Although large floods, such as in 2000 or 2011, result in considerable eco- nomic and social damages (MRC, 2012(MRC, , 2015, flooding is the backbone of the agricultural production in the region. Moderate floods, commonly perceived as "good floods" by the local population, bring various benefits, e.g. reduction in soil acidity; removal of residual pesticides and other pol- lutants in paddy fields; an immense wealth of wild fish in the rivers, channels and inundated floodplains; and provision of nutrients through deposited sediments on the floodplains (Hashimoto, 2001;Sakamoto et al., 2007;Hung et al., 2012;Manh et al., 2013Manh et al., , ...
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... enters the VMD via three main routes, i.e. the mainstream flow through the Mekong River (named Tien River in Vietnam) and Bassac River (named Hau River in Vietnam), and transboundary overland flow to the Plain of Reeds (PoR) east of the Mekong River and to Long Xuyen Quadrangle (LXQ) west of the Bassac River (Fig. 1). The mainstream flow accounts for 90 % of the total flood volume entering the VMD . The flood-prone areas cover a territory of approximately 2.0 million hectares in the north- ern part of the VMD (Fig. 1). The average inundation depth varies from 0.5 to 4.0 m and lasts for 3 to 6 months (Toan, 2014;Xo et al., 2015). The floodplains are protected by ex- tensive dyke systems, both low dykes and high dykes, with a total length of over 13 000 km, of which 8000 km comprises low dykes with crest levels vary from 1.5 to 4.0 m a.s.l. High- dyke areas are mainly concentrated in the provinces An Gi- ang and Dong Thap in the upper part of the delta (green areas in Fig. 1). About 65 % of the cultivation area in An Giang and 40 % in Dong Thap are protected by high dykes with crest levels of 4.0-6.0 m a.s.l. (SIWRR, 2010). The area of triple cropping in 2014 was 175 000 ha in An Giang and 120 000 ha in Dong Thap, respectively (GSO, ...
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... enters the VMD via three main routes, i.e. the mainstream flow through the Mekong River (named Tien River in Vietnam) and Bassac River (named Hau River in Vietnam), and transboundary overland flow to the Plain of Reeds (PoR) east of the Mekong River and to Long Xuyen Quadrangle (LXQ) west of the Bassac River (Fig. 1). The mainstream flow accounts for 90 % of the total flood volume entering the VMD . The flood-prone areas cover a territory of approximately 2.0 million hectares in the north- ern part of the VMD (Fig. 1). The average inundation depth varies from 0.5 to 4.0 m and lasts for 3 to 6 months (Toan, 2014;Xo et al., 2015). The floodplains are protected by ex- tensive dyke systems, both low dykes and high dykes, with a total length of over 13 000 km, of which 8000 km comprises low dykes with crest levels vary from 1.5 to 4.0 m a.s.l. High- dyke areas are mainly concentrated in the provinces An Gi- ang and Dong Thap in the upper part of the delta (green areas in Fig. 1). About 65 % of the cultivation area in An Giang and 40 % in Dong Thap are protected by high dykes with crest levels of 4.0-6.0 m a.s.l. (SIWRR, 2010). The area of triple cropping in 2014 was 175 000 ha in An Giang and 120 000 ha in Dong Thap, respectively (GSO, ...
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... enters the VMD via three main routes, i.e. the mainstream flow through the Mekong River (named Tien River in Vietnam) and Bassac River (named Hau River in Vietnam), and transboundary overland flow to the Plain of Reeds (PoR) east of the Mekong River and to Long Xuyen Quadrangle (LXQ) west of the Bassac River (Fig. 1). The mainstream flow accounts for 90 % of the total flood volume entering the VMD . The flood-prone areas cover a territory of approximately 2.0 million hectares in the north- ern part of the VMD (Fig. 1). The average inundation depth varies from 0.5 to 4.0 m and lasts for 3 to 6 months (Toan, 2014;Xo et al., 2015). The floodplains are protected by ex- tensive dyke systems, both low dykes and high dykes, with a total length of over 13 000 km, of which 8000 km comprises low dykes with crest levels vary from 1.5 to 4.0 m a.s.l. High- dyke areas are mainly concentrated in the provinces An Gi- ang and Dong Thap in the upper part of the delta (green areas in Fig. 1). About 65 % of the cultivation area in An Giang and 40 % in Dong Thap are protected by high dykes with crest levels of 4.0-6.0 m a.s.l. (SIWRR, 2010). The area of triple cropping in 2014 was 175 000 ha in An Giang and 120 000 ha in Dong Thap, respectively (GSO, ...
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... the calibration and verification of the hydraulic model, hourly data of all VMD gauging stations ( Fig. 1 and Ta- ble S1 in the Supplement) and inundation maps derived from MODIS satellite images were used. Cloud cover of the MODIS images was removed by Kotera et al. (2014Kotera et al. ( , 2016. The calibration considered the rainy season (June to Novem- ber) of the years 2000 and ...
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... development Downstream boundary Figure 10. Contribution of each factor to the alteration of water levels between the floods 2000 and 2011 for key gauge stations in the VMD. The difference between the two scenarios S3 and S1 is considered to be 100 ...
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... data were used as boundaries for the hydraulic model, for model calibration and validation and for detection of flood trends. Daily and hourly water level and discharge data were collected at 30 stations. They include 13 stations along the rivers Mekong and Bassac, of which 6 stations are located in Cambodia, along with 10 tidal gauge stations and 7 sta- tions located in secondary rivers/canals (Fig. 1). The location and name of each station are given in Table S1 (Supplement). These data were provided by the Mekong River Commission (MRC) and the Southern Regional Hydro-Meteorology Cen- tre of Vietnam (SRHMC). The MRC database contains daily readings from 1960s to present, with some stations having data back to the 1930s. However, the data often have gaps due to the past political conflicts in the region. SRHMC data are measured in hourly intervals and are relatively complete, but cover only the period from the late 1970s to present. To obtain a common period for the trend analyses for the Viet- namese and Cambodian stations, time series of 38 years of daily water level/discharge data at five key sta- tions, i.e. Kratie, Tan Chau, Chau Doc, Can Tho and My Thuan, were chosen. These two databases use different verti- cal reference points, i.e. Hatien1960 in MRC data, and Hon- dau72 in SRHMC data. To ensure consistency, the MRC data were converted to the Hondau72 ...
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... to the three upstream locations, the two stations downstream of high-dyke areas, i.e. Can Tho and My Thuan, show significant upward trends in both AMWL and DOT. AMWL increases by 13.1 and 9.2 mm year −1 (p ≤ 0.001) at Can Tho and My Thuan, respectively. This is similar to the findings of Fujihara et al. (2016). Dang et al. (2016) anal- ysed annual mean water levels and detected a significant up- ward trend at Can Tho, but no trend in My Thuan (Fig. 6). This, at first sight, contradictory result can be explained by the different relation between annual maximum and mean water levels at the two stations. There is a strong correla- tion between maximum and mean water levels for Can Tho (r = 0.84), but only a weak correlation is seen for My Thuan (Fig. 6)
Figure 6. Strong correlation between annual maximum and mean water level at Can Tho, but no correlation at My Thuan; data from 1978 to 2015. The numbers next to the station names refer to the numbers in Fig. ...
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... the impact on AMWL and DOT at the stations Can Tho and My Thuan is almost identical to the range es- timated from the trend analysis. Applying the obtained trend slopes to the interval 2000-2011 yields an increase of 11- 15 cm for AMWL and 12-18 days for DOT. This agreement between the two independent methods enhances the credibil- ity of the results. Stations are listed from upstream to downstream and from small to large distance from main rivers; station locations are given Fig. 1 Step-change analysis including the uncertainty analysis at four stations in the VMD. Panel (a) presents results for annual maximum water level (in metres) and (b) for flood duration over thresholds (in days). Data before the change point are presented in black. The second period is presented in red for negative step change and in blue for a positive change. Dashed lines are mean values of partial datasets. Results of the uncertainty analysis are presented using the second vertical axis on the right, as the number of times that a step change occurred in a certain year at three error levels (5 %: diamond; 10 %: cross; 15 %: ...
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... comparison of the changes in AMWL and DOT in Ta- ble 5 reveals a spatial pattern: the upstream boundary has the largest impact on the stations located north of Long Xuyen and Cao Lanh, and at stations with larger distances from the main rivers. In these areas the tidal amplitude is attenuated due to the large distance from the sea and/or the length of the channel network. The situation at the stations downstream of the high-dyke areas and along the main rivers (stations Long Xuyen, Cao Lanh, Can Tho, My Thuan) is more complex. Here the changes caused by the different factors have similar magnitudes, whereas the tidal influence increases in down- stream direction. Hence, the factors can partly compensate for each other, and an attribution of observed changes to in- dividual factors requires a careful inspection. Table 6 and Fig. 10 present the contributions of the three factors in relation to the observed differences between the floods in 2000 and 2011. Apparently, the sum of the sin- gle contributions does not equal the observed differences. This is a consequence of non-linear interactions, including, for example, the problem of timing between flood peaks and tidal characteristics. The magnitude of the discrepancy varies widely between the stations from a close match to almost 50 %. Most of the stations with small discrepancies are lo- cated farthest north and farthest away from the main rivers. For those stations the upstream boundary causes changes of 120-130 % of the baseline difference. Dyke construction and, to a lesser extent, the change in the lower boundary counteract these changes. Downstream of Vam Nao the contribution of the upper boundary diminishes to only 20-50 % of the baseline dif- ference. In this region the other two factors have higher im- portance, but the relative contribution changes from station to station. With respect to the motivation of the study, i.e. the quantification of the impact of high-dyke construction on floodwater levels, this region is the most affected by the high- dyke development. This factor amounts to 65-80 % of the baseline difference. Further downstream, i.e. at Can Tho and My Thuan, the lower boundary becomes the prevailing fac- tor, amounting to more than 80 % of the baseline difference. The water level changes caused by the high-dyke system is reduced to about 30 ...
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... this section the relative impact of the three factors (i) changes in the upper boundary, (ii) high-dyke construc- tion, and (iii) changes of the lower boundary is evaluated by interchanging the upper boundary, the dyke system and the lower boundary of the model simulation for the reference years 2000 and 2011. The scenario set is given in Table 3 and the results are summarized in Table 5. The contributions of the three factors are compared to the baseline difference, which is defined as the difference in maximum water level of 2011 (scenario S3) and 2000 (scenario S1). The contribu- tions were calculated as the mean of the two scenarios for each factor. The relative contributions are presented in Ta- ble 6 and Fig. 10. Table 5 reveals that for most stations the maximum water levels and the duration over threshold lev- els decrease when as upper boundary the flood hydrograph of 2000 is replaced with the higher volume flood of 2011. Interestingly, this is not the case for Can Tho and My Thuan. These stations are located in areas where the magnitude of both river discharge and tidal water levels is important for AMWL and DOT during the annual flood events. Moreover, not only the magnitude but also the temporal coincidence of maximum floodwater levels and the spring tides is highly rel- evant. During the flood in 2000, the flood peak in Tan Chau and Chau Doc occurred on 23 September, coinciding with a neap tide period. However, the peak in 2011 occurred dur- ing the first week of October, coinciding with a spring tide period. When the upper boundaries are interchanged, this Table 5 at these two stations when the lower boundaries are interchanged. For the DOT this effect is also observable for the scenario S5-S1, but for the analogous scenario the long period of high water levels in 2000 causes higher DOT, even if the period of high water levels does not coincide with the spring tide ...
Citations
... The construction of high-dikes and sluice gates has been the conventional flood management approach in the VMD (Dung et al., 2018a;Tran and Weger, 2018;Tran et al., 2020aTran et al., , 2020bTran et al., 2021;Vu et al., 2021). These structures prevent protected areas from being flooded and thus reduce flood hazards within the protected areas; however, they divert flood hazards to non-protected, mostly downstream zones of the delta (Dung et al., 2018c;Triet et al., 2017). ...
Water management strategy for agriculture in the Vietnamese Mekong Delta (VMD) is undergoing radical changes in response to hydrological changes under the exogenous impacts of climate change, upstream developments, and in-situ water infrastructure development. There have been notable efforts in transitioning to sustainable agricultural development policies, aiming at increasing farmers’ income while protecting the environmental systems of the delta. However, realities suggest that rice famers’ livelihoods remain unstable and highly susceptible to environmental changes. In response to these challenges, farmers have decided to shift their farming practices by transforming from rice-based to more adaptive farming systems. These on-going processes of livelihood transformation raise important questions concerning how local efforts correspond to policymaking and planning toward adaptation. This chapter sheds light on the interface between state-led climate change adaptation and local dynamics of livelihood transformation and how they interact with each other. We first reviewed studies carried out in the VMD, focusing on the adaptation and adaptive capacity of farmers under climate change and environmental impacts. Then we used the data collected from our previous surveys to explore farmers’ perspectives and actions in response to environmental changes. Insights from this chapter contribute to the much-needed knowledge base about how farmers’ livelihoods and adaptive capacity can be enhanced to allow for effective climate change adaptation.
... In the last three decades, the two floodplains have been transformed into major rice production regions, accounting for 34 % of the rice production of Vietnam (GSO, 2023). A series of high dikes and flood control structures have been built to block the flood water, allowing the production of two (even three in some areas) rice crops annually Käkönen, 2008;Triet et al., 2017). Dismantling the portion of the dike system or reducing the elevation of the dike systems (e.g., from a high dike to a low dike system) can hold more and longer flood water and serve as a mitigation strategy for SWI intensity and risks in the dry season. ...
... But not all the blame can be put on the upstream actions. In the Delta itself, high dikes have been built to control floods and thus enable high-intensification agriculture in the traditional floodplain region of the Delta (Käkönen, 2008;Triet et al., 2017;Tran et al., 2019;Kondolf et al., 2022). Less water use during the dry season and/or a higher amount of water retained in the floodplain regions during the rainy season would mean more flow to the coastal region during the dry season. ...
... Less water use during the dry season and/or a higher amount of water retained in the floodplain regions during the rainy season would mean more flow to the coastal region during the dry season. Previous studies argued that maintaining the connectivity of the delta floodplain by adaptive water infrastructure (e.g., replacing high dikes with low dikes in the delta floodplain) can increase low flows of the Mekong River during the dry season substantially (Triet et al., 2017;Tran et al., 2019;Kondolf et al., 2022); thus, would be a more sustainable strategy to keep the SWI at bay (e.g., similar to the baseline). Here, we show that though soft policy alone would not be able to bring the SWI intensity and risks back to their baseline level, the policy would still reduce SWI intensity and risks substantially (Table 2). ...
The Mekong Delta is one of the most productive rice-producing regions in the world, exporting approximately one-fifth of the global rice traded annually. Previous studies note that saltwater intrusion is a serious concern, and the intensity of saltwater intrusion is primarily driven by sea level rise, land subsidence, anthropogenic sediment starvation, and upstream hydro-infrastructure developments. However, these studies often rely on scenario-based approaches instead of an integrated approach to assess the possible impacts of saltwater intrusion. Using an integrated hydrodynamic-statistical-economic model, we investigate how and the extent to which these drivers may impact the saltwater intrusion. We also examine the costs and returns of two popular saltwater intrusion control policies, i.e., hard-engineering structural and soft-land use planning. When comparing the baseline scenarios, the findings indicate that anthropogenic forces lead to a four times greater saltwater intrusion intensity than the climate change-induced sea level rise. The results further reveal a 50 % or less chance that annual saltwater-affected areas would exceed 1.93 million ha for the baseline, but the likelihood is highly likely to be 100 % with a sea level rising of 22 cm. Under the combined effects of sea-level rise, land subsidence, and riverbed incision, our model shows that the probability of annual saltwater-affected areas staying above 2.30 million ha is almost equal to one. This finding implies that a large share of the current rice-planted areas of the Delta could be wiped out of production for at least one season a year. The findings show that a combination of hard and soft policies would be a more sustainable and cost-effective strategy to lower the intensity and risks of saltwater intrusion. Therefore, there is an urgent need for better coordination of governance and investments among regions within the Delta and counties in the whole Mekong River Basin.
... These systems have considerably altered the natural hydrodynamics and sediment transport [11,12]. Recently, researchers have paid more attention to the whole domain through extensive monitoring networks [13,14] and satellite observations [7,15] and by applying 1D [16][17][18], semi/quasi 2D [19] or 1D-2D coupled flow simulation models [8,12]. Other studies concentrated on the impacts of dyke systems on hydrodynamics [20,21]. ...
... The low dyke rings, with an average crest level of about 2.0 -2.5 m a.s.l. [13], aim to protect paddy fields against the early flood peak from mid-July to mid-August so that farmers can cultivate two rice crops per year [19]. The high dyke rings were designed with an average crest level of about 4.0 -4.5 m a.s.l. ...
... The period 25 -30 October 2011 is selected to simulate the extreme flood dynamics in the VMD because the maximum water level in 2011 was higher than that of the historic flood event in 2000 [6,64]. For this event, a late flood peak (in October 2011) coincided with a spring tide period [19], which caused the highest water level observed so far in the VMD. Figure 8 shows that the water level in the upper VMD is always higher than in the downstream parts, especially in the PoR and LXQ, which are considered to be two floodprone areas of the VMD. The water level in the PoR is higher than 1.8 m, while the water level in the LXQ is higher than 1.0 m, which redistributes the flow in the VMD by discharging floodwater into the Gulf of Thailand to protect local residents and crops. ...
The Mekong Delta has the world’s third-largest surface area. It plays an indisputable role in the economy and livelihoods of Vietnam and Cambodia, with repercussions at regional and global scales. During recent decades, the Vietnamese part of the Mekong Delta underwent profound human interventions (construction of dykes and multi-channel networks), which modified the hydrodynamic regime, especially cycles of field submersion. In this study, we first applied a full 2D numerical hydraulic model, TELEMAC-2D, to examine the effects of the complex channel and river networks on the spatial and temporal distribution of the flow in the 40,000 km2 of the Vietnamese Mekong Delta. Then, two scenarios of relative sea-level rise in 2050 and 2100 were implemented to simulate the future patterns of water fluxes in the delta. The results show that dykes and multi-channel networks would reduce the inundation area by 36% and lessen the peak water level by 15% and the discharge over the floodplains by 24%. Despite this protection, under a relative sea-level rise of 30 cm and 100 cm, the maximum flooded area could occupy about 69% and 85% of the whole delta in 2050 and 2100, respectively.
... GHG emission from agriculture is more likely to increase in the province as the adverse impacts of dyke systems, e.g. environmental degradation and soil pollution, have led farmers to the overuse of nitrogen-containing fertilizers and pesticides, and higher mechanization to sustain high agricultural yields (Brown, 2016;Triet et al., 2017). The increased agricultural GHG emission has been widely reported in other Asian agricultural economies such as Bangladesh, India and China (Aryal et al., 2020;Nayak et al., 2015;Vetter et al., 2017). ...
... The dependent variables ("adoption of adaptation strategies" in this study) were binary, and their values (1 and 0) were used to distinguish between farmers who have adopted a certain adaptation strategies, such as polyculture and innovative irrigation, and those who have not innovated in research site. (Pokhrel et al., 2018;Quang & Borton, 2020;Triet et al., 2017). Accordingly, the results signify that farmers' perception of climate change is consistent with data and province's observed climate records (Figures 2 and 3). ...
Globally, agriculture is both a victim and contributor to anthropogenic global warming. While farmers’ climate change perception generally increases, a low-carbon agricultural transition is not always an easy choice. There are numerous studies looking at the constraints hampering farmers’ adoption of adaptation strategies in climate-prone areas worldwide. The extent to which their assertion applies to farmers in carbon-intensive agricultural areas with less experience of climate change effects, however, is not clear and cannot be assumed given the shared social and cultural specificities of the farming population. This paper seeks to address this gap by scrutinizing critical determinants of farmers’ adaptation action in agriculturally rich An Giang province, where climate change impacts are generally less evident. Intense crop cultivation in the province involves the liberal use of fertilizers, crop-residue burning, frequent tilling, and other harmful farming practices that release carbon. Primary data were collected through household surveys (n = 133), field observation, and in-depth interviews (n = 24). A chi-square (χ2) test and a binary logistic regression model was used to analyze the factors influencing farmers’ adaptation decisions. The results indicated that farmers’ adaptation intent and decisions in the research area were significantly determined by market accessibility, uncertainty/instability of existing crops, and extreme weather conditions. These findings shed new light on approaches that are likely to motivate or hamper farmers’ climate-friendly transition in carbon-intensive agricultural hubs. We suggest that adaptive farming initiatives that have the potential to improve marketability and sustainability should be a starting point for mobilizing farmers for a low-carbon farming transition.
... Under the French colonization of Vietnam, canals were excavated and land drained for increased cultivation. From the 1990s onwards, the government developed extensive flood management works (Hoa et al., 2008;Triet et al., 2017). Currently, hydrological engineering works in the VMD include over 100,000 km of canals, more than 14,000 km of high and low dykes, and numerous sluice gates. ...
Sinking and shrinking, the Vietnamese Mekong Delta is a materialization of dynamic river flows, sediment flows, and coastline processes. Past policy aspirations and extensive water infrastructures have shaped the delta into one the most significant food producing landscapes in Southeast Asia. Yet, these changes have also created new environmental risks by transforming the hydrological system. Research has produced a growing and increasingly diverse empirical literature on the delta's environmental context, without necessarily providing water resource managers, policymakers and practitioners with the information needed to galvanize more resilient development. This focus review presents a detailed overview of the recent scientific findings, exploring how the management of water resources is changing, as well as their inter‐relationship with land use, policy, socio‐economic transitions, and global environmental crises. Compound and systemic risks to the delta include climate change, hydrometeorological hazards, upstream developments and an unsustainable development trajectory. We outline scientific knowledge gaps, as well as the pressing need for sharable analysis‐ready data and innovations. Finally, we provide recommended future research avenues for multiscale actions toward a sustainable and resilient delta future.
This article is categorized under: Human Water > Water Governance
Science of Water > Water Extremes
Science of Water > Water and Environmental Change
... As a result, the low dyke systems (semi-dyke systems) were built in An Giang Province, which helped to prevent the early flood peak from arriving around mid-July to mid-August. Thus, farmers were able to produce double rice crops per year (Nguyen et al. 2017a). However, after the disastrous flood in 2000, the majority of the low dyke systems were upgraded into high dyke systems, which are termed the FD systems (Kontgis et al. 2015). ...
... Initially, the FD system demonstrated many positive effects on livelihoods and agricultural production, such as increasing safety in farming and additional profits for the farmers (Nguyen et al. 2017a(Nguyen et al. , 2018. However, the negative impacts of the FD system in the long term have been increasingly acknowledged, including (1) restraining water exchange between inside and outside; ...
The dyke system plays a vital role in cultivating rice intensively in the Vietnamese Mekong Delta, which protects rice paddy fields from annual floods. This study aimed to examine whether the full-dyke system (FD, which restricts water exchange for a long time) can cause degradation of surface water quality and reduction in benthic invertebrate biodiversity. The surface water quality and benthic invertebrate community were compared between the FD and semi-dyke systems (SD, which permits water exchange during flooding season) using a large number of samples collected seasonally in 2019. The results showed that the surface water quality within the FD system had significantly higher concentrations of TSS, COD, BOD5, N-NO3⁻, N-TKN, P-PO4³⁻, and TP than compared to the SD system (p < 0.05), indicating greater pollution levels. The benthic invertebrate community was less diverse in the FD system than in the SD system. Only 17 species (belonging to 4 families) were detected in the FD system, and 30 species (belonging to 5 families) were detected in the SD system. The benthic invertebrate community structure changes and biodiversity loss were associated with degraded water quality. The P-PO4³⁻ and TP parameters were negatively correlated with the number of species, density, and biomass in the FD system and with the Shannon–Wiener (H′) index in the SD system. In conclusion, the FD system has been degrading water quality and causing biodiversity loss.
... These models are used to simulate floods during the period in which the event occurs and to describe its progress over time, where only the hydraulic aspects of the event take place. Some authors suggest that the depth and maximum extent of water flow in a flood event are enough for hazard assessment (Triet et al. 2017;Bulti and Abebe 2020;Ongdas et al. 2020;Elkhrachy et al. 2021) but others studies claim that the flow velocity must be modelled for flood damage assessment (Kadam and Sen 2012;Neal et al. 2012;Falter et al. 2013;Iroume et al. 2022). ...
Floods are one of the most frequent, dangerous natural disasters globally. During the period from 1990 to 2020, more than 50% of the world's recorded disasters were related to floods. This problem stems largely from the inadequate planning and economic circumstances of human settlements in flood-prone plains. Geospatial modelling can be a powerful tool for large-scale flood modelling. The hydrological and hydraulic models theory, GIS-based multi-criteria evaluation techniques, and machine learning algorithms for flood simulation are presented. The most used techniques and methodologies for the geospatial simulation of floods in the last decade are presented. This paper also shows the input data requirements and the algorithms used for each geospatial technique and a description of the tools and some relevant examples of geospatial flood studies are given. A comprehensive assessment of the characteristics of the flood models is presented based on its modelling approach, either for flood susceptibility, hazard, vulnerability, or risk.
... A fuller exploitation of land and water resources for agricultural development in the VMD has fueled the rapid growth of rice production [8]. However, unexpected environmental impacts have also increasingly emerged, such as riverbank erosion, new inundation areas downstream, water pollution, and land degradation [3,6,9,10]. These effects, combined with the impacts of climate change, sea level rise, and the construction of hydropower dams and reservoirs upstream, have raised increasing concern, particularly regarding the disappearance of the flood season, the growing severity of salinity intrusion, and the droughts, which have become increasingly frequent in the VMD [11][12][13][14]. ...
There is an implementation gap between government plans and land-use changes at the local level in the Vietnamese Mekong Delta. This stands in the way of the sustainable development of the delta, especially in the face of environmental degradation, climate change, and water-use conflicts. To narrow the gap between plans and practice, the government needs a better understanding of what drives land-use decisions at the farm level. Our research developed and applied a multi-scale framework to identify the principal drivers of land-use changes at the farm level in the Vietnamese Mekong Delta over the past 40 years. We conducted semi-structured interviews with 31 farmers in the highly flooded zone, then used transcript analysis to quantify the influence of the drivers mentioned by farmers. We found drastic shifts in land uses, predominantly towards rice intensification. Among the 43 change drivers the farmers mentioned, those operating at the regional scale were particularly influential, including the activities of local authorities, neighborhood effects, and the development of water management infrastructure. Market factors have become more prominent in the last two decades, motivating farmers to shift from double to triple rice or to gradually diversify into vegetables. However, agricultural diversification remains limited by the agro-hydrological context, which favors triple rice cropping, as well as household scale factors such as natural and physical assets of the farm, household capital, and labor capacity. The local community also played a key role in land-use change, though with a double-edged effect, both delaying implementation of central government policy and forcing farmers to follow the majority’s decision.
... To ensure the accuracy of the MIKE11 model, calibration and validation simulations were conducted for the two extreme dry seasons of 2016 and 2020, respectively. The goodnessof-fit checks between simulated data and observed data were performed using the Nash-Sutcliffe efficiency (NSE) and correlation coefficient (R 2 ), which are common criteria used to evaluate model performance [37,60,61]. The NSE values ranged from 0.9 to 1, with values close to 1 indicating optimal performance, while negative values indicate inadequate performance. ...
This scientific paper delves into sustainable water management strategies for Ben Tre Province of the Vietnamese Mekong Delta (VMD) in light of water-infrastructure plans that have been impacted by climate change-induced salinity intrusion. Specifically, we aim to mitigate the effects of salinity intrusion for the province while promoting long-term environmental sustainability. In doing so, a water accounting framework was applied, mostly based on the MIKE11 hydrodynamic modeling and water balance calculations, to determine current and future water stress issues based on two main scenarios of extreme drought year 2016 (baseline) and the future year 2030 under climate change for a medium-low emission scenario (RCP4.5). The study found that salinity intrusion significantly causes severe water stress in the future year 2030 compared to the baseline year 2016, while the existing water management methods are relatively inadequate to control salinity intrusion, leading to over 57% of the area affected by medium to critical water stress levels, although it will go along with planned water infrastructures. Additionally, a system of triple rice cropping converted two rice cropping and upland cropping with 40% water demand cutoff was found to be the most suitable measure for 2030. Particularly, water-saving and water demand reduction should be incorporated into infrastructural planning for sustainable water management. Our study provides valuable insights for policymakers and stakeholders, not only for the province and the VMD, but also other regions facing similar challenges.
... The orange cluster includes Australia, Germany, Indonesia, Italy, Netherlands, Russia, and the UK. It is the largest cluster and includes the themes relative to the risks related to subsidence [103], like flooding [104,105], but also to the main causes such as sea level rise [106,107] and climate change. Studies in Canada, China, Iran, Mexico, Taiwan, and Thailand (red cluster) are mainly related to hydrogeology [108][109][110], with a lesser extent to mitigation measures related to the exploitation from the subsoil [83,[111][112][113]. ...
Land subsidence (LS) is becoming one of the major problems in coastal and delta cities worldwide. Understanding the current LS situation and the research trends is of paramount importance for further studies and addressing future international research networks. We analyzed the LS-related literature available from the Scopus database. The use of a single database avoided the redundancy of articles, while excluding some subject areas was useful to obtain only studies related to LS. By using VOSviewer and CiteSpace tools, we conducted a bibliometric analysis by considering title, keywords, and abstract to identify the temporal development, the geographical origin, and the area of study of the research. The results revealed a considerable heterogeneity of approaches, thematics, study areas, and research output trends. China, the US, and Italy are the major contributors to the scientific production, but the higher number of articles is not always related to the extension of the LS phenomenon in these countries. The monitoring approach differs worldwide, and univocal modeling is still lacking; from the analysis of the keywords, it is clear that the focus of most studies is on the relationship with the hydrological/hydrogeological aspects. Since the 2000s, however, the development of SAR technologies has boosted the study of the phenomenon from a different point of view.
