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Sample records for mekong delta vietnam

  1. The spatial distribution of vulnerability to the health impacts of flooding in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Phung, Dung; Rutherford, Shannon; Dwirahmadi, Febi; Chu, Cordia; Do, Cuong Manh; Nguyen, Thuy; Duong, Nam Chi

    2015-10-01

    Flooding causes significant public health issues. The Mekong Delta has been considered the region to be the most vulnerable to flooding in Vietnam. This study assessed the spatial vulnerability of the health impacts of flooding in the Mekong Delta region, Vietnam. This study applied a vulnerability assessment framework which was computed as the function of three dimensions: exposure, sensitivity, and adaptive capacity. The indicators for each dimension were derived from the relevant literature, consultations with experts, and data availability. An analytic hierarchy process (AHP) and a principal component analysis (PCA) were used to determine the weight of indicators. Vulnerability indexes (VIs) were then computed for each province. A total of 29 indicators (sensitivity index, 14; adaptive capacity index, 13; and exposure index, 2) were employed to evaluate the vulnerability to the health impacts of flooding at a provincial level. The results of AHP revealed that the highest VIs were found in the Dong Thap and An Giang provinces (VI, 1.948 and 1.574, respectively). VIs were distributed with higher indexes in upstream provinces close to a river than in coastal provinces. PCA generated three components from the 29 indicators, and the VIs computed from the PCA method are in substantial agreement with the AHP method (ICC = 0.71, p < 0.05). The vulnerability to the health impacts of flooding varies from province to province in the Mekong Delta region in Vietnam. Individual plans for health preparedness and adaption to flooding should be developed for each province in the Mekong Delta region.

  2. The spatial distribution of vulnerability to the health impacts of flooding in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Phung, Dung; Rutherford, Shannon; Dwirahmadi, Febi; Chu, Cordia; Do, Cuong Manh; Nguyen, Thuy; Duong, Nam Chi

    2016-06-01

    Flooding causes significant public health issues. The Mekong Delta has been considered the region to be the most vulnerable to flooding in Vietnam. This study assessed the spatial vulnerability of the health impacts of flooding in the Mekong Delta region, Vietnam. This study applied a vulnerability assessment framework which was computed as the function of three dimensions: exposure, sensitivity, and adaptive capacity. The indicators for each dimension were derived from the relevant literature, consultations with experts, and data availability. An analytic hierarchy process (AHP) and a principal component analysis (PCA) were used to determine the weight of indicators. Vulnerability indexes (VIs) were then computed for each province. A total of 29 indicators (sensitivity index, 14; adaptive capacity index, 13; and exposure index, 2) were employed to evaluate the vulnerability to the health impacts of flooding at a provincial level. The results of AHP revealed that the highest VIs were found in the Dong Thap and An Giang provinces (VI, 1.948 and 1.574, respectively). VIs were distributed with higher indexes in upstream provinces close to a river than in coastal provinces. PCA generated three components from the 29 indicators, and the VIs computed from the PCA method are in substantial agreement with the AHP method (ICC = 0.71, p < 0.05). The vulnerability to the health impacts of flooding varies from province to province in the Mekong Delta region in Vietnam. Individual plans for health preparedness and adaption to flooding should be developed for each province in the Mekong Delta region.

  3. Assessing the prehistoric shoreline changes of the Mekong delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Tamura, T.; Saito, Y.; Nguyen, V. L.; Ta, T. K. O.; Bateman, M. D.; Sato, A.

    2014-12-01

    The environment and sustainability of deltaic lowlands have been threatened by combined impacts of climate changes, human activities and land subsidence. The Mekong delta has also been disturbed by the construction of upstream river dams and fluvial dredging, and we have a limited knowledge of its morphodynamics response to fluctuations in Asian monsoons that governs the coastal sediment dynamics. In order to understand the recent shoreline changes of the Mekong delta, we attempted to reconstruct the prehistoric changes based on landform records and their chronology. Thirteen optically-stimulated luminescence (OSL) ages of chenier, a record of past shoreline, were obtained from the Soc Trang coastal plain, southwestern part of the delta. The OSL ages are younger than 2770 yr BP, and become younger seawards concordantly with the coastal progradation that cheniers document. The progradation rate has changed drastically; it was 8 m/yr, 31 m/yr, and 5 m/yr during periods of 2770-1370 yr BP, 1370-590 yr BP, and 590 yr BP to present, respectively. The rapid progradation during 1370-590 yr BP did not form cheniers, resulting in an extensive inter-ridge swale. Cheniers generally form in relations to erosion of muddy coast. The chenier distribution and drastic changes in progradation rate were resulted from fluctuations in relative importance of longshore sediment removal to seaward sediment accretion. Beach ridges in the Tra Vinh coastal plain, northeast of the Soc Trang, also indicate similar and synchronous fluctuations in the longshore sediment transport. The dominance of the longshore sediment transport after 590 yr BP is thought caused by the strengthened winter monsoon that drives the southwestward longshore current, which is possibly related to the beginning of the Little Ice Age. Many cheniers occur along the present shoreline in relation to the low progradation rate, and possibly some sporadic erosion after 590 yr BP. Some evidences have suggested that the winter

  4. The spatial distribution of vulnerability to the health impacts of flooding in the Mekong Delta, Vietnam.

    PubMed

    Phung, Dung; Rutherford, Shannon; Dwirahmadi, Febi; Chu, Cordia; Do, Cuong Manh; Nguyen, Thuy; Duong, Nam Chi

    2016-06-01

    Flooding causes significant public health issues. The Mekong Delta has been considered the region to be the most vulnerable to flooding in Vietnam. This study assessed the spatial vulnerability of the health impacts of flooding in the Mekong Delta region, Vietnam. This study applied a vulnerability assessment framework which was computed as the function of three dimensions: exposure, sensitivity, and adaptive capacity. The indicators for each dimension were derived from the relevant literature, consultations with experts, and data availability. An analytic hierarchy process (AHP) and a principal component analysis (PCA) were used to determine the weight of indicators. Vulnerability indexes (VIs) were then computed for each province. A total of 29 indicators (sensitivity index, 14; adaptive capacity index, 13; and exposure index, 2) were employed to evaluate the vulnerability to the health impacts of flooding at a provincial level. The results of AHP revealed that the highest VIs were found in the Dong Thap and An Giang provinces (VI, 1.948 and 1.574, respectively). VIs were distributed with higher indexes in upstream provinces close to a river than in coastal provinces. PCA generated three components from the 29 indicators, and the VIs computed from the PCA method are in substantial agreement with the AHP method (ICC = 0.71, p < 0.05). The vulnerability to the health impacts of flooding varies from province to province in the Mekong Delta region in Vietnam. Individual plans for health preparedness and adaption to flooding should be developed for each province in the Mekong Delta region. PMID:26506930

  5. Development of sea level rise scenarios for climate change assessments of the Mekong Delta, Vietnam

    USGS Publications Warehouse

    Doyle, Thomas W.; Day, Richard H.; Michot, Thomas C.

    2010-01-01

    Rising sea level poses critical ecological and economical consequences for the low-lying megadeltas of the world where dependent populations and agriculture are at risk. The Mekong Delta of Vietnam is one of many deltas that are especially vulnerable because much of the land surface is below mean sea level and because there is a lack of coastal barrier protection. Food security related to rice and shrimp farming in the Mekong Delta is currently under threat from saltwater intrusion, relative sea level rise, and storm surge potential. Understanding the degree of potential change in sea level under climate change is needed to undertake regional assessments of potential impacts and to formulate adaptation strategies. This report provides constructed time series of potential sea level rise scenarios for the Mekong Delta region by incorporating (1) aspects of observed intra- and inter-annual sea level variability from tide records and (2) projected estimates for different rates of regional subsidence and accelerated eustacy through the year 2100 corresponding with the Intergovernmental Panel on Climate Change (IPCC) climate models and emission scenarios.

  6. Exploring the climate change concerns of striped catfish producers in the Mekong Delta, Vietnam.

    PubMed

    Nguyen, Anh Lam; Truong, Minh Hoang; Verreth, Johan Aj; Leemans, Rik; Bosma, Roel H; De Silva, Sena S

    2015-01-01

    This study investigated the perceptions on and adaptations to climate change impacts of 235 pangasius farmers in the Mekong Delta, Vietnam. Data were collected using semi-structured household surveys in six provinces, from three regions along the Mekong river branches. A Chi-Square test was used to determine the association between variables, and a logit regression model was employed to identify factors correlated with farmer's perception and adaptation. Less than half of respondents were concerned about climate change and sought suitable adaptation measures to alleviate its impacts. Improving information on climate change and introducing early warning systems could improve the adaptive capacity of pangasius farmers, in particularly for those farmers, who were not concerned yet. Farmers relied strongly on technical support from government agencies, but farmers in the coastal provinces did not express the need for training by these institutions. This contrasting result requires further assessment of the effectiveness of adaptation measures such as breeding salinity tolerant pangasius. PMID:25674502

  7. Gravity Anomalies and Depths of Sedimentary of Mekong Delta Area, South of Vietnam

    NASA Astrophysics Data System (ADS)

    Dang Van, L.

    2014-12-01

    The Mekong Delta is the region in the south of Vietnam with the total area of about 40.000 km2 and almost of this area is covered by water. Gravity measurement of this area was performed by Cuu Long Petroleum Agency (Vietnam) in 1980's and the Bouguer anomaly map of this area at the scale of 1/500.000 was established.We used the Bouguer anomaly map to study the geological structure of this area. This paper is divided into two parts. Firstly, we split the Mekong Delta area into two basins (CanTho-DongThap and TraCu basins) and two swells (Saigon and SocTrang swells) and delineated their boundaries by using the characteristics of Bouguer anomalies. Secondly, we used the second polynomial formula to separate the Bouger anomaly map into the regional and residual gravity anomaly maps. With this residual anomaly map, the 3D basemenf of Cenozoic-Mesozoic sediments of this area was computed by using the Parker-Oldenburg method.

  8. Climate Change Impact On Mekong Delta of Vietnam in recent years

    NASA Astrophysics Data System (ADS)

    Le, L. T. X., III

    2015-12-01

    In recent years, the climate change signal increase globally. Abnormal changes of weather tends increasingly detrimental to human life, such as natural disasters occur with increasing level of more severe. Climate change is one the biggest challenges, and is a potential threat to humans. The impact of climate change increases the number and extent of the disaster fierce exists as typhoons, floods, droughts ... Global warming and sea level rise increases the area of flooding, saline intrusion and erosion in the delta region may cause farmers to lose the opportunity to produce, source of life their only. Impact of climate change on people in the community, but poor farmers in the developing countries like our country, women are the most severe consequences In this section, we summarize changes in climate on the territory of Vietnam, especially in Mekong Delta evaluate causes and its relationship to changes in global climate and region. Along with the analysis of characteristics of climate changes over time and through space to help the evolution of the standard deviation (average deviation from the standard of the period from 1971 to 2015) may indicate that the characteristic gas scenes took place related to global climate change ... Vietnam's territory stretches over approximately 15 latitude, the terrain is very complex, located in the interior full of tropical Southeast Asia. Vietnam climate strongly influenced by the Asian monsoon, monsoon and Northern Hemisphere especially the ENSO activity in the equatorial region and the Pacific Ocean. Climate Vietnam abundant and diversified, with strong ties to the region and globally.

  9. A Proposed Biology Teacher Training Program for Secondary School Teachers in the Mekong Delta Region of Vietnam.

    ERIC Educational Resources Information Center

    Phung, Thi Nguyet Hong

    This study was undertaken to design a biology training program for secondary school teachers in the Mekong Delta region of Vietnam. The methods reported in this study included an analysis of the current biology training programs with reference to a set of biology objectives developed in the 1970 curriculum revision. Second, modern developments in…

  10. Temporal and spatial patterns of diarrhoea in the Mekong Delta area, Vietnam.

    PubMed

    Phung, D; Huang, C; Rutherford, S; Chu, C; Wang, X; Nguyen, M; Nguyen, N H; Do, C M; Nguyen, T H

    2015-12-01

    This study examined the temporal and spatial patterns of diarrhoea in relation to hydro-meteorological factors in the Mekong Delta area in Vietnam. A time-series design was applied to examine the temporal pattern of the climate-diarrhoea relationship using Poisson regression models. Spatial analysis was applied to examine the spatial clusters of diarrhoea using Global Moran's I and local indicators of spatial autocorrelation (LISA). The temporal pattern showed that the highest peak of diarrhoea was from weeks 30-42 corresponding to August-October annually. A 1 cm increase in river water level at a lag of 1 week was associated with a small [0·07%, 95% confidence interval (CI) 0·01-0·1] increase in the diarrhoeal rate. A 1 °C increase in temperature at lag of 2 and 4 weeks was associated with a 1·5% (95% CI 0·3-2·7) and 1·1% (95% CI 0·1-2·3) increase in diarrhoeal risk, respectively. Relative humidity and diarrhoeal risk were in nonlinear relationship. The spatial analysis showed significant clustering of diarrhoea, and the LISA map shows three multi-centred diarrhoeal clusters and three single-centred clusters in the research location. The findings suggest that climatic conditions projected to be associated with climate change have important implication for human health impact in the Mekong Delta region. PMID:25876699

  11. Clonal Occurrence of Salmonella Weltevreden in Cultured Shrimp in the Mekong Delta, Vietnam

    PubMed Central

    Noor Uddin, Gazi Md.; Larsen, Marianne Halberg; Barco, Lisa; Minh Phu, Tran; Dalsgaard, Anders

    2015-01-01

    This study investigated the occurrence, serovar and antimicrobial resistance of Salmonella spp. in shrimp samples from intensive and extensive farms located in three different provinces in the Mekong Delta, Vietnam. Shrimp from 11 of the 48 farms all contained S. Weltevreden, except for one farm yielding S. Agona, with no difference in Salmonella occurrence between the two production systems. Pulsed field gel electrophoresis (PFGE) of S. Weltevreden showed closely related XbaI pulse types, suggesting a clonal relationship despite the farms and shrimp samples being epidemiologically unrelated. S. Weltevreden was susceptible to most antimicrobials tested, with a few strains being resistant to florfenicol, chloramphenicol, sulfamethoxazole or trimethoprim. Future studies of the ecology of S. Weltevreden should establish if this serovar may survive better and even multiply in warm-water shrimp farm environments compared to other Salmonella serovars. PMID:26222547

  12. Hydrogeologic reconnaissance of the Mekong Delta in South Vietnam and Cambodia

    USGS Publications Warehouse

    Anderson, Henry R.

    1978-01-01

    The present report describes the results of a hydrogeologic reconnaissance in the Mekong Delta region by the writer, a hydrogeologist of the U.S. Geological Survey, while on assignment as an adviser to the Vietnamese Directorate of Water Supply from October 1968 to April 1970 under the auspices of the U.s. Agency for International Development. The delta of the Mekong River, comprising an area of about 70,000 square kilometres in South Vietnam and Cambodia, is an almost featureless plain rising gradually from sea level to about 5 metres above sea level at its apex 300 kilometres inland. Most of the shallow ground water in the Holocene Alluvium of the delta in Vietnam is brackish or saline down to depths of 50 to 100 metres. Moreover, in the Dong Thap Mu?oi (Plain of Reeds) the shallow ground water is alum-bearing. Locally, however, perched bodies of fresh ground water occur in ancient beach and dune ridges and are tapped by shallow dug wells or pits for village and domestic water supply. The Old Alluvium beneath the lower delta contains freshwater in some areas, notably in the Ca Mau Peninsula and adjacent areas, in the viciniy of Bau Xau near Saigon, and in the Tinh Long An area. Elsewhere in the lower delta both the Holocene and Old Alluvium may contain brackish or saline water from the land surface to depths of as much as 568 metres, as for example in Tinh Vinh Binh. Ground water in the outcrop area of Old Alluvium northwest of Saigon is generally fresh and potable, but high iron and low pH are locally troublesome. Although considerable exploratory drilling for ground water down to depths of as much as 568 metres has already been completed, large areas of the delta remain yet to be explored before full development of the ground-water potential can be realized. With careful development and controlled management to avoid saltwater contamination, however, it is estimated that freshwater aquifers could provide approximately 80 percent of existing needs for village

  13. An epidemiological investigation of Campylobacter in pig and poultry farms in the Mekong delta of Vietnam.

    PubMed

    Carrique-Mas, J J; Bryant, J E; Cuong, N V; Hoang, N V M; Campbell, J; Hoang, N V; Dung, T T N; Duy, D T; Hoa, N T; Thompson, C; Hien, V V; Phat, V V; Farrar, J; Baker, S

    2014-07-01

    Campylobacter are zoonotic pathogens commonly associated with gastroenteritis. To assess the relevance of Campylobacter in Vietnam, an economically transitioning country in SE Asia, we conducted a survey of 343 pig and poultry farms in the Mekong delta, a region characterized by mixed species farming with limited biosecurity. The animal-level prevalence of Campylobacter was 31·9%, 23·9% and 53·7% for chickens, ducks and pigs, respectively. C. jejuni was predominant in all three host species, with the highest prevalence in pigs in high-density production areas. Campylobacter isolates demonstrated high levels of antimicrobial resistance (21% and 100% resistance against ciprofloxacin and erythromycin, respectively). Multilocus sequence type genotyping showed a high level of genetic diversity within C. jejuni, and predicted C. coli inter-species transmission. We suggest that on-going intensification of animal production systems, limited biosecurity, and increased urbanization in Vietnam is likely to result in Campylobacter becoming an increasingly significant cause of human diarrhoeal infections in coming years. PMID:24067502

  14. Mosquitoes and their potential predators in rice agroecosystems of the Mekong Delta, southern Vietnam.

    PubMed

    Ohba, Shin-Ya; Huynh, T T Trang; Le, Loan Luu; Ngoc, Huu Tran; Hoang, San Le; Takagi, Masahiro

    2011-12-01

    Culex tritaeniorhynchus, Cx. gelidus, and Cx. quinquefasciatus, known vectors of Japanese encephalitis (JE), are distributed in rice agroecosystems in Asian countries. Very few integrated studies on the breeding habitats of rice-field mosquitoes, including JE vectors, have been conducted in Vietnam. We investigated the mosquito fauna and potential predators in 8 rice growing areas in the Mekong Delta region of southern Vietnam, during the wet and dry seasons of 2009. Mosquitoes and their predators were collected from a variety of aquatic habitats (rice fields, ponds, wetlands, shrimp ponds, ditches, canals, and rivers). We collected 936 Culex spp. (354 Cx. tritaeniorhynchus, 240 Cx. vishnui s.l., 189 Cx. fuscocephala, and 42 Cx. gelidus), 33 Uranotaenia, 25 Anopheles, and 9 Mimomyia (4 Mi. chamberlaini) in the dry season. During the rainy season, we collected 1,232 Culex spp. (132 Cx. vishnui s.l., 66 Cx. tritaeniorhynchus, 9 Cx. gelidus, 4 Cx. fuscocephala, and 2 Cx. bitaeniorhynchus), 236 Anopheles spp. (40 An. vagus and 1 An. sinensis), and 7 Uranotaenia (3 Ur. lateralis). Heteroptera such as Micronecta, Veliidae, and Pleidae were abundant and widely distributed in both seasons. Based on a stepwise generalized linear model, the abundance of mosquitoes and their predators in rice fields was high when the rice plant length was short and water depth was shallow. Therefore, the use of insecticides during the earlier stages of rice growth should be avoided in order to preserve the predator populations. PMID:22329270

  15. How Important Are Rats As Vectors of Leptospirosis in the Mekong Delta of Vietnam?

    PubMed Central

    Loan, Hoang Kim; Van Cuong, Nguyen; Takhampunya, Ratree; Kiet, Bach Tuan; Campbell, James; Them, Lac Ngoc; Bryant, Juliet E.; Tippayachai, Bousaraporn; Van Hoang, Nguyen; Morand, Serge; Hien, Vo Be

    2015-01-01

    Abstract Leptospirosis is a zoonosis known to be endemic in the Mekong Delta of Vietnam, even though clinical reports are uncommon. We investigated leptospira infection in rats purchased in food markets during the rainy season (October) (n=150), as well as those trapped during the dry season (February–March) (n=125) in the region using RT-PCR for the lipL32 gene, confirmed by 16S rRNA, as well as by the microscopic agglutination test (MAT). Results were compared with the serovar distribution of human cases referred from Ho Chi Minh City hospitals (2004–2012) confirmed by MAT (n=45). The MAT seroprevalence among rats was 18.3%. The highest MAT seroprevalence corresponded, in decreasing order, to: Rattus norvegicus (33.0%), Bandicota indica (26.5%), Rattus tanezumi (24.6%), Rattus exulans (14.3%), and Rattus argentiventer (7.1%). The most prevalent serovars were, in descending order: Javanica (4.6% rats), Lousiana (4.2%), Copenageni (4.2%), Cynopterie (3.7%), Pomona (2.9%), and Icterohaemorrhagiae (2.5%). A total of 16 rats (5.8%) tested positive by RT-PCR. Overall, larger rats tended to have a higher prevalence of detection. There was considerable agreement between MAT and PCR (kappa=0.28 [0.07–0.49]), although significantly more rats were positive by MAT (McNemar 29.9 (p<0.001). MAT prevalence was higher among rats during the rainy season compared with rats in the dry season. There are no current available data on leptospira serovars in humans in the Mekong Delta, although existing studies suggest limited overlapping between human and rat serovars. Further studies should take into account a wider range of potential reservoirs (i.e., dogs, pigs) as well as perform geographically linked co-sampling of humans and animals to establish the main sources of leptospirosis in the region. PMID:25629781

  16. Occurrence and Dissipation of the Antibiotics Sulfamethoxazole, Sulfadiazine, Trimethoprim, and Enrofloxacin in the Mekong Delta, Vietnam

    PubMed Central

    Nguyen Dang Giang, Chau; Sebesvari, Zita; Renaud, Fabrice; Rosendahl, Ingrid; Hoang Minh, Quang; Amelung, Wulf

    2015-01-01

    The Mekong Delta in Vietnam has seen a rapid development and intensification of aquaculture in the last decades, with a corresponding widespread use of antibiotics. This study provides information on current antibiotic use in freshwater aquaculture, as well as on resulting antibiotic concentrations in the aquatic environment of the Mekong Delta. Two major production steps, fish hatcheries and mature fish cultivation, were surveyed (50 fish farm interviews) for antibiotic use. Different water sources, including surface water, groundwater and piped water (164 water samples) were systematically screened for antibiotic residues. To better understand antibiotic fate under tropical conditions, the dissipation behavior of selected antibiotics in the aquatic environment was investigated for the first time in mesocosm experiments. None of the investigated antibiotics were detected in groundwater and piped water samples. Surface water, which is still often used for drinking and domestic purposes by local populations, contained median concentrations of 21 ng L-1 sulfamethoxazole (SMX), 4 ng L-1 sulfadiazine (SDZ), 17 ng L-1 trimethoprim (TRIM), and 12 ng L-1 enrofloxacin (ENRO). These concentrations were lower than the predicted no effect concentrations (PNECs) and minimum inhibitory concentrations (MICs), suggesting limited antibiotic-related risk to aquatic ecosystems in the monitored systems. The dissipation half-lives of the studied antibiotics ranged from <1 to 44 days, depending on the availability of sunlight and sediment. Among the studied antibiotics TRIM was the most persistent in water systems. TRIM was not susceptible to photodegradation, while the dissipation of ENRO and SDZ was influenced by photolysis. The recorded dissipation models gave good predictions of the occurrence and concentrations of TRIM, ENRO and SDZ in surface water. In summary, the currently measured concentrations of the investigated antibiotics are unlikely to cause immediate risks to the

  17. How important are rats as vectors of leptospirosis in the Mekong Delta of Vietnam?

    PubMed

    Loan, Hoang Kim; Van Cuong, Nguyen; Takhampunya, Ratree; Kiet, Bach Tuan; Campbell, James; Them, Lac Ngoc; Bryant, Juliet E; Tippayachai, Bousaraporn; Van Hoang, Nguyen; Morand, Serge; Hien, Vo Be; Carrique-Mas, Juan J

    2015-01-01

    Leptospirosis is a zoonosis known to be endemic in the Mekong Delta of Vietnam, even though clinical reports are uncommon. We investigated leptospira infection in rats purchased in food markets during the rainy season (October) (n=150), as well as those trapped during the dry season (February-March) (n=125) in the region using RT-PCR for the lipL32 gene, confirmed by 16S rRNA, as well as by the microscopic agglutination test (MAT). Results were compared with the serovar distribution of human cases referred from Ho Chi Minh City hospitals (2004-2012) confirmed by MAT (n=45). The MAT seroprevalence among rats was 18.3%. The highest MAT seroprevalence corresponded, in decreasing order, to: Rattus norvegicus (33.0%), Bandicota indica (26.5%), Rattus tanezumi (24.6%), Rattus exulans (14.3%), and Rattus argentiventer (7.1%). The most prevalent serovars were, in descending order: Javanica (4.6% rats), Lousiana (4.2%), Copenageni (4.2%), Cynopterie (3.7%), Pomona (2.9%), and Icterohaemorrhagiae (2.5%). A total of 16 rats (5.8%) tested positive by RT-PCR. Overall, larger rats tended to have a higher prevalence of detection. There was considerable agreement between MAT and PCR (kappa=0.28 [0.07-0.49]), although significantly more rats were positive by MAT (McNemar 29.9 (p<0.001). MAT prevalence was higher among rats during the rainy season compared with rats in the dry season. There are no current available data on leptospira serovars in humans in the Mekong Delta, although existing studies suggest limited overlapping between human and rat serovars. Further studies should take into account a wider range of potential reservoirs (i.e., dogs, pigs) as well as perform geographically linked co-sampling of humans and animals to establish the main sources of leptospirosis in the region. PMID:25629781

  18. Occurrence and Dissipation of the Antibiotics Sulfamethoxazole, Sulfadiazine, Trimethoprim, and Enrofloxacin in the Mekong Delta, Vietnam.

    PubMed

    Nguyen Dang Giang, Chau; Sebesvari, Zita; Renaud, Fabrice; Rosendahl, Ingrid; Hoang Minh, Quang; Amelung, Wulf

    2015-01-01

    The Mekong Delta in Vietnam has seen a rapid development and intensification of aquaculture in the last decades, with a corresponding widespread use of antibiotics. This study provides information on current antibiotic use in freshwater aquaculture, as well as on resulting antibiotic concentrations in the aquatic environment of the Mekong Delta. Two major production steps, fish hatcheries and mature fish cultivation, were surveyed (50 fish farm interviews) for antibiotic use. Different water sources, including surface water, groundwater and piped water (164 water samples) were systematically screened for antibiotic residues. To better understand antibiotic fate under tropical conditions, the dissipation behavior of selected antibiotics in the aquatic environment was investigated for the first time in mesocosm experiments. None of the investigated antibiotics were detected in groundwater and piped water samples. Surface water, which is still often used for drinking and domestic purposes by local populations, contained median concentrations of 21 ng L-1 sulfamethoxazole (SMX), 4 ng L-1 sulfadiazine (SDZ), 17 ng L-1 trimethoprim (TRIM), and 12 ng L-1 enrofloxacin (ENRO). These concentrations were lower than the predicted no effect concentrations (PNECs) and minimum inhibitory concentrations (MICs), suggesting limited antibiotic-related risk to aquatic ecosystems in the monitored systems. The dissipation half-lives of the studied antibiotics ranged from <1 to 44 days, depending on the availability of sunlight and sediment. Among the studied antibiotics TRIM was the most persistent in water systems. TRIM was not susceptible to photodegradation, while the dissipation of ENRO and SDZ was influenced by photolysis. The recorded dissipation models gave good predictions of the occurrence and concentrations of TRIM, ENRO and SDZ in surface water. In summary, the currently measured concentrations of the investigated antibiotics are unlikely to cause immediate risks to the

  19. Bottom sediments affect Sonneratia mangrove forests in the prograding Mekong delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Nardin, William; Woodcock, Curtis E.; Fagherazzi, Sergio

    2016-08-01

    Mangrove forests exert a strong influence on tropical deltas by trapping sediments discharged by rivers and by stabilizing the substrate with roots. Understanding the dynamics of sediments and morphology in and around mangrove forests is critical in order to assess the resilience of coastlines in a period of accelerated sea level rise. In this research, sediment samples, mangrove forest characteristics, and remote sensing data are used to investigate the relationship between mangroves and sediment substrate in the Mekong Delta, Vietnam. Our data show a significant correlation between percent of sand in bottom sediments and density of Sonneratia caseolaris forest. We ascribe this result to higher sediment disturbance in muddy areas that prevents seedling establishment. This correlation potentially allows the determination of substrate characteristics from vegetation attributes detected by remote sensing, despite the impenetrability of the forest canopy. The results presented herein suggest that a supply of sand from the river and hydrodynamic processes moving the sand ashore control the density of the Sonneratia mangrove forests at this location, promoting tidal flat colonization and canopy expansion.

  20. Modelling The Environmental Impact of Controlling Saline Intrusion In The Mekong River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Lehmann, E.; Gowing, J.; Payton, R.

    The delta at the mouth of the Mekong River extends over 50,000 km2 in Vietnam and Cambodia. It is a highly productive environment both for rice and fish, but conflicts arise between their water quality demands. In this paper we focus on an investigation of this conflict in the Ca Mau peninsula, which lies entirely within Vietnam at the southern tip of the delta. The study area is a highly modified environment in which the natural mangrove veg- etation has been removed and a complex network of natural and man-made channels has been created. In an attempt to manage salinity intrusion into this environment, a number of tidal sluices have been constructed in recent years leading to progressive expansion of the area suitable for intensification of rice production. However, this has also led to negative impact on fish and shrimp production due to the change from brackish to fresh water conditions. The impact of this change is further exacerbated by the existence throughout a large part of the Ca Mau peninsula of acid sulphate soils. These are old marine sediments which are sulphur rich and have the potential to release sulphuric acid once they be- come oxidised. This has serious implications for productivity of rice fields and also for severe impacts on the aquatic environment. This paper reports an interdisciplinary investigation of the environmental impact of these changes. We identify the sources of acidity, which include rice fields, shrimp ponds and excavated channel sediments. We add different water quality modules to an existing hydraulic and transport model to allow simulation of temporal and spatial variation of water quality within the study area. We show a special interest on the water exchange between the fields and the canals as the area suffers from floods and dry spells.

  1. Identification of the prediction model for dengue incidence in Can Tho city, a Mekong Delta area in Vietnam.

    PubMed

    Phung, Dung; Huang, Cunrui; Rutherford, Shannon; Chu, Cordia; Wang, Xiaoming; Nguyen, Minh; Nguyen, Nga Huy; Manh, Cuong Do

    2015-01-01

    The Mekong Delta is highly vulnerable to climate change and a dengue endemic area in Vietnam. This study aims to examine the association between climate factors and dengue incidence and to identify the best climate prediction model for dengue incidence in Can Tho city, the Mekong Delta area in Vietnam. We used three different regression models comprising: standard multiple regression model (SMR), seasonal autoregressive integrated moving average model (SARIMA), and Poisson distributed lag model (PDLM) to examine the association between climate factors and dengue incidence over the period 2003-2010. We validated the models by forecasting dengue cases for the period of January-December, 2011 using the mean absolute percentage error (MAPE). Receiver operating characteristics curves were used to analyze the sensitivity of the forecast of a dengue outbreak. The results indicate that temperature and relative humidity are significantly associated with changes in dengue incidence consistently across the model methods used, but not cumulative rainfall. The Poisson distributed lag model (PDLM) performs the best prediction of dengue incidence for a 6, 9, and 12-month period and diagnosis of an outbreak however the SARIMA model performs a better prediction of dengue incidence for a 3-month period. The simple or standard multiple regression performed highly imprecise prediction of dengue incidence. We recommend a follow-up study to validate the model on a larger scale in the Mekong Delta region and to analyze the possibility of incorporating a climate-based dengue early warning method into the national dengue surveillance system. PMID:25447266

  2. Pesticide pollution of multiple drinking water sources in the Mekong Delta, Vietnam: evidence from two provinces.

    PubMed

    Chau, N D G; Sebesvari, Z; Amelung, W; Renaud, F G

    2015-06-01

    Pollution of drinking water sources with agrochemicals is often a major threat to human and ecosystem health in some river deltas, where agricultural production must meet the requirements of national food security or export aspirations. This study was performed to survey the use of different drinking water sources and their pollution with pesticides in order to inform on potential exposure sources to pesticides in rural areas of the Mekong River delta, Vietnam. The field work comprised both household surveys and monitoring of 15 frequently used pesticide active ingredients in different water sources used for drinking (surface water, groundwater, water at public pumping stations, surface water chemically treated at household level, harvested rainwater, and bottled water). Our research also considered the surrounding land use systems as well as the cropping seasons. Improper pesticide storage and waste disposal as well as inadequate personal protection during pesticide handling and application were widespread amongst the interviewed households, with little overall risk awareness for human and environmental health. The results show that despite the local differences in the amount and frequency of pesticides applied, pesticide pollution was ubiquitous. Isoprothiolane (max. concentration 8.49 μg L(-1)), fenobucarb (max. 2.32 μg L(-1)), and fipronil (max. 0.41 μg L(-1)) were detected in almost all analyzed water samples (98 % of all surface samples contained isoprothiolane, for instance). Other pesticides quantified comprised butachlor, pretilachlor, propiconazole, hexaconazole, difenoconazole, cypermethrin, fenoxapro-p-ethyl, tebuconazole, trifloxystrobin, azoxystrobin, quinalphos, and thiamethoxam. Among the studied water sources, concentrations were highest in canal waters. Pesticide concentrations varied with cropping season but did not diminish through the year. Even in harvested rainwater or purchased bottled water, up to 12 different pesticides were detected at

  3. Application of the Water Needs Index: Can Tho City, Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Moglia, Magnus; Neumann, Luis E.; Alexander, Kim S.; Nguyen, Minh N.; Sharma, Ashok K.; Cook, Stephen; Trung, Nguyen H.; Tuan, Dinh D. A.

    2012-10-01

    SummaryProvision of urban water supplies to rapidly growing cities of South East Asia is difficult because of increasing demand for limited water supplies, periodic droughts, and depletion and contamination of surface and groundwater. In such adverse environments, effective policy and planning processes are required to secure adequate water supplies. Developing a Water Needs Index reveals key elements of the complex urban water supply by means of a participatory approach for rapid and interdisciplinary assessment. The index uses deliberative interactions with stakeholders to create opportunities for mutual understanding, confirmation of constructs and capacity building of all involved. In Can Tho City, located at the heart of the Mekong delta in Vietnam, a Water Needs Index has been developed with local stakeholders. The functional attributes of the Water Needs Index at this urban scale have been critically appraised. Systemic water issues, supply problems, health issues and inadequate, poorly functioning infrastructure requiring attention from local authorities have been identified. Entrenched social and economic inequities in access to water and sanitation, as well as polluting environmental management practices has caused widespread problems for urban populations. The framework provides a common language based on systems thinking, increased cross-sectoral communication, as well as increased recognition of problem issues; this ought to lead to improved urban water management. Importantly, the case study shows that the approach can help to overcome biases of local planners based on their limited experience (information black spots), to allow them to address problems experienced in all areas of the city.

  4. Copper use and accumulation in catfish culture in the Mekong Delta, Vietnam.

    PubMed

    Marcussen, Helle; Løjmand, Helle; Dalsgaard, Anders; Hai, Dao M; Holm, Peter E

    2014-01-01

    Aquaculture of Pangasius hypophthalmus (striped catfish) in Vietnam reached 1.1 million tonnes in 2011 and catfish fillets are exported worldwide. The intensive cultures of catfish mainly in earth ponds have made it necessary to apply CuSO4 and other chemicals to control external parasites and other pathogens. However, accumulation of Cu in aquaculture ponds may pose a hazard to growth of fish or to the aquatic environment. The aim of this study was to determine accumulation of Cu in sediment, water and fish in a catfish pond with a history of repeated treatment with CuSO4 in the Mekong Delta, Vietnam. Copper concentrations in pond sediment were in the interval 21.3-45.7 mg kg(-1) dw and did not exceed the Vietnamese values for soil to be used for agricultural production (70 mg kg(-1) dw.). During three samplings the total mean concentration of Cu in pond water (4 μg L(-1)) did not exceed the LC50-value (70 μg L(-1)) for catfish and the mean dissolved concentration of Cu (0.986 μg L(-1)) did not seem to constitute a risk for the stability of the aquatic ecosystem. No significant variation in Cu concentrations between sampling sites in the pond and depth of sediment profile were determined. The accumulation of Cu in catfish was highest in the liver compared to the skin, gills and muscle tissue. With the current practice of removing pond sludge three to four times during a production cycle little if any Cu seems to accumulate in catfish ponds despite repeated anti-parasite treatments with CuSO4. Further studies are needed to assess the eco-toxicity and impact on agricultural production when pond sediment is discharged into aquatic recipients and used as soil fertilizer. PMID:24171418

  5. Modern sedimentation and morphology of the subaqueous Mekong Delta, Southern Vietnam

    NASA Astrophysics Data System (ADS)

    Unverricht, Daniel; Szczuciński, Witold; Stattegger, Karl; Jagodziński, Robert; Le, Xuan Thuyen; Kwong, Laval Liong Wee

    2013-11-01

    The Mekong River Delta is among the Asian mega-deltas and is influenced by various factors including tides (meso-tidal system), waves, coastal currents, monsoon-driven river discharge and human impact (agriculture, fishing, sand dredging, tourism). The present study aims to document the seafloor relief, sediment distribution and sediment accumulation rates to interpret modern sediment transport directions and main sedimentation processes in the subaqueous Mekong Delta. The major results of this investigation include the detection of two delta fronts 200 km apart, one at the mouth of the Bassac River (the biggest branch of the Mekong Delta) and the other around Cape Ca Mau (most south-western end of the Mekong Delta). Additionally, a large channel system runs in the subaqueous delta platform parallel to the shore and between the two fronts. The sediment accumulation rates vary greatly according to the location in the subaqueous delta and have reached up to 10 cm/yr for the last century. A cluster analysis of surface sediment samples revealed two different sediment types within the delta including a well-sorted sandy sediment and a poorly sorted, silty sediment. In addition, a third end member with medium to coarse sand characterised the distant parts of the delta at the transition to the open shelf. The increase of organic matter and carbonate content to the bottom set area and other sedimentary features such as shell fragments, foraminiferas and concretions of palaeo-soils that do not occur in delta sediments, supported grain size-based classification. Beginning in front of the Bassac River mouth, sedimentary pattern indicates clockwise sediment transport alongshore in the western direction to a broad topset area and the delta front around Cape Ca Mau. Our results clearly show the large lateral variability of the subaqueous Mekong Delta that is further complicated by strong monsoon-driven seasonality. River, tidal and wave forcing vary at local and seasonal scales

  6. Arsenic in groundwater of the Mekong Delta, Vietnam: contaminant expulsion from deep clays due to over-exploitation of aquifers

    NASA Astrophysics Data System (ADS)

    Erban, L.; Gorelick, S.; Zebker, H. A.; Fendorf, S. E.

    2013-12-01

    The Mekong Delta is home to over 20 million people living in Cambodia and Vietnam. Like many others in Southeast Asia, the Delta's aquifer system is prone to naturally-occurring arsenic contamination, a condition that may be exacerbated by human activities such as intensive groundwater use. Pumping in the Delta has increased significantly in recent decades, to meet a variety of agricultural, industrial and municipal demands, resulting in widespread overdraft, primarily in deep aquifers. We focus on analysis of an anomalously deep (200-500m) and large (>1000 km2) hotspot of groundwater arsenic contamination identified in a survey of >40,000 wells on the southern Vietnamese portion of the Delta. We employ a suite of methods to explore the relationship between regional-scale patterns in groundwater pumping and arsenic occurrence and to propose how the hotspot formed. Our analysis is based on examination of the arsenic survey in the context of hydraulic head data, 3D numerical aquifer system modeling, and InSAR-based measurements of land subsidence that indicate induced vertical deformation of up to 3 cm/yr. We suggest a new physical mechanism explaining deep aquifer contamination in the hotspot: expulsion of arsenic or arsenic-mobilizing solutes from compacting clays during over-exploitation of adjacent aquifers. The clay-compaction release mechanism has implications for wells in deep aquifers in arsenic-affected regions of the Mekong Delta, and potentially other similar systems, that test clean upon installation but may become contaminated over decades.

  7. Suspended sediment dynamics during the inter-monsoon season in the subaqueous Mekong Delta and adjacent shelf, southern Vietnam

    NASA Astrophysics Data System (ADS)

    Unverricht, Daniel; Nguyen, Thanh Cong; Heinrich, Christoph; Szczuciński, Witold; Lahajnar, Niko; Stattegger, Karl

    2014-01-01

    Land-ocean interactions in the coastal zone are severely influenced by tidal processes. In regions of high sediment discharge like the Mekong River Delta in southern Vietnam, these processes are even more significant. Three cruises in 2006, 2007 and 2008 were carried out to investigate the sediment suspension and their spatial distribution. Additionally, we investigated the influence of the tidal currents in relation to the suspended sediment. Therefore, all cruises took place during the inter-monsoon season between March and May where wave and wind influences are not dominant in contrast to the summer monsoon (May to early October) and winter monsoon season (November to early March).Suspended sediment concentrations (SSCs) in the particle-size range between 2.5 and 500 μm were measured with an LISST-instrument (Laser In Situ Scattering and Transmissiometry). Current velocities and directions were recorded with an Acoustic Doppler Current Profiler (ADCP). Additionally, data of different tidal gauge stations in the Mekong River Delta were correlated and compared to the mixed semidiurnal-diurnal tidal cycle.Our results show significant areas of SSCs greater than 25 μl/l in the Mekong River branches and its subaqueous delta during the inter-monsoon season. 20% of all measured SSCs in the subaqueous Mekong Delta exceed 100 μl/l. Highest concentrations occur close to the seabed. SSCs decrease at the transition to the open shelf. The shelf region contains only low suspension loads, especially on the south-eastern shelf (99% of all samples <25 μl/l). However, in the southern shelf region around Ca Mau Cape the suspension load is also higher (>25 μl/l) close to the seabed in water depths of 20-25 m.Two surveys lasting 25 h each were performed on mooring stations in 12 m (Mooring 1) and 26 m (Mooring 2) water depth and located 3.2 km apart on the subaqueous delta slope.Similar patterns of SSC over time show that concentrations of suspension load correlate with the

  8. Regional-Scale Controls on Arsenic Contamination in the Multi-Aquifer System of the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Erban, L.; Gorelick, S.; Fendorf, S. E.

    2014-12-01

    Geogenic groundwater arsenic poses a considerable health threat to a large, largely agrarian population in the Mekong Delta, Vietnam. Demand for groundwater continues to rise despite limited information about where arsenic contamination occurs and how it may be affected by excessive pumping. We investigate arsenic measurements from over >40,000 wells found throughout the Delta's seven major exploited aquifers, relating trends in contamination to ancillary physico-chemical datasets. Logistic regression modeling shows that among wells in the most shallow aquifers, arsenic occurrence above the WHO standard (10 µg/L) is best described by a well's distance to 1) the Mekong River network and 2) delta front, its depth and location within fault-bounded areas of the delta. The shallow model is inadequate to capture contaminant occurrence in deeper aquifers (generally 200-500m) where wells are rarely contaminated except in near-river areas undergoing heavy pumping. Our results are the first to quantify how the probability of arsenic contamination varies in 3D throughout the complex aquifer system in relation to both natural and anthropogenically-mediated factors, and suggest that excessive extraction may be degrading the quality of deep aquifers. Findings may serve as a baseline for managing groundwater use for optimal human welfare and assessing any future changes in arsenic occurrence.

  9. Aerobic decomposition of crop residues improves N availability and grain yield for three rice soils of the Mekong Delta, Vietnam: A screenhouse study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the Mekong Delta of Vietnam, rice (Oryza sativa, L.) is usually planted two to three times annually. Limited evidence elsewhere suggests that rice crop uptake of soil nitrogen (N) under such intensive cropping can be increased by replacing the customary anaerobic decomposition of crop residues wi...

  10. Intraspecific diversity of Edwardsiella ictaluri isolates from diseased freshwater catfish, Pangasianodon hypophthalmus (Sauvage), cultured in the Mekong Delta, Vietnam.

    PubMed

    Bartie, K L; Austin, F W; Diab, A; Dickson, C; Dung, T T; Giacomini, M; Crumlish, M

    2012-09-01

    A molecular epidemiology study was conducted on 90 Edwardsiella ictaluri isolates recovered from diseased farmed freshwater catfish, Pangasianodon hypophthalmus, cultured in the Mekong Delta, Vietnam. Thirteen isolates of E. ictaluri derived from diseased channel catfish, Ictalurus punctatus, cultured in the USA were included for comparison. All the E.ictaluri isolates tested were found to be biochemically indistinguishable. A repetitive (rep)-PCR using the single (GTG)(5) primer was shown to possess limited discriminatory power, yielding two similar DNA profiles categorized as (GTG)(5) -PCR group 1 or 2 among the Vietnam isolates and (GTG)(5) -PCR group 1 within the USA isolates. Macrorestriction analysis identified 14 and 22 unique pulsotypes by XbaI and SpeI, respectively, among a subset of 59 E. ictaluri isolates. Numerical analysis of the combined macrorestriction profiles revealed three main groups: a distinct cluster formed exclusively of the USA isolates, and a major and minor cluster with outliers contained the Vietnam isolates. Antibiotic susceptibility and plasmid profiling supported the existence of the three groups. The results indicate that macrorestriction analysis may be regarded as a suitable typing method among the E. ictaluri species of limited intraspecific diversity. Furthermore, the findings suggest that E. ictaluri originating from Vietnam may constitute a distinct genetic group. PMID:22804634

  11. Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence.

    PubMed

    Erban, Laura E; Gorelick, Steven M; Zebker, Howard A; Fendorf, Scott

    2013-08-20

    Deep aquifers in South and Southeast Asia are increasingly exploited as presumed sources of pathogen- and arsenic-free water, although little is known of the processes that may compromise their long-term viability. We analyze a large area (>1,000 km(2)) of the Mekong Delta, Vietnam, in which arsenic is found pervasively in deep, Pliocene-Miocene-age aquifers, where nearly 900 wells at depths of 200-500 m are contaminated. There, intensive groundwater extraction is causing land subsidence of up to 3 cm/y as measured using satellite-based radar images from 2007 to 2010 and consistent with transient 3D aquifer simulations showing similar subsidence rates and total subsidence of up to 27 cm since 1988. We propose a previously unrecognized mechanism in which deep groundwater extraction is causing interbedded clays to compact and expel water containing dissolved arsenic or arsenic-mobilizing solutes (e.g., dissolved organic carbon and competing ions) to deep aquifers over decades. The implication for the broader Mekong Delta region, and potentially others like it across Asia, is that deep, untreated groundwater will not necessarily remain a safe source of drinking water. PMID:23918360

  12. Release of arsenic to deep groundwater in the Mekong Delta, Vietnam, linked to pumping-induced land subsidence

    PubMed Central

    Erban, Laura E.; Gorelick, Steven M.; Zebker, Howard A.; Fendorf, Scott

    2013-01-01

    Deep aquifers in South and Southeast Asia are increasingly exploited as presumed sources of pathogen- and arsenic-free water, although little is known of the processes that may compromise their long-term viability. We analyze a large area (>1,000 km2) of the Mekong Delta, Vietnam, in which arsenic is found pervasively in deep, Pliocene–Miocene-age aquifers, where nearly 900 wells at depths of 200–500 m are contaminated. There, intensive groundwater extraction is causing land subsidence of up to 3 cm/y as measured using satellite-based radar images from 2007 to 2010 and consistent with transient 3D aquifer simulations showing similar subsidence rates and total subsidence of up to 27 cm since 1988. We propose a previously unrecognized mechanism in which deep groundwater extraction is causing interbedded clays to compact and expel water containing dissolved arsenic or arsenic-mobilizing solutes (e.g., dissolved organic carbon and competing ions) to deep aquifers over decades. The implication for the broader Mekong Delta region, and potentially others like it across Asia, is that deep, untreated groundwater will not necessarily remain a safe source of drinking water. PMID:23918360

  13. Pesticide management and their residues in sediments and surface and drinking water in the Mekong Delta, Vietnam.

    PubMed

    Toan, Pham Van; Sebesvari, Zita; Bläsing, Melanie; Rosendahl, Ingrid; Renaud, Fabrice G

    2013-05-01

    Public concern in Vietnam is increasing with respect to pesticide pollution of the environment and of drinking water resources. While established monitoring programs in the Mekong Delta (MD) focus on the analysis of organochlorines and some organophosphates, the environmental concentrations of more recently used pesticides such as carbamates, pyrethroides, and triazoles are not monitored. In the present study, household level pesticide use and management was therefore surveyed and combined with a one year environmental monitoring program of thirteen relevant pesticides (buprofezin, butachlor, cypermethrin, α-endosulfan, β-endosulfan, endosulfan-sulfate, fenobucarb, fipronil, isoprothiolane, pretilachlor, profenofos, propanil, and propiconazole) in surface water, soil, and sediment samples. The surveys showed that household level pesticide management remains suboptimal in the Mekong Delta. As a consequence, a wide range of pesticide residues were present in water, soil, and sediments throughout the monitoring period. Maximum concentrations recorded were up to 11.24 μg l(-1) in water for isoprothiolane and up to 521 μg kg(-1) dm in sediment for buprofezin. Annual average concentrations ranged up to 3.34 μg l(-1) in water and up to 135 μg kg(-1) dm in sediment, both for isoprothiolane. Occurrence of pesticides in the environment throughout the year and co-occurrence of several pesticides in the samples indicate a considerable chronic exposure of biota and humans to pesticides. This has a high relevance in the delta as water for drinking is often extracted from canals and rivers by rural households (GSO, 2005, and own surveys). The treatment used by the households for preparing surface water prior to consumption (flocculation followed by boiling) is insufficient for the removal of the studied pesticides and boiling can actually increase the concentration of non-volatile pollutants. PMID:23500396

  14. Discrimination rice cropping systems using multi-temporal Proba-V data in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Son, Nguyen-Thanh; Chen, Chi-Farn; Chen, Cheng-Ru; Chang, Ly-Yu; Chiang, Shou-Hao; Lau, Khin-Va

    2016-04-01

    Rice is considered a main source of livelihoods for several billions of people worldwide and plays an important role in the economy of many Asian countries. More than just a food source, rice production is regarded as one of the most important components to maintaining political stability and is also a national subject of economic policy due to domestic food consumption and grain exports. Vietnam is globally one of the largest rice producers and suppliers with more than 80% of the exported rice amount produced from the Mekong River Delta. This delta is one of the three deltas in the world most vulnerable to the climate change, causing the potential loss of rice yields. Thus, spatiotemporal information of rice cropping systems is important for agricultural management to ensure food security and rice grain exports. Coarse resolution satellite data such as MODIS demonstrates the applicability for rice mapping at a large scale. However, the use of MODIS data for such a monitoring purpose still reveals a challenging task due to mixed-pixel issues. The Proba-V satellite launched on 7 May 2013 is a potential candidate for this monitoring purpose because the data include four spectral bands (blue, red, near-infrared and mid-infrared) with a swath of 2,285 km with a spatial resolution of 100 m and temporal resolution of 5 days. This study aimed to investigate the applicability of multi-temporal Proba-V data for mapping rice cropping systems in Mekong Delta River, South Vietnam. The data were processed for 2014-2015 rice cropping seasons, following three main steps: (1) construction of smooth time-series NDVI data, (2) classification of rice cropping systems using crop phenological metrics, and (3) accuracy assessment of the mapping results. The results indicated that the smooth time-series NDVI profiles characterized the temporal spectral responses of rice fields through different growing stages of rice plant, which was critically important for understanding rice crop

  15. The combined impact on the flooding in Vietnam's Mekong River delta of local man-made structures, sea level rise, and dams upstream in the river catchment

    NASA Astrophysics Data System (ADS)

    Le, Thi Viet Hoa; Nguyen, Huu Nhan; Wolanski, Eric; Tran, Thanh Cong; Haruyama, Shigeko

    2007-01-01

    The Mekong River delta plays an important role in the Vietnamese economy and it has been severely impacted during this century by a series of unusually large floods. In the dry season the delta is also impacted by salinity intrusion and tides. These effects have caused severe human hardship. To mitigate these impacts, a large number of engineering structures, primarily dykes and weirs, have been built in the delta in recent years and are still being built, mainly to control floods and saltwater intrusion. These control measures are still being upgraded. A GIS-linked numerical model shows that the flood levels in the delta depend on the combined impacts of high river flows in the Mekong River, storm surges, sea level rise, and the likely, future siltation of the Mekong Estuary resulting from the construction of dams in China as well as many other dams proposed throughout the remaining river catchment. The model suggests that the engineering structures in the delta increase the flow velocities in the rivers and canals, increasing bank erosion, and cause the water to be deeper in the rivers and canals. This increases flooding in the non-protected areas of the delta and increases the risk of catastrophic failure of the dykes in the protected areas. The model also predicts that a sea level rise induced by global warming will enhance flooding in the Mekong River delta in Vietnam, and that flooding may worsen in the long term as a result of estuarine siltation resulting from the construction of dams. At the scale of the Mekong River basin, a multinational water resources management plan is needed that includes the hydrological needs of the delta. At the scale of the delta, a compromise is needed between allowing some flooding necessary for agriculture and preventing catastrophic flooding to alleviate human suffering.

  16. Status and changes of mangrove forest in Mekong Delta: Case study in Tra Vinh, Vietnam

    NASA Astrophysics Data System (ADS)

    Thu, Phan Minh; Populus, Jacques

    2007-01-01

    Because shrimp culture in the Mekong Delta develops rapidly, it has negatively impacted the environment, socio-economics and natural resources. In particular, mangrove forests have been altered by the shrimp culture. The area of mangrove forests in the region has been reduced and this is seen especially in Tra Vinh province. The results obtained from GIS (Geography Information System) and RS (Remote Sensing) show the status of mangrove forests in Tra Vinh province in 1965, 1995 (Northeastern part of Tra Vinh Province) and 2001. In 1965, the area of mangrove forests was 21,221 ha making up 56% of total land-use, while in 2001 it was 12,797 ha making up 37% of total land-use. Also based on GIS analysis, over the 36 years (1965-2001), the total coverage of mangrove forests have decreased by 50% since 1965. However, the speed of mangrove forest destruction in the period from 1965 to 1995 was much less than that in the period from 1995 to 2001. The average annual reduction in mangrove forest coverage in the first period (1965-1995) was 0.2% whereas it was 13.1% in the later period (1995-2001). For the long time, mangrove deforestation has been caused by war, collection of firewood and clearing for agriculture, and recently, shrimp farming has significantly contributed rate of mangrove destruction.

  17. Farmers' Perceived Risks of Climate Change and Influencing Factors: A Study in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Le Dang, Hoa; Li, Elton; Nuberg, Ian; Bruwer, Johan

    2014-08-01

    Many countries are confronting climate change that threatens agricultural production and farmers' lives. Farmers' perceived risks of climate change and factors influencing those perceived risks are critical to their adaptive behavior and well-planned adaptation strategies. However, there is limited understanding of these issues. In this paper, we attempt to quantitatively measure farmers' perceived risks of climate change and explore the influences of risk experience, information, belief in climate change, and trust in public adaptation to those perceived risks. Data are from structured interviews with 598 farmers in the Mekong Delta. The study shows that perceived risks to production, physical health, and income dimensions receive greater priority while farmers pay less attention to risks to happiness and social relationships. Experiences of the events that can be attributed to climate change increase farmers' perceived risks. Information variables can increase or decrease perceived risks, depending on the sources of information. Farmers who believe that climate change is actually happening and influencing their family's lives, perceive higher risks in most dimensions. Farmers who think that climate change is not their concern but the government's, perceive lower risks to physical health, finance, and production. As to trust in public adaptation, farmers who believe that public adaptive measures are well co-ordinated, perceive lower risks to production and psychology. Interestingly, those who believe that the disaster warning system is working well, perceive higher risks to finance, production, and social relationships. Further attention is suggested for the quality, timing, and channels of information about climate change and adaptation.

  18. Farmers' perceived risks of climate change and influencing factors: a study in the Mekong Delta, Vietnam.

    PubMed

    Le Dang, Hoa; Li, Elton; Nuberg, Ian; Bruwer, Johan

    2014-08-01

    Many countries are confronting climate change that threatens agricultural production and farmers' lives. Farmers' perceived risks of climate change and factors influencing those perceived risks are critical to their adaptive behavior and well-planned adaptation strategies. However, there is limited understanding of these issues. In this paper, we attempt to quantitatively measure farmers' perceived risks of climate change and explore the influences of risk experience, information, belief in climate change, and trust in public adaptation to those perceived risks. Data are from structured interviews with 598 farmers in the Mekong Delta. The study shows that perceived risks to production, physical health, and income dimensions receive greater priority while farmers pay less attention to risks to happiness and social relationships. Experiences of the events that can be attributed to climate change increase farmers' perceived risks. Information variables can increase or decrease perceived risks, depending on the sources of information. Farmers who believe that climate change is actually happening and influencing their family's lives, perceive higher risks in most dimensions. Farmers who think that climate change is not their concern but the government's, perceive lower risks to physical health, finance, and production. As to trust in public adaptation, farmers who believe that public adaptive measures are well co-ordinated, perceive lower risks to production and psychology. Interestingly, those who believe that the disaster warning system is working well, perceive higher risks to finance, production, and social relationships. Further attention is suggested for the quality, timing, and channels of information about climate change and adaptation. PMID:24894008

  19. Spatiotemporal simulation of changes in rice cropping systems in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Chen, Cheng-Ru; Chen, Chi-Farn; Son, Nguyen-Thanh

    2015-04-01

    With the dramatic development of agro-economics, population growth, and climate change, the rice cropping systems in the Vietnamese Mekong Delta (VMD) have been undergoing a major change. Information on rice cropping practices and changes in cropping systems is critical for policymakers to devise successful strategies to ensure food security and rice grain exports for the country. The primary objective of this research is to map rice cropping systems and predict future dynamics of rice cropping systems using MODIS time-series data from 2002 to 2012. A phenology-based classification approach was applied for the classification and assessment of rice cropping systems. Then, the Cellular Automata-Markov (CA-Markov) model was used to simulate future changes in rice-cropping activities. To obtain precise prediction, a calibration of CA-Markov were implemented by using a series of rice crop maps. The comparisons between the classification maps and the ground reference data indicated satisfactory results with overall accuracies above 81%, and Kappa coefficients above 0.75, respectively. The simulated maps of rice cropping systems for 2010-2012 were extrapolated by CA-Markov model based on the trend of rice cropping systems during 2002-2009. The comparison between the predicted scenarios and the classification maps for 2010-2012 presents a reasonably close agreement. In summary, the CA-Markov model with a long-term calibration confirmed the validity of the approach for dynamic modeling of changes in rice cropping systems in the study region. The results obtained from this study demonstrate that the approach produced satisfactory results in terms of accuracy, quantitative forecast, and spatial pattern changes. Thus, projections of future changes would provide useful information for the agricultural policymakers in respect to formulating effective management strategies of rice cropping practices in VMD.

  20. Sex pheromones of three citrus leafrollers, Archips atrolucens, Adoxophyes privatana, and Homona sp., inhabiting the Mekong Delta of Vietnam.

    PubMed

    Van Vang, Le; Thuy, Ho Nhu; Khanh, Chau Nguyen Quoc; Son, Pham Kim; Yan, Qi; Yamamoto, Masanobu; Jinbo, Utsugi; Ando, Tetsu

    2013-06-01

    Archips atrolucens, Adoxophyes privatana, and Homona sp. are serious defoliators of citrus trees in the Mekong Delta of Vietnam. In order to establish a sustainable pest-management program for the three species, their female-produced sex pheromones were investigated by GC-EAD and GC-MS analyses, and the following multi-component pheromones were identified: (Z)-11-tetradecenyl acetate (Z11-14:OAc), (E)-11-tetradecenyl acetate (E11-14:OAc), and tetradecyl acetate (14:OAc) in a ratio of 64:32:4 for A. atrolucens; Z11-14:OAc and (Z)-9-tetradecenyl acetate (Z9-14:OAc) in a ratio of 92:8 for A. privatana; and Z11-14:OAc and (Z)-9-dodecenyl acetate (Z9-12:OAc) in a ratio of 96:4 for Homona sp. Each lure baited with synthetic components as a mimic of the natural pheromone attracted males of the target species specifically, indicating that each monounsaturated minor component plays a significant role for mating communication and reproductive isolation of the three species inhabiting the same citrus orchards. In an extract of the pheromone glands of A. atrolucens females, the content of 14:OAc was very low, but a synergistic effect was observed clearly when the saturated compound was mixed at the same level as the E11-14:OAc. The synthetic lures will provide useful tools for monitoring flights of adults of the three species. PMID:23674124

  1. Simulated impacts of climate change on current farming locations of striped catfish (Pangasianodon hypophthalmus; Sauvage) in the Mekong Delta, Vietnam.

    PubMed

    Nguyen, Anh L; Dang, Vinh H; Bosma, Roel H; Verreth, Johan A J; Leemans, Rik; De Silva, Sena S

    2014-12-01

    In Vietnam, culturing striped catfish makes an important contribution to the Mekong Delta's economy. Water level rise during rainy season and salt intrusion during dry season affect the water exchange and quality for this culture. Sea level rise as a consequence of climate change will worsen these influences. In this study, water level rise and salt water intrusion for three sea level rise (SLR) scenarios (i.e., +30, +50, and +75 cm) were simulated. The results showed that at SLR +50, the 3-m-flood level would spread downstream and threaten farms located in AnGiang, DongThap and CanTho provinces. Rising salinity levels for SLR +75 would reduce the window appropriate for the culture in SocTrang and BenTre provinces, and in TienGiang's coastal districts. Next to increasing dikes to reduce the impacts, the most tenable and least disruptive option to the farming community would be to shift to a salinity tolerant strain of catfish. PMID:24715387

  2. Rodents and Risk in the Mekong Delta of Vietnam: Seroprevalence of Selected Zoonotic Viruses in Rodents and Humans

    PubMed Central

    Van Cuong, Nguyen; Carrique-Mas, Juan; Vo Be, Hien; An, Nguyen Ngoc; Tue, Ngo Tri; Anh, Nguyet Lam; Anh, Pham Hong; Phuc, Nguyen The; Baker, Stephen; Voutilainen, Liina; Jääskeläinen, Anne; Huhtamo, Eili; Utriainen, Mira; Sironen, Tarja; Vaheri, Antti; Henttonen, Heikki; Vapalahti, Olli; Chaval, Yannick

    2015-01-01

    Abstract In the Mekong Delta in southern Vietnam, rats are commonly traded in wet markets and sold live for food consumption. We investigated seroprevalence to selected groups of rodent-borne viruses among human populations with high levels of animal exposure and among co-located rodent populations. The indirect fluorescence antibody test (IFAT) was used to determine seropositivity to representative reference strains of hantaviruses (Dobrava virus [DOBV], Seoul virus [SEOV]), cowpox virus, arenaviruses (lymphocytic choriomeningitis virus [LCMV]), flaviviruses (tick-borne encephalitis virus [TBEV]), and rodent parechoviruses (Ljungan virus), using sera from 245 humans living in Dong Thap Province and 275 rodents representing the five common rodent species sold in wet markets and present in peridomestic and farm settings. Combined seropositivity to DOBV and SEOV among the rodents and humans was 6.9% (19/275) and 3.7% (9/245), respectively; 1.1% (3/275) and 4.5% (11/245) to cowpox virus; 5.4% (15/275) and 47.3% (116/245) for TBEV; and exposure to Ljungan virus was 18.8% (46/245) in humans, but 0% in rodents. Very little seroreactivity was observed to LCMV in either rodents (1/275, 0.4%) or humans (2/245, 0.8%). Molecular screening of rodent liver tissues using consensus primers for flaviviruses did not yield any amplicons, whereas molecular screening of rodent lung tissues for hantavirus yielded one hantavirus sequence (SEOV). In summary, these results indicate low to moderate levels of endemic hantavirus circulation, possible circulation of a flavivirus in rodent reservoirs, and the first available data on human exposures to parechoviruses in Vietnam. Although the current evidence suggests only limited exposure of humans to known rodent-borne diseases, further research is warranted to assess public health implications of the rodent trade. PMID:25629782

  3. Spatial and temporal variability of surface water pollution in the Mekong Delta, Vietnam.

    PubMed

    Wilbers, Gert-Jan; Becker, Mathias; Nga, La Thi; Sebesvari, Zita; Renaud, Fabrice G

    2014-07-01

    Surface water pollution in the Vietnamese Mekong Delta (MD) could threaten human, animal and ecosystem health given the fact that this water source is intensively used for drinking, irrigation and domestic services. We therefore determined the levels of pollution by organic pollutants, salts, metals and microbial indicators by (bi)monthly monitoring of canals between November 2011 and July 2012 at 32 sampling locations, representing fresh and saline/brackish environments. The results were compared with national water quality guidelines, between the studied regions and with water quality data from main waterways. Key factors explaining the observed levels of pollution in surface water were identified through principal component analysis (PCA). Temporal variations due to tidal regime and seasonality were also assessed. Based on regression models, the spatial variability of five water quality parameters was visualized using GIS based maps. Results indicate that pH (max. 8.6), turbidity (max. 461 FTU), maximum concentrations of ammonium (14.7 mg L(-1)), arsenic (44.1 μg L(-1)), barium (157.5 μg L(-1)), chromium (84.7 μg L(-1)), mercury (45.5 μg L(-1)), manganese (1659.7 μg L(-1)), aluminum (14.5 mg L(-1)), iron (17.0 mg L(-1)) and the number of Escherichia coli (87,000 CFU 100 mL(-1)) and total coliforms (2,500,000 CFU 100 mL(-1)) in canals exceed the thresholds set by Vietnamese quality guidelines for drinking and domestic purposes. The PCA showed that i) urbanization; ii) metal leaching from soils; iii) aquaculture; and iv) tidal regime explain 85% of the variance of surface water quality attributes. Significant differences in water quality were found due to daily tidal regime and as a result of seasonality. Surface water quality maps for dissolved oxygen, ammonium, ortho-phosphate, manganese and total coliforms were developed to highlight hot-spot areas of pollution. The results of this study can assist policy makers in developing water management strategies

  4. Arsenic in the multi-aquifer system of the Mekong Delta, Vietnam: analysis of large-scale spatial trends and controlling factors.

    PubMed

    Erban, Laura E; Gorelick, Steven M; Fendorf, Scott

    2014-06-01

    Groundwater exploitation is rising in the Mekong Delta, Vietnam, potentially exacerbating arsenic contamination from natural sources. We investigate trends and controls on contamination patterns throughout the Delta's multi-aquifer system as observed in a spatially exhaustive data set of arsenic measured in >40,000 wells, 10.5% of which exceed the WHO drinking water standard for arsenic (10 μg/L). We relate strong trends in the distribution of contamination among well samples to explanatory variables derived from 3D ancillary physicochemical data sets using logistic regression models. Parsimonious models describe much of the observed variability in arsenic occurrence, which differs considerably between subsets of wells tapping shallow versus deeper aquifer groups. In the shallowest Holocene-Pleistocene aquifers, arsenic occurrence is best described by distance to the Mekong river channels and delta front, depth, and location within fault-bounded zones of the region. The same model, however, fails to explain observations in the deeper group of Pliocene-Miocene aquifers. Among these deeper units, arsenic occurrence is rare except among older wells in near-river, heavily pumped areas. Our analysis is the first to examine both natural and anthropogenically mediated contributions to the distribution of arsenic throughout the Mekong Delta's multi-aquifer system, with implications for management of similarly affected basins throughout Southeast Asia. PMID:24849074

  5. Effects of chlorpyrifos ethyl on acetylcholinesterase activity in climbing perch cultured in rice fields in the Mekong Delta, Vietnam.

    PubMed

    Nguyen, Tam Thanh; Berg, Håkan; Nguyen, Hang Thi Thuy; Nguyen, Cong Van

    2015-07-01

    Climbing perch is commonly harvested in rice fields and associated wetlands in the Mekong Delta. Despite its importance in providing food and income to local households, there is little information how this fish species is affected by the high use of pesticides in rice farming. Organophosphate insecticides, such as chlorpyrifos ethyl, which are highly toxic to aquatic organisms, are commonly used in the Mekong Delta. This study shows that the brain acetylcholinesterase (AChE) activity in climbing perch fingerlings cultured in rice fields, was significantly inhibited by a single application of chlorpyrifos ethyl, at doses commonly applied by rice farmers (0.32-0.64 kg/ha). The water concentration of chlorpyrifos ethyl decreased below the detection level within 3 days, but the inhibition of brain AChE activity remained for more than 12 days. In addition, the chlorpyrifos ethyl treatments had a significant impact on the survival and growth rates of climbing perch fingerlings, which were proportional to the exposure levels. The results indicate that the high use of pesticides among rice farmers in the Mekong Delta could have a negative impact on aquatic organisms and fish yields, with implications for the aquatic biodiversity, local people's livelihoods and the aquaculture industry in the Mekong Delta. PMID:25828891

  6. Monitoring of rice cropping intensity in the upper Mekong Delta, Vietnam using time-series MODIS data

    NASA Astrophysics Data System (ADS)

    Chen, C. F.; Son, N. T.; Chang, L. Y.

    2012-01-01

    Information on rice growing areas is important for policymakers to devise agricultural plans. This research explores the monitoring of rice cropping intensity in the upper Mekong Delta, Vietnam (from 2001 to 2007) using time-series MODIS NDVI 250-m data. Data processing includes three steps: (1) noise is filtered from the time-series NDVI data using empirical mode decomposition (EMD); (2) endmembers are extracted from the filtered time-series data and trained in a linear mixture model (LMM) for classification of rice cropping systems; and (3) classification results are verified by comparing them with the ground-truth and statistical data. The results indicate that EMD is a good filter for noise removal from the time-series data. The classification results confirm the validity of LMM, giving an overall accuracy of 90.1% and a Kappa coefficient of 0.7. The lowest producer and user accuracies were associated with single crop rain-fed rice class due to the mixed pixel problems. A strong yearly correlation at the district level was revealed in the MODIS-derived areas (R2 ⩾ 0.9). Investigation of interannual changes in rice cropping intensity from 2001 to 2007 showed a remarkable conversion from double to triple crop irrigated rice from 2001 to 2003, especially in the Thoai Son and Phu Tan districts. A big conversion from triple crop rice back to double crop rice cultivation was also observed in Phu Tan from 2005 to 2006. These changes were verified by visual interpretation of Landsat images and examination of NDVI profiles.

  7. Molecular Characterization of HIV-1 CRF01_AE in Mekong Delta, Vietnam, and Impact of T-Cell Epitope Mutations on HLA Recognition (ANRS 12159)

    PubMed Central

    Bellecave, Pantxika; Guidicelli, Gwenda-Line; Anies, Guerric; Hoang Khanh Thu, Huynh; Pillot Debelleix, Marie; Vray, Muriel; Recordon-Pinson, Patricia; Taupin, Jean-Luc; Thi Xuan Lien, Truong; Fleury, Herve

    2011-01-01

    Background To date, 11 HIV-1 subtypes and 48 circulating recombinant forms have been described worldwide. The underlying reason why their distribution is so heterogeneous is not clear. Host genetic factors could partly explain this distribution. The aim of this study was to describe HIV-1 strains circulating in an unexplored area of Mekong Delta, Vietnam, and to assess the impact of optimal epitope mutations on HLA binding. Methods We recruited 125 chronically antiretroviral-naive HIV-1-infected subjects from five cities in the Mekong Delta. We performed high-resolution DNA typing of HLA class I alleles, sequencing of Gag and RT-Prot genes and phylogenetic analysis of the strains. Epitope mutations were analyzed in patients bearing the HLA allele restricting the studied epitope. Optimal wild-type epitopes from the Los Alamos database were used as reference. T-cell epitope recognition was predicted using the immune epitope database tool according to three different scores involved in antigen processing (TAP and proteasome scores) and HLA binding (MHC score). Results All sequences clustered with CRF01_AE. HLA class I genotyping showed the predominance of Asian alleles as A*11:01 and B*46:01 with a Vietnamese specificity held by two different haplotypes. The percentage of homology between Mekong and B consensus HIV-1 sequences was above 85%. Divergent epitopes had TAP and proteasome scores comparable with wild-type epitopes. MHC scores were significantly lower in divergent epitopes with a mean of 2.4 (±0.9) versus 2 (±0.7) in non-divergent ones (p<0.0001). Conclusions Our study confirms the wide predominance of CRF01_AE in the Mekong Delta where patients harbor a specific HLA pattern. Moreover, it demonstrates the lower MHC binding affinity among divergent epitopes. This weak immune pressure combined with a narrow genetic diversity favors immune escape and could explain why CRF01_AE is still predominant in Vietnam, particularly in the Mekong area. PMID:22039450

  8. Analysis of biomagnification of persistent organic pollutants in the aquatic food web of the Mekong Delta, South Vietnam using stable carbon and nitrogen isotopes.

    PubMed

    Ikemoto, Tokutaka; Tu, Nguyen Phuc Cam; Watanabe, Michio X; Okuda, Noboru; Omori, Koji; Tanabe, Shinsuke; Tuyen, Bui Cach; Takeuchi, Ichiro

    2008-05-01

    The present study elucidated the biomagnification profiles of persistent organic pollutants (POPs) through a tropical aquatic food web of Vietnam based on trophic characterization using stable nitrogen analysis. Various biological samples collected from the main stream of the Mekong Delta were provided for the analysis for both POPs, and stable nitrogen and carbon isotope ratios. Of the POPs analyzed, dichlorodiphenyltrichloroethane and its metabolites (DDTs) were the predominant contaminants with concentrations ranging from 0.058 to 12 ng/g wet weight, followed by polychlorinated biphenyls (PCBs) at 0.017-8.9 ng/g, chlordane compounds (CHLs) at 0.0043-0.76 ng/g, tris-4-chlorophenyl methane (TCPMe) at N.D.-0.26 ng/g, hexachlorocyclohexane isomers (HCHs) at N.D.-0.20 ng/g and hexachlorobenzene (HCB) at 0.0021-0.096 ng/g. Significant positive increases of concentrations in DDTs, CHLs, and TCPMe against the stable nitrogen ratio (delta(15)N) were detected, while, concentrations of HCHs and HCB showed no significant increase. The slopes of the regression equations between the log-transformed concentrations of these POPs and delta(15)N were used as indices of biomagnification. The slopes of the POPs for which positive biomagnification was detected ranged from 0.149 to 0.177 on a wet weight basis. The slopes of DDTs and CHLs were less than those reported for a marine food web of the Arctic Ocean, indicating that less biomagnification had occurred in the tropical food web. Of the isomers of CHLs, unlike the studies of the Arctic Ocean, oxychlordane did not undergo significant biomagnification through the food web of the Mekong Delta. This difference is considered to be due to a lack of marine mammals, which might metabolize cis- and trans-chlordane to oxychlordane, in the Mekong Delta ecosystem. The biomagnification profile of TCPMe is reported for the first time in the present study. PMID:18313720

  9. Combined fluvial and pluvial urban flood hazard analysis: method development and application to Can Tho City, Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Apel, H.; Trepat, O. M.; Hung, N. N.; Chinh, D. T.; Merz, B.; Dung, N. V.

    2015-08-01

    Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas, and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either fluvial or pluvial flood hazard, studies of combined fluvial and pluvial flood hazard are hardly available. Thus this study aims at the analysis of fluvial and pluvial flood hazard individually, but also at developing a method for the analysis of combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as example. In this tropical environment the annual monsoon triggered floods of the Mekong River can coincide with heavy local convective precipitation events causing both fluvial and pluvial flooding at the same time. Fluvial flood hazard was estimated with a copula based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. Pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data, and a stochastic rain storm generator. Inundation was simulated by a 2-dimensional hydrodynamic model implemented on a Graphical Processor Unit (GPU) for time-efficient flood propagation modelling. All hazards - fluvial, pluvial and combined - were accompanied by an uncertainty estimation considering the natural variability of the flood events. This resulted in probabilistic flood hazard maps showing the maximum inundation depths for a selected set of probabilities of occurrence, with maps showing the expectation (median) and the uncertainty by

  10. Ecological risk assessment of the antibiotic enrofloxacin applied to Pangasius catfish farms in the Mekong Delta, Vietnam.

    PubMed

    Andrieu, Margot; Rico, Andreu; Phu, Tran Minh; Huong, Do Thi Thanh; Phuong, Nguyen Thanh; Van den Brink, Paul J

    2015-01-01

    Antibiotics applied in aquaculture production may be released into the environment and contribute to the deterioration of surrounding aquatic ecosystems. In the present study, we assessed the ecological risks posed by the use of the antibiotic enrofloxacin (ENR), and its main metabolite ciprofloxacin (CIP), in a Pangasius catfish farm in the Mekong Delta region, Vietnam. Water and sediment samples were collected in a stream receiving effluents from a Pangasius catfish farm that had applied ENR. The toxicity of ENR and CIP was assessed on three tropical aquatic species: the green-algae Chlorella sp. (72 h - growth inhibition test), the micro-invertebrate Moina macrocopa (48 h - immobilization test), and the Nile tilapia (Oreochromis niloticus). The toxic effects on O. niloticus were evaluated by measuring the cholinesterase (ChE) and catalase (CAT) activities in the fish brain and muscles, respectively, and by considering feed exposure and water exposure separately. Ecological risks were assessed by comparing maximum exposure concentrations with predicted no effect concentrations for cyanobacteria, green algae, invertebrates and fish derived with available toxicity data. The results of this study showed that maximum antibiotic concentrations in Pangasius catfish farm effluents were 0.68 μg L(-1) for ENR and 0.25 μg L(-1) for CIP (dissolved water concentrations). Antibiotics accumulated in sediments down-stream the effluent discharge point at concentrations up to 2590 μg kg(-1) d.w. and 592 μg kg(-1) d.w. for ENR and CIP, respectively. The calculated EC50 values for ENR and CIP were 111000 and 23000 μg L(-1) for Chlorella sp., and 69000 and 71000 μg L(-1) for M. macrocopa, respectively. Significant effects on the ChE and CAT enzymatic activities of O. niloticus were observed at 5 g kg(-1) feed and 400-50000 μg L(-1), for both antibiotics. The results of the ecological risk assessment performed in this study indicated only minor risks for cyanobacteria

  11. Soil salinity and sodicity in a shrimp farming coastal area of the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Tho, Nguyen; Vromant, N.; Hung, Nguyen Thanh; Hens, L.

    2008-06-01

    Soil salinity and sodicity are environmental problems in the shrimp farming areas of the Cai Nuoc district, Ca Mau province, Vietnam. In 2000, farmers in the district switched en masse from rice cropping to shrimp culture. Due to recent failure in shrimp farming, many farmers wish to revert to a rotational system with rice in the wet season and shrimps in the dry season. So far, all their attempts to grow rice have failed. To assess soil salinity and sodicity, 25 boreholes in shrimp ponds were analysed in four consecutive seasons from 2002 to 2004. The results showed that soil salinity was quite serious (mean ECe 29.25 dS m-1), particularly in the dry season (mean ECe 33.44 dS m-1). In the wet season, significant amounts of salts still remained in the soil (mean ECe 24.65 dS m-1) and the highest soil salinity levels were found near the sea. Soil sodicity is also a problem in the district (exchangeable sodium percentage range 9.63-72.07%). Sodicity is mainly a phenomenon of topsoils and of soils near the sea. Both soil salinity and sodicity are regulated by seasonal rainfall patterns. They could together result in disastrous soil degradation in the Cai Nuoc district.

  12. High levels of contamination and antimicrobial-resistant non-typhoidal Salmonella serovars on pig and poultry farms in the Mekong Delta of Vietnam.

    PubMed

    Tu, L T P; Hoang, N V M; Cuong, N V; Campbell, J; Bryant, J E; Hoa, N T; Kiet, B T; Thompson, C; Duy, D T; Phat, V V; Hien, V B; Thwaites, G; Baker, S; Carrique-Mas, J J

    2015-10-01

    We investigated the prevalence, diversity, and antimicrobial resistance (AMR) profiles of non-typhoidal Salmonella (NTS) and associated risk factors on 341 pig, chicken, and duck farms in Dong Thap province (Mekong Delta, Vietnam). Sampling was stratified by species, district (four categories), and farm size (three categories). Pooled faeces, collected using boot swabs, were tested using ISO 6575: 2002 (Annex D). Isolates were serogrouped; group B isolates were tested by polymerase chain reaction to detect S. Typhimurium and (monophasic) serovar 4,[5],12:i:- variants. The farm-level adjusted NTS prevalence was 64·7%, 94·3% and 91·3% for chicken, duck and pig farms, respectively. Factors independently associated with NTS were duck farms [odds ratio (OR) 21·2], farm with >50 pigs (OR 11·9), pig farm with 5-50 pigs (OR 4·88) (vs. chickens), and frequent rodent sightings (OR 2·3). Both S. Typhimurium and monophasic S. Typhimurium were more common in duck farms. Isolates had a high prevalence of resistance (77·6%) against tetracycline, moderate resistance (20-30%) against chloramphenicol, sulfamethoxazole-trimethoprim, ampicillin and nalidixic acid, and low resistance (<5%) against ciprofloxacin and third-generation cephalosporins. Multidrug resistance (resistance against ⩾3 classes of antimicrobial) was independently associated with monophasic S. Typhimurium and other group B isolates (excluding S. Typhimurium) and pig farms. The unusually high prevalence of NTS on Mekong Delta farms poses formidable challenges for control. PMID:25778282

  13. Combined fluvial and pluvial urban flood hazard analysis: concept development and application to Can Tho city, Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Apel, Heiko; Martínez Trepat, Oriol; Nghia Hung, Nguyen; Thi Chinh, Do; Merz, Bruno; Viet Dung, Nguyen

    2016-04-01

    Many urban areas experience both fluvial and pluvial floods, because locations next to rivers are preferred settlement areas and the predominantly sealed urban surface prevents infiltration and facilitates surface inundation. The latter problem is enhanced in cities with insufficient or non-existent sewer systems. While there are a number of approaches to analyse either a fluvial or pluvial flood hazard, studies of a combined fluvial and pluvial flood hazard are hardly available. Thus this study aims to analyse a fluvial and a pluvial flood hazard individually, but also to develop a method for the analysis of a combined pluvial and fluvial flood hazard. This combined fluvial-pluvial flood hazard analysis is performed taking Can Tho city, the largest city in the Vietnamese part of the Mekong Delta, as an example. In this tropical environment the annual monsoon triggered floods of the Mekong River, which can coincide with heavy local convective precipitation events, causing both fluvial and pluvial flooding at the same time. The fluvial flood hazard was estimated with a copula-based bivariate extreme value statistic for the gauge Kratie at the upper boundary of the Mekong Delta and a large-scale hydrodynamic model of the Mekong Delta. This provided the boundaries for 2-dimensional hydrodynamic inundation simulation for Can Tho city. The pluvial hazard was estimated by a peak-over-threshold frequency estimation based on local rain gauge data and a stochastic rainstorm generator. Inundation for all flood scenarios was simulated by a 2-dimensional hydrodynamic model implemented on a Graphics Processing Unit (GPU) for time-efficient flood propagation modelling. The combined fluvial-pluvial flood scenarios were derived by adding rainstorms to the fluvial flood events during the highest fluvial water levels. The probabilities of occurrence of the combined events were determined assuming independence of the two flood types and taking the seasonality and probability of

  14. Mekong Delta at the crossroads: more control or adaptation?

    PubMed

    Käkönen, Mira

    2008-05-01

    Development in the Mekong Delta of Vietnam has been very dynamic in the recent past, and currently it stands at an interesting crossroads. On one hand, agricultural production has developed successfully, and economic growth has been very rapid, but on the other hand, intensifying agriculture and large-scale water-control structures have challenged the environmental sustainability and social equity. The development plans have included a strong belief in the human mastery over the nature and waters of the Mekong Delta. In many cases, water resources planners have underestimated the complexity and integrated nature of the ecology and livelihoods of the Mekong Delta. This article examines cases where development efforts, while successful in some dimensions, have also contributed to create new risks for, especially, the poorest groups. The current situation calls for a more sustainable future route that would require examination of more adaptive measures in relation to the changing water flows of the Mekong River. PMID:18595276

  15. Assimilation of MODIS-derived LAI by radiative transfer modelling to crop growth simulation model for rice crop monitoring and yield estimation in the Mekong delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Nguyen, H.; de Bie, K.; Verhoef, W.

    2014-12-01

    Successful monitoring of rice crops and estimation of its yields in Mekong delta provide vital information to government agencies, rice production stakeholders and insurance companies in making their decisions and plans to establish solutions to protect rice smallholders from the risks involved. Remote sensing-based information promises a cost-effective way to observe rice crop growth in the largest rice producing region of Vietnam. For an extensive rice cultivation region as the Mekong delta, the use of divergence statistic to extract information from long-term or hypertemporal optical remote sensing NDVI profile to map rice cropping patterns has shown a high degree of success. The result map provides accurate information on where rice grew, when it was seeded and harvested, how many time it was cultivated every year. In addition, by using 8-day MODIS TERRA surface reflectance in Soil-Leaf-Canopy (SLC) radiative transfer model, 70 percent variation of seasonal rice LAI values was able to capture, making it useful to be assimilated into a rice crop growth simulation model (ORYZA 2000) to estimate the regional rice production in the season of 2008-2009. Tested results from 56 rice fields located in different rice cropping patterns showed that yields estimated using ORYZA2000 can explain 83 percent variation of field measured yields. However, simulated yields by ORYZA 2000 were used to overestimate by the model since some of model parameters could not be recalibrated due to the lack of field experiment data. This suggest that in the future, in order to gain a better results of rice crop monitoring and yield estimation, apart from improving the estimation of MODIS -derived LAIs by using SLC, calibrating crop growth simulation's parameter have to be taken into account.

  16. Effective management for acidic pollution in the canal network of the Mekong Delta of Vietnam: a modeling approach.

    PubMed

    Phong, Ngo Dang; Hoanh, Chu Thai; Tuong, To Phuc; Malano, Hector

    2014-07-01

    Acidic pollution can cause severe environmental consequences annually in coastal areas overlain with acid sulfate soils (ASS). A water quality model was used as an analytical tool for exploring the effects of water management options and other interventions on acidic pollution and salinity in Bac Lieu, a coastal province of the Mekong Delta. Fifty eight percent of the provincial area is covered by ASS, and more than three-fourths (approximately 175,000 ha) are used for brackish-water shrimp culture. Simulations of acid water propagation in the canal network indicate that the combination of opening the two main sluices along the East Sea of the study area at high tide for one day every week in May and June and widening the canals that connect these sluices to the West Sea allows for adequate saline water intake and minimizes the acidic pollution in the study area. On the other hand, canal dredging in the freshwater ASS area should be done properly as it can create severe acidic pollution. PMID:24726961

  17. Rice crop mapping and change prediction using multi-temporal satellite images in the Mekong Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Chen, C. R.; Chen, C. F.; Nguyen, S. T.

    2014-12-01

    The rice cropping systems in the Vietnamese Mekong Delta (VMD) has been undergoing major changes to cope with developing agro-economics, increasing population and changing climate. Information on rice cropping practices and changes in cropping systems is critical for policymakers to devise successful strategies to ensure food security and rice grain exports for the country. The primary objective of this research is to map rice cropping systems and predict future dynamics of rice cropping systems using the MODIS time-series data of 2002, 2006, and 2010. First, a phenology-based classification approach was applied for the classification and assessment of rice cropping systems in study region. Second, the Cellular Automata-Markov (CA-Markov) models was used to simulate the rice-cropping system map of VMD for 2010. The comparisons between the classification maps and the ground reference data indicated satisfactory results with overall accuracies and Kappa coefficients, respectively, of 81.4% and 0.75 for 2002, 80.6% and 0.74 for 2006 and 85.5% and 0.81 for 2010. The simulated map of rice cropping system for 2010 was extrapolated by CA-Markov model based on the trend of rice cropping systems during 2002~2006. The comparison between predicted scenario and classification map for 2010 presents a reasonably closer agreement. In conclusion, the CA-Markov model performs a powerful tool for the dynamic modeling of changes in rice cropping systems, and the results obtained demonstrate that the approach produces satisfactory results in terms of accuracy, quantitative forecast and spatial pattern changes. Meanwhile, the projections of the future changes would provide useful inputs to the agricultural policy for effective management of the rice cropping practices in VMD.

  18. Highly Pathogenic Avian Influenza Virus A/H5N1 Infection in Vaccinated Meat Duck Flocks in the Mekong Delta of Vietnam.

    PubMed

    Cuong, N V; Truc, V N T; Nhung, N T; Thanh, T T; Chieu, T T B; Hieu, T Q; Men, N T; Mai, H H; Chi, H T; Boni, M F; van Doorn, H R; Thwaites, G E; Carrique-Mas, J J; Hoa, N T

    2016-04-01

    We investigated episodes of suspected highly pathogenic avian influenza (HPAI)-like illness among 12 meat duck flocks in two districts in Tien Giang province (Mekong Delta, Vietnam) in November 2013. In total, duck samples from 8 of 12 farms tested positive for HPAI virus subtype A/haemagglutinin 5 and neuraminidase 1 (H5N1) by real-time RT-PCR. Sequencing results confirmed clade of 2.3.2.1.c as the cause of the outbreaks. Most (7/8) laboratory-confirmed positive flocks had been vaccinated with inactivated HPAI H5N1 clade 2.3.4 vaccines <6 days prior to onset of clinical signs. A review of vaccination data in relation to estimated production in the area suggested that vaccination efforts were biased towards larger flocks and that vaccination coverage was low [21.2% ducks vaccinated with two shots (range by district 7.4-34.9%)]. The low-coverage data, the experimental evidence of lack of cross-protection conferred by the currently used vaccines based on clade 2.3.4 together with the short lifespan of meat duck flocks (60-70 days), suggest that vaccination is not likely to be effective as a tool for control of H5N1 infection in meat duck flocks in the area. PMID:26748550

  19. High levels of antimicrobial resistance among escherichia coli isolates from livestock farms and synanthropic rats and shrews in the Mekong Delta of Vietnam.

    PubMed

    Nhung, N T; Cuong, N V; Campbell, J; Hoa, N T; Bryant, J E; Truc, V N T; Kiet, B T; Jombart, T; Trung, N V; Hien, V B; Thwaites, G; Baker, S; Carrique-Mas, J

    2015-02-01

    In Mekong Delta farms (Vietnam), antimicrobials are extensively used, but limited data are available on levels of antimicrobial resistance (AMR) among Escherichia coli isolates. We performed a structured survey of AMR in E. coli isolates (n = 434) from 90 pig, chicken, and duck farms. The results were compared with AMR among E. coli isolates (n = 234) from 66 small wild animals (rats and shrews) trapped on farms and in forests and rice fields. The isolates were susceptibility tested against eight antimicrobials. E. coli isolates from farmed animals were resistant to a median of 4 (interquartile range [IQR], 3 to 6) antimicrobials versus 1 (IQR, 1 to 2) among wild mammal isolates (P < 0.001). The prevalences of AMR among farmed species isolates (versus wild animals) were as follows: tetracycline, 84.7% (versus 25.6%); ampicillin, 78.9% (versus 85.9%); trimethoprim-sulfamethoxazole, 52.1% (versus 18.8%); chloramphenicol, 39.9% (versus 22.5%); amoxicillin-clavulanic acid, 36.6% (versus 34.5%); and ciprofloxacin, 24.9% (versus 7.3%). The prevalence of multidrug resistance (MDR) (resistance against three or more antimicrobial classes) among pig isolates was 86.7% compared to 66.9 to 72.7% among poultry isolates. After adjusting for host species, MDR was ∼8 times greater among isolates from wild mammals trapped on farms than among those trapped in forests/rice fields (P < 0.001). Isolates were assigned to unique profiles representing their combinations of susceptibility results. Multivariable analysis of variance indicated that AMR profiles from wild mammals trapped on farms and those from domestic animals were more alike (R(2) range, 0.14 to 0.30) than E. coli isolates from domestic animals and mammals trapped in the wild (R(2) range, 0.25 to 0.45). The results strongly suggest that AMR on farms is a key driver of environmental AMR in the Mekong Delta. PMID:25398864

  20. High Levels of Antimicrobial Resistance among Escherichia coli Isolates from Livestock Farms and Synanthropic Rats and Shrews in the Mekong Delta of Vietnam

    PubMed Central

    Nhung, N. T.; Cuong, N. V.; Campbell, J.; Hoa, N. T.; Bryant, J. E.; Truc, V. N. T.; Kiet, B. T.; Jombart, T.; Trung, N. V.; Hien, V. B.; Thwaites, G.; Baker, S.

    2014-01-01

    In Mekong Delta farms (Vietnam), antimicrobials are extensively used, but limited data are available on levels of antimicrobial resistance (AMR) among Escherichia coli isolates. We performed a structured survey of AMR in E. coli isolates (n = 434) from 90 pig, chicken, and duck farms. The results were compared with AMR among E. coli isolates (n = 234) from 66 small wild animals (rats and shrews) trapped on farms and in forests and rice fields. The isolates were susceptibility tested against eight antimicrobials. E. coli isolates from farmed animals were resistant to a median of 4 (interquartile range [IQR], 3 to 6) antimicrobials versus 1 (IQR, 1 to 2) among wild mammal isolates (P < 0.001). The prevalences of AMR among farmed species isolates (versus wild animals) were as follows: tetracycline, 84.7% (versus 25.6%); ampicillin, 78.9% (versus 85.9%); trimethoprim-sulfamethoxazole, 52.1% (versus 18.8%); chloramphenicol, 39.9% (versus 22.5%); amoxicillin-clavulanic acid, 36.6% (versus 34.5%); and ciprofloxacin, 24.9% (versus 7.3%). The prevalence of multidrug resistance (MDR) (resistance against three or more antimicrobial classes) among pig isolates was 86.7% compared to 66.9 to 72.7% among poultry isolates. After adjusting for host species, MDR was ∼8 times greater among isolates from wild mammals trapped on farms than among those trapped in forests/rice fields (P < 0.001). Isolates were assigned to unique profiles representing their combinations of susceptibility results. Multivariable analysis of variance indicated that AMR profiles from wild mammals trapped on farms and those from domestic animals were more alike (R2 range, 0.14 to 0.30) than E. coli isolates from domestic animals and mammals trapped in the wild (R2 range, 0.25 to 0.45). The results strongly suggest that AMR on farms is a key driver of environmental AMR in the Mekong Delta. PMID:25398864

  1. Temporal and spatial assessment of river surface water quality using multivariate statistical techniques: a study in Can Tho City, a Mekong Delta area, Vietnam.

    PubMed

    Phung, Dung; Huang, Cunrui; Rutherford, Shannon; Dwirahmadi, Febi; Chu, Cordia; Wang, Xiaoming; Nguyen, Minh; Nguyen, Nga Huy; Do, Cuong Manh; Nguyen, Trung Hieu; Dinh, Tuan Anh Diep

    2015-05-01

    The present study is an evaluation of temporal/spatial variations of surface water quality using multivariate statistical techniques, comprising cluster analysis (CA), principal component analysis (PCA), factor analysis (FA) and discriminant analysis (DA). Eleven water quality parameters were monitored at 38 different sites in Can Tho City, a Mekong Delta area of Vietnam from 2008 to 2012. Hierarchical cluster analysis grouped the 38 sampling sites into three clusters, representing mixed urban-rural areas, agricultural areas and industrial zone. FA/PCA resulted in three latent factors for the entire research location, three for cluster 1, four for cluster 2, and four for cluster 3 explaining 60, 60.2, 80.9, and 70% of the total variance in the respective water quality. The varifactors from FA indicated that the parameters responsible for water quality variations are related to erosion from disturbed land or inflow of effluent from sewage plants and industry, discharges from wastewater treatment plants and domestic wastewater, agricultural activities and industrial effluents, and contamination by sewage waste with faecal coliform bacteria through sewer and septic systems. Discriminant analysis (DA) revealed that nephelometric turbidity units (NTU), chemical oxygen demand (COD) and NH₃ are the discriminating parameters in space, affording 67% correct assignation in spatial analysis; pH and NO₂ are the discriminating parameters according to season, assigning approximately 60% of cases correctly. The findings suggest a possible revised sampling strategy that can reduce the number of sampling sites and the indicator parameters responsible for large variations in water quality. This study demonstrates the usefulness of multivariate statistical techniques for evaluation of temporal/spatial variations in water quality assessment and management. PMID:25847419

  2. Evaluating sustainable adaptation strategies for vulnerable mega-deltas using system dynamics modelling: Rice agriculture in the Mekong Delta's An Giang Province, Vietnam.

    PubMed

    Chapman, Alexander; Darby, Stephen

    2016-07-15

    Challenging dynamics are unfolding in social-ecological systems around the globe as society attempts to mitigate and adapt to climate change while sustaining rapid local development. The IPCC's 5th assessment suggests these changing systems are susceptible to unforeseen and dangerous 'emergent risks'. An archetypal example is the Vietnamese Mekong Delta (VMD) where the river dyke network has been heightened and extended over the last decade with the dual objectives of (1) adapting the delta's 18 million inhabitants and their livelihoods to increasingly intense river-flooding, and (2) developing rice production through a shift from double to triple-cropping. Negative impacts have been associated with this shift, particularly in relation to its exclusion of fluvial sediment deposition from the floodplain. A deficit in our understanding of the dynamics of the rice-sediment system, which involve unintuitive delays, feedbacks, and tipping points, is addressed here, using a system dynamics (SD) approach to inform sustainable adaptation strategies. Specifically, we develop and test a new SD model which simulates the dynamics between the farmers' economic system and their rice agriculture operations, and uniquely, integrates the role of fluvial sediment deposition within their dyke compartment. We use the model to explore a range of alternative rice cultivation strategies. Our results suggest that the current dominant strategy (triple-cropping) is only optimal for wealthier groups within society and over the short-term (ca. 10years post-implementation). The model suggests that the policy of opening sluice gates and leaving paddies fallow during high-flood years, in order to encourage natural sediment deposition and the nutrient replenishment it supplies, is both a more equitable and a more sustainable policy. But, even with this approach, diminished supplies of sediment-bound nutrients and the consequent need to compensate with artificial fertilisers will mean that smaller

  3. The prevalence and genetic diversity of group A rotaviruses on pig farms in the Mekong Delta region of Vietnam

    PubMed Central

    Hong Anh, Pham; Carrique-Mas, Juan J.; Van Cuong, Nguyen; Hoa, Ngo Thi; Lam Anh, Nguyet; Duy, Do Tien; Hien, Vo Be; Vu Tra My, Phan; Rabaa, Maia A.; Farrar, Jeremy; Baker, Stephen; Bryant, Juliet E.

    2014-01-01

    Group A rotaviruses (ARoVs) are a common cause of severe diarrhea among children worldwide and the cause of approximately 45% of pediatric hospitalizations for acute diarrhea in Vietnam. ARoVs are known to cause significant economic losses to livestock producers by reducing growth performance and production efficiencies, however little is known about the implications of asymptomatic endemic circulation of ARoV. We aimed to determine the prevalence and predominant circulating genotypes of ARoVs on pig farms in a southern province of Vietnam. We found overall animal-level and farm-level prevalence of 32.7% (239/730) and 74% (77/104), respectively, and identified six different G types and 4 P types in various combinations (G2, G3, G4, G5, G9, G11 and P[6], P[13], P[23], and P[34]). There was no significant association between ARoV infection and clinical disease in pigs, suggesting that endemic asymptomatic circulation of ARoV may complicate rotavirus disease attribution during outbreaks of diarrhea in swine. Sequence analysis of the detected ARoVs suggested homology to recent human clinical cases and extensive genetic diversity. The epidemiological relevance of these findings for veterinary practitioners and to ongoing pediatric ARoV vaccine initiatives in Vietnam merits further study. PMID:24679960

  4. Assessing the potential of the multi-aquifer subsurface of the Mekong Delta (Vietnam) for land subsidence due to groundwater extraction

    NASA Astrophysics Data System (ADS)

    Minderhoud, P. S. J.; Erkens, G.; Pham, V. H.; Vuong, B. T.; Stouthamer, E.

    2015-11-01

    Land subsidence rates of ~ 1-4 cm yr-1 are measured in the low-lying Vietnamese Mekong Delta. These relatively high subsidence rates are attributed to groundwater extraction, which has increased drastically over the past decades due to growing domestic, agricultural and industrial demands. As a result, hydraulic heads in aquifers are dropping, on average 0.3-0.7 m yr-1. There is an urgent need to go from measurements to predictions in order to test possible future groundwater management scenarios and to reduce the increase of flood risk, salt water intrusion and, on the longer term, prevent the delta from drowning. In this study, we aim to assess the subsidence potential of the multi-aquifer subsurface of the Mekong delta due to groundwater extraction. The first step is to gain a thorough understanding of the complex sedimentary architecture of the heterogeneous subsurface. Combined with the related geotechnical properties, the subsurface build-up determines the subsidence potential. Here, we present our approach to develop a 3-D geo-hydrological model based on lithological borehole data, geophysical sedimentary properties, palaeogeography and conceptual models of delta evolution.

  5. Recent morphological changes in the Mekong and Bassac river channels, Mekong delta: The marked impact of river-bed mining and implications for delta destabilisation

    NASA Astrophysics Data System (ADS)

    Brunier, Guillaume; Anthony, Edward J.; Goichot, Marc; Provansal, Mireille; Dussouillez, Philippe

    2014-11-01

    The Mekong delta, in Vietnam, is the world's third largest delta. Densely populated, the delta has been significantly armoured with engineering works and dykes to protect populations and infrastructure from storms, and shrimp farms from saltwater intrusion. Considerable development pressures in Vietnam and in the upstream countries have resulted in the construction of several dams in China and in important channel-bed aggregate extractions especially in Cambodia. The effects of these developments impact the delta dynamics in various ways. In this study, changes in the channel morphology of the Mekong proper and the Bassac, the two main distributaries in the 250 km-long deltaic reach from the Cambodian border to the coast, were analysed using channel depth data for 1998 and 2008. The channels display important and irregular bed changes over the 10-year comparison period, including significant incision and expansion and deepening of numerous pools. The mean depth of both channels increased by more than 1.3 m. Both channels also showed correlative significant bed material losses: respectively 90 million m3 in the Mekong and 110 million m3 in the Bassac over the 10-year period. These important losses over a relatively short period, and weak correlations between bed incision and hydraulic parameters suggest that the marked morphological changes are not in equilibrium with flow and sediment entrainment conditions, and are therefore not related to changes in river hydrology. We claim that aggregate extraction, currently practised on a very large scale in the Mekong delta channels and upstream of the delta, is the main cause of these recent morphological changes. These changes are deemed to contribute actively to rampant bank erosion in the delta as well as to erosion of the Mekong delta shoreline. Other contributory activities include the numerous dykes and embankments. The role of existing dams in bed losses remains unclear in the absence of reliable data on the Mekong

  6. Dimensions of gender relations and reproductive health inequity perceived by female undergraduate students in the Mekong Delta of Vietnam: a qualitative exploration

    PubMed Central

    2012-01-01

    Introduction Increasing evidence indicates that gender equity has a significant influence on women’s health; yet few culturally specific indicators of gender relations exist which are applicable to health. This study explores dimensions of gender relations perceived by female undergraduate students in southern Vietnamese culture, and qualitatively examines how this perceived gender inequity may influence females’ sexual or reproductive health. Methods Sixty-two female undergraduate students from two universities participated in eight focus group discussions to talk about their perspectives regarding national and local gender equity issues. Results Although overall gender gaps in the Mekong Delta were perceived to have decreased in comparison to previous times, several specific dimensions of gender relations were emergent in students’ discussions. Perceived dimensions of gender relations were comparable to theoretical structures of the Theory of Gender and Power, and to findings from several reports describing the actual inferiority of women. Allocation of housework and social paid work represented salient dimensions of labor. The most salient dimension of power related to women in positions of authority. Salient dimensions of cathexis related to son preference, women’s vulnerability to blame or criticism, and double standards or expectations. Findings also suggested that gender inequity potentially influenced women’s sexual and reproductive health as regards to health information seeking, gynecological care access, contraceptive use responsibility, and child bearing. Conclusion Further investigations of the associations between gender relations and different women’s sexual and reproductive health outcomes in this region are needed. It may be important to address gender relations as a distal determinant in health interventions in order to promote gender-based equity in sexual and reproductive health. PMID:23095733

  7. Constant sediment budget of Mekong delta shorelines: implications from long-term shoreline changes

    NASA Astrophysics Data System (ADS)

    Tamura, T.; Saito, Y.; Nguyen, V. L.; Ta, T. K. O.

    2015-12-01

    The sustainability of delta shorelines requires the sufficient sediment supply that is equal to or more than the sediment removal by tides and waves. The Mekong River delta, southern Vietnam, is a mixed-energy, complicated system with multiple delta plain shorelines that share the sediment supply from the river. We reconstructed the long-term shoreline changes of the Mekong delta over the last 2500 years based on the architecture and chronology of beach ridges on three delta plain in Ben Tre (North, Central, and South Ben Tre), and a delta plain in Tra Vinh to consider the sediment flux and its contribution to the growth of individual delta plains. While each delta plain shows temporal changes in growth rate, the sum of these four plains is nearly constant. This implies that the net sediment supply to the shorelines is constant, and that the geomorphological changes at distributary branches cause changes in sediment supply to each shoreline compartment. The distributary between North and Central Ben Tre was choked sometime between 500 and 1000 years ago, causing the rapid and stagnant shoreline progradation in North and Central Ben Tre, respectively. The shoreline of Central Ben Tre however has prograded slowly even after the choking, suggesting the beach sand can be supplied beyond the distributary or onshore from the delta front. Pre-industrial changes in delta geomorphology, based on geological records, improve the understanding of the delta systems and when compared with historical changes, diagnose the post-industrial state of delta.

  8. Learning Environment in Vietnamese Physics Teacher Education Programme through the Lens of Constructivism: A Case Study of a State University in Mekong Delta Region, Vietnam

    ERIC Educational Resources Information Center

    Thao-Do, Thi Phuong; Bac-Ly, Dang Thi; Yuenyong, Chokchai

    2016-01-01

    Constructivism was introduced to Vietnam through many ways such as workshops, books, the Internet, and so on. However, due to the lack of professional education, fundamental ideas of constructivist learning perhaps were missing or neglected through classroom activities. Furthermore, due to the influence of culture and society, Vietnamese…

  9. Effects of Sequential Applications of Bassa 50EC (Fenobucarb) and Vitashield 40EC (Chlorpyrifos ethyl) on Acetylcholinesterase Activity in Climbing Perch (Anabas testudineus) Cultured in Rice Fields in the Mekong Delta, Vietnam.

    PubMed

    Tam, Nguyen Thanh; Berg, Håkan; Laureus, Jenny; Cong, Nguyen Van; Tedengren, Michael

    2016-07-01

    This study assesses the effects of sequential applications of the insecticides Bassa 50EC (fenobucarb-F) and Vitashield 40EC (chlorpyrifos ethyl-CPF), sprayed at concentrations used by rice farmers in the Mekong Delta, on the brain acetylcholinesterase (AChE) in climbing perch fingerlings. After spraying the pesticides on the rice fields, the water concentrations of both insecticides decreased below the detection levels within 3 days. The sequential applications caused significant inhibition on the brain AChE activity in the exposed fish. The inhibition by F was quicker, but less prolonged, than for CPF. The inhibition levels caused by the sequential applications were lower than those caused by only CPF and by a mixture of CPF and F. The results indicate that sequential applications of pesticides could have a negative impact on aquatic organisms and fish yields, with implication for the aquatic biodiversity, local people's livelihood and the aquaculture industry in the Mekong Delta. PMID:27075585

  10. Prevalence and risk factors for carriage of antimicrobial-resistant Escherichia coli on household and small-scale chicken farms in the Mekong Delta of Vietnam

    PubMed Central

    Nguyen, Vinh Trung; Carrique-Mas, Juan J.; Ngo, Thi Hoa; Ho, Huynh Mai; Ha, Thanh Tuyen; Campbell, James I.; Nguyen, Thi Nhung; Hoang, Ngoc Nhung; Pham, Van Minh; Wagenaar, Jaap A.; Hardon, Anita; Thai, Quoc Hieu; Schultsz, Constance

    2015-01-01

    Objectives To describe the prevalence of antimicrobial resistance among commensal Escherichia coli isolates on household and small-scale chicken farms, common in southern Vietnam, and to investigate the association of antimicrobial resistance with farming practices and antimicrobial usage. Methods We collected data on farming and antimicrobial usage from 208 chicken farms. E. coli was isolated from boot swab samples using MacConkey agar (MA) and MA with ceftazidime, nalidixic acid or gentamicin. Isolates were tested for their susceptibility to 11 antimicrobials and for ESBL production. Risk factor analyses were carried out, using logistic regression, at both the bacterial population and farm levels. Results E. coli resistant to gentamicin, ciprofloxacin and third-generation cephalosporins was detected on 201 (96.6%), 191 (91.8%) and 77 (37.0%) of the farms, respectively. Of the 895 E. coli isolates, resistance to gentamicin, ciprofloxacin and third-generation cephalosporins was detected in 178 (19.9%), 291 (32.5%) and 29 (3.2%) of the isolates, respectively. Ciprofloxacin resistance was significantly associated with quinolone usage (OR = 2.26) and tetracycline usage (OR = 1.70). ESBL-producing E. coli were associated with farms containing fish ponds (OR = 4.82). Conclusions Household and small farms showed frequent antimicrobial usage associated with a high prevalence of resistance to the most commonly used antimicrobials. Given the weak biocontainment, the high prevalence of resistant E. coli could represent a risk to the environment and to humans. PMID:25755000

  11. Association between climate factors and diarrhoea in a Mekong Delta area.

    PubMed

    Phung, Dung; Huang, Cunrui; Rutherford, Shannon; Chu, Cordia; Wang, Xiaoming; Nguyen, Minh; Nguyen, Nga Huy; Manh, Cuong Do; Nguyen, Trung Hieu

    2015-09-01

    The Mekong Delta is vulnerable to changes in climate and hydrological events which alter environmental conditions, resulting in increased risk of waterborne diseases. Research exploring the association between climate factors and diarrhoea, the most frequent waterborne disease in Mekong Delta region, is sparse. This study evaluated the climate-diarrhoea association in Can Tho city, a typical Mekong Delta area in Vietnam. Climate data (temperature, relative humidity, and rainfall) were obtained from the Southern Regional Hydro-Meteorological Centre, and weekly counts of diarrhoea visits were obtained from Can Tho Preventive Medicine Centre from 2004 to 2011. Analysis of climate and health variables was carried out using spline function to adjust for seasonal and long-term trends of variables. A distributed lag model was used to investigate possible delayed effects of climate variables on diarrhoea (considering 0-4 week lag periods), then the multivariate Poisson regression was used to examine any potential association between climate factors and diarrhoea. The results indicated that the diarrhoea incidence peaked within the period August-October annually. Significant positive associations were found between increased diarrhoea and high temperature at 4 weeks prior to the date of hospital visits (IRR = 1.07; 95 % CI = 1.04-1.08), high relative humidity (IRR = 1.13; 95 % CI = 1.12-1.15) and high (>90th percentile) cumulative rainfall (IRR = 1.05; 95 % CI = 1.05-1.08). The association between climate factors and diarrhoea was stronger in rural than urban areas. These findings in the context of the projected changes of climate conditions suggest that climate change will have important implications for residential health in Mekong Delta region. PMID:25472927

  12. Association between climate factors and diarrhoea in a Mekong Delta area

    NASA Astrophysics Data System (ADS)

    Phung, Dung; Huang, Cunrui; Rutherford, Shannon; Chu, Cordia; Wang, Xiaoming; Nguyen, Minh; Nguyen, Nga Huy; Manh, Cuong Do; Nguyen, Trung Hieu

    2015-09-01

    The Mekong Delta is vulnerable to changes in climate and hydrological events which alter environmental conditions, resulting in increased risk of waterborne diseases. Research exploring the association between climate factors and diarrhoea, the most frequent waterborne disease in Mekong Delta region, is sparse. This study evaluated the climate-diarrhoea association in Can Tho city, a typical Mekong Delta area in Vietnam. Climate data (temperature, relative humidity, and rainfall) were obtained from the Southern Regional Hydro-Meteorological Centre, and weekly counts of diarrhoea visits were obtained from Can Tho Preventive Medicine Centre from 2004 to 2011. Analysis of climate and health variables was carried out using spline function to adjust for seasonal and long-term trends of variables. A distributed lag model was used to investigate possible delayed effects of climate variables on diarrhoea (considering 0-4 week lag periods), then the multivariate Poisson regression was used to examine any potential association between climate factors and diarrhoea. The results indicated that the diarrhoea incidence peaked within the period August-October annually. Significant positive associations were found between increased diarrhoea and high temperature at 4 weeks prior to the date of hospital visits (IRR = 1.07; 95 % CI = 1.04-1.08), high relative humidity (IRR = 1.13; 95 % CI = 1.12-1.15) and high (>90th percentile) cumulative rainfall (IRR = 1.05; 95 % CI = 1.05-1.08). The association between climate factors and diarrhoea was stronger in rural than urban areas. These findings in the context of the projected changes of climate conditions suggest that climate change will have important implications for residential health in Mekong Delta region.

  13. Vulnerability of climate change and its adaptation in the Mekong Delta: monitoring and resident's perception along the coast

    NASA Astrophysics Data System (ADS)

    Tamura, M.; Yasuhara, K.

    2014-12-01

    The Mekong Delta in Vietnam is expected to face challenges from various forms of climate-induced events. In addition, a growing population, which currently stands at 18.6 million people lives in the Mekong Delta, Vietnam. Therefore, the Mekong Delta is the focus of international action for adaptation. However, many climate sensitive regions and communities are unprepared for climate-induced natural disasters due to mismatch in perception with their respective risks. This study examines the vulnerability and appropriate adaptation in the Mekong Delta from both scientific and regional aspects. First, we show the change in coastal areas in Soc Trang province, comparing the past to the present images using Unmanned Aerial Vehicle (UAV) and satellite. We identify some vulnerable areas which derived from multiple factors due to coastal erosion, flooding, and sea level rise. Second, we present results of perception survey about climate change and the adaptation at community level in Ca Mau, Soc Trang, and An Giang Provinces, which were conducted in 2012 and 2014. While the findings suggest varying degrees of adaptation to seasonal flooding by raising the ground floors of their homes and repairing houses, their capacity to prepare for extreme flooding is limited in spite of the residents' awareness of the increasing frequency and intensity of natural disasters. Third, we propose an erosion-resistant dyke reinforcement technique by mixing natural palm tree fiber and cement, both of which are locally available materials in the Mekong Delta. It is expected that adaptation with multiple protections in accordance to regional feature can work well for such coastal disasters.

  14. Monitoring rice farming activities in the Mekong Delta region

    NASA Astrophysics Data System (ADS)

    Nguyen, S. T.; Chen, C. F.; Chen, C. R.; Chiang, S. H.; Chang, L. Y.; Khin, L. V.

    2015-12-01

    Half of the world's population depends on rice for survival. Rice agriculture thus plays an important role in the developing world's economy. Vietnam is one of the largest rice producers and suppliers on earth and more than 80% of the exported rice was produced from the Mekong Delta region, which is situated in the southwestern Vietnam and encompasses approximately 40,000 km2. Changes in climate conditions could likely trigger the increase of insect populations and rice diseases, causing the potential loss of rice yields. Monitoring rice-farming activities through crop phenology detection can provide policymakers with timely strategies to mitigate possible impacts on the potential yield as well as rice grain exports to ensure food security for the region. The main objective of this study is to develop a logistic-based algorithm to investigate rice sowing and harvesting activities from the multi-temporal Moderate Resolution Imaging Spectroradiometer (MODIS)-Landsat fusion data. We processed the data for two main cropping seasons (i.e., winter-spring and summer-autumn seasons) through a three-step procedure: (1) MODIS-Landsat data fusion, (2) construction of the time-series enhanced vegetation index 2 (EVI2) data, (3) rice crop phenology detection. The EVI2 data derived from the fusion results between MODIS and Landsat data were compared with that of Landsat data indicated close correlation between the two datasets (R2 = 0.93). The time-series EVI2 data were processed using the double logistic method to detect the progress of sowing and harvesting activities in the region. The comparisons between the estimated sowing and harvesting dates and the field survey data revealed the root mean squared error (RMSE) values of 8.4 and 5.5 days for the winter-spring crop and 9.4 and 12.8 days for the summer-autumn crop, respectively. This study demonstrates the effectiveness of the double logistic-based algorithm for rice crop monitoring from temporal MODIS-Landsat fusion data

  15. Crop Uptake of Arsenic from Flooded Paddy Fields in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Mohr, K.; Boye, K.

    2014-12-01

    Arsenic is found naturally in the soils in the Mekong delta in Vietnam and Cambodia. It originates from erosion in the Himalayas. When similar levels of arsenic are present in well aerated soil, it is not dangerous, because it is strongly bound to soil particles and not readily plant available. Arsenic is released when the soil is saturated with water, and therefore contaminates crops grown in flooded fields. This results in people being exposed to unsafe levels of arsenic from their food, such as rice and lotus, which are normally grown under flooded conditions. Rice is a staple food in these regions, so the transfer of arsenic from soil, to water, and ultimately into the grain, poses a threat to human health. We have conducted a limited, preliminary field survey of arsenic levels in soil, flood water, and crops from distinctly different paddy fields in the lower Mekong delta in Vietnam and Cambodia. The purpose of the study was to identify soils and crops (or specific plant parts) that are especially prone to arsenic transfer from soil to crop, and vice versa (i.e. arsenic uptake is prevented in spite of being present in the soil). In addition to arsenic concentration in soil, plant and water, we are examining other elements, such as carbon, nitrogen, sulfur and iron, which give us clues about what chemical and microbial processes that control the overall arsenic uptake.

  16. Tide and river influences on distributary channels of the Mekong River delta

    NASA Astrophysics Data System (ADS)

    Saito, Y.; Nguyen, V. L.; Ta, T. K. O.; Tamura, T.; Kanai, Y.; Nakashima, R.

    2015-12-01

    The Mekong River delta, one of the world's largest deltas, has extended from Phnom Penh in Cambodia (apex) to the coast from the Saigon River mouth to Cape Camau in Vietnam with a triangular-shape area of more than 60,000 km2. The delta has prograded more than 200 km over at least the last 6-7 ka. The river-mouth area of the delta is meso-tidal with the mean tidal range of 2.5 ± 0.1 m and the maximum tidal range is 3.2-3.8 m. The mean wave height is 0.9 m. Its water discharge is 470 km3/y and its sediment discharge is 160 million t/y, or tenth and ninth largest in the world, respectively. The water discharge varies by season because most of the drainage area is under a monsoonal tropical regime. The flow at Phnom Penh, Cambodia, reaches a maximum in October (typically 39,000 m3/s) and a minimum in May (about 1700 m3/s). Tidal water-level changes are observed in Cambodia, more than 200 km upstream from the river mouth. To understand the combined influenced of river and tide on river bottom sediments, we have collected ~210 surface samples from river bottoms of the whole Mekong River delta in Vietnam, covering five distributaries during dry season from January to May 2015. Sediment characteristics show clearly tide- and river-influenced areas, which are closely linked with river morphology.

  17. Responding to rising sea levels in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Smajgl, A.; Toan, T. Q.; Nhan, D. K.; Ward, J.; Trung, N. H.; Tri, L. Q.; Tri, V. P. D.; Vu, P. T.

    2015-02-01

    Vietnamese communities in the Mekong Delta are faced with the substantial impacts of rising sea levels and salinity intrusion. The construction of embankments and dykes has historically been the principal strategy of the Vietnamese government to mitigate the effects of salinity intrusion on agricultural production. A predicted sea-level rise of 30 cm by the year 2050 is expected to accelerate salinity intrusion. This study combines hydrologic, agronomic and behavioural assessments to identify effective adaptation strategies reliant on land-use change (soft options) and investments in water infrastructure (hard options). As these strategies are managed within different policy portfolios, the political discussion has polarized between choices of either soft or hard options. This paper argues that an ensemble of hard and soft policies is likely to provide the most effective results for people's livelihoods in the Mekong Delta. The consequences of policy deliberations are likely to be felt beyond the Mekong Delta as levels of rice cultivation there also affect national and global food security.

  18. Recent morphodynamic evolution of coastline of Mekong river Delta, towards an increased vulnerability

    NASA Astrophysics Data System (ADS)

    Besset, Manon; Brunier, Guillaume; Anthony, Edward

    2015-04-01

    river delta and generate considerable risks to residents. Thus, nearly 12,000 people were evacuated from the Giang region in 2014 (Vietnam News, 2014) as a result of coastal erosion. This growing vulnerability related to erosion is combined with the problems of subsidence and susceptibility to flooding which are already rendering the Mekong river delta one of the most vulnerable and threatened deltas (Syvitski et al., 2009).

  19. Large-scale suspended sediment transport and sediment deposition in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Manh, N. V.; Dung, N. V.; Hung, N. N.; Merz, B.; Apel, H.

    2014-08-01

    Sediment dynamics play a major role in the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains, and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment deposition in the whole Mekong Delta. To this end, a quasi-2D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for 2 validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition is differentiated from Kratie at the entrance of the delta on its way to the coast. The main factors influencing the spatial sediment dynamics are the river and channel system, dike rings, sluice gate operations, the magnitude of the floods, and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, annual sediment loads reaching the coast vary from 48 to 60% of the sediment load at Kratie. Deposited sediment varies from 19 to 23% of the annual load at Kratie in Cambodian floodplains, and from 1 to 6% in the compartmented and diked floodplains in Vietnam. Annual deposited nutrients (N, P, K), which are associated with the sediment deposition, provide on average more than 50% of mineral fertilizers typically applied for rice crops in non-flooded ring dike floodplains in Vietnam. Through the quantification of sediment and related nutrient input, the presented study provides a quantitative basis for

  20. Association between annual river flood pulse and paediatric hospital admissions in the Mekong Delta area.

    PubMed

    Phung, Dung; Huang, Cunrui; Rutherford, Shannon; Chu, Cordia; Wang, Xiaoming; Nguyen, Minh

    2014-11-01

    The Mekong Delta is the most vulnerable region to extreme climate and hydrological conditions however the association between these conditions and children's health has been little studied. We examine the association between annual river flood pulse and paediatric hospital admissions in a Vietnam Mekong Delta city. Daily paediatric hospital admissions (PHA) were collected from the City Paediatric Hospital, and daily river water level (RWL) and meteorological data were retrieved from the Southern Regional Hydro-Meteorological Centre from 2008 to 2011. We evaluated the association between annual river flood pulse (>=90th percentile of RWL) and PHA using the Poisson distributed lag model, controlling for temperature, relative humidity, day of week, seasonal and long-term trends. The seasonal pattern of PHA was examined using harmonic and polynomial regression models. The cumulative risk ratios estimated for a 15-day period following an extreme RWL was 1.26 (95%CI, 1.2-1.38) for all age groups, 1.27 (95%CI, 1.23-1.30) for under five-years and 1.15 (95%CI, 1.07-1.20) for school-aged children, 1.24 (95%CI, 1.21-1.27) for all-causes, 1.18 (95%CI, 1.12-1.21) for communicable infection, 1.66 (95%CI, 1.57-1.74) for respiratory infection and 1.06 (95%CI, 1.01-1.1) for other diseases. The peak PHA risk is in the September-October period corresponding to the highest RWL, and the PHA-RWL association was modified by temperature. An increase in PHA is significantly associated with annual river flood, and the pattern of PHA is seasonally correspondent to the RWL. These findings combined with projected changes in climate conditions suggest important implications of climate change for human health in the Mekong Delta region. PMID:25282279

  1. Changes in Ecosystem Services and related Livelihoods in the Mekong Delta: vulnerabilities and adaptation strategies

    NASA Astrophysics Data System (ADS)

    Sebesvari, Z.; Renaud, F. G.

    2014-12-01

    The Mekong Delta (Vietnam) is highly vulnerable to the many impacts of global environmental change as well as to the accelerating anthropogenic changes in the catchment and in the delta itself. Today the delta is an agricultural landscape controlled by engineering structures such as channels, dykes, embankments, and sluice gates. These structures have been constructed gradually over the last 200 years mainly for irrigation and flood control in the upper part of the delta and to control saline intrusion in the coastal areas. Recent changes in the hydrology mainly driven by upstream hydropower development on the mainstream and the tributaries of the Mekong will likely have far reaching impacts on the delta´s social-ecological systems through changes in e.g. sedimentation processes, nutrient transport as well as the health of aquatic ecosystems. Further threats to the delta include sea level rise and an increase in seasonal rainfall variability leading to an increase in flood variability. These changes affect the lives of millions of low-income inhabitants who depend on the ecosystem services provided by the Mekong for their livelihoods and sustenance. Since the changes in ecosystem service provision are occurring relatively fast while the resource dependency of the delta population is very high, adaptation becomes a challenge. An assessment of livelihood dependencies on ecosystem services requires an understanding of ecosystem services affected by different drivers of change, as well as of the types of livelihoods likely to be jeopardized as a result of these changes. We will present main ecosystem services supporting specific livelihoods, discuss how they are threatened, and analyse the merits of potential solutions. Options based solely on grey infrastructure might be problematic on the long term while an integration of ecosystem based solution such as a (re)adaptation of agricultural production systems to floods in the upper delta might be a more sustainable

  2. Extreme floods in the Mekong River Delta under climate change: combined impacts of upstream hydrological changes and sea level rise

    NASA Astrophysics Data System (ADS)

    Hoang, Long; Nguyen Viet, Dung; Kummu, Matti; Lauri, Hannu; Koponen, Jorma; van Vliet, Michelle T. H.; Supit, Iwan; Leemans, Rik; Kabat, Pavel; Ludwig, Fulco

    2016-04-01

    Extreme floods cause huge damages to human lives and infrastructure, and hamper socio-economic development in the Mekong River Delta in Vietnam. Induced by climate change, upstream hydrological changes and sea level rise are expected to further exacerbate future flood hazard and thereby posing critical challenges for securing safety and sustainability. This paper provides a probabilistic quantification of future flood hazard for the Mekong Delta, focusing on extreme events under climate change. We developed a model chain to simulate separate and combined impacts of two drivers, namely upstream hydrological changes and sea level rise on flood magnitude and frequency. Simulation results show that upstream changes and sea level rise substantially increase flood hazard throughout the whole Mekong Delta. Due to differences in their nature, two drivers show different features in their impacts on floods. Impacts of upstream changes are more dominant in floodplains in the upper delta, causing an increase of up to +0.80 m in flood depth. Sea level rise introduces flood hazard to currently safe areas in the middle and coastal delta zones. A 0.6 m rise in relative sea level causes an increase in flood depth between 0.10 and 0.70 m, depending on location by 2050s. Upstream hydrological changes and sea level rise tend to intensify each other's impacts on floods, resulting in stronger combined impacts than linearly summed impacts of each individual driver. Substantial increase of future flood hazard strongly requires better flood protection and more flood resilient development for the Mekong Delta. Findings from this study can be used as quantified physical boundary conditions to develop flood management strategies and strategic delta management plans.

  3. Future flood hazard under climate change in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Apel, H.; Dung, N. V.; Delgado, J. M.; Merz, B.

    2012-04-01

    The main characteristic of flood hazard estimations is the association of a probability of occurrence to a flood event of a defined magnitude. This is usually performed via frequency analysis assuming stationarity and independence of the analyzed time series. This assumption, however, often does not hold true even for historical records and periods and it will be even more challenged under the expected impact of climate change to the water cycle in general and flood probabilities and magnitudes in particular. Thus strategies and methods have to be developed and evaluated for accounting for climate change impacts on flood hazard. In the presented contribution two options are presented and compared for the Mekong Delta, one of the most endangered areas with respect to climate change world-wide. The first method takes non-stationarity explicitly into account by analyzing the observed time series of peak discharge and flood volume at the upper boundary of the Delta with non-stationary extreme value statistics. The two variables and their dependence are modeled by a copula, coupling their marginal distributions to a joint bivariate distribution. Using this copula in combination with characteristic normalized flood hydrographs, probabilistic flood hazard maps for the Mekong Delta are generated via a large scale hydrodynamic model of the Delta embedded in a Monte Carlo framework for the reference year 2009. In order to account for climate change the observed trend in the non-stationary extreme value distribution was simply extrapolated to two future time horizons 2030 and 2050. However, the extrapolations of the trends are certainly associated with high level of uncertainty, in particular for time horizons in the far future. Thus we compare the simple extrapolation approach with an approach deriving future flood hazard in the Mekong Delta by establishing direct correlations between monsoon indexes describing the intensity of the flood triggering monsoon activities and the

  4. Structure of the Mekong trough

    SciTech Connect

    Van Khy, L.

    1986-01-01

    The Mekong trough occupies the shelf of southern Vietnam between the sea coast and the Condao-Cu Lao Tu line of islands and the adjacent area of the onshore Mekong delta. It extends for 400 km from southwest to northeast with a width of 100 km. The Mekong trough is situated on the upper Mesozoic volcanic belt of South Vietnam, which is part of the East Asian volcanogenic belt. It is bounded on the southeast by the Con Son high, on the southwest by the Corat-Ca Mau high, and on the northwest by the Dalat massif. The Mekong trough is considered to have major potential as a new petroleum province. Since 1969, numerous common depth point (CDP) seismic profiles have been run and seven deep wells have been drilled on the shelf in the Mekong trough. This paper is devoted to an analysis of the findings. 9 references, 4 figures.

  5. Detection of Area Changes in River Mouthbars at the Mekong River Delta using ALOS/PALSAR data

    NASA Astrophysics Data System (ADS)

    Tanaka, A.; Uehara, K.; Tamura, T.; Saito, Y.

    2011-12-01

    Projected sea-level rise by the year 2100 would be ~1m recently and its negative impact on the coastal zone has been pointed out, particularly for mega-deltas in Asia by the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC, 2007). The relative sea-level rise varies with specific conditions and processes over broad spatial and temporal scales. Therefore, long-term monitoring of geomorphological changes in coastal areas over wide areas is of highly interest and importance for coastal management. However, due to limited data availability and accessibility in developing countries, there is not enough systematic coastal monitoring. The Mekong River Delta is one of typical mega-deltas in Asia, which has a low-lying wide delta-plain located in Cambodia to South Vietnam. Sediment and water discharges of the Mekong River are controlled by the monsoon with high and low discharge in summer (wet season) and winter (dry season), respectively. Therefore, technologies such as SAR (Synthetic Aperture Radar) not affected by the cloud conditions offer potential for monitoring in the monsoon Asia region. In this study, ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band SAR) data acquired over a period from December 2006 to January 2011 are analyzed to investigate the relation between the sea level and the shape of mouthbars in the Mekong River. Level-1.0 PALSAR data were processed, coregistered, and geocoded to make SAR backscatter intensity images. River mouthbars with strong backscatter, which is surrounded by the water with weak backscatter, are successfully extracted using a histogram thresholding algorithm. Estimated areas of river mouthbars, which are located at the central part of the delta and openly faced to the South China Sea, gradually increase on an annual time scale. These river mouthbars are growing to the seaward. Besides this overall increasing trend, seasonal variations of areas are observed; these correlate with

  6. Monitoring and modeling the fate of commonly used pesticides in surface water of the Lower Mekong Delta

    NASA Astrophysics Data System (ADS)

    van Toan, Pham; Sebesvari, Zita; Loan, Vo Phuong Hong; Renaud, Fabrice

    2010-05-01

    , Vietnam. Marine Pollution Bulletin 56, 1476-1485. Dasgupta S., Meisner C., Wheeler D., Nhan L. T., Khuc X., 2005. Pesticide poisoning of farm workers: implications of blood test results from Vietnam. World Bank Policy Research Working Paper 3624. Dung, N.H., Dung, T.T., 2003. Economic and health consequences of pesticide use in paddy production in the Mekong Delta, Vietnam. Economy and environment case studies in Vietnam. Economy and environment program for Southeast Asia. Margni, M., Rossier, D., Crettaz, P., Jolliet, O., 2002. Life cycle impact assessment of pesticides on human health and ecosystems. Agriculture, Ecosystems and Environment 93, 379-392. Mekong River Committee Secretariat (MRCS), 2007. Environmental health concerns related to agro-chemical use in the Mekong Delta. Environment training case studies. Minh, N. H., Minh, T. B., Kajiwara, N., Kunisue, T., Iwata, H., Viet P.H., Tu, N. P. C., Tuyen, B. C., Tanabe, S., 2007. Pollution sources and occurrences of selected persistent organic pollutants (POPs) in sediments of the Mekong River delta, South Vietnam. Chemosphere. 67, 1794-1801. Phuong, D. M., Gopalakrishnan, C., 2003. An application of the contingent valuation method to estimate the loss of value of water resources due to pesticide contamination: the case of the Mekong Delta, Vietnam',International. Journal of Water Resources Development,19, 617-633.

  7. Floods in Mekong Delta Under Sea-Level Rise Projections By IPCC AR5

    NASA Astrophysics Data System (ADS)

    Takagi, H.

    2014-12-01

    One of the mightiest rivers in the planet, the Mekong ranks 10th amongst the world's great rivers on the basis of mean annual flow at the mouth. It flows southwards over a distance of approximately 4,800 km from its source to the sea, through six different countries: China, Myanmar, Lao PDR, Thailand, Cambodia and Vietnam. This great basin has been considered to be one of the most sensitive areas in the world to climate change. The present paper investigates fluvial flood hazards in urban areas in the Mekong Delta to inundation due to seasonal flooding, a phenomenon which is likely to be exacerbated by future sea-level rise. Unlike past researches which mainly focus on flooding due to river discharge from upstream or heavy precipitation, the present paper scrutinizes the influence of ocean tides. The research reveals that ocean tides predominantly determine water elevation even in an upstream location such as Can Tho City, 80 km inland from the river mouth, and that the river flow causes tidal damping and effectively reduces the energy of the incoming tides. This tidal damping is especially pronounced during the rainy season. Analysis based on the water levels monitored by the Mekong River Commission reveals that the ground near the riverbank of Can Tho had experienced inundation for a total of 215 hours between July 2009 and June 2010 (2.5% of the time over a one year period). It is also shown that inundation reached up to a maximum height of 47 cm above the roads of Can Tho downtown in this one-year period. Assuming two scenarios of sea-level rise of 25 cm in the middle of the 21st century and 60 cm in the end of the century, all based on the Fifth Assessment Report of Intergovernmental Panel on Climate Change (IPCC AR5) projections, it was found that the duration of inundation will be prolonged from the present percentage of 2.5% to 7.5% and 24% of the year, respectively. It is important to note that while at present this flooding is seasonal and limited, in the

  8. Low Carbon Rice Farming Practices in the Mekong Delta Yield Significantly Higher Profits and Lower Greenhouse Gas Emissions

    NASA Astrophysics Data System (ADS)

    Rudek, J.; Van Sanh, N.; Tinh, T. K.; Tin, H. Q.; Thu Ha, T.; Pha, D. N.; Cui, T. Q.; Tin, N. H.; Son, N. N.; Thanh, H. H.; Kien, H. T.; Kritee, K.; Ahuja, R.

    2014-12-01

    The Vietnam Low-Carbon Rice Project (VLCRP) seeks to significantly reduce GHG emissions from rice cultivation, an activity responsible for more than 30% of Vietnam's overall GHG emissions, while improving livelihoods for the rice farmer community by decreasing costs and enhancing yield as well as providing supplemental farmer income through the sale of carbon credits. The Mekong Delta makes up 12% of Vietnam's land area, but produces more than 50% of the country's rice, including more than 90% of the rice for export. Rice cultivation is the main source of income for 80% of farmers in the Mekong Delta. VLCRP was launched in late 2012 in the Mekong Delta in two major rice production provinces, Kien Giang and An Giang. To date, VLCRP has completed 11 crop seasons (in Kien Giang and An Giang combined), training over 400 farmer households in applying VLCRP's package of practices (known as 1 Must - 6 Reductions) and building technical capacity to its key stakeholders and rice farmer community leaders. By adopting the 1 Must- 6 Reductions practices (including reduced seeding density, reduced fertilizer and pesticide application, and alternative wetting and drying water management), rice farmers reduce their input costs while maintaining or improving yields, and decreasing greenhouse gas emissions. The VLCRP package of practices also deliver other environmental and social co-benefits, such as reduced water pollution, improved habitat for fishery resources and reduced health risks for farmers through the reduction of agri-chemicals. VLCRP farmers use significantly less inputs (50% reduction in seed, 30% reduction in fertilizer, 40-50% reduction in water) while improving yields 5-10%, leading to an increase in profit from 10% to as high as 60% per hectare. Preliminary results indicate that the 1 Must- 6 Reductions practices have led to approximately 40-65% reductions in greenhouse gas emissions, equivalent to 4 tons of CO2e/ha/yr in An Giang and 35 tons of CO2e/ha/yr in Kien

  9. From Risk Towards Resilience: Assessing Vulnerability and Adaptability to Climate Change in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Ling, F. H.; Yasuhara, K.; Tamura, M.; Tabayashi, Y.

    2012-12-01

    While efforts to mainstream climate adaptation have only begun in recent years, many developing regions are already taking measures to proof themselves from various natural disasters, including storm surges, flooding, land subsidence, and erosion. In the Asia-Pacific region, one of the most vulnerable in the world, climate resilience is urgently needed due to sea level rise and the increasing frequency and intensity of climate events. Yet, many regions and communities are unprepared due to insufficient awareness of disaster risks. In order to utilize the science of the changing environment more effectively, there is a critical need to understand the social context and perception of those who are affected by climate change. Using the Mekong Delta region in Vietnam as an example, we discuss our current efforts to develop a vulnerability and adaptation index for building climate resilience in the Asia-Pacific Region. A survey of current adaptation efforts in this region will be shown and preliminary findings from our survey to understand the perception of disaster risk in this region will be discussed.

  10. Flood precautionary behaviour of private households in Can Tho city in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Kreibich, Heidi; Gani Adnan, Sarfaraz; Thi Chinh, Do; Bubeck, Philip

    2015-04-01

    Flood risk is high and it is projected to increase in many places due to the effects of climate change and the on-going intensification of human activities in risk-prone areas. These projections and the considerable uncertainties associated with these developments increasingly require integrated approaches in flood risk management. In addition to flood protection, private precautionary measures aim at reducing the potential negative consequences of floods. Thus, insights into flood precautionary behaviour are important. This study is grounded on the Protection Motivation Theory (PMT), which refers to the cognitive process that people undergo when evaluating their own ability to avoid a certain risk. Results of a survey among 858 flood-prone households in Can Tho city in the Mekong Delta, Vietnam are presented. It is shown that flood-coping appraisal is an important variable in terms of precautionary behaviour. Thus, risk communication should focus more on the potential of precautionary measures to effectively reduce flood damage, as well as on information about how to implement such measures in practice.

  11. Integrated flood risk assessment for the Mekong Delta through the combined assessment of flood hazard change and social vulnerability

    NASA Astrophysics Data System (ADS)

    Apel, Heiko; Garschagen, Matthias; Delgado, José Miguel; Viet Dung, Nguyen; Van Tuan, Vo; Thanh Binh, Nguyen; Birkmann, Joern; Merz, Bruno

    2013-04-01

    Low lying estuaries as the Mekong Delta in Vietnam are among the most vulnerable areas with respect to climate change impacts. While regular floods are not a threat but an opportunity for livelihoods and income generation, extreme flood events can pose considerable risks to the people living in Deltas. Climate change is expected to increase the frequency of extreme floods globally, which in combination with sea level rise and a likely intensification of cyclone activity creates increased and/or entirely new hazard exposure in the Deltas. Yet, in line with the risk literature and especially the recent IPCC SREX report, flooding risk needs to be understood as deriving from the interaction of physical hazards and the vulnerabilities of exposed elements. Therefore, the paper aims for an integrated risk assessment through combining the most up to date estimates of flood hazard projections under climate change conditions in the Mekong Delta with the assessment of vulnerability patterns. Projections of flood hazard are estimated based the modulation of the flood frequency distribution by atmospheric circulation patterns. Future projections of these patterns are calculated from an ensemble of climate models. A quasi two-dimensional hydrodynamical model of the Delta is then applied to estimate water levels and flood extend. This model is fed with a set of hydrographs which are based on both the derived climate model uncertainty and the bivariate nature of floods in the Mekong Delta. Flood peak is coupled with flood volume in the probabilistic framework to derive synthetic extreme future floods with associated probabilities of occurrence. This flood hazard analysis is combined with static sea level rise scenarios, which alter the lower boundary of the hydrodynamic model and give estimates of the impact on sea level rise on inundation extend and depths. The vulnerability assessment is based on a three step approach. Firstly, vulnerability profiles are developed for different

  12. Science implementation of Forecast Mekong for food and environmental security

    USGS Publications Warehouse

    Turnipseed, D. Phil

    2012-01-01

    Forecast Mekong is a significant international thrust under the Delta Research and Global Observation Network (DRAGON) of the U.S. Geological Survey (USGS) and was launched in 2009 by the U.S. Department of State and the Foreign Ministers of Cambodia, Laos, Thailand, and Vietnam under U.S. Department of State Secretary Hillary R. Clinton's Lower Mekong Initiative to enhance U.S. engagement with countries of the Lower Mekong River Basin in the areas of environment, health, education, and infrastructure. Since 2009, the USGS has worked closely with the U.S. Department of State; personnel from Cambodia, Laos, Thailand, and Vietnam; nongovernmental organizations; and academia to collect and use research and data from the Lower Mekong River Basin to provide hands-on results that will help decisionmakers in future planning and design for restoration, conservation, and management efforts in the Lower Mekong River Basin. In 2012 Forecast Mekong is highlighting the increasing cooperation between the United States and Lower Mekong River Basin countries in the areas of food and environmental security. Under the DRAGON, Forecast Mekong continues work in interactive data integration, modeling, and visualization system by initiating three-dimensional bathymetry and river flow data along with a pilot study of fish distribution, population, and migratory patterns in the Lower Mekong River Basin. When fully developed by the USGS, in partnership with local governments and universities throughout the Mekong River region, Forecast Mekong will provide valuable planning tools to visualize the consequences of climate change and river management.

  13. A study of the climate change impacts on fluvial flood propagation in the Vietnamese Mekong Delta

    NASA Astrophysics Data System (ADS)

    Van, P. D. T.; Popescu, I.; van Griensven, A.; Solomatine, D. P.; Trung, N. H.; Green, A.

    2012-12-01

    The present paper investigated the extent of the flood propagation in the Vietnamese Mekong Delta under different projected flood hydrographs, considering the 2000 flood event (the 20-yr return period event, T. V. H. Le et al., 2007) as the basis for computation. The analysis herein was done to demonstrate the particular complexity of the flood dynamics, which was simulated by the 1-D modelling system ISIS used by the Mekong River Commission. The floods of the year 2050 are simulated using a projected sea level rise of +30 cm. The future flood hydrograph changes at Kratie, Cambodia, were also applied for the upstream boundary condition by using an adjusted regional climate model. Two future flood hydrographs were applied at the upstream part of the delta, the first one in a scenario of climate change without considering developments in the Mekong Basin,and the second one in a scenario of climate change taking into account future development of the delta. Analyses were done to identify the areas sensitive to floods, considering the uncertainty of the projection of both the upstream and downstream boundary conditions. In addition, due to the rice-dominated culture in the Vietnamese Mekong Delta, possible impacts of floods on the rice-based farming systems were also analysed.

  14. Effect of Environmental Factors on the Relationship between Concentrations of Coprostanol and Fecal Indicator Bacteria in Tropical (Mekong Delta) and Temperate (Tokyo) Freshwaters

    PubMed Central

    Isobe, Kei O.; Tarao, Mitsunori; Chiem, Nguyen H.; Minh, Le Y.; Takada, Hideshige

    2004-01-01

    A reliable assessment of microbial indicators of fecal pollution (total coliform, Escherichia coli, and fecal streptococcus) is critical in tropical environments. Therefore, we investigated the relationship between concentrations of indicator bacteria and a chemical indicator, coprostanol (5β-cholestan-3β-ol), in tropical and temperate regions. Water samples were collected from the Mekong Delta, Vietnam, during wet and dry seasons, and from Tokyo, Japan, during summer, the aftermath of a typhoon, and winter. During the wet season in the Mekong Delta, higher bacterial densities were observed in rivers, probably due to the higher bacterial inputs from soil particles with runoff. In Tokyo, higher bacterial densities were usually observed during summer, followed by those in the typhoon aftermath and winter. A strong logarithmic correlation between the concentrations of E. coli and coprostanol was demonstrated in all surveys. Distinctive seasonal fluctuations were observed, as concentrations of coprostanol corresponding to 1,000 CFU of E. coli/100 ml were at their lowest during the wet season in the Mekong Delta and the typhoon aftermath in Tokyo (30 ng/liter), followed by the dry season in the Mekong Delta and the summer in Tokyo (100 ng/liter), and they were much higher during the winter in Tokyo (400 ng/liter). These results suggested that E. coli is a specific indicator of fecal contamination in both tropical and temperate regions but that the densities are affected by elevated water temperature and input from runoff of soil particles. The concurrent determination of E. coli and coprostanol concentrations could provide a possible approach to assessing the reliability of fecal pollution monitoring data. PMID:14766559

  15. Is a Decline in Tropical Storms Leading to the Demise of the Mekong Delta?

    NASA Astrophysics Data System (ADS)

    Darby, S. E.; Hackney, C. R.; Leyland, J.; Kummu, M.; Lauri, H.; Parsons, D. R.; Best, J.; Nicholas, A. P.; Aalto, R. E.

    2015-12-01

    The world's largest rivers deliver ~19 billion tonnes of sediment to the coastal zone annually, with a significant fraction sequestered in the large deltas that are home to 14% of the world's population. Most (>70%) of these large deltas are under threat from a combination of rising sea levels and ground surface subsidence, while the rivers that feed them have also been subjected to damming, substantially reducing the sediment supply that is available for delta (re)construction. In this paper we use new measurements of suspended sediment load, combined with hydrological modelling, to reconstruct inter-annual variations in sediment load with and without tropical cyclones during the period 1981-2005. We examine in particular the results at Kratie in Cambodia, a gauging station that is located within 250 km of the apex of the Mekong delta. Our results indicate that fluvial sediment loads at Kratie have undergone a large and rapid decline (at a rate of ~2 Mt/yr, reducing the annual sediment load in this period by ~50%) during the study period. This is a remarkable finding, but we also show that this decline in sediment load is attributable almost entirely to a commensurate decline in the proportion of the Mekong's sediment load that is forced by tropical storms. Our results have profound implications. The Mekong's great delta, the rice basket of SE Asia, is home to 17 million people. A sustainable supply of fluvial sediment is critical in preventing the Mekong's delta being 'drowned' by rising sea levels. In recent years attention has been focused on the likely deleterious effects of hydropower dam construction in the Mekong Basin on the future sediment loads reaching the delta. However, it is evident that the delivery of sediment from the Mekong River has already undergone a substantial reduction, similar in magnitude to that associated with future dam-induced trapping, as a result of recent changes in tropical storm climatology. A continuing dearth of tropical storms

  16. Estimating residents' willingness to pay for groundwater protection in the Vietnamese Mekong Delta

    NASA Astrophysics Data System (ADS)

    Vo, Danh Thanh; Huynh, Khai Viet

    2014-11-01

    Groundwater in the Vietnamese Mekong Delta is facing the pollution and it needs to be protected. Searching literature reviews on economic valuation techniques, the contingent valuation method (CVM) has been popularly applied to estimate the economic value of water protection. This approach is based on a hypothetical scenario in which respondents are requested through questionnaires to reveal their maximum willingness to pay (WTP) for the water protection project. The study used the approach of CVM to analyze the households' motivations and their WTP for the program of groundwater protection in the Mekong Delta. The study performed that the residents in the delta were willing to pay approximately 141,730 VND (US6.74) per household a year. Groundwater could be an inferior good with the negative income effect found in the demanding for clean groundwater. Respondent's gender and groundwater-related health risk consideration were factors sensitively affecting the probability of demanding for groundwater protection.

  17. Two-year intervention trial to control of fish-borne zoonotic trematodes in giant gourami (Osphronemus goramy) and striped catfish (Pangasianodon hypophthalmus) in nursery ponds in the Mekong Delta, Vietnam.

    PubMed

    Madsen, H; Thien, P C; Nga, H T N; Clausen, J H; Dalsgaard, A; Murrell, K D

    2015-12-01

    Fish-borne zoonotic trematode parasites (FZT) pose a food safety and public health problem in Vietnam. The transmission cycle is complex as domestic animals, especially dogs, cats, fish-eating birds and pigs together with humans serve as reservoir hosts and contribute to FZT egg contamination of aquaculture ponds and the environment. This intervention trial was conducted to determine the effectiveness of various on-farm interventions, including reduction in FZT egg contamination through treatment of infected people and domestic animals, reduction in snail density through mud removal from aquaculture ponds prior to fish stocking, and various other measures in reducing FZT infection in juvenile striped catfish (Pangasianodon hypophthalmus) and giant gourami (Osphronemus goramy). Interventions were implemented on 5 farms for each fish species during production cycles in 2009 and 2010 while 5 similar farms for each species served as control. For both fish species, both prevalence and intensity of infection did not differ significantly between intervention and non-intervention farms prior to the interventions. The interventions significantly reduced both prevalence and intensity of FZT infection in the juvenile fish compared to control ponds. For giant gourami, odds of infection in intervention ponds was 0.13 (95% CL: 0.09-0.20; p<0.001) of that in non-intervention ponds after the 2009 trial and 0.07 (0.03-0.14; p<0.001) after the 2010 trial. For striped catfish, these figures were 0.17 (0.08-0.35; p<0.001) after the 2009 trial while after the 2010 trial all ponds with interventions were free from infection. Metacercariae intensity (no. of metacercariae/fish) in giant gourami from intervention ponds was 0.16 (0.11-0.23; p<0.001) of that in fish from non-intervention ponds after the 2009 trial and 0.07 (0.04-0.15; p<0.001) after the 2010 trial; for striped catfish these figures were 0.18 (0.09-0.36; p<0.001) and 0.00 (confidence limits not estimated), respectively. The

  18. Seasonality, disease and behavior: using multiple methods to explore socio-environmental health risks in the Mekong Delta.

    PubMed

    Few, Roger; Lake, Iain; Hunter, Paul R; Tran, Pham Gia

    2013-03-01

    Any analysis of how changing environmental hazards impact on public health is fundamentally constrained unless it recognizes the centrality of the social and behavioral dimensions of risk. This paper reports on a research project conducted among low-income peri-urban households in the Mekong Delta of Vietnam. The research was based on cross-disciplinary inputs to develop a multi-layered understanding of the implications of a dynamic seasonal environment for diarrheal disease risk. It is a widely held assumption that the major changes in the abundance of surface water between the flood and dry seasons in the Mekong Delta are likely to be reflected in the changing patterns of disease risk, especially for poorer households that tend to rely heavily on river water for domestic water use. Therefore, this study investigated seasonal patterns in the contamination of environmental water, incidences of diarrheal illnesses, water use and hygiene behavior, together with perceptions of health risks and seasonality. During the period of October 2007 to October 2008, the UK and Vietnamese research team worked with a total of 120 households in four low-income sites around the city of Long Xuyen to conduct water testing; administer questionnaires on self-reported health, risk perceptions and behavior; and conduct semi-structured interviews. The research team found no overall evidence of a systematic seasonal risk pattern. At the population level, marginal temporal variations in water quality in the environment failed to translate into health outcomes. A complex risk narrative emerged from the interweaving data elements, demonstrating major inter- and intra-household variations in risk perceptions, hygiene behavior, seasonal behavior and other risk factors. It is suggested that these complexities of human behavior and transmission routes challenge simplistic assumptions about change in health outcomes as a result of seasonal environmental changes. These findings demonstrate the key

  19. Large-scale quantification of suspended sediment transport and deposition in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Manh, N. V.; Dung, N. V.; Hung, N. N.; Merz, B.; Apel, H.

    2014-04-01

    Sediment dynamics play a major role for the agricultural and fishery productivity of the Mekong Delta. However, the understanding of sediment dynamics in the Mekong Delta, one of the most complex river deltas in the world, is very limited. This is a consequence of its large extent, the intricate system of rivers, channels and floodplains and the scarcity of observations. This study quantifies, for the first time, the suspended sediment transport and sediment-nutrient deposition in the whole Mekong Delta. To this end, a quasi-2-D hydrodynamic model is combined with a cohesive sediment transport model. The combined model is calibrated automatically using six objective functions to represent the different aspects of the hydraulic and sediment transport components. The model is calibrated for the extreme flood season in 2011 and shows good performance for the two validation years with very different flood characteristics. It is shown how sediment transport and sediment deposition vary from Kratie at the entrance of the Delta to the coast. The main factors influencing the spatial sediment dynamics are the setup of rivers, channels and dike-rings, the sluice gate operations, the magnitude of the floods and tidal influences. The superposition of these factors leads to high spatial variability of sediment transport, in particular in the Vietnamese floodplains. Depending on the flood magnitude, the annual sedimentation rate averaged over the Vietnamese floodplains varies from 0.3 to 2.1 kg m-2 yr-1, and the ring dike floodplains trap between 1 and 6% of the total sediment load at Kratie. This is equivalent to 29 × 103-440 × 103 t of nutrients (N, P, K, TOC) deposited in the Vietnamese floodplains. This large-scale quantification provides a basis for estimating the benefits of the annual Mekong floods for agriculture and fishery, and is important information for assessing the effects of deltaic subsidence and climate change related sea level rise.

  20. Linking rapid erosion of the Mekong River delta to human activities.

    PubMed

    Anthony, Edward J; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-01-01

    As international concern for the survival of deltas grows, the Mekong River delta, the world's third largest delta, densely populated, considered as Southeast Asia's most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river's discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams. PMID:26446752

  1. Linking rapid erosion of the Mekong River delta to human activities

    PubMed Central

    Anthony, Edward J.; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-01-01

    As international concern for the survival of deltas grows, the Mekong River delta, the world’s third largest delta, densely populated, considered as Southeast Asia’s most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river’s discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams. PMID:26446752

  2. Linking rapid erosion of the Mekong River delta to human activities

    NASA Astrophysics Data System (ADS)

    Anthony, Edward J.; Brunier, Guillaume; Besset, Manon; Goichot, Marc; Dussouillez, Philippe; Nguyen, Van Lap

    2015-10-01

    As international concern for the survival of deltas grows, the Mekong River delta, the world’s third largest delta, densely populated, considered as Southeast Asia’s most important food basket, and rich in biodiversity at the world scale, is also increasingly affected by human activities and exposed to subsidence and coastal erosion. Several dams have been constructed upstream of the delta and many more are now planned. We quantify from high-resolution SPOT 5 satellite images large-scale shoreline erosion and land loss between 2003 and 2012 that now affect over 50% of the once strongly advancing >600 km-long delta shoreline. Erosion, with no identified change in the river’s discharge and in wave and wind conditions over this recent period, is consistent with: (1) a reported significant decrease in coastal surface suspended sediment from the Mekong that may be linked to dam retention of its sediment, (2) large-scale commercial sand mining in the river and delta channels, and (3) subsidence due to groundwater extraction. Shoreline erosion is already responsible for displacement of coastal populations. It is an additional hazard to the integrity of this Asian mega delta now considered particularly vulnerable to accelerated subsidence and sea-level rise, and will be exacerbated by future hydropower dams.

  3. Peat formation concentrates arsenic within sediment deposits of the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Stuckey, Jason W.; Schaefer, Michael V.; Kocar, Benjamin D.; Dittmar, Jessica; Pacheco, Juan Lezama; Benner, Shawn G.; Fendorf, Scott

    2015-01-01

    Mekong River Delta sediment bears arsenic that has been released to groundwater under anaerobic conditions over the past several thousand years. The oxidation state, speciation, and distribution of arsenic and the associated iron bearing phases are crucial determinants of As reactivity in sediments. Peat from buried mangrove swamps in particular may be an important host, source, or sink of arsenic in the Mekong Delta. The total concentration, speciation, and reactivity of arsenic and iron were examined in sediments in a Mekong Delta wetland by X-ray fluorescence spectrometry (XRF), X-ray absorption spectroscopy (XAS), and selective chemical extractions. Total solid-phase arsenic concentrations in a peat layer at a depth of 6 m below ground increased 10-fold relative to the overlying sediment. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that arsenic in the peat was predominantly in the form of arsenian pyrite. Arsenic speciation in the peat was examined further at the micron-scale using μXRF and μX-ray absorption near-edge structure (XANES) spectroscopy coupled with principal component analysis. The multiple energy μXRF mapping and μXANES routine was repeated for both iron and sulfur phase analyses. Our μXRF/μXANES analyses confirm arsenic association with pyrite - a less reactive host phase than iron (hydr)oxides under anaerobic conditions. The arsenian pyrite likely formed upon deposition/formation of the peat in a past estuarine environment (∼5.5 ka BP), a process that is not expected under current geochemical conditions. Presently, arsenian pyrite is neither a detectable source nor a sink for aqueous arsenic in our sediment profile, and under present geochemical conditions represents a stable host of As under the reducing aquifer conditions of the Mekong Delta. Furthermore, organic carbon within the peat is unable to fuel Fe(III) reduction, as noted by the persistence of goethite which can be reduced microbially with the

  4. Sediment dynamics in the Mekong Delta: impacts of planned hydropower development, climate change and sea level rise

    NASA Astrophysics Data System (ADS)

    Van Manh, Nguyen; Viet Dung, Nguyen; Nghia Hung, Nguyen; Kummu, Matti; Merz, Bruno; Apel, Heiko

    2016-04-01

    The Mekong Delta is under threat due to human activities endangering the livelihood of millions of people. Hydropower development, climate change and the combined effects of sea level rise and deltaic subsidence are the main drivers impacting future flow regimes, sedimentation patterns and erosion in the Mekong Delta. In order to estimate the individual and combined impacts of the different drivers sensitivity-based scenario simulations were performed. The hydraulic processes and the sediment transport and deposition in the Mekong delta including the Tonle Sap Lake was simulated with a quasi-2D hydrodynamic for a baseline (2000-2010) and a future (2050-2060) period. For each driver a plausible range of future states was determined based on existing literature and studies. The ranges were discretized into different levels, resulting in 216 combinations of driver combinations. The results thus cover all plausible future pathways of sediment dynamics in the delta based on current knowledge. The results indicate that hydropower development dominates the changes in floodplain sediment dynamics of the Mekong Delta, while sea level rise has the smallest effect. The floodplains of the Vietnamese Mekong Delta are much more sensitive to the changes compared to other subsystems of the delta. The median changes of the three drivers combined indicate that the inundation extent would increase slightly, but the overall floodplain sedimentation would decrease by approximately 40%, and the suspended sediment load to the South China Sea would diminish to half of the current rates. The maximum changes in all drivers would mean a nearly 90% reduction of delta sedimentation, and a 95% reduction of the suspended sediment reaching the sea. These findings provide new and valuable information on the possible future development of floodplain hydraulics and sedimentation in the Mekong Delta, and identify the areas that are most vulnerable to these changes. This, in turn, provides a

  5. Mekong Floods Fill Tonle Sap

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The monsoon season in Southeast Asia brings recurring, often devastating floods to countries in the region, but these floods also play a necessary role in the region's water cycle. These MODIS images centered on Cambodia reveal extensive flooding of the Mekong River, which comes in from Laos in the north, to the right of center in the images, and flows south through Cambodia and southeast through Vietnam to empty into the South China Sea. The true-color image shows the brownish, sediment-laden floodwaters filling the Mekong Delta in southern Cambodia and Vietnam on September 15, 2001. The false color image above has been enhanced to bring out the contrast between the floodwaters and the lands, with sediment-carrying floodwaters in purple. Sediment can be seen flowing into the South China Sea as well. This year's floods have affected over a million people, and 100 people have been killed in Vietnam alone. The monsoon floods bring not only devastation, but renewal. The large body of water just left of center in Cambodia is the Tonle Sap. This shallow lake plays a changing role in the regional water cycle. During the dry season, the stream-fed Tonle Sap drains via the Tonle Sab River into the Mekong River. During the wet season (June-November), flooding of the Mekong reverses the course of the Tonle Sab, roughly tripling the lake's size from about 3000 km2 to about 10,000. When the dry season returns, the lake once again begins to drain into the Mekong Delta, where it provides a flow of fresh water that balances the intrusion of salty seawater into the delta's agricultural lands. Image courtesy Jacques Descloitres, MODIS Land Rapid Response Team at NASA GSFC

  6. Forecast Mekong

    USGS Publications Warehouse

    Turnipseed, D. Phil

    2011-01-01

    Forecast Mekong is part of the U.S. Department of State's Lower Mekong Initiative, which was launched in 2009 by Secretary Hillary Clinton and the Foreign Ministers of Cambodia, Laos, Thailand, and Vietnam to enhance partnerships between the U.S. and the Lower Mekong River countries in the areas of environment, health, education, and infrastructure. The U.S. Geological Survey (USGS) is working in close cooperation with the U.S. Department of State to use research and data from the Lower Mekong Basin to provide hands-on results that will help decision makers in Lower Mekong River countries in the planning and design for restoration, conservation, and management efforts in the basin.

  7. Forecast Mekong: 2011 update

    USGS Publications Warehouse

    Turnipseed, D. Phil

    2011-01-01

    In 2009, U.S. Secretary of State Hillary R. Clinton joined with the Foreign Ministers of Cambodia, Laos, Thailand, and Vietnam in launching the Lower Mekong Initiative to enhance U.S. engagement with the Lower Mekong countries in the areas of environment, health, education, and infrastructure. Part of the Lower Mekong Initiative, the U.S. Geological Survey's Forecast Mekong project is engaging the United States in scientific research relevant to environmental issues in the Lower Mekong River countries and is staying the course in support of the Mekong Nations with a suite of new projects for 2011.

  8. Future sediment dynamics in the Mekong Delta floodplains: Impacts of hydropower development, climate change and sea level rise

    NASA Astrophysics Data System (ADS)

    Manh, Nguyen Van; Dung, Nguyen Viet; Hung, Nguyen Nghia; Kummu, Matti; Merz, Bruno; Apel, Heiko

    2015-04-01

    The Mekong Delta is under threat due to human activities that are endangering livelihood of millions of people. Hydropower development, climate change and the combined effects of sea level rise and deltaic subsidence are the main drivers impacting future flow regimes and sedimentation patterns in the Mekong Delta. We develop a sensitivity-based approach to assess the response of the floodplain hydrology and sediment dynamics in the delta to these drivers. A quasi-2D hydrodynamic model of suspended sediment dynamics is used to simulate the sediment transport and sediment deposition in the delta, including Tonle Sap Lake, for a baseline (2000-2010) and a future (2050-2060) period. For each driver we derive a plausible range of future states and discretize it into different levels, resulting in 216 combinations. Our results thus cover all plausible future pathways of sediment dynamics in the delta based on current knowledge. Our results indicate that hydropower development dominates the changes in floodplain sediment dynamics of the Mekong Delta, while sea level rise has the smallest effect. The floodplains of the Vietnamese Mekong Delta are much more sensitive to the changes compared to the other subsystems of the delta. The median changes of the three drivers combined indicate that the inundation extent would increase slightly, but the overall floodplain sedimentation would decrease by approximately 40%, and the sediment load to the South China Sea would diminish to half of the current rates. The maximum changes in all drivers would mean a nearly 90% reduction of delta sedimentation and a 95% reduction of the sediment reaching the sea. Our findings provide new and valuable information on the possible future development of floodplain hydraulics and sedimentation in the Mekong Delta and identify the areas that are most vulnerable to these changes.

  9. A study of the climate change impacts on fluvial flood propagation in the Vietnamese Mekong Delta

    NASA Astrophysics Data System (ADS)

    Dang Tri, V. P.; Popescu, I.; van Griensven, A.; Solomatine, D.; Trung, N. H.; Green, A.

    2012-06-01

    The present paper investigated what would be the flood propagation in the Vietnamese Mekong Delta (VMD), due to different projected climate change scenarios, if the 2000 flood event (the most recent highest flood in the history) was taken as a base for computation. The analysis herein was done to demonstrate the particular complexity of the flood dynamics. The future floods, on short term horizon, year 2050, were studied by considering the projected sea level rise (SLR) (+30 cm). At the same time, future flood hydrograph changes at Kratie, Cambodia were applied for the upstream boundary condition. In this study, the future flood hydrograph was separated into two scenarios in which: (i) Scenario 1 was projected in 2050 according to the adjusted regional climate model without any development in the Upper Mekong Basin; and, (ii) Scenario 2 was projected as in Scenario 1 but with the development of the Upper Mekong Basin after 2030. Analyses were done to identify the high sensitive areas in terms of flood conditions (i.e. with and without flood) according to the uncertainty of the projection of both the upstream and downstream boundary conditions. In addition, due to the rice-dominated culture in the VMD, possible impacts of flood on the rice-based farming systems were analysed.

  10. Population dynamics of shrimps in littoral marine waters of the Mekong Delta, south of Viet Nam.

    PubMed

    Dinh, T D; Moreau, J; Van, M V; Phuong, N T; Toan, V T

    2010-07-15

    The population dynamics of eight commercial species of shrimp (Haliporoides sibogae, Harpiosquilla harpax, Metapenaeus affinis, Metapenaeus brevicornis, Metapenaeus tenuipes, Parapenaeopsis cultrirostris, Parapenaeopsis gracillima and Parapenaeus maxilipedo) distributed in littoral marine zone of the Mekong Delta were investigated. Length-based stock assessment using FiSAT II software package was used to assess the growth and mortality parameters: Asymptotic size (L8), growth coefficient (K), total (Z) and natural (M) mortality, exploitation rate (E), recruitment pattern, current probability of capture and selectivity of fishing gears. Yield-per-recruit analyses were carried out showing different levels of the exploitation. Results showed that the maximum sustainable yield would be reached for an exploitation rate higher than the current one for each population. However, the size of first capture should be increased for every population. The findings indicated that the current exploitations of shrimp populations distributed in littoral marine zone of the Mekong Delta are under exploitation level for maximum sustainable yield; however, all the shrimp populations are subject to growth over-exploitation. PMID:21848060

  11. Arsenic Concentrations in Rice and Associated Health Risks Along the Upper Mekong Delta, Cambodia

    NASA Astrophysics Data System (ADS)

    Barragan, L.; Seyfferth, A.; Fendorf, S.

    2011-12-01

    The consumption of arsenic contaminated food, such as rice, can be a significant portion of daily arsenic exposure, even for populations already exposed through drinking water. While arsenic contamination of rice grains has been documented in parts of Southern Asia, (e.g. Bangladesh), little research has been conducted on arsenic contamination of Cambodian-grown rice. We collected rice plant samples at various locations within the upper Mekong River Delta near Phnom Penh, Cambodia, and we analyzed total arsenic concentrations in plant digests of grains, husk, and straw. In addition, we used CaCl2-, DTPA-, and oxalate-extractable arsenic to define plant-available soil pools. We found variability of arsenic concentration in the plants, with grain arsenic ranging from 0.046 to 0.214 μg g-1; other researchers have shown that concentrations higher than 0.1 μg g-1 could be a concern for human health. Although more extensive sampling is needed to assess the risk of arsenic exposure from rice consumption on a country-wide basis, our work clearly illustrates the risk within regions of the Mekong Delta.

  12. Vietnamese Women in Academic Leadership: Experiences of Mid-Level Women Leaders in Universities and Colleges in the Mekong Delta

    ERIC Educational Resources Information Center

    Dang, Ngoc Lan Thi

    2012-01-01

    Academic women in the Mekong Delta (MD) in southern Viet Nam remain underrepresented in key leadership positions and other positions of power and influence in their institutions. This situation exists regardless of various local, national, and international policies on gender equality and the implementation of numerous action plans, strategies,…

  13. 2500 years of changing shoreline accretion rates at the mouths of the Mekong River delta

    NASA Astrophysics Data System (ADS)

    Besset, Manon; Tamura, Toru; Anthony, Edward; Brunier, Guillaume; Saito, Yoshiki; Dussouillez, Philippe; Lap Nguyen, Van; Ta, Oahn

    2016-04-01

    The Mekong River delta prograded rapidly in a relatively sheltered bight in the South China Sea under the influence of high fluvial sediment supply 5300 to 3500 years ago, developing from an estuary into a delta. This >200 km seaward growth resulted in increasing exposure of the delta to ocean waves that led to a more wave-influenced mode of progradation characterized by the construction of numerous sets of beach ridges in the eastern sector of the delta, which shows a system of multiple distributary mouths. The growth pattern of this river-mouth sector over the last 2500 years has been determined from OSL dating of these beach-ridge deposits, while the most up-to-date trends (1950-2014) have been highlighted from the analysis of maps and satellite images. The OSL ages show that the area of the delta in the mouths sector remained nearly constant till about 500 yr BP, following which significant accretion occurred, possibly in response to changes in catchment land-use and monsoon rainfall and attendant river water and sediment discharge. A fine-tuned analysis of changes since 1950 shows dominant but fluctuating accretion, with two periods of erosion. The first (1965-1973) occurred in the course of the second Indochina war, and the second more recently from 2003 to 2011, followed by mild recovery between 2011 and 2014. These fluctuations most likely reflect changes in sediment supply caused by the vicissitudes of war and its effect on vegetation cover, as well as variations in monsoon rainfall and discharge, and, for the most recent period, massive sand mining in the river and deltaic channels. Accretion of the mouths sector has gone apace, over the same recent multi-decadal period, with large-scale erosion of the muddy shores of the delta in the western South China Sea and the Gulf of Thailand, thus suggesting that the mouths sector may be increasingly sequestering sediment to the detriment of the rest of the delta shoreline. The accretion in the mouths sector is

  14. Determining the solid phases hosting arsenic in Mekong Delta sediments

    NASA Astrophysics Data System (ADS)

    Wucher, M.; Stuckey, J. W.; McCurdy, S.; Fendorf, S.

    2011-12-01

    The major river systems originating from the Himalaya deposit arsenic bearing sediment into the deltas of South and Southeast Asia. High rates of sediment and organic carbon deposition combined with frequent flooding leads to anaerobic processes that release arsenic into the pore-water. Arsenic concentrations in the groundwater of these sedimentary basins are often above the World Health Organization drinking water standard of 10 μg As L-1. As a result, 150 million people are at risk of chronic arsenic poisoning through water and rice consumption. The composition of the iron bearing phases hosting the arsenic in these deltaic sediments is poorly understood. Here we implemented a suite of selective chemical extractions to help constrain the types of arsenic bearing solid phases, which were complimented with synchrotron-based X-ray absorption spectroscopy and X-ray diffraction analyses to define the arsenic and iron mineralogy of the system. Sediment cores were collected in triplicate from a seasonally-inundated wetland in Cambodia at depths of 10, 50, 100, and 150 centimeters. We hypothesize that (i) arsenic will be predominantly associated with iron oxides, and (ii) the ratio of crystalline to amorphous iron oxides will increase with sediment depth (and age). We performed four selective extractions in parallel to quantify the various pools of arsenic. First, 1 M MgCl2 was used to extract electrostatically-bound arsenic (labile forms) from the sediment. Second, 1 M NaH2PO4 targeted strongly adsorbed arsenic. Third, 1 M HCl was used to liberated arsenic coprecipitated with amorphous Fe/Mn oxides, carbonates, and acid-volatile sulfides. Finally, a dithionite extraction was used to account for arsenic associated with reducible Fe/Mn oxides. Through this work, we identified the composition of the phases hosting arsenic at various depths through the soil profile, improving our understanding of how arsenic persists in the aquifer. In addition, defining the arsenic and

  15. Water turbidity mapping using Landsat-8 data in Mekong and Bassac Rivers, Vietnam

    NASA Astrophysics Data System (ADS)

    Lau, Va-Khin; Chen, Chi-Farn; Nguyen, Thanh-Son; Lam, Dao-Nguyen; Chen, Cheng-Ru

    2016-04-01

    Turbidity is the cloudiness or haziness measured by the intensity of light scattered through a water sample and turbidity is often used as an indicator of water quality. Traditional studies of water turbidity are often implemented through costly and time-consuming field surveys, and water samples are analyzed in the laboratory. This method can be applied for a small region. However, the method often creates limitation due to the time bias of data collection, interpolation error, and cost when applied to a large region. In recent year, remote sensing technologies have proved the capacity of mapping turbidity or suspended solids by various data sources, including aerial photography, high resolution images (e.g., Spot, Formosat) and medium resolution images (e.g., Landsat), and low resolution images (e.g., MODIS, MERIS, and VIIR). The main of this study is to investigate the applicability of Landsat data for water turbidity mapping in Mekong and Bassac Rivers, Vietnam. The length of these two main rivers is approximately 210 km with the width ranging from 500 m to 5 km. Aerial photos and high resolution images (e.g., IKONOS, QuickView) are good candidates for this water turbidity monitoring purpose. However, it is costly. Low resolution images such as MODIS are relatively coarse, given the width of rivers in some areas smaller than 500 m. The Landsat 8 satellite launched in 2013 provides the multispectral data with seven bands and 30 m resolution, which are deemed suitable for water turbidity monitoring in the study region, and thus used in this study. The data were processed by first converting the digital number of each pixel to radiance. The atmospheric correction using FLAASH model was accordingly applied to generate surface reflectance data. We used the Bayesian model average (BMA) to investigate the relationship between Landsat spectral bands and field survey data, which were collected from 63 sites of 21 transects across the two rivers on 24 January 2015

  16. Understanding transitions in rice paddy extent and management in the Vietnamese Mekong River Delta using Landsat data

    NASA Astrophysics Data System (ADS)

    Kontgis, C. P.; Schneider, A.; Ozdogan, M.

    2014-12-01

    Rice is a staple food crop for the majority of the world's population, yet paddy fields are threatened by urban expansion, climate change, and degraded agricultural land. For example, Vietnam, the second largest exporter of rice globally, grows most of its rice in the Mekong River Delta at the country's southern tip, yet this low-lying and heavily populated area is proving susceptible to land cover changes in the area. To properly monitor and manage the rice crops in this region, remote sensing of satellite imagery has been particularly useful; however, most efforts to map regional paddy area utilize coarse resolution MODIS or AVHRR data since the high temporal resolution of these datasets can overcome missing data issues due to clouds. Here, we aim to map the landscape using finer-scale Landsat data by generating dense time stacks over multiple growing seasons. First, we exploit dense stacks of data for circa 2000 and circa 2010 to classify rice using vegetation trajectories (EVI and NDWI). Next, these pixel-based rice maps are combined with image-based segments (generated using the open-source Mean-shift region-growing segmentation algorithm, which has been proven to optimally identify clusters within an image) to generate a polygon-based rice map using the majority rule. Results show that this method can map rice paddy agriculture with over 90% accuracy at a much finer spatial resolution than has ever been produced. Finally, this work also aims to differentiate between double- and triple-cropped rice paddies in the region, again by exploiting EVI trajectories, in an effort to determine how management practices have changed over the decade-long study period. Increasing the number of annual cropping cycles over the area can lead to soil degradation and lower yields per harvest, albeit larger total annual yields, so monitoring these practices is vital to understanding the sustainability of these agricultural systems.

  17. Potential collaboration with the private sector for the provision of ambulatory care in the Mekong region, Vietnam

    PubMed Central

    Duc, Ha Anh; Sabin, Lora L.; Cuong, Le Quang; Thien, Duong Duc; Feeley, Rich

    2012-01-01

    Background Over the past two decades, health insurance in Vietnam has expanded nationwide. Concurrently, Vietnam's private health sector has developed rapidly and become an increasingly integral part of the health system. To date, however, little is understood regarding the potential for expanding public-private partnerships to improve health care access and outcomes in Vietnam. Objective To explore possibilities for public-private collaboration in the provision of ambulatory care at the primary level in the Mekong region, Vietnam. Design We employed a mixed methods research approach. Qualitative methods included focus group discussions with health officials and in-depth interviews with managers of private health facilities. Quantitative methods encompassed facility assessments, and exit surveys of clients at the same private facilities. Results Discussions with health officials indicated generally favorable attitudes towards partnerships with private providers. Concerns were also voiced, regarding the over- and irrational use of antibiotics, and in terms of limited capacity for regulation, monitoring, and quality assurance. Private facility managers expressed a willingness to collaborate in the provision of ambulatory care, and private providers facilites were relatively well staffed and equipped. The client surveys indicated that 80% of clients first sought treatment at a private facility, even though most lived closer to a public provider. This choice was motivated mainly by perceptions of quality of care. Clients who reported seeking care at both a public and private facility were more satisfied with the latter. Conclusions Public-private collaboration in the provision of ambulatory care at the primary level in Vietnam has substantial potential for improving access to quality services. We recommend that such collaboration be explored by Vietnamese policy-makers. If implemented, we strongly urge attention to effectively managing such partnerships, establishing a

  18. Monitoring and modeling the fate of commonly used pesticides in surface water of the Lower Mekong Delta

    NASA Astrophysics Data System (ADS)

    van Toan, Pham; Sebesvari, Zita; Loan, Vo Phuong Hong; Renaud, Fabrice

    2010-05-01

    Introduction: The Lower Mekong Delta, one of the largest agricultural areas in Southeast Asia, has been reported to be increasingly polluted by agrochemicals since the beginning of the transformation processes in Vietnamese economy and specifically in the agricultural sector in 1986 (MRCS, 2007; Dasgupta et al., 2005; Dung, 2003; Phuong, 2003). Although pesticides have contributed significantly to enhancing agricultural productivity, these agrochemicals also have created risks to human health and environment (Margni, 2001; Phuong, 2003; Dasgupta et al., 2005) and lead to value loss of water resources (Phuong, 2003). While prohibited persistent organic pollutants such as HCHs and DDTs, were monitored and still detected in the Lower Mekong Delta in recent studies (Minh et al., 2007, Carvalho et al., 2008) little data exist on water pollution by recently used pesticides in the Delta. Aiming to fill this information gap, a study comprising three components was set up at two study sites of the Delta. Pesticide use and management was investigated through surveys and participatory rural appraisals with farmers; pesticide residue concentrations were determined in field outflows, connected irrigation canals and in drinking water and finally pesticide fate was predicted by using a coupled MIKE 11/ MIKE SHE model. This abstract focuses on the work done in the field of pesticide monitoring. The western study site (An Long Commune, Dong Thap province) represented an agricultural pattern with two intensive paddy rice crops per year and was heavily affected by flood in the rainy season. The second site located in the central part of the Delta (Ba Lang ward, Can Tho City) was characterized by a mix of paddy rice, vegetables and fruit trees. Fifteen pesticide compounds (buprofezin, butachlor, cypermethrin, difenozonazol, α-endosulfan, β-endosulfan, endosulfan-sulfate, fenobucarb, fipronil, hexaconazol, isoprothiolane, pretilachlor, profenofos, propanil, and propiconazol) were

  19. Arsenic release metabolically limited to permanently water-saturated soil in Mekong Delta

    NASA Astrophysics Data System (ADS)

    Stuckey, Jason W.; Schaefer, Michael V.; Kocar, Benjamin D.; Benner, Shawn G.; Fendorf, Scott

    2016-01-01

    Microbial reduction of arsenic-bearing iron oxides in the deltas of South and Southeast Asia produces widespread arsenic-contaminated groundwater. Organic carbon is abundant both at the surface and within aquifers, but the source of organic carbon used by microbes in the reduction and release of arsenic has been debated, as has the wetland type and sedimentary depth where release occurs. Here we present data from fresh-sediment incubations, in situ model sediment incubations and a controlled field experiment with manipulated wetland hydrology and organic carbon inputs. We find that in the minimally disturbed Mekong Delta, arsenic release is limited to near-surface sediments of permanently saturated wetlands where both organic carbon and arsenic-bearing solids are sufficiently reactive for microbial oxidation of organic carbon and reduction of arsenic-bearing iron oxides. In contrast, within the deeper aquifer or seasonally saturated sediments, reductive dissolution of iron oxides is observed only when either more reactive exogenous forms of iron oxides or organic carbon are added, revealing a potential thermodynamic restriction to microbial metabolism. We conclude that microbial arsenic release is limited by the reactivity of arsenic-bearing iron oxides with respect to native organic carbon, but equally limited by organic carbon reactivity with respect to the native arsenic-bearing iron oxides.

  20. River Network Uncertainty and Coastal Morphodynamics in the Mekong Delta: Model Validation and Sensitivity to Fluvial Fluxes

    NASA Astrophysics Data System (ADS)

    Tessler, Z. D.; Vorosmarty, C. J.; Cohen, S.; Tang, H.

    2014-12-01

    A loose-coupling of a basin-scale hydrological and sediment flux model with acoastal ocean hydrodynamics model is used to assess the importance ofuncertainties in river mouth locations and fluxes on coastal geomorphology ofthe Mekong river delta. At the land-ocean interface, river deltas mediate theflux of water, sediment, and nutrients from the basin watershed, though thecomplex delta river network, and into the coastal ocean. In the Mekong riverdelta, irrigation networks and surface water storage for rice cultivationredistribute, in space and time, water and sediment fluxes along the coastline.Distribution of fluxes through the delta is important for accurate assessment ofdelta land aggregation, coastline migration, and coastal ocean biogeochemistry.Using a basin-scale hydrological model, WBMsed, interfaced with a coastalhydrodynamics/wave/sediment model, COAWST, we investigate freshwater andsediment plumes and morphological changes to the subaqueous delta front. Thereis considerable uncertainty regarding how the delta spatially filters water andsediment fluxes as they transit through the river and irrigation network. Byadjusting the placement and relative distribution of WBMsed discharge along thecoast, we estimate the resulting bounds on sediment plume structure, timing, andmorphological deposition patterns. The coastal ocean model is validated bycomparing simulated plume structure and seasonality to MERIS and MODIS derivedestimates of surface turbidity. We find good agreement with regards to plumeextent and timing, with plumes weakest in the early spring, extending stronglyto the west in the fall, and toward the east in winter. Uncertainty regardingriver outflow distribution along the coastline leads to substantial uncertaintyin rates of morphological change, particularly away from the main Mekong Riverdistributary channels.

  1. Flood frequency analysis with uncertainty estimation and its application for hazard assessment - a case study in the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Nguyen Viet, Dung; Apel, Heiko; Merz, Bruno; Bárdossy, András

    2015-04-01

    In many flood-prone regions on earth, the nature of the floods calls for a multivariate approach as analyzing flood frequency, which provides a basic for a sound flood hazard and risk assessment. That is because the flood severity is determined not only by the peak flood discharge as usually considered but also by other aspects such as the volume and even the hydrograph shape of the flood. However, the multivariate flood frequency analysis taking into account its associated uncertainty sources has rarely been studied. The Mekong Delta is one of the largest and most densely populated deltas on Earth. It witnesses annual large scale inundations which are associated to the SE-Asian monsoons. These floods are the basis for the livelihoods of the population of the Delta, but they are also the major hazard. This hazard has, however, not been studied within the frame of a probabilistic flood hazard analysis. Thus this study focuses on the identification of a suitable statistical model for the estimation of flood frequencies considering two important flood aspects peak Q and volume V and exemplifies its applicability for a sound flood hazard assessment for the case study in the Mekong Delta. A copula-based bivariate statistical model with bootstrapping-based uncertainty estimation is, hence, developed for a flood frequency analysis of peak flow and volume. The analysis reveals that even with the available - in a hydrological context - quite long data series (e.g. 88 years in the Mekong Delta), large uncertainties are associated to the bivariate quantiles (Q, V), even for rather frequent events. The main uncertainty source is the sampling uncertainty, thus a direct consequence of the limited length of the data series. However, we still advocate for applying the proposed bivariate frequency method for flood frequency estimation in the Mekong Delta because a) it reflects the essential aspects of floods in this region, b) the uncertainties are inherent for every multivariate

  2. Applications of multispectral imagery to water resources development planning in the lower Mekong Basin (Khmer Republic, Laos, Thailand and Viet-Nam)

    NASA Technical Reports Server (NTRS)

    Vankiere, W. J.

    1973-01-01

    The use of ERTS imagery for water resources planning in the lower Mekong Basin relates to three major issues: (1) it complements data from areas, which have been inaccessible in the past because of security; this concerns mainly forest cover of the watersheds, and geological features, (2) it refines ground surveys; this concerns mainly land forms, and soils of existing and planned irrigation perimeters, and (3) it provides new information, which would be almost or entirely impossible to detect with ground surveys or conventional photography; this concerns the mechanism of flooding and drainage of the delta; siltation of the Great Lake and mapping of acidity, possibly also of salinity, in the lower delta; sedimentation and fisheries in the Mekong Delta estuarine areas.

  3. Flood hazard in the Mekong Delta - a probabilistic, bivariate, and non-stationary analysis with a short-termed future perspective

    NASA Astrophysics Data System (ADS)

    Dung, N. V.; Merz, B.; Bárdossy, A.; Apel, H.

    2013-02-01

    In this paper we present a novel approach for flood hazard analysis of the whole Mekong Delta with a particular focus on the Vietnamese part. Based on previous studies identifying the flood regime in the Mekong delta as non-stationary (Delgado et al., 2010), we develop a non-stationary approach for flood hazard analysis. Moreover, the approach is also bi-variate, as the flood severity in the Mekong Delta is determined by both maximum discharge and flood volume, which determines the flood duration. Probabilities of occurrences of peak discharge and flood volume are estimated by a copula. The flood discharges and volumes are used to derive synthetic hydrographs, which in turn constitute the upper boundary condition for a large-scale hydrodynamic model covering the whole Mekong Delta. The hydrodynamic model transforms the hydrographs into hazard maps. In addition, we extrapolate the observed trends in flood peak and volume and their associated non-stationary extreme value distributions to the year 2030 in order to give a flood hazard estimate for the near future. The uncertainty of extreme flood events in terms of different possible combinations of peak discharge and flood volume given by the copula is considered. Also, the uncertainty in flood hydrograph shape is combined with parameter uncertainty of the hydrodynamic model in a Monte Carlo framework yielding uncertainty estimates in terms of quantile flood maps. The proposed methodology sets the frame for the development of probabilistic flood hazard maps for the entire Mekong Delta. The combination of bi-variate, non-stationary extreme value statistics with large-scale flood inundation modeling and uncertainty quantification is novel in itself. Moreover, it is in particular novel for the Mekong Delta: a region where not even a standard hazard analysis based on a univariate, stationary extreme value statistic exists.

  4. Forecast Mekong: navigating changing waters

    USGS Publications Warehouse

    Powell, Janine

    2011-01-01

    The U.S. Geological Survey (USGS) is using research and data from the Mekong River Delta in Southeast Asia to compare restoration, conservation, and management efforts there with those done in other major river deltas, such as the Mississippi River Delta in the United States. The project provides a forum to engage regional partners in the Mekong Basin countries to share data and support local research efforts. Ultimately, Forecast Mekong will lead to more informed decisions about how to make the Mekong and Mississippi Deltas resilient in the face of climate change, economic stresses, and other impacts.

  5. Intertidal nematode communities in the Mekong estuaries of Vietnam and their potential for biomonitoring.

    PubMed

    Quang, Ngo Xuan; Chau, Nguyen Ngoc; Smol, Nic; Prozorova, Larisa; Vanreusel, Ann

    2016-02-01

    Nematode communities in eight Mekong estuaries were investigated during the dry season. The aim of the study was to identify the structure and the diversity of the communities in relation to the main environmental characteristics. In each estuary, three to four intertidal sampling stations were identified at regular distances from the mouth to up to 45 km land inward. The nematode communities showed a strong correlation with sediment composition and to a lesser degree with chlorophyll a concentrations. Multivariate analysis resulted in the identification of four types of communities. We identified two types of Desmodora communities in the sandy mouth stations and two types of Parodontophora communities in the silty sand stations. One of the silt associated communities showed a preference for higher chlorophyll a concentrations, resulting in higher densities and higher diversity, mainly of monhysterid species. Because of the strong association between community structure and sediment composition, nematodes are a meaningful tool for monitoring changes in their environment. In case their community deviates from what is expected based on sediment, it may serve as an early warning for disturbance. PMID:26780410

  6. Modern sediment dispersal pattern and sediment budget on the continental shelf off the Mekong River delta, South China Sea

    NASA Astrophysics Data System (ADS)

    Szczucinski, W.; Jagodzinski, R.; Hanebuth, T.; Stattegger, K.; Wetzel, A.; Mitrega, M.; Unverricht, D.; Van Phach, P.

    2013-12-01

    The Mekong River is one the major suppliers of sediments to the ocean resulting in the formation of one of the largest river deltas. A major portion of the supplied sediments is accumulated in the subaqueous part of the delta which progrades directly off the river mouths as well as forms in an area next to Camau Peninsula, more than 200 km westward of these mouths. This study shows evidence for the existence of a Mekong-fed prodelta further offshore and provides a first quantitative estimate of the modern fate of fluvial-derived sediments and of the dispersal pattern of sediments transported further offshore to the subaqueous prodelta, to the outer continental shelf and to the deep South China Sea basin. The study is based on 96 surface sediment samples and five short sediment cores which were analyzed for grain-size composition, carbonate and total organic carbon contents, sedimentary structures (X-ray radiographs), clay mineralogy and bulk geochemistry, as well as 210Pb and 137Cs-based sediment accumulation rates. According to these results, the shelf environment is divided into three zones. Westward and southward of Camau Peninsula, the subaqueous prodelta (water depth < 32 m) appears as mud-dominated, organic-rich, high-accumulation (up to 1.5 cm yr-1) zone. South of the river mouths, a wide zone is dominated by terrigenous sands, probably representing the sink for river-supplied bedload sediments. The third, most offshore zone is dominated by muddy sands rich in biogenic carbonate. Evidence for redeposition, event deposition and changing sedimentary conditions is found in each of these zones reflecting the combined effects of tides, changing monsoonal current and wind regimes as well as of episodic tropical storms. The sediment budget calculation reveals that the subaqueous delta front stores about 50% of the fine-grained sediments supplied by the Mekong River. Roughly one fourth of the sediments is retained in the subaerial part of the delta (including the

  7. Modern sedimentation and sediment dispersal pattern on the continental shelf off the Mekong River delta, South China Sea

    NASA Astrophysics Data System (ADS)

    Szczuciński, Witold; Jagodziński, Robert; Hanebuth, Till J. J.; Stattegger, Karl; Wetzel, Andreas; Mitręga, Marta; Unverricht, Daniel; Van Phach, Phung

    2013-11-01

    The Mekong River is one of the major suppliers of sediments to the ocean, resulting in the formation of one of the largest river deltas. A major portion of the supplied sediments is accumulated in the subaqueous delta front, which progrades directly off the river mouths and also forms at a distance of more than 200 km westward, next to the Camau Peninsula. This study presents evidence of the existence of a Mekong-fed prodelta further offshore and provides a first quantitative assessment of the modern fluvial-derived sediment dispersal pattern to the subaqueous prodelta, the outer continental shelf and the deep region of the South China Sea. The study is based on 96 surface shelf sediment samples and five short sediment cores, which were analyzed for grain-size composition, carbonate and total organic carbon contents, sedimentary structures (X-ray radiographs), clay mineralogy and bulk geochemistry as well as 210Pb and 137Cs-based sediment accumulation rates. The major sediment types in water depths of 18 m to 112 m include muddy sand, sand, gravelly muddy sand, sandy mud, gravelly sand and mud. The mud is composed mostly of silt fraction, while gravel is primarily composed of shell hash. The sedimentary structures include lamination, cross-stratification, truncation surfaces and burrows of various types. The carbonate content in the sediments varies from 3% close to the Mekong River mouths to 81% further on the shelf. Total organic carbon is from 0.02% in sand to 0.94% in mud. The highest average elemental concentrations are of Si, Ca, Al, Fe, Mg and K. The spatial variability is similar for Al, K and Ti, as well as for Ca and Sr, suggesting the common presence in phyllosilicates and calcium carbonate minerals, respectively. The most common clay mineral is illite followed by smectite, kaolinite and chlorite. The spatial distribution of clay minerals suggests that they are primarily derived from the Mekong River, except in the northeastern region. The sediment

  8. Two-stage-six-objective calibration of a hydrodynamic-based sediment transport model for the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Viet Dung, Nguyen; Van Manh, Nguyen; Merz, Bruno; Apel, Heiko

    2014-05-01

    An advection-dispersive (AD) module for cohesive sediment transport modelling is built up based on a quasi-2D hydrodynamic model (HD) for the whole Mekong Delta which has been recently developed by Dung et al. (2011) using the modelling software DHI MIKE 11. As parameter uncertainty is one main epistemic uncertainty source of modelling work, it needs to be reduced via a calibration-validation process in order to improve the modelling skill of the simulation tool. In this large scale two-component (HD-AD) model, many parameters need to be properly estimated. These parameters include the flow resistance coefficient (Manning's roughness coefficient), longitudinal dispersion coefficient, the free settling velocity and the critical shear stress for deposition. It should be noted that they are spatially distributed over the modelling domain which consists of more than 4000 branches and 26000 computational nodes used to model real channels and floodplains for the vast area in the Mekong Delta. We aim at developing a suitable framework for optimizing these parameters automatically. As the model included a real 1D illustration of river and channel networks and quasi-2D presentation of floodplains being able to represent both main flow and inundation processes, the calibration is, hence, seen from a multi-objective viewpoint using in parallel high-temporal, low-spatial resolution data (gauge data) and low-temporal, high spatial resolution data (remote sensing data). The calibration (and validation) data utilized in this study comprise of gauged time series data along the main channel (water level, flow discharge and suspended sediment concentration), satellite-based flood extent maps and monitored sedimentation deposition rates in several locations. In total, six objective functions as calibration criteria are defined based on these data. Learning from the feature that AD module can be simulated using finer computational time step after HD results are computed, we propose to

  9. Integrated Biogeochemical and Hydrologic Processes Driving Arsenic Release from Shallow Sediments to Groundwaters of the Mekong Delta

    SciTech Connect

    Kocar, Benjamin D.; Polizzotto, Matthew L.; Benner, Shawn G.; Ying, Samantha C.; Ung, Mengieng; Ouch, Kagna; Samreth, Sopheap; Suy, Bunseang; Phan, Kongkea; Sampson, Michael; Fendorf, Scott

    2008-11-01

    Arsenic is contaminating the groundwater of Holocene aquifers throughout South and Southeast Asia. To examine the biogeochemical and hydrological processes influencing dissolved concentrations and transport of As within soils/sediments in the Mekong River delta, a ~50 km₂ field site was established near Phnom Penh, Cambodia, where aqueous As concentrations are dangerously high and where groundwater retrieval for irrigation is minimal. Dissolved As concentrations vary spatially, ranging up to 1300 µg/L in aquifer groundwater and up to 600 µg/L in surficial clay pore water. Groundwaters with high As concentrations are reducing with negligible dissolved O₂ and high concentrations of Fe(II), NH⁺₄ , and dissolved organic C. Within near-surface environments, these conditions are most pronounced in sediments underlying permanent wetlands, often found within oxbow channels near the Mekong River. There, labile C, co-deposited with As-bearing Fe (hydr)oxides under reducing conditions, drives the reductive mobilization (inclusive of Fe and As reduction) of As. Here, conditions are described under which As is mobilized from these sediments, and near-surface As release is linked to aquifer contamination over long time periods (100s to 1000s of years). Site biogeochemistry is coupled with extensive hydrologic measurements, and, accordingly, a comprehensive interpretation of spatial As release and transport within a calibrated hydraulic flow-field is provided of an As-contaminated aquifer that is representative of those found throughout South and Southeast Asia.

  10. Effects of changing rice cultural practices on C-band synthetic aperture radar backscatter using Envisat advanced synthetic aperture radar data in the Mekong River Delta

    NASA Astrophysics Data System (ADS)

    Lam-Dao, Nguyen; Le Toan, Thuy; Apan, Armando; Bouvet, Alexandre; Young, Frank; Le-van, Trung

    2009-11-01

    Changes in rice cultivation systems have been observed in the Mekong River Delta, Vietnam. Among the changes in cultural practices, the change from transplanting to direct sowing, the use of water-saving technology, and the use of high production method could have impacts on radar remote sensing methods previously developed for rice monitoring. Using Envisat (Environmental Satellite) ASAR (Advanced Synthetic Aperture Radar) data over the province of An Giang, this study showed that the radar backscattering behaviour is much different from that of the reported traditional rice. At the early stage of the season, direct sowing on fields with rough and wet soil surface provides very high backscatter values for HH (Horizontal transmit - Horizontal receive polarisation) and VV (Vertical transmit - Vertical receive polarisation) data, as a contrast compared to the very low backscatter of fields covered with water before emergence. The temporal increase of the backscatter is therefore not observed clearly over direct sowing fields. Hence, the use of the intensity temporal change as a rice classifier proposed previously may not apply. Due to the drainage that occurs during the season, HH, VV and HH/VV are not strongly related to biomass, in contrast with past results. However, HH/VV ratio could be used to derive the rice/non-rice classification algorithm for all conditions of rice fields in the test province. The mapping results using the HH/VV polarization ratio at a single date in the middle period of the rice season were assessed using statistical data at different districts in the province, where very high accuracy was found. The method can be applied to other regions, provided that the synthetic aperture radar data are acquired during the peak period of the rice season, and that few training fields provide adjusted threshold values used in the method.

  11. High temperature and risk of hospitalizations, and effect modifying potential of socio-economic conditions: A multi-province study in the tropical Mekong Delta Region.

    PubMed

    Phung, Dung; Guo, Yuming; Nguyen, Huong T L; Rutherford, Shannon; Baum, Scott; Chu, Cordia

    2016-01-01

    The Mekong Delta Region (MDR) in Vietnam is highly vulnerable to extreme weather related to climate change. However there have been hardly any studies on temperature-hospitalization relationships. The objectives of this study were to examine temperature-hospitalization relationship and to evaluate the effects of socio-economic factors on the risk of hospitalizations due to high temperature in the MDR. The Generalized Linear and Distributed Lag Models were used to examine hospitalizations for extreme temperature for each of the 13 provinces in the MDR. A random-effects meta-analysis was used to estimate the pooled risk for all causes, and for infectious, cardiovascular, and respiratory diseases sorted by sex and age groups. Random-effects meta-regression was used to evaluate the effect of socio-economic factors on the temperature-hospitalization association. For 1°C increase in average temperature, the risk of hospital admissions increased by 1.3% (95% CI, 0.9-1.8) for all causes, 2.2% (95% CI, 1.4-3.1) for infectious diseases, and 1.1% (95% CI, 0.5-1.7) for respiratory diseases. However the result was inconsistent for cardiovascular diseases. Meta-regression showed population density, poverty rate, and illiteracy rate increased the risk of hospitalization due to high temperature, while higher household income, houses using safe water, and houses using hygienic toilets reduced this risk. In the MDR, high temperatures have a significant impact on hospitalizations for infectious and respiratory diseases. Our findings have important implications for better understanding the future impacts of climate change on residents of the MDR. Adaptation programs that consider the risk and protective factors should be developed to protect residents from extreme temperature conditions. PMID:27060418

  12. Relation between oceanic conditions in the South China Sea and water levels within and along the Vietnamese Mekong River Delta

    NASA Astrophysics Data System (ADS)

    Uehara, K.; Tanaka, A.; Saito, Y.; Tamura, T.; Nguyen, V. L.; Ta, T. K.

    2013-12-01

    Seasonal water level change within and around the Vietnamese Mekong River Delta (MRD) has been analyzed to understand the impact of climate change in the South China Sea on river flooding within the MRD. It was found that the sea level variability along the deltaic coast has high coherence with the strength of offshore oceanic currents which seasonally reverse their direction under the SE Asian monsoon climate, indicating that the coastal sea level is linked with offshore currents through a geostrophic relation. It was also suggested that the temporal pattern of water levels in the middle reaches of the MRD, 80-100km apart from the river mouth, was influenced not only by upstream information but also by the downstream sea level change. These results indicates that the climatic change in the oceanic current field may influence the occurrence of flooding within the MRD especially during the NE monsoon season when the sea level is high.

  13. Reactive and unreactive iron minerals hosting arsenic within seasonal wetland sediments of the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Stuckey, J.; Schaefer, M.; Lezama, J.; Dittmar, J.; Fendorf, S.

    2013-12-01

    Millions of people in the deltaic regions of S/SE Asia regularly consume arsenic contaminated groundwater. Within the Mekong Delta of Cambodia, for example, arsenic persists within the groundwater despite being flushed by several pore volumes of recharge. The identity and reactivity of the minerals contributing to the persistence of arsenic in the deltaic aquifers remain elusive. Here we seek to define the molecular form of the arsenic and its host phases along defined flow paths in seasonally saturated wetlands: i) a grassland flooded for ~ 3 - 4 months of the year (Grassland) and ii) an abandoned river channel saturated for ~ 5 - 6 months (Oxbow). Sediment cores were retrieved by pounding aluminum cores into a fresh profile exposed by successive excavation. The cores were sealed with melted wax in the field and stored at 4 °C until processed. Depths of 0.2 to 6 m were sampled at the Grassland site and 0.2 to 4 m at the Oxbow site. Sediments were dried under 95%N2/5%H2 atmosphere. A 1 M HCl extraction dissolving the 'reactive' iron (predominantly poorly crystalline iron oxides) solubilized 3 - 7 % of the total iron in the Grassland site and 8 - 41 % in the Oxbow site. A citrate-bicarbonate-dithionite (CBD) extraction was performed to extract reducible iron (predominantly iron oxides), accounting for 35 - 50 % of the total iron in the Grassland site and 27 - 44 % in the Oxbow site. Correspondingly, least squares fitting of k3 - weighted chi(k) iron extended X-ray absorption fine structure (EXAFS) spectra showed that goethite and hematite together comprised 34 - 50 % of the iron mineralogy in the mineral sediments of the Grassland site and 24 - 38 % of those in the Oxbow site. The remaining iron minerals present were predominantly silicates. Iron EXAFS spectra were obtained for the post-CBD extracted sediments, theoretically containing only non-reducible iron. Least squares fitting of the bulk (pre-CBD extracted) sediments was performed a second time with the

  14. Indigenous arsenic(V)-reducing microbial communities in redox-fluctuating near-surface sediments of the Mekong Delta.

    PubMed

    Ying, S C; Damashek, J; Fendorf, S; Francis, C A

    2015-11-01

    Arsenic (As) cycling within soils and sediments of the Mekong Delta of Cambodia is affected by drastic redox fluctuations caused by seasonal monsoons. Extensive flooding during monsoon seasons creates anoxic soil conditions that favor anaerobic microbial processes, including arsenate [As(V)] respiration-a process contributing to the mobilization of As. Repeated oxidation and reduction in near-surface sediments, which contain 10-40 mg kg(-1) As, lead to the eventual downward movement of As to the underlying aquifer. Amplification of a highly conserved functional gene encoding dissimilatory As(V) reductase, arrA, can be used as a molecular marker to detect the genetic potential for As(V) respiration in environmental samples. However, few studies have successfully amplified arrA from sediments without prior enrichment, which can drastically shift community structure. In the present study, we examine the distribution and diversity of arrA genes amplified from multiple sites within the Cambodian Mekong Delta as a function of near-surface depth (10, 50, 100, 200, and 400 cm), where sediments undergo seasonal redox fluctuations. We report successful amplification of 302 arrA gene sequences (72 OTUs) from near-surface Cambodian soils (without prior enrichment or stimulation with carbon amendments), where a large majority (>70%) formed a well-supported clade that is phylogenetically distinct from previously reported sequences from Cambodia and other South and Southeast Asian sediments, with highest sequence similarity to known Geobacter species capable of As(V) respiration, further supporting the potentially important role of Geobacter sp. in arsenic mobilization in these regions. PMID:26466963

  15. Persistent organic pollutants in wetlands of the Mekong Basin

    USGS Publications Warehouse

    Triet, Tran; Barzen, Jeb Anthony; Choowaew, Sansanee; Engels, Jon Michael; Ni, Duong Van; Mai, Nguyen Anh; Inkhavilay, Khamla; Soben, Kim; Sethik, Rath; Gomotean, Bhuvadol; Thuyen, Le Xuan; Kyi, Aung; Du, Nguyen Huy; Nordheim, Richard; Lam, Ho Si Tung; Moore, Dorn M.; Wilson, Scott

    2013-01-01

    In this study, the presence and concentration of persistent organic pollutants (POP) were assessed in surface sediments collected from a wide variety of wetlands located throughout the Mekong Basin in Myanmar, Lao People’s Democratic Republic (PDR), Thailand, Cambodia, and Vietnam. Of the 39 POPs tested in 531 sediment samples, dichlorodiphenyltrichloroethane (DDT) and its metabolites endosulfan, hexachlorobenzene (HCB), and endrin were most commonly detected. Even though DDT was banned in the 1990s, some use of DDT may still be occurring in the Mekong Basin. The amount of metabolites for DDT—dichlorodiphenyldichloroethylene (DDE) and dichlorodiphenyldichloroethane (DDD)—found, however, suggests that use of DDT is on the decline throughout the region. HCB and endrin were found distributed broadly throughout the Mekong Basin but not in high amounts. The concentration and distribution of endosulfan and its metabolites represent a serious problem requiring further study and management action. While the total loading of POPs in wetland sediments of the Mekong Basin was generally low, hotspot sites occurred where concentrations exceeded established ecological risk thresholds. For example, wetlands of the open, dry dipterocarp forest of northern Cambodia and Vietnam as well as wetlands in the Mekong Delta of Vietnam contained high concentrations of some POPs. High concentrations of POPs were detected in some wetlands important for biodiversity conservation. Hotspots identified in wetlands such as the Tonle Sap not only had concentrations of DDT and DDE that exceeded Canadian and U.S. benchmarks, but fauna sampled in the area also showed high degrees of bioaccumulation of the same substances. Further and more extensive attention to monitoring POP presence in water birds, fish, and other aquatic organisms is warranted because of the bioaccumulation of these chemicals at higher levels in the food chain. This study represents a collaboration of eight universities from

  16. Diversity and As-adsorption properties of Mn(II)-oxidizing bacteria within tropical wetlands of the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Ying, S. C.; Kocar, B. D.; Fendorf, S.; Francis, C. A.

    2007-12-01

    Manganese (Mn) and iron (Fe) oxides are ubiquitous minerals that occur under similar redox conditions in terrestrial systems and have high sorptive capacities for many trace metals, including arsenic (As). In most natural environments, Fe oxidation is dominated by abiotic processes, while Mn oxides are primarily formed via bacterial Mn(II) oxidation, and both processes can profoundly impact the mobility of metal(loid) contaminants. Deciphering the mechanisms involved in arsenic transport within soils and sediments is essential for aiding many Southeast Asian countries, including Cambodia, where naturally occurring As is in groundwater at concentrations well above the WHO recommended limit. Although numerous past studies have characterized the effects of As adsorption onto Fe and Mn oxides individually, it is unknown whether, in the presence of both oxides, there is preferential adsorption of As onto one oxide over the other. In the present study, we examine the competitive retention of As(III) and As(V) on goethite and biogenic Mn oxides using Donnan membranes--where each oxides is isolated by a semi-permeable membrane through which arsenic can migrate. Mn(II)-oxidizing bacteria, isolated from several Mn-rich sites along the Mekong River and wetland areas within the Mekong delta, were dominated by a diverse array of Bacillus strains that rapidly oxidize Mn(II) within three to five days in liquid culture. The results of this study not only expand our knowledge of the diversity and biogeochemical importance of terrestrial Mn(II)-oxidizing bacteria, but also contribute to our understanding the relative impact of Fe and Mn oxides on arsenic retention within natural wetlands.

  17. Monsoon-influenced variations in morphology and sediment of a mesotidal beach on the Mekong River delta coast

    NASA Astrophysics Data System (ADS)

    Tamura, Toru; Horaguchi, Keishi; Saito, Yoshiki; Nguyen, Van Lap; Tateishi, Masaaki; Ta, Thi Kim Oanh; Nanayama, Futoshi; Watanabe, Kazuaki

    2010-03-01

    A mesotidal beach on the Mekong River delta coast exhibits unique patterns of river sediment discharge and experiences reversals of ocean wave directions in response to the summer and winter monsoons. We analyzed long-term changes of the shoreline since 1936 from past topographic maps and satellite images, and short-term changes in geomorphology and sedimentology by undertaking repeated field surveys between November 2005 and February 2008 along six shore-normal beach transects. The shoreline of the Mekong River delta coast has changed asymmetrically over the last 70 years in response to net southwestward sediment transport related to dry northeasterly winter monsoons. During the summer rainy season, large volumes of sediments are discharged from the river; at this time, wave direction is reversed in response to the relatively weak southwesterly summer monsoon. Mud and very fine sand in the surface sediments of the northeastern (updrift) beach transects tend to be removed during winter, suggesting that the sediment supplied from the river during summer is temporarily deposited near the river mouth and later transported southwestward during the winter monsoon. The relief of intertidal bars on the beach increased during winter in response to higher waves. However, previous studies have suggested that higher waves flatten bars. We hypothesize that the increase in relief that we observed is related to a wide and shallow subtidal delta-front platform that attenuates ocean waves at all times other than at high tide. The beach profile varies longshore: the accreting to stable beach dips seaward at a gradient of about 1/80 with up to three longshore intertidal bars, classified here as either slip-face bars or low-amplitude ridges. In contrast, the eroding beach profile is much steeper (1/20-1/40) and linear without intertidal bars, and is similar in form to a low-tide terrace. Because there is little variation of wave size and grain size within the study area, we consider

  18. The U.S. Community College Model and Vietnam's Higher Education System.

    ERIC Educational Resources Information Center

    Oliver, Diane

    This paper reports on research conducted to determine if United States' community college model can be applied to higher education systems in developing countries. The author examined Vietnam's higher education system and conducted a case study of Can Tho University (CTU) in the Mekong Delta. First, common characteristics found among community…

  19. Impacts of dyke development in flood prone areas in the Vietnamese Mekong Delta to downstream flood hazard

    NASA Astrophysics Data System (ADS)

    Khanh Triet Nguyen, Van; Dung Nguyen, Viet; Fujii, Hideto; Kummu, Matti; Merz, Bruno; Apel, Heiko

    2016-04-01

    The Vietnamese Mekong Delta (VMD) plays an important role in food security and socio-economic development of the country. Being a low-lying coastal region, the VMD is particularly susceptible to both riverine and tidal floods, which provide, on (the) one hand, the basis for the rich agricultural production and the livelihood of the people, but on the other hand pose a considerable hazard depending on the severity of the floods. But despite of potentially hazardous flood, the area remain active as a rice granary due to its nutrient-rich soils and sediment input, and dense waterways, canals and the long standing experience of the population living with floods. In response to both farmers' requests and governmental plans, the construction of flood protection infrastructure in the delta progressed rapidly in the last twenty years, notably at areas prone to deep flooding, i.e. the Plain of Reeds (PoR) and Long Xuyen Quadrangle (LXQ). Triple rice cropping becomes possible in farmlands enclosed by "full-dykes", i.e. dykes strong and high enough to prevent flooding of the flood plains for most of the floods. In these protected flood plains rice can be grown even during the peak flood period (September to November). However, little is known about the possibly (and already alleged) negative impacts of this fully flood protection measure to downstream areas. This study aims at quantifying how the flood regime in the lower part of the VMD (e.g. Can Tho, My Thuan, …) has been changed in the last 2 recent "big flood" events of 2000 and 2011 due to the construction of the full-dyke system in the upper part. First, an evaluation of 35 years of daily water level data was performed in order to detect trends at key gauging stations: Kratie: upper boundary of the Delta, Tan Chau and Chau Doc: areas with full-dyke construction, Can Tho and My Thuan: downstream. Results from the Mann-Kendall (MK) test show a decreasing trend of the annual maximum water level at 3 stations Kratie, Tan

  20. Closing the irrigation deficit in Cambodia: Implications for transboundary impacts on groundwater and Mekong River flow

    NASA Astrophysics Data System (ADS)

    Erban, Laura E.; Gorelick, Steven M.

    2016-04-01

    Rice production in Cambodia, essential to food security and exports, is largely limited to the wet season. The vast majority (96%) of land planted with rice during the wet season remains fallow during the dry season. This is in large part due to lack of irrigation capacity, increases in which would entail significant consequences for Cambodia and Vietnam, located downstream on the Mekong River. Here we quantify the extent of the dry season "deficit" area in the Cambodian Mekong River catchment, using a recent agricultural survey and our analysis of MODIS satellite data. Irrigation of this land for rice production would require a volume of water up to 31% of dry season Mekong River flow to Vietnam. However, the two countries share an aquifer system in the Mekong Delta, where irrigation demand is increasingly met by groundwater. We estimate expansion rates of groundwater-irrigated land to be >10% per year in the Cambodian Delta using LANDSAT satellite data and simulate the effects of future expansion on groundwater levels over a 25-year period. If groundwater irrigation continues to expand at current rates, the water table will drop below the lift limit of suction pump wells, used for domestic supply by >1.5 million people, throughout much of the area within 15 years. Extensive groundwater irrigation jeopardizes access for shallow domestic water supply wells, raises the costs of pumping for all groundwater users, and may exacerbate arsenic contamination and land subsidence that are already widespread hazards in the region.

  1. Flood loss assessment in Can Tho City, Vietnam

    NASA Astrophysics Data System (ADS)

    Do, T. C.; Kreibich, H.

    2012-04-01

    Floods are recurring events in the Lower Mekong Basin resulting in loss of life and property, causing damage to agriculture and rural infrastructure, and disrupting social and economic activities. Flood management and mitigation has become a priority issue at the national and regional levels. Besides, it is expected that large areas of the Mekong delta, the Red River delta and the central coast will be flooded by sea-level rise due to climate change. Can Tho City is ranked under the five most flood-tide-influenced cities of Vietnam. It is the biggest city in the Mekong delta and it is located near the Hau river. Like other region of the Mekong delta, Can Tho suffers due to floods from upstream and flood tides from the sea. In the flood season large rural areas of the city are flooded, particularly during tidal days. Flood risk management policy includes preparative measures for living with floods and to minimise the damage caused by floods as well as to take advantage of floods for sustainable development. An intensive literature review, including administrative reports as well as expert interviews have been undertaken to gain more insight into flood characteristics, their consequences and risk mitigation. Therefore, flood damaging processes and trends have been reviewed for Can Tho City and the Mekong Basin in Vietnam. Additionally, suitable flood damage estimation methodologies have been collected as important input for flood risk analyses. On this basis it has been investigated which flood risk mitigation and management strategies promise to be effective in Can Tho City, Vietnam.

  2. Shoreline changes at the mouths of the Mekong River delta over the last 50 years: fluctuating sediment supply and shoreline cells

    NASA Astrophysics Data System (ADS)

    Anthony, E.; Besset, M.; Brunier, G.; Dussouillez, P.; Dolique, F.; Nguyen, V. L.; Goichot, M.

    2014-12-01

    River delta shorelines may be characterized by complex patterns of sediment transport and sequestering at various timescales in response to changes in sediment supply, hydrodynamic conditions, and deltaic self-organization. While being good indicators of delta stability, these changes also have important coastal management and defence implications. These aspects are examined with reference to the mouths of the Mekong River delta, the world's third largest delta, backbone of the Vietnamese economy and home to nearly 20 million people. We conducted an analysis of shoreline fluctuations over the last five decades using low-resolution Landsat (1973-2014), very high-resolution SPOT 5 (2003-2011) satellite imagery, topographic maps (1950, 1965), and field hydrodynamic and shoreline topographic measurements. The results show that the 250 km-long river-mouth sector of the delta shoreline has been characterized by overall accretion but with marked temporal and spatial variations. The temporal pattern is attributed to fluctuations in sediment supply due to both human activities and natural variations in catchment sediment loads (e.g., 2000-2003), and natural adjustments in delta-plain sediment storage and delivery to the coast. The spatial pattern is indicative of discrete sediment cells that may be a response to an overall decreasing sand supply, especially since 2003, following increasingly massive riverbed mining with concomitant losses in channel-bed sand. Field measurements show the prevalence of mesotidal bar-trough beaches characterized by sand migration to the southwest in response to energetic dry-season monsoon waves. Beaches underfed as a result of both wave-energy gradients and possible diminishing sand supply from the adjacent river mouths are eroded to feed accreting beaches. Understanding this cell pattern has important implications in terms of: (1) interpreting past patterns of shoreline translation involved in the construction of successive beach ridges that

  3. Reactivity and speciation of mineral-associated arsenic in seasonal and permanent wetlands of the Mekong Delta

    NASA Astrophysics Data System (ADS)

    Stuckey, Jason W.; Schaefer, Michael V.; Benner, Shawn G.; Fendorf, Scott

    2015-12-01

    Millions of people in the deltaic regions of S/SE Asia regularly consume As contaminated groundwater. Arsenic persists within these groundwaters despite being flushed by several pore volumes of recharge, indicative of an in situ solid phase source. Despite the importance of this solid phase source, the identity and reactivity of the minerals hosting and releasing As in the deltaic aquifers remain poorly constrained. Here we seek to define the chemistry and reactivity of As and its host minerals in aquifer sediments recharged by both seasonally saturated and permanent wetlands in the Mekong Delta of Cambodia. Sediment cores were retrieved to depths of up to 30 m. Selective extractions on near-surface sediments (to depths of 4-6 m) indicate that more than a third (27-50%) of the Fe in the profile is "reducible" (citrate-bicarbonate-dithionite-extractable) - nominally consisting of Fe(III) oxides. The Fe(III) oxide fraction was approximately the same under seasonal wetlands (mean = 39%) compared with sediments from beneath permanent wetlands (mean = 37%). Correspondingly, Fe K-edge extended X-ray absorption fine structure (EXAFS) spectra analysis indicates that the Fe mineral phases are predominantly goethite and hematite (30-50%). Analysis of solid phase As speciation by X-ray absorption near edge structure (XANES) spectroscopy showed arsenate in the shallowest sediments (upper 1 and 4 m of seasonal and permanent wetlands), and arsenite and/or As sulfides as the dominant phases in the deeper sediments. The reducible As fraction ranged from 17% to 42% of the total As at both sites. The exception was found in a peat layer at 6 m beneath the seasonal wetland, in which only 1% of the total As was reducible. Arsenian pyrite was the predominant form of As in the peat. Thus, a pool of As hosted by reducible mineral phases persists in sediments below both the seasonal and permanently saturated wetland sites.

  4. Evidence of Water Quality Degradation in Lower Mekong Basin Revealed by Self-Organizing Map

    PubMed Central

    Chea, Ratha; Grenouillet, Gaël; Lek, Sovan

    2016-01-01

    To reach a better understanding of the spatial variability of water quality in the Lower Mekong Basin (LMB), the Self-Organizing Map (SOM) was used to classify 117 monitoring sites and hotspots of pollution within the basin identified according to water quality indicators and US-EPA guidelines. Four different clusters were identified based on their similar physicochemical characteristics. The majority of sites in upper (Laos and Thailand) and middle part (Cambodia) of the basin were grouped in two clusters, considered as good quality water with high DO and low nutrient levels. The other two clusters were mostly composed of sites in Mekong delta (Vietnam) and few sites in upstream tributaries (i.e., northwestern Thailand, Tonle Sap Lake, and swamps close to Vientiane), known for moderate to poor quality of water and characterized by high nutrient and dissolved solid levels. Overall, we found that the water in the mainstream was less polluted than its tributaries; eutrophication and salinity could be key factors affecting water quality in LMB. Moreover, the seasonal variation of water quality seemed to be less marked than spatial variation occurring along the longitudinal gradient of Mekong River. Significant degradations were mainly associated with human disturbance and particularly apparent in sites distributed along the man-made canals in Vietnam delta where population growth and agricultural development are intensive. PMID:26731522

  5. Evidence of Water Quality Degradation in Lower Mekong Basin Revealed by Self-Organizing Map.

    PubMed

    Chea, Ratha; Grenouillet, Gaël; Lek, Sovan

    2016-01-01

    To reach a better understanding of the spatial variability of water quality in the Lower Mekong Basin (LMB), the Self-Organizing Map (SOM) was used to classify 117 monitoring sites and hotspots of pollution within the basin identified according to water quality indicators and US-EPA guidelines. Four different clusters were identified based on their similar physicochemical characteristics. The majority of sites in upper (Laos and Thailand) and middle part (Cambodia) of the basin were grouped in two clusters, considered as good quality water with high DO and low nutrient levels. The other two clusters were mostly composed of sites in Mekong delta (Vietnam) and few sites in upstream tributaries (i.e., northwestern Thailand, Tonle Sap Lake, and swamps close to Vientiane), known for moderate to poor quality of water and characterized by high nutrient and dissolved solid levels. Overall, we found that the water in the mainstream was less polluted than its tributaries; eutrophication and salinity could be key factors affecting water quality in LMB. Moreover, the seasonal variation of water quality seemed to be less marked than spatial variation occurring along the longitudinal gradient of Mekong River. Significant degradations were mainly associated with human disturbance and particularly apparent in sites distributed along the man-made canals in Vietnam delta where population growth and agricultural development are intensive. PMID:26731522

  6. Forecast Mekong 2012: Building scientific capacity

    USGS Publications Warehouse

    Stefanov, James E.

    2012-01-01

    In 2009, U.S. Secretary of State Hillary R. Clinton joined the Foreign Ministers of Cambodia, Laos, Thailand, and Vietnam in launching the Lower Mekong Initiative to enhance U.S. engagement with the countries of the Lower Mekong River Basin in the areas of environment, health, education, and infrastructure. The U.S. Geological Survey Forecast Mekong supports the Lower Mekong Initiative through a variety of activities. The principal objectives of Forecast Mekong include the following: * Build scientific capacity in the Lower Mekong Basin and promote cooperation and collaboration among scientists working in the region. * Provide data, information, and scientific models to help resource managers there make informed decisions. * Produce forecasting and visualization tools to support basin planning, including climate change adaptation. The focus of this product is Forecast Mekong accomplishments and current activities related to the development of scientific capacity at organizations and institutions in the region. Building on accomplishments in 2010 and 2011, Forecast Mekong continues to enhance scientific capacity in the Lower Mekong Basin with a suite of activities in 2012.

  7. February 2012 workshop jumpstarts the Mekong Fish Monitoring Network

    USGS Publications Warehouse

    Andersen, Matthew E.; Ainsley, Shaara M.

    2012-01-01

    The Mekong River in Southeast Asia travels through a basin rich in natural resources. The river originates on the northern slope of the world's tallest mountains, the Himalaya Range, and then drops elevation quickly through steep mountain gorges, tumbling out of China into Myanmar (Burma) and the Lao People's Democratic Republic (Lao PDR). The precipitous terrain of Lao PDR and Thailand generates interest in the river and its tributaries for hydropower development. The terrain, soils, water, and climate make it one of the world's most biologically rich regions. The Mekong's bounty is again on display in the Mekong River Delta, where rice production has successfully been increased to high levels making Vietnam second only to Thailand as the world's largest rice exporters. At least 800 fish species contribute to the natural resource bounty of the Mekong River and are the basis for one of the world's most productive fisheries that provide the primary protein source to more than 50 million people. Against this backdrop of rich natural resources, the U.S. Geological Survey (USGS) is working with the consulting firm FISHBIO, colleagues from the international Delta Research and Global Observation Network (DRAGON) Institute, and a broad contingent of Southeast Asian representatives and partners from abroad to increase knowledge of the Mekong River fisheries and to develop the capacity of permanent residents to investigate and understand these fisheries resources. With the Lower Mekong Basin (LMB) region facing the likelihood of significant environmental changes as a result of both human activities and global climate change, enhancing environmental understanding is critical. To encourage cooperation among the LMB scientists and managers in the study of the Mekong River's fisheries, FISHBIO and the USGS, with generous support from the U.S. State Department, hosted a workshop in Phnom Penh, Cambodia, in February 2012. Workshop participants were from Lao PDR, Thailand

  8. Bathymetry of the Hong and Luoc River Junction, Red River Delta, Vietnam, 2010

    USGS Publications Warehouse

    Kinzel, Paul J.; Nelson, Jonathan M.; Toan, Duong Duc; Thanh, Mung Dinh; Shimizu, Yasuyuki

    2012-01-01

    The U.S. Geological Survey, in collaboration with the Water Resources University in Hanoi, Vietnam, conducted a bathymetric survey of the junction of the Hong and Luoc Rivers. The survey was done to characterize the channel morphology of this delta distributary network and provide input for hydrodynamic and sediment transport models. The survey was carried out in December 2010 using a boat-mounted multibeam echo sounder integrated with a global positioning system. A bathymetric map of the Hong and Luoc River junction was produced which was referenced to the datum of the Trieu Duong tide gage on the Luoc River.

  9. Characterization and interaction of precipitation, river water and groundwater in the Vietnamese Mekong Delta - A case study in the Plain of Reeds

    NASA Astrophysics Data System (ADS)

    Duy Nguyen, Le; Heidbüchel, Ingo; Merz, Bruno; Apel, Heiko

    2016-04-01

    An understanding of the interactions between surface water and groundwater systems in the Vietnamese Mekong Delta (VMD) is important not only for water resources planning and management, but also for the livelihood of the majority of the population in the delta. Precipitation and ground water, but also river water is used as drinking water in the communes of the Delta. Particularly the ground water is increasingly exploited, but the important processes like river - aquifer interaction and ground water recharge rates are largely unknown. This study thus aims at the characterization of processes between the different water resources. For this the different water sources were sampled over longer time periods and analysed for isotopic composition (2H, 18O). Additionally surface and ground water levels were recorded, as well as the temperature profile at and under the river bed in order to identify the river-ground water interaction. First results indicate that the isotopic composition and the local meteoric water line of the precipitation is very similar to the GNIP data for Bangkok, indicating similar isotopic sequestration and origin of the rainfall in the region (near ocean areas of SE-Asia). The isotopic composition of precipitation and river water exhibits a strong seasonal signal indicating the monsoonal influence. During the monsoon season both precipitation and river water is depleted in stable isotopes, while the dry season shows an enriched composition. This also indicates the different composition of the river water over the seasons. During the rainy season the portion of rain water, i.e. surface runoff stemming from the Mekong basin but also direct rainfall contribution in the Mekong Delta is considerably larger, as expected. The enriched composition during the dry season indicates a larger ground water, i.e. base flow portion, but also a generally higher evaporation due to the lower atmospheric moisture. The isotopic composition of the ground water differs

  10. Hydrogeochemical characteristics of groundwater from the two main aquifers in the Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Nguyen, Thuy Thanh; Kawamura, Akira; Tong, Thanh Ngoc; Nakagawa, Naoko; Amaguchi, Hideo; Gilbuena, Romeo

    2014-10-01

    In the Red River Delta, situated in the northern part of Vietnam, nearly its entire population depends solely on groundwater for daily water consumptions. For this reason, groundwater quality assessments must be carefully carried out using hydrogeochemical properties, to ensure effective groundwater resource planning for the Delta’s present and future groundwater use. In this study, the spatial and seasonal changes in the hydrogeochemical characteristics of groundwater in the two main aquifers of the RRD were investigated by analyzing the physicochemical data obtained in 2011 from 31 conjunctive wells in the Delta’s Holocene unconfined aquifer (HUA) and Pleistocene confined aquifer (PCA) using the Piper diagram and the Gibbs diagram. Results of the data analysis show that the groundwater in both aquifers in the upstream area of the delta is dominated by the [Ca2+-HCO3-] water-type, while the [Na+-Cl-] dominates along the middle-stream and downstream areas. Seasonal changes in the hydrogeochemical facies in both aquifers, comparing the results for the dry and the rainy seasons, were detected in about one third of the sampling wells, which were mainly located at the upstream portion of the Delta. The hydrogeochemical facies of HUA were different from that of PCA by about 45% of the sampling wells in both the dry and the rainy seasons, which were found mostly in the upstream and middle-stream areas.

  11. Vietnam.

    PubMed

    1984-05-01

    Attention in this discussion of Vietnam is directed to the following: people; geography; history; government; the economy (agriculture and industry, trade and balance of payments); foreign relations; and relations between the US and Vietnam. In mid-1983 the population was estimated at 57,610,000 with an annual growth rate of 2.4%. Ethnic Vietnamese constitute almost 90% of the population. Various ethnic groups make up the remaining 10% of the population, with approximately 1.2 million Chinese being the most numerous and concentrated in southern Vietnam. The 2nd largest minority, the Montagnards (mountain tribesmen) comprise 2 main ethnolinguistic groups--Malayo Polynesia and Mon-Khmer. The most important political institution in Vietnam is the Vietnamese Communisty Party. All but 4 party Politburo members concurrently hold high positions in the government. The most important powers within the Vietnamese government, as opposed to the Communisty Party, are the executive agencies. Under the overly ambitious initial 5 year plan and the more conservative 1981-85 plan, the Vietnamese have made little progress in raising output and living standards beyond the levels of the 1960s. Guidelines of the 1981-85 plan call for attaining food self sufficiency, strengthening export and consumer industries, as well as the heavy industries that support them, and improving transport and energy production. The US does not have diplomatic relations with Vietnam. PMID:12178076

  12. Planning practice in support of economically and environmentally sustainable roads in floodplains: the case of the Mekong delta floodplains.

    PubMed

    Douven, Wim; Buurman, Joost

    2013-10-15

    Road development in relatively undisturbed floodplain systems, such as the floodplains of the Mekong River, will impact hydraulics and interrupt the natural flow of water. This affects the ecology and environment, and the livelihoods of people who depend on fishing and agriculture. On the other hand, floods can severely damage road infrastructure in years with large floods and can cause high annual maintenance costs. Improving road development practices in floodplains is a complex, multidimensional task involving hydraulic and geotechnical analysis, ecosystem analysis, socio-economic analysis, policy analysis, etc. This paper analyses the planning practice of road development and rehabilitation and how this practice can be improved in support of economically and environmentally sustainable roads in floodplains. It is concluded that although ample technical, planning and environmental assessment guidelines exist, guidelines need updating to address cumulative impacts at floodplain level and factors hampering the implementation in guidelines should be addressed in the guideline design (process). PMID:23735460

  13. Trace Gas Emissions from Extensive Aquaculture Systems in the Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Beman, J.; Seto, K. C.

    2002-12-01

    The Red River Delta of Vietnam is an area undergoing rapid land use change. Aquaculture development is among the most significant of these transformations, with important economic, social and environmental effects. We explored the potential for managed mangrove' and `converted paddy' aquaculture systems in the Delta to produce and/or consume greenhouse gasses. We measured dissolved concentrations of the radiatively-important trace gasses methane (CH4) and nitrous oxide (N2O), as well as associated parameters. All ponds were super-saturated with CH4, with concentrations ranging from 132-1203 nM, (mean 561 nM) in managed mangrove, and 28-521 nM (mean 110 nM) in converted paddy. Surprisingly, none of the ponds was measurably supersaturated with N2O. Methane fluxes were calculated for all ponds using five well-accepted models of gas flux based on wind speed. Mean flux values ranged from 1.04 to 17.09 mg CH4 m-2 d-1 for managed mangrove, falling somewhere between fluxes reported for natural systems and those receiving sewage inputs. Further measurements should be made in more intensive systems to better understand the potential for trace gas production-particularly N2O-in aquaculture systems.

  14. Social and ecological challenges of market-oriented shrimp farming in Vietnam.

    PubMed

    Lan, Ngo Thi Phuong

    2013-01-01

    Vietnam is one of the largest shrimp exporters in the world. Since 2010, Vietnam has earned about two billion dollars annually through shrimp exports. As a fertile area of greatest potential for agricultural production in Vietnam, the Mekong Delta has been a major contributor to the country's achievements, especially in the agricultural sector. During recent decades, trade liberation along with various policies in support of aquaculture has accelerated the development of shrimp production in the Delta. Based on an ethnographic study of shrimp farming in the Mekong Delta of Vietnam, I assert that along with great rewards arising from the expansion of shrimp farming areas, productivity, and export value, the shrimp industry has brought various environmental, economic and social challenges. Consequently, shrimp farming is a risky business and local inhabitants have relied on various strategies to cope with these challenges. Risk mitigation in shrimp production and labor migration are the two important strategies of local inhabitants for securing their livelihoods. Water pollution and poor quality post-larvae shrimp are direct consequences of market-oriented production. PMID:24386621

  15. Bridging the Past with Today's Microwave Remote Sensing: A Case Study of Long Term Inundation Patterns in the Mekong River Delta

    NASA Astrophysics Data System (ADS)

    Jensen, K.; McDonald, K. C.; Schroeder, R.; Tessler, Z. D.

    2015-12-01

    Surface inundation extent and its predictability vary tremendously across the globe. This dynamic is being and has been captured by three general categories of satellite imagery: 1) low-spatial-resolution microwave sensors with global coverage and a long record of observations (e.g., SSM/I), 2) optical sensors with high spatial and temporal resolution and global coverage, but with cloud contamination (e.g. MODIS), and 3) in more ''snapshot'' form by high-resolution synthetic aperture radar (SAR) sensors. We explore the ability to bridge techniques that can exploit the higher spatial resolution of more recent data products back in time with the help of the temporal evolution of lower resolution products. We present a study of long term (20+ year) inundation patterns in the Mekong River Delta using baseline observations from the Surface Water Microwave Product Series (SWAMPS), an inundation area fraction product derived at 25km scale from active and passive microwave instruments (ERS, QuikSCAT, ASCAT, and SSM/I) that spans from Jan. 1992 to Jun. 2015. Every hydrological basin has unique characteristics - such as its topography, land cover / land use, and space-time variability - thus, a downscaling algorithm needs to take into account these idiosyncrasies. We merge SWAMPS with topographical information derived from 30m SRTM DEM, river networks from USGS HydroSHEDS, and assess the best statistical procedure to "learn" from two sets of classified SAR data: (1) L-band imaging radar from ALOS PALSAR, 2007-2010, and (2) C-band imagery from the Sentinel-1 mission (2014 to present). We present a comparison of retrospective downscaled flood extent with Landsat imagery and recent observations from SMAP. With a higher spatial resolution of past flooding extent, we can improve our understanding of how delta surface hydrology responds to local and regional events. This is important both in the short-term for accurate flood prediction, as well as on longer-term planning horizons.

  16. Aerobic Decomposition and Organic Amendments Effects on Grain Yield of Triple-Cropped Rice in the Mekong Delta, Vietnam

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil aeration during decomposition of incorporated crop residues and application of organic amendments might help improve soil quality and rice yield for sustainable intensive rice production. A field experiment was conducted on triple-cropped rice during three consecutive crops with five treatments...

  17. Application of co-anaerobic digester's effluent for sustainable agriculture and aquaculture in the Mekong Delta, Vietnam.

    PubMed

    Nguyen, V C N; Fricke, K

    2015-01-01

    This investigation studied the application of digester effluent from co-digestion of pig manure and spent mushroom substrate as a fertilizer for leaf mustard planting and as feed for Tilapia fish growing. The fish raising experiment was set up in 1 × 1 × 1 m hapa conditions (triplicate for each treatment) with the density of 10 individiual per hapa; the fish weight and length were measured every 10 days for 50 continuous days. The leaf mustard was planted in real conditions at farmer's garden with normal cultivation style, and the weight and length of the plant were measured four times during the growing period. The study result shows that the harvest yield of leaf mustard fertilized by the digester effluent was 5.4 times higher than that by an inorganic fertilizer (IF). In addition to its contribution to a higher yield, the digester effluent accelerated the flower formation and shortened cultivation duration. For Tilapia fish culture, the growing rate of fish in the treatments supplied with 50% digester effluent + 50% commercial food (CF) was not significantly different in comparison to the fish cultivation with 100% CF. The result strongly confirms that the digester effluent from a co-digestion biogas plant of pig dung and spent mushroom compost is possible to be used as an organic fertilizer well for not only vegetable planting but also fish culture. PMID:26510614

  18. Managing Tradeoffs between Hydropower and the Environment in the Mekong River Basin

    NASA Astrophysics Data System (ADS)

    Loucks, Daniel P.; Wild, Thomas B.

    2015-04-01

    Hydropower dams are being designed and constructed at a rapid pace in the Mekong/Lancang River basin in Southeast Asia. These reservoirs are expected to trap significant amounts sediment, decreasing much of the river's capability to transport nutrients and maintain its geomorphology and habitats. We apply a simulation model for identifying and evaluating alternative dam siting, design and operating policy (SDO) options that could help maintain more natural sediment regimes downstream of dams and for evaluating the effect of these sediment-focused SDO strategies on hydropower production and reliability. We apply this approach to the planned reservoirs that would prevent a significant source of sediment from reaching critical Mekong ecosystems such as Cambodia's Tonle Sap Lake and the Mekong delta in Vietnam. Model results suggest that various SDO modifications could increase sediment discharge from this site by 300-450% compared to current plans, but a 30-55% loss in short-term annual energy production depending on various configurations of upstream reservoirs. Simulation results also suggest that sediment management-focused reservoir operating policies could cause ecological damage if they are not properly implemented.

  19. Language Education, Economic Development and Participation in the Greater Mekong Subregion

    ERIC Educational Resources Information Center

    Bruthiaux, Paul

    2008-01-01

    The Mekong has long attracted interest although it remains economically insignificant. A group of riparian states known as the Greater Mekong Subregion (GMS)--Cambodia, Laos, Myanmar, Thailand, Vietnam and Yunnan Province (China)--now manage aspects of regional development including trade, water management and education. Standard GMS discourse…

  20. Estimation of daily global solar radiation in Vietnamese Mekong Delta area: A combinational application of statistical downscaling method and Bayesian inference

    NASA Astrophysics Data System (ADS)

    Iizumi, T.; Nishimori, M.; Yokozawa, M.; Kotera, A.; Khang, N. D.

    2008-12-01

    Long-term daily global solar radiation (GSR) data of the same quality in the 20th century has been needed as a baseline to assess the climate change impact on paddy rice production in Vietnamese Mekong Delta area (MKD: 104.5-107.5oE/8.2-11.2oN). However, though sunshine duration data is available, the accessibility of GSR data is quite poor in MKD. This study estimated the daily GSR in MKD for 30-yr (1978- 2007) by applying the statistical downscaling method (SDM). The estimates of GSR was obtained from four different sources: (1) the combined equations with the corrected reanalysis data of daily maximum/minimum temperatures, relative humidity, sea level pressure, and precipitable water; (2) the correction equation with the reanalysis data of downward shortwave radiation; (3) the empirical equation with the observed sunshine duration; and (4) the observation at one site for short term. Three reanalysis data, i.e., NCEP-R1, ERA-40, and JRA-25, were used. Also the observed meteorological data, which includes many missing data, were obtained from 11 stations of the Vietnamese Meteorological Agency for 28-yr and five stations of the Global Summary of the Day for 30-yr. The observed GSR data for 1-yr was obtained from our station. Considering the use of data with many missing data for analysis, the Bayesian inference was used for this study, which has the powerful capability to optimize multiple parameters in a non-linear and hierarchical model. The Bayesian inference provided the posterior distributions of 306 parameter values relating to the combined equations, the empirical equation, and the correction equation. The preliminary result shows that the amplitude of daily fluctuation of modeled GSR was underestimated by the empirical equation and the correction equation. The combination of SDM and Bayesian inference has a potential to estimate the long- term daily GSR of the same quality even though in the area where the observed data is quite limited.

  1. Dynamic Emulation Modeling of irrigation water deficit in the Red-Thai Binh River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Dinh, Q.; Cassaro, L.; Micotti, M.; Soncini-Sessa, R.

    2013-12-01

    real-world case study: the Red-Thai Binh River Delta in Vietnam. It is a large and complex river system, supplied by five unregulated rivers and four large multi-purpose reservoirs, the operating rules of which have to be designed. In order to ascertain the effects of their regulation on the WD in the Delta, a Mike11 model was calibrated and validated. It describes 320 rivers and canals for a total length of 4200 km, 11 irrigation districts and many structures, among which 88 sluice gates and 302 irrigation water intakes (simulated as controlled pumps). Its inputs are the four reservoirs releases, the non-regulated flows of the five rivers, the sea levels at the nine river mouths, the water demand at each one of the irrigation water intakes. The considered outputs are the daily WD in the 11 districts. The dimension of the state vector of the model is of the order of 16,000. From the high dimensional Mike11, a low dimensional (11 dimension) DEMo model was identified that mimics very well (R2=0.95) the WDs as computed by the Mike11 model. The DEMo model will be later on embedded within a large multi-objective optimal control problem to design the operating rules of the four reservoirs.

  2. Impact of the Hoa Binh dam (Vietnam) on water and sediment budgets in the Red River basin and delta

    NASA Astrophysics Data System (ADS)

    Vinh, V. D.; Ouillon, S.; Thanh, T. D.; Chu, L. V.

    2014-10-01

    The Hoa Binh dam (HBD), located on a tributary of the Red River in Vietnam, has a capacity of 9.45 × 109 m3 and was commissioned in December 1988. Although it is important for flood prevention, electricity production and irrigation in northern Vietnam, the Hoa Binh dam has also highly influenced the suspended sediment distribution in the lower Red River basin, in the delta and in the coastal zone. Its impact was analysed from a 50-year data set of water discharge and suspended sediment concentration (1960-2010), and the distribution of water and sediment across the nine mouths of the delta was simulated using the MIKE11 numerical model before and after the dam settlement. Although water discharge at the delta inlet decreased by only 9%, the yearly suspended sediment flux dropped, on average, by 61% at Son Tay near Hanoi (from 119 to 46 × 106 t yr-1). Along the coast, reduced sedimentation rates are coincident with the lower sediment delivery observed since the impoundment of the Hoa Binh dam. Water regulation has led to decreased water discharge in the wet season (-14% in the Red River at Son Tay) and increased water discharge in the dry season (+12% at the same station). The ratios of water and suspended sediment flows, as compared to the total flows in the nine mouths, increased in the northern and southern estuaries and decreased in the central, main Ba Lat mouth. The increasing volume of dredged sediments in the Haiphong harbour is evidence of the silting up of the northern estuary of Cam-Bach Dang. The effect of tidal pumping on enhanced flow occurring in the dry season and resulting from changed water regulation is discussed as a possible cause of the enhanced siltation of the estuary after Hoa Binh dam impoundment.

  3. Managing flow, sediment, and hydropower regimes in the Sre Pok, Se San, and Se Kong Rivers of the Mekong basin

    NASA Astrophysics Data System (ADS)

    Wild, Thomas B.; Loucks, Daniel P.

    2014-06-01

    The Lancang/Mekong River Basin is presently undergoing a period of rapid hydropower development. In its natural undeveloped state, the river transports about 160 million metric tons of sediment per year, maintaining the geomorphologic features of the basin, sustaining habitats, and transporting the nutrients that support ecosystem productivity. Despite the importance of sediment in the river, currently little attention is being paid to reservoir sediment trapping. This study is devoted to assessing the potential for managing sediment and its impact on energy production in the Se San, Sre Pok, and Se Kong tributaries of the Mekong River. These tributaries drain a set of adjacent watersheds that are important with respect to biodiversity and ecological productivity, and serve as a significant source of flow and sediment to the mainstream Mekong River. A daily sediment transport model is used to assess tradeoffs among energy production and sediment and flow regime alteration in multiple reservoir systems. This study finds that eventually about 40%-80% of the annual suspended sediment load may be trapped in reservoirs. Clearly, these reservoirs will affect the rivers' sediment regimes. However, even after 100 years of simulated sedimentation, reservoir storage capacities and hydropower production at most reservoir sites are not significantly reduced. This suggests that the strongest motivation for implementing measures to reduce trapped sediment is their impact not on hydropower production but on fish migration and survival and on sediment-dependent ecosystems such as the Vietnam Delta and Cambodia's Tonle Sap Lake.

  4. Micronutrient composition and nutritional importance of gathered vegetables in Vietnam.

    PubMed

    Ogle, B M; Dao, H T; Mulokozi, G; Hambraeus, L

    2001-11-01

    This article presents the nutrient composition and nutritional contribution of naturally occurring vegetables (NOV) in four villages in Vietnam. The frequency of consumption and quantities eaten were evaluated within the overall diet of 101 and 110 women in the Mekong Delta (flood period and rainy season, respectively) and of 103 women in the Central Highlands (rainy season). The concentrations of Ca, Fe and Zn were analysed in 28 species, and presence of tannins and phytic acid in 19 species. Provitamin carotenoids were determined in 11 species. Over 90% of the women consumed NOV, and they contributed 43, 72 and 75% (Central Highlands, Mekong rainy and Mekong flood period, respectively) of the total quantities of vegetables eaten. Aquatic species such as lpomoea aquatica and Limnocharis flava, and terrestrial vegetables such as Schismattoglottis calyptrata, were among the most commonly consumed vegetables. They were eaten in mean daily quantities exceeding 50 g and had high concentrations of Ca, Fe and beta-carotene. Other major aquatic vegetables included the stems of Eleocharis sp., Nelumbo nucifera and Nymphea lotus, all of which were used as salad vegetables and had relatively low nutrient density. The problems of assessing the current role of NOV due to lack of data on intakes in the context of the overall diets, as well as data on their composition, are addressed. PMID:11570015

  5. Cloud Cover and Wildfire Variations in Vietnam and Southeast Asia

    NASA Astrophysics Data System (ADS)

    Lasko, K.

    2015-12-01

    Monitoring fires from space is constrained by cloud cover, particularly in tropical regions. Cloud cover-fire variations were assessed using the CERES SSF1Deg and MODIS active fire (MCD14ML) products in Vietnam and Southeast Asia. Twelve years (2003-2014) of data have been analyzed spatially and temporally at four spatial scales: a) country level; b). 1x1 degree scale; c). land cover type; d). regions. Country-level results suggested Vietnam having the highest monthly cloud cover (72.37%) followed by Cambodia (69.69%), Laos (67.64%), Thailand (67.58%), and Myanmar (59.90%). Strong negative correlation between cloud cover and MODIS active fires has been observed during the biomass burning months (Jan-Apr). Of the different countries, Vietnam also had the lowest monthly fire detections. Pixel by pixel spatial correlation at 1x1 degree suggested negative fire-cloud relationships over the Red River Delta of Vietnam, the forests of northern Laos, and agriculture-dominated peninsulas of Thailand and Myanmar. Among the different land cover types, the average monthly cloud cover varied between 64% - 66%. Further, results from daily data showed the Red River Delta to have consistently more cloud cover (20-40% more) than the Mekong River Delta in Vietnam, with fewer fire detections in the former than the latter. The study highlights potential fire under-detection due to clouds. Our results highlight spatial and temporal variations in cloud-fire relationships and the difficulty of using optical data for fire detection and characterization in persistently cloudy regions.

  6. Genetic polymorphisms in glutathione S-transferase (GST) superfamily and arsenic metabolism in residents of the Red River Delta, Vietnam

    SciTech Connect

    Agusa, Tetsuro; Iwata, Hisato; Fujihara, Junko; Kunito, Takashi; Takeshita, Haruo; Tu Binh Minh; Pham Thi Kim Trang; Pham Hung Viet; Tanabe, Shinsuke

    2010-02-01

    To elucidate the role of genetic factors in arsenic metabolism, we investigated associations of genetic polymorphisms in the members of glutathione S-transferase (GST) superfamily with the arsenic concentrations in hair and urine, and urinary arsenic profile in residents in the Red River Delta, Vietnam. Genotyping was conducted for GST omega1 (GSTO1) Ala140Asp, Glu155del, Glu208Lys, Thr217Asn, and Ala236Val, GST omega2 (GSTO2) Asn142Asp, GST pi1 (GSTP1) Ile105Val, GST mu1 (GSTM1) wild/null, and GST theta1 (GSTT1) wild/null. There were no mutation alleles for GSTO1 Glu208Lys, Thr217Asn, and Ala236Val in this population. GSTO1 Glu155del hetero type showed higher urinary concentration of As{sup V} than the wild homo type. Higher percentage of DMA{sup V} in urine of GSTM1 wild type was observed compared with that of the null type. Strong correlations between GSTP1 Ile105Val and arsenic exposure level and profile were observed in this study. Especially, heterozygote of GSTP1 Ile105Val had a higher metabolic capacity from inorganic arsenic to monomethyl arsenic, while the opposite trend was observed for ability of metabolism from As{sup V} to As{sup III}. Furthermore, other factors including sex, age, body mass index, arsenic level in drinking water, and genotypes of As (+ 3 oxidation state) methyltransferase (AS3MT) were also significantly co-associated with arsenic level and profile in the Vietnamese. To our knowledge, this is the first study indicating the associations of genetic factors of GST superfamily with arsenic metabolism in a Vietnamese population.

  7. Genetic polymorphisms in AS3MT and arsenic metabolism in residents of the Red River Delta, Vietnam

    SciTech Connect

    Agusa, Tetsuro; Iwata, Hisato Fujihara, Junko; Kunito, Takashi; Takeshita, Haruo; Minh, Tu Binh; Trang, Pham Thi Kim; Viet, Pham Hung; Tanabe, Shinsuke

    2009-04-15

    To elucidate the role of genetic factors in arsenic (As) metabolism, we studied associations of single nucleotide polymorphisms (SNPs) in As (+ 3 oxidation state) methyltransferase (AS3MT) with the As concentrations in hair and urine, and urinary As profile in residents in the Red River Delta, Vietnam. Concentrations of total As in groundwater were 0.7-502 {mu}g/l. Total As levels in groundwater drastically decreased by using sand filter, indicating that the filter could be effective to remove As from raw groundwater. Concentrations of inorganic As (IAs) in urine and total As in hair of males were higher than those of females. A significant positive correlation between monomethylarsonic acid (MMA)/IAs and age in females indicates that older females have higher methylation capacity from IAs to MMA. Body mass index negatively correlated with urinary As concentrations in males. Homozygote for SNPs 4602AA, 35991GG, and 37853GG, which showed strong linkage disequilibrium (LD), had higher percentage (%) of dimethylarsinic acid (DMA) in urine. SNPs 4740 and 12590 had strong LD and associated with urinary %DMA. Although SNPs 6144, 12390, 14215, and 35587 comprised LD cluster, homozygotes in SNPs 12390GG and 35587CC had lower DMA/MMA in urine, suggesting low methylation capacity from MMA to DMA in homo types for these SNPs. SNPs 5913 and 8973 correlated with %MMA and %DMA, respectively. Heterozygote for SNP 14458TC had higher MMA/IAs in urine than TT homozygote, indicating that the heterozygote may have stronger methylation ability of IAs. To our knowledge, this is the first study on the association of genetic factors with As metabolism in Vietnamese.

  8. Genesis of economic relevant fresh groundwater resources in Pleistocene/ Neogene aquifers in Nam Dinh (Red River Delta, Vietnam).

    NASA Astrophysics Data System (ADS)

    Wagner, F.; Ludwig, R. R.; Noell, U.; Hoang, H. V.; Pham, N. Q.; Larsen, F.; Lindenmaier, F.

    2012-04-01

    In the Southern Red River Delta (Nam Dinh Province, Vietnam), a local lens of low saline pore water of high quality has been identified in unconsolidated Pleistocene and Neogene aquifers, which are regionally known to contain brackish and saline pore waters. Since the 1990ies, ongoing overexploitation of the fresh groundwater results in decreasing GW heads up to 0.6 m/a and the development of a regional abstraction cone. The presented study focuses on distribution and genesis of fresh and saline pore waters and reflects the results in frame of the regional hydrogeological context. Observations of the geological structure and groundwater dynamics combined with hydrochemical and isotopic studies suggest adjacent Triassic hard rock aquifers as the major source for fresh Pleistocene and Neogene groundwater. Salinization status in the economically most relevant Pleistocene aquifer has been studied based on archive and new hydrochemical and geophysical data. Own hydrochemical field studies as well as laboratory measurements of the specific resistivity of dry sediment samples allow the translation of induction logging data from existing monitoring wells into vertical pore water salinity profiles. This approach suggests the regional occurrence of saline pore water in shallow Holocene sediments in the working area, as confirmed by pore water studies in Hoan et al. (2010). Interpretation of induction logging and stable isotope data suggest vertical diffusion of saline pore water in shallow Holocene sediments as a source for high saline pore water in deeper aquifers. Analytical diffusion modeling for a period of 3000 years confirms that vertical diffusion of Holocene paleo-sea water can explain saline pore water in Pleistocene and Neogene aquifers in a stagnant environment. The constant influx of fresh groundwater from adjacent Triassic hard rocks results in flushing of the primary Pleistocene and Neogene pore water and inhibits the infiltration of saline water from marine

  9. Fish-borne zoonotic trematodes in cultured and wild-caught freshwater fish from the Red River Delta, Vietnam.

    PubMed

    Phan, Van Thi; Ersbøll, Annette Kjaer; Bui, Te Quang; Nguyen, Hang Thi; Murrell, Darwin; Dalsgaard, Anders

    2010-11-01

    Nam Dinh province in Red River Delta, Vietnam, is an endemic area for the human liver fluke Clonorchis sinensis, but little is known about its occurrence in the fish intermediate host in this region. A cross-sectional study was carried out to identify fish-borne zoonotic trematodes (FZT) species diversity and to estimate the prevalence and infection densities of FZT in three major types of fish: cultured species and self-recruiting species from family ponds and wild-caught species from irrigation canals in Nam Dinh province. A total of 714 wild-caught fish from canals and 829 fish from family ponds were examined for FZT infection. Only a single fish from a pond was infected with Cl. sinensis. The intestinal fluke Haplorchis pumilio was very common and found in more than 50% of fish irrespective of origin. Four other intestinal FZT species were found at low prevalence (<4.0%) except Procerovum varium, which was found in 14.4% of wild-caught fish. There was no significant difference (p > 0.05) in FZT prevalence in cultured fish (64.3%) compared with wild-caught fish (68.9%), nor between cultured fish species (65.1%) and self-recruiting species obtained from ponds (58.1%). The prevalence of FZT in silver carp (Hypophthalmichthys molitrix) (82.7%), grass carp (Ctenopharyngodon idellus) (76.9%), and mrigal (Cirrhinus mrigala) (63.8%) was significantly higher than that in rohu (Labeo rohita) (49.1%) (p < 0.001). The density of FZT metacercariae in fish from canals (0.56 metacercariae/g) was significantly higher (p < 0.001) than that in fish from ponds (0.03 metacercariae/g). The frequent occurrence of intestinal flukes in all fish types indicates that wild-caught and cultured fish are equally at risk of infection with FZT, particularly in species commonly used in Nam Dinh to prepare raw fish dishes. These results underscore the need for greater awareness of the risk from raw fish dishes among public health agencies and consumers. PMID:20370427

  10. Real and Virtual Experiential Learning on the Mekong: Field Schools, e-Sims and Cultural Challenge

    ERIC Educational Resources Information Center

    Hirsch, Philip; Lloyd, Kate

    2005-01-01

    This paper describes two innovative and linked approaches to teaching and student learning in the environmental and development geography of the Mekong region, a region remote from students' normal experiential options. The first approach is field-based learning through Field Schools carried out in Vietnam, Laos and Thailand. The second approach…

  11. Recent social and biogeophysical changes in the Ganges-Brahmaputra-Meghna, Mekong, and Amazon deltas as inputs into evolutionary policy-making.

    NASA Astrophysics Data System (ADS)

    de Araujo Barbosa, C. C.; Hossain, S.; Szabo, S.; Matthews, Z.; Heard, S.; Dearing, J.

    2014-12-01

    Policy-making in social-ecological systems increasingly looks to iterative, evolutionary approaches that can address the inherent complexity of interactions between human wellbeing, agricultural and aquacultural production, and ecosystem services. Here we show how an analysis of available time-series in delta regions over past decades can provide important insight into the social-ecological system dynamics that result from the complexity. The presentation summarises the recent changes for major elements of each social-ecological system, for example demography, economy, health, climate, food, and water. Time-series data from official statistics, monitoring programmes and sequential satellite imagery are analysed to define the range of trends, the presence of change points, slow and fast variables, and the significant drivers of change. For example, in the Bangladesh delta zone, increasing gross domestic product and per capita income levels since the 1980s mirror rising levels of food and inland fish production. In contrast, non-food ecosystem services such as water availability, water quality and land stability have deteriorated. As a result, poverty alleviation is associated with environmental degradation. Trends in indicators of human wellbeing and ecosystem services point to widespread non-stationary dynamics governed by slowly changing variables with increased probability of systemic threshold changes/tipping points in the near future. We conclude by examining how the findings could feed into new management tools, such as system dynamic models and assessments of safe operating spaces. Such tools have the potential to help create policies that deliver alternative and sustainable paths for land management while accommodating social and environmental change.

  12. Dealing with the safety paradox of delta-branches closure; a geomorphology study

    NASA Astrophysics Data System (ADS)

    Sloff, C.; Tromp, R.; Sieben, A.

    2013-12-01

    Closing off estuaries by dams is a conventional solution to reduce flood risks and salt intrusion in river deltas. However, if not all branches are closed, residual tidal currents develop or increase in connecting channels between the closed and open branches. These channels start to erode, causing bank instability and possible failure of levees. Hence, paradoxically, the intended increase in safety by this closure creates a new threat with increased flood risks. We illustrate this for existing channel erosion and dike stability problems in the Dutch Rhine River delta in the Netherlands, as well as for proposed future closure works in the Mekong River in Vietnam. Crucial for assessing and dealing with the erosion problems, is a proper prediction of flow conditions and of bed erodibility. The channels incise ancient deltaic deposits, consisting of diverse sections and layers of sand, clay and peat with diverse states of compaction. In the presented studies we show how we applied Delft3D to model the full delta, with all relevant dynamics and complex interactions between tidal flow and river discharges. For the Dutch situation, we simulated the long-term fate of the eroding interconnecting channels, applying a detailed description of subsurface heterogeneous erodibility (space and depth varying). Since these rivers are incising slowly in clay and peat beds covering highly-erodible sand layers, alternate sections occur of undersupplied ';fixed' beds, and of very deep scour holes. For the Vietnam case, we show how the location of a barrier and operation of gates, can be used to control both the salinity intrusion and channel erosion for the Mekong delta. Although the morphology studies for the Dutch delta with high-density data availability obviously justify a detailed Delft3D approach, it is shown that even in the Mekong delta with poor data quality, a coarse-grid large-scale Delft3D model can provide the answers necessary for planning the closure works and potential

  13. Enhancing Floodplain Management in the Lower Mekong River Basin Using Vegetation and Water Cycle Satellite Observations

    NASA Astrophysics Data System (ADS)

    Bolten, J. D.; Spruce, J.; Wilson, R.; Strauch, K.; Doyle, T.; Srinivan, R.; Lakshmi, V.; Gupta, M.

    2014-12-01

    The Lower Mekong River Basin shared by China, Burma, Laos, Thailand, Cambodia, and Vietnam, is considered the lifeblood of Southeast Asia. The Mekong Basin is subject to large hydrological fluctuations on a seasonal and inter-annual basis. The basin remains prone to severe annual floods that continue to cause widespread damage and endanger food security and the livelihood of the millions who dwell in the region. Also the placement of newly planned dams primarily for hydropower in the Lower Mekong Basin may cause damaging social, agriculture and fisheries impacts to the region where we may now likely be at a critical 'tipping point'. The primary goal of this project is to apply NASA and USGS products, tools, and information for improved flood and water management in the Lower Mekong River Basin to help characterize, understand, and predict future changes on the basin. Specifically, we are providing and helping transfer to the Mekong River Commission (MRC) and the member countries of Thailand, Cambodia, Lao, Vietnam, and Burma the enhanced Soil and Water Assessment Tool (SWAT) using remotely sensed surface, ground water, and root zone soil moisture along with improved Land Use and Land Cover (LULC) maps. In order to estimate the flood potential and constrain the SWAT Available Water Capacity model parameter over the region, we are assimilated GRACE Terrestrial Water Storage observations into the Catchment Land Surface Model. In addition, a Graphic Visualization Tool (GVT) as been developed to work in concert with the output of the SWAT model parameterized for the Mekong Basin as an adjunct tool of the MRC Decision Support Framework. The project requires a close coordination of the development and assessment of the enhanced MRC SWAT with the guidance of MRC resource managers and technical advisors. This presentation will evaluate the skill of the enhanced SWAT model using qualitative (i.e., MODIS change detection) and quantitative (e.g., streamflow) metrics over one

  14. Dilemmas in examining understanding of nature of science in Vietnam

    NASA Astrophysics Data System (ADS)

    Thao-Do, Thi Phuong; Yuenyong, Chokchai

    2015-12-01

    Scholars proved nature of science (NOS) has made certain contributions to science teaching and learning. Nonetheless, what, how and how much NOS should be integrated in the science curriculum of each country cannot be a benchmark, due to the influence of culture and society. Before employing NOS in a new context, it should be carefully studied. In assessing views of NOS in Vietnam, a developing country with Eastern culture where the NOS is not consider a compulsory learning outcome, there are several issues that researchers and educators should notice to develop an appropriate instrument that can clearly exhibit a NOS view of Vietnamese. They may include: time for the survey; length, content, type, and terms of the questionnaire; Vietnamese epistemology and philosophy; and some other Vietnamese social and cultural aspects. The most important reason for these considerations is that a Vietnamese view of NOS and NOS assessment possibly differs from the Western ideas due to the social and cultural impact. As a result, a Western assessment tool may become less effective in an Eastern context. The suggestions and implications in this study were derived from a prolonged investigation on Vietnamese science teacher educators and student teachers of School of Education, at Can Tho University, a State University in Mekong Delta region, Vietnam.

  15. The Potential of Time Series Based Earth Observation for the Monitoring of Large River Deltas

    NASA Astrophysics Data System (ADS)

    Kuenzer, C.; Leinenkugel, P.; Huth, J.; Ottinger, M.; Renaud, F.; Foufoula-Georgiou, E.; Vo Khac, T.; Trinh Thi, L.; Dech, S.; Koch, P.; Le Tissier, M.

    2015-12-01

    Although river deltas only contribute 5% to the overall land surface, nearly six hundred million people live in these complex social-ecological environments, which combine a variety of appealing locational advantages. In many countries deltas provide the major national contribution to agricultural and industrial production. At the same time these already very dynamic environments are exposed to a variety of threats, including the disturbance and replacement of valuable ecosystems, increasing water, soil, and air pollution, human induced land subsidence, sea level rise, as well upstream developments impacting water and sediment supplies. A constant monitoring of delta systems is thus of utmost relevance for understanding past and current land surface change and anticipating possible future developments. We present the potential of Earth Observation based analyses and derived novel information products that can play a key role in this context. Along with the current trend of opening up numerous satellite data archives go increasing capabilities to explore big data. Whereas in past decades remote sensing data were analysed based on the spectral-reflectance-defined 'finger print' of individual surfaces, we mainly exploit the 'temporal fingerprints' of our land surface in novel pathways of data analyses at differing spatial-, and temporally-dense scales. Following our results on an Earth Observation based characterization of large deltas globally, we present in depth results from the Mekong Delta in Vietnam, the Yellow River Delta in China, the Niger Delta in Nigeria, as well as additional deltas, focussing on the assessment of river delta flood and inundation dynamics, river delta coastline dynamics, delta morphology dynamics including the quantification of erosion and accretion processes, river delta land use change and trends, as well as the monitoring of compliance to environmental regulations.

  16. DELTAE

    SciTech Connect

    Ward, W.C.; Swift, G.W. )

    1993-11-01

    In thermoacoustic engines and refrigerators, and in many simple acoustic systems, a one dimensional wave equation determines the spatial dependence of the acoustic pressure and velocity. DELTAE numerically integrates such wave equations in the acoustic approximation, in gases or liquids, in user-defined geometries. Boundary conditions can include conventional acoustic boundary conditions of geometry and impedance, as well as temperature and thermal power in thermoacoustic systems. DELTAE can be used easily for apparatus ranging from simple duct networks and resonators to thermoacoustic engines refrigerators and combinations thereof. It can predict how a given apparatus will perform, or can allow the user to design an apparatus to achieve desired performance. DELTAE views systems as a series of segments; twenty segment types are supported. The purely acoustic segments include ducts and cones, and lumped impedances including compliances, series impedances, and endcaps. Electroacoustics tranducer segments can be defined using either frequency-independent coefficients or the conventional parameters of loudspeaker-style drivers: mass, spring constant, magnetic field strength, etc. Tranducers can be current driven, voltage driven, or connected to an electrical load impedance. Thermoacoustic segment geometries include parallel plates, circular and rectangular pores, and pin arrays. Side branches can be defined with fixed impedances, frequency-dependent radiation impedances, or as an auxiliary series of segments of any types. The user can select working fluids from among air, helium, neon, argon, hydrogen, deuterium, carbon dioxide, nitrogen, helium-argon mixtures, helium-xenon mixtures, liquid sodium, and eutectic sodium-potassium. Additional fluids and solids can be defined by the user.

  17. Temporal change and its spatial variety on land surface temperature and land use changes in the Red River Delta, Vietnam, using MODIS time-series imagery.

    PubMed

    Van Nguyen, On; Kawamura, Kensuke; Trong, Dung Phan; Gong, Zhe; Suwandana, Endan

    2015-07-01

    Temporal changes in the land surface temperature (LST) in urbanization areas are important for studying an urban heat island (UHI) and regional climate change. This study examined the LST trends under different land use categories in the Red River Delta, Vietnam, using the Moderate Resolution Imaging Spectroradiometer (MODIS) LST product (MOD11A2) and land cover type product (MCD12Q1) for 11 years (2002-2012). Smoothened time-series MODIS LST data were reconstructed by the Harmonic Analysis of Time Series (HANTS) algorithm. The reconstructed LST (maximum and minimum temperatures) was assessed using the hourly air temperature dataset in two land-based meteorological stations provided by the National Climatic Data Center (NCDC). Significant correlation was obtained between MODIS LST and the air temperature for the daytime (R (2) = 0.73, root mean square error [RMSE] = 1.66 °C) and night time (R (2) = 0.84, RMSE = 1.79 °C). Statistical analysis also showed that LST trends vary strongly depending on the land cover type. Forest, wetland, and cropland had a slight tendency to decline, whereas cropland and urban had sharper increases. In urbanized areas, these increasing trends are even more obvious. This is undeniable evidence of the negative impact of urbanization on a surface urban heat island (SUHI) and global warming. PMID:26113204

  18. Molecular Breeding to Improve Salt Tolerance of Rice (Oryza sativa L.) in the Red River Delta of Vietnam

    PubMed Central

    Linh, Le Hung; Linh, Ta Hong; Xuan, Tran Dang; Ham, Le Huy; Ismail, Abdelbagi M.; Khanh, Tran Dang

    2012-01-01

    Rice is a stable food in Vietnam and plays a key role in the economy of the country. However, the production and the cultivating areas are adversely affected from the threats of devastation caused by the rise of sea level. Using marker-assisted backcrossing (MABC) to develop a new salt tolerance rice cultivar is one of the feasible methods to cope with these devastating changes. To improve rice salt tolerance in BT7 cultivar, FL478 was used as a donor parent to introgress the Saltol QTL conferring salt tolerance into BT7. Three backcrosses were conducted and successfully transferred positive alleles of Saltol from FL478 into BT7. The plants numbers IL-30 and IL-32 in BC3F1 population expected recurrent genome recovery of up to 99.2% and 100%, respectively. These selected lines that carried the Saltol alleles were screened in field for their agronomic traits. All improved lines had Saltol allele similar to the donor parent FL478, whereas their agronomic performances were the same as the original BT7. We show here the success of improving rice salt tolerance by MABC and the high efficiency of selection in early generations. In the present study, MABC has accelerated the development of superior qualities in the genetic background of BT7. PMID:23326259

  19. Survey for zoonotic liver and intestinal trematode metacercariae in cultured and wild fish in An Giang Province, Vietnam

    PubMed Central

    Thu, Nguyen Diem; Dalsgaard, Anders; Loan, Ly Thi Thanh

    2007-01-01

    Although Vietnam has a high risk of fishborne zoonotic trematode (FZT) infections for humans, little information exists on the epidemiology of these infections in the country's fish. Because of the importance of cultured catfish and snakehead production in An Giang province, a major production area in the Mekong Delta of Vietnam, a survey for FZTs was carried out in randomly selected fish farms between June 2005 and March 2006. For comparison, wild fish from the same area were also surveyed. A total of 852 cultured fish from 4 districts were collected and examined by pepsin digestion to determine their FZT infection status. In Tra catfish, the prevalence of all types of metacercariae was 2.6%, of which the prevalence of Haplorchis pumilio was 0.7%. The overall prevalence of metacercariae in wild fish was 30.6%, of which 10.3% harbored zoonotic species: H. pumilio (2.8%) and Procerovum sp. (5.6%). The prevalence of Opisthorchis metacercariae, which were diagnosed as O. viverrini, was 1.9%. No metacercariae were found in cultured snakehead fish, although wild-caught snakehead fish had a FZT prevalence of 10.3%: 5.1% were O. viverrini; 2.6% H. pumilio; and 2.6% were Procerovum sp. These are the first reports of H. pumilio, Procerovum sp., and O. viverrini metacercariae in Vietnamese fish. These results indicate that consumption of improperly prepared fish represents a significant risk of acquiring FZTs in this south Vietnam region. PMID:17374978

  20. Risk factors of highly pathogenic avian influenza H5N1 occurrence at the village and farm levels in the Red River Delta Region in Vietnam.

    PubMed

    Desvaux, S; Grosbois, V; Pham, T T H; Fenwick, S; Tollis, S; Pham, N H; Tran, A; Roger, F

    2011-12-01

    A case-control study at both village and farm levels was designed to investigate risk factors for highly pathogenic avian influenza H5N1 during the 2007 outbreaks in one province of Northern Vietnam. Data related to human and natural environments, and poultry production systems were collected for 19 case and 38 unmatched control villages and 19 pairs of matched farms. Our results confirmed the role of poultry movements and trading activities. In particular, our models found that higher number of broiler flocks in the village increased the risk (OR = 1.49, 95% CI: 1.12-1.96), as well as the village having at least one poultry trader (OR = 11.53, 95% CI: 1.34-98.86). To a lesser extent, in one of our two models, we also identified that increased density of ponds and streams, commonly used for waterfowl production, and greater number of duck flocks in the village also increased the risk. The higher percentage of households keeping poultry, as an indicator of households keeping backyard poultry in our study population, was a protective factor (OR = 0.95, 95% CI: 0.91-0.98). At the farm level, three risk factors at the 5% level of type I error were identified by univariate analysis: a greater total number of birds (P = 0.006), increase in the number of flocks having access to water (P = 0.027) and a greater number of broiler flocks in the farm (P = 0.049). Effect of vaccination implementation (date and doses) was difficult to investigate because of a poor recording system. Some protective or risk factors with limited effect may not have been identified owing to our limited sample size. Nevertheless, our results provide a better understanding of local transmission mechanisms of HPAI H5N1 in one province of the Red River Delta region in Vietnam and highlight the need to reduce at-risk trading and production practices. PMID:21545692

  1. Data sharing in international transboundary contexts: The Vietnamese perspective on data sharing in the Lower Mekong Basin

    NASA Astrophysics Data System (ADS)

    Thu, Hang Ngo; Wehn, Uta

    2016-05-01

    Transboundary data sharing is widely recognised as a necessary element in the successful handling of water-related climate change issues, as it is a means towards integrated water resources management (IWRM). However, in practice it is often a challenge to achieve it. The Mekong River Commission (MRC), an inter-governmental agency established by Cambodia, Lao PDR, Thailand and Vietnam, has adopted IWRM in its water strategy plan in order to properly manage the transboundary waters of the Mekong River. In this context, data sharing procedures were institutionalised and have been officially implemented by the four member countries since 2001. This paper uses a systematic approach to identify the extent of data sharing and the factors influencing the willingness of key individuals in the Vietnam National Mekong Committee and its Primary Custodians to share data. We find that the initial objectives of the Procedures for Data and Information Exchange and Sharing (PDIES) have not been fully achieved and, further, that Vietnam has much to gain and little to lose by engaging in data sharing in the MRC context. The primary motivation for data sharing stems from the desire to protect national benefits and to prevent upstream countries from overexploiting the shared water resources. However, data sharing is hindered by a lack of national regulations in the Vietnam context concerning data sharing between state agencies and outdated information management systems.

  2. Late Pleistocene-Holocene seismic stratigraphy of the Southeast Vietnam Shelf

    NASA Astrophysics Data System (ADS)

    Dung, Bui Viet; Stattegger, Karl; Unverricht, Daniel; Phach, Phung Van; Thanh, Nguyen Trung

    2013-11-01

    The Late Pleistocene-Holocene sedimentary architecture of the Southeast (SE) Vietnam Shelf was investigated using high-resolution seismic profiles and core samples. Three systems tracts and a prominent seismic reflection surface at the base of the sequence were revealed. This surface (SB1) is interpreted as a sequence boundary formed by subaerial processes during the Late Pleistocene sea-level fall and subsequent marine reworking during transgression. A surface map of the lowstand surface, compiled from seismic profiles and sediment cores, revealed the W-E to N-S oriented incised-valley system of the paleo-Mekong River. The incised valleys show a clear change in morphology from the north to the south in the study area. The northern incised-valley system off Vung Tau appears as a narrow and deep V-shape in cross-section (< 5 km wide and tens of meters deep) likely as a result of the high-gradient morphology of the paleo-shelf. In contrast, the wide and low-gradient paleo-shelf off the modern Mekong Delta and Ca Mau Peninsula created shallow incised-valleys (5-15 km wide and < 15 m deep) on the exposed shelf. The lowstand systems tract (LST) consists of a prograding outer shelf delta-wedge formed during the Last Glacial Maximum (LGM) sea-level lowstand period. The transgressive systems tract (TST) was well preserved in the incised-valleys, where its thickness reaches 15-25 m. Sediment core analysis results and seismic facies reveal that the TST deposits within the incised-channels were marked by a transition from fluvial deposits at the base to marine deposits in the upper part of the channels. On the exposed shelf and the interfluvial area of the incised-channels, the TST is a sandy layer overlying the sequence boundary SB1. Thickness of the TST on the shelf varies from 0 to 15 m. The highstand systems tract (HST) consists of thick mud clinoforms of the modern Mekong subaqueous delta. The HST wedge prograded onto the shelf primarily after the mid-Holocene sea

  3. Mekong River flow and hydrological extremes under climate change

    NASA Astrophysics Data System (ADS)

    Phi Hoang, Long; Lauri, Hannu; Kummu, Matti; Koponen, Jorma; van Vliet, Michelle T. H.; Supit, Iwan; Leemans, Rik; Kabat, Pavel; Ludwig, Fulco

    2016-07-01

    Climate change poses critical threats to water-related safety and sustainability in the Mekong River basin. Hydrological impact signals from earlier Coupled Model Intercomparison Project phase 3 (CMIP3)-based assessments, however, are highly uncertain and largely ignore hydrological extremes. This paper provides one of the first hydrological impact assessments using the CMIP5 climate projections. Furthermore, we model and analyse changes in river flow regimes and hydrological extremes (i.e. high-flow and low-flow conditions). In general, the Mekong's hydrological cycle intensifies under future climate change. The scenario's ensemble mean shows increases in both seasonal and annual river discharges (annual change between +5 and +16 %, depending on location). Despite the overall increasing trend, the individual scenarios show differences in the magnitude of discharge changes and, to a lesser extent, contrasting directional changes. The scenario's ensemble, however, shows reduced uncertainties in climate projection and hydrological impacts compared to earlier CMIP3-based assessments. We further found that extremely high-flow events increase in both magnitude and frequency. Extremely low flows, on the other hand, are projected to occur less often under climate change. Higher low flows can help reducing dry season water shortage and controlling salinization in the downstream Mekong Delta. However, higher and more frequent peak discharges will exacerbate flood risks in the basin. Climate-change-induced hydrological changes will have important implications for safety, economic development, and ecosystem dynamics and thus require special attention in climate change adaptation and water management.

  4. A fluvial and pluvial probabilistic flood hazard analysis for Can Tho city, Vietnam

    NASA Astrophysics Data System (ADS)

    Apel, Heiko; Martinez, Oriol; Thi Chinh, Do; Viet Dung, Nguyen

    2014-05-01

    Can Tho city is the largest city and the economic heart of the Mekong Delta, Vietnam. Due to its economic importance and envisaged development goals the city grew rapidly in population size and extend over the last two decades. Large parts of the city are located in flood prone areas, and also the central parts of the city recently experienced an increasing number of flood events, both of fluvial and pluvial nature. As the economic power and asset values are constantly increasing, this poses a considerable risk for the city. The the aim of this study is to perform a flood hazard analysis considering both fluvial and pluvial floods and to derive probabilistic flood hazard maps. This requires in a first step an understanding of the typical flood mechanisms. Fluvial floods are triggered by a coincidence of high water levels during the annual flood period in the Mekong Delta with high tidal levels, which cause in combination short term inundations in Can Tho. Pluvial floods are triggered by typical tropical convective rain storms during the monsoon season. These two flood pathways are essentially independent in its sources and can thus be treated in the hazard analysis accordingly. For the fluvial hazard analysis we propose a bivariate frequency analysis of the Mekong flood characteristics, the annual maximum flood discharge Q and the annual flood volume V at the upper boundary of the Mekong Delta, the gauging station Kratie. This defines probabilities of exceedance of different Q-V pairs, which are transferred into synthetic flood hydrographs. The synthetic hydrographs are routed through a quasi-2D hydrodynamic model of the entire Mekong Delta in order to provide boundary conditions for a detailed hazard mapping of Can Tho. This downscaling step is necessary, because the huge complexity of the river and channel network does not allow for a proper definition of boundary conditions for Can Tho city by gauge data alone. In addition the available gauge data around Can Tho

  5. Analysis of the 2011 Mekong flood in Can Tho city

    NASA Astrophysics Data System (ADS)

    Do, Thi-Chinh; Bubeck, Philip; Nguyen, Viet-Dung; Kreibich, Heidi

    2014-05-01

    Floods in the Mekong delta occur on a recurring basis during the flood season from July to November, and regular inundations of large areas are a prerequisite for the livelihoods of about 17 million people in the Vietnamese delta. At the same time, large-scale flood events above usual water levels pose a serious hazard that repeatedly caused severe economic damage and losses of life in past decades. The flood event in 2011 in the Mekong Delta heavily impacted Can Tho City and caused substantial damage to various economic sectors. Data from face to face interviews with 480 flood-affected households and 378 small businesses were analysed to gain detailed insights into flood preparedness, early warning, emergency measures, flood impacts and recovery before, during and after the 2011 flood in Can Tho city. Amongst other things, the findings reveal that damage to households is high, often exceeding the amount of several months of income, despite a relatively high level of preparedness. In terms of small businesses, it is found that higher losses indeed occur due to the disruption of production processes compared with direct damage.

  6. Dams in the Mekong River Basin: Options for Improved Sediment and Fish Passage

    NASA Astrophysics Data System (ADS)

    Wild, T. B.; Loucks, D. P.

    2014-12-01

    The Mekong River and its tributaries comprise one of the most productive fish habitats in the world today. The economic value of the Mekong fishery in Lao PDR, Cambodia and Vietnam is among the highest in the world, providing income and food security to tens of millions of people. However, the construction of multiple dams in the basin will reduce sediment discharge, which will adversely impact nutrient transport and habitat quality and availability, and disrupt fish migration routes. Thus, of considerable interest is the identification of alternatives to the location, design and operation of planned hydropower dams that could improve sediment passage, enable migratory fish passage, and sustain fish production for local use. This paper describes the results of simulation studies designed to identify and evaluate such alternatives, as well as their potential impact on hydropower production. Dam sites in Cambodia and Lao PDR on tributaries and on the mainstream Mekong River will be discussed. Evaluations of sediment management techniques such as flushing, sluicing and bypassing will be discussed. This study is intended to inform decision makers in Cambodia, Lao PDR and Vietnam about potential alternatives to current plans as they prepare decisions regarding the development of over 100 hydropower dams throughout the basin.

  7. Mekong Basin Disease Surveillance (MBDS): a trust-based network.

    PubMed

    Phommasack, Bounlay; Jiraphongsa, Chuleeporn; Ko Oo, Moe; Bond, Katherine C; Phaholyothin, Natalie; Suphanchaimat, Rapeepong; Ungchusak, Kumnuan; Macfarlane, Sarah B

    2013-01-01

    The Mekong Basin Disease Surveillance (MBDS) network was formally established in 2001 through a Memorandum of Understanding signed by six Ministers of Health of the countries in the Greater Mekong sub-region: Cambodia, China (Yunnan and Guangxi), Lao PDR, Myanmar, Thailand and Vietnam. The main areas of focus of the network are to: i) improve cross-border infectious disease outbreak investigation and response by sharing surveillance data and best practices in disease recognition and reporting, and by jointly responding to outbreaks; ii) develop expertise in epidemiological surveillance across the countries; and iii) enhance communication between the countries. Comprised of senior health officials, epidemiologists, health practitioners, and other professionals, the MBDS has grown and matured over the years into an entity based on mutual trust that can be sustained into the future. Other regions have started emulating the network's pioneering work. In this paper, we describe the development of MBDS, the way in which it operates today, and some of its achievements. We present key challenges the network has faced and lessons its members have learned about how to develop sufficient trust for health and other professionals to alert each other to disease threats across national borders and thereby more effectively combat these threats. PMID:23362411

  8. Malaria Modeling and Surveillance for the Greater Mekong Subregion

    NASA Technical Reports Server (NTRS)

    Kiang, Richard; Adimi, Farida; Soika, Valerii; Nigro, Joseph

    2005-01-01

    At 4,200 km, the Mekong River is the tenth longest river in the world. It directly and indirectly influences the lives of hundreds of millions of inhabitants in its basin. The riparian countries - Thailand, Myanmar, Cambodia, Laos, Vietnam, and a small part of China - form the Greater Mekong Subregion (GMS). This geographical region has the misfortune of being the world's epicenter of falciparum malaria, which is the most severe form of malaria caused by Plasmodium falciparum. Depending on the country, approximately 50 to 90% of all malaria cases are due to this species. In the Malaria Modeling and Surveillance Project, we have been developing techniques to enhance public health's decision capability for malaria risk assessments and controls. The main objectives are: 1) Identifying the potential breeding sites for major vector species; 2) Implementing a malaria transmission model to identify the key factors that sustain or intensify malaria transmission; and 3) Implementing a risk algorithm to predict the occurrence of malaria and its transmission intensity. The potential benefits are: 1) Increased warning time for public health organizations to respond to malaria outbreaks; 2) Optimized utilization of pesticide and chemoprophylaxis; 3) Reduced likelihood of pesticide and drug resistance; and 4) Reduced damage to environment. Environmental parameters important to malaria transmission include temperature, relative humidity, precipitation, and vegetation conditions. These parameters are extracted from NASA Earth science data sets. Hindcastings based on these environmental parameters have shown good agreement to epidemiological records.

  9. Mekong Basin Disease Surveillance (MBDS): A Trust-Based Network

    PubMed Central

    Phommasack, Bounlay; Jiraphongsa, Chuleeporn; Ko Oo, Moe; Bond, Katherine C.; Phaholyothin, Natalie; Suphanchaimat, Rapeepong; Ungchusak, Kumnuan; Macfarlane, Sarah B.

    2013-01-01

    The Mekong Basin Disease Surveillance (MBDS) network was formally established in 2001 through a Memorandum of Understanding signed by six Ministers of Health of the countries in the Greater Mekong sub-region: Cambodia, China (Yunnan and Guangxi), Lao PDR, Myanmar, Thailand and Vietnam. The main areas of focus of the network are to: i) improve cross-border infectious disease outbreak investigation and response by sharing surveillance data and best practices in disease recognition and reporting, and by jointly responding to outbreaks; ii) develop expertise in epidemiological surveillance across the countries; and iii) enhance communication between the countries. Comprised of senior health officials, epidemiologists, health practitioners, and other professionals, the MBDS has grown and matured over the years into an entity based on mutual trust that can be sustained into the future. Other regions have started emulating the network's pioneering work. In this paper, we describe the development of MBDS, the way in which it operates today, and some of its achievements. We present key challenges the network has faced and lessons its members have learned about how to develop sufficient trust for health and other professionals to alert each other to disease threats across national borders and thereby more effectively combat these threats. PMID:23362411

  10. Detection and Characterization of Clade 1 Reassortant H5N1 Viruses Isolated from Human Cases in Vietnam during 2013

    PubMed Central

    Balish, Amanda; Hoang, Anh Nguyen; Gustin, Kortney M.; Nhung, Pham Thi; Jones, Joyce; Thu, Ngoc Nguyen; Davis, William; Ngoc, Thao Nguyen Thi; Jang, Yunho; Sleeman, Katrina; Villanueva, Julie; Kile, James; Gubareva, Larisa V.; Lindstrom, Stephen; Tumpey, Terrence M.; Davis, C. Todd; Long, Nguyen Thanh

    2015-01-01

    Highly pathogenic avian influenza (HPAI) H5N1 is endemic in Vietnamese poultry and has caused sporadic human infection in Vietnam since 2003. Human infections with HPAI H5N1 are of concern due to a high mortality rate and the potential for the emergence of pandemic viruses with sustained human-to-human transmission. Viruses isolated from humans in southern Vietnam have been classified as clade 1 with a single genome constellation (VN3) since their earliest detection in 2003. This is consistent with detection of this clade/genotype in poultry viruses endemic to the Mekong River Delta and surrounding regions. Comparison of H5N1 viruses detected in humans from southern Vietnamese provinces during 2012 and 2013 revealed the emergence of a 2013 reassortant virus with clade 1.1.2 hemagglutinin (HA) and neuraminidase (NA) surface protein genes but internal genes derived from clade 2.3.2.1a viruses (A/Hubei/1/2010-like; VN12). Closer analysis revealed mutations in multiple genes of this novel genotype (referred to as VN49) previously associated with increased virulence in animal models and other markers of adaptation to mammalian hosts. Despite the changes identified between the 2012 and 2013 genotypes analyzed, their virulence in a ferret model was similar. Antigenically, the 2013 viruses were less cross-reactive with ferret antiserum produced to the clade 1 progenitor virus, A/Vietnam/1203/2004, but reacted with antiserum produced against a new clade 1.1.2 WHO candidate vaccine virus (A/Cambodia/W0526301/2012) with comparable hemagglutination inhibition titers as the homologous antigen. Together, these results indicate changes to both surface and internal protein genes of H5N1 viruses circulating in southern Vietnam compared to 2012 and earlier viruses. PMID:26244768

  11. Detection and Characterization of Clade 1 Reassortant H5N1 Viruses Isolated from Human Cases in Vietnam during 2013.

    PubMed

    Thor, Sharmi W; Nguyen, Hieu; Balish, Amanda; Hoang, Anh Nguyen; Gustin, Kortney M; Nhung, Pham Thi; Jones, Joyce; Thu, Ngoc Nguyen; Davis, William; Ngoc, Thao Nguyen Thi; Jang, Yunho; Sleeman, Katrina; Villanueva, Julie; Kile, James; Gubareva, Larisa V; Lindstrom, Stephen; Tumpey, Terrence M; Davis, C Todd; Long, Nguyen Thanh

    2015-01-01

    Highly pathogenic avian influenza (HPAI) H5N1 is endemic in Vietnamese poultry and has caused sporadic human infection in Vietnam since 2003. Human infections with HPAI H5N1 are of concern due to a high mortality rate and the potential for the emergence of pandemic viruses with sustained human-to-human transmission. Viruses isolated from humans in southern Vietnam have been classified as clade 1 with a single genome constellation (VN3) since their earliest detection in 2003. This is consistent with detection of this clade/genotype in poultry viruses endemic to the Mekong River Delta and surrounding regions. Comparison of H5N1 viruses detected in humans from southern Vietnamese provinces during 2012 and 2013 revealed the emergence of a 2013 reassortant virus with clade 1.1.2 hemagglutinin (HA) and neuraminidase (NA) surface protein genes but internal genes derived from clade 2.3.2.1a viruses (A/Hubei/1/2010-like; VN12). Closer analysis revealed mutations in multiple genes of this novel genotype (referred to as VN49) previously associated with increased virulence in animal models and other markers of adaptation to mammalian hosts. Despite the changes identified between the 2012 and 2013 genotypes analyzed, their virulence in a ferret model was similar. Antigenically, the 2013 viruses were less cross-reactive with ferret antiserum produced to the clade 1 progenitor virus, A/Vietnam/1203/2004, but reacted with antiserum produced against a new clade 1.1.2 WHO candidate vaccine virus (A/Cambodia/W0526301/2012) with comparable hemagglutination inhibition titers as the homologous antigen. Together, these results indicate changes to both surface and internal protein genes of H5N1 viruses circulating in southern Vietnam compared to 2012 and earlier viruses. PMID:26244768

  12. Household trends in access to improved water sources and sanitation facilities in Vietnam and associated factors: findings from the Multiple Indicator Cluster Surveys, 2000–2011

    PubMed Central

    Tuyet-Hanh, Tran Thi; Lee, Jong-Koo; Oh, Juhwan; Van Minh, Hoang; Ou Lee, Chul; Hoan, Le Thi; Nam, You-Seon; Long, Tran Khanh

    2016-01-01

    Background Despite progress made by the Millennium Development Goal (MDG) number 7.C, Vietnam still faces challenges with regard to the provision of access to safe drinking water and basic sanitation. Objective This paper describes household trends in access to improved water sources and sanitation facilities separately, and analyses factors associated with access to improved water sources and sanitation facilities in combination. Design Secondary data from the Vietnam Multiple Indicator Cluster Survey in 2000, 2006, and 2011 were analyzed. Descriptive statistics and tests of significance describe trends over time in access to water and sanitation by location, demographic and socio-economic factors. Binary logistic regressions (2000, 2006, and 2011) describe associations between access to water and sanitation, and geographic, demographic, and socio-economic factors. Results There have been some outstanding developments in access to improved water sources and sanitation facilities from 2000 to 2011. In 2011, the proportion of households with access to improved water sources and sanitation facilities reached 90% and 77%, respectively, meeting the 2015 MDG targets for safe drinking water and basic sanitation set at 88% and 75%, respectively. However, despite these achievements, in 2011, only 74% of households overall had access to combined improved drinking water and sanitation facilities. There were also stark differences between regions. In 2011, only 47% of households had access to both improved water and sanitation facilities in the Mekong River Delta compared with 94% in the Red River Delta. In 2011, households in urban compared to rural areas were more than twice as likely (odds ratio [OR]: 2.2; 95% confidence interval [CI]: 1.9–2.5) to have access to improved water and sanitation facilities in combination, and households in the highest compared with the lowest wealth quintile were over 40 times more likely (OR: 42.3; 95% CI: 29.8–60.0). Conclusions More

  13. Rice-planted area extraction by time series analysis of ENVISAT ASAR WS data using a phenology-based classification approach: A case study for Red River Delta, Vietnam

    NASA Astrophysics Data System (ADS)

    Nguyen, D.; Wagner, W.; Naeimi, V.; Cao, S.

    2015-04-01

    Recent studies have shown the potential of Synthetic Aperture Radars (SAR) for mapping of rice fields and some other vegetation types. For rice field classification, conventional classification techniques have been mostly used including manual threshold-based and supervised classification approaches. The challenge of the threshold-based approach is to find acceptable thresholds to be used for each individual SAR scene. Furthermore, the influence of local incidence angle on backscatter hinders using a single threshold for the entire scene. Similarly, the supervised classification approach requires different training samples for different output classes. In case of rice crop, supervised classification using temporal data requires different training datasets to perform classification procedure which might lead to inconsistent mapping results. In this study we present an automatic method to identify rice crop areas by extracting phonological parameters after performing an empirical regression-based normalization of the backscatter to a reference incidence angle. The method is evaluated in the Red River Delta (RRD), Vietnam using the time series of ENVISAT Advanced SAR (ASAR) Wide Swath (WS) mode data. The results of rice mapping algorithm compared to the reference data indicate the Completeness (User accuracy), Correctness (Producer accuracy) and Quality (Overall accuracies) of 88.8%, 92.5 % and 83.9 % respectively. The total area of the classified rice fields corresponds to the total rice cultivation areas given by the official statistics in Vietnam (R2  0.96). The results indicates that applying a phenology-based classification approach using backscatter time series in optimal incidence angle normalization can achieve high classification accuracies. In addition, the method is not only useful for large scale early mapping of rice fields in the Red River Delta using the current and future C-band Sentinal-1A&B backscatter data but also might be applied for other rice

  14. Mekong River flow and hydrological extremes under climate change

    NASA Astrophysics Data System (ADS)

    Hoang, L. P.; Lauri, H.; Kummu, M.; Koponen, J.; van Vliet, M. T. H.; Supit, I.; Leemans, R.; Kabat, P.; Ludwig, F.

    2015-11-01

    Climate change poses critical threats to water related safety and sustainability in the Mekong River basin. Hydrological impact signals derived from CMIP3 climate change scenarios, however, are highly uncertain and largely ignore hydrological extremes. This paper provides one of the first hydrological impact assessments using the most recent CMIP5 climate change scenarios. Furthermore, we model and analyse changes in river flow regimes and hydrological extremes (i.e. high flow and low flow conditions). Similar to earlier CMIP3-based assessments, the hydrological cycle also intensifies in the CMIP5 climate change scenarios. The scenarios ensemble mean shows increases in both seasonal and annual river discharges (annual change between +5 and +16 %, depending on location). Despite the overall increasing trend, the individual scenarios show differences in the magnitude of discharge changes and, to a lesser extent, contrasting directional changes. We further found that extremely high flow events increase in both magnitude and frequency. Extremely low flows, on the other hand, are projected to occur less often under climate change. Higher low flows can help reducing dry season water shortage and controlling salinization in the downstream Mekong Delta. However, higher and more frequent peak discharges will exacerbate flood risk in the basin. The implications of climate change induced hydrological changes are critical and thus require special attention in climate change adaptation and disaster-risk reduction.

  15. Quality of Antimicrobial Products Used in Striped Catfish (Pangasianodon hypophthalmus) Aquaculture in Vietnam

    PubMed Central

    Phu, Tran Minh; Phuong, Nguyen Thanh; Scippo, Marie-Louise; Dalsgaard, Anders

    2015-01-01

    Antimicrobial usage is common in Asian aquaculture. This study aimed to determine the quality of antimicrobial products used by Vietnamese striped catfish (Pangasianodon hypophthalmus) farmers. Twenty one antimicrobial products (11 products contained a single antimicrobial and 10 products contained a mixture of two different antimicrobials) commonly used by catfish farmers were obtained from so-called chemical shops located in the Mekong Delta, Vietnam. Ultra High Performance Liquid Chromatography Mass Spectrometry was used to analyze concentration of sulfonamides, trimethoprim, amoxicillin, cefalexin and ciprofloxacin whereas concentrations of florfenicol and doxycycline were analyzed by High Performance Liquid Chromatography with UV detection. Results revealed that only 4/11 products with a single antimicrobial and 2/10 products with a mixture of antimicrobials contained active substances within ±10% of the concentration declared on the product label. Two products with antimicrobial mixtures did not contain any of the declared antimicrobials. Comparing two batches, analysis of 11 products revealed that only one product contained a concentration of active compound that varied with less than 10% in both batches. Several product labels provided inadequate information on how to calculate therapeutic dosage and further stated withdrawal time despite lack of pharmacokinetic data on the antimicrobials in catfish. There is an urgent need to strengthen approval procedures and in particular regularly to monitor the quality of antimicrobials used in Vietnamese aquaculture. PMID:25897517

  16. Quality of Antimicrobial Products Used in Striped Catfish (Pangasianodon hypophthalmus) Aquaculture in Vietnam.

    PubMed

    Phu, Tran Minh; Phuong, Nguyen Thanh; Scippo, Marie-Louise; Dalsgaard, Anders

    2015-01-01

    Antimicrobial usage is common in Asian aquaculture. This study aimed to determine the quality of antimicrobial products used by Vietnamese striped catfish (Pangasianodon hypophthalmus) farmers. Twenty one antimicrobial products (11 products contained a single antimicrobial and 10 products contained a mixture of two different antimicrobials) commonly used by catfish farmers were obtained from so-called chemical shops located in the Mekong Delta, Vietnam. Ultra High Performance Liquid Chromatography Mass Spectrometry was used to analyze concentration of sulfonamides, trimethoprim, amoxicillin, cefalexin and ciprofloxacin whereas concentrations of florfenicol and doxycycline were analyzed by High Performance Liquid Chromatography with UV detection. Results revealed that only 4/11 products with a single antimicrobial and 2/10 products with a mixture of antimicrobials contained active substances within ±10% of the concentration declared on the product label. Two products with antimicrobial mixtures did not contain any of the declared antimicrobials. Comparing two batches, analysis of 11 products revealed that only one product contained a concentration of active compound that varied with less than 10% in both batches. Several product labels provided inadequate information on how to calculate therapeutic dosage and further stated withdrawal time despite lack of pharmacokinetic data on the antimicrobials in catfish. There is an urgent need to strengthen approval procedures and in particular regularly to monitor the quality of antimicrobials used in Vietnamese aquaculture. PMID:25897517

  17. Poverty, economic growth, deprivation, and water: the cases of Cambodia and Vietnam.

    PubMed

    Varis, Olli

    2008-05-01

    Poverty reduction decorates all development agendas, but the complexity of the poverty issue is too often hidden behind simplistic indicators and development goals. Here, a closer look is taken at the concepts of "deprivation" and "vulnerability" as outcomes of poverty. Deprivation leads typically to social exclusion and marginalization; such groups are particularly weak in getting themselves out of poverty by "self-help," and economic growth does not trickle down to these people. When looking at the connections between poverty reduction and economic growth, special emphasis should be put on the differences between modern and more traditional sectors: development of the modern sector should not marginalize and exclude those dependent on more traditional livelihoods. Two case studies--The Tonle Sap area, Cambodia, and the Mekong Delta, Vietnam--reveal that investment in education, empowerment of small-scale entrepreneurship and other means of microeconomic environment, along with good governance, infrastructure, and income distribution can ensure that economic growth includes the poorer echelons of society. PMID:18595279

  18. Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap System

    NASA Astrophysics Data System (ADS)

    Cochrane, T. A.; Arias, M. E.; Piman, T.

    2014-04-01

    Kdam provides evidence of a diminished Tonle Sap flood pulse in the post-1991 period. Given the observed water level alterations from 1991 to 2010 as a result of water infrastructure development, we can extrapolate that future development in the mainstream and the key transboundary Srepok, Sesan and Sekong subbasins will have an even greater effect on the Tonle Sap flood regime, the lower Mekong floodplain, and the delta.

  19. Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap system

    NASA Astrophysics Data System (ADS)

    Cochrane, T. A.; Arias, M. E.; Piman, T.

    2014-11-01

    rates respectively at Prek Kdam provides evidence of a diminished Tonle Sap flood pulse in the post-1991 period. Given the observed water level alterations from 1991 to 2010 as a result of water infrastructure development, we can extrapolate that future development in the mainstream and the key transboundary Srepok, Sesan, and Sekong sub-basins will have an even greater effect on the Tonle Sap flood regime, the lower Mekong floodplain, and the delta.

  20. Are the fish of the upper and lower Mekong interconnected?

    NASA Astrophysics Data System (ADS)

    Kang, Bin; Perrett, Lisa; Li, Yungang; He, Daming

    2009-05-01

    The Mekong supports one of the richest inland fisheries in the world, with many of the fish migrating long distance to spawn. Little is known about the fisheries and migration strategies of the Upper Mekong whilst it is supposed that many fish species move between the Lower and Upper Mekong. Most likely, natural fish migration in the river has been altered by dam construction across the mainstream of the Upper Mekong. In this paper, the interconnectivity of fish species between different sections of the Mekong and negative impacts of dams on migratory fish are studied. Of the 162 fish species in the Upper Mekong and the 869 species in the Lower Mekong, 61 species are common. Results show that there is no significant difference at order level between the UM and LM. Similarity coefficients are used to evaluate interconnectivity at species, genus and family levels among four different sections of the Upper Mekong with each other and with the Lower Mekong as a whole. The highest similarity is found between the middle and lower reach of the Upper Mekong at species and genus levels and the middle and upper reach at family level. Of the eight cascade dams, Mengsong Dam in planning is considered as the biggest threat to migratory fish from the Lower Mekong and should be particularly concerned.

  1. The transmission of Fasciola spp. to cattle and contamination of grazing areas with Fasciola eggs in the Red River Delta region of Vietnam.

    PubMed

    Lan Anh, Nguyen Thi; Thanh, Dao Thi Ha; Hoan, Doan Huu; Thuy, Do Thu; Khong, Nguyen Viet; Anderson, Norman

    2014-04-01

    At four times during November 2010, cattle with infections of Fasciola spp., in two communes of northern Vietnam, were allocated to two equivalent groups. Cattle in one group were treated with triclabendazole. Faecal samples collected monthly from both groups were tested for Fasciola copro-antigens and the presence of Fasciola eggs. Re-infection of treated cattle occurred from early March to late November, coinciding with high weekly totals of rainfall. Contamination of grazing areas by untreated cattle was high and relatively constant throughout the year. However, contamination was reduced to undetectable amounts for 8 to 12 weeks after treatment and even at 20 weeks was only 50% or less of the pre-treatment amounts. Therefore, treatments given in mid-September and again in early April, at the start of the wet season, may be sufficient to prevent contamination of grazing areas and reduce the prevalence and severity of Fasciola infections in cattle. PMID:24510222

  2. Measuring Bedload Sediment Flux in Large Rivers: New Data from the Mekong River and Its Applications in Assessing Geomorphic Change

    NASA Astrophysics Data System (ADS)

    Best, J.; Hackney, C. R.; Parsons, D. R.; Darby, S. E.; Leyland, J.; Aalto, R. E.; Nicholas, A. P.

    2014-12-01

    Many large rivers are undergoing renewed and increasing anthropogenic-induced change as water diversions, new dams and greater water demands place enhanced stresses on these river basins. Examples of rivers undergoing significant change include the Amazon, Madeira, Nile, Yangtze and Mekong, with considerable ongoing debate raging as to the long-term geomorphic and ecological effects of major anthropogenic interventions. Assessing the effects of such change in large rivers is demanding, one reason being that sediment transport is often exceedingly difficult to measure, and thus data needed to inform the debate on the impact of anthropogenic change is frequently lacking. Here, we report on one aspect of research being undertaken as part of STELAR-S2S - Sediment Transfer and Erosion on Large Alluvial Rivers - that is seeking to better understand the relationship between climate, anthropogenic impacts and sediment transport in some of the world's largest rivers. We are using the Lower Mekong River as our study site, with the Mekong delta being one of only three in the world classified by the IPCC as 'extremely vulnerable' to future changes in climate. Herein, we describe details of bedload sediment flux estimation using repeated high-resolution multibeam echo sounder (MBES) bathymetric mapping along the Lower Mekong and Tonle Sap rivers in Cambodia. We are using MBES to quantify the spatial variation in sediment transport both along and also across the river at 11 sites in the study area. Predicted increases in the extraction of sediment from the river through sand dredging are thought likely to cause a significant decrease in downstream sediment flux, and future dam construction along the Mekong main channel potentially offers another source of significant change. These field results will be set in the light of these anthropogenic drivers on sediment flux in the Mekong River and their possible future effects on bar formation and channel migration.

  3. Long-term trend of climate variables in the upper Dong Nai river basin in Vietnam

    NASA Astrophysics Data System (ADS)

    Truong, Nguyen Cung Que; Nguyen, Hong Quan; Kondoh, Akihiko

    2015-04-01

    Dong Nai river and Mekong delta downstream are located in and supplied the major water resources to the whole Southern of Vietnam. In the state of continuous changes in water resources due to climate changes, there are several controversy about the potential impact of sediment transport and river flows downstream due to either the cascade hydroelectric power plant system or dam construction in the upper of Mekong delta. Therefore, management and planning for efficient use of Dong Nai river water resource is very important. Furthermore, that it is necessary to consider the hydrological regime change by the effects of climate variable. On the other hand, solving the problems of water shortage in the dry season and flood control in rainy season are also important for issues of water management at Dong Nai river basin. In this study we evaluated changes in two main factors of the water balance equation (both rainfall and evapotranspiration) to assess long-term change in the hydrological regime in the upper area of Dong Nai river basin. This key theme was divided into the following two sub-goals. The first goal was to analyze long term spatial and temporal rainfall trends. The second goal was to analyze the long-term trend of meteorological factors determining evapotranspiration such as air temperature, wind speed, solar radiation and sunshine duration. The results were used to assess their impact to evapotranspiration. The meteorological and hydrological data of the basin for the last 20 years (from 1993 to 2012) were analyzed based on the Empirical Mode Decomposition (EMD) method. The EMD method has been pioneered by Huang et al. (1998) for adaptively representing nonstationary time-series data as sum of zero-mean amplitude modulation-frequency modulation (AM-FM) components by iteratively conducting the sifting process. These components called Intrinsic Mode Functions (IMFs) allow the calculation of a meaningful multi-component instantaneous frequency. The results

  4. Managing Mekong Mud and its Impact on Fish, Hydropower and People

    NASA Astrophysics Data System (ADS)

    Wild, T. B.; Loucks, D. P.

    2013-12-01

    The Lancang/Mekong River flows from the Tibetan Plateau through the Upper Mekong Basin in China (where it is called the Lancang Jiang) to the Lower Mekong Basin (LMB) in Myanmar, Laos, Thailand, Cambodia, and Vietnam, before discharging into the South China Sea. The river has remained largely unaltered for much of its history, but today hydropower reservoirs are being designed and developed at a rapid pace. Some 60 million people living in the basin have depended on the basin's ecosystems to produce much of their food and income. The health and productivity of the ecosystems are dependent upon the river's natural flow and sediment regimes, both of which could be significantly altered by the rapid construction of dams. This presentation focuses on the potential impacts of dam development and alternative sediment management options, where feasible, including flushing, sluicing, bypassing, and density current venting. We evaluate whether these techniques can improve reservoir sediment outflows without damaging the environmental system we are attempting to preserve. We also evaluate the accompanying losses in hydropower production necessary to achieve the improved sediment passage. This study focuses on dams in China, Cambodia, Laos and Vietnam, both on the mainstream Mekong River and on its tributaries. A sediment simulation model was developed specifically to conduct these evaluations. This model implements a daily time-step mass-balance simulation of flow and sediment to predict the spatial and temporal accumulation, depletion, and distribution of sediment in river reaches and in reservoirs under different flow and sediment management policies. Results of simulations suggest that more benign (with regard to sediment) alternatives to the currently proposed locations and designs of dams exist and should be considered. While sediment management alternatives have the potential to increase sediment loads discharged downstream, careful attention must be paid to the

  5. Induction of Antimicrobial Resistance in Escherichia coli and Non-Typhoidal Salmonella Strains after Adaptation to Disinfectant Commonly Used on Farms in Vietnam.

    PubMed

    Nhung, Nguyen T; Thuy, Cao T; Trung, Nguyen V; Campbell, James; Baker, Stephen; Thwaites, Guy; Hoa, Ngo T; Carrique-Mas, Juan

    2015-01-01

    In Vietnam, commercial disinfectants containing quaternary ammonium compounds (QACs) are commonly used in pig and poultry farms to maintain hygiene during production. We hypothesized that sustained exposure to sub-bactericidal concentrations of QAC-based disinfectants may result in increased levels of antimicrobial resistance (AMR) among Enterobacteriacea due to the increase of efflux pump expression. To test this hypothesis we exposed six antimicrobial-susceptible Escherichia coli (E. coli) and six antimicrobial-susceptible non-typhoidal Salmonella (NTS) isolates to increasing concentrations of a commonly used commercial disinfectant containing a mix of benzalkonium chloride and glutaraldehyde. Over the 12-day experiment, strains exhibited a significant change in their minimum inhibitory concentration (MIC) of the disinfectant product (mean increase of 31% (SD ± 40)) (p = 0.02, paired Wilcoxon test). Increases in MIC for the disinfectant product were strongly correlated with increases in MIC (or decreases in inhibition zone) for all antimicrobials (Pearson's correlation coefficient 0.71-0.83, all p < 0.01). The greatest increases in MIC (or decreases in inhibition zone) were observed for ampicillin, tetracycline, ciprofloxacin, and chloramphenicol, and the smallest for gentamicin, trimethoprim/sulphamethoxazole. The treatment of 155 representative E. coli isolates from farmed and wild animals in the Mekong Delta (Vietnam) with phenyl-arginine beta-naphthylamide (PAβN), a generic efflux pump inhibitor, resulted in reductions in the prevalence of AMR ranging from 0.7% to 3.3% in these organisms, indicating a small contribution of efflux pumps on the observed prevalence of AMR on farms. These results suggest that the mass usage of commercial disinfectants, many of which contain QACs, is potentially a contributing factor on the generation and maintenance of AMR in animal production in Vietnam. PMID:27025637

  6. Induction of Antimicrobial Resistance in Escherichia coli and Non-Typhoidal Salmonella Strains after Adaptation to Disinfectant Commonly Used on Farms in Vietnam

    PubMed Central

    Nhung, Nguyen T.; Thuy, Cao T.; Trung, Nguyen V.; Campbell, James; Baker, Stephen; Thwaites, Guy; Hoa, Ngo T.; Carrique-Mas, Juan

    2015-01-01

    In Vietnam, commercial disinfectants containing quaternary ammonium compounds (QACs) are commonly used in pig and poultry farms to maintain hygiene during production. We hypothesized that sustained exposure to sub-bactericidal concentrations of QAC-based disinfectants may result in increased levels of antimicrobial resistance (AMR) among Enterobacteriacea due to the increase of efflux pump expression. To test this hypothesis we exposed six antimicrobial-susceptible Escherichia coli (E. coli) and six antimicrobial-susceptible non-typhoidal Salmonella (NTS) isolates to increasing concentrations of a commonly used commercial disinfectant containing a mix of benzalkonium chloride and glutaraldehyde. Over the 12-day experiment, strains exhibited a significant change in their minimum inhibitory concentration (MIC) of the disinfectant product (mean increase of 31% (SD ± 40)) (p = 0.02, paired Wilcoxon test). Increases in MIC for the disinfectant product were strongly correlated with increases in MIC (or decreases in inhibition zone) for all antimicrobials (Pearson’s correlation coefficient 0.71–0.83, all p < 0.01). The greatest increases in MIC (or decreases in inhibition zone) were observed for ampicillin, tetracycline, ciprofloxacin, and chloramphenicol, and the smallest for gentamicin, trimethoprim/sulphamethoxazole. The treatment of 155 representative E. coli isolates from farmed and wild animals in the Mekong Delta (Vietnam) with phenyl-arginine beta-naphthylamide (PAβN), a generic efflux pump inhibitor, resulted in reductions in the prevalence of AMR ranging from 0.7% to 3.3% in these organisms, indicating a small contribution of efflux pumps on the observed prevalence of AMR on farms. These results suggest that the mass usage of commercial disinfectants, many of which contain QACs, is potentially a contributing factor on the generation and maintenance of AMR in animal production in Vietnam. PMID:27025637

  7. Assessment of plastic waste generation and its potential recycling of household solid waste in Can Tho City, Vietnam.

    PubMed

    Thanh, Nguyen Phuc; Matsui, Yasuhiro; Fujiwara, Takeshi

    2011-04-01

    Plastic solid waste has become a serious problem when considering the disposal alternatives following the sequential hierarchy of sound solid waste management. This study was undertaken to assess the quantity and composition of household solid waste, especially plastic waste to identify opportunities for waste recycling. A 1-month survey of 130 households was carried out in Can Tho City, the capital city of the Mekong Delta region in southern Vietnam. Household solid waste was collected from each household and classified into ten physical categories; especially plastic waste was sorted into 22 subcategories. The average household solid waste generation rate was 281.27 g/cap/day. The compostable and recyclable shares respectively accounted for high percentage as 80.74% and 11%. Regarding plastic waste, the average plastic waste generation rate was 17.24 g/cap/day; plastic packaging and plastic containers dominated with the high percentage, 95.64% of plastic waste. Plastic shopping bags were especially identified as the major component, accounting for 45.72% of total plastic waste. Relevant factors such as household income and household size were found to have an existing correlation to plastic waste generation in detailed composition. The household habits and behaviors of plastic waste discharge and the aspects of environmental impacts and resource consumption for plastic waste disposal alternatives were also evaluated. PMID:20490914

  8. The Mekong Fish Network: expanding the capacity of the people and institutions of the Mekong River Basin to share information and conduct standardized fisheries monitoring

    USGS Publications Warehouse

    Patricio, Harmony C.; Ainsley, Shaara M.; Andersen, Matthew E.; Beeman, John W.; Hewitt, David A.

    2012-01-01

    The Mekong River is one of the most biologically diverse rivers in the world, and it supports the most productive freshwater fisheries in the world. Millions of people in the Lower Mekong River Basin (LMB) countries of the Union of Myanmar (Burma), Lao People’s Democratic Republic, the Kingdom of Thailand, the Kingdom of Cambodia, and the Socialist Republic of Vietnam rely on the fisheries of the basin to provide a source of protein. The Mekong Fish Network Workshop was convened in Phnom Penh, Cambodia, in February 2012 to discuss the potential for coordinating fisheries monitoring among nations and the utility of establishing standard methods for short- and long-term monitoring and data sharing throughout the LMB. The concept for this network developed out of a frequently cited need for fisheries researchers in the LMB to share their knowledge with other scientists and decisionmakers. A fish monitoring network could be a valuable forum for researchers to exchange ideas, store data, or access general information regarding fisheries studies in the LMB region. At the workshop, representatives from governments, nongovernmental organizations, and universities, as well as participating foreign technical experts, cited a great need for more international cooperation and technical support among them. Given the limited staff and resources of many institutions in the LMB, the success of the proposed network would depend on whether it could offer tools that would provide benefits to network participants. A potential tool discussed at the workshop was a user-friendly, Web-accessible portal and database that could help streamline data entry and storage at the institutional level, as well as facilitate communication and data sharing among institutions. The workshop provided a consensus to establish pilot standardized data collection and database efforts that will be further reviewed by the workshop participants. Overall, workshop participants agreed that this is the type of

  9. Malaria in the Greater Mekong Subregion: Heterogeneity and Complexity

    PubMed Central

    Cui, Liwang; Yan, Guiyun; Sattabongkot, Jetsumon; Cao, Yaming; Chen, Bin; Chen, Xiaoguang; Fan, Qi; Fang, Qiang; Jongwutiwes, Somchai; Parker, Daniel; Sirichaisinthop, Jeeraphat; Kyaw, Myat Phone; Su, Xin-zhuan; Yang, Henglin; Yang, Zhaoqing; Wang, Baomin; Xu, Jianwei; Zheng, Bin; Zhong, Daibin; Zhou, Guofa

    2011-01-01

    The Greater Mekong Subregion (GMS), comprised of six countries including Cambodia, China's Yunnan Province, Lao PDR, Myanmar (Burma), Thailand and Vietnam, is one of the most threatening foci of malaria. Since the initiation of the WHO's Mekong Malaria Program a decade ago, malaria situation in the GMS has greatly improved, reflected in the continuous decline in annual malaria incidence and deaths. However, as many nations are moving towards malaria elimination, the GMS nations still face great challenges. Malaria epidemiology in this region exhibits enormous geographical heterogeneity with Myanmar and Cambodia remaining high-burden countries. Within each country, malaria distribution is also patchy, exemplified by ‘border malaria’ and ‘forest malaria’ with high transmission occurring along international borders and in forests or forest fringes, respectively. ‘Border malaria’ is extremely difficult to monitor, and frequent malaria introductions by migratory human populations constitute a major threat to neighboring, malaria-eliminating countries. Therefore, coordination between neighboring countries is essential for malaria elimination from the entire region. In addition to these operational difficulties, malaria control in the GMS also encounters several technological challenges. Contemporary malaria control measures rely heavily on effective chemotherapy and insecticide control of vector mosquitoes. However, the spread of multidrug resistance and potential emergence of artemisinin resistance in Plasmodium falciparum make resistance management a high priority in the GMS. This situation is further worsened by the circulation of counterfeit and substandard artemisinin-related drugs. In most endemic areas of the GMS, P. falciparum and P. vivax coexist, and in recent malaria control history, P. vivax has demonstrated remarkable resilience to control measures. Deployment of the only registered drug (primaquine) for the radical cure of vivax malaria is

  10. Estimating the Burden of Japanese Encephalitis Virus and Other Encephalitides in Countries of the Mekong Region

    PubMed Central

    Tarantola, Arnaud; Goutard, Flavie; Newton, Paul; de Lamballerie, Xavier; Lortholary, Olivier; Cappelle, Julien; Buchy, Philippe

    2014-01-01

    Diverse aetiologies of viral and bacterial encephalitis are widely recognized as significant yet neglected public health issues in the Mekong region. A robust analysis of the corresponding health burden is lacking. We retrieved 75 articles on encephalitis in the region published in English or in French from 1965 through 2011. Review of available data demonstrated that they are sparse and often derived from hospital-based studies with significant recruitment bias. Almost half (35 of 75) of articles were on Japanese encephalitis virus (JEV) alone or associated with dengue. In the Western Pacific region the WHO reported 30,000–50,000 annual JEV cases (15,000 deaths) between 1966 and 1996 and 4,633 cases (200 deaths) in 2008, a decline likely related to the introduction of JEV vaccination in China, Vietnam, or Thailand since the 1980s. Data on dengue, scrub typhus and rabies encephalitis, among other aetiologies, are also reviewed and discussed. Countries of the Mekong region are undergoing profound demographic, economic and ecological change. As the epidemiological aspects of Japanese encephalitis (JE) are transformed by vaccination in some countries, highly integrated expert collaborative research and objective data are needed to identify and prioritize the human health, animal health and economic burden due to JE and other pathogens associated with encephalitides. PMID:24498443

  11. Urbanization and climate change impacts on future urban flooding in Can Tho city, Vietnam

    NASA Astrophysics Data System (ADS)

    Huong, H. T. L.; Pathirana, A.

    2013-01-01

    Urban development increases flood risk in cities due to local changes in hydrological and hydrometeorological conditions that increase flood hazard, as well as to urban concentrations that increase the vulnerability. The relationship between the increasing urban runoff and flooding due to increased imperviousness is better perceived than that between the cyclic impact of urban growth and the urban rainfall via microclimatic changes. The large-scale, global impacts due to climate variability and change could compound these risks. We present the case of a typical third world city - Can Tho (the biggest city in Mekong River Delta, Vietnam) - faced with multiple future challenges, namely: (i) the likely effect of climate change-driven sea level rise, (ii) an expected increase of river runoff due to climate change as estimated by the Vietnamese government, (iii) increased urban runoff driven by imperviousness, and (iv) enhancement of extreme rainfall due to urban growth-driven, microclimatic change (urban heat islands). A set of model simulations were used to construct future scenarios, combining these influences. Urban growth of the city was projected up to year 2100 based on historical growth patterns, using a land use simulation model (Dinamica EGO). A dynamic limited-area atmospheric model (WRF), coupled with a detailed land surface model with vegetation parameterization (Noah LSM), was employed in controlled numerical experiments to estimate the anticipated changes in extreme rainfall patterns due to urban heat island effect. Finally, a 1-D/2-D coupled urban-drainage/flooding model (SWMM-Brezo) was used to simulate storm-sewer surcharge and surface inundation to establish the increase in the flood hazard resulting from the changes. The results show that under the combined scenario of significant change in river level (due to climate-driven sea level rise and increase of flow in the Mekong) and "business as usual" urbanization, the flooding of Can Tho could increase

  12. Building Exposure Maps Of Urban Infrastructure And Crop Fields In The Mekong River Basin

    NASA Astrophysics Data System (ADS)

    Haas, E.; Weichselbaum, J.; Gangkofner, U.; Miltzer, J.; Wali, A.

    2013-12-01

    In the frame of the Integrated Water Resources Management (IWRM) initiative for the Mekong river basin World Bank is collaborating with the Mekong River Commission and governmental organizations in Cambodia, Lao PDR, Thailand and Vietnam to build national and regional capacities for managing the risks associated with natural disasters, such as floods, flash floods and droughts. Within ‘eoworld', a joint initiative set up by ESA and World Bank to foster the use of Earth Observation (EO) for sustainable development work, a comprehensive database of elements at risk in the Lower Mekong river basin has been established by GeoVille, including urban infrastructure and crops (primarily rice paddies). In the long term, this exposure information shall be fed into an open-source multi- hazard modeling tool for risk assessment along the Mekong River, which then shall be used by national stakeholders as well as insurance and financial institutions for planning, disaster preparedness and emergency management. Earth Observation techniques can provide objective, synoptic and repetitive observations of elements at risk including buildings, infrastructure and crops. Through the fusion of satellite-based with in-situ data from field surveys and local knowledge (e.g. on building materials) features at risk can be characterised and mapped with high accuracy. Earth Observation data utilised comprise bi-weekly Envisat ASAR imagery programmed for a period of 9 months in 2011 to map the development of the rice cultivation area, identify predominant cropping systems (wet-season vs. dry season cultivation), crop cycles (single /double / triple crop per year), date of emergence/harvest and the distinction between rice planted under intensive (SRI) vs. regular rice cultivation techniques. Very High Resolution (VHR) optical data from SPOT, KOMPSAT and QuickBird were used for mapping of buildings and infrastructure, such as building footprints, residential / commercial areas, industrial

  13. Bayesian modeling approach for characterizing groundwater arsenic contamination in the Mekong River basin.

    PubMed

    Cha, YoonKyung; Kim, Young Mo; Choi, Jae-Woo; Sthiannopkao, Suthipong; Cho, Kyung Hwa

    2016-01-01

    In the Mekong River basin, groundwater from tube-wells is a major drinking water source. However, arsenic (As) contamination in groundwater resources has become a critical issue in the watershed. In this study, As species such as total As (AsTOT), As(III), and As(V), were monitored across the watershed to investigate their characteristics and inter-relationships with water quality parameters, including pH and redox potential (Eh). The data illustrated a dramatic change in the relationship between AsTOT and Eh over a specific Eh range, suggesting the importance of Eh in predicting AsTOT. Thus, a Bayesian change-point model was developed to predict AsTOT concentrations based on Eh and pH, to determine changes in the AsTOT-Eh relationship. The model captured the Eh change-point (∼-100±15mV), which was compatible with the data. Importantly, the inclusion of this change-point in the model resulted in improved model fit and prediction accuracy; AsTOT concentrations were strongly negatively related to Eh values higher than the change-point. The process underlying this relationship was subsequently posited to be the reductive dissolution of mineral oxides and As release. Overall, AsTOT showed a weak positive relationship with Eh at a lower range, similar to those commonly observed in the Mekong River basin delta. It is expected that these results would serve as a guide for establishing public health strategies in the Mekong River Basin. PMID:25796421

  14. Vietnam: Historians at War

    ERIC Educational Resources Information Center

    Moyar, Mark

    2008-01-01

    Although the Vietnam War ended more than thirty years ago, historians remain as divided on what happened as the American people were during the war. Mark Moyar maps the ongoing battle between "orthodox" and "revisionist" Vietnam War historians: the first group, those who depict Vietnam as a bad war that the United States should not have fought,…

  15. Land cover, land use, and climate change impacts on agriculture in southern Vietnam

    NASA Astrophysics Data System (ADS)

    Kontgis, Caitlin

    Global environmental change is rapidly changing the surface of the Earth in varied and irrevocable ways. Across the world, land cover and land use have been altered to accommodate the needs of expanding populations, and climate change has required plant, animal, and human communities to adapt to novel climates. These changes have created unprecedented new ecosystems that affect the planet in ways that are not fully understood and difficult to predict. Of utmost concern is food security, and whether agro-ecosystems will adapt and respond to widespread changes so that growing global populations can be sustained. To understand how one staple food crop, rice, responds to global environmental change in southern Vietnam, this dissertation aims to accomplish three main tasks: (1) quantify the rate and form of urban and peri-urban expansion onto cropland using satellite imagery and demographic data, (2) track changes to annual rice paddy harvests using time series satellite data, and (3) model the potential effects of climate change on rice paddies by incorporating farmer interview data into a crop systems model. The results of these analyses show that the footprint of Ho Chi Minh City grew nearly five times between 1990 and 2012. Mismatches between urban development and population growth suggest that peri-urbanization is driven by supply-side investment, and that much of this form of land expansion has occurred near major transit routes. In the nearby Mekong River Delta, triple-cropped rice paddy area doubled between 2000 and 2010, from one-third to two-thirds of rice fields, while paddy area expanded by about 10%. These results illustrate the intensification of farming practices since Vietnam liberalized its economy, yet it is not clear whether such practices are environmentally sustainable long-term. Although triple-cropped paddy fields have expanded, future overall production is estimated to decline without the effects of CO2 fertilization. Temperatures are anticipated

  16. Assessing Malaria Risks in Greater Mekong Subregion based on Environmental Parameters

    NASA Technical Reports Server (NTRS)

    Kiang, Richard; Soika, Valerii; Adimi, Farida; Nigro, Joseph

    2005-01-01

    At 4,200 km, the Mekong River is the tenth longest river in the world. It directly and indirectly influences the lives of hundreds of millions of inhabitants in its basin. The riparian countries - Thailand, Myanmar, Cambodia, Laos, Vietnam, and a small part of China - form the Greater Mekong Subregion (GMS). This geographical region has the misfortune of being the world's epicenter of falciparum malaria, which is the most severe form of malaria caused by Plasmodium falciparum. Depending on the country, approximately 50 to 90% of all malaria cases are due to this species. In the Malaria Modeling and Surveillance Project, we have been developing techniques to enhance public health s decision capability for malaria risk assessments and controls. The main objectives are: 1) identifying the potential breeding sites for major vector species; 2) implementing a malaria transmission model to identify the key factors that sustain or intensify malaria transmission; and 3) implementing a risk algorithm to predict the occurrence of malaria and its transmission intensity. The potential benefits are: 1) increased warning time for public health organizations to respond to malaria outbreaks; 2) optimized utilization of pesticide and chemoprophylaxis; 3) reduced likelihood of pesticide and drug resistance; and 4) reduced damage to environment. Environmental parameters important to malaria transmission include temperature, relative humidity, precipitation, and vegetation conditions. The NASA Earth science data sets that have been used for malaria surveillance and risk assessment include AVHRR Pathfinder, TRMM, MODIS, NSIPP, and SIESIP. Hindcastings based on these environmental parameters have shown good agreement to epidemiological records. Socioeconomic factors that may influence malaria transmissions will also be incorporated into the predictive models.

  17. Sediment dynamics in the lower Mekong River: Transition from tidal river to estuary

    NASA Astrophysics Data System (ADS)

    Nowacki, Daniel J.; Ogston, Andrea S.; Nittrouer, Charles A.; Fricke, Aaron T.; Van, Pham Dang Tri

    2015-09-01

    A better understanding of flow and sediment dynamics in the lowermost portions of large-tropical rivers is essential to constraining estimates of worldwide sediment delivery to the ocean. Flow velocity, salinity, and suspended-sediment concentration were measured for 25 h at three cross sections in the tidal Song Hau distributary of the Mekong River, Vietnam. Two campaigns took place during comparatively high-seasonal and low-seasonal discharge, and estuarine conditions varied dramatically between them. The system transitioned from a tidal river with ephemeral presence of a salt wedge during high flow to a partially mixed estuary during low flow. The changing freshwater input, sediment sources, and estuarine characteristics resulted in seaward sediment export during high flow and landward import during low flow. The Dinh An channel of the Song Hau distributary exported sediment to the coast at a rate of about 1 t s-1 during high flow and imported sediment in a spatially varying manner at approximately 0.3 t s-1 during low flow. Scaling these values results in a yearly Mekong sediment discharge estimate about 65% smaller than a generally accepted estimate of 110 Mt yr-1, although the limited temporal and spatial nature of this study implies a relatively high degree of uncertainty for the new estimate. Fluvial advection of sediment was primarily responsible for the high-flow sediment export. Exchange-flow and tidal processes, including local resuspension, were principally responsible for the low-flow import. The resulting bed-sediment grain size was coarser and more variable during high flow and finer during low, and the residual flow patterns support the maintenance of mid-channel islands. This article was corrected on 7 OCT 2015. See the end of the full text for details.

  18. Spatio-temporal patterns of soil erosion and suspended sediment dynamics in the Mekong River Basin.

    PubMed

    Suif, Zuliziana; Fleifle, Amr; Yoshimura, Chihiro; Saavedra, Oliver

    2016-10-15

    Understanding of the distribution patterns of sediment erosion, concentration and transport in river basins is critically important as sediment plays a major role in river basin hydrophysical and ecological processes. In this study, we proposed an integrated framework for the assessment of sediment dynamics, including soil erosion (SE), suspended sediment load (SSL) and suspended sediment concentration (SSC), and applied this framework to the Mekong River Basin. The Revised Universal Soil Loss Equation (RUSLE) model was adopted with a geographic information system to assess SE and was coupled with a sediment accumulation and a routing scheme to simulate SSL. This framework also analyzed Landsat imagery captured between 1987 and 2000 together with ground observations to interpolate spatio-temporal patterns of SSC. The simulated SSL results from 1987 to 2000 showed the relative root mean square error of 41% and coefficient of determination (R(2)) of 0.89. The polynomial relationship of the near infrared exoatmospheric reflectance and the band 4 wavelength (760-900nm) to the observed SSC at 9 sites demonstrated the good agreement (overall relative RMSE=5.2%, R(2)=0.87). The result found that the severe SE occurs in the upper (China and Lao PDR) and lower (western part of Vietnam) regions. The SSC in the rainy season (June-November) showed increasing and decreasing trends longitudinally in the upper (China and Lao PDR) and lower regions (Cambodia), respectively, while the longitudinal profile of SSL showed a fluctuating trend along the river in the early rainy season. Overall, the results described the unique spatio-temporal patterns of SE, SSL and SSC in the Mekong River Basin. Thus, the proposed integrated framework is useful for elucidating complex process of sediment generation and transport in the land and river systems of large river basins. PMID:27338846

  19. Copper toxicity and the influence of water quality of Dongnai River and Mekong River waters on copper bioavailability and toxicity to three tropical species.

    PubMed

    Bui, Thanh-Khiet L; Do-Hong, L Chi; Dao, Thanh-Son; Hoang, Tham C

    2016-02-01

    The present study investigated copper (Cu) toxicity and the influence of water quality characteristics of Dongnai River and Mekong River (Vietnam) surface waters to three tropical species; Daphnia lumholtzi, Ceriodaphnia cornuta, and Danio rerio. The river waters had a range of water quality parameters that modify Cu bioavailability and toxicity. The range of total hardness, alkalinity, pH and dissolved organic carbon were 15-64 mg/L as CaCO3, 18-58 mg/L as CaCO3, 6.62-7.88, and 6.9-14.7 mg/l, respectively. The US EPA acute toxicity test method with a modification to the light photoperiod and temperature for tropical organisms was used to investigate Cu toxicity. Result of the present study found that Cu produced toxic effect to the studied organisms at low concentrations. The 48-h LC50 ranged from 3.92 to 8.61 µg/l, 2.92-9.56 µg/l, and 15.71-68.69 µg/l dissolved Cu for D. lumholtzi, C. cornuta, and D. rerio, respectively. In general, water quality had an influence on Cu bioavailability and toxicity to the studied organisms. The toxicity of Cu was higher in water with lower hardness, DOC, and/or pH. The present study indicates a contribution of Cu hydroxide and carbonate to Cu bioavailability to Mekong organisms. Results of the present study will be used for calibrating the US Cu Biotic Ligand Model (BLM) to Mekong River water and organisms in support of application of the BLM for setting site-specific Cu water quality guidelines in the ecosystem of the Lower Mekong River Basin. PMID:26421627

  20. Vietnam plunges ahead

    SciTech Connect

    Burr, M.T.

    1995-07-01

    Vietnam is moving fast. Facing the need to double its installed power generation capacity by the year 2000, Vietnam is pursuing a range of development alternatives to add an estimated 3,000 MW of new power plants. As part of the country`s progress toward a market economy, Vietnam has relaxed its rules regarding investment in power plants. The country enacted a new electricity law early in 1995, paving the way for private participation in the power sector.

  1. DELTAS: A new Global Delta Sustainability Initiative (Invited)

    NASA Astrophysics Data System (ADS)

    Foufoula-Georgiou, E.

    2013-12-01

    , Vietnam, and Canada. Key components of the DELTAS Sustainability Initiative are: integrated research on deltas as coupled socio-ecological systems undergoing change (Delta-SRES), a global delta data depository (Delta-DAT), a suite of open access delta risk assessment and decision support modeling tools (Delta-RADS), and the coordinated demonstration of these activities in deltas around the world (Delta-ACT).

  2. In Vietnam, Manufacturing Masterworks

    ERIC Educational Resources Information Center

    Overland, Martha Ann

    2006-01-01

    Vietnam, with its cheap labor and lax copyright laws, is a counterfeiter's dream. Books are sold hot off the photocopier and Hollywood's latest blockbusters can be had on DVD's for about a dollar. But it is in art forgery that Vietnam excels. With a stable of neoclassically trained art students, who spend years learning to copy the masters, art…

  3. Emergency medicine in Vietnam.

    PubMed

    Richards, J R

    1997-04-01

    The Socialist Republic of Vietnam is one of the poorest countries in the world. Recent economic developments, as the country attempts to start a market economy, have had a profound impact on its health care system. This report describes the state of prehospital and emergency medical care in Vietnam and possibilities for the future. PMID:9095019

  4. [Increase of entomological indices during the pre-epidemic period of dengue in Ben Tre, South Vietnam].

    PubMed

    Nguyen, T P Q; Luu, L L; Vu, T Q H; Buisson, Y

    2011-10-01

    Dengue has emerged in Vietnam 50 years ago and since has become endemo-epidemic throughout the whole country. Each year, major epidemics of dengue fever (DF) and dengue hemorrhagic fever (DHF) hit South Vietnam during the rainy season, causing significant morbidity and mortality, especially among young children. The only preventive measure is vector control, but it is often implemented too late or indiscriminately. The aim of this study was to investigate, in the pre-epidemic stage, the existence of significant changes in vector indices, which will predict DF/DHF outbreaks. We conducted a descriptive transversal study, repeated once a month for four months (March to June) in the village of Locthuan (province Ben Tre) in the Mekong's delta. Adult mosquitoes were caught in 30 houses, and larvae were collected in water holding containers of 50 houses. The houses were randomly selected. Vector densities were calculated according to the indices recommended by WHO. Virological analysis was carried out on lots of female Aedes and larvae in order to determine viral infection rates. Catches of adult mosquitoes collected 496 specimens including 329 Aedes, 139 Culex and 28 Anopheles. Aedes aegypti was present in 63% of visited homes that is an average density of 1.8 mosquitoes per house. The increase in imaginal indices during the 4 months was not significant. The survey of breeding sites of Ae. aegypti identified 1292 water containers in which 71,569 larval specimens were collected. The values of house index, container index [CI] and Breteau index [BI] increased each month, the latter from 166 to 442. This increase was significant for CI and BI. Breeding sites were mostly intra-home, mainly consisting of large and small ceramic jars. Larval density of Ae. aegypti in the containers also increased significantly over the 4 months. It was correlated with the lack of cover and predators such as Mesocyclops spp., Micronecta spp. and larvivorous fishes. Cultivation of 15 pools of

  5. Malaria situation in the Greater Mekong Subregion.

    PubMed

    Hewitt, Sean; Delacollette, Charles; Chavez, Irwin

    2013-01-01

    The epidemiology of malaria in the Greater Mekong Subregion is complex and rapidly evolving. Malaria control and elimination efforts face a daunting array of challenges including multidrug-resistant parasites. This review presents secondary data collected by the national malaria control programs in the six countries between 1998 and 2010 and examines trends over the last decade. This data has a number of limitations: it is derived exclusively from public sector health facilities; falciparum-specific and then pan-specific rapid diagnostic tests were introduced during the period under review; and, recently there has been a massive increase in case detection capability as a result of increased funding. It therefore requires cautious interpretation. A series of maps are presented showing trends in incidence, mortality and proportion of cases caused by Plasmodium falciparum over the last decade. A brief overview of institutional and implementation arrangements, historical background, demographics and key issues affecting malaria epidemiology is provided for each country. National malaria statistics for 2010 are presented and their robustness discussed in terms of the public sector's share of cases and other influencing factors such as inter-country variations in risk stratification, changes in diagnostic approach and immigration. Targets are presented for malaria control and where appropriate for elimination. Each country's artemisinin resistance status is described. The epidemiological trends presented reflect the improvement in the malaria situation, however the true malaria burden is as yet unknown. There is a need for continuing strengthening and updating of surveillance and response systems. PMID:24159830

  6. Maternal mortality in Vietnam in 1994-95.

    PubMed

    Hieu, D T; Hanenberg, R; Vach, T H; Vinh, D Q; Sokal, D

    1999-12-01

    This report presents the first population-based estimates of maternal mortality in Vietnam. All the deaths of women aged 15-49 in 1994-95 in three provinces of Vietnam were identified and classified by cause. Maternal mortality was the fifth most frequent cause of death. The maternal mortality ratio was 155 deaths per 100,000 live births. This ratio compares with the World Health Organization's estimates of 430 such deaths globally and 390 for Asia. The maternal mortality ratio in the delta regions of these provinces was half that of the mountainous and semimountainous regions. Because a larger proportion of the Vietnamese population live in delta regions than elsewhere, the maternal mortality ratio for Vietnam as a whole may be lower than that of the three provinces studied. Maternal mortality is low in Vietnam primarily because a relatively high proportion of deliveries take place in clinics and hospitals, where few women die in childbirth. Also, few women die of the consequences of induced abortion in Vietnam because the procedure is legal and easily available. PMID:10674328

  7. Forecasting approaches to the Mekong River

    NASA Astrophysics Data System (ADS)

    Plate, E. J.

    2009-04-01

    Hydrologists distinguish between flood forecasts, which are concerned with events of the immediate future, and flood predictions, which are concerned with events that are possible, but whose date of occurrence is not determined. Although in principle both involve the determination of runoff from rainfall, the analytical approaches differ because of different objectives. The differences between the two approaches will be discussed, starting with an analysis of the forecasting process. The Mekong River in south-east Asia is used as an example. Prediction is defined as forecast for a hypothetical event, such as the 100-year flood, which is usually sufficiently specified by its magnitude and its probability of occurrence. It forms the basis for designing flood protection structures and risk management activities. The method for determining these quantities is hydrological modeling combined with extreme value statistics, today usually applied both to rainfall events and to observed river discharges. A rainfall-runoff model converts extreme rainfall events into extreme discharges, which at certain gage points along a river are calibrated against observed discharges. The quality of the model output is assessed against the mean value by means of the Nash-Sutcliffe quality criterion. The result of this procedure is a design hydrograph (or a family of design hydrographs) which are used as inputs into a hydraulic model, which converts the hydrograph into design water levels according to the hydraulic situation of the location. The accuracy of making a prediction in this sense is not particularly high: hydrologists know that the 100-year flood is a statistical quantity which can be estimated only within comparatively wide error bounds, and the hydraulics of a river site, in particular under conditions of heavy sediment loads has many uncertainties. Safety margins, such as additional freeboards are arranged to compensate for the uncertainty of the prediction. Forecasts, on the

  8. Urbanization and climate change impacts on future urban flood risk in Can Tho city, Vietnam

    NASA Astrophysics Data System (ADS)

    Huong, H. T. L.; Pathirana, A.

    2011-12-01

    Urban development increases flood risk in cities due to local changes in hydrological and hydrometeorological conditions that increase flood hazard, and also to urban concentrations that increase the vulnerability. The relationship between the increasing urban runoff and flooding due to increased imperviousness better perceived than that between the cyclic impact of urban growth and the urban rainfall via microclimatic changes. The large-scale, global impacts due to climate variability and change could compound these risks. We present the case of a typical third world city - Can Tho (the biggest city in Mekong River Delta, Vietnam) - faced with multiple future challenges, namely: (i) climate change-driven sea-level rise and tidal effect, (ii) increase river runoff due to climate change, (iii) increased urban runoff driven by imperviousness, and (iv) enhancement of extreme rainfall due to urban growth-driven micro-climatic change (urban heat islands). A set of model simulations were used to assess the future impact of the combination of these influences. Urban growth of the city was projected up to year 2100 based on historical growth patterns, using a land-use simulation model (Dinamica-EGO). A dynamic limited-area atmospheric model (WRF), coupled with a detailed land-surface model with vegetation parameterization (Noah LSM), was employed in controlled numerical experiments to estimate the anticipated changes in extreme rainfall patterns due to urban heat island effect. Finally, a 1-D/2-D coupled urban-drainage/flooding model (SWMM-Brezo) was used to simulate storm-sewer surcharge and surface inundation to establish the increase in the flood risk resulting from the changes. The results show that, if the city develops as predicted, the maximum of inundation depth and area in Can Tho will increase by about 20%. The impact of climate change on inundation is more serious than that of urbanization. The worse case may occur if the sea level rises 100 cm and the flow from

  9. The heat flow study in the Tertiary Basin of Vietnam offshore

    SciTech Connect

    Huyen, T.

    1994-07-01

    In Vietnam, study of heat flow has paralleled petroleum exploration activities. For a long time there had only been results on temperature gradients in the Tertiary basin. Recently, with its participation in CCOP's project on the establishment of heat flow regional maps (1992-1993) and the government's mineral resources program (1993-1995) (Coded KT-01-18), Vietnam Petroleum Institute's group on heat flow obtained results on heat flow. A heat flow study in the oil basinal area in Vietnam has been conducted using data from 76 exploratory wells. Thermal conductivity of 427 cores was measured using the quick thermal conductivity meter (QTM) within temperature gradients of wells calculated from well log data and from testing data. The average heat flow of sedimentary basins in Vietnam follows: Hanoi graben, 125 Q (mW/m2); north Gulf of Tonkin, 87 Q (mW/m2); south Gulf of Tonkin, 119 Q (mW/m2); Danang Graben, 89 Q (mW/m2); northeast-south Conson, 88 Q (mW/m2); southwest-south Conson, 85 Q (mW/m2); Mekong Basin, 64 Q (mW/m2).

  10. RMIT Vietnam and Vietnam's Development: Risk and Responsibility

    ERIC Educational Resources Information Center

    Wilmoth, David

    2004-01-01

    To help bridge the gap between demand and supply for tertiary education, Vietnam has opened to direct, foreign providers, and the Royal Melbourne Institute of Technology (RMIT) International University Vietnam is the first of this category. By sponsoring a large project in a country that some see as risky, RMIT Vietnam needs to be triply viable.…

  11. Nile Delta

    Atmospheric Science Data Center

    2013-04-15

    article title:  The Nile River Delta     View Larger Image ... of eastern Africa. At the apex of the fertile Nile River Delta is the Egyptian capital city of Cairo. To the west are the Great Pyramids ...

  12. An assessment of sediment-transport processes in the Lower Mekong River based on deposit grain sizes, the CM technique and flow-energy data

    NASA Astrophysics Data System (ADS)

    Bravard, Jean-Paul; Goichot, Marc; Tronchère, Hervé

    2014-02-01

    The Lower Mekong River has been an important research topic for at least 15 years, notably in the fields of hydrology, fluvial geomorphology, and the impact of dams. Recent papers refer mostly to the impact of the Lancang chain of hydroelectric dams constructed on the Chinese section of the river. Among the pending scientific questions are (1) the upstream-downstream variations in the concentration and yield of suspended sediment and (2) the relative importance of sand in the total yield. The general consensus among the scientific community is that the relative importance of sand in suspended load is not the main scientific concern despite its extensive presence in the Mekong River channel, as noted by geomorphologists, and despite its extreme importance for the stability of the delta shoreline in Viet Nam. This paper contradicts the general consensus. Its objective is to present new information on the processes of sand transport in the Lower Mekong channel. Imagery, field observations, sampling on the river banks, and grain size analysis of sand deposits have been carried out between Chiang Sean (downstream of the Chinese border) and the delta. The C-M image technique served to discriminate between the various transport processes (bedload and different types of suspension). This technique helps in understanding the changing processes responsible for downstream sediment transfer in river channels. The results of this study are the following.

  13. The Mekong at climatic crossroads: Lessons from the geological past.

    PubMed

    Penny, Dan

    2008-05-01

    The wetlands of the lower Mekong River Basin are ecologically and socioeconomically significant, but they are threatened by predicted climatic change. The likely response of wetland ecosystems to altered flooding regimes and surface-water chemistry is unknown in detail and difficult to model. One way of exploring the impact of climate change on wetland ecosystems is to utilize proxy environmental data that reveal patterns of change over geological time. In recent years, the coverage and resolution of proxy climatic data have improved markedly in the region. Recent evidence of the South China Sea transgression into southern and central Cambodia and paleobotanical evidence from the Tonle Sap ("Great Lake") and elsewhere allow us to explore how periods of higher-than-present sea level and increased monsoon rainfall in the past have impacted the wetland ecology of the lower Mekong River Basin. PMID:18595270

  14. Caring for Vietnam Veterans.

    PubMed

    Elliott, Brenda

    2015-01-01

    Veterans of the Vietnam era are now the largest group of United States Veterans, and are at or approaching Social Security and Medicare eligibility. As a result, it is likely that home care clinicians will be caring for many patients who are Vietnam Veterans. The purpose of this article is to increase awareness of the unique healthcare needs of Vietnam Veterans. Having an understanding of military and Veteran culture can help inform home healthcare clinicians in ways to manage the unique healthcare needs of Veterans and engage previously learned behaviors and attitudes from military service. In addition, knowing the types of exposures and health risks specific to this era could be beneficial in identifying potential problems that may have not yet been addressed. PMID:26121505

  15. Modelling the Mekong: hydrological simulation for environmental impact studies

    NASA Astrophysics Data System (ADS)

    Kite, Geoff

    2001-11-01

    The Mekong, with a basin area of almost 800,000 km 2 and a length of 4500 km, is one of the most important rivers of the world. The many lakes and wetlands along the river, including Cambodia's Tonle Sap (Grand Lac), are major sources of fish for the riparian peoples and form an important part of the regional economy. This resource may be affected by proposed developments in the basin. Using climatic, topographic and land cover data from the Internet, the semi-distributed land-use runoff process (SLURP) hydrological model was used to simulate the complete hydrological cycle of the Mekong and its tributaries. Information on dam locations and reservoir characteristics were obtained from local sources. The model was verified by comparing simulated flows with recorded daily flows for the Mekong River and by comparing simulated levels of the Tonle Sap lake with recorded daily levels. The daily computed levels of the Tonle Sap lake were then converted into flooded areas for each land cover around the lake which were then used in a fish production model to evaluate the possible impacts of basin development on the fisheries. Model outputs may also be used to investigate issues such as water allocations and the effects of land use change or climate change on water resources and the aquatic and riparian environments.

  16. Impacts of Seasonal Flooding on Arsenic Release in Tropical River Deltas

    NASA Astrophysics Data System (ADS)

    Roberts, K. A.; Fendorf, S. E.; Schaefer, M.; Benner, S. G.; Salvador, A. K.

    2015-12-01

    More than 140 million people in South and Southeast Asia drink groundwater contaminated with toxic levels of arsenic. Arsenic release from sediment is controlled by oxidation of reduced organic carbon coupled to iron and arsenic reduction; this process occurs principally under anaerobic conditions and is constrained to surficial (<1 m depth) sediments in the Mekong Delta. However, there is limited knowledge of water level changes in seasonal wetlands that control carbon oxidation pathways and subsequently arsenic release from sediments to groundwater. During drained periods, soils undergo aerobic carbon oxidation, diverting electron flow away from iron and arsenic reduction, decreasing arsenic release from sediments to groundwater. Additionally, draining may lead to fresh Fe-oxide precipitation that sequesters As. We monitored soil moisture and porewater chemistry of a seasonal wetland in the Mekong Delta through a wetting and drying cycle. We examined temporal trends in arsenic release from the solid phase over the flooding and drying cycles. Based on frequent field measurements we determine the timing and magnitude of arsenic release in surficial sediments of seasonal wetlands typical of the Mekong Delta. These results show the importance of surface processes on arsenic release and aid in developing mechanistic and predictive models of arsenic concentrations in the subsurface throughout Asia.

  17. Education in Vietnam.

    ERIC Educational Resources Information Center

    Kieu, Tran; Chau, Nguyen Huu

    2000-01-01

    Describes and analyzes the development of education in Vietnam under reforms initiated in 1950, 1956, and 1981. Considers the implications of the country's focus on industrialization and modernization. Identifies current challenges to educational development, including the challenges of expanding the scale of education while improving the quality…

  18. Vietnam: An Historical Perspective.

    ERIC Educational Resources Information Center

    Shackford, Julie

    This book provides an overview of Vietnam's history prior to the U.S. presence there. The book begins with a chronology extending from prehistoric times to the defeat of the French at Dien Bien Phu in 1954. Each chapter provides background information along with a glossary, student activities, and project suggestions. Chapters include: (1)…

  19. Chemical weathering and CO₂ consumption in the Lower Mekong River.

    PubMed

    Li, Siyue; Lu, X X; Bush, Richard T

    2014-02-15

    Data on river water quality from 42 monitoring stations in the Lower Mekong Basin obtained during the period 1972-1996 was used to relate solute fluxes with controlling factors such as chemical weathering processes. The total dissolved solid (TDS) concentration of the Lower Mekong varied from 53 mg/L to 198 mg/L, and the median (114 mg/L) was compared to the world spatial median value (127 mg/L). Total cationic exchange capacity (Tz(+)) ranged from 729 to 2,607 μmolc/L, and the mean (1,572 μmolc/L) was 1.4 times higher than the world discharge-weighted average. Calcium and bicarbonate dominated the annual ionic composition, accounting for ~70% of the solute load that equalled 41.2×10(9)kg/y. TDS and major elements varied seasonally and in a predictable way with river runoff. The chemical weathering rate of 37.7t/(km(2)y), with respective carbonate and silicate weathering rates of 27.5t/(km(2) y) (13.8mm/ky) and 10.2t/(km(2) y) (3.8mm/ky), was 1.5 times higher than the global average. The CO2 consumption rate was estimated at 191×10(3)molCO2/(km(2)y) for silicate weathering, and 286×10(3)molCO2/(km(2)y) by carbonate weathering. In total, the Mekong basin consumed 228×10(9)molCO2/y and 152×10(9)molCO2/y by the combined weathering of carbonate and silicate, constituting 1.85% of the global CO2 consumption by carbonate weathering and 1.75% by silicates. This is marginally higher than its contribution to global water discharge ~1.3% and much higher than (more than three-fold) its contribution to world land surface area. Remarkable CO2 consumed by chemical weathering (380×10(9)mol/y) was similar in magnitude to dissolved inorganic carbon as HCO3(-) (370×10(9)mol/y) exported by the Mekong to the South China Sea. In this landscape, atmospheric CO2 consumption by rock chemical weathering represents an important carbon sink with runoff and physical erosion controlling chemical erosion. PMID:24291559

  20. Son preference in Vietnam.

    PubMed

    Haughton, J; Haughton, D

    1995-01-01

    This article assesses the strength of son preference in Vietnam, as reflected in fertility behavior. It formulates and estimates a proportional hazards model applied to birth intervals, and a contraceptive prevalence model, using household survey data from 2,636 ever-married women aged 15-49 with at least one living child who were interviewed for the Vietnam Living Standards Survey 1992-1993. Son preference is found to be strong by world standards, but nevertheless, it has a minor effect on fertility; in its absence, the total fertility rate would fall by roughly 10 percent from the current level of about 3.2 children per woman of reproductive age. PMID:8826072

  1. Opportunities in Vietnam

    SciTech Connect

    Burke, F.; Donoghue, N.

    1994-11-01

    Vietnam`s energy needs are clear and acute. Economic reforms have triggered a dynamic development process with a large and growing appetite for power. In view of the Vietnamese government`s own shortages of capital, private international power companies have been identified as key problem-solvers in the country`s efforts to meet a skyrocketing demand for energy resources. There are no restrictions on the nature of projects in which non-Vietnamese investors may participate. A number of legal issues need resolution before independent power producers can take advantage of the Republic`s recently created Builder-Operator-Transfer Contracts (the BOT Regulations). This paper discusses these regulations and how they affect independent power producers

  2. El Niño Southern Oscillation Influences River Bank Erosion on the Lower Mekong River

    NASA Astrophysics Data System (ADS)

    Darby, S. E.; Trieu, H. Q.; Carling, P. A.

    2009-12-01

    . However, both simulated time series exhibit quasi-periodic oscillations about these means. The Mekong’s flow regime is controlled by variations in meltwater regime, the intensity of the SE Asian monsoon, and the frequency and intensity of tropical cyclones that penetrate inland from the South China Sea. Since melt contributes only to (non-erosive) base flows, variability in glacier and snow melt contributions from Himalayan source areas are unlikely to significantly impact inter-annual variations in river bank erosion. However, inter-annual variability in the SE Asian monsoon and tropical cyclone dynamics may both be related, albeit in a complex manner, to the El Niño Southern Oscillation (ENSO). Cross-wavelet transform and wavelet coherence analyses indicate statistically significant (at 95% limit) coherence between ENSO and simulated river bank erosion, but at both sites only since about 1980. During this recent period the ENSO and fluvial erosion time series are in anti-phase; that is ENSO cold phases are associated with enhanced rates of river bank erosion. This is as expected, since ENSO cold phases are associated with earlier onset and enhanced intensity of the monsoon, while the number of intense tropical storm systems making landfall over Vietnam and moving across the Lower Mekong Basin is also higher.

  3. Vietnam in the English Classroom.

    ERIC Educational Resources Information Center

    Johannessen, Larry R.

    Vietnam War literature offers students a unique mix of themes which in many ways speak directly to them as, perhaps, no other literature is able to. This literature can help them better understand literature, history, the world they live in, and themselves, as well as the Vietnam War. A sequence of classroom activities (beginning with an…

  4. Developing School Psychology in Vietnam

    ERIC Educational Resources Information Center

    Le, Phuong; Hagans, Kristi; Powers, Kristin; Hass, Michael

    2011-01-01

    Like China, Vietnam is a communist country with increasingly capitalist economic policies. A fundamental change occurred in these policies with the enactment of Vietnam's "doi moi" (renovation) policy in 1986 that called for a "free market with socialist orientations." However, this economic modernization has inadvertently changed the social…

  5. The Lessons of the Vietnam War.

    ERIC Educational Resources Information Center

    Starr, Jerold M., Ed.

    This text book on the Vietnam War is to be used in teaching high students. Each of the volume's 12 chapters is a self-contained unit on an aspect of the War. The chapters are: (1) Introduction to Vietnam: land, history, and culture; (2) America at war in Vietnam: decisions and consequences; (3) Was the Vietnam War legal? (4) who fought for the…

  6. Clade-level Spatial Modelling of HPAI H5N1 Dynamics in the Mekong Region Reveals New Patterns and Associations with Agro-Ecological Factors

    PubMed Central

    Artois, Jean; Newman, Scott H.; Dhingra, Madhur S.; Chaiban, Celia; Linard, Catherine; Cattoli, Giovanni; Monne, Isabella; Fusaro, Alice; Xenarios, Ioannis; Engler, Robin; Liechti, Robin; Kuznetsov, Dmitri; Pham, Thanh Long; Nguyen, Tung; Pham, Van Dong; Castellan, David; Von Dobschuetz, Sophie; Claes, Filip; Dauphin, Gwenaëlle; Inui, Ken; Gilbert, Marius

    2016-01-01

    The highly pathogenic avian influenza (HPAI) H5N1 virus has been circulating in Asia since 2003 and diversified into several genetic lineages, or clades. Although the spatial distribution of its outbreaks was extensively studied, differences in clades were never previously taken into account. We developed models to quantify associations over time and space between different HPAI H5N1 viruses from clade 1, 2.3.4 and 2.3.2 and agro-ecological factors. We found that the distribution of clades in the Mekong region from 2004 to 2013 was strongly regionalised, defining specific epidemiological zones, or epizones. Clade 1 became entrenched in the Mekong Delta and was not supplanted by newer clades, in association with a relatively higher presence of domestic ducks. In contrast, two new clades were introduced (2.3.4 and 2.3.2) in northern Viet Nam and were associated with higher chicken density and more intensive chicken production systems. We suggest that differences in poultry production systems in these different epizones may explain these associations, along with differences in introduction pressure from neighbouring countries. The different distribution patterns found at the clade level would not be otherwise apparent through analysis treating all outbreaks equally, which requires improved linking of disease outbreak records and genetic sequence data. PMID:27453195

  7. Clade-level Spatial Modelling of HPAI H5N1 Dynamics in the Mekong Region Reveals New Patterns and Associations with Agro-Ecological Factors.

    PubMed

    Artois, Jean; Newman, Scott H; Dhingra, Madhur S; Chaiban, Celia; Linard, Catherine; Cattoli, Giovanni; Monne, Isabella; Fusaro, Alice; Xenarios, Ioannis; Engler, Robin; Liechti, Robin; Kuznetsov, Dmitri; Pham, Thanh Long; Nguyen, Tung; Pham, Van Dong; Castellan, David; Von Dobschuetz, Sophie; Claes, Filip; Dauphin, Gwenaëlle; Inui, Ken; Gilbert, Marius

    2016-01-01

    The highly pathogenic avian influenza (HPAI) H5N1 virus has been circulating in Asia since 2003 and diversified into several genetic lineages, or clades. Although the spatial distribution of its outbreaks was extensively studied, differences in clades were never previously taken into account. We developed models to quantify associations over time and space between different HPAI H5N1 viruses from clade 1, 2.3.4 and 2.3.2 and agro-ecological factors. We found that the distribution of clades in the Mekong region from 2004 to 2013 was strongly regionalised, defining specific epidemiological zones, or epizones. Clade 1 became entrenched in the Mekong Delta and was not supplanted by newer clades, in association with a relatively higher presence of domestic ducks. In contrast, two new clades were introduced (2.3.4 and 2.3.2) in northern Viet Nam and were associated with higher chicken density and more intensive chicken production systems. We suggest that differences in poultry production systems in these different epizones may explain these associations, along with differences in introduction pressure from neighbouring countries. The different distribution patterns found at the clade level would not be otherwise apparent through analysis treating all outbreaks equally, which requires improved linking of disease outbreak records and genetic sequence data. PMID:27453195

  8. Sediment-related impacts due to upstream reservoir trapping, the Lower Mekong River

    NASA Astrophysics Data System (ADS)

    Kummu, Matti; Varis, Olli

    2007-03-01

    A sharp decrease in total suspended solids (TSS) concentration has occurred in the Mekong River after the closure of the Manwan Dam in China in 1993, the first of a planned cascade of eight dams. This paper describes the upstream developments on the Mekong River, concentrating on the effects of hydropower dams and reservoirs. The reservoir-related changes in total suspended solids, suspended sediment concentration (SSC), and hydrology have been analyzed, and the impacts of such possible changes on the Lower Mekong Basin discussed. The theoretical trapping efficiency of the proposed dams has been computed and the amount of sediment to be trapped in the reservoirs estimated. The reservoir trapping of sediments and the changing of natural flow patterns will impact the countries downstream in this international river basin. Both positive and negative possible effects of such impacts have been reviewed, based on the available data from the Mekong and studies on other basins.

  9. Managing fish, flood plains and food security in the Lower Mekong Basin.

    PubMed

    Jensen, J G

    2001-01-01

    The "Lower Mekong Basin" in this paper refers to the part of the Mekong River Basin which is shared by Cambodia, Laos, Thailand and Viet Nam, all members of the Mekong River Commission, consisting of approx. 2,400 km of mainstream river, numerous tributaries and huge flood plains. Few river basins produce as much fish as the Mekong River Basin, and the fishery in the Lower Mekong Basin is among the biggest and most productive inland fisheries in the world. The flood plains of the Lower Mekong produce some four times as much fish per square kilometre as the North Sea, which is among the most productive marine areas in the world. It is quite clear that the fisheries in the Mekong Basin are very important for the population in respect to their food security and income. Its importance in nutrition is highest in the rural areas, where there are few other low cost sources of protein, and even in highland areas fish is of crucial importance in the diet. Most fish species in the Mekong Basin are migratory, and the economically most important ones are certainly so. However, with economic development gaining speed, the impact on migratory patterns and the competition for the water resources are becoming stronger. The water resources offer a large number of opportunities, and a lot of economic activities need access to the water resources for their development. However, what is seen in one sector as an opportunity may be considered as a threat in another, and a careful balance is necessary in order not to lose opportunities in important sectors. The fate of a large number of river basins in the world is frightening. Most have been left biologically near dead, with some of the big rivers reduced for a time, or forever, to be used as waste water canals for the new industries, and others almost dried out from excessive water extraction before they reach the sea. PMID:11419123

  10. Dam-Induced Sediment Starvation in Deltas: Implications for the Mekong

    NASA Astrophysics Data System (ADS)

    Kondolf, G. M.; Rubin, Z.; Minear, J. T.

    2014-12-01

    As the climate warms, especially rapid responses are being seen in the Arctic. Melting ice and thawing soils have wide ranging impacts including changes to ecosystems. What that means depends, in no small measure, on your understanding of—and relationship—to the ecosystems as evidenced by the currencies in which you measure ecosystem change. Thus, an ecologist will tend to focus on the impacts on energy flow and organizational complexity; conservationists on ecosystem services and biodiversity; and subsistence hunters on food security and cultural identity. Policy makers (a poorly defined group) will attempt to integrate all of the above within the very real limits of their fluency with each currency. The situation is further complicated by unavoidable ambiguities; abiotic and biotic influences can be difficult to distinguish, scale impacts ecosystem response unevenly, and ecosystems are useful concepts but not amenable to precise boundaries. As the risks of climate change become more evident, the cost of ambiguities and disparate currencies increases. It is imperative that scientists, conservationists, subsistence hunters, and policy makers appreciate and overcome their different ways of understanding environmental change.

  11. Pharmacy Education in Vietnam

    PubMed Central

    Bedouch, Pierrick; Nguyen, Thi-Hoai; Nguyen, Thi-Lien-Huong; Hoang, Thi-Kim-Huyen; Calop, Jean; Allenet, Benoît

    2013-01-01

    Pharmacy education programs in Vietnam are complex and offer various career pathways. All include theory and laboratory modules in general, foundation, and pharmaceutical knowledge; placements in health facilities; and a final examination. The various pharmacy degree programs allow specialization in 1 or more of 5 main fields: (1) drug management and supply, (2) drug development and production, (3) pharmacology and clinical pharmacy, (4) traditional medicine and pharmacognosy, and (5) drug quality control, which are offered as main specialization options during the reformed undergraduate and postgraduate programs. However, pharmacy education in Vietnam in general remains product oriented and clinical pharmacy training has not received adequate attention. Only students who have obtained the bachelor of pharmacy degree, which requires a minimum of 5 years of study, are considered as fully qualified pharmacists. In contrast, an elementary diploma in pharmacy awarded after 1 year of pharmacy study permits entry into more junior pharmacy positions. Since the 2000s, there has been a surge in the number and types of schools offering pharmacy qualifications at various levels. PMID:23966717

  12. Trichinellosis in Vietnam.

    PubMed

    Van De, Nguyen; Thi Nga, Vu; Dorny, Pierre; Vu Trung, Nguyen; Ngoc Minh, Pham; Trung Dung, Do; Pozio, Edoardo

    2015-06-01

    Trichinellosis is a zoonotic parasitic disease with a worldwide distribution. The aim of this work was to describe the epidemiological and clinical data of five outbreaks of trichinellosis, which affected ethnic minorities living in remote mountainous areas of northwestern Vietnam from 1970 to 2012. Trichinellosis was diagnosed in 126 patients, of which 11 (8.7%) were hospitalized and 8 (6.3%) died. All infected people had consumed raw pork from backyard and roaming pigs or wild boar at wedding, funeral, or New Year parties. The short incubation period (average of 9.5 days), the severity of the symptoms, which were characterized by diarrhea, abdominal pain, fever, myalgia, edema, weight loss, itch, and lisping, and the high mortality, suggest that patients had ingested a high number of larvae. The larval burden in pigs examined in one of the outbreaks ranged from 70 to 879 larvae/g. These larvae and those collected from a muscle biopsy taken from a patient from the 2012 outbreak were identified as Trichinella spiralis. Data presented in this work show that the northern regions of Vietnam are endemic areas for Trichinella infections in domestic pigs and humans. PMID:25846295

  13. Trichinellosis in Vietnam

    PubMed Central

    De, Nguyen Van; Nga, Vu Thi; Dorny, Pierre; Trung, Nguyen Vu; Minh, Pham Ngoc; Dung, Do Trung; Pozio, Edoardo

    2015-01-01

    Trichinellosis is a zoonotic parasitic disease with a worldwide distribution. The aim of this work was to describe the epidemiological and clinical data of five outbreaks of trichinellosis, which affected ethnic minorities living in remote mountainous areas of northwestern Vietnam from 1970 to 2012. Trichinellosis was diagnosed in 126 patients, of which 11 (8.7%) were hospitalized and 8 (6.3%) died. All infected people had consumed raw pork from backyard and roaming pigs or wild boar at wedding, funeral, or New Year parties. The short incubation period (average of 9.5 days), the severity of the symptoms, which were characterized by diarrhea, abdominal pain, fever, myalgia, edema, weight loss, itch, and lisping, and the high mortality, suggest that patients had ingested a high number of larvae. The larval burden in pigs examined in one of the outbreaks ranged from 70 to 879 larvae/g. These larvae and those collected from a muscle biopsy taken from a patient from the 2012 outbreak were identified as Trichinella spiralis. Data presented in this work show that the northern regions of Vietnam are endemic areas for Trichinella infections in domestic pigs and humans. PMID:25846295

  14. Deliberation and Scale in Mekong Region Water Governance

    NASA Astrophysics Data System (ADS)

    Dore, John; Lebel, Louis

    2010-07-01

    Understanding the politics of deliberation, scales, and levels is crucial to understanding the social complexity of water-related governance. Deliberative processes might complement and inform more conventional representational and bureaucratic approaches to planning and decision-making. However, they are also subject to scale and level politics, which can confound institutionalized decision-making. Scale and level contests arise in dialogues and related arenas because different actors privilege particular temporal or spatial scales and levels in their analysis, arguments, and responses. Scale contests might include whether to privilege administrative, hydrological, ecosystem, or economic boundaries. Level contests might include whether to privilege the subdistrict or the province, the tributary watershed or the international river basin, a river or a biogeographic region, and the local or the regional economy. In the Mekong Region there is a recurrent demand for water resources development projects and major policies proposed by governments and investors to be scrutinized in public. Deliberative forms of engagement are potentially very helpful because they encourage supporters and critics to articulate assumptions and reasoning about the different opportunities and risks associated with alternative options, and in doing so, they often traverse and enable higher-quality conversations within and across scales and within and between levels. Six case studies from the Mekong Region are examined. We find evidence that scale and level politics affects the context, process, content, and outcomes of deliberative engagement in a region where public deliberation is still far from being a norm, particularly where there are sensitive and far-reaching choices to be made about water use and energy production.

  15. Women take initiative in Vietnam.

    PubMed

    1992-04-01

    Improvements in the health of Vietnamese people is currently being hampered by the lack of medical equipment and medicine. This, despite strong governmental commitment and a vast national health care system that serves the grassroots through a network of village health stations. Vietnam needs strong support to overcome these serious shortages according to Dr Nguyen Thi Ngoc Phuong, Vicechairwoman of the National Assembly of Vietnam. The JOICFP has initiated an Integrated Project (IP) to tackle women's reproductive health issues. The IP supports activities to send supplies and medical equipment from Japan to pilot communes. The Nagano Chapter of the Women's League has been supporting grassroots projects in Vietnam with donations of equipment and funds. Woman play a critical role in development because they account for 50% of the population and work under the double burden of family and employment. In Vietnam, women are a political force that link the government with the grassroots organizations. O the 496 members of Parliament, 88 are women. The IP has greatly improved contraceptive availability. Now condoms, IUDs, the pill are available. Greater access to gynecological examinations are also made possible by the IP. The women of Japan have a lot to offer the women of Vietnam. Their experiences of post World War II allowed them to develop a very effective system of maternal/child health care in this period. The lessons they learned during this time can be of immense value to the health care system of Vietnam. PMID:12285342

  16. 77 FR 27435 - Certain Frozen Fish Fillets From the Socialist Republic of Vietnam: Final Results of the New...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-05-10

    ... Vietnam: Preliminary Results of the New Shipper Review, 76 FR 77485 (December 13, 2011) (``Preliminary... the New Shipper Review, 77 FR 1470 (January 10, 2012). \\4\\ The Catfish Farmers of America and... Catfish, Delta Pride Catfish, Inc., Harvest Select Catfish, Inc., Heartland Catfish Company, Pride of...

  17. Ecological health monitoring of the Mekong River by using benthic algae in 2003-2004

    NASA Astrophysics Data System (ADS)

    Kunpradid, T.

    2005-05-01

    The monitoring of ecological health of the Mekong River by using benthic algae was carried out from 2003 - 2004. Thirty sampling sites along the Mekong River and its tributaries were selected in Laos, Thailand, Cambodia and Veitnam. In this investigation, the distribution of some species of benthic algae in different environments revealed that there was a significant relationship in the presence of them to the water quality, and these species could be used as a potential biomonitor of water quality in the Mekong River. One hundred and eighty six species of benthic diatoms and 46 species of macroalgae were found. Some dominant species of benthic algae could be used as biomonitors to assess water quality. Hydrodictyon recticulatum and Microspora floccosa and indicated clean-moderate water quality; Audouinella cylindrica, Cladophora glomerata, Achnanthes inflate and Cymbella turgidula indicated moderate water quality; Stigeoclonium flagelliforum, Aulacoseira granulata and Cymbella tumida indicated moderate-polluted water quality and Caloglossa leprieurii, Gomphonema parvulum and Nitzschia clausii indicated polluted water quality. The ecological health assessment of the Mekong River by using the species of benthic algae as biomonitors reveled that in the upstream and tributaries revealed moderate water quality. In contrast, some sites in the lower Mekong showed moderate-polluted to polluted water quality.

  18. Higher Education in Vietnam: Change and Response.

    ERIC Educational Resources Information Center

    Sloper, David, Ed.; Le, Thac Can, Ed.

    This collection of 12 essays examines the development of higher education in Vietnam, focusing on current issues related to educational reform, expansion, and funding. They are: (1) "Higher Education in Vietnam: The Door Opens--From Inside" (Le Thac Can and David Sloper); (2) "Socio-Economic Background of Vietnam Since 1986: Impact on Education…

  19. Mississippi Delta

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The streamers of clouds draped over the Gulf of Mexico in this true-color MODIS image from February 27, 2002, suggest that a cold, dry wind was blowing southward over the United States and began to pick up moisture over the Gulf, causing these strips of clouds. That the clouds didn't pick up until some distance from the coastline allowed MODIS to get a perfect view of the dynamic Gulf Coast environment spanning (left to right) Texas, Louisiana, Mississippi, Alabama, and Florida's Western Panhandle. The Mississippi River runs roughly down the center of the image, and is joined in Louisiana by the Red River coming in from the northwest. Over the past 7000 years, the actual delta, where the main river channel empties into the Gulf, has wandered around what we now think of as the Louisiana coast. Considering all the sediment visible in this image, it's not hard to imagine that the river carries about 2.4 billion kilograms of sediment into the Gulf each year. Deposition of some of this sediment has been building up the current delta, called the Birdfoot Delta, for obvious reasons, for about 700 years. The coastal waters are alive with microscopic organisms called phytoplankton, which contain colorful pigments, including chlorophyll, for harvesting sunlight. Beyond the sediment plume off Louisiana, the waters are very dark, which could indicate that a large amount of chlorophyll is present, absorbing lots of sunlight and causing the water to appear dark. Farther south, the waters appear bright blue, which could be a signature of coccolithophores, which use highly reflective calcium carbonate to build scaly coverings for themselves. The brighter offshore waters could also be caused by a blue-green algae called Trichodesmium, an organism that can not only harness carbon dioxide for photosynthesis, but can also take nitrogen from the air and turn it into a form that can be used by living organisms. Credit: Jacques Descloitres, MODIS Land Rapid Response Team, NASA/GSFC

  20. Human exposure to arsenic from drinking water in Vietnam.

    PubMed

    Agusa, Tetsuro; Trang, Pham Thi Kim; Lan, Vi Mai; Anh, Duong Hong; Tanabe, Shinsuke; Viet, Pham Hung; Berg, Michael

    2014-08-01

    Vietnam is an agricultural country with a population of about 88 million, with some 18 million inhabitants living in the Red River Delta in Northern Vietnam. The present study reports the chemical analyses of 68 water and 213 biological (human hair and urine) samples conducted to investigate arsenic contamination in tube well water and human arsenic exposure in four districts (Tu Liem, Dan Phuong, Ly Nhan, and Hoai Duc) in the Red River Delta. Arsenic concentrations in groundwater in these areas were in the range of <1 to 632 μg/L, with severe contamination found in the communities Ly Nhan, Hoai Duc, and Dan Phuong. Arsenic concentrations were markedly lowered in water treated with sand filters, except for groundwater from Hoai Duc. Human hair samples had arsenic levels in the range of 0.07-7.51 μg/g, and among residents exposed to arsenic levels ≥50 μg/L, 64% of them had hair arsenic concentrations higher than 1 μg/g, which is a level that can cause skin lesions. Urinary arsenic concentrations were 4-435 μg/g creatinine. Concentrations of arsenic in hair and urine increased significantly with increasing arsenic content in drinking water, indicating that drinking water is a significant source of arsenic exposure for these residents. The percentage of inorganic arsenic (IA) in urine decreased with age, whereas the opposite trend was observed for monomethylarsonic acid (MMA) in urine. Significant co-interactions of age and arsenic exposure status were also detected for concentrations of arsenic in hair and the sum of IA, MMA, and dimethylarsinic acid (DMA) in urine and %MMA. In summary, this study demonstrates that a considerable proportion of the Vietnamese population is exposed to arsenic levels of chronic toxicity, even if sand filters reduce exposure in many households. Health problems caused by arsenic ingestion through drinking water are increasingly reported in Vietnam. PMID:24262873

  1. Some Cenozoic hydrocarbon basins on the continental shelf of Vietnam

    SciTech Connect

    Dien, P.T.

    1994-07-01

    The formation of the East Vietnam Sea basins was related to different geodynamic processes. The pre-Oligocene basement consists of igneous, metamorphic, and metasediment complexes. The Cretaceous-Eocene basement formations are formed by convergence of continents after destruction of the Tethys Ocean. Many Jurassic-Eocene fractured magmatic highs of the Cuulong basin basement constitute important reservoirs that are producing good crude oil. The Paleocene-Eocene formations are characterized by intramountain metamolasses, sometimes interbedded volcanic rocks. Interior structures of the Tertiary basins connect with rifted branches of the widened East Vietnam Sea. Bacbo (Song Hong) basin is predominated by alluvial-rhythmic clastics in high-constructive deltas, which developed on the rifting and sagging structures of the continental branch. Petroleum plays are constituted from Type III source rocks, clastic reservoirs, and local caprocks. Cuulong basin represents sagging structures and is predominated by fine clastics, with tidal-lagoonal fine sandstone and shalestone in high-destructive deltas that are rich in Type II source rocks. The association of the pre-Cenozoic fractured basement reservoirs and the Oligocene-Miocene clastic reservoir sequences with the Oligocene source rocks and the good caprocks is frequently met in petroleum plays of this basin. Nan Conson basin was formed from complicated structures that are related to spreading of the oceanic branch. This basin is characterized by Oligocene epicontinental fine clastics and Miocene marine carbonates that are rich in Types I, II, and III organic matter. There are both pre-Cenozoic fractured basement reservoirs, Miocene buildup carbonate reservoir rocks and Oligocene-Miocene clastic reservoir sequences, in this basin. Pliocene-Quaternary sediments are sand and mud carbonates in the shelf facies of the East Vietnam Sea back-arc basin. Their great thickness provides good conditions for maturation and trapping.

  2. Environmental arsenic epidemiology in the Mekong river basin of Cambodia.

    PubMed

    Phan, Kongkea; Kim, Kyoung-Woong; Hashim, Jamal Hisham

    2014-11-01

    We investigated relationship of arsenicosis symptoms with total blood arsenic (BAs) and serum albumin (SAlb) of residents in the Mekong River basin of Cambodia. We found that arsenicosis patients had significantly higher BAs and lower SAlb than asymptomatic villagers (Mann-Whitney U test, p<0.01). Arsenicosis symptoms were found to be 76.4% (1.764 times) more likely to develop among individuals having an SAlb≤44.3gL(-1) than among those who had an SAlb>44.3gL(-1) (OR=1.764, 95% CI=0.999-3.114) and 117.6% (2.176 times) as likely to occur among those with BAs>5.73µgL(-1) than for those having BAs≤5.73µgL(-1) (OR=2.176, 95% CI=1.223-3.872). Furthermore, a significant negative correlation was also found between BAs and SAlb (rs (199)=-0.354, p<0.0001). As such, this study suggests that people with low SAlb and/or high BAs are likely to rapidly develop arsenicosis symptoms. PMID:25262072

  3. Epidemiology of Strongyloides stercoralis on Mekong islands in southern Laos.

    PubMed

    Vonghachack, Youthanavanh; Sayasone, Somphou; Bouakhasith, Dalouny; Taisayavong, Keoka; Akkavong, Kongsap; Odermatt, Peter

    2015-01-01

    Strongyloides stercoralis is a neglected helminth infection potentially that can lead to systemic infection in immunocompromised individuals. In Lao People's Democratic Republic (Lao PDR, Laos), information on S. stercoralis infection is scarce. We assessed S. stercoralis infection and associated risk factors and symptoms on the Mekong islands in Southern Laos. Baermann and Kato-Katz techniques were performed on two stool samples from each individual to detect S. stercoralis larvae and concomitant helminth infections. Among 729 individuals, 41.0% were infected with S. stercoralis. Men were at higher risk than women (OR 1.97, 95% CI 1.45-2.67). Urticaria and body itching was associated with S. stercoralis infection (OR 2.4, 95% CI 1.42-4.05). Infection with Opisthorchis viverrini (72.2%), Schistosoma mekongi (12.8%), and hookworm (56.1%) were very common. Few infections with Trichuris trichiura (3.3%), Ascaris lumbricoides (0.3%) and Taenia spp. (0.3%) were detected. The majority of helminth infections were of light intensity, with prevalences of 80.4%, 92.9%, 64.5%, 100% and 100%, for O. viverrini, hookworm, S. mekongi, T. trichiura and A. lumbricoides, respectively. Nevertheless, heavy infection intensities were observed for O. viverrini (1.0%), S. mekongi (14.0%) and hookworm (2.9%). S. stercoralis is highly endemic on the islands of Khong district, Champasack province, Southern Laos. The national helminth control programme should take action to control this helminth infection. PMID:25291044

  4. Opisthorchis viverrini infections and associated risk factors in a lowland area of Binh Dinh Province, Central Vietnam.

    PubMed

    Dao, Thanh Thi Ha; Bui, Tuan Van; Abatih, Emmanuel Nji; Gabriël, Sarah; Nguyen, Thanh Thi Giang; Huynh, Quang Hong; Nguyen, Chuong Van; Dorny, Pierre

    2016-05-01

    Opisthorchiasis caused by Opisthorchis viverrini is a major public health problem in the Mekong Basin in South East Asia. It is associated with cholangiocarcinoma, a fatal cancer of the bile duct, which is very common in some areas of Thailand and Lao PDR. Although there is evidence of opisthorchiasis in the central and Southern provinces of Vietnam, data are scarce and Vietnam is often not considered an opisthorchiasis endemic area in the international literature. We conducted a cross-sectional survey in June 2015 in a lowland rural area of Binh Dinh Province in Central Vietnam to investigate the apparent prevalence of O. viverrini infection in the population and the associated risk factors. A total of 254 stool samples were collected and examined by the Kato Katz method. Consenting people shedding Opisthorchis-like eggs with their stools were treated with praziquantel and MgSO4 and adult worms were collected from stools for morphological and molecular identifications. Risk factors were studied with a structured questionnaire and the association with infection was evaluated by univariate and multivariate Firth's logistic regression analysis. The apparent prevalence in the investigated population determined by stool examination was 11.4% (CI: 8-16%). Infection with O. viverrini was confirmed in all 11 individuals consenting to receive praziquantel treatment and subsequent worm recovery from stools. The mean number of worms recovered after treatment/purgation was 14.5 (range 2-44). Male gender and the consumption of dishes prepared from raw small wild-caught freshwater fish (Carassius auratus) were found to be significant risk factors associated with opisthorchiasis in the area. These findings confirm the presence of O. viverrini infection in Central Vietnam related to the consumption of raw fish dishes. Awareness campaigns and control programs should be implemented in the region to combat this potentially fatal fluke infection. PMID:26872984

  5. Adaptive Delta Management: cultural aspects of dealing with uncertainty

    NASA Astrophysics Data System (ADS)

    Timmermans, Jos; Haasnoot, Marjolijn; Hermans, Leon; Kwakkel, Jan

    2016-04-01

    Hofstede's (1983) cultural dimensions, of which uncertainty avoidance and long-term orientation are of particular relevance for our analysis. Our conclusions comment on the suitability of approaches in Adaptive Delta Management rooted in different management theories are more suitable for specific delta countries than others. The most striking conclusion is the unsuitability of rational policy analytic approaches for The Netherlands. Although surprising this conclusion finds some support in the process dominated approach taken in the Dutch Delta Program. In addition, the divergence between Vietnam, Bangladesh and Myanmar, all located in South East Asia, is striking. References Hofstede, G. (1983). The cultural relativity of organizational practices and theories. Journal of international business studies, 75-89. Jos Timmermans, Marjolijn Haasnoot, Leon Hermans, Jan Kwakkel, Martine Rutten and Wil Thissen (2015). Adaptive Delta Management: Roots and Branches, IAHR The Hague 2015.

  6. Mississippi Delta

    NASA Technical Reports Server (NTRS)

    2002-01-01

    The Mississippi River delta teems with sediment deposited by the river as it flows into the Gulf of Mexico in this true-color image captured by MODIS on October 15, 2001. The sediment, which is marked by brown swirls in the Gulf, provides nutrients for the bloom of phytoplankton visible as blue-green swirls off the coastline. In the high-resolution image the city of Memphis can be seen in the southwest corner of Tennessee, which is just to left of center at the top of the image. The brown coloration that encompasses Memphis and either side of the river, as flows north to south along the left side of the image, is the river's flood plain. Also visible, in the upper-right hand corner of the image is the southern end of the Appalachian Mountains.

  7. [Health system of Vietnam].

    PubMed

    Matsuda, S

    1994-01-01

    Vietnam's health system consists of four levels: national, provincial/special city, prefecture/ward, and basic unit of town or village. Health care is managed by the Health Department at the national level and by the health and welfare section of the People's Committee at all other levels. Actual medical services are provided by the National Central Hospital at the national level, by general hospitals at the provincial/special city level, by general hospitals and multi-purpose health clinics at the prefecture/ward level, and by health stations at the basic unit level. Health services provide not only doctors, nurses, and pharmacists, but also paramedical staff, especially at the basic unit level. Just as with other developing countries, infectious diseases are the most important priorities in health/medical care policies; especially malaria, which is the number one priority followed by diarrhea. Because of well-established health stations at the basic unit level throughout the country and a relatively sufficient supply of medication, the mortality rate due to the above is low. The maternal/infant health care index of 1988 shows the following: low birth weight (14%); maternal mortality (1.4/1000); neonatal mortality (33.5/1000); and perinatal mortality (22.5/1000). Malnutrition of children under 3 years of age in farming areas, insufficient supply of drinking water, and lack of industrial health insurance are some of the problems yet to be solved. It is hoped that medical services can be a significant part of the comprehensive economic development program within the framework of Japan's international cooperation/assistance. PMID:8111100

  8. Vietnam recommended dietary allowances 2007.

    PubMed

    Khan, Nguyen Cong; Hoan, Pham Van

    2008-01-01

    It has been well acknowledged that Vietnam is undergoing a nutrition transition. With a rapid change in the country's reform and economic growth, food supply at the macronutrient level has improved. Changes of the Vietnamese diet include significantly more foods of animal origin, and an increase of fat/oils, and ripe fruits. Consequently, nutritional problems in Vietnam now include not only malnutrition but also overweight/obesity, metabolic syndrome and other chronic diseases related to nutrition and lifestyles. The recognition of these shifts, which is also associated with morbidity and mortality, was a major factor in the need to review and update the Recommended Dietary Allowances (RDA) for the Vietnamese population. This revised RDA established an important science-based tool for evaluation of nutrition adequacy, for teaching, and for scientific communications within Vietnam. It is expected that the 2007 Vietnam RDA and its conversion to food-based dietary guidelines will facilitate education to the public, as well as the policy implementation of programs for prevention of non-communicable chronic diseases and addressing the double burden of both under and over nutrition. PMID:18460440

  9. Data on Vietnam Era Veterans.

    ERIC Educational Resources Information Center

    Veterans Administration, Washington, DC. Office of the Controller.

    Statistical data are presented on Vietnam era veterans for the following topics: employment status, medical status, compensation and pension, education, housing assistance, expenditures, and demographic information. The estimated number and age of veterans in civil life, categorized by sex and state, and the educational attainment of veterans at…

  10. Hydrologic evaluation of the lower Mekong River Basin with the Soil and Water Assessment Tool model

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recently the Mekong River Commission (MRC) has developed a computer package so-called Decision Support Framework (DSF) under the Water Utilization Programme (WUP). The development was aimed to implement the 1995 Agreement on the Water Utilization with sustainable development and equitable manner of ...

  11. Sex attractants for moths of Vietnam: field attraction by synthetic lures baited with known lepidopteran pheromones.

    PubMed

    Tran, Van Hai; Pham, Kim Son; Inomata, Shin-ichi; Ando, Tetsu

    2002-07-01

    Screening tests of synthetic lepidopteran sex pheromones were carried out at orchards in the Mekong Delta over an approximately two-year period starting from December 1998. Monoenyl acetates with a C10-C14 chain attracted six species distributed mainly in Southeast Asia: Adoxophyes privatana, Archips atrolucens, and Meridemisfurtiva in the Tortricidae family, and Argyrogramma signata. Spodoptera pectinicornis, and Zonoplusia ochreata in the Noctuidae family. These were in addition to three other noctuid species that had been attracted during previous field examinations within a temperate zone. Furthermore, male moths of three species belonging to the Cosmopterigidae, Gelechiidae, or Batrachedridae family were also caught by traps baited with acetates. Trienes with a C18-C21 chain and their monoepoxides. which are stereotypes of pheromones secreted by females in the Geometridae family, failed to attract any geometrid male, but attracted three Noctuidae species and four Arctiidae species. PMID:12199508

  12. Agro-Environmental Determinants of Avian Influenza Circulation: A Multisite Study in Thailand, Vietnam and Madagascar

    PubMed Central

    Paul, Mathilde C.; Gilbert, Marius; Desvaux, Stéphanie; Rasamoelina Andriamanivo, Harena; Peyre, Marisa; Khong, Nguyen Viet; Thanapongtharm, Weerapong; Chevalier, Véronique

    2014-01-01

    Outbreaks of highly pathogenic avian influenza have occurred and have been studied in a variety of ecological systems. However, differences in the spatial resolution, geographical extent, units of analysis and risk factors examined in these studies prevent their quantitative comparison. This study aimed to develop a high-resolution, comparative study of a common set of agro-environmental determinants of avian influenza viruses (AIV) in domestic poultry in four different environments: (1) lower-Northern Thailand, where H5N1 circulated in 2004–2005, (2) the Red River Delta in Vietnam, where H5N1 is circulating widely, (3) the Vietnam highlands, where sporadic H5N1 outbreaks have occurred, and (4) the Lake Alaotra region in Madagascar, which features remarkable similarities with Asian agro-ecosystems and where low pathogenic avian influenza viruses have been found. We analyzed H5N1 outbreak data in Thailand in parallel with serological data collected on the H5 subtype in Vietnam and on low pathogenic AIV in Madagascar. Several agro-environmental covariates were examined: poultry densities, landscape dominated by rice cultivation, proximity to a water body or major road, and human population density. Relationships between covariates and AIV circulation were explored using spatial generalized linear models. We found that AIV prevalence was negatively associated with distance to the closest water body in the Red River Delta, Vietnam highlands and Madagascar. We also found a positive association between AIV and duck density in the Vietnam highlands and Thailand, and with rice landscapes in Thailand and Madagascar. Our findings confirm the important role of wetlands-rice-ducks ecosystems in the epidemiology of AI in diverse settings. Variables influencing circulation of the H5 subtype in Southeast Asia played a similar role for low pathogenic AIV in Madagascar, indicating that this area may be at risk if a highly virulent strain is introduced. PMID:25029441

  13. Delta III—an evolutionary delta growth

    NASA Astrophysics Data System (ADS)

    Arvesen, R. J.; Simpson, J. S.

    1996-03-01

    In order to remain competitive in the future and expand the McDonnell Douglas Aerospace market share, MDA has developed an expendable launch system strategy that devices cost-effective launch systems from the Delta II with a growth vehicle configuration called Delta III. The Delta III evolves from the Delta II launch system through development of a larger payload fairing (4-meter diameter), new cryogenically propelled upper stage, new first stage fuel tank, and larger strap-on solid rocket motors. We are developing the Delta III using Integrated Product Development Teams that capitalize on the experience base that has led us to a world record breaking mission success of 49 consecutive Delta II missions. The Delta III first-launch capability is currently planned for the spring of 1998 in support of our first spacecraft customer, Hughes Space and Communications International.

  14. Stratigraphy and Holocene evolution of the mud-dominated Chao Phraya delta, Thailand

    NASA Astrophysics Data System (ADS)

    Tanabe, Susumu; Saito, Yoshiki; Sato, Yoshio; Suzuki, Yuichiro; Sinsakul, Sin; Tiyapairach, Suwat; Chaimanee, Niran

    2003-04-01

    The central plain of Thailand was formed over the last 8-7 kyr mainly by the deltaic processes of two major rivers, the Chao Phraya and the Mae Klong. The delta plain is the third largest delta plain in Southeast Asia after that of the Mekong and the Irrawaddy. On the basis of sedimentological and paleontological analyses of samples from three boreholes and an open-pit survey, the evolution of the delta was clarified with high-resolution 14C dating. After the maximum transgression at between 8 and 7 cal kyr BP, the delta system migrated southward into the paleo-Gulf of Ayutthaya. A large mud shoal (the Sananivate Mud Shoal) formed near the mouth of the paleo-gulf between 7 and 3 cal kyr BP and facilitated its infilling. As a result, the delta has prograded rapidly particularly during the last 2 kyr. Deltaic sediment volume for the last 7.5±0.5 kyr shows that the average rate of sedimentation was 23.1±3.6 million t/yr, which is nearly the same as the present total sediment discharge from both rivers. The comparatively wide delta plain relative to sediment discharge resulted from the stable sea level, the shallow paleo-gulf acting as a receiving basin, and effective sediment trapping because of the mud shoal.

  15. Neurology in the Vietnam War.

    PubMed

    Gunderson, Carl H; Daroff, Robert B

    2016-01-01

    Between December 1965 and December 1971, the United States maintained armed forces in Vietnam never less than 180,000 men and women in support of the war. At one time, this commitment exceeded half a million soldiers, sailors, and airmen from both the United States and its allies. Such forces required an extensive medical presence, including 19 neurologists. All but two of the neurologists had been drafted for a 2-year tour of duty after deferment for residency training. They were assigned to Vietnam for one of those 2 years in two Army Medical Units and one Air Force facility providing neurological care for American and allied forces, as well as many civilians. Their practice included exposure to unfamiliar disorders including cerebral malaria, Japanese B encephalitis, sleep deprivation seizures, and toxic encephalitis caused by injection or inhalation of C-4 explosive. They and neurologists at facilities in the United States published studies on all of these entities both during and after the war. These publications spawned the Defense and Veterans Head Injury Study, which was conceived during the Korean War and continues today as the Defense and Veterans Head Injury Center. It initially focused on post-traumatic epilepsy and later on all effects of brain injury. The Agent Orange controversy arose after the war; during the war, it was not perceived as a threat by medical personnel. Although soldiers in previous wars had developed serious psychological impairments, post-traumatic stress disorder was formally recognized in the servicemen returning from Vietnam. PMID:27035455

  16. AB035. Thalassemia in Vietnam

    PubMed Central

    Nguyen, Hoang Nam

    2015-01-01

    Thalassemia is a common inherited hemoglobin disorder in Vietnam. The alpha thalassemia, beta thalassemia, and HbE are popular in Vietnam but its variance depends on ethnics. The research for frequency of some ethnics almost in electrophoresis includes: Kinh (beta thalassemia carrier 1.49%, HbE 1.24%), Muong (beta thalassemia carrier 10.7%, HbE 11.7%), Tay (beta thalassemia carrier 11%, HbE 1%). In the recent years, we have conducted researches on thalassemia gene in the Northern and Southern areas of Vietnam. The two researches on beta thalassemia conducted at National Hospital of Pediatrics were Cd17 (33.8%), Cd41/42 (29.4%) following are HbE (19.1%), Cd 71/72 (7.3%), -28 (5.9%), IVS 2-625 (1.5%), IVS 1-5 (1.5%), IVS 1-1 (1.5%). In Vietnam, we have a thalassemia centre at the National Institute of Hematology and Blood Transfusion and several outpatient clinics at National Hospital of Pediatrics, Children No. 1 Hospital, Blood Transfusion and Hematology Hospital Ho Chi Minh city, Central Hue Hospital. In provincial hospitals, we have transfusion service but very variance. That the number of patients with thalassemia requires regular blood transfusion has been increasing results in big shortage of blood supply. At Department of Clinical Hematology-NHP, we provide patients with screening for HIV, HCV and HBV in every 6 months. Patients were done antibody screening test. Deferoxamine, deferiprone and deferasirox are currently used but in short supply. We are facing the difficulty that almost hospitals in Vietnam lack the drug which is unique for each type of chelation. We have to apply ferritin level to follow the chelation effective and MRI to measure iron overload in patients’ liver and heart. We are only able to provide SCT for the modest number of patients with thalassemia. In almost cases, we used sibling donor in SCT for patients with thalassemia. Regarding prevention service, we offer genetic counseling and prenatal diagnosis at three hospitals. We organized

  17. An Analysis of Historical Impacts of Water Resources Development on Water Levels of the Mekong River (Invited)

    NASA Astrophysics Data System (ADS)

    Cochrane, T. A.; Arias, M. E.; Piman, T.

    2013-12-01

    The rapid rate of water resources development in the Mekong basin of Southeast Asia is a cause for concern due to potential impacts on highly valued fisheries and natural ecosystems. Historical water levels of the Mekong were analyzed by comparing pre and post 1991 daily data of 6 stations along the mainstream from Chiang Sean, in northern Lao PDR and Thailand, to Stung Treng, in Cambodia, and the Pre Kdam station near the Tonle Sap Lake in the lower Mekong floodplain using the Indicators of Hydrological Alteration (IHA) software. The year 1991 marks a turning point in the rate of development in the basin, with the start of development of mainstream dams in the upper Mekong and accelerated hydropower and irrigation development in key tributaries. Observed changes in water level patterns along the Mekong were linked to temporal and spatial water resources development from 1960 to 2010. Variations in climate were accounted for and are important, but they were not observed to be the main causes of changes in key hydrological indicators related to ecosystem productivity. The development of mainstream dams in the upper Mekong basin in the post 1991 period resulted in a significant change of seasonal water levels, raise rates, fall rates, and the number of water level fluctuations at Chiang Sean. This effect diminishes downstream until it becomes negligible at the Mukdahan monitoring station in Thailand, which represents a drainage area of over 50% of the total Mekong Basin. Further downstream at Pakse station in Southern Lao PDR, changes in hydrological indicators post 1991 were observed to be significant again, which can be directly attributed to water resource development in the Chi and Mun River basins in Northeastern Thailand. A reduction of 23% and 11% in water level raising rates and fall rates, respectively at Prek Kdam, provides clear evidence of a diminished flood pulse of the Tonle Sap Lake in the post 1991 period. Given the observed water level alterations

  18. "Achilles in Vietnam" and the Humanities Classroom.

    ERIC Educational Resources Information Center

    Walter, James A.

    This paper discusses the book "Achilles in Vietnam" (Jonathan Shay) in relation to Homer's "Iliad" and the need for society to accept the consequences of veterans' experiences. Classical allusions to the epic are incorporated into the study and U.S. experience of the Vietnam War. The paper advocates student "ownership" of literature study and…

  19. Educational Reform and Teacher Education in Vietnam

    ERIC Educational Resources Information Center

    Hamano, Takashi

    2008-01-01

    This paper examines the current state and a challenge faced by teachers and teacher education in Vietnam, and analyzes international aid projects providing support to teacher education there. It is necessary to grasp changes in teacher education in Vietnam in the context of the current comprehensive reform of education, which has been greatly…

  20. Interpersonal Styles of Vietnam Era Veterans

    ERIC Educational Resources Information Center

    Lorr, Maurice; And Others

    1975-01-01

    A comparative analysis is made of the social characteristics of Vietnam veterans and World War II veterans. By use of the Interpersonal Style Inventory, the results showed that the Vietnam veterans were more rebellious, radical, and expedient than older veterans. (DEP)

  1. Economic aspects of chronic diseases in Vietnam

    PubMed Central

    Van Minh, Hoang; Lan Huong, Dao; Bao Giang, Kim; Byass, Peter

    2009-01-01

    Introduction There remains a lack of information on economic aspects of chronic diseases. This paper, by gathering available and relevant research findings, aims to report and discuss current evidence on economic aspects of chronic diseases in Vietnam. Methods Data used in this paper were obtained from various information sources: international and national journal articles and studies, government documents and publications, web-based statistics and fact sheets. Results In Vietnam, chronic diseases were shown to be leading causes of deaths, accounting for 66% of all deaths in 2002. The burdens caused by chronic disease morbidity and risk factors are also substantial. Poorer people in Vietnam are more vulnerable to chronic diseases and their risk factors, other than being overweight. The estimated economic loss caused by chronic diseases for Vietnam in 2005 was about US$20 million (0.033% of annual national GDP). Chronic diseases were also shown to cause economic losses for families and individuals in Vietnam. Both population-wide and high-risk individual interventions against chronic disease were shown to be cost-effective in Vietnam. Conclusion Given the evidence from this study, actions to prevent chronic diseases in Vietnam are clearly urgent. Further research findings are required to give greater insights into economic aspects of chronic diseases in Vietnam. PMID:20057939

  2. 77 FR 20273 - Vietnam Veterans Day

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-04-03

    ... thirty-sixth. (Presidential Sig.) [FR Doc. 2012-8162 Filed 4-2-12; 11:15 am] Billing code 3295-F2-P ... April 3, 2012 Part IV The President Proclamation 8789--Vietnam Veterans Day Memorandum of March 30, 2012... ] Proclamation 8789 of March 29, 2012 Vietnam Veterans Day By the President of the United States of America...

  3. Vietnam: The Political Economy of Education in a "Socialist" Periphery

    ERIC Educational Resources Information Center

    London, Jonathan D.

    2006-01-01

    In this article I examine historic changes in the goals, conduct and outcomes of education policies in Vietnam from the 1940s to the present, under the Communist Party of Vietnam. Recent studies of Vietnam's education system centre on econometric and demographic analysis of education data dating back to the early 1990s, when Vietnam began an…

  4. delta-Hexachlorocyclohexane (delta-HCH)

    Integrated Risk Information System (IRIS)

    delta - Hexachlorocyclohexane ( delta - HCH ) ; CASRN 319 - 86 - 8 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Ass

  5. Fish Migration, Dams, and Loss of Ecosystem Services in the Mekong Basin

    SciTech Connect

    Dugan, Patrick J.; Barlow, Chris; Agostinho, Angelo A.; Baran, Eric; Cada, Glenn F; Chen, Daqing; Cowx, Ian G.; Ferguson, John W.; Jutagate, Tuantong; Mallen-Cooper, Martin; Marmulla, Gerd; Nestler, John; Petrere, Miquel; Winemiller, Kirk O.

    2010-06-01

    The past decade has seen increased international recognition of the importance of the services provided by natural ecosystems. It is unclear however whether such international awareness will lead to improved environmental management in many regions. We explore this issue by examining the specific case of fish migration and dams on the Mekong river. We determine that dams on the Mekong mainstem and major tributaries will have a major impact on the basin's fisheries and the people who depend upon them for food and income. We find no evidence that current moves towards dam construction will stop, and consider two scenarios for the future of the fisheries and other ecosystems of the basin. We conclude that major investment is required in innovative technology to reduce the loss of ecosystem services, and alternative livelihood strategies to cope with the losses that do occur

  6. Rising flux of nutrients (C, N, P and Si) in the lower Mekong River

    NASA Astrophysics Data System (ADS)

    Li, Siyue; Bush, Richard T.

    2015-11-01

    Changing human land use is accelerating global element cycling and appreciably altering ecosystems in the riverine-estuarine systems. This is evident by dramatic shifts in the supply of nutrients (C, N, P, Si). However, very little is known about the magnitude and rates of these changes. We examine the Mekong, one of the world largest rivers, to assess on a whole-of-system scale, the spatial, monthly and inter-annual flux of nutrients and stoichiometric ratios using a huge data-set (1985-2011). Seasonal and spatial patterns are apparent and linked to hydrology. The estimated mean flux (×109 mol/y) of elements from the Mekong at Pakse are 414.5 for DIC, 4.1 for DIN (3.3 for NO3--N and 0.8 for NH4+-N), 10.2 for TN, 0.32 for DIP, 0.46 for TP and 62.8 for DSi, respectively, which are intermediate relative to other large rivers. However, compared to the river reach at Pakse, the total river fluxes are two-fold greater for C, N, P and DSi. Annual flux increases significantly for DIC, NO3--N, DIN, TN and DSi, and is especially pronounced for all N and P species during the recent decade (1998 onward). Distinct shifts of nutrient stoichiometry, with far-reaching changes for phytoplankton productivity in the Mekong estuary are also evident, as the system shifts from potentially N limited to P limited. These notable changes to the exports and ratios of nutrient variables and anthropogenically-driven nutrient concerns are becoming a defining feature of the Mekong Plume to the South China Sea.

  7. What do the occurrences of migratory fishes in the Upper Mekong mean?

    PubMed

    Kang, Bin

    2013-11-01

    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. PMID:23828312

  8. Early childhood survivorship in Vietnam.

    PubMed

    Swenson, I E; Thang, N M; San, P B; Nhan, V Q; Man, V D

    1995-06-01

    The effects on early childhood mortality of birth order, age of the mother at the time of the child's birth, mother's education, as well as infant mortality risk in the province, urban/rural residence, the presence of schools and other facilities and health care services, were examined using data from the 1988 Vietnam Demographic and Health Survey and the 1990 Study of Accessibility of Contraceptives in Vietnam. A total of 4137 urban and rural children born between 1983 and 1988 to the 4172 women interviewed in the Demographic and Health Survey were included in the hazard model analysis of maternal and child characteristics. However, since the Accessibility of Contraceptives Study included only rural respondents, the hazard model analysis of community development characteristics and health services effects on early childhood mortality was based on a subsample of 3314 rural children. Rural children in birth orders five and higher had the greatest risk of early childhood death, birth order one an intermediate risk and orders 2-4 the lowest risk of early childhood death. Rural children residing in communes with fewer than 10,000 inhabitants were at significantly greater risk of early childhood death than children from larger communes. Neither age nor education of the mother nor gender of the child, had a significant impact on early childhood survivorship independent of other variables. Risk of infant mortality in the child's province was of borderline significance. PMID:7783281

  9. Investigations of the effect of guava as a possible tool in the control/management of Huanglongbing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The farmers of the Mekong Delta of Vietnam have discovered a unique interaction between citrus and guava, Psidium guajava L., that extends the commercial life of citrus plantings plagued by huanglongbing (HLB). Due to HLB, the normal life of citrus plantings in the region is 2-4 years. However, wh...

  10. Agricultural Biotechnology: From the lab to the market place. Partnership between FAS and ARS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Dr. VanToai is a Plant Physiologist and the Lead Scientist for plant flooding tolerance research at the Soil Drainage Research Unit in Columbus, Ohio. A native of Vietnam, Dr. VanToai grew up in the Mekong Delta, where the land was fertile and the water plentiful, yet many farmers faced life-long po...

  11. Synergistic Utilization of Microwave Satellite Data and GRACE-Total Water Storage Anomaly for Improving Available Water Capacity Prediction in Lower Mekong Basin

    NASA Astrophysics Data System (ADS)

    Gupta, M.; Bolten, J. D.; Lakshmi, V.

    2015-12-01

    The Mekong River is the longest river in Southeast Asia and the world's eighth largest in discharge with draining an area of 795,000 km² from the eastern watershed of the Tibetan Plateau to the Mekong Delta including three provinces of China, Myanmar, Lao PDR, Thailand, Cambodia and Viet Nam. This makes the life of people highly vulnerable to availability of the water resources as soil moisture is one of the major fundamental variables in global hydrological cycles. The day-to-day variability in soil moisture on field to global scales is an important quantity for early warning systems for events like flooding and drought. In addition to the extreme situations the accurate soil moisture retrieval are important for agricultural irrigation scheduling and water resource management. The present study proposes a method to determine the effective soil hydraulic parameters directly from information available for the soil moisture state from the recently launched SMAP (L-band) microwave remote sensing observations. Since the optimized parameters are based on the near surface soil moisture information, further constraints are applied during the numerical simulation through the assimilation of GRACE Total Water Storage (TWS) within the physically based land surface model. This work addresses the improvement of available water capacity as the soil hydraulic parameters are optimized through the utilization of satellite-retrieved near surface soil moisture. The initial ranges of soil hydraulic parameters are taken in correspondence with the values available from the literature based on FAO. The optimization process is divided into two steps: the state variable are optimized and the optimal parameter values are then transferred for retrieving soil moisture and streamflow. A homogeneous soil system is considered as the soil moisture from sensors such as AMSR-E/SMAP can only be retrieved for the top few centimeters of soil. To evaluate the performance of the system in helping

  12. Education and Science in North Vietnam

    ERIC Educational Resources Information Center

    Galston, Arthur W.; Signer, Ethan

    1971-01-01

    Describes the organization of education, particulary higher education, and medical and scientific research in North Vietnam. Description is based on experiences during a lecture tour as well as available literature. (AL)

  13. Effects of Upstream Human Changes on Nutrient Fluxes to Major Deltas World-Wide

    NASA Astrophysics Data System (ADS)

    Van Cappellen, P.; Dürr, H. H.; Maavara, T.

    2015-12-01

    Major deltas world-wide are connected to large river systems, and while they make up <1% of the shoreline, they are at the receiving end of 25-42% of all discharge, suspended sediment load and nutrient load. Thus, in addition to the pressure from human impact in the deltas, changes far upstream are tightly linked to effects downstream. The Global-NEWS approach has explored scenarios along storylines that influence future nutrient fluxes, and if highlighted for individual delta, reveals large differences in future change, with most of the influence being attributed to factors such as land use change or increased damming. Notably the latter factor has received recent attention with regards to nutrient fluxes, and phosphorus (P) in particular (Maavara et al. in review): the largest increases in P retention by reservoirs, between 2000 and 2030, are expected to occur in the Yangtze, Mekong, Amazon and Ganges-Brahmaputra river basins. Here, we discuss how Global-NEWS and other approaches assess these future changes in nutrient fluxes, and how the expected new boom in dam construction can influence these fluxes to deltas world-wide.

  14. Changing fluxes of carbon and other solutes from the Mekong River

    PubMed Central

    Li, Siyue; Bush, Richard T.

    2015-01-01

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world’s largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923–2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO42−, Cl− and Na+. The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3− (23.4) > Ca2+ (6.4) > SO42− (3.8) > Cl− (1.74)~Na+ (1.7) ~ Si (1.67) > Mg2+ (1.2) > K+ (0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3− and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3− flux (Himalayan Rivers included) is 34014 × 109 mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3−, and 13553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling. PMID:26522820

  15. Changing fluxes of carbon and other solutes from the Mekong River.

    PubMed

    Li, Siyue; Bush, Richard T

    2015-01-01

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world's largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923-2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO4(2-), Cl(-) and Na(+). The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3(-) (23.4) > Ca(2+) (6.4) > SO4(2-) (3.8) > Cl(-) (1.74)~Na(+) (1.7) ~ Si (1.67) > Mg(2+) (1.2) > K(+ 0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3(-) and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3(-) flux (Himalayan Rivers included) is 34,014 × 10(9) mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3(-), and 13,553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling. PMID:26522820

  16. Changing fluxes of carbon and other solutes from the Mekong River

    NASA Astrophysics Data System (ADS)

    Li, Siyue; Bush, Richard T.

    2015-11-01

    Rivers are an important aquatic conduit that connects terrestrial sources of dissolved inorganic carbon (DIC) and other elements with oceanic reservoirs. The Mekong River, one of the world’s largest rivers, is firstly examined to explore inter-annual fluxes of dissolved and particulate constituents during 1923-2011 and their associated natural or anthropogenic controls. Over this period, inter-annual fluxes of dissolved and particulate constituents decrease, while anthropogenic activities have doubled the relative abundance of SO42-, Cl- and Na+. The estimated fluxes of solutes from the Mekong decrease as follows (Mt/y): TDS (40.4) > HCO3- (23.4) > Ca2+ (6.4) > SO42- (3.8) > Cl- (1.74)~Na+ (1.7) ~ Si (1.67) > Mg2+ (1.2) > K+ (0.5). The runoff, land cover and lithological composition significantly contribute to dissolved and particulate yields globally. HCO3- and TDS yields are readily predicted by runoff and percent of carbonate, while TSS yield by runoff and population density. The Himalayan Rivers, including the Mekong, are a disproportionally high contributor to global riverine carbon and other solute budgets, and are of course underlined. The estimated global riverine HCO3- flux (Himalayan Rivers included) is 34014 × 109 mol/y (0.41 Pg C/y), 3915 Mt/y for solute load, including HCO3-, and 13553 Mt/y for TSS. Thereby this study illustrates the importance of riverine solute delivery in global carbon cycling.

  17. Characteristics of bedrock-alluvial anastomosed rivers: the Mekong River in Cambodia

    NASA Astrophysics Data System (ADS)

    Meshkova, Liubov. V.; Carling, Paul. A.

    2010-05-01

    The Mekong River is the 12th largest river in the world in terms of its length and mean annual discharge and yet it is poorly investigated. In the north eastern regions of Cambodia the Mekong River develops a multichannel pattern. It is characterised by a complex of intersecting bedrock channels, well vegetated alluvial and seasonally inundated islands, various types of sand bars, numerous bedrock exposures, rapids, waterfalls and deep bedrock pools which can be classified as a large mixed bedrock-alluvial anastomosed river of a tropical monsoonal climate zone. In order to complete a portrait of the river at the high level of details new data on morphology, geology and sediments were obtained during field surveys of a 120 km river section in Cambodia and combined with information from published literature and interpretation of available remote sensing images. This process has enabled to update and clarify knowledge on morphology of observed islands and floodplain, comprehensive geology and tectonic structures, hydrological regime and land cover. Complex analyses of the collected data have distinguished several geomorphological zones accordingly to frequency of morphological elements, the planview configuration of channels and vertical profile characteristics. The occurrence of each zone is a subject of variable controlling factors such as local topography, channel gradient, structural and tectonic elements and intercalating geological units. Evolution of the channel pattern has been considered at both short- and long term time scales. Historical cartographic and remote sensing materials were applied to determine planform channel changes over the last 50 years revealing the channels stability and cases of occasional, local erosion and deposition. The channel network was extracted from vector layers to examine channels and islands width and length parameters, bifurcation angles at the upstream end of islands and to obtain main channel network indices such as braiding

  18. 45 CFR 506.10 - “Vietnam conflict” defined.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 45 Public Welfare 3 2010-10-01 2010-10-01 false âVietnam conflictâ defined. 506.10 Section 506.10... § 506.10 “Vietnam conflict” defined. Vietnam conflict refers to the period beginning February 28, 1961... proclaimed the date of May 7, 1975, to be the ending date of the “Vietnam era” (Presidential Proclamation...

  19. 45 CFR 506.10 - “Vietnam conflict” defined.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 45 Public Welfare 3 2013-10-01 2013-10-01 false âVietnam conflictâ defined. 506.10 Section 506.10... § 506.10 “Vietnam conflict” defined. Vietnam conflict refers to the period beginning February 28, 1961... proclaimed the date of May 7, 1975, to be the ending date of the “Vietnam era” (Presidential Proclamation...

  20. 45 CFR 506.10 - “Vietnam conflict” defined.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 45 Public Welfare 3 2012-10-01 2012-10-01 false âVietnam conflictâ defined. 506.10 Section 506.10... § 506.10 “Vietnam conflict” defined. Vietnam conflict refers to the period beginning February 28, 1961... proclaimed the date of May 7, 1975, to be the ending date of the “Vietnam era” (Presidential Proclamation...

  1. 45 CFR 506.10 - “Vietnam conflict” defined.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 45 Public Welfare 3 2014-10-01 2014-10-01 false âVietnam conflictâ defined. 506.10 Section 506.10... § 506.10 “Vietnam conflict” defined. Vietnam conflict refers to the period beginning February 28, 1961... proclaimed the date of May 7, 1975, to be the ending date of the “Vietnam era” (Presidential Proclamation...

  2. Pen Branch delta expansion

    SciTech Connect

    Nelson, E.A.; Christensen, E.J.; Mackey, H.E.; Sharitz, R.R.; Jensen, J.R.; Hodgson, M.E.

    1984-02-01

    Since 1954, cooling water discharges from K Reactor ({anti X} = 370 cfs {at} 59 C) to Pen Branch have altered vegetation and deposited sediment in the Savannah River Swamp forming the Pen Branch delta. Currently, the delta covers over 300 acres and continues to expand at a rate of about 16 acres/yr. Examination of delta expansion can provide important information on environmental impacts to wetlands exposed to elevated temperature and flow conditions. To assess the current status and predict future expansion of the Pen Branch delta, historic aerial photographs were analyzed using both basic photo interpretation and computer techniques to provide the following information: (1) past and current expansion rates; (2) location and changes of impacted areas; (3) total acreage presently affected. Delta acreage changes were then compared to historic reactor discharge temperature and flow data to see if expansion rate variations could be related to reactor operations.

  3. Drawing on Experience: A Study of Vietnam Veteran Artists

    ERIC Educational Resources Information Center

    Michel, Karl F.

    2004-01-01

    This study is an exploration of the art produced by American veterans of the Vietnam War. In the areas of artistic history, military service, and the creative process, Vietnam veteran artists are a diverse group, and there are many different ways of explaining the connection between Vietnam experience and their art. Some individuals made limited…

  4. The Determinants and Impact of Private Tutoring Classes in Vietnam

    ERIC Educational Resources Information Center

    Dang, Hai-Anh

    2007-01-01

    Private tutoring is a widespread phenomenon in many developing countries, including Vietnam. Using the Vietnam Living Standards Surveys 1997-1998 and 1992-1993 for analysis, this paper finds evidence that private tutoring in Vietnam is a necessity in the household budget for both primary students and lower secondary students, and the trend to…

  5. Teaching the Vietnam Experience as a Whole Course.

    ERIC Educational Resources Information Center

    Pike, Douglas

    1985-01-01

    Since the end of the Vietnam War there has been a flood of new historical information vastly revising much of what anyone--left, right, or center--knew. Teachers must take this into account when teaching about Vietnam. All major competing perceptions of the Vietnam war should be analyzed objectively. (RM)

  6. 45 CFR 506.10 - “Vietnam conflict” defined.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 45 Public Welfare 3 2011-10-01 2011-10-01 false âVietnam conflictâ defined. 506.10 Section 506.10 Public Welfare Regulations Relating to Public Welfare (Continued) FOREIGN CLAIMS SETTLEMENT COMMISSION OF... § 506.10 “Vietnam conflict” defined. Vietnam conflict refers to the period beginning February 28,...

  7. Postservice mortality among Vietnam veterans. The Centers for Disease Control Vietnam Experience Study.

    PubMed

    1987-02-13

    The postservice mortality (through December 1983) of a cohort of 9324 US Army veterans who served in Vietnam was compared with that of 8989 Vietnam-era Army veterans who served in Korea, Germany, or the United States. Over the entire follow-up period, total mortality in Vietnam veterans was 17% higher than for other veterans. The excess mortality occurred mainly in the first five years after discharge from active duty (rate ratio, 1.45; 95% confidence interval, 1.08 to 1.96) and involved motor vehicle accidents, suicide, homicide, and accidental poisonings. Thereafter, mortality among Vietnam veterans was similar to that of other Vietnam-era veterans, except for drug-related deaths, which continued to be elevated. An unexpected finding was a deficit in deaths from diseases of the circulatory system among Vietnam veterans. The excess in postservice mortality due to external causes among Vietnam veterans is similar to that found among men returning from combat areas after World War II and the Korean War. PMID:3027422

  8. Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap Floodplain in Cambodia

    NASA Astrophysics Data System (ADS)

    Arias, M. E.; Piman, T.; Lauri, H.; Cochrane, T. A.; Kummu, M.

    2014-02-01

    River tributaries have a key role in the biophysical functioning of the Mekong Basin. Of particular attention are the Sesan, Srepok, and Sekong (3S) rivers, which contribute nearly a quarter of the total Mekong discharge. Forty two dams are proposed in the 3S, and once completed they will exceed the active storage of China's large dam cascade in the upper Mekong. Given their proximity to the lower Mekong floodplains, the 3S dams could alter the flood-pulse hydrology driving the productivity of downstream ecosystems. Therefore, the main objective of this study was to quantify how hydropower development in the 3S would alter the hydrology of the Tonle Sap floodplain, the largest wetland in the Mekong and home to one of the most productive inland fisheries in the world. We coupled results from four numerical models representing the basin's surface hydrology, water resources development, and floodplain hydrodynamics. The scale of alterations caused by hydropower in the 3S was compared with the basin's definite future development scenario (DF) driven by the upper Mekong dam cascade. The DF or the 3S development scenarios could independently increase Tonle Sap's 30 day minimum water levels by 30 ± 5 cm and decrease annual water level fall rates by 0.30 ± 0.05 cm d-2. When analyzed together (DF + 3S), these scenarios are likely to eliminate all baseline conditions (1986-2000) of extreme low water levels, a particularly important component of Tonle Sap's environmental flows. Given the ongoing trends and large economic incentives in the hydropower business in the region, there is a high possibility that most of the 3S hydropower potential will actually be exploited and that dams would be built even in locations where there is a high risk of ecological disruptions. Hence, retrofitting current designs and operations to promote sustainable hydropower practices that optimize multiple river services - rather than just maximize hydropower generation - appear to be the most

  9. Dams on Mekong tributaries as significant contributors of hydrological alterations to the Tonle Sap Floodplain in Cambodia

    NASA Astrophysics Data System (ADS)

    Arias, M. E.; Piman, T.; Lauri, H.; Cochrane, T. A.; Kummu, M.

    2014-12-01

    River tributaries have a key role in the biophysical functioning of the Mekong Basin. Of particular interest are the Sesan, Srepok, and Sekong (3S) rivers, which contribute nearly a quarter of the total Mekong discharge. Forty two dams are proposed in the 3S, and once completed they will exceed the active storage of China's large dam cascade in the Upper Mekong. Given their proximity to the Lower Mekong floodplains, the 3S dams could alter the flood-pulse hydrology driving the productivity of downstream ecosystems. Therefore, the main objective of this study was to quantify how hydropower development in the 3S, together with definite future (DF) plans for infrastructure development through the basin, would alter the hydrology of the Tonle Sap's Floodplain, the largest wetland in the Mekong and home to one of the most productive inland fisheries in the world. We coupled results from four numerical models representing the basin's surface hydrology, water resources development, and floodplain hydrodynamics. The scale of alterations caused by hydropower in the 3S was compared with the basin's DF scenario driven by the Upper Mekong dam cascade. The DF or the 3S development scenarios could independently increase Tonle Sap's 30-day minimum water levels by 30 ± 5 cm and decrease annual water level fall rates by 0.30 ± 0.05 cm day-1. When analyzed together (DF + 3S), these scenarios are likely to eliminate all baseline conditions (1986-2000) of extreme low water levels, a particularly important component of Tonle Sap's environmental flows. Given the ongoing trends and large economic incentives in the hydropower business in the region, there is a high possibility that most of the 3S hydropower potential will be exploited and that dams will be built even in locations where there is a high risk of ecological disruption. Hence, retrofitting current designs and operations to promote sustainable hydropower practices that optimize multiple river services - rather than just

  10. Post Vietnam syndrome: neurosis or sociosis?

    PubMed

    Fleming, R H

    1985-05-01

    Recently released figures from the Veterans Administration on the number of Vietnam veterans who have been granted service connection in their claims for post-traumatic stress disorder appear to be astonishingly low, given the publicity that the media and mental health professionals have placed on this diagnosis in recent years. As of the summer of 1984, only slightly more than 7,000 Vietnam veteran cases had been approved by VA rating boards. A conservative popular estimate is that half a million Vietnam veterans are alleged to suffer from this neurosis, which is largely attributable to combat-related experiences. This gross discrepancy raises many serious questions about the appropriate use of the clinical diagnosis of post-traumatic stress disorder. The point of contention is not the legitimacy of the diagnosis, but the abuse and misuse of the term for personal or political purposes to explain the dilemma of the Vietnam veteran in contemporary America. The traditional psychodynamic content of clinical psychology needs to be integrated with an analysis of the impact of social, political, historical, economic, and philosophical forces on individual and group dynamics. The objective of this paper is to examine those forces, the social and historical conditions in particular, which have contributed to the origin, development, and prolongation of readjustment difficulties for Vietnam veterans. PMID:3991821

  11. New records of marine algae in Vietnam

    NASA Astrophysics Data System (ADS)

    Le Hau, Nhu; Ly, Bui Minh; Van Huynh, Tran; Trung, Vo Thanh

    2015-06-01

    In May, 2013, a scientific expedition was organized by the Vietnam Academy of Science and Technology (VAST) and the Far Eastern Branch of the Russian Academy of Sciences (FEBRAS) through the frame of the VAST-FEBRAS International Collaboration Program. The expedition went along the coast of Vietnam from Quang Ninh to Kien Giang. The objective was to collect natural resources to investigate the biological and biochemical diversity of the territorial waters of Vietnam. Among the collected algae, six taxa are new records for the Vietnam algal flora. They are the red algae Titanophora pikeana (Dickie) Feldmann from Cu Lao Xanh Island, Laurencia natalensis Kylin from Tho Chu Island, Coelothrix irregularis (Harvey) Børgesen from Con Dao Island, the green algae Caulerpa oligophylla Montagne, Caulerpa andamanensis (W.R. Taylor) Draisma, Prudhomme et Sauvage from Phu Quy Island, and Caulerpa falcifolia Harvey & Bailey from Ly Son Island. The seaweed flora of Vietnam now counts 833 marine algal taxa, including 415 Rhodophyta, 147 Phaeophyceae, 183 Chlorophyta, and 88 Cyanobacteria.

  12. Vietnam's campaign to reduce population growth.

    PubMed

    Haub, C

    1999-10-01

    This paper reports campaigns to reduce the population growth in Vietnam. In July, red banners flew above the broad boulevard in Hanoi proclaiming World Population Day. This widespread public attention to population issues is not surprising, given the country's sharp reduction in fertility and widespread citizen support for smaller families. Since 1961, Vietnam has been trying to formulate a policy to reduce the population rate growth. The policy was a reaction to the results of the 1960 Census of the Democratic Republic of Vietnam and reflected long-standing concerns over food shortages, as well as a desire to improve women's health and welfare. After the reunification in 1975, the policy was extended to the entire country. Since then, Vietnam's growth rate has been declining, suggesting that the national campaign for smaller families is succeeding in changing deeply held attitudes and perceptions, in addition to current practices. While the fertility decline in Vietnam may not be the world's fastest, the success of the national population policy has forever altered the country's prospect for population growth. PMID:12295331

  13. Snow Cover and Precipitation Impacts on Dry Season Streamflow in the Lower Mekong Basin

    NASA Technical Reports Server (NTRS)

    Cook, Benjamin I.; Bell, A. R.; Anchukaitis, K. J.; Buckley, B. M.

    2012-01-01

    Climate change impacts on dry season streamflow in the Mekong River are relatively understudied, despite the fact that water availability during this time is critically important for agricultural and ecological systems. Analyses of two gauging stations (Vientiane and Kratie) in the Lower Mekong Basin (LMB) show significant positive correlations between dry season (March through May, MAM) discharge and upper basin snow cover and local precipitation. Using snow cover, precipitation, and upstream discharge as predictors, we develop skillful regression models for MAM streamflow at Vientiane and Kratie, and force these models with output from a suite of general circulation model (GCM) experiments for the twentieth and twenty-first centuries. The GCM simulations predict divergent trends in snow cover (decreasing) and precipitation (increasing) over the twenty-first century, driving overall negligible long-term trends in dry season streamflow. Our study demonstrates how future changes in dry season streamflow in the LMB will depend on changes in snow cover and precipitation, factors that will need to be considered when assessing the full basin response to other climatic and non-climatic drivers.

  14. The Lessons of the Vietnam War: Unit 13. Teacher's Manual: Strategies and Resources for Teaching the Vietnam War.

    ERIC Educational Resources Information Center

    Center for Social Studies Education, Pittsburgh, PA.

    This teacher's manual is designed to accompany the curriculum "The Lessons of the Vietnam War." For each of 12 units of the curriculum, this manual suggests projects for student research and classroom activities. The 12 units are entitled: (1) Introduction to Vietnam: land, history and culture; (2) America at war in Vietnam: decisions and…

  15. 39Ar groundwater dating of a coastal aquifer in the Nam Dinh Province, Vietnam

    NASA Astrophysics Data System (ADS)

    Gerber, Christoph; Purtschert, Roland; Larsen, Flemming; Hoang, Hoan V.; Tran, Long V.; Tran, Luu T.; Pham, Nhan Q.; Sültenfuss, Jürgen

    2013-04-01

    In the south of Nam Dinh Province, Red River Delta, Vietnam, fresh Pleistocene groundwater has been identified to exist next to brackish pore waters in the Red River area (WAGNER et al. 2011). Extensive exploitation of the fresh water results in decreasing groundwater heads and migration of brackish water towards the freshwater (WAGNER et al., 2012). In order to understand the dynamics and origin of the fresh and saltwater and to predict the future evolution of the resource an extensive investigation using environmental tracers has been carried out. 39Ar, 85Kr, 3H/3He and stable noble gas measurements have been used for groundwater dating. Stable isotopes and other geochemical parameters (stable isotopes of the water molecule, water chemistry and gas composition) provide crucial information about the genesis of the water. Groundwater ages are modern in the recharge area and increase to > 1000 years towards the coast and northwards based on the 39Ar data (T1-2: 269 years). Depleted stable noble gas concentrations correlate with high concentrations of dissolved methane suggesting degassing due to the high methane partial pressure. Physical modelling of the degassing process (AESCHBACH-HERTIG et al., 2008) supported by concentrations of accumulated radiogenic 4He indicates that diffusion controlled the observed degassing at a late stage of the groundwater evolution path. References Aeschbach-Hertig, W., El-Gamal, H., Wieser, M., Palcsu, L., 2008. Modeling excess air and degassing in groundwater by equilibrium partitioning with a gas phase. Water Resour Res 44:W08449. Wagner, F., Trung, Ð. T., Phúc, H. Ð., Lindenmaier, F., 2011, Assessment of Groundwater Resources in Nam Dinh Province, Final Technical Report, Part A, Improvement of Groundwater Protection in Vietnam. Wagner, F., Ludwig, R. R., Noell, U., Hoang, H. V., Pham, N. Q., Larsen, F., Lindenmaier, F., 2012, Genesis of economic relevant fresh groundwater resources in Pleistocene/Neogene aquifers in Nam Dinh

  16. Delta hepatitis in Malaysia.

    PubMed

    Sinniah, M; Dimitrakakis, M; Tan, D S

    1986-06-01

    Sera from one hundred and fifty nine Malaysian individuals were screened for the prevalence of delta markers. These included 15 HBsAg positive homosexuals, 16 acute hepatitis B cases, 9 chronic hepatitis B patients, 13 healthy HBsAg carriers and 106 intravenous (i.v.) drug abusers, of whom 27 were positive for HBsAg only and the rest were anti-HBc IgG positive but HBsAg negative. The prevalence of delta markers in the homosexuals was found to be 6.7%, in the HBsAg positive drug abusers 17.8%, in acute hepatitis B cases 12.5%. No evidence of delta infection was detected in healthy HBsAg carriers, chronic hepatitis B cases and HBsAg negative i.v. drug abusers. With reference to i.v. drug abusers, the prevalence of delta markers was higher in Malays (23%) than in Chinese (7%) although the latter had a higher HBsAg carrier rate. Although the HBsAg carrier rate in the homosexuals was high, their delta prevalence rate was low as compared to drug abusers. In Malaysia, as in other non-endemic regions, hepatitis delta virus transmission appeared to occur mainly via the parenteral and sexual routes. This is the first time in Malaysia that a reservoir of delta infection has been demonstrated in certain groups of the population at high risk for hepatitis B. PMID:3787309

  17. Delta Scuti stars: Theory

    SciTech Connect

    Guzik, J.A.

    1998-03-01

    The purpose of asteroseismology is not only to derive the internal structure of individual stars from their observed oscillation frequencies, but also to test and extend one`s understanding of the physics of matter under the extremes of temperature, density, and pressure found in stellar interiors. In this review, the author hopes to point out what one can learn about the Sun by studying {delta} Scuti stars, as well as what one can learn about stars more massive or evolved than the Sun. He discusses some of the difficulties in theoretical approaches to asteroseismology for {delta} Scuti stars, using FG Vir, {delta} Scuti, and CD-24{degree} 7599 as examples.

  18. The Delta Clipper dream

    NASA Astrophysics Data System (ADS)

    Furniss, Tim

    1992-04-01

    A conceptual development status evaluation is presented for the SDIO's projected VTOL SSTOV, dubbed the 'Delta Clipper', which is envisioned as an alternative to the slowly developing NASP and the next-generation National Launch System. Delta Clipper program managers believe that the lightweight materials and structures entailed by the requisite empty/gross-weight ratio for an SSTOV are now available, precluding the airbreathing propulsion of such alternatives as HOTOL. The Delta Clipper could operate with a crew of two, or entirely unmanned. The 8-12 LH2/LOX engines employed are derived from the RL-10 engines of the Centaur launcher.

  19. Modeling river delta formation.

    PubMed

    Seybold, Hansjörg; Andrade, José S; Herrmann, Hans J

    2007-10-23

    A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi River. PMID:17940031

  20. Nile River Delta, Egypt

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The Nile River Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population. The capital city of Cairo is at the apex of the delta. Just across the river from Cairo can be seen the ancient three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.

  1. Nile Delta, Egypt

    NASA Technical Reports Server (NTRS)

    1982-01-01

    The Nile Delta of Egypt (30.0N, 31.0E) irrigated by the Nile River and its many distributaries, is some of the richest farm land in the world and home to some 45 million people, over half of Egypt's population of 57 million. The capital city of Cairo is at the apex of the delta in the middle of the scene. Across the river from Cairo can be seen the three big pyramids and sphinx at Giza and the Suez Canal is just to the right of the delta.

  2. Modeling river delta formation

    PubMed Central

    Seybold, Hansjörg; Andrade, José S.; Herrmann, Hans J.

    2007-01-01

    A model to simulate the time evolution of river delta formation process is presented. It is based on the continuity equation for water and sediment flow and a phenomenological sedimentation/erosion law. Different delta types are reproduced by using different parameters and erosion rules. The structures of the calculated patterns are analyzed in space and time and compared with real data patterns. Furthermore, our model is capable of simulating the rich dynamics related to the switching of the mouth of the river delta. The simulation results are then compared with geological records for the Mississippi River. PMID:17940031

  3. Fertility and family planning in Vietnam.

    PubMed

    Allman, J; Vu, Q N; Nguyen, M T; Pham, B S; Vu, D M

    1991-01-01

    This report provides the first reliable statistical data on fertility patterns and the family planning program in the Socialist Republic of Vietnam. Findings are from the 1988 Demographic and Health Survey of Vietnam and the 1989 census survey. The data show that the total fertility rate has declined from over 6 children per woman in the early 1970s to under 4 in the later 1980s. Contraceptive prevalence for modern methods is estimated at 37 percent among married women of reproductive age in 1988. The average duration of breastfeeding is over 14 months; marriage is relatively late. The IUD is the most common contraceptive method and abortion is widespread. The major factors likely to influence fertility and family planning in the future are the government's population policy, improved access to modern methods of contraception, and the institution of new economic policies that are currently under way in Vietnam. PMID:1759276

  4. Current separation and upwelling over the southeast shelf of Vietnam in the South China Sea

    NASA Astrophysics Data System (ADS)

    Chen, Changsheng; Lai, Zhigang; Beardsley, Robert C.; Xu, Qichun; Lin, Huichan; Viet, Nguyen Trung

    2012-03-01

    The high-resolution, unstructured grid Finite-Volume Community Ocean Model (FVCOM) was used to examine the physical mechanisms that cause current separation and upwelling over the southeast shelf of Vietnam in the South China Sea (SCS). Process-oriented experiments suggest that the southwesterly monsoon wind is a key physical mechanism for upwelling in that area but not a prerequisite to cause current separation. With no wind forcing, current separation in summer can occur as a result of the encounter of a southward along-shelf coastal current from the north and northeastward buoyancy-driven and stratified tidal-rectified currents from the southwest. The southward current can be traced upstream to the Hong River in the Gulf of Tonkin. This current is dominated by semigeostrophic dynamics and is mostly confined to the narrow shelf along the northern Vietnamese coast. The northeastward currents are generated by tidal rectification and are intensified by the Mekong River discharge and southwesterly monsoon wind forcing. The dynamics controlling this current are fully nonlinear, with significant contributions from advection and vertical turbulent mixing. Upwelling in the current separation zone can be produced by a spatially uniform constant wind field and can be explained using simple wind-induced Ekman transport theory. This finding differs from previous theory in which the regional dipole wind stress curl is claimed as a key mechanism for current separation and upwelling in this coastal region. Our SCS FVCOM, driven by the wind stress, river discharge, and tides, is capable of reproducing the location and tongue-like offshore distribution of temperature as those seen in satellite-derived sea surface temperature imagery.

  5. Man made deltas.

    PubMed

    Maselli, Vittorio; Trincardi, Fabio

    2013-01-01

    The review of geochronological and historical data documents that the largest southern European deltas formed almost synchronously during two short intervals of enhanced anthropic pressure on landscapes, respectively during the Roman Empire and the Little Ice Age. These growth phases, that occurred under contrasting climatic regimes, were both followed by generalized delta retreat, driven by two markedly different reasons: after the Romans, the fall of the population and new afforestation let soil erosion in river catchments return to natural background levels; since the industrial revolution, instead, flow regulation through river dams overkill a still increasing sediment production in catchment basins. In this second case, furthermore, the effect of a reduced sediment flux to the coasts is amplified by the sinking of modern deltas, due to land subsidence and sea level rise, that hampers delta outbuilding and increases the vulnerability of coastal zone to marine erosion and flooding. PMID:23722597

  6. Man made deltas

    PubMed Central

    Maselli, Vittorio; Trincardi, Fabio

    2013-01-01

    The review of geochronological and historical data documents that the largest southern European deltas formed almost synchronously during two short intervals of enhanced anthropic pressure on landscapes, respectively during the Roman Empire and the Little Ice Age. These growth phases, that occurred under contrasting climatic regimes, were both followed by generalized delta retreat, driven by two markedly different reasons: after the Romans, the fall of the population and new afforestation let soil erosion in river catchments return to natural background levels; since the industrial revolution, instead, flow regulation through river dams overkill a still increasing sediment production in catchment basins. In this second case, furthermore, the effect of a reduced sediment flux to the coasts is amplified by the sinking of modern deltas, due to land subsidence and sea level rise, that hampers delta outbuilding and increases the vulnerability of coastal zone to marine erosion and flooding. PMID:23722597

  7. Neogene sequence stratigraphy, Nam Con Son Basin, offshore Vietnam

    SciTech Connect

    McMillen, K.J. ); Do Van Luu; Lee, E.K.; Hong, S.S. )

    1996-01-01

    An integrated well log, biostratigraphic, and seismic stratigraphic study of Miocene to Recent deltaic sediments deposited in the Nam Con Son Basin offshore from southern Vietnam shows the influence of eustacy and tectonics on sequence development. Sediments consist of Oligocene non-marine rift-basin fill (Cau Formation), early to middle Miocene tide-dominated delta plain to delta front sediments (TB 1.5 to TB 2.5, Due and Thong Formations), and late Miocene to Recent marine shelf sediments (TB. 2.6 to TB 3.1 0, Mang Cau, Nam Con Son, and Bien Dong Formations). Eustacy controlled the timing of key surfaces and sand distribution in the tectonically-quiet early Miocene. Tectonic effects on middle to late Miocene sequence development consist of thick transgressive systems tracts due to basin-wide subsidence and transgression, sand distribution in the basin center, and carbonate sedimentation on isolated fault blocks within the basin. Third-order sequence boundaries (SB) are identified by spore peaks, sand stacking patterns, and channel incision. In the basin center, widespread shale beds with coal occur above sequence boundaries followed by transgressive sandstone units. These TST sandstones merge toward the basin margin where they lie on older HST sandstones. Maximum flooding surfaces (MFS) have abundant marine microfossils and mangrove pollen, a change in sand stacking pattern, and often a strong seismic reflection with downlap. Fourth-order genetic-type sequences are also interpreted. The MFS is the easiest marker to identify and correlate on well logs. Fourth-order SB occur within these genetic units but are harder to identify and correlate.

  8. Neogene sequence stratigraphy, Nam Con Son Basin, offshore Vietnam

    SciTech Connect

    McMillen, K.J.; Do Van Luu; Lee, E.K.; Hong, S.S.

    1996-12-31

    An integrated well log, biostratigraphic, and seismic stratigraphic study of Miocene to Recent deltaic sediments deposited in the Nam Con Son Basin offshore from southern Vietnam shows the influence of eustacy and tectonics on sequence development. Sediments consist of Oligocene non-marine rift-basin fill (Cau Formation), early to middle Miocene tide-dominated delta plain to delta front sediments (TB 1.5 to TB 2.5, Due and Thong Formations), and late Miocene to Recent marine shelf sediments (TB. 2.6 to TB 3.1 0, Mang Cau, Nam Con Son, and Bien Dong Formations). Eustacy controlled the timing of key surfaces and sand distribution in the tectonically-quiet early Miocene. Tectonic effects on middle to late Miocene sequence development consist of thick transgressive systems tracts due to basin-wide subsidence and transgression, sand distribution in the basin center, and carbonate sedimentation on isolated fault blocks within the basin. Third-order sequence boundaries (SB) are identified by spore peaks, sand stacking patterns, and channel incision. In the basin center, widespread shale beds with coal occur above sequence boundaries followed by transgressive sandstone units. These TST sandstones merge toward the basin margin where they lie on older HST sandstones. Maximum flooding surfaces (MFS) have abundant marine microfossils and mangrove pollen, a change in sand stacking pattern, and often a strong seismic reflection with downlap. Fourth-order genetic-type sequences are also interpreted. The MFS is the easiest marker to identify and correlate on well logs. Fourth-order SB occur within these genetic units but are harder to identify and correlate.

  9. Coastal evolution between two giant rivers: The Chan May embayment in central Vietnam

    NASA Astrophysics Data System (ADS)

    Gouramanis, C.; Switzer, A.; Bristow, C.; Pham, D. T.; Mauz, B.; Pile, J.; Doan, L. D.; Hoang, Q. D.; Ngo, C. K.; Dao, N.; Polivka, P.; Soria, L.; Lee, Y.; Sloss, C.; Hoang, L. V.

    2015-12-01

    The coastal landscapes of Vietnam are dominated in the north and south by the very large Red and Mekong rivers. Central Vietnam, in contrast, has few large rivers that flow to the coastal zone. This coupled with the high relief (>1500 m) of the granitic Truong Son Range and shallow gradient continental shelf, has produced two different coastal geomorphologies. The first is a shallow basin infilled with a sequence of parallel, arcuate beach ridges, and the second includes the development of shore-parallel spits and coastal lagoons. All systems are Holocene in age and we present evidence of the Holocene evolution of the northward-facing, beach ridge strandplain located in the Chan May embayment, approximately 35 km north of Danang. This embayment is relatively small (5 km long at the beach and with a beach ridge sequence that spans 11 km from the modern beach to the base of the Truong Son Range) compared to other beach ridge strandplains to the north and south and serves as an analogue for the evolution of these larger systems. The Holocene evolution of the embayment was resolved using Ground Penetrating Radar (GPR), high-resolution sedimentological analysis and quartz Optically Stimulated Luminescence were used to investigate the internal stratigraphy and chronological development of the beach ridges at Chan May. The strandplain contains uniform, clean quartz-rich sediment interspersed by thin heavy mineral rich bands forming shallow-gradient beach ridges that have steadily prograded seaward during the regression after the mid-Holocene sea level highstand. As the beach ridges prograded seaward, a small river feeding directly from the Truong Son Range meandered across the strandplain and significantly modified the embayment. Recently, the river has become much reduced due to anthropogenic modification of the river and landscape. Prior to the Holocene marine highstand, the area was similarly characterized by a surface of prograding beach ridges that were eroded by

  10. Federal Funding in the Delta.

    ERIC Educational Resources Information Center

    Reeder, Richard J.; Calhoun, Samuel D.

    2002-01-01

    The Lower Mississippi Delta region, especially the rural Delta, faces many economic challenges. The rural Delta has received much federal aid in basic income support and funding for human resource development, but less for community resource programs, which are important for economic development. Federal aid to the Delta is analyzed in terms of…

  11. Man made deltas?

    NASA Astrophysics Data System (ADS)

    Maselli, V.; Trincardi, F.

    2014-12-01

    During the last few millennia, southern European fluvio-deltaic systems have evolved in response to changes in the hydrological cycle, mostly driven by high-frequency climate oscillations and increasing anthropic pressure on natural landscapes. The review of geochronological and historical data documents that the bulk of the four largest northern Mediterranean and Black Sea deltas (Ebro, Rhone, Po and Danube) formed during two short and synchronous intervals during which anthropogenic land cover change was the main driver for enhanced sediment production. These two major growth phases occurred under contrasting climatic regimes and were both followed by generalized delta retreat, supporting the hypothesis of human-driven delta progradation. Delta retreat, in particular, was the consequence of reduced soil erosion for renewed afforestation after the fall of the Roman Empire, and of river dams construction that overkilled the still increasing sediment production in catchment basins since the Industrial Era. In this second case, in particular, the effect of a reduced sediment flux to the coasts is amplified by the sinking of modern deltas, due to land subsidence and sea level rise, that hampers delta outbuilding and increases the vulnerability of coastal zone to marine erosion and flooding.

  12. Essential oils from five species of Annonaceae from Vietnam.

    PubMed

    Thang, Tran D; Dai, Do N; Hoi, Tran M; Ogunwande, Isiaka A

    2013-02-01

    The essential oils obtained by hydrodistillation from the leaves of five species of Annonaceace grown in Vietnam were analyzed by gas chromatography (GC) coupled with mass spectrometry (GC/MS). The main constituents of Artabotrys hongkongensis Hance were the sesquiterpenes spathulenol (13.1%), beta-caryophyllene (6.6%), gamma-elemene (6.3%) and delta-cadinene (6.3%). beta-Caryophyllene (12.1%), bicycloelemene (11.2%) and bicyclogermacrene (11.6%) were the predominant components of the oil of Melodorum fruticosum Lour, whereas the oil of Polyalthia longifolia var. pendula Hort was comprised mainly of beta-caryophyllene (30.0%), alpha-zingiberene (21.7%), aromadendrene (15.2%) and beta-selinene (9.1%). The main constituents of Fissistigma maclurei Merr. were germacrene D (26.1%), alpha-terpinene (8.2%), spathulenol (10.0%), and bicyclogermacrene (6.6%), while alpha-santalene (14.3%), beta-caryophyllene (6.3%), terpinen-4-ol (6.3%), caryophyllene oxide (5.7%), trans-alpha-bergamotene (5.3%) and allo-ocimene (5.3%) were identified in significant quantity from Fissistigma rufinerve (Hook.f. & Thomson) Merr. PMID:23513739

  13. Flood Hazard Trends in the Mekong River during the 20th century due to monsoon variability

    NASA Astrophysics Data System (ADS)

    Delgado, Jose; Merz, Bruno; Apel, Heiko

    2013-04-01

    Flood trends were investigated in four stations of the lower Mekong River. Two types of changes were accounted for: trend in the mean and trend in the variance of the time series. A trend in the mean implies that the average flood events changed with time. A trend in variance implies that the frequency of low and high magnitude floods changed with time (Merz et al., 2012). Results showed that average flood events decreased during the 20th century. However, due to an increase in variance, the frequency of high magnitude floods increased towards the end of the 20th century (Delgado et al., 2010). This increase could not be detected by usual trend tests like Mann Kendall test or the ordinary least squares regression. The results agree with Katz and Brown (1992), who showed that variance changes are more important that changes in mean, when it comes to flood frequency trends. To investigate possible causes for the detected changes in flood variance, we looked at several large scale atmospheric circulation patterns cited in the literature. The Western Pacific monsoon index (Wang, 2001) showed the greatest resemblance with the flood data. A test of step change in variance was conducted which revealed a coinciding step change in variance between annual maximum discharge and the Western Pacific monsoon. A statistical model where monsoon variance forces flood frequency in the 20th century was tested. The results were statistically significant. This has the advantadge of by-passing the use of precipitation, which in this region is collected in a rather sparse network. Concerning climate change projections, a dynamic index like the Western Pacific monsoon index is better simulated by climate models than tropical precipitation (Wang, 2004, Douville et al. 2005). Another important result is the attribution of the detected changes. The Mekong River basin is located in a transition zone between the Indian and the Pacific oceans. Our results showed that the interannual variability

  14. Vietnam's Half-Hearted Welcome Home

    ERIC Educational Resources Information Center

    Overland, Martha Ann

    2008-01-01

    Twenty years ago, Vietnam's closed-door policy meant its students were restricted to the former Soviet-bloc countries. Today they study all over the world--about 6,000 are in the United States alone. In many cases, their tuition and living expenses are paid by foreign governments and private charitable organizations. Fulbright, the Ford…

  15. A Resocialization Strategy for Black Vietnam Veterans.

    ERIC Educational Resources Information Center

    Pink, William T.; And Others

    1979-01-01

    The major objective of the Veterans in Education program was to place unemployed or underemployed Black males into the field of education by training them as teachers. The participating Vietnam veterans attended the University of Nebraska while working 30 hours per week in Omaha public school classrooms. (GC)

  16. What Should Our Students Know about Vietnam?

    ERIC Educational Resources Information Center

    Burson, George

    1988-01-01

    Analyzes four concepts contributing to U.S. involvement in Vietnam: (1) security; (2) ideology; (3) economics; and (4) domestic political considerations. Examines reasons why the United States lost the war; reviews combat conditions; and discusses the public attitudes toward the war. (LS)

  17. Ecological Effects of the War in Vietnam

    ERIC Educational Resources Information Center

    Orians, Gordon H.; Pfeiffer, E. W.

    1970-01-01

    Research report on the severe ecological consequences of the defoliation program by American military forces in Vietnam. A significant fraction of mature trees in most forests are killed by single application of herbicides and almost completely killed by repeated sprayings. AAAS is urged to set up an international research program on the…

  18. Student Activism and the War in Vietnam.

    ERIC Educational Resources Information Center

    Geller, Jesse D.; Howard, Gary

    The present study represents an attempt to further delineate the sociological and psychological variables that predispose a student to become an activist of the "new left." A total of 103 students participated in the study, 48 experimental and 55 control subjects. Measures used included a self report, an activism index, a Vietnam opinion Survey,…

  19. Establishment of primary health care in Vietnam.

    PubMed Central

    Birt, C A

    1990-01-01

    Basic demographic and epidemiological data relevant to health problems in Vietnam are described in this paper. Existing health service arrangements are referred to, with particular emphasis on the strategy for development of primary health care. The establishment of the paediatric centre in Ho Chi Minh City is reported, and examples of its valuable work in primary health care development are described. PMID:2121182

  20. Dutch Universities' Joint Aid to Vietnam

    ERIC Educational Resources Information Center

    Higher Education and Research in the Netherlands, 1975

    1975-01-01

    A survey is presented of the joint aid in the reconstruction of North and South Vietnam provided by Dutch universities. The hospital project, solid matter physics project, micro-electronics project, agricultural project and dentistry project are defined. (Author/PG)

  1. Abortion in Vietnam: measurements, puzzles, and concerns.

    PubMed

    Goodkind, D

    1994-01-01

    This report summarizes current knowledge about abortion in Vietnam, drawing upon government statistics, survey data, and fieldwork undertaken by the author in Vietnam throughout 1993 and part of 1994. The official total abortion rate in Vietnam in 1992 was about 2.5 per woman, the highest in Asia and worrisome for a country with a still-high total fertility rate of 3.7 children per woman. Vietnamese provinces exhibited substantial variation in both the rate of abortion and the type of procedures performed. Among the hypotheses explored to explain Vietnam's high rate of abortion are the borrowing of family planning strategies from other poor socialist states where abortion is common; current antinatal population policies that interact with a lack of contraceptive alternatives; and a rise in pregnancies among young and unmarried women in the wake of recent free-market reforms. Because family-size preferences are still declining, abortion rates may continue to increase unless the incidence of unwanted pregnancy can be reduced, a goal that Vietnamese population specialists are seeking to achieve. PMID:7716799

  2. Symptom development in Vietnam era veterans.

    PubMed

    DeFazio, V J; Rustin, S; Diamond, A

    1975-01-01

    Recent studies and clinical reports concerning Vietnam returnees have led to contradictory conclusions as to maladjustment. A questionnaire and symptom checklist was obtain-d from 207 veterans. Significant differences in the mean number of symptoms (e.g., recurrent nightmares, fears, etc.) were found between the combat and non-combat groups. PMID:1111298

  3. Exploration and development offshore southern Vietnam

    SciTech Connect

    Ferguson, A.M. )

    1996-01-01

    In Vietnam, the major focus of the oil and gas industry is on the Nam Con Son and Cuu Long Basins in the southern offshore area. Major licensing first occurred here in the early 1970s. Some exploration was also undertaken by foreign companies in the early 1980s. In 1981, the Soviet Union undertook to assist Vietnam with the development of oil and gas. Vietsovpetro, a joint venture between the then Soviet Oil and Gas Ministry and the Vietnam Oil and Gas Corporation was formed. Most of Vietsovpetro's efforts have been to develop the Bach Ho field in the Cuu Long Basin. This now produces [approximately]130000 bopd. The most recent large scale licensing round occurred in 1992, and, at present, there are over thirty foreign companies active in these Basins' blocks . The first phase of exploration is ending and successes in the Nam Con Son Basin include the BP-led Lan Tay/Lan Do gas discoveries and Pedco's gas discoveries. Mitsubishi's and Petronas' oil discoveries in the Cuu Long Basin have attracted much attention also. The Dai Hung oil field (BHP-operated) has been producing since late 1994. Certain blocks are being appraised, and exploration work is also continuing. Areas of the Cuu Long Basin that were part of Vietsovpetro's acreage, but which may soon be re-licensed, have generated keen interest. The presence of an active upstream industry - exploring, appraising, developing and producing - indicates the emergence of Vietnam as an important East Asian oil and gas player.

  4. Learning Vocabulary in Group Work in Vietnam

    ERIC Educational Resources Information Center

    Huong, Le Pham Hoai

    2006-01-01

    This study investigated learning vocabulary in group work at university in Vietnam. The students were studied in two kinds of group settings, "unassisted" and "assisted", the first consisting of five students from the same class level and the second of four from the same class and a student from a higher class. Differences were observed in both…

  5. Urbanization, migration, and Vietnam's spatial structure.

    PubMed

    Forbes, D

    1996-04-01

    In North Vietnam during the war years from the mid-1960s to the mid-1970s, cities were evacuated to minimize damage from bombing. As such, the urbanization process was checked. In the South, however, urban areas grew rapidly as people fled the fighting in the villages. Reunification of the country led to an outflow of residents from the largest southern cities back to the North or into new economic zones. From the mid-1970s to the early 1980s, Vietnam's total urban population remained static before beginning to increase slowly during the latter half of the 1980s. The rate of urbanization accelerated in the first half of the 1990s, although that process is not reflected in the available statistics. During 1979-89, the smaller cities grew faster than the larger ones, while most interprovincial migration occurred from North to South. Unemployment is a major problem in Vietnam's growing cities. The country's economic reforms require a more fluid labor market with fewer restrictions upon labor mobility. These needs are gradually undermining the strategy designed to contain urbanization, forcing planners to rethink urban development. The author discusses developing Vietnam's three main urban development corridors. PMID:12292069

  6. US Army Chemical Corps Vietnam veterans health study: preliminary results.

    PubMed

    Kang, H K; Dalager, N A; Needham, L L; Patterson, D G; Matanoski, G M; Kanchanaraksa, S; Lees, P S

    2001-01-01

    The long-term health consequences of exposure to phenoxyherbicides used in Vietnam has been a great concern to the veterans. In addition to the Air Force Ranch Hand personnel, Army Chemical Corps personnel who served in Vietnam are thought to have had some of the highest herbicide exposures. The Department of Veterans Affairs commenced a study of veterans who served in Vietnam as members of the Army Chemical Corps and a comparison cohort of Army Chemical Corps personnel who served elsewhere. A total of 2872 Vietnam veterans and 2737 non-Vietnam veterans who served in the Army Chemical Corps were identified for inclusion in a telephone health interview survey with a random 20% sample of veterans receiving serum dioxin and other congeners assessments. In a feasibility study which included 284 Vietnam veterans and 281 non-Vietnam veterans, 100 serum assessments were conducted of which 95 were included in the analysis. Vietnam veterans with a history of spraying herbicides were found to have a statistically significant elevation in their current serum 2,3,7,8-TCDD concentrations compared to non-Vietnam veterans without a spray history (P = 0.05). Other 2,3,7,8-substituted dioxins levels were comparable to the levels found in the non-Vietnam veterans. This feasibility study demonstrated that serum dioxin concentrations from a sample of the study participants can be used to identify exposure variables in the health survey that can serve as a surrogate measure of phenoxyherbicide exposure. PMID:11372888

  7. Impacts of Hydrological Alterations to the Tonle Sap Ecosystem of the Mekong River Basin

    NASA Astrophysics Data System (ADS)

    Arias, M. E.; Cochrane, T. A.

    2013-12-01

    The Tonle Sap is the largest and most important natural wetland in Southeast Asia. It covers an area of more than 15,000 km2 with a unique mosaic of natural and agricultural floodplain habitats that coexist with the largest fishery in the Mekong Basin. Accelerating hydropower development and climate change, however, are altering the Mekong's hydrology, which could negatively affect downstream ecosystems. The Tonle Sap is facing a two-fold problem. First, the link between its hydrology and ecosystem properties is not well understood. Second, potential ecological changes caused by future hydrological disruptions related to hydropower and climate change are unknown. Thus, the main objective of this study was to quantify how alterations to the Mekong hydrology could affect the Tonle Sap ecosystem. An assessment of landscape patterns revealed a distinct relationship between inundation and vegetation. Habitats in the Tonle Sap were divided into five groups based on annual flood duration, as well as physiognomic factors and human activity: (1) open water, (2) gallery forest, (3) seasonally flooded habitats, (4) transitional habitats, and (5) rainfed habitats. Large shifts could occur as a result of hydropower development scenarios by the 2030s; areas optimal for gallery forest could decrease by 82% from baseline conditions, whereas areas of rainfed habitats could increase by 10-13 % (813-1061 km2). An assessment of habitat patterns demonstrated that despite the complexity and intense human use of this ecosystem, the Mekong flood-pulse hydrology is the underlying driver of habitat characteristics by (1) determining inundation depth and duration, (2) creating the main soils gradient, (3) limiting the area cleared for agriculture, (4) influencing vegetation structure and water quality, and (5) shaping the composition of plant species. A numerical model was used to estimate aquatic net primary production (NPP) as a function of hydrology, sediments, and habitat characteristics

  8. Quaternary Morphodynamics for two large rivers: the Fly River, PNG, and the Mekong River, Cambodia.

    NASA Astrophysics Data System (ADS)

    Aalto, R. E.; Lauer, J. W.; Darby, S. E.; Goni, M. A.; Dietrich, W. E.

    2014-12-01

    During glacial marine transgressions, sediment & carbon are deposited due to the infilling of lowland fluvial systems, material that is then largely removed during ensuing regressions. Measuring & modelling these processes would help quantify the amount, timing, & preservation of these materials, providing insight into the morphodynamics of lowland fluvial systems in response to sea level change. We investigated the infilling dynamics of the Fly and Strickland Rivers, Papua New Guinea. Field data include: 14C dated deep cores recording base level evolution over the Holocene, sonar imaging of floodbasin stratigraphy, and the observations of blocked valley lakes and weathered erosional remnants from LGM conditions. Similar research was conducted on the Mekong River, Cambodia, where we have imaged basin fill stratigraphy and recorded the extent of blocked valley lakes. Such field data provide tantalizing empirical glimpses into the landscapes & flux buffering exhibited by large tropical rivers during glacial-interglacial transitions. We upscale our observations by modelling river system evolution, employing a GpU Lowland Landscape Evolution Model (GULLEM) to predict the evolution of the entire basin. A novel & powerful (>10 Tflops on an inexpensive computer) simulator, GULLEM models morphodynamics and estimates the accommodation space subsequently infilled during marine transgressions by representing a range of geomorphic processes, including: river & tributary incision, non-linear diffusion, sea level and isostatic change, hydraulic geometry, tectonic deformation, sediment production, transport & deposition, & tracking of the resulting stratigraphy. GULLEM's vectorized approach allows for massively parallel operation on GPUs (Graphics Processing Unit), making it practical to model coupled fluvial-landscape evolution for complex lowland river systems over large temporal and spatial scales. Our combined approach affords estimates for the timing and budgets of sediment

  9. River reach classification for the Greater Mekong Region at high spatial resolution

    NASA Astrophysics Data System (ADS)

    Ouellet Dallaire, C.; Lehner, B.

    2014-12-01

    River classifications have been used in river health and ecological assessments as coarse proxies to represent aquatic biodiversity when comprehensive biological and/or species data is unavailable. Currently there are no river classifications or biological data available in a consistent format for the extent of the Greater Mekong Region (GMR; including the Irrawaddy, the Salween, the Chao Praya, the Mekong and the Red River basins). The current project proposes a new river habitat classification for the region, facilitated by the HydroSHEDS (HYDROlogical SHuttle Elevation Derivatives at multiple Scales) database at 500m pixel resolution. The classification project is based on the Global River Classification framework relying on the creation of multiple sub-classifications based on different disciplines. The resulting classes from the sub-classification are later combined into final classes to create a holistic river reach classification. For the GMR, a final habitat classification was created based on three sub-classifications: a hydrological sub-classification based only on discharge indices (river size and flow variability); a physio-climatic sub-classification based on large scale indices of climate and elevation (biomes, ecoregions and elevation); and a geomorphological sub-classification based on local morphology (presence of floodplains, reach gradient and sand transport). Key variables and thresholds were identified in collaboration with local experts to ensure that regional knowledge was included. The final classification is composed 54 unique final classes based on 3 sub-classifications with less than 15 classes each. The resulting classifications are driven by abiotic variables and do not include biological data, but they represent a state-of-the art product based on best available data (mostly global data). The most common river habitat type is the "dry broadleaf, low gradient, very small river". These classifications could be applied in a wide range of

  10. Improving Smallholder Farmer Biosecurity in the Mekong Region Through Change Management.

    PubMed

    Young, J R; Evans-Kocinski, S; Bush, R D; Windsor, P A

    2015-10-01

    Transboundary animal diseases including foot-and-mouth disease and haemorrhagic septicaemia remain a major constraint for improving smallholder large ruminant productivity in the Mekong region, producing negative impacts on rural livelihoods and compromising efforts to reduce poverty and food insecurity. The traditional husbandry practices of smallholders largely exclude preventive health measures, increasing risks of disease transmission. Although significant efforts have been made to understand the social aspects of change development in agricultural production, attention to improving the adoption of biosecurity has been limited. This study reviews smallholder biosecurity risk factors identified in the peer-reviewed literature and from field research observations conducted in Cambodia and Laos during 2006-2013, considering these in the context of a change management perspective aimed at improving adoption of biosecurity measures. Motivation for change, resistance to change, knowledge management, cultural dimensions, systems theory and leadership are discussed. Due to geographical, physical and resource variability, the implementation of biosecurity interventions suitable for smallholders is not a 'one size fits all'. Smallholders should be educated in biosecurity principles and empowered to make personal decisions rather than adopt prescribed pre-defined interventions. Biosecurity interventions should be aligned with smallholder farmer motivations, preferably offering clear short-term risk management benefits that elicit interest from smallholders. Linking biosecurity and disease control with improved livestock productivity provides opportunities for sustainable improvements in livelihoods. Participatory research and extension that improves farmer knowledge and practices offers a pathway to elicit sustainable broad-scale social change. However, examples of successes need to be communicated both at the 'evidence-based level' to influence regional policy

  11. Delta II Mars Pathfinder

    NASA Technical Reports Server (NTRS)

    1998-01-01

    Final preparations for lift off of the DELTA II Mars Pathfinder Rocket are shown. Activities include loading the liquid oxygen, completing the construction of the Rover, and placing the Rover into the Lander. After the countdown, important visual events include the launch of the Delta Rocket, burnout and separation of the three Solid Rocket Boosters, and the main engine cutoff. The cutoff of the main engine marks the beginning of the second stage engine. After the completion of the second stage, the third stage engine ignites and then cuts off. Once the third stage engine cuts off spacecraft separation occurs.

  12. Republic of Vietnam. A Study of Higher Education in the Republic of Vietnam and Guide to the Academic Placement of Students from Vietnam in United States Educational Institutions.

    ERIC Educational Resources Information Center

    Jarmon, Hattie; And Others

    This 1970 study of higher education in the Republic of Vietnam looks at an educational system based on the old French colonial system, superimposed on the Chinese Mandarin system, with some evidence of change to prepare students for lives in a modern technological age. Each university and college in Vietnam is reviewed and recommendations for…

  13. Decoding the drivers of bank erosion on the Mekong river: The roles of the Asian monsoon, tropical storms, and snowmelt

    PubMed Central

    Darby, Stephen E; Leyland, Julian; Kummu, Matti; Räsänen, Timo A; Lauri, Hannu

    2013-01-01

    We evaluate links between climate and simulated river bank erosion for one of the world's largest rivers, the Mekong. We employ a process-based model to reconstruct multidecadal time series of bank erosion at study sites within the Mekong's two main hydrological response zones, defining a new parameter, accumulated excess runoff (AER), pertinent to bank erosion. We employ a hydrological model to isolate how snowmelt, tropical storms and monsoon precipitation each contribute to AER and thus modeled bank erosion. Our results show that melt (23.9% at the upstream study site, declining to 11.1% downstream) and tropical cyclones (17.5% and 26.4% at the upstream and downstream sites, respectively) both force significant fractions of bank erosion on the Mekong. We also show (i) small, but significant, declines in AER and hence assumed bank erosion during the 20th century, and; (ii) that significant correlations exist between AER and the Indian Ocean Dipole (IOD) and El Niño Southern Oscillation (ENSO). Of these modes of climate variability, we find that IOD events exert a greater control on simulated bank erosion than ENSO events; but the influences of both ENSO and IOD when averaged over several decades are found to be relatively weak. However, importantly, relationships between ENSO, IOD, and AER and hence inferred river bank erosion are not time invariant. Specifically, we show that there is an intense and prolonged epoch of strong coherence between ENSO and AER from the early 1980s to present, such that in recent decades derived Mekong River bank erosion has been more strongly affected by ENSO. PMID:23926362

  14. Teaching the Vietnam War in the 1990s.

    ERIC Educational Resources Information Center

    Franklin, H. Bruce

    For an instructor who has been teaching the Vietnam War for over 30 years, the War has been teaching him for even longer. One of the objectives in teaching the Vietnam War in the 1990s is what it meant to teach the Vietnam War in the 1960s. It is easy to forget that the antiwar movement began as an attempt to educate the government and the nation,…

  15. Multi-model ensemble simulation and projection in the climate change in the Mekong River Basin. Part I: temperature.

    PubMed

    Huang, Yong; Wang, Fengyou; Li, Yi; Cai, Tijiu

    2014-11-01

    This paper evaluates the performance of the Coupled Model Intercomparison Project phase 5 (CMIP5) in simulating annual and decadal temperature in the Mekong River Basin from 1950 to 2005. By use of Bayesian multi-model averaging method, the future projection of temperature variation under different scenarios are also analyzed. The results show, the performances of climate model are more accurate in space than time, the model can catch the warming characteristics in the Mekong river Basin, but the accuracy of simulation is not good enough. Bayesian multi-model averaging method can improve the annual and decadal temperature simulation when compared to a single result. The projected temperature in Mekong River will increase by 0.88 °C/100 year, 2.15 °C/100 year and 4.96 °C/100 year for the RCP2.6, RCP4.5, and RCP8.5 scenarios, respectively, over the twenty-first century. The findings will be beneficial for local people and policy-maker to formulate regional strategies against the potential menaces of warming scenarios. PMID:25027780

  16. Integrated Optical and SAR Imagery with DEM to Quantify Glacier Water Storage Change in Upper Mekong River Basin

    NASA Astrophysics Data System (ADS)

    Liu, G. T.; Chen, J. B.; Le, T. S.; Chang, C. P.; Shum, C. K.; Tseng, K. H.

    2015-12-01

    In the past few decades, regional increase in air temperature has accelerated the ice melting in polar, sub-polar, and major land glacial areas. The glaciers in Tibetan Plateau, the largest glaciers outside Polar Regions and the sources of several trans-boundary major rivers, are now showing aggravated terminus retreat and thinning. The variation of freshwater availability is crucial for the economic development in Mainland Southeast Asia, especially in hydroelectric generation and agriculture irrigation. These rives, including the Mekong River, is also subject to upstream-downstream conflict and transboundary issues. In this study, we propose to estimate the remaining glacier water storage in Mekong River basin, and further analyze the impact of glacier retreat on these dams/reservoirs for the next decade. By calculating the Modified Normalized Difference Water Index (MNDWI), the water surface area (WSA) can thus be extracted from optical satellite images. On the other hand, the ice surface area (ISA) can be derived from the Polarimetric Synthetic Aperture Radar (POLSAR) images. With different polarization states of electromagnetic wave reflected by earth surface, POLSAR image can effectively identify glacier/ice from snow. Combined WSA and ISA information with digital elevation model (DEM), the change of freshwater storage in glaciers can be estimated. In the end, the influence on dams/reservoirs in the Mekong River caused by glacier retreat can be forecasted. The result can also be applied to hydrology, water allocation, and economy/agriculture policy determination.

  17. Potential Effects of Dams on Migratory Fish in the Mekong River: Lessons from Salmon in the Fraser and Columbia Rivers

    NASA Astrophysics Data System (ADS)

    Ferguson, John W.; Healey, Michael; Dugan, Patrick; Barlow, Chris

    2011-01-01

    We compared the effects of water resource development on migratory fish in two North American rivers using a descriptive approach based on four high-level indicators: (1) trends in abundance of Pacific salmon, (2) reliance on artificial production to maintain fisheries, (3) proportion of adult salmon that are wild- versus hatchery-origin, and (4) number of salmon populations needing federal protection to avoid extinction. The two rivers had similar biological and physical features but radically different levels of water resource development: the Fraser River has few dams and all are located in tributaries, whereas the Columbia River has more than 130 large mainstem and tributary dams. Not surprisingly, we found substantial effects of development on salmon in the Columbia River. We related the results to potential effects on migratory fish in the Mekong River where nearly 200 mainstem and tributary dams are installed, under construction, or planned and could have profound effects on its 135 migratory fish species. Impacts will vary with dam location due to differential fish production within the basin, with overall effects likely being greatest from 11 proposed mainstem dams. Minimizing impacts will require decades to design specialized fish passage facilities, dam operations, and artificial production, and is complicated by the Mekong's high diversity and productivity. Prompt action is needed by governments and fisheries managers to plan Mekong water resource development wisely to prevent impacts to the world's most productive inland fisheries, and food security and employment opportunities for millions of people in the region.

  18. Potential effects of dams on migratory fish in the Mekong River: lessons from salmon in the Fraser and Columbia Rivers.

    PubMed

    Ferguson, John W; Healey, Michael; Dugan, Patrick; Barlow, Chris

    2011-01-01

    We compared the effects of water resource development on migratory fish in two North American rivers using a descriptive approach based on four high-level indicators: (1) trends in abundance of Pacific salmon, (2) reliance on artificial production to maintain fisheries, (3) proportion of adult salmon that are wild- versus hatchery-origin, and (4) number of salmon populations needing federal protection to avoid extinction. The two rivers had similar biological and physical features but radically different levels of water resource development: the Fraser River has few dams and all are located in tributaries, whereas the Columbia River has more than 130 large mainstem and tributary dams. Not surprisingly, we found substantial effects of development on salmon in the Columbia River. We related the results to potential effects on migratory fish in the Mekong River where nearly 200 mainstem and tributary dams are installed, under construction, or planned and could have profound effects on its 135 migratory fish species. Impacts will vary with dam location due to differential fish production within the basin, with overall effects likely being greatest from 11 proposed mainstem dams. Minimizing impacts will require decades to design specialized fish passage facilities, dam operations, and artificial production, and is complicated by the Mekong's high diversity and productivity. Prompt action is needed by governments and fisheries managers to plan Mekong water resource development wisely to prevent impacts to the world's most productive inland fisheries, and food security and employment opportunities for millions of people in the region. PMID:20924582

  19. Impact of Agent Orange exposure among Korean Vietnam veterans.

    PubMed

    Kim, Joung-Soon; Lim, Hyun-Sul; Cho, Sung-Il; Cheong, Hae-Kwan; Lim, Min-Kyung

    2003-07-01

    In order to determine whether Agent Orange exposure was associated with increased frequency of medical problems, we conducted a cross-sectional epidemiologic study of Korean veterans during 1995-1996. 1,224 Vietnam and 154 non-Vietnam veterans were included in the study. Exposure to Agent Orange was assessed by structured in-depth interview on the participants' history of service in Vietnam. Health outcomes were assessed by a standardized comprehensive clinical investigation by a group of clinical specialists. The differences in the prevalence of various medical diagnoses were assessed by Cochran-Mantel-Haenszel chi-square tests comparing the exposure levels of Vietnam veterans, adjusting for age. Multiple logistic regression was performed to estimate the effect of "service in Vietnam" adjusting for age, smoking, alcohol, body mass index, education, and marital status. Vietnam veterans had an increased frequency of eczema (odds ratio [OR] = 6.54), radiculopathy (OR = 3.98), diabetes (OR = 2.69), peripheral neuropathy (OR = 2.39), and hypertension (OR = 2.29), compared to non-Vietnam veterans, adjusting for potential confounders. In addition, higher levels of exposure among Vietnam veterans were associated with increased frequency of ischemic heart disease (p < 0.01), valvular heart disease (p < 0.01), and retinopathy (p < 0.01). We conclude that exposure to Agent Orange is associated with various health impacts in Korean Vietnam veterans. PMID:12916744

  20. Serum dioxin in Vietnam-era veterans - preliminary report

    SciTech Connect

    Not Available

    1987-08-14

    Agent orange, a defoliant used in Vietnam, was a mixture of 2,4-DD and 2,4,5-TS. During manufacture 2,4,5-T was contaminated with TCDD, a compound with marked toxicity in some species of experimental animals. In 1979, the US Congress responded to concerns of Vietnam veterans by passing Public Law 96-151 mandating epidemiologic studies of the possible health effects on Vietnam veterans of exposure to herbicides and their associated dioxin contaminants. In 1983, CDC developed a protocol for a historical cohort study of US Army veterans who had served in heavily sprayed areas of Vietnam. A report on that study is presented.

  1. Lessons from KIPP Delta

    ERIC Educational Resources Information Center

    Maranto, Robert; Shuls, James V.

    2011-01-01

    KIPP Delta succeeds at its stated mission, probably because of its careful attention to culture building. What distinguishes this KIPP school is thoughtful work linking the daily processes of schooling to the goals of schooling, in this case success in college. Day to day tactics reflect broader themes: having a clear mission and hiring staff who…

  2. Delta Airlines LOFT training

    NASA Technical Reports Server (NTRS)

    Whitehead, J.

    1981-01-01

    A LOFT program was developed as part of the DC-9 training program which serves as a prototype for much of Delta's other aircraft training programs. The LOFT used differs little from the ideology presented in the Advisory Circular. Difficulty and experienced concerns regarding the effectiveness of LOFT as a complete training vehicle are explored.

  3. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  4. Using delta-front bathymetry to understand river delta progradation

    NASA Astrophysics Data System (ADS)

    Shaw, J. B.; Mohrig, D. C.

    2010-12-01

    We investigate the delta-front bathymetry of the Wax Lake Delta in Louisiana, USA; a sand rich river delta prograding quickly (~100 m/yr) into a shallow (~2.5 m) basin. The delta-front is the zone separating the bottomset from the topset of the delta. Bottomset sedimentation covers the bed evenly whereas topset sediment transport is focused by flow through distributary channels. The delta front connects these two disparate transport regimes and has a profound effect on channel-network evolution and sedimentary structure of river deltas. Predictions of delta-front topography made by models of delta progradation have rarely been compared to the bathymetry of field-scale deltas. We have mapped 60 km2 of delta front bathymetry immediately seaward of two sub-aerial distributary channels. Subaqueous channels extend up to 2 km seaward of their subaerial portions. These channels lose definition at their distal ends through a combination of channel-bed shoaling and loss of bank relief. Little bathymetric relief is observed at the fronts of the subaqueous channels, calling into question the role of channel-mouth bars in generating the bifurcations observed in this delta-channel network. Near the subaerial to subaqueous transition, steep and eroding sidewalls transition to constructional banks with gentle grades. Grab samples of bed material have been collected throughout the study area in order to detect proximal to distal fining and to constrain the shear stresses connected with delta-front sedimentation. A better understanding of sediment transport in the delta front and its affiliated patterns of erosion and deposition is essential for progress in understanding how river deltas prograde and fill their basins.

  5. The Devil's in the Delta

    ERIC Educational Resources Information Center

    Luyben, William L.

    2007-01-01

    Students frequently confuse and incorrectly apply the several "deltas" that are used in chemical engineering. The deltas come in three different flavors: "out minus in", "big minus little" and "now versus then." The first applies to a change in a stream property as the stream flows through a process. For example, the "[delta]H" in an energy…

  6. Warfare rather than agriculture as a critical influence on fires in the late Holocene, inferred from northern Vietnam

    PubMed Central

    Li, Zhen; Saito, Yoshiki; Dang, Phong X.; Matsumoto, Eiji; Vu, Quang Lan

    2009-01-01

    Fire has played an essential role in the development of human civilization. Most previous research suggests that frequent-fire regimes in the late Holocene were associated with intensification of human activities, especially agriculture development. Here, we analyze fire regimes recorded in the Song Hong delta area of Vietnam over the past 5,000 years. In the prehistoric period, 2 long-term, low-charcoal abundance periods have been linked to periods of low humidity and cool climate, and 5 short-term fire regimes of 100–150 years in duration occurred at regular intervals of ≈700 years. However, over the last 1,500 years, the number, frequency, and intensity of fire regimes clearly increased. Six intensified-fire regime periods in northern Vietnam during this time coincided with changes of Vietnamese dynasties and associated warfare and unrest. In contrast, agricultural development supported by rulers of stable societies at this time does not show a positive correlation with intensified-fire regime periods. Thus, warfare rather than agriculture appears to have been a critical factor contributing to fire regimes in northern Vietnam during the late Holocene. PMID:19597148

  7. Trends and determinants of infant and under-five childhood mortality in Vietnam, 1986–2011

    PubMed Central

    Lee, Hwa-Young; Van Do, Dung; Choi, Sugy; Trinh, Oanh Thi Hoang; To, Kien Gia

    2016-01-01

    Background Although Vietnam has taken great efforts to reduce child mortality in recent years, a large number of children still die at early age. Only a few studies have been conducted to identify at-risk groups in order to provide baseline information for effective interventions. Objective The study estimated the overall trends in infant mortality rate (IMR) and under-five mortality rate (U5MR) during 1986–2011 and identified demographic and socioeconomic determinants of child mortality. Design Data from the Vietnam Multiple Indicator Cluster Surveys (MICSs) in 2000 (MICS2), 2006 (MICS3) and 2011 (MICS4) were analysed. The IMR and U5MR were calculated using the indirect method developed by William Brass. Unadjusted and adjusted odds ratios were estimated to assess the association between child death and demographic and socioeconomic variables. Region-stratified stepwise logistic regression was conducted to test the sensitivity of the results. Results The IMR and U5MR significantly decreased for both male and female children between 1986 and 2010. Male children had higher IMR and U5MR compared with females in all 3 years. Women who were living in the Northern Midlands and Mountain areas were more likely to experience child deaths compared with women who were living in the Red River Delta. Women who were from minor ethnic groups, had low education, living in urban areas, and had multiple children were more likely to have experienced child deaths. Conclusion Baby boys require more healthcare attention during the first year of their life. Comprehensive strategies are necessary for tackling child mortality problems in Vietnam. This study shows that child mortality is not just a problem of poverty but involves many other factors. Further studies are needed to investigate pathways underlying associations between demographic and socioeconomic conditions and childhood mortality. PMID:26950560

  8. Vegetation fires and air pollution in Vietnam.

    PubMed

    Le, Thanh Ha; Thanh Nguyen, Thi Nhat; Lasko, Kristofer; Ilavajhala, Shriram; Vadrevu, Krishna Prasad; Justice, Chris

    2014-12-01

    Forest fires are a significant source of air pollution in Asia. In this study, we integrate satellite remote sensing data and ground-based measurements to infer fire-air pollution relationships in selected regions of Vietnam. We first characterized the active fires and burnt areas at a regional scale from MODIS satellite data. We then used satellite-derived active fire data to correlate the resulting atmospheric pollution. Further, we analyzed the relationship between satellite atmospheric variables and ground-based air pollutant parameters. Our results show peak fire activity during March in Vietnam, with hotspots in the Northwest and Central Highlands. Active fires were significantly correlated with UV Aerosol Index (UVAI), aerosol extinction absorption optical depth (AAOD), and Carbon Monoxide. The use of satellite aerosol optical thickness improved the prediction of Particulate Matter (PM) concentration significantly. PMID:25108840

  9. Hydrographic survey of Chaktomuk, the confluence of the Mekong, Tonlé Sap, and Bassac Rivers near Phnom Penh, Cambodia, 2012

    USGS Publications Warehouse

    Dietsch, Benjamin J.; Densmore, Brenda K.; Wilson, Richard C.

    2014-01-01

    Detailed hydrographic maps of Mekong, Tonlé Sap, and Bassac Rivers showing the riverbed elevations surveyed April 21–May 2, 2012, referenced to Ha Tien 1960 were produced. The surveyed area included a 2-km stretch of the Mekong River between the confluence with the Tonlé Sap and Bassac Rivers, and extended 4 km upstream and 3.6 km downstream from the 2,000-m confluence stretch of the Mekong River. In addition, 0.7 km of the Bassac River downstream and 3.5 km of the Tonlé Sap River (from the confluence to Chroy Changvar Bridge) upstream from their confluence with the Mekong River were surveyed. Riverbed features (such as dunes, shoals, and the effects of sediment mining, which were observed during data collection) are visible on the hydrographic maps. All surveys were completed at low annual water levels as referenced to nearby Mekong River Commission streamflow-gaging stations. Riverbed elevations surveyed ranged from 24.08 m below to 1.54 m above Ha Tien 1960.

  10. Vegetation distribution pattern in the dam areas along middle-low reach of Lancang-Mekong River in Yunnan Province, China

    NASA Astrophysics Data System (ADS)

    Li, Jinpeng; Dong, Shikui; Peng, Mingchun; Li, Xiaoyan; Liu, Shiliang

    2012-09-01

    Lancang-Mekong River Basin is one of ecoregions with rich biodiversity and high ecological values in the world. The basin has been strongly affected by human activities, particularly by dam construction. This study was conducted to investigate the vegetation distribution patterns in the dam areas along middle-low reach of the Lancang-Mekong River in Yunnan Province of China, where eight cascade dams have been planned or are being constructed. To identify the vegetation composition and structure, we sampled 126 quadrats along the transects arrayed vertically to both side of river channel from the year of 2004 to 2010. We found that the forest, shrub and grass communities were widely spread along the riverside. In low reach watershed of the Lancang-Mekong River, the dominated vegetations were grasses and shrubs which were severely disturbed by human activity. In middle reach of the Lancang-Mekong River, the dry-hot valley vegetation was found in the low valley. At high altitude, the pine forest and semi-evergreen seasonal forest were found. As a result of dam construction and operation, the structure and compositions of riparian vegetation were strongly changed. Some plants declined or disappeared due to the alteration of their habitats. The protection or restoration interventions are urgently needed to mitigate the risk of vegetation damage associated with dam projects along middle and low reach of the Lancang-Mekong River.

  11. [Plantar pruritus after trip to Vietnam].

    PubMed

    Tanneberger, O; Fehr, J; Nuesch, R

    2007-10-01

    A 33 year old man is evaluated for a pruriginous plantar eruption on the right foot. Three weeks ago he walked across a river barefoot in the south of Vietnam. In the clinical examination of the foot a red, serpiginuous dermatitis was seen. Patient history and clinical picture were typical for a larva migrans. After starting a treatment with albendazol the patient felt well and the lesions disappeared. PMID:17966826

  12. Exploration and development offshore southern Vietnam

    SciTech Connect

    Ferguson, A.M.

    1996-12-31

    In Vietnam, the major focus of the oil and gas industry is on the Nam Con Son and Cuu Long Basins in the southern offshore area. Major licensing first occurred here in the early 1970s. Some exploration was also undertaken by foreign companies in the early 1980s. In 1981, the Soviet Union undertook to assist Vietnam with the development of oil and gas. Vietsovpetro, a joint venture between the then Soviet Oil and Gas Ministry and the Vietnam Oil and Gas Corporation was formed. Most of Vietsovpetro`s efforts have been to develop the Bach Ho field in the Cuu Long Basin. This now produces {approximately}130000 bopd. The most recent large scale licensing round occurred in 1992, and, at present, there are over thirty foreign companies active in these Basins` blocks . The first phase of exploration is ending and successes in the Nam Con Son Basin include the BP-led Lan Tay/Lan Do gas discoveries and Pedco`s gas discoveries. Mitsubishi`s and Petronas` oil discoveries in the Cuu Long Basin have attracted much attention also. The Dai Hung oil field (BHP-operated) has been producing since late 1994. Certain blocks are being appraised, and exploration work is also continuing. Areas of the Cuu Long Basin that were part of Vietsovpetro`s acreage, but which may soon be re-licensed, have generated keen interest. The presence of an active upstream industry - exploring, appraising, developing and producing - indicates the emergence of Vietnam as an important East Asian oil and gas player.

  13. Prevalence and risk factors associated with Cryptosporidium oocysts shedding in pigs in Central Vietnam.

    PubMed

    Nguyen, Sam Thi; Honma, Hajime; Geurden, Thomas; Ikarash, Makoto; Fukuda, Yasuhiro; Huynh, Vu Vy; Nguyen, Duc Tan; Nakai, Yutaka

    2012-10-01

    We investigated the prevalence and risk factors associated with Cryptosporidium oocysts shedding in pigs in Central Vietnam. A total of 740 single fecal samples collected from diarrheic and non-diarrheic pigs on 89 farms were screened by the modified Ziehl-Neelsen staining method. Prevalence at the animal and the farm levels were 18.1% (134/740) and 71.9% (64/89), respectively. Risk factors for the infection were identified using univariate and multivariate logistic regression analysis. The results revealed that age, sanitary condition and topography were significantly associated with oocyst shedding (P<0.05). Pre-weaned piglets were at the highest risk for infection, followed by post-weaners, sows and finishing pigs. Good sanitary conditions showed positive effects in decreasing oocysts shedding. Topographically, Cryptosporidium was more common in mountainous zone than that in coastal delta zone. There was an association between the occurrence of diarrhea and the level of Cryptosporidium oocyst excretion within infected pigs. This is the first epidemiological investigation of prevalence and risk factors of Cryptosporidium in pigs in Vietnam. PMID:22342125

  14. Sustainable hydropower in Lower Mekong Countries: Technical assessment and training travel report

    SciTech Connect

    Hadjerioua, Boualem; Witt, Adam M.

    2015-08-01

    The U.S. Agency for International Development (USAID), through their partnership with the U.S. Department of the Interior (DOI), requested the support of Oak Ridge National Laboratory (ORNL) to provide specialized technical assistance as part of the Smart Infrastructure for the Mekong (SIM) Program in Thailand. Introduced in July 2013 by U.S. Secretary of State John Kerry, SIM is a U.S. Government Inter-Agency program that provides Lower Mekong partner countries with targeted, demand-driven technical and scientific assistance to support environmentally sound, climate conscious and socially equitable infrastructure, clean energy development, and water resources optimization. The U.S. Government is committed to supporting sustainable economic development within the region by providing tools, best practices, technical assistance, and lessons learned for the benefit of partner countries. In response to a request from the Electricity Generating Authority of Thailand (EGAT), a SIM project was developed with two main activities: 1) to promote hydropower sustainability and efficiency through technical assessment training at two existing hydropower assets in Thailand, and 2) the design and implementation of one national and two or three regional science and policy workshops, to be co-hosted with EGAT, to build common understanding of and commitment to environmental and social safeguards for Mekong Basin hydropower projects. The U.S. Department of Energy (DOE) is leading the technical assessment (Activity 1), and has contracted ORNL to provide expert technical assistance focused on increasing efficiency at existing projects, with the goal of increasing renewable energy generation at little to no capital cost. ORNL is the leading national laboratory in hydropower analysis, with a nationally recognized and highly qualified team of scientists addressing small to large-scale systems (basin-, regional-, and national-scale) energy generation optimization analysis for DOE. The

  15. Martian deltas: Morphology and distribution

    NASA Technical Reports Server (NTRS)

    Rice, J. W., Jr.; Scott, D. H.

    1993-01-01

    Recent detailed mapping has revealed numerous examples of Martian deltas. The location and morphology of these deltas are described. Factors that contribute to delta morphology are river regime, coastal processes, structural stability, and climate. The largest delta systems on Mars are located near the mouths of Maja, Maumee, Vedra, Ma'adim, Kasei, and Brazos Valles. There are also several smaller-scale deltas emplaced near channel mouths situated in Ismenius Lacus, Memnonia, and Arabia. Delta morphology was used to reconstruct type, quantity, and sediment load size transported by the debouching channel systems. Methods initially developed for terrestrial systems were used to gain information on the relationships between Martian delta morphology, river regime, and coastal processes.

  16. Understanding pesticides in California's Delta

    USGS Publications Warehouse

    Kuivila, Kathryn M.; Orlando, James L.

    2012-01-01

    The Sacramento-San Joaquin River Delta (Delta) is the hub of California’s water system and also an important habitat for imperiled fish and wildlife. Aquatic organisms are exposed to mixtures of pesticides that flow through the maze of Delta water channels from sources including agricultural, landscape, and urban pest-control applications. While we do not know all of the effects pesticides have on the ecosystem, there is evidence that they cause some damage to organisms in the Delta. Decades of USGS research have provided a good understanding of when, where, and how pesticides enter the Delta. However, pesticide use is continually changing. New field studies and methods are needed so that scientists can analyze which pesticides are present in the Delta, and at what concentrations, enabling them to estimate exposure and ultimate effects on organisms. Continuing research will provide resource managers and stakeholders with crucial information to manage the Delta wisely.

  17. Current status of cysticercosis in Vietnam.

    PubMed

    Willingham, A Lee; De, Nguyen Van; Doanh, Nguyen Quoc; Cong, Le Dinh; Dung, Truong Van; Dorny, Pierre; Cam, Phung Dac; Dalsgaard, Anders

    2003-01-01

    This English review concerning the current status of cysticercosis in Vietnam has been compiled from various reports of studies conducted over the past 15 years, which have appeared in national publications in Vietnamese, in order to make the information available to the international community. Hospital surveys indicate that cysticercosis is emerging as a serious health problem in the country though most of the information comes from the Hanoi area. Many more men than women are being treated for cysticercosis with most patients being young to middle-aged adults though several juvenile cases have been seen in the south. Clinical manifestations of the disease in humans include subcutaneous nodules, epileptic seizures, severe headache, impaired vision and memory loss. Albendazole has been found to be the best drug for treating cysticercosis though it does not appear to be totally effective for curing cerebral cysts. Information concerning porcine and bovine cysticercosis is very limited and based mostly on passive surveillance at Hanoi slaughterhouses. Surveys for human taeniasis in central and northern provinces indicate a prevalence of 0.2-7.2%. However, techniques of low sensitivity were used and the results are inconclusive since it is unknown with which species of tapeworm the people were infected. In addition to Taenia solium which causes human cysticercosis, T. saginata and T. asiatica are also known to be present in Vietnam. Risk factors investigated thus far with regard to transmission of T. solium suggest that consumption of raw pork, inadequate or absent meat inspection and control, poor sanitation in some areas, and the use of untreated human waste as fertilizer for crops may play important roles in Vietnam but this remains to be validated. The evidence thus far collected suggests that a national surveillance program for cysticercosis is a great need for Vietnam. The authors recommend further research on the epidemiology and impact of cysticercosis in

  18. Medical Hydrogeology of Asian Deltas: Status of Groundwater Toxicants and Nutrients, and Implications for Human Health

    PubMed Central

    Hoque, Mohammad A.; Butler, Adrian P.

    2015-01-01

    Drinking water, a fluid primarily for human hydration, is also a source of mineral nutrients. Groundwater, a drinking water source for more than 70% of inhabitants living in Asian deltas, has received much attention because of its naturally occurring arsenic, but the linkage of arsenic toxicity with other water constituents has not been studied. In addition, although nutrients are generally provided by food, in under developed rural settings, where people subsist on low nutrient diets, drinking-water-nutrients may supply quantities vital to human health thereby preventing diseases. Here, we show, using augmented datasets from three Asian deltas (Bengal, Mekong, and Red River), that the chemical content of groundwater is such that in some areas individuals obtain up to 50% or more of the recommended daily intake (RDI) of some nutrients (e.g., calcium, magnesium, iron) from just two litres of drinking water. We also show some indications of a spatial association of groundwater nutrients and health outcome using demographic health data from Bangladesh. We therefore suggest that an understanding of the association of non-communicable disease and poor nutrition cannot be developed, particularly in areas with high levels of dissolved solids in water sources, without considering the contribution of drinking water to nutrient and mineral supply. PMID:26712780

  19. Medical Hydrogeology of Asian Deltas: Status of Groundwater Toxicants and Nutrients, and Implications for Human Health.

    PubMed

    Hoque, Mohammad A; Butler, Adrian P

    2016-01-01

    Drinking water, a fluid primarily for human hydration, is also a source of mineral nutrients. Groundwater, a drinking water source for more than 70% of inhabitants living in Asian deltas, has received much attention because of its naturally occurring arsenic, but the linkage of arsenic toxicity with other water constituents has not been studied. In addition, although nutrients are generally provided by food, in under developed rural settings, where people subsist on low nutrient diets, drinking-water-nutrients may supply quantities critical to human health thereby preventing diseases. Here, we show, using augmented datasets from three Asian deltas (Bengal, Mekong, and Red River), that the chemical content of groundwater is so substantial that in some areas individuals obtain up to 50% or more of the recommended daily intake (RDI) of some nutrients (e.g., calcium, magnesium, iron) from just two litres of drinking water. We also show some indications of a spatial association of groundwater nutrients and health outcome using demographic health data from Bangladesh. We therefore suggest that an understanding of the association of non-communicable disease and poor nutrition cannot be developed, particularly in areas with high levels of dissolved solids in water sources, without considering the contribution of drinking water to nutrient and mineral supply. PMID:26712780

  20. A list of oribatid mites (Acari, Oribatida) of Vietnam

    PubMed Central

    Ermilov, Sergey G.

    2015-01-01

    Abstract A species list of identified oribatid mite taxa (Acari, Oribatida) in the fauna of Vietnam is provided. During 1967–2015, a total of 535 species/subspecies from 222 genera and 81 families was registered. Of these, 194 species/subspecies were described as new for science from Vietnam. PMID:26798306

  1. Transforming Vietnam's Medical Education through E-Learning

    ERIC Educational Resources Information Center

    Churton, Michael W.

    2011-01-01

    The costs for providing medical school education and services in Vietnam's universities continue to increase. Through a collaborative project between the Government of the Netherlands and Vietnam's Ministry of Health, a five year experimental program to develop in-country capacity and reduce the dependence upon a foreign medical service delivery…

  2. Second Generation Effect of Vietnam: Adolescent Children of Combat Veterans.

    ERIC Educational Resources Information Center

    Dansby, Virginia Smejkal

    Although extensive research has focused upon the adjustment problems of the veterans of the Vietnam conflict, little data is available concerning their children. The purpose of this study was to provide a description of the adolescent children who have lived with Vietnam combat veteran fathers, comparing them (on the basis of social and personal…

  3. 78 FR 7452 - Steel Wire Garment Hangers From Vietnam; Determinations

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-01

    ... Register on August 20, 2012 (77 FR 50160) and on August 22, 2012 (77 FR 50713, corrected). The hearing was... COMMISSION Steel Wire Garment Hangers From Vietnam; Determinations On the basis of the record \\1\\ developed... imports of steel wire garment hangers from Vietnam, provided for in subheading 7326.20.00 of...

  4. Education and Inequalities in Rural Vietnam in the 1990s

    ERIC Educational Resources Information Center

    Belanger, Daniele; Liu, Jianye

    2008-01-01

    This article examines the determinants of children's schooling during the 1990s in rural areas of Vietnam. It focuses on the impact of family attributes on the likelihood of children remaining in school or leaving during the primary and secondary school years. Using data from the Vietnam Living Standard Survey (VLSS) of 1992-93 and 1997-98, the…

  5. What Should We Tell Our Children about Vietnam?

    ERIC Educational Resources Information Center

    McCloud, Bill

    1988-01-01

    Describes McCloud's efforts to improve coverage of the Vietnam War in the junior high school curriculum. Presents answers to the question "What do you think are the most important things for today's junior high students to understand about the Vietnam War?" from people such as Ronald Reagan, Jimmy Carter, Tom Hayden, and Robert S. McNamara. (GEA)

  6. Using Oral History to Teach the Vietnam War.

    ERIC Educational Resources Information Center

    Burson, George

    1988-01-01

    Illustrates the strengths and weaknesses of oral histories through an oral history assignment that helps students understand the impact of the Vietnam War on the "Vietnam generation." Suggests introductory materials and lists exemplar interview questions for students to use in interviewing soldiers who were on active duty and those who were not.…

  7. Primary English Language Education Policy in Vietnam: Insights from Implementation

    ERIC Educational Resources Information Center

    Nguyen, Hoa Thi Mai

    2011-01-01

    The introduction of English in primary education curricula is a phenomenon occurring in many non-English-speaking countries in Asia, including Vietnam. Recently, the Ministry of Education and Training (MOET) in Vietnam issued guidelines for the piloting of an English as a foreign language (EFL) primary curriculum in which English is taught as a…

  8. Latent Classes of PTSD Symptoms in Vietnam Veterans

    ERIC Educational Resources Information Center

    Steenkamp, Maria M.; Nickerson, Angela; Maguen, Shira; Dickstein, Benjamin D.; Nash, William P.; Litz, Brett T.

    2012-01-01

    The authors examined heterogeneity in posttraumatic stress disorder (PTSD) symptom presentation among veterans (n = 335) participating in the clinical interview subsample of the National Vietnam Veterans Readjustment Study. Latent class analysis was used to identify clinically homogeneous subgroups of Vietnam War combat veterans. Consistent with…

  9. Teaching English in Primary Schools in Vietnam: An Overview

    ERIC Educational Resources Information Center

    Hoa, Nguyen Thi Mai; Tuan, Nguyen Quoc

    2007-01-01

    This paper examines the English language situation at primary school level in Vietnam from a language planning perspective. It examines language policy for foreign language teaching in Vietnam to provide a picture of the role of English in foreign language education. It analyses language-in-education policy, curriculum and teaching materials, and…

  10. Masculinity and Punishment: Men's Upbringing of Boys in Rural Vietnam

    ERIC Educational Resources Information Center

    Rydstrom, Helle

    2006-01-01

    This article examines men's use of physical punishment when interacting with their sons or grandsons in rural Vietnam. By drawing on two periods of anthropological fieldwork in a northern Vietnamese commune, the article analyses the ways in which violence is informed by, while also perpetually reinforcing, a masculine discourse. Vietnam has…

  11. Vietnam to Central America: A Case of Educational Failure.

    ERIC Educational Resources Information Center

    Kincheloe, Joe; Staley, George

    1983-01-01

    Vietnam and El Salvador can serve as models depicting the failure of American education to teach students to critically and objectively examine a current event. Only a decade after the Vietnam debacle, public schools are once again equating critical inquiry into the formulation of American foreign policy with anti-Americanism. (RM)

  12. Education and Economic, Political, and Social Change in Vietnam

    ERIC Educational Resources Information Center

    Huong, Pham Lan; Fry, Gerald W.

    2004-01-01

    This paper provides an overview of the complex relations among history, education, political economy, and social change in Vietnam. Vietnam has a long history of education and a literate culture. The evolution of Vietnamese culture and society is characterized by both persistence and change. Social and political persistence and change have been…

  13. Vietnam War Veteran-Poets: The Ideology of Horror.

    ERIC Educational Resources Information Center

    Holdstein, Deborah H.

    1983-01-01

    Verses written by Vietnam veterans from "Winning Hearts and Minds" are discussed in terms of two thematic categories: that which smashes the hypocrisy and myths of America and its patriotism, and that which documents and records the veteran's experience. This accessible, immediate poetic documentation of the Vietnam experience merits recognition.…

  14. The History and Future of Community Colleges in Vietnam

    ERIC Educational Resources Information Center

    Le, Anh T.

    2013-01-01

    Since 1986, with the creation of the Renovation ("Doi moi") policy, Vietnam has demonstrated a strong commitment to the improvement of its higher education system. After 25 years of opening its doors to the global educational environment, Vietnam has achieved some notable accomplishments. The country's higher educational system has become more…

  15. Effective Primary Schools in Geographically Isolated Areas of Vietnam

    ERIC Educational Resources Information Center

    Ikeda, Miyako

    2010-01-01

    This study identifies the major characteristics of "effective" primary schools in isolated areas in Vietnam. It suggests areas in which the implementation of beneficial changes can occur. Pupils in isolated areas of Vietnam are, in many respects, educationally disadvantaged. Usually, these pupils are in schools that have fewer educational…

  16. Vietnam: Education Financing. A World Bank Country Study.

    ERIC Educational Resources Information Center

    World Bank, Washington, DC.

    This study examines the system of education and training in Vietnam and poses the question: what changes in educational policies will ensure that students who pass through the system today will acquire the knowledge, skills, and attitudes needed for Vietnam to successfully complete the transition from a planned to a market economy? The report…

  17. Teaching the New Vietnam: It's a Country, Not a War

    ERIC Educational Resources Information Center

    McCornac, Dennis C.

    2008-01-01

    Vietnam has made remarkable progress over the past two decades in its transition to a market economy resulting in numerous changes to both its social and economic institutions. It is a nation at peace focusing on economic development and integrating into the world economy. Although the tragic events in Vietnam's history cannot be forgotten, the…

  18. 75 FR 54087 - Education Trade Mission to Indonesia and Vietnam

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-03

    ... International Trade Administration Education Trade Mission to Indonesia and Vietnam AGENCY: International Trade... education trade mission to Indonesia and Vietnam, April 3-8, 2011. Led by a senior Department of Commerce... accredited U.S. education institutions. However, the emphasis will be on community colleges,...

  19. 75 FR 55740 - Certain Frozen Warmwater Shrimp From the Socialist Republic of Vietnam: Extension of Preliminary...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-09-14

    ... Vietnam and the People's Republic of China, 75 FR 18154 (April 9, 2010). The preliminary results of the... International Trade Administration Certain Frozen Warmwater Shrimp From the Socialist Republic of Vietnam... frozen warmwater shrimp from the Socialist Republic of Vietnam (``Vietnam''). The review covers...

  20. 38 CFR 3.313 - Claims based on service in Vietnam.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... in Vietnam. 3.313 Section 3.313 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS... Evaluations; Service Connection § 3.313 Claims based on service in Vietnam. (a) Service in Vietnam. Service in Vietnam includes service in the waters offshore, or service in other locations if the conditions...

  1. 78 FR 40100 - Certain Frozen Fish Fillets from the Socialist Republic of Vietnam: Rescission of Antidumping...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-03

    ... Socialist Republic of Vietnam: Initiation of Antidumping Duty New Shipper Review; 2012- 2013, 78 FR 18957... International Trade Administration Certain Frozen Fish Fillets from the Socialist Republic of Vietnam... Republic of Vietnam (``Vietnam'') covering the period August 1, 2012, through January 31, 2013.\\1\\ On...

  2. 31 CFR 500.565 - Family remittances to nationals of Vietnam and Cambodia.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Vietnam and Cambodia. 500.565 Section 500.565 Money and Finance: Treasury Regulations Relating to Money... remittances to nationals of Vietnam and Cambodia. (a) The remittances specified in this section are authorized... relative is a national of Vietnam or Cambodia, is a resident of Vietnam, Cambodia, or a country to...

  3. The Future of Patriotism: The War Film, The Cinema Industry, and the Vietnam Veteran Movement.

    ERIC Educational Resources Information Center

    Camacho, Paul

    1990-01-01

    Examines the media's effect on attitudes about Vietnam veterans. Discusses the relationship between media and culture. Analyzes the film industry's ideological battle over Vietnam. Critiques the media's treatment of the Vietnam experience, and considers the impact of media portrayals of the war on the Vietnam Veteran's movement. (RW)

  4. 38 CFR 3.313 - Claims based on service in Vietnam.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... in Vietnam. 3.313 Section 3.313 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS... Evaluations; Service Connection § 3.313 Claims based on service in Vietnam. (a) Service in Vietnam. Service in Vietnam includes service in the waters offshore, or service in other locations if the conditions...

  5. 38 CFR 3.313 - Claims based on service in Vietnam.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... in Vietnam. 3.313 Section 3.313 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS... Evaluations; Service Connection § 3.313 Claims based on service in Vietnam. (a) Service in Vietnam. Service in Vietnam includes service in the waters offshore, or service in other locations if the conditions...

  6. 38 CFR 3.313 - Claims based on service in Vietnam.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... in Vietnam. 3.313 Section 3.313 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS... Evaluations; Service Connection § 3.313 Claims based on service in Vietnam. (a) Service in Vietnam. Service in Vietnam includes service in the waters offshore, or service in other locations if the conditions...

  7. 38 CFR 3.313 - Claims based on service in Vietnam.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... in Vietnam. 3.313 Section 3.313 Pensions, Bonuses, and Veterans' Relief DEPARTMENT OF VETERANS... Evaluations; Service Connection § 3.313 Claims based on service in Vietnam. (a) Service in Vietnam. Service in Vietnam includes service in the waters offshore, or service in other locations if the conditions...

  8. Mississippi River Delta

    NASA Technical Reports Server (NTRS)

    2002-01-01

    As the Mississippi River enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the mid continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown on this image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad stripe running northwest to southeast.

    This image was acquired on May 24, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite. With its 14 spectral bands from the visible to the thermal infrared wavelength region, and its high spatial resolution of 15 to 90 meters (about 50 to 300 feet), ASTER will image Earth for the next 6 years to map and monitor the changing surface of our planet.

    ASTER is one of five Earth-observing instruments launched December 18,1999, on NASA's Terra satellite. The instrument was built by Japan's Ministry of Economy, Trade and Industry. A joint U.S./Japan science team is responsible for validation and calibration of the instrument and the data products. Dr. Anne Kahle at NASA's Jet Propulsion Laboratory, Pasadena, California, is the U.S. Science team leader; Bjorn Eng of JPL is the project manager. The Terra mission is part of NASA's Earth Science Enterprise, a long-term research and technology program designed to examine Earth's land, oceans, atmosphere, ice and life as a total integrated system.

    The broad spectral coverage and high spectral resolution of ASTER will provide scientists in numerous disciplines with critical information for surface mapping

  9. Quantifying fluvial sediment flux on a monsoonal mega-river: the Mekong

    NASA Astrophysics Data System (ADS)

    Parsons, D. R.; Darby, S. E.; Hackney, C. R.; Best, J.; Aalto, R. E.; Nicholas, A. P.; Leyland, J.

    2013-12-01

    Quantifying sediment fluxes and distinguishing between bed-load and suspended-load (bed-load and suspended bed-load) transport of large rivers remains a significant challenge. It is increasingly apparent that prediction of large river morphodynamics in response to environmental change requires a robust quantification of sediment fluxes across a range of discharges. Such quantification becomes even more problematic for monsoonal rivers where large non-linearities in hydrological-sediment relations exist. This paper, as part of a NERC funded STELAR-S2S project (www.stelar-s2s.org), presents a series of multibeam sonar repeat bed surveys and acoustic calibrations that allow simultaneous quantification of bed-load transport and suspended load fluxes in the lower Mekong River. Results show how multibeam sonar can be used to map bedform evolution across a range of time scales and produce robust extimates of bed-load whilst acoustic backscatter calibration to suspended sediment load can be used in combination to Doppler flow velocity estimates to recover full sediment fluxes at the reach scale. The methods, estimates of error and implications of the results for the function of large river systems will be discussed.

  10. Meiobenthos assemblages in the mekong estuarine system with special focus on free-living marine nematodes

    NASA Astrophysics Data System (ADS)

    Quang, Ngo Xuan; Vanreusel, Ann; Smol, Nic; Chau, Nguyen Ngoc

    2010-12-01

    Meiobenthos assemblages in eight estuaries of the Mekong river system were investigated in August 2008 (from the Cua Tieu estuary to the Tran De estuary). In each estuary, one sampling station was established for meiobenthos sampling. Twelve major taxa of meiobenthos were recorded in this estuarine system, including Nematoda, Copepoda, Turbellaria, Polychaeta, Oligochaeta, Tardigrada, Bivalvia, Ostracoda, Amphipoda, Cumacea, Gastrotricha, Gastropoda, and Crustacean Nauplii larvae. The densities of the meiobenthos range from 581 to 3168 inds/10 cm2. Nematodes always occupy the highest numbers with a percentage ranging from 64-99%. There are 135 nematode genera recorded in this study with the following as dominant genera Desmodora, Leptolaimus, Halalaimus, Thalassomonhystera, Theristus, Daptonema, Rhynchonema, Parodontophora, and Oncholaimus. Although the biodiversity of the meiobenthos at higher taxa level is not high compared to other marine environments, the estimates of nematode biodiversity at the genus level indicates high values. The increase in number of genera with increasing sampling intensity illustrate that the diversity is underestimated and would have been higher if the authors had considered a larger number of individuals, more replicates per station, and more sampling stations.

  11. Natural processes in delta restoration: application to the Mississippi Delta.

    PubMed

    Paola, Chris; Twilley, Robert R; Edmonds, Douglas A; Kim, Wonsuck; Mohrig, David; Parker, Gary; Viparelli, Enrica; Voller, Vaughan R

    2011-01-01

    Restoration of river deltas involves diverting sediment and water from major channels into adjoining drowned areas, where the sediment can build new land and provide a platform for regenerating wetland ecosystems. Except for local engineered structures at the points of diversion, restoration mainly relies on natural delta-building processes. Present understanding of such processes is sufficient to provide a basis for determining the feasibility of restoration projects through quantitative estimates of land-building rates and sustainable wetland area under different scenarios of sediment supply, subsidence, and sea-level rise. We are not yet to the point of being able to predict the evolution of a restored delta in detail. Predictions of delta evolution are based on field studies of active deltas, deltas in mine-tailings ponds, experimental deltas, and countless natural experiments contained in the stratigraphic record. These studies provide input for a variety of mechanistic delta models, ranging from radially averaged formulations to more detailed models that can resolve channels, topography, and ecosystem processes. Especially exciting areas for future research include understanding the mechanisms by which deltaic channel networks self-organize, grow, and distribute sediment and nutrients over the delta surface and coupling these to ecosystem processes, especially the interplay of topography, network geometry, and ecosystem dynamics. PMID:21329199

  12. Pioneer Launch on Delta Vehicle

    NASA Technical Reports Server (NTRS)

    1969-01-01

    NASA launches the last in the series of interplanetary Pioneer spacecraft, Pioneer 10 from Cape Kennedy, Florida. The long-tank Delta launch vehicle placed the spacecraft in a solar orbit along the path of Earth's orbit. The spacecraft then passed inside and outside Earth's orbit, alternately speeding up and slowing down relative to Earth. The Delta launch vehicle family started development in 1959. The Delta was composed of parts from the Thor, an intermediate-range ballistic missile, as its first stage, and the Vanguard as its second. The first Delta was launched from Cape Canaveral on May 13, 1960 and was powerful enough to deliver a 100-pound spacecraft into geostationary transfer orbit. Delta has been used to launch civil, commercial, and military satellites into orbit. For more information about Delta, please see Chapter 3 in Roger Launius and Dennis Jenkins' book To Reach the High Frontier published by The University Press of Kentucky in 2002.

  13. Delta in Eberswalde

    NASA Technical Reports Server (NTRS)

    2006-01-01

    This HiRISE image covers a portion of a delta that partially fills Eberswalde crater in Margaritifer Sinus. The delta was first recognized and mapped using MOC images that revealed various features whose presence required sustained flow and deposition into a lake that once occupied the crater. The HiRISE image resolves meter-scale features that record the migration of channels and delta distributaries as the delta grew over time. Differences in grain-size of sediments within the environments on the delta enable differential erosion of the deposits. As a result, coarser channel deposits are slightly more resistant and stand in relief relative to finer-grained over-bank and more easily eroded distal delta deposits. Close examination of the relict channel deposits confirms the presence of some meter-size blocks that were likely too coarse to have been transported by water flowing within the channels. These blocks may be formed of the sand and gravel that more likely moved along the channels that was lithified and eroded. Numerous meter-scale polygonal structures are common on many surfaces, but mostly those associated with more quiescent depositional environments removed from the channels. The polygons could be the result of deposition of fine-grained sediments that were either exposed and desiccated (dried out), rich in clays that shrunk when the water was removed, turned into rock and then fractured and eroded, or some combination of these processes.

    Image PSP_001336_1560 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 8, 2006. The complete image is centered at -23.8 degrees latitude, 326.4 degrees East longitude. The range to the target site was 256.3 km (160.2 miles). At this distance the image scale is 25.6 cm/pixel (with 1 x 1 binning) so objects 77 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel and north is up. The image was

  14. Vietnam: expanding the social security system.

    PubMed

    Pruzin, D

    1996-01-01

    Viet Nam's shift toward a market-oriented economy has been associated with annual gross domestic product growth of more than 8% over the past 5 years. At the same time, the emergence of private-sector enterprises and subsequent closure of many state-run enterprises have had profound implications for Viet Nam's social protection systems. At present, only 5.6 million of the country's 33 million workers are covered under the state-run social insurance system. In 1995, the government moved to include private enterprises with 10 or more employees in its state benefits system. The International Labor Organization (ILO) has been working with the Vietnamese Government to design and implement a social security system that would extend coverage progressively to excluded sectors and provide support to workers who have become unemployed as a result of the economic transition process. At its Eighth National Congress, the Vietnamese Communist Party approved a 5-year social and economic plan calling for such an expansion of the social insurance system as well as for a guaranteed standard of living for pensioners. To facilitate anticipated changes, activities that were previously divided between the Ministry of Labor, Invalids, and Social Affairs and the Vietnam General Confederation of Labor have been assigned to the newly formed Vietnam Social Insurance (VSI) Organization. Under consideration is a plan to combine some VSI activities with those of the Vietnam Health Insurance Organization. The ILO will assist with training, computerization, and social security fund investing. Noncompliance is a major obstacle to planned expansion of the social security system; about 90% of private firms are still not paying into the system. PMID:12320521

  15. Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations

    PubMed Central

    Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

    2016-01-01

    The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998–2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002–2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability. PMID:27010692

  16. Modelling Hydrologic Processes in the Mekong River Basin Using a Distributed Model Driven by Satellite Precipitation and Rain Gauge Observations.

    PubMed

    Wang, Wei; Lu, Hui; Yang, Dawen; Sothea, Khem; Jiao, Yang; Gao, Bin; Peng, Xueting; Pang, Zhiguo

    2016-01-01

    The Mekong River is the most important river in Southeast Asia. It has increasingly suffered from water-related problems due to economic development, population growth and climate change in the surrounding areas. In this study, we built a distributed Geomorphology-Based Hydrological Model (GBHM) of the Mekong River using remote sensing data and other publicly available data. Two numerical experiments were conducted using different rainfall data sets as model inputs. The data sets included rain gauge data from the Mekong River Commission (MRC) and remote sensing rainfall data from the Tropic Rainfall Measurement Mission (TRMM 3B42V7). Model calibration and validation were conducted for the two rainfall data sets. Compared to the observed discharge, both the gauge simulation and TRMM simulation performed well during the calibration period (1998-2001). However, the performance of the gauge simulation was worse than that of the TRMM simulation during the validation period (2002-2012). The TRMM simulation is more stable and reliable at different scales. Moreover, the calibration period was changed to 2, 4, and 8 years to test the impact of the calibration period length on the two simulations. The results suggest that longer calibration periods improved the GBHM performance during validation periods. In addition, the TRMM simulation is more stable and less sensitive to the calibration period length than is the gauge simulation. Further analysis reveals that the uneven distribution of rain gauges makes the input rainfall data less representative and more heterogeneous, worsening the simulation performance. Our results indicate that remotely sensed rainfall data may be more suitable for driving distributed hydrologic models, especially in basins with poor data quality or limited gauge availability. PMID:27010692

  17. Case report: intraocular gnathostomiasis in Vietnam.

    PubMed

    Xuan, Le Thi; Rojekittikhun, Wichit; Punpoowong, Benjanee; Trang, Le Nhu; Hien, Tran Vinh

    2002-09-01

    This is the report of the first case of intraocular gnathostomiasis diagnosed in Vietnam. The disease progressed in two months in two distinct phases: in the first phase, the patient had swellings, which appeared at different times and in different locations, on his face--this phase lasted around one month; the second phase was the embedding of the parasite in the vitreous cavity of the right eye and uveitis. Surgical extraction of a living Gnathostoma larva was carried out. Based on morphological, histological criteria, the larva may have been an atypical third-stage of Gnathostoma spinigerum. PMID:12693580

  18. Cutaneous fascioliasis: a case report in Vietnam.

    PubMed

    Xuan, Le Thi; Hung, Nguyen Thien; Waikagul, Jitra

    2005-05-01

    A 40 year-old woman living in Gialai, Kontum, Vietnam, developed a red solid mass in the epigastric region. From ultrasound investigation, liver abscess and myositis of the intercostal muscle was diagnosed. Two weeks after treatment with antibiotics, the mass disappeared, but a migratory track developed in the right upper quadrant of the abdomen. An aspiration of the vesicular end of the serpiginous track showed a light brown, living worm that was later identified as an immature Fasciola sp. This is the first case report of cutaneous fascioliasis in the form similar to creeping eruption. PMID:15891121

  19. Lift force of delta wings

    SciTech Connect

    Lee, M.; Ho, Chihming )

    1990-09-01

    On a delta wing, the separation vortices can be stationary due to the balance of the vorticity surface flux and the axial convection along the swept leading edge. These stationary vortices keep the wing from losing lift. A highly swept delta wing reaches the maximum lift at an angle of attack of about 40, which is more than twice as high as that of a two-dimensional airfoil. In this paper, the experimental results of lift forces for delta wings are reviewed from the perspective of fundamental vorticity balance. The effects of different operational and geometrical parameters on the performance of delta wings are surveyed.

  20. Observations on Neotricula aperta (Gastropoda: Pomatiopsidae) population densities in Thailand and central Laos: implications for the spread of Mekong schistosomiasis

    PubMed Central

    2012-01-01

    Background The snail Neotricula aperta transmits Mekong schistosomiasis in southern Laos and Cambodia, with about 1.5 million people at risk of infection. Plans are under consideration for at least 12 hydroelectric power dams on the lower Mekong river and much controversy surrounds predictions of their environmental impacts. Unfortunately, there are almost no ecological data (such as long term population trend studies) available for N. aperta which could be used in impact assessment. Predictions currently assume that the impacts will be the same as those observed in Africa (i.e., a worsening of the schistosomiasis problem); however, marked ecological differences between the snails involved suggest that region specific models are required. The present study was performed as an initial step in providing data, which could be useful in the planning of water resource development in the Mekong. Snail population density records were analyzed for populations close to, and far downstream of, the Nam Theun 2 (NT2) project in Laos in order to detect any changes that might be attributable to impoundment. Results The population immediately downstream of NT2 and that sampled 400 km downstream in Thailand both showed a long term trend of slow growth from 1992 to 2005; however, both populations showed a marked decline in density between 2005 and 2011. The decline in Thailand was to a value significantly lower than that predicted by a linear mixed model for the data, whilst the population density close to NT2 fell to undetectable levels in 2011 from densities of over 5000 m-2 in 2005. The NT2 dam began operation in 2010. Conclusions The impact of the NT2 dam on N. aperta population density could be more complex than first thought and may reflect the strict ecological requirements of this snail. There was no indication that responses of N. aperta populations to dam construction are similar to those observed with Bulinus and Schistosoma haematobium in Africa, for example. In view

  1. Forest transition in Vietnam and displacement of deforestation abroad

    PubMed Central

    Meyfroidt, Patrick; Lambin, Eric F.

    2009-01-01

    In some countries across the globe, tropical forest cover is increasing. The national-scale reforestation of Vietnam since 1992 is assumed to contribute to this recovery. It is achieved, however, by the displacement of forest extraction to other countries on the order of 49 (34–70) M m3, or ≈39% of the regrowth of Vietnam's forests from 1987 to 2006. Approximately half of wood imports to Vietnam during this period were illegal. Leakage due to policies restricting forest exploitation and displacement due to growing domestic consumption and exports contributed respectively to an estimated 58% and 42% of total displacement. Exports of wood products from Vietnam also grew rapidly, amounting to 84% of the displacement, which is a remarkable feature of the forest transition in Vietnam. Attribution of the displacement and corresponding forest extraction to Vietnam, the source countries or the final consumers is thus debatable. Sixty-one percent of the regrowth in Vietnam was, thus, not associated with displacement abroad. Policies allocating credits to countries for reducing deforestation and forest degradation should monitor illegal timber trade and take into account the policy-induced leakage of wood extraction to other countries. PMID:19805270

  2. The epidemiology of nematode and fluke infections in cattle in the Red River Delta in Vietnam.

    PubMed

    Holland, W G; Luong, T T; Nguyen, L A; Do, T T; Vercruysse, J

    2000-11-10

    Over a period of 13 months, faecal samples were collected monthly from approximately 45 cattle over 3 months of age. Additionally, 74 calves of 1-2 months were sampled to determine the presence of Toxocara vitulorum eggs. Individual egg counts and infective strongyle larvae from pooled faecal samples were examined. Post-mortem worm counts were carried out on six groups of tracer calves (n=12) that had been kept for 4 weeks on pasture in and around the village studied. The following helminths were identified: T. vitulorum, Cooperia punctata, C. pectinata, C. oncophora, Oesophagostomum radiatum, Trichostrongylus axei, T. colubriformis, Haemonchus spp., Fasciola spp. and Paramphistomum spp. In 8% of the samples collected from young calves, individual egg counts for T. vitulorum were found indicative for pathogenic worm burdens. Strongyle egg counts and worm counts indicated that transmission is low without a distinct seasonality. In animals of 3-9 months old, a strongyle egg count peak can be demonstrated which at a higher age steadily and significantly decreased. In faecal cultures Cooperia spp. were most prominent in all age groups throughout the year with the exception of the period September-November when Haemonchus spp. and Oesophagostomum spp. were most prevalent. Fasciola spp. eggs were found in 22% of the collected faecal samples and the egg counts were low indicating that the intensity of Fasciola spp. infection is mild. Based on the present data, regular anthelmintic treatments seem not to be justified, except for a single treatment at the age of 2 weeks against toxocariosis. PMID:11035232

  3. Using Shoreline Video Assessment for coastal planning and restoration in the context of climate change in Kien Giang, Vietnam

    NASA Astrophysics Data System (ADS)

    Van Cuong, Chu; Russell, Michael; Brown, Sharon; Dart, Peter

    2015-06-01

    Kien Giang, bordering Cambodia in the Mekong River Delta, is one of the two most vulnerable provinces in the region to coastal erosion and flooding. Coastal protection can conflict with current land use and economic development activities. The conditions of the mangrove forest and mainland coastline of the Kien Giang province were assessed using the Shoreline Video Assessment Method (SVAM) backed up with information from satellite images. Half of the 206 km Kien Giang coastline has been eroded or is being eroded. Protective mangrove forests naturally occurred in 74% of the coastline but have been under threat from illegal cutting, erosion and coastal retreat. Accurate information on the state of the coastline and mangrove forest health provided invaluable data for developing a new coastal rehabilitation plan to guard against future sea level rise. In contrast to the current boundary management of land and natural resources, this plan divided the provincial coastline into 19 sections based on the landscape condition and exposure to erosion. Priority strategic actions for erosion management, mangrove restoration and sustainable livelihood development for local communities for each section of coast were developed based on an integrated cross sectoral approach and practical experience in the Conservation and Development of the Kien Giang Biosphere Reserve Project.

  4. Holden Crater Delta

    NASA Technical Reports Server (NTRS)

    2006-01-01

    [figure removed for brevity, see original site] Context image for PIA03694 Holden Crater Delta

    This fan-shaped delta deposit is located in Holden Crater.

    Image information: VIS instrument. Latitude -27.3N, Longitude 324.5E. 17 meter/pixel resolution.

    Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.

    NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.

  5. Shanghai Delta Complex

    SciTech Connect

    Hart, R.E.; Hoffman, P.F.; Parker, R.W.

    1988-01-01

    The upper Eocene Yegua Formation expands dramatically across a regional system of growth faults into an area generally 12-15 km wide, extending at least from the western edge of the Houston sale dome basin to the San Marcos arch. Within this area, the expanded Yegua trend has yielded, since 1982, at least seven noteworthy discoveries: Toro Grande and Lost Bridge fields in Jackson County, and Black Owl, Shanghai, Shanghai East, El Campo, and Phase Four fields in Wharton County. During each of several postulated Yegua sea level drops, this flexure became a focal point for deltaic deposition of excellent reservoir-quality sands. Shanghai, Shanghai East, and El Campo fields are located within what the writers have labeled the ''Shanghai delta complex.'' Integration of seismic and well data in this vicinity shows a marked increase in the expansion indices of growth faults, and moderately thick progradational sand sequences have accumulated immediately downthrow. This structural-stratigraphic pattern, as well as internal bedding characteristics and other lithologic data observed, is believed typical of deltas deposited along the Yegua shelf margin.

  6. Thermostatted delta f

    SciTech Connect

    Krommes, J.A.

    2000-01-18

    The delta f simulation method is revisited. Statistical coarse-graining is used to rigorously derive the equation for the fluctuation delta f in the particle distribution. It is argued that completely collisionless simulation is incompatible with the achievement of true statistically steady states with nonzero turbulent fluxes because the variance of the particle weights w grows with time. To ensure such steady states, it is shown that for dynamically collisionless situations a generalized thermostat or W-stat may be used in lieu of a full collision operator to absorb the flow of entropy to unresolved fine scales in velocity space. The simplest W-stat can be implemented as a self-consistently determined, time-dependent damping applied to w. A precise kinematic analogy to thermostatted nonequilibrium molecular dynamics (NEMD) is pointed out, and the justification of W-stats for simulations of turbulence is discussed. An extrapolation procedure is proposed such that the long-time, steady-state, collisionless flux can be deduced from several short W-statted runs with large effective collisionality, and a numerical demonstration is given.

  7. Proposed Training Plan to Improve Building Energy Efficiency in Vietnam

    SciTech Connect

    Yu, Sha; Evans, Meredydd

    2013-01-01

    Vietnam has experienced fast growth in energy consumption in the past decade, with annual growth rate of over 12 percent. This is accompanied by the fast increase in commercial energy use, driven by rapid industrialization, expansion of motorized transport, and increasing energy use in residential and commercial buildings. Meanwhile, Vietnam is experiencing rapid urbanization at a rate of 3.4 percent per year; and the majority of the growth centered in and near major cities such as Hanoi and Ho Chi Minh City. This has resulted in a construction boom in Vietnam.

  8. Negotiating care: reproductive tract infections in Vietnam.

    PubMed

    Whittaker, Maxine

    2002-01-01

    Through case studies of two women, this paper uses a taskonomy approach to analyze rural Vietnamese women's narratives of prevention, treatment and management of vaginal discharge to illustrate care seeking, health practice and the pragmatism of their action. The research is based upon ethnographic research undertaken by the author between 1995 and 1997 in a rural district in northern Vietnam. This exploration illustrates the complexities of women's rationalities and the web of influences upon their choices-the health seeking culture as practiced. The women's narratives are also placed within the broader context of gender, power and health systems that structure their decision making. The author discusses how social and economic resource factors influence the choices women make regarding when to begin treatment for vaginal discharge and where to seek care. She concludes that women use their understanding of the relationships between health, living conditions and diseases on a day-to-day basis and that the practice of managing vaginal discharge is mediated by concepts of body, self and the body politic in Vietnam. PMID:12216991

  9. Secondary Traumatization in Vietnam Veterans' Families.

    PubMed

    Yager, Thomas J; Gerszberg, Nicole; Dohrenwend, Bruce P

    2016-08-01

    This research focused on secondary traumatization of wives and offspring of 115 male Vietnam veterans, a subsample from the National Vietnam Veterans Readjustment Study who had one or more children aged 6 to 16 years and had had a clinical interview. Traumatization was defined as meeting criteria for lifetime war-related posttraumatic stress disorder (PTSD). Secondary traumatization was operationalized by elevated scores on children's internalizing or externalizing behavior problems and on wives' demoralization. There was evidence of secondary traumatization in the veterans' sons (odds ratio [OR] = 20.31 for internalizing behavior problems). Current PTSD in the veterans was associated with demoralization in their wives or partners (β = 0.24), which in turn was associated with behavior problems in their daughters (ORs = 2.67 and 4.61 for internalizing and externalizing behavior problems, respectively; these were adjusted for veteran's PTSD). Demoralization of the wife or partner was also associated with current alcoholism in the veterans (β = 0.30, adjusting for veteran's PTSD). These associations were also adjusted for other veteran risk factors, including severity of combat exposure, involvement in harming civilians or prisoners, and prewar vulnerability. Even with the degree of secondary traumatization present, the veterans' children appeared at least as healthy as counterparts in the general population. PMID:27529559

  10. Thermometric well testing on the Vietnam offshore

    SciTech Connect

    San, T.N.; Shtyrlin, V.F.; Vakhitov, G.G.; Loi, L.M.; Listengarten, L.; Hien, D.L.

    1994-12-31

    It is impossible to control and adjust an oil and gas field development without determining the flow intervals of production wells. For that it is preferable to get production profiles by using the downhole flowmeter. There are, however, some main restrictions for wide-spread application of them on the offshore of Vietnam as follows: the flowmeter spinner velocity cannot indicate correctly in the open hole wells having a nonuniform diameter; it is unable to carry out in the case when the tubing shoe is lower than top formation on 300--500m. In this paper, the authors present a summary of temperature profile method to determine the flowing and intaking intervals of wells drilled in basement of the White Tiger Field on Vietnam offshore. For the last 2 years more than 30 wells were surveyed by this method in the above mentioned conditions. This paper presents the theory and practice of well temperature profile surveys, the concrete examples of data interpretation using the software Oiltest.

  11. Greenhouse Gas Emissions within Seasonally Flooded Tropical River Deltas

    NASA Astrophysics Data System (ADS)

    Salvador, A. K.; Schaefer, M.; Roberts, K. A.; Fendorf, S. E.; Benner, S. G.

    2015-12-01

    Soils contain the largest terrestrial carbon pool on Earth, and approximately one-third of soil carbon is stored in the tropics. Gas exchange between soil and the atmosphere occurs largely as a result of microbial degradation (mineralization) of organic carbon. The rate of soil organic matter (SOM) mineralization is determined by a combination of climatic factors and soil ecosystem properties, which dictate the dominant metabolic pathway(s) within soil at a given time; major changes in metabolic rate are particularly pronounced between aerobic and anaerobic mineralization. Here we assessed the impact of soil moisture, a major factor determining soil anaerobiosis, on greenhouse gas fluxes in a tropical, seasonally flooded wetland in the Mekong Delta. We monitored CO2, CH4, and N2O gas fluxes, porewater chemistry, and soil moisture content in a seasonal wetland. Additionally, we collected wetland soil cores (10 cm diameter) and manipulated them in the laboratory, allowing us to control soil moisture and drying rates, and to simulate multiple periods of wetting and drying. During drying, CH4 fluxes within the wetland initially increase to a maximum before decreasing as soil moisture decreases and oxygen diffusion into the soil increases. Maximum CH4 fluxes vary with moisture content, but the wettest sites produced fluxes >1000 mg C m-2 d-1 for short periods of time. As drying continues, CH4 fluxes decrease to nearly zero, and N2O fluxes begin to increase to ~3 mg N m-2 d-1 but do not appear to have reached a maximum before sampling ceased. Gas flux from soil core incubations (n=5) exhibit trends and values similar to field measurements. CH4 fluxes initially increase and reach >1000 mg C m-2 d-1 in cores while N2O fluxes reach up to 10 mg N m-2 d-1 and decrease with continued drying. CO2 fluxes in both field and laboratory are sustained until near desiccated conditions. Seasonal wetlands are characteristic of large tropical deltas. Our findings provide a means to

  12. 78 FR 8107 - Certain Steel Wire Garment Hangers From the Socialist Republic of Vietnam: Countervailing Duty Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-02-05

    ... Countervailing Duty Determination and Final Affirmative Critical Circumstances Determination, 77 FR 75973... International Trade Administration Certain Steel Wire Garment Hangers From the Socialist Republic of Vietnam... order on certain steel wire garment hangers from the Socialist Republic of Vietnam (Vietnam)....

  13. Perspective: Towards environmentally acceptable criteria for downstream fish passage through mini hydro and irrigation infrastructure in the Lower Mekong River Basin

    SciTech Connect

    Baumgartner, Lee J.; Deng, Zhiqun; Thorncraft, Garry; Boys, Craig A.; Brown, Richard S.; Singhanouvong, Douangkham; Phonekhampeng, Oudom

    2014-02-26

    Tropical rivers have high annual discharges optimal for hydropower and irrigation development. The Mekong River is one of the largest tropical river systems, supporting a unique mega-diverse fish community. Fish are an important commodity in the Mekong, contributing a large proportion of calcium, protein, and essential nutrients to the diet of the local people and providing a critical source of income for rural households. Many of these fish migrate not only upstream and downstream within main-channel habitats but also laterally into highly productive floodplain habitat to both feed and spawn. Most work to date has focused on providing for upstream fish passage, but downstream movement is an equally important process to protect. Expansion of hydropower and irrigation weirs can disrupt downstream migrations and it is important to ensure that passage through regulators or mini hydro systems is not harmful or fatal. Many new infrastructure projects (<6 m head) are proposed for the thousands of tributary streams throughout the Lower Mekong Basin and it is important that designs incorporate the best available science to protect downstream migrants. Recent advances in technology have provided new techniques which could be applied to Mekong fish species to obtain design criteria that can facilitate safe downstream passage. Obtaining and applying this knowledge to new infrastructure projects is essential in order to produce outcomes that are more favorable to local ecosystems and fisheries.

  14. Land Use and Water Quality Along a Mekong Tributary in Northern Lao P.D.R.

    NASA Astrophysics Data System (ADS)

    Ribolzi, Olivier; Cuny, Juliette; Sengsoulichanh, Phonexay; Mousquès, Claire; Soulileuth, Bounsamai; Pierret, Alain; Huon, Sylvain; Sengtaheuanghoung, Oloth

    2011-02-01

    Improving access to clean water has the potential to make a major contribution toward poverty reduction in rural communities of Lao P.D.R. This study focuses on stream water quality along a Mekong basin tributary, the Houay Xon that flows within a mountainous, mosaic land-use catchment of northern Lao P.D.R. To compare direct water quality measurements to the perception of water quality within the riparian population, our survey included interviews of villagers. Water quality was found to vary greatly depending on the location along the stream. Overall, it reflected the balance between the stream self-cleaning potential and human pressure on the riparian zone: (i) high bacteria and suspended load levels occurred where livestock are left to free-range within the riparian zone; (ii) very low oxygen content and high bacteriological contamination prevailed downstream from villages; (iii) high concentrations of bacteria were consistently observed along urbanized banks; (iv) low oxygen content were associated with the discharge of organic-rich wastewater from a small industrial plant; (v) very high suspended load and bacteria levels occurred during flood events due to soil erosion from steep cultivated hill slopes. Besides these human induced pollutions we also noted spontaneous enrichments in metals in wetland areas fed by dysoxic groundwater. These biophysical measurements were in agreement with the opinions expressed by the majority of the interviewees who reported poor and decreasing water quality in the Houay Xon catchment. Based on our survey, we propose recommendations to improve or maintain stream water quality in the uplands of northern Lao P.D.R.

  15. The disappearing Environmental Kuznets Curve: a study of water quality in the Lower Mekong Basin (LMB).

    PubMed

    Wong, Yoon Loong Andrew; Lewis, Lynne

    2013-12-15

    The literature is flush with articles focused on estimating the Environmental Kuznets Curve (EKC) for various pollutants and various locations. Most studies have utilized air pollution variables; far fewer have utilized water quality variables, all with mixed results. We suspect that mixed evidence of the EKC stems from model and error specification. We analyze annual data for four water quality indicators, three of them previously unstudied - total phosphorus (TOTP), dissolved oxygen (DO), ammonium (NH4) and nitrites (NO2) - from the Lower Mekong Basin region to determine whether an Environmental Kuznets Curve (EKC) is evident for a transboundary river in a developing country and whether that curve is dependent on model specification and/or pollutant. We build upon previous studies by correcting for the problems of heteroskedasticity, serial correlation and cross-sectional dependence. Unlike multi-country EKC studies, we mitigate for potential distortion from pooling data across geographically heterogeneous locations by analyzing data drawn from proximate locations within a specific international river basin in Southeast Asia. We also attempt to identify vital socioeconomic determinants of water pollution by including a broad list of explanatory variables alongside the income term. Finally, we attempt to shed light on the pollution-income relationship as it pertains to trans-boundary water pollution by examining data from an international river system. We do not find consistent evidence of an EKC for any of the 4 pollutant indicators in this study, but find the results are entirely dependent on model and error specification as well as pollutant. PMID:24211570

  16. Evaluation of Mekong River commission operational flood forecasts, 2000-2012

    NASA Astrophysics Data System (ADS)

    Pagano, T. C.

    2014-07-01

    This study created a 13-year historical archive of operational flood forecasts issued by the Regional Flood Management and Mitigation Center (RFMMC) of the Mekong River Commission. The RFMMC issues 1- to 5-day daily deterministic river height forecasts for 22 locations throughout the wet season (June-October). When these forecasts reach near flood level, government agencies and the public are encouraged to take protective action against damages. When measured by standard skill scores, the forecasts perform exceptionally well (e.g., 1 day-ahead Nash-Sutcliffe > 0.99) although much of this apparent skill is due to the strong seasonal cycle and the narrow natural range of variability at certain locations. Five-day forecasts upstream of Phnom Penh typically have 0.8 m error standard deviation, whereas below Phnom Penh the error is typically 0.3 m. The coefficients of persistence for 1-day forecasts are typically 0.4-0.8 and 5-day forecasts are typically 0.1-0.7. RFMMC uses a series of benchmarks to define a metric of percentage satisfactory forecasts. As the benchmarks were derived based on the average error, certain locations and lead times consistently appear less satisfactory than others. Instead, different benchmarks were proposed and derived based on the 70th percentile of absolute error over the 13-year period. There are no obvious trends in the percentage of satisfactory forecasts from 2002 to 2012, regardless of the benchmark chosen. Finally, when evaluated from a categorical "crossing above/not-crossing above flood level" perspective, the forecasts have a moderate probability of detection (48% at 1 day ahead, 31% at 5 days ahead) and false alarm rate (13% at 1 day ahead, 74% at 5 days ahead).

  17. Current status of arsenic exposure and social implication in the Mekong River basin of Cambodia.

    PubMed

    Phan, Kongkea; Kim, Kyoung-Woong; Huoy, Laingshun; Phan, Samrach; Se, Soknim; Capon, Anthony Guy; Hashim, Jamal Hisham

    2016-06-01

    To evaluate the current status of arsenic exposure in the Mekong River basin of Cambodia, field interview along with urine sample collection was conducted in the arsenic-affected area of Kandal Province, Cambodia. Urine samples were analyzed for total arsenic concentrations by inductively coupled plasma mass spectrometry. As a result, arsenicosis patients (n = 127) had As in urine (UAs) ranging from 3.76 to 373 µg L(-1) (mean = 78.7 ± 69.8 µg L(-1); median = 60.2 µg L(-1)). Asymptomatic villagers (n = 108) had UAs ranging from 5.93 to 312 µg L(-1) (mean = 73.0 ± 52.2 µg L(-1); median = 60.5 µg L(-1)). About 24.7 % of all participants had UAs greater than 100 µg L(-1) which indicated a recent arsenic exposure. A survey found that females and adults were more likely to be diagnosed with skin sign of arsenicosis than males and children, respectively. Education level, age, gender, groundwater drinking period, residence time in the village and amount of water drunk per day may influence the incidence of skin signs of arsenicosis. This study suggests that residents in Kandal study area are currently at risk of arsenic although some mitigation has been implemented. More commitment should be made to address this public health concern in rural Cambodia. PMID:26298061

  18. Linking ecology to hydrology and geomorphology using river reach classification for the Greater Mekong Region

    NASA Astrophysics Data System (ADS)

    Ouelette Dallaire, Camille; Lehner, Bernhard

    2016-04-01

    Large-scale development projects, such as hydropower dams, in the Greater Mekong Region (GMR) are putting high pressure on freshwater resources. Environmental impact assessments are needed in the region to understand the possible impacts of these projects. These assessments often require biodiversity data that can be costly to acquire both in terms of time and money. It is often assumed that river or ecosystem classes, based on geo-physical characteristics, can be used as biodiversity proxies in large scale assessments to account for a lack of biodiversity data. However, there has been little research to compare the spatial distribution of river classes and fish species. It is unclear how well river classes are able to represent the distribution of fish and, more generally, biodiversity. To address this question, a set of two classifications were compared to a newly available dataset of fish species distribution in the GMR (Allen et al., 2012). The classifications were derived from two different methods to test which could potentially better represent fish assemblages. The first classification is derived using regional expert knowledge and the second using K-mean analysis. Both are using the same geophysical datasets. The two datasets were used in a Redundancy Analysis (RDA) to calculate which proportion of the variability in the fish species data can be explained by the river classes. The RDA resulted in R2 of 0.44 for the supervised classification and 0.41for the statistical classification, showing a moderate correlation between the datasets. Based on these results, using river classes as biodiversity proxy is deemed reasonable. However, some of the variability in the distribution of fish species cannot be related simply to geophysical factors. River classes may capture different elements such as unique habitats and associated, possibly unknown, endemic species that indices based only on biological data do not. Hence, river classes can be a good alternative and

  19. Evaluation of Mekong River Commission operational flood forecasts, 2000-2012

    NASA Astrophysics Data System (ADS)

    Pagano, T. C.

    2013-11-01

    This study created a 13 yr historical archive of operational flood forecasts issued by the Regional Flood Management and Mitigation Center (RFMMC) of the Mekong River Commission. The RFMMC issues 1 to 5 day-ahead daily deterministic river height forecasts for 22 locations throughout the wet season (June-October). When these forecasts reach near Flood Level, government agencies and the public are encouraged to take protective action against damages. When measured by standard skill scores, the forecasts perform exceptionally well (e.g. 1 day-ahead Nash-Sutcliffe > 0.99) although much of this apparent skill is due to the strong seasonal cycle and the narrow natural range of variability at certain locations. 5 day-ahead forecasts upstream of Phnom Penh typically have 0.8 m error standard deviation, whereas below Phnom Penh the error is typically 0.3 m. The Coefficients of Persistence for 1 day-ahead forecasts are typically 0.4-0.8 and 5 day-ahead forecasts are typically 0.1-0.7. RFMMC uses a series of benchmarks to define a metric of Percentage Satisfactory forecasts. As the benchmarks were derived based on the average error, certain locations and lead-times consistently appear less satisfactory than others. Instead, different benchmarks were proposed and derived based on the 70th percentile of absolute error over the 13 yr period. There are no obvious trends in the Percentage of Satisfactory forecasts from 2002-2012, regardless of the benchmark chosen. Finally, when evaluated from a categorical "crossing above/not-crossing above flood level" perspective, the forecasts have a moderate probability of detection (48% at 1 day-ahead, 31% at 5 day-ahead) and false alarm rate (13% at 1 day-ahead, 74% at 5 days-ahead).

  20. Delta Electroproduction in 12-C

    SciTech Connect

    Steven McLauchlan

    2003-01-31

    The Delta-nucleus potential is a crucial element in the understanding of the nuclear system. Previous electroexcitation measurements in the delta region reported a Q2 dependence of the delta mass indicating that this potential is dependent on the momentum of the delta. Such a dependence is not observed for protons and neutrons in the nuclear medium. This thesis presents the experimental study of the electroexcitation of the delta resonance in 12C, performed using the high energy electron beam at the Thomas Jefferson National Accelerator Facility, and the near 4(pie) acceptance detector CLAS that enables the detection of the full reaction final state. Inclusive, semi inclusive, and exclusive cross sections were measured with an incident electron beam energy of 1.162GeV over the Q2 range 0.175-0.475 (GeV/c)2. A Q2 dependence of the delta mass was only observed in the exclusive measurements indicating that the delta-nucleus potential is affected by the momentum of the delta.

  1. Magnetic minerals in three Asian rivers draining into the South China Sea: Pearl, Red, and Mekong Rivers

    NASA Astrophysics Data System (ADS)

    Kissel, Catherine; Liu, Zhifei; Li, Jinhua; Wandres, Camille

    2016-05-01

    The use of the marine sedimentary magnetic properties, as tracers for changes in precipitation rate and in oceanic water masses transport and exchanges, implies to identify and to characterize the different sources of the detrital fraction. This is of particular importance in closed and/or marginal seas such as the South China Sea. We report on the magnetic properties of sedimentary samples collected in three main Asian rivers draining into the South China Sea: the Pearl, Red, and Mekong Rivers. The geological formations as well as the present climatic conditions are different from one catchment to another. The entire set of performed magnetic analyses (low-field magnetic susceptibility, ARM acquisition and decay, IRM acquisition and decay, back-field acquisition, thermal demagnetization of three-axes IRM, hysteresis parameters, FORC diagrams, and low-temperature magnetic measurements) allow us to identify the magnetic mineralogy and the grain-size distribution when magnetite is dominant. Some degree of variability is observed in each basin, illustrating different parent rocks and degree of weathering. On average it appears that the Pearl River is rich in magnetite along the main stream while the Mekong River is rich in hematite. The Red River is a mixture of the two. Compared to clay mineral assemblages and major element contents previously determined on the same samples, these new findings indicate that the magnetic fraction brings complementary information of great interest for environmental reconstructions based on marine sediments from the South China Sea.

  2. Raw attitudes, wetland cultures, life-cycles: socio-cultural dynamics relating to Opisthorchis viverrini in the Mekong Basin.

    PubMed

    Grundy-Warr, Carl; Andrews, Ross H; Sithithaworn, Paiboon; Petney, Trevor N; Sripa, Banchop; Laithavewat, Luxana; Ziegler, Alan D

    2012-03-01

    Opisthorchis viverrini is one of the most common and medically important food-borne parasites in the Lower Mekong area of Southeast Asia. As we learn more about its ecology, pathology and epidemiology we see the need to consider more deeply the socio-cultural dynamics with which food-borne species complexes are associated. This paper argues that the Mekong region is characterized by strong livelihoods and life-style associations within wetland ecosystems, which are inseparable from human eating habits ("raw attitudes"). Within the fish-rice economies of the region there are many long-cherished food cultures based on eating raw, semi-cooked and fermented fish dishes, which are known to lead to opisthorchiasis, and potentially cholangiocarcinoma. This paper examines evidence from northeast Thailand showing that dedicated health outreach campaigns do help to reduce prevalence of opisthorchiasis over time. For disease prevention and health education approaches to be most effective, they must be sensitive to culture, livelihood economics, gender, and age. Further integrative, inter-disciplinary and international research must incorporate the complex dynamics of parasite ecology, human behavior, socio-economics, and public health awareness. PMID:21712097

  3. Colorado River Delta

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Colorado River ends its 2330 km journey in the Gulf of Mexico in Baja California. The heavy use of the river as an irrigation source for the Imperial Valley has dessicated the lower course of the river in Mexico such that it no longer consistently reaches the sea. Prior to the mid 20th century, the Colorado River Delta provided a rich estuarine marshland that is now essentially desiccated, but nonetheless is an important ecological resource.

    The image was acquired May 29, 2006, covers an area of 44.3 x 57.5 km, and is located at 32.1 degrees north latitude, 115.1 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  4. Mackenzie River Delta, Canada

    NASA Technical Reports Server (NTRS)

    2007-01-01

    The Mackenzie River in the Northwest Territories, Canada, with its headstreams the Peace and Finley, is the longest river in North America at 4241 km, and drains an area of 1,805,000 square km. The large marshy delta provides habitat for migrating Snow Geese, Tundra Swans, Brant, and other waterfowl. The estuary is a calving area for Beluga whales. The Mackenzie (previously the Disappointment River) was named after Alexander Mackenzie who travelled the river while trying to reach the Pacific in 1789.

    The image was acquired on August 4, 2005, covers an area of 55.8 x 55.8 km, and is located at 68.6 degrees north latitude, 134.7 degrees west longitude.

    The U.S. science team is located at NASA's Jet Propulsion Laboratory, Pasadena, Calif. The Terra mission is part of NASA's Science Mission Directorate.

  5. Design and methods of the national Vietnam veterans longitudinal study.

    PubMed

    Schlenger, William E; Corry, Nida H; Kulka, Richard A; Williams, Christianna S; Henn-Haase, Clare; Marmar, Charles R

    2015-09-01

    The National Vietnam Veterans Longitudinal Study (NVVLS) is the second assessment of a representative cohort of US veterans who served during the Vietnam War era, either in Vietnam or elsewhere. The cohort was initially surveyed in the National Vietnam Veterans Readjustment Study (NVVRS) from 1984 to 1988 to assess the prevalence, incidence, and effects of post-traumatic stress disorder (PTSD) and other post-war problems. The NVVLS sought to re-interview the cohort to assess the long-term course of PTSD. NVVLS data collection began July 3, 2012 and ended May 17, 2013, comprising three components: a mailed health questionnaire, a telephone health survey interview, and, for a probability sample of theater Veterans, a clinical diagnostic telephone interview administered by licensed psychologists. Excluding decedents, 78.8% completed the questionnaire and/or telephone survey, and 55.0% of selected living veterans participated in the clinical interview. This report provides a description of the NVVLS design and methods. Together, the NVVRS and NVVLS constitute a nationally representative longitudinal study of Vietnam veterans, and extend the NVVRS as a critical resource for scientific and policy analyses for Vietnam veterans, with policy relevance for Iraq and Afghanistan veterans. PMID:26096554

  6. United States national security policy making and Vietnam

    SciTech Connect

    Davidson, M.W.

    1985-01-01

    The United States failed to achieve its goals in waging a war in Vietnam. This thesis endeavors to show that this failure was due to errors in the formulation of American national security policy regarding Vietnam. The policy making process went astray, at least in part, due to a narrowing of the role of senior military officers as national security policy makers. The restricted role of senior officers as national security policy makers adversely affected American policy formulation regarding Vietnam. The United States response to the coup against Diem in 1963 and the deployment of conventional American forces to ground combat in Vietnam, in 1965 were undertaken without a clear recognition of the considerable costs of the commitments being assumed. Senior military officers had prompted such a recognition in similar previous crises but were not in a policy making position to do so concerning Vietnam. The policymaking input that was absent was ethical counsel of a fundamental nature. Clausewitz viewed the mortality of a war as being embodied in the national will to fight that war. The absence of an accurate appreciation of the costs of a military solution in Vietnam denied civilian officials a critical policy making factor and contributed significantly to the defeat of the American purpose there.

  7. Artificial delta growth

    NASA Astrophysics Data System (ADS)

    Mikeš, Daniel

    2010-05-01

    A deltaic sedimentary system has a point source; sediment is carried over the delta plain by distributary channels away from the point source and deposited at the delta front by distributary mouth bars. The established methods to describe such a sedimentary system are "bedding analysis", "facies analysis", and "basin analysis". We shall call the ambient conditions "input" and the rock record "output". There exist a number of methods to deduce input from output, e.g. "Sequence stratigraphy" (a.o. Vail et al. 1977, Catuneanu et al. 2009), "Shoreline trajectory" (a.o. Helland-Hansen & Martinsen 1996, Helland-Hansen & Hampson 2009) on the one hand and the complex use of established techniques on the other (a.o. Miall & Miall 2001, Miall & Miall 2002). None of these deductive methods seems to be sufficient. I claim that the common errors in all these attempts are the following: (1) a sedimentary system is four-dimensional (3+1) and a lesser dimensional analysis is insufficient; (2) a sedimentary system is complex and any empirical/deductive analysis is non-unique. The proper approach to the problem is therefore the theoretical/inductive analysis. To that end we performed six scenarios of a scaled version of a passive margin delta in a flume tank. The scenarios have identical stepwise tectonic subsidence and semi-cyclic sealevel, but different supply curves, i.e. supply is: constant, highly-frequent, proportional to sealevel, inversely proportional to sealevel, lagging to sealevel, ahead of sealevel. The preliminary results are indicative. Lobe-switching occurs frequently and hence locally sedimentation occurs shortly and hiatuses are substantial; therefore events in 2D (+1) cross-sections don't correlate temporally. The number of sedimentary cycles disequals the number of sealevel cycles. Lobe-switching and stepwise tectonic subsidence cause onlap/transgression. Erosional unconformities are local diachronous events, whereas maximum flooding surfaces are regional

  8. Delta spots and great flares

    NASA Technical Reports Server (NTRS)

    Zirin, Harold; Liggett, Margaret A.

    1987-01-01

    The development of delta spots and the great flares they produce are reviewed based on 18 years of observations. Delta groups are found to develop in three ways: (1) by the eruption of a single complex active region formed below the surface; (2) by the eruption of large satellite spots near a large older spot; and (3) by the collision of spots of opposite polarity from different dipoles. It is shown that the present sample of 21 delta spots never separate once they lock together, and that the driving force for the shear is spot motion. Indicators for the prediction of the occurrence of great flares are identified.

  9. A review of the present status of lymphatic filariasis in Vietnam.

    PubMed

    Meyrowitsch, D W; Nguyen, D T; Hoang, T H; Nguyen, T D; Michael, E

    1998-07-30

    Establishing the current status of an infectious disease forms the starting point of any attempt at parasite control. Although data on the prevalence and distribution of lymphatic filariasis exist for Vietnam from the early 1900s, the present situation regarding the disease is less well-known. Here, we review the results of recent surveys conducted by the Institute of Malariology, Parasitology and Entomology, Hanoi, to update the existing information on filariasis epidemiology and distribution for this country. The present results are from surveys carried out on some 135,000 individuals in 24 provinces of Vietnam. The highest prevalences of microfilaraemia (primarily Brugia malayi ) are observed in lowland areas of the Red River Delta and in Quang-binh Province where the survey results show microfilaraemia (mf) prevalences in the range of 0.9-5.5%. The most common type of chronic clinical manifestation is shown to be leg elephantiasis. A significant finding is that an overall decrease in mf prevalence was observed to occur in five communities which were surveyed twice over an 11-21-year period, even though no interventions were carried out between the two surveys. The changes are probably caused by environmental changes, such as increased standards of housing and drainage. Studies on the effect of selective chemotherapy and mass chemotherapy using diethylcarbamazine showed reductions in community mf prevalences of 69 and 72-88%, respectively. Furthermore, cats do not appear to represent significant reservoirs of infection. These findings of geographical restriction of infection, effective and well-tolerated drug therapy, low significance of animal reservoirs, together with the existence of an effective national health network, suggest a good prognosis for the control of filariasis in this country. PMID:9777718

  10. Impact of milk consumption on performance and health of primary school children in rural Vietnam.

    PubMed

    Lien, Do Thi Kim; Nhung, Bui Thi; Khan, Nguyen Cong; Hop, Le Thi; Nga, Nguyen Thi Quynh; Hung, Nguyen Tri; Kiers, Jeroen; Shigeru, Yamamoto; te Biesebeke, Rob

    2009-01-01

    This is a follow-up study to an investigation on the prevalence of malnutrition and micronutrient deficiencies among Vietnamese primary schoolchildren. A total of 454 children aged 7 to 8 years attending three primary schools in the Northern delta province of Vietnam were either provided with regular milk, milk fortified with vitamins, minerals and inulin or served as a reference control group. Children were monitored for anthropometrics, (micro)-nutritional status, faecal microbiota composition, school performance, and health indices. Both weight-for-age (WAZ) and height-for-age (HAZ) significantly improved during 6 months of milk intervention; and underweight and stunting dropped by 10% in these groups. During intervention the incidence of anemia decreased and serum ferritin levels increased significantly in all groups. Serum zinc levels increased and consequently the incidence of zinc deficiency improved significantly in all three groups. Serum retinol levels and urine iodine levels remained stable upon intervention with fortified milk whereas in the control group the incidence of iodine deficiency increased. Bifidobacteria composed less than 1% of the total faecal bacteria. After three months of milk intervention total bacteria, bifidobacteria and Bacteroides sp. increased significantly in both milk and inulin fortified milk groups. Children in the milk consuming groups had significantly better short-term memory scores. Parent reported that health related quality of life status significantly improved upon milk intervention. In conclusion, (fortified) milk consumption benefited the children in rural Vietnam including lowering the occurrence of underweight and stunting, improving micronutrients status and better learning indicators as well as improving the quality of life. PMID:19786380

  11. 75 FR 23670 - Polyethylene Retail Carrier Bags from the Socialist Republic of Vietnam: Countervailing Duty Order

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-05-04

    ... Bags from the Socialist Republic of Vietnam: Final Affirmative Countervailing Duty Determination, 75 FR..., 74 FR 45811 (September 4, 2009) (Preliminary Determination). Therefore, the Department will direct... Vietnam: Countervailing Duty Order AGENCY: Import Administration, International Trade...

  12. Delta-9 desaturase from sharpshooters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Genomic analyses of several leafhoppers identified the first leafhopper delta-9 desaturase. Identification of important gene transcripts within insect pests permits them to be targeted with RNA interference, RNAi, strategies. The glassy-winged sharpshooter, GWSS (Hemiptera: Cicadellidae; Homalodis...

  13. Assessment of long-term channel changes in the Mekong River using remote sensing and a channel-evolution model

    NASA Astrophysics Data System (ADS)

    Miyazawa, N.

    2011-12-01

    River-channel changes are a key factor affecting physical, ecological and management issues in the fluvial environment. In this study, long-term channel changes in the Mekong River were assessed using remote sensing and a channel-evolution model. A channel-evolution model for calculating long-term channel changes of a measndering river was developed using a previous fluid-dynamic model [Zolezzi and Seminara, 2001], and was applied in order to quantify channel changes of two meandering reaches in the Mekong River. Quite few attempts have been made so far to combine remote sensing observation of meandering planform change with the application of channel evolution models within relatively small-scale gravel-bed systems in humid temperate regions. The novel point of the present work is to link state-of-art meandering planform evolution model with observed morphological changes within large-scale sand-bed rivers with higher bank height in tropical monsoonal climate regions, which are the highly dynamic system, and assess the performance. Unstable extents of the reaches could be historically identified using remote-sensing technique. The instability caused i) bank erosion and accretion of meander bends and ii) movement or development of bars and changes in the flow around the bars. The remote sensing measurements indicate that maximum erosion occurred downstream of the maximum curvature of the river-center line in both reaches. The model simulations indicates that under the mean annual peak discharge the maximum of excess longitudinal velocity near the banks occurs downstream of the maximum curvature in both reaches. The channel migration coefficients of the reaches were calibrated by comparing remote-sensing measurements and model simulations. The diffrence in the migration coefficients between both reaches depends on the diffrence in bank height rather than the geotechnical properties of floodplain sediments. Possible eroded floodplain areas and accreted floodplain

  14. Supersonic aerodynamics of delta wings

    NASA Technical Reports Server (NTRS)

    Wood, Richard M.

    1988-01-01

    Through the empirical correlation of experimental data and theoretical analysis, a set of graphs has been developed which summarize the inviscid aerodynamics of delta wings at supersonic speeds. The various graphs which detail the aerodynamic performance of delta wings at both zero-lift and lifting conditions were then employed to define a preliminary wing design approach in which both the low-lift and high-lift design criteria were combined to define a feasible design space.

  15. Three new species of the water strider genus Rhyacobates Esaki, 1923 (Hemiptera: Gerridae) from Vietnam.

    PubMed

    Tran, A D; Nguyen, X Q

    2016-01-01

    Three new species: Rhyacobates zetteli sp.n., R. angustus sp.n., and R. constrictus sp.n., all from mountainous areas of northern Vietnam, are described. With these new taxa, a total of six species of Rhyacobates has been recorded from       Vietnam. A key to species of Rhyacobates occurring in Vietnam is provided. PMID:27395239

  16. Making History Come Alive with the Nonfiction Literature of the Vietnam War.

    ERIC Educational Resources Information Center

    Johannessen, Larry R.

    2003-01-01

    Considers student response to nonfiction Vietnam War literature and discusses why students should study Vietnam War nonfiction. Presents strategies for teaching nonfiction Vietnam War literature. Presents follow-up research and writing activities that are designed to enable students to connect reading, writing, and thinking. Concludes that the…

  17. 76 FR 16384 - Certain Frozen Warmwater Shrimp From the Socialist Republic of Vietnam: Extension of Preliminary...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-03-23

    ... Shipper Review, 75 FR 60730 (October 1, 2010). The preliminary results of this review are currently due no... International Trade Administration Certain Frozen Warmwater Shrimp From the Socialist Republic of Vietnam... warmwater shrimp (``shrimp'') from the Socialist Republic of Vietnam (``Vietnam''). The period of review...

  18. 38 CFR 21.5020 - Post-Vietnam era veterans' educational assistance.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 38 Pensions, Bonuses, and Veterans' Relief 2 2010-07-01 2010-07-01 false Post-Vietnam era veterans... AFFAIRS (CONTINUED) VOCATIONAL REHABILITATION AND EDUCATION Post-Vietnam Era Veterans' Educational Assistance Under 38 U.S.C. Chapter 32 General § 21.5020 Post-Vietnam era veterans' educational...

  19. 75 FR 20563 - Certain Frozen Warmwater Shrimp from the Socialist Republic of Vietnam: Extension of Final...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-04-20

    ..., 75 FR 3446 (January 21, 2010) (``Preliminary Rescission''). The final results of this review are... International Trade Administration Certain Frozen Warmwater Shrimp from the Socialist Republic of Vietnam... warmwater shrimp (``shrimp'') from the Socialist Republic of Vietnam (``Vietnam''). This review covers...

  20. Stratification and the Emergence of the Postsecondary Private Education Sector in Vietnam

    ERIC Educational Resources Information Center

    Goyette, Kimberly Ann

    2012-01-01

    Vietnam has a strong public postsecondary education sector that has only recently begun to experience growth in nonpublic institutions. I investigate how the growth of nonpublic institutions may be related to stratification in Vietnam. I find that these institutions are more likely to serve more advantaged students from South Vietnam. Students pay…

  1. "Never Forget the Sacrifice:" A Visit to Chu Van An High School in Hanoi, Vietnam.

    ERIC Educational Resources Information Center

    Berman, David M.

    1995-01-01

    Reports on a 1993 study tour of Vietnam by educators. Discusses the role of a secondary school during the struggle against French colonialism and the U.S.-Vietnam War. Argues that educators must acknowledge the humanity of the Vietnamese as the first step in designing Vietnam-related social studies curriculum. (CFR)

  2. The Assessment of Post-Traumatic Stress Disorder among Minority Vietnam Veterans.

    ERIC Educational Resources Information Center

    LaDue, Robin A.

    Vietnam veterans from racial or ethnic minority groups have a "double minority" status; clinicians treating these veterans should distinguish between behaviors resulting from experiences in Vietnam and those due to experiences as members of minority groups. Post-Traumatic Stress Disorder (PTSD) affects an estimated 20% of all Vietnam veterans and…

  3. The flood pulse as the underlying driver of vegetation in the largest wetland and fishery of the Mekong Basin.

    PubMed

    Arias, Mauricio E; Cochrane, Thomas A; Norton, David; Killeen, Timothy J; Khon, Puthea

    2013-11-01

    The Tonle Sap is the largest wetland in Southeast Asia and one of the world's most productive inland fisheries. The Mekong River inundates the Tonle Sap every year, shaping a mosaic of natural and agricultural habitats. Ongoing hydropower development, however, will dampen the flood pulse that maintains the Tonle Sap. This study established the current underlying relationship among hydrology, vegetation, and human use. We found that vegetation is strongly influenced by flood duration; however, this relationship was heavily distorted by fire, grazing, and rice cultivation. The expected flood pulse alteration will result in higher water levels during the dry season, permanently inundating existing forests. The reduction of the maximum flood extent will facilitate agricultural expansion into natural habitats. This study is the most comprehensive field survey of the Tonle Sap to date, and it provides fundamental knowledge needed to understand the underlying processes that maintain this important wetland. PMID:23877417

  4. Sister Lab Program Prospective Partner Nuclear Profile: Vietnam

    SciTech Connect

    Bissani, M; Tyson, S

    2006-12-14

    Vietnam's nuclear program began in the 1960s with the installation at Dalat of a 250 kW TRIGA Mk-II research reactor under the U.S. Atoms for Peace Program. The reactor was shut down and its core removed only a few years later, and the nuclear research program was suspended until after the end of the civil war in the late 1970s. The Soviet Union assisted Vietnam in restoring the Dalat reactor to an operational status in 1984, trained a cadre of scientific and technical staff in its operation, and contributed to the development of nuclear science for the medical and agricultural sectors. In the agricultural area in particular, Vietnamese experts have been very successful in developing mutant strains of rice, and continue to work with the IAEA to yield strains that have a shorter growing period, increased resistance to disease, and other desirable characteristics. Rice has always been the main crop in Vietnam, but technical cooperation with the IAEA and other states has enabled the country to become one of the top rice producers in the world, exporting much of its annual crop to over two dozen countries annually. More recently, Vietnam's government has shown increasing interest in developing a civil nuclear program to supplement its fossil fuel and other energy resources. Projections from a variety of open sources, ranging from the IAEA, the U.S. Department of Energy's Energy Information Administration (EIA), the Vietnamese government, energy corporations, and think tanks all predict a massive increase in energy consumption--especially electricity--within Vietnam and the region as a whole. This growth in consumption will require a corresponding increase in energy production, which in Vietnam is currently satisfied mainly by fossil fuels (coal) and renewable energy (hydropower and biomass); Vietnam has a refining capacity of about 800 barrels/day. Most of its crude oil is exported to generate export income, and is not used to generate electricity. Although Vietnam is

  5. Implementation of forest cover and carbon mapping in the Greater Mekong subregion and Malaysia project - A case study of Thailand

    NASA Astrophysics Data System (ADS)

    Pungkul, S.; Suraswasdi, C.; Phonekeo, V.

    2014-02-01

    The Great Mekong Subregion (GMS) contains one of the world's largest tropical forests and plays a vital role in sustainable development and provides a range of economic, social and environmental benefits, including essential ecosystem services such as climate change mitigation and adaptation. However, the forest in this Subregion is experiencing deforestation rates at high level due to human activities. The reduction of the forest area has negative influence to the environmental and natural resources issues, particularly, more severe disasters have occurred due to global warming and the release of the greenhouse gases. Therefore, in order to conduct forest management in the Subregion efficiently, the Forest Cover and Carbon Mapping in Greater Mekong Subregion and Malaysia project was initialized by the Asia-Pacific Network for Sustainable Forest Management and Rehabilitation (APFNet) with the collaboration of various research institutions including Institute of Forest Resource Information Technique (IFRIT), Chinese Academy of Forestry (CAF) and the countries in Sub region and Malaysia comprises of Cambodia, the People's Republic of China (Yunnan province and Guangxi province), Lao People's Democratic Republic, Malaysia, Myanmar, Thailand, and Viet Nam. The main target of the project is to apply the intensive use of recent satellite remote sensing technology, establishing regional forest cover maps, documenting forest change processes and estimating carbon storage in the GMS and Malaysia. In this paper, the authors present the implementation of the project in Thailand and demonstrate the result of forest cover mapping in the whole country in 2005 and 2010. The result of the project will contribute towards developing efficient tools to support decision makers to clearly understand the dynamic change of the forest cover which could benefit sustainable forest resource management in Thailand and the whole Subregion.

  6. Arsenic contamination in the food chain and its risk assessment of populations residing in the Mekong River basin of Cambodia.

    PubMed

    Phan, Kongkea; Sthiannopkao, Suthipong; Heng, Savoeun; Phan, Samrach; Huoy, Laingshun; Wong, Ming Hung; Kim, Kyoung-Woong

    2013-11-15

    In the present study, we investigated the potential arsenic exposure of Cambodian residents from their daily food consumption. Environmental and ecological samples such as paddy soils, paddy rice (unhusked), staple rice (uncooked and cooked), fish and vegetables were collected from Kandal, Kratie and Kampong Cham provinces in the Mekong River basin of Cambodia. After acid-digestion, digestates were chemically analyzed by inductively coupled plasma mass spectrometry. Results revealed that the means of total arsenic concentration ([As]tot) in paddy soils and paddy rice from Kandal were significantly higher than those from Kampong Cham province (t-test, p<0.05). Moreover, a significant positive correlation between the [As]tot in paddy soils and paddy rice was found (r(14) = 0.826, p<0.01). Calculations of arsenic intake from food consumption indicated that the upper end of the range of the daily dose of inorganic arsenic for Kandal residents (0.089-8.386 μg d(-1) kg(-1) body wt.) was greater than the lower limits on the benchmark dose for a 0.5% increased incidence of lung cancer (BMDL0.5 is equal to 3.0 μg d(-1) kg(-1) body wt.). The present study suggests that the residents in Kandal are at risk of arsenic intake from their daily food consumption. However, the residents in Kratie and Kampong Cham provinces are less likely to be exposed to arsenic through their daily dietary intake. To the best of our knowledge, this is the first report estimating the daily intake and daily dose of inorganic arsenic from food consumption in the Mekong River basin of Cambodia. PMID:22818591

  7. Seasonal variability in the sources of particulate organic matter of the Mekong River as discerned by elemental and lignin analyses

    NASA Astrophysics Data System (ADS)

    Ellis, Erin E.; Keil, Richard G.; Ingalls, Anitra E.; Richey, Jeffrey E.; Alin, Simone R.

    2012-03-01

    The Mekong River ranks within the top ten rivers of the world in terms of water discharge and sediment load to the ocean, yet its organic matter (OM) composition remains unstudied. This river is experiencing anthropogenically forced changes due to land use and impoundment, and these changes are expected to intensify in the future. Accordingly, we monitored the composition (including vascular-plant signatures) of Mekong River fine particulate organic matter (FPOM) over a one-year period. Autochthonous production comprises a greater proportion of FPOM during the dry season than in the rainy season, as demonstrated by higher percent organic carbon values (7.9 ± 2.4 versus 2.2 ± 0.4%), lower yields of lignin normalized to carbon (0.40 ± 0.05 versus 1.1 ± 0.3 mg (100 mg OC)-1), and an increase in N:C ratios toward phytoplankton values during the dry season (from 0.06 to 0.12). Changes in the lignin-phenol composition of FPOM suggest that gymnosperms contribute more toward FPOM composition during the dry season, with angiosperms dominating in the wet season. This is supported by calculations of the lignin phenol vegetation index of riverine FPOM, which increases between the dry to wet seasons (dry: 29.4 ± 15.0 versus wet: 74.6 ± 17.3). These changes likely reflect seasonal differences in the proportion of flow that is coming from the Upper and Lower Basin, corresponding to compositional differences between the vegetation of these regions. Therefore, this work provides a baseline understanding of FPOM variability that can be used to assess how future change will affect this river.

  8. Taxonomy and conservation of Vietnam's primates: a review.

    PubMed

    Blair, Mary E; Sterling, Eleanor J; Hurley, Martha M

    2011-11-01

    Vietnam has the highest number of primate taxa overall (24-27) and the highest number of globally threatened primate taxa (minimum 20) in Mainland Southeast Asia. Conservation management of these species depends in part on resolving taxonomic uncertainties, which remain numerous among the Asian primates. Recent research on genetic, morphological, and acoustic diversity in Vietnam's primates has clarified some of these uncertainties, although a number of significant classification issues still remain. Herein, we summarize and compare the major current taxonomic classifications of Vietnam's primates, discuss recent advances in the context of these taxonomies, and suggest key areas for additional research to best inform conservation efforts in a region crucial to global primate diversity. Among the most important next steps for the conservation of Vietnam's primates is a new consensus list of Asian primates that resolves current differences between major taxonomies, incorporates recent research advances, and recognizes units of diversity at scales below the species-level, whether termed populations, morphs, or subspecies. Priority should be placed on recognizing distinct populations, regardless of the species concept in use, in order to foster the evolutionary processes necessary for primate populations to cope with inevitable environmental changes. The long-term conservation of Vietnam's primates depends not only on an accepted and accurate taxonomy but also on funding for on-the-ground conservation activities, including training, and the continued dedication and leadership of Vietnamese researchers and managers. PMID:21948330

  9. 31 CFR 500.577 - Authorization of bank transactions with respect to Vietnam by certain international organizations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... with respect to Vietnam by certain international organizations. 500.577 Section 500.577 Money and... Licensing Policy § 500.577 Authorization of bank transactions with respect to Vietnam by certain... reference to Vietnam are authorized. Example: A transfer to Vietnam or a Vietnamese national of funds...

  10. The Vietnam Drug User Returns. Final Report. Special Action Office Monograph, Series A, Number 2, May 1974.

    ERIC Educational Resources Information Center

    Robins, Lee N.

    This report, based upon case records and follow-up interviews with 965 U.S. Servicemen returning from Vietnam investigates: (1) the availability and utilization of narcotics, marihuana and alcohol in Vietnam; (2) the psychosocial and demographic predictors of pre- and post-Vietnam narcotic use; and (3) the post-Vietnam adjustment difficulties of…

  11. 31 CFR 500.560 - Bank accounts of official representatives of foreign governments in North Korea, North Viet-Nam...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... representatives of foreign governments in North Korea, North Viet-Nam, Cambodia, or South Viet-Nam. 500.560... governments in North Korea, North Viet-Nam, Cambodia, or South Viet-Nam. Specific licenses are issued authorizing payments from accounts of official representatives of foreign governments in North Korea,...

  12. The DELTA Synchrotron Light Interferometer

    SciTech Connect

    Berges, U.

    2004-05-12

    Synchrotron radiation sources like DELTA, the Dortmund Electron Accelerator, a third generation synchrotron light source, need an optical monitoring system to measure the beam size at different points of the ring with high resolution and accuracy. These measurements also allow an investigation of the emittance of the storage ring, an important working parameter for the efficiency of working beamlines with experiments using the synchrotron radiation. The resolution limits of the different types of optical synchrotron light monitors at DELTA are investigated. The minimum measurable beamsize with the normal synchrotron light monitor using visible light at DELTA is about 80 {mu}m. Due to this a synchrotron light interferometer was built up and tested at DELTA. The interferometer uses the same beamline in the visible range. The minimum measurable beamsize is with about 8 {mu}m one order of magnitude smaller. This resolution is sufficient for the expected small vertical beamsizes at DELTA. The electron beamsize and emittance were measured with both systems at different electron beam energies of the storage ring. The theoretical values of the present optics are smaller than the measured emittance. So possible reasons for beam movements are investigated.

  13. Teaching Pediatric Hand Surgery in Vietnam

    PubMed Central

    Kotsis, Sandra V.

    2007-01-01

    Background International volunteering missions are becoming an important focus of plastic surgeons in the United States. The purpose of this paper is to describe the teaching of pediatric hand surgery in Vietnam to share the lessons learned from this project. Methods Two medical education trips were conducted to the no. 1 Children’s Hospital in Ho Chi Minh city (Saigon) to teach pediatric hand and burn reconstructive surgery to the surgeons and therapists. This is the main referral children’s hospital for the country, and pediatric hand surgery expertise is not available. Results Structured education programs were conducted over two trips to introduce congenital hand surgery and burn reconstructive procedures using flap techniques. The education programs included lectures and surgical demonstrations of selected procedures. Their proficiency was verified by supervised conduct of these operations. Conclusions A well-conceived medical education program can introduce complex surgical discipline to a country. Through two trips, the surgeons at this referral center will have the capability to take care of many children requiring reconstructive hand surgery. PMID:18780043

  14. Adverse health consequences of the Vietnam War.

    PubMed

    Levy, Barry S; Sidel, Victor W

    2015-01-01

    The 40th anniversary of the end of the Vietnam War is a useful time to review the adverse health consequences of that war and to identify and address serious problems related to armed conflict, such as the protection of noncombatant civilians. More than 58,000 U.S. servicemembers died during the war and more than 150,000 were wounded. Many suffered from posttraumatic stress disorders and other mental disorders and from the long-term consequences of physical injuries. However, morbidity and mortality, although difficult to determine precisely, was substantially higher among the Vietnamese people, with at least two million of them dying during the course of the war. In addition, more than one million Vietnamese were forced to migrate during the war and its aftermath, including many "boat people" who died at sea during attempts to flee. Wars continue to kill and injure large numbers of noncombatant civilians and continue to damage the health-supporting infrastructure of society, expose civilians to toxic chemicals, forcibly displace many people, and divert resources away from services to benefit noncombatant civilians. Health professionals can play important roles in promoting the protection of noncombatant civilians during war and helping to prevent war and create a culture of peace. PMID:26754766

  15. Husbands' involvement in abortion in Vietnam.

    PubMed

    Johansson, A; Nga, N T; Huy, T Q; Dat, D D; Holmgren, K

    1998-12-01

    This study analyzes the involvement of men in abortion in Vietnam, where induced abortion is legal and abortion rates are among the highest in the world. Twenty men were interviewed in 1996 about the role they played in their wives' abortions and about their feelings and ethical views concerning the procedure. The results showed that both husbands and wives considered the husband to be the main decisionmaker regarding family size, which included the decision to have an abortion, but that, in fact, some women had undergone an abortion without consulting their husbands in advance. Parents and in-laws were usually not consulted; the couples thought they might object to the decision on moral grounds. Respondents' ethical perspectives on abortion are discussed. When faced with an unwanted pregnancy, the husbands adopted an ethics of care and responsibility toward family and children, although some felt that abortion was immoral. The study highlights the importance of understanding husbands' perspectives on their responsibilities and rights in reproductive decisionmaking and their ethical and other concerns related to abortion. PMID:9919633

  16. Advancing Development and Greenhouse Gas Reductions in Vietnam's Wind Sector

    SciTech Connect

    Bilello, D.; Katz, J.; Esterly, S.; Ogonowski, M.

    2014-09-01

    Clean energy development is a key component of Vietnam's Green Growth Strategy, which establishes a target to reduce greenhouse gas (GHG) emissions from domestic energy activities by 20-30 percent by 2030 relative to a business-as-usual scenario. Vietnam has significant wind energy resources, which, if developed, could help the country reach this target while providing ancillary economic, social, and environmental benefits. Given Vietnam's ambitious clean energy goals and the relatively nascent state of wind energy development in the country, this paper seeks to fulfill two primary objectives: to distill timely and useful information to provincial-level planners, analysts, and project developers as they evaluate opportunities to develop local wind resources; and, to provide insights to policymakers on how coordinated efforts may help advance large-scale wind development, deliver near-term GHG emission reductions, and promote national objectives in the context of a low emission development framework.

  17. Operation homecoming: psychological observations of repatriated Vietnam prisoners of war.

    PubMed

    Andersen, R S

    1975-02-01

    While in military service as a psychiatrist stationed at Scott Air Force Base, I had the opportunity to do the psychiatric evaluations on a number of the prisoners of war returning from North Vietnam. Scott Air Force Base is an area medical center (North Central United States), and was responsible for administering the medical and psychiatric examinations on all the men whose homes were in this area. Our hospital processed 29 returning POWS, of whom I saw 14. This group of POWS was probably unique in military history in that it was comprised almost entirely of officers. Their period of confinement was considerably longer than that of the prisoners of World War II and the Korean War, with the typical Vietnam POW being in captivity about six or seven years. This paper is an attempt to share my observations and thoughts on the experience of being a Vietnam Prisoner of War. PMID:1114192

  18. Hepatitis B infection in Vietnam: current issues and future challenges.

    PubMed

    Nguyen, Van T T

    2012-03-01

    Hepatitis B virus (HBV) infection remains a major public health problem in Vietnam. Recent studies have found that prevalence of current HBV infection (HBsAg+) ranges from 10% to 20% in the general population and 20% to 40% among injecting drug users and HIV+ patients. However, HBV prevention and control in Vietnam relies heavily on universal infant vaccination program and HBsAg screening for blood donors. Currently, HBV prevention and control is underfunded by the government and receives little support from international agencies. HBV-related liver disease will continue to create a heavy burden for public health in Vietnam in the next several decades unless appropriate interventions are undertaken urgently. Establishment of a national strategy for HBV prevention and control is crucial to develop and implement effective interventions. PMID:21159700

  19. Mapping wetlands in the Lower Mekong Basin for wetland resource and conservation management using Landsat ETM images and field survey data.

    PubMed

    MacAlister, Charlotte; Mahaxay, Manithaphone

    2009-05-01

    The Mekong River Basin is considered to be the second most species rich river basin in the world. The 795,000 km(2) catchment encompasses several ecoregions, incorporating biodiverse and productive wetland systems. Eighty percent of the rapidly expanding population of the Lower Mekong Basin (LMB), made up in part by Lao PDR, Thailand, Cambodia and Viet Nam, live in rural areas and are heavily reliant on wetland resources. As the populations of Cambodia and Lao PDR will double in the next 20 years, pressure on natural resources and particularly wetlands can only increase. For development planning, resource and conservation management to incorporate wetland issues, information on the distribution and character of Mekong wetlands is essential. The existing but outdated wetland maps were compiled from secondary landuse-landcover data, have limited coverage, poor thematic accuracy and no meta-data. Therefore the Mekong River Commission (MRC) undertook to produce new wetland coverage for the LMB. As resources, funding and regional capacity are limited, it was determined that the method applied should use existing facilities, be easily adaptable, and replicable locally. For the product to be useful it must be accepted by local governments and decision makers. The results must be of acceptable accuracy (>75%) and the methodology should be relatively understandable to non-experts. In the first stage of this exercise, field survey was conducted at five pilot sites covering a range of typical wetland habitats (MRC wetland classification) to supply data for a supervised classification of Landsat ETM images from the existing MRC archive. Images were analysed using ERDAS IMAGINE and applying Maximum Likelihood Classification. Field data were reserved to apply formal accuracy assessment to the final wetland habitat maps, with resulting accuracy ranging from 77 to 94%. The maps produced are now in use at a Provincial and National level in three countries for resource and

  20. Potential Effects of Hydroelectric Dam Development in the Mekong River Basin on the Migration of Siamese Mud Carp (Henicorhynchus siamensis and H. lobatus) Elucidated by Otolith Microchemistry

    PubMed Central

    Fukushima, Michio; Jutagate, Tuantong; Grudpan, Chaiwut; Phomikong, Pisit; Nohara, Seiichi

    2014-01-01

    The migration of Siamese mud carp (Henicorhynchus siamensis and H. lobatus), two of the most economically important fish species in the Mekong River, was studied using an otolith microchemistry technique. Fish and river water samples were collected in seven regions throughout the whole basin in Thailand, Laos and Cambodia over a 4 year study period. There was coherence between the elements in the ambient water and on the surface of the otoliths, with strontium (Sr) and barium (Ba) showing the strongest correlation. The partition coefficients were 0.409–0.496 for Sr and 0.055 for Ba. Otolith Sr-Ba profiles indicated extensive synchronized migrations with similar natal origins among individuals within the same region. H. siamensis movement has been severely suppressed in a tributary system where a series of irrigation dams has blocked their migration. H. lobatus collected both below and above the Khone Falls in the mainstream Mekong exhibited statistically different otolith surface elemental signatures but similar core elemental signatures. This result suggests a population originating from a single natal origin but bypassing the waterfalls through a passable side channel where a major hydroelectric dam is planned. The potential effects of damming in the Mekong River are discussed. PMID:25099147

  1. Potential effects of hydroelectric dam development in the Mekong River basin on the migration of Siamese mud carp (Henicorhynchus siamensis and H. lobatus) elucidated by otolith microchemistry.

    PubMed

    Fukushima, Michio; Jutagate, Tuantong; Grudpan, Chaiwut; Phomikong, Pisit; Nohara, Seiichi

    2014-01-01

    The migration of Siamese mud carp (Henicorhynchus siamensis and H. lobatus), two of the most economically important fish species in the Mekong River, was studied using an otolith microchemistry technique. Fish and river water samples were collected in seven regions throughout the whole basin in Thailand, Laos and Cambodia over a 4 year study period. There was coherence between the elements in the ambient water and on the surface of the otoliths, with strontium (Sr) and barium (Ba) showing the strongest correlation. The partition coefficients were 0.409-0.496 for Sr and 0.055 for Ba. Otolith Sr-Ba profiles indicated extensive synchronized migrations with similar natal origins among individuals within the same region. H. siamensis movement has been severely suppressed in a tributary system where a series of irrigation dams has blocked their migration. H. lobatus collected both below and above the Khone Falls in the mainstream Mekong exhibited statistically different otolith surface elemental signatures but similar core elemental signatures. This result suggests a population originating from a single natal origin but bypassing the waterfalls through a passable side channel where a major hydroelectric dam is planned. The potential effects of damming in the Mekong River are discussed. PMID:25099147

  2. Alcoholism in Black Vietnam Veterans: Symptoms of Posttraumatic Stress Disorder

    PubMed Central

    Carter, James H.

    1982-01-01

    A definitive diagnosis of a posttraumatic stress disorder in black Vietnam veterans can be made when recognition is given, not only to the stressors of war but to racism. An aftermath of the war for black veterans has been an alarming increase in alcoholism, believed to be an attempt to reduce feeling of inadequacy, pessimism, and uncontrollable rage. Two cases are described that are illustrative of the posttraumatic stress disorder and alcoholism in black Vietnam veterans. A brief discussion of salient issues that are crucial to diagnosis and treatment is presented. PMID:7120496

  3. US firms in middle of Vietnam, China oil battle

    SciTech Connect

    Kaplan, D.

    1994-04-21

    U.S. oil companies Crestone Energy and Mobil are developing oil fields in the South China Sea and are in the middle of a dispute between China and Vietnam over ownership of two large fields. The two fields together contain an estimated 1.1 billion barrels of petroleum. Vietnam maintains they own both fields since they are located on the Vietnamese continental shelf, while China says they own them historically. Companies from Australia, Japan, and Indonesia are also involved in developing the two fields.

  4. Coastal Monitoring Using L-band Synthetic Aperture Radar (SAR) Image Data - Some Case Studies in Asian Delta Areas

    NASA Astrophysics Data System (ADS)

    Tanaka, A.

    2014-12-01

    Coastal geomorphology is highly variable as it is affected by sea-level changes and other naturally- and human-induced fluctuations. To effectively assess and monitor geomorphological changes in various time scales is thus critical for coastal management. Asian mega deltas are vulnerable to a sea-level rise due to its low-lying delta plain, and are dynamic region given a large amount of sediment supply. However, limited data availability and accessibility in the deltas have prevented establishment of systematic coastal monitoring. A variety of remote sensing systems can be used to monitor geomorphological changes in coastal areas as it has wide spatial coverage and high temporal repeatability. Especially, analysis using SAR (Synthetic Aperture Radar) data not affected by the cloud conditions offer potential for monitoring in the monsoon Asia region. We will present some case studies of Asian coastal regions using L-band SAR data, ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band SAR) and JERS-1 (Japanese Earth Resource Satellite-1) SAR data. One example is that time-series of radar amplitude images can be used to delineate changes quantitatively of the areal extent of river-mouth bars in distributaries of the Mekong River delta. It shows that the estimated areas of river mouthbars gradually increase on an annual time scale, and seasonal variations of areas were also recognized. Another example is that differential SAR interferometry is applied to the coast of the Yellow River delta in China. It shows very high subsidence rates, likely due to groundwater pumping. A further example is that we apply a SAR interferometry time series analysis to monitor ground deformations in the lower Chao Phraya delta plain, Thailand. A single reference time series interferogram from the stacking of unwrapped phases were applied. The subsidence and uplift pattern observed using the SAR interferometry time series analysis highlights the spatial complexity

  5. SEX RATIO AT BIRTH AND THE IDEAL FAMILY IN CHI LINH DISTRICT, VIETNAM

    PubMed Central

    Thuy Duong, Doan Thi

    2016-01-01

    Chi Linh district, which locates in the Red Delta River region, has been recognized as the “hot pot” of high sex ratio at birth in Vietnam. This paper used community-based periodic Demographic-Epidemiologic Surveillance System (CHILILAB) to describe sex ratio at birth (SRB) and identify social - economic factors that related to the SRB. A total 5,940 births born from August 1, 2004 to August 31, 2011 was included in analysis. The SRB of 116.6 boys/100 girls (CI: 110.7 – 122.5) was significantly higher than normal. SRB were found high among second child having only older sister(s), among third child and higher birth order, among mothers who were 35 years and older, running small business or homemakers. Interestingly, a SRB of 91.4 boys/100 girls (CI: 81.8 – 102) was found among second children having an older brother, this is significantly lower than the normal level. Further research should be done to assert if abortion is practiced both to have a son and to have a daughter. PMID:27499813

  6. Delta launch vehicle inertial guidance system (DIGS)

    NASA Technical Reports Server (NTRS)

    Duck, K. I.

    1973-01-01

    The Delta inertial guidance system, part of the Delta launch vehicle improvement effort, has been flown on three launches and was found to perform as expected for a variety of mission profiles and vehicle configurations.

  7. Delta Revival: Restoring a California Ecosystem

    USGS Publications Warehouse

    U.S. Geological Survey; California Bay Delta Authority

    2003-01-01

    'Delta Revival: Restoring a California Ecosystem' shows scientists from many disciplines working together to guide the unprecendented restoration of the Sacramento- San Joaquin Delta east of San Francisco Bay.

  8. Spongeplant Spreading in the Delta

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Invasive, exotic aquatic plants impact a range of important economic and ecological functions in the Sacramento-San Joaquin Delta of California, and the state now spends over $5 million to control water hyacinth and Brazilian waterweed. In 2007, a new exotic floating plant South American Spongeplan...

  9. Delta-ALA urine test

    MedlinePlus

    ... increased level of urinary delta-ALA may indicate: Lead poisoning Porphyria (several types) A decreased level may occur ... A.M. Editorial team. Related MedlinePlus Health Topics Lead Poisoning Porphyria Browse the Encyclopedia A.D.A.M., ...

  10. Delta launch vehicle accident investigation

    NASA Astrophysics Data System (ADS)

    1986-03-01

    The text of the testimony given by several witnesses during the House hearings on the Delta launch vehicle accident of May 3, 1986 is given. Pre-launch procedures, failure analysis, the possibility of sabotage, and design and testing are among the topics discussed.

  11. N-{Delta} weak transition

    SciTech Connect

    Graczyk, Krzysztof M.

    2011-11-23

    A short review of the Rein-Sehgal and isobar models is presented. The attention is focused on the nucleon-{Delta}(1232) weak transition form-factors. The results of the recent re-analyses of the ANL and BNL bubble chamber neutrino-deuteron scattering data are discussed.

  12. Phytoplankton fuels Delta food web

    USGS Publications Warehouse

    Jassby, Alan D.; Cloern, James E.; Muller-Solger, A. B.

    2003-01-01

    Populations of certain fishes and invertebrates in the Sacramento-San Joaquin Delta have declined in abundance in recent decades and there is evidence that food supply is partly responsible. While many sources of organic matter in the Delta could be supporting fish populations indirectly through the food web (including aquatic vegetation and decaying organic matter from agricultural drainage), a careful accounting shows that phytoplankton is the dominant food source. Phytoplankton, communities of microscopic free-floating algae, are the most important food source on a Delta-wide scale when both food quantity and quality are taken into account. These microscopic algae have declined since the late 1960s. Fertilizer and pesticide runoff do not appear to be playing a direct role in long-term phytoplankton changes; rather, species invasions, increasing water transparency and fluctuations in water transport are responsible. Although the potential toxicity of herbicides and pesticides to plank- ton in the Delta is well documented, the ecological significance remains speculative. Nutrient inputs from agricultural runoff at current levels, in combination with increasing transparency, could result in harmful al- gal blooms. 

  13. Revisiting double Dirac delta potential

    NASA Astrophysics Data System (ADS)

    Ahmed, Zafar; Kumar, Sachin; Sharma, Mayank; Sharma, Vibhu

    2016-07-01

    We study a general double Dirac delta potential to show that this is the simplest yet still versatile solvable potential to introduce double wells, avoided crossings, resonances and perfect transmission (T = 1). Perfect transmission energies turn out to be the critical property of symmetric and anti-symmetric cases wherein these discrete energies are found to correspond to the eigenvalues of a Dirac delta potential placed symmetrically between two rigid walls. For well(s) or barrier(s), perfect transmission (or zero reflectivity, R(E)) at energy E=0 is non-intuitive. However, this has been found earlier and called the ‘threshold anomaly’. Here we show that it is a critical phenomenon and we can have 0≤slant R(0)\\lt 1 when the parameters of the double delta potential satisfy an interesting condition. We also invoke a zero-energy and zero curvature eigenstate (\\psi (x)={Ax}+B) of the delta well between two symmetric rigid walls for R(0)=0. We resolve that the resonant energies and the perfect transmission energies are different and they arise differently.

  14. Maintenance of large deltas through channelization

    NASA Astrophysics Data System (ADS)

    Giosan, L.; Constatinescu, S.; Filip, F.

    2013-12-01

    A new paradigm for delta restoration is currently taking shape using primarily Mississippi delta examples. Here we propose an alternative for delta maintenance primarily envisioned for wave-influenced deltas based on Danube delta experiences. Over the last half century, while the total sediment load of the Danube dramatically decreased due to dam construction on tributaries and its mainstem, a grand experiment was inadvertently run in the Danube delta: the construction of a dense network of canals, which almost tripled the water discharge toward the interior of the delta plain. We use core-based and chart-based sedimentation rates and patterns to explore the delta transition from the natural to an anthropogenic regime, to understand the effects of far-field damming and near-field channelization, and to construct a conceptual model for delta development as a function sediment partition between the delta plain and the delta coastal fringe. We show that sediment fluxes increased to the delta plain due to channelization, counteracting sea level rise. In turn, the delta coastal fringe was most impacted by the Danube's sediment load collapse. Furthermore, we show that morphodynamic feedbacks at the river mouth are crucial in trapping sediment near the coast and constructing wave-dominated deltas or lobes or delaying their destruction. As a general conclusion, we suggest that increased channelization that mimics and enhances natural processes may provide a simple solution for keeping delta plains above sea level and that abandonment of wave-dominated lobes may be the most long term efficient solution for protecting the internal fluvial regions of deltas and provide new coastal growth downcoast.

  15. Assessment of Delta Nitrogen Losses (Delta NL) at the Field Level

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We defined a new concept of field-level delta nitrogen (N) losses (Delta NL) as a comparison between management scenarios. We defined delta nitrogen losses (Delta NL) as a function of improved N use efficiencies of field management scenarios that reduce the average N inputs and/or modify other manag...

  16. After Access: Divergent Learning Profiles in Vietnam and India

    ERIC Educational Resources Information Center

    Rolleston, Caine; James, Zoe

    2015-01-01

    In recent decades, both India and Vietnam have successfully expanded access to schooling to near-universal levels and have shifted their focus to quality-oriented policy reform. Yet, international and national evidence shows strongly contrasting learning profiles for children within the two systems. Simple indicators of numeracy suggest similar…

  17. Employment Problems of the Vietnam Veteran. Special Report.

    ERIC Educational Resources Information Center

    National Advisory Council on Vocational Education, Washington, DC.

    Vietnam veterans are finding it extremely difficult of find jobs upon their return home. Altogether there are approximately 320,000 known unemployed veterans. Statistics show that they have a higher unemployment rate than nonveterans, and that the unemployment persists longer. Factors contributing to this condition are the economic slump, a…

  18. Special Report [on the] Employment Problems of the Vietnam Veteran.

    ERIC Educational Resources Information Center

    National Advisory Council on Vocational Education, Washington, DC.

    A report analyzing the special problems and needs of the Vietnam-era veterans and offering some recommendations in regard to training and employment is presented. This report is based on available statistical data along with results of small group interviews with returning veterans and meetings with officials responsible for programs affecting…

  19. Current status of fasciolosis in Vietnam: an update and perspectives.

    PubMed

    Bui, T D; Doanh, P N; Saegerman, C; Losson, B

    2016-09-01

    Vietnam is recognized to be endemic for fasciolosis. However, most of the available publications have not been published in international journals. This review is based on national and international Vietnamese publications and highlights the current status of fasciolosis in Vietnam. It also provides some information available for neighbouring countries. Updated data on responsible species, distribution, transmission and control aspects are summarized. The central region of Vietnam is reported as being highly endemic for fasciolosis, with a high number of human patients (more than 20,000 in 2011). Fasciola gigantica is reported to be the main species in Vietnam. However, hybrids between F. gigantica and F. hepatica were identified. Both humans and animals are infected by the ingestion of raw vegetables and possibly contaminated drinking water. Three lymnaeid snail species (Austropeplea viridis, Radix auricularia and Radix rubiginosa) may act as intermediate hosts of Fasciola spp. However, due to the likely misidentification of snail species and cercariae during the past decade the critical analysis of published data is difficult. A better understanding of transmission aspects of fasciolosis would allow the implementation of preventive measures of this important neglected zoonotic disease. PMID:26564097

  20. Modeling the impact of rubella vaccination in Vietnam.

    PubMed

    Vynnycky, Emilia; Yoshida, Lay Myint; Huyen, Dang Thi Thanh; Trung, Nguyen Dac; Toda, Kohei; Cuong, Nguyen Van; Thi Hong, Duong; Ariyoshi, Koya; Miyakawa, Masami; Moriuchi, Hiroyuki; Tho, Le Huu; Nguyen, Hien Anh; Duc Anh, Dang; Jit, Mark; Hien, Nguyen Tran

    2016-01-01

    Supported by GAVI Alliance, measles-rubella vaccination was introduced in Vietnam in 2014, involving a mass campaign among 1-14 year olds and routine immunization of children aged 9 months. We explore the impact on the incidence of Congenital Rubella Syndrome (CRS) during 2013-2050 of this strategy and variants involving women aged 15-35 years. We use an age and sex-structured dynamic transmission model, set up using recently-collected seroprevalence data from Central Vietnam, and also consider different levels of transmission and contact patterns. If the serological profile resembles that in Central Vietnam, the planned vaccination strategy could potentially prevent 125,000 CRS cases by 2050 in Vietnam, despite outbreaks predicted in the meantime. Targeting the initial campaign at 15-35 year old women with or without children aged 9 months-14 years led to sustained reductions in incidence, unless levels of ongoing transmission were medium-high before vaccination started. Assumptions about contact greatly influenced predictions if the initial campaign just targeted 15-35 year old women and/or levels of ongoing transmission were medium-high. Given increased interest in rubella vaccination, resulting from GAVI Alliance funding, the findings are relevant for many countries. PMID:26260857