Sai Gon-Dong Nai Research Articles

Response of streamflow and sediment variability to cascade dam development and climate change in the Sai Gon Dong Nai River basin

Response of streamflow and sediment variability to cascade dam development and climate change in the Sai Gon Dong Nai River basin

Acute Toxicity of DDT on Embryo and Larval Growth of the Pacific Oyster, Crassostrea gigas (Thunberg, 1793): A Case Study in the Saigon–Dongnai River, Vietnam

Acute Toxicity of DDT on Embryo and Larval Growth of the Pacific Oyster, Crassostrea gigas (Thunberg, 1793): A Case Study in the Saigon–Dongnai River, Vietnam

Geological-geotechnical correlation of a deltaic subsoil profile and characterization of its uppermost soft marine clay deposit with reference to infrastructure development in the Saigon-Dong Nai delta, Vietnam

Geological-geotechnical correlation of a deltaic subsoil profile and characterization of its uppermost soft marine clay deposit with reference to infrastructure development in the Saigon-Dong Nai delta, Vietnam

Sources of microplastic pollution in the Saigon-Dong Nai rivers, potential risks affecting human health and recommendations for mitigation solutions

The purpose of the study was to investigate the existence of tiny plastic particles present in the aquatic environment of the Saigon-Dong Nai rivers. Additionally, the study provided an overview of the origins and risks of microplastics for human health. A sampling method was built based on the ocean microplastic analysis method of National Oceanic and Atmospheric Administration to match actual conditions. Water samples were extracted to remove organic matter, minerals, and metals before analyzing them using stereomicroscopy and Fourier-Transform Infrared spectroscopy. Research results have shown the existence of microplastics with sizes from 0.1-5 millimeters in the Saigon-Dong Nai rivers. Microplastics in the form of fragments, films, and fibers account for 228,120-715,124 items.m−3 of water and pelleted microplastics account for 23-300 items.m−3 of water. The results about microplastics in the samples showed that Polyethylene, Polypropylene, and Polyvinylchloride accounted for 51.2%, 27.1%, and 13.4%, respectively; and the rest are other plastics (8.3%). The average length and radius of filamentous microplastics are 524.68 micrometers and 100.4 micrometers, respectively. The average length of microplastics in the form of fragments and films is 229.49 micrometers with an average width of 101.3-120.6 micrometers. The average radius of microplastics in the form of pellets is 113.81 micrometers. They have many different colors and shapes and appear in many places where garbage accumulates when the tide recedes, especially in densely populated areas such as Thu Dau Mot and Ho Chi Minh City.

Water-level changes and subsidence rates along the Saigon-Dong Nai River Estuary and the East Sea coastline of the Mekong Delta

Southeast Asian deltas are highly threatened areas for flooding as a response to the combined effects of natural compaction and subsidence exacerbated by human impacts, e.g. oil, gas and water extraction, retention of sediment discharge due to river damming and sand mining, land use changes, sea-level rise and storm-induced water-level setup. Tide-induced water-level fluctuations on different time- and spatial scales, seasonal variations of freshwater runoff and sea-level setup can amplify the impact of sea-level rise and of storm surges on the coastal environment and its inhabitants. Moreover, increasing populations accompanied by growing societal demands can lead to further pressure on delta areas. For the Vietnamese Mekong Delta (VMD) and the Saigon-Dong Nai River (SGDNR), rates of subsidence of several cm/yr have already been determined, but for the coastal area, which is most vulnerable to sea-level rise and storm surges, a lack of detailed spatial and temporal information of this parameter exists. To assess the influence of tide- and water-level fluctuations, records from 11 stations, from the tectonically stable position Vung Tau north of the SGDNR entry to Ganh Hao in the southern VMD, were analyzed. The results reveal a relative sea-level rise at Vung Tau reaching 2.2 ± 0.3 mm/yr for the period from 1987-2015, while along the VMD those rates show a spatially variation from 5.6 ± 0.3 mm/yr at Ben Trai to 13.5 ± 0.7 mm/yr at My Thanh. Considering Vung Tau as tectonically stable, these numbers indicate subsidence rates of the coastal sections along the VMD ranging from 3.4 ± 0.3 mm/yr to 11.3 ± 0.7 mm/yr. It is likely that the rates of subsidence along the coast of VMD have accelerated since 2005. They are not only up to 4 times higher than the mean sea-level rise but are variable along the whole SGDNR estuary and the VMD East Sea coastline. Additionally, the importance of daily, fortnightly and seasonal water level fluctuations due to tides and atmospheric influence, which are acting on top of the long-term relative sea-level rise, is shown. Especially the identified regional variations make these data valuable for setting regional priorities for protection strategies to mitigate riverine and marine flooding, especially when both coincide.

Influence of flood control facilities on water level in downstream of river system Sai Gon -Dong Nai

Ho Chi Minh City, Vietnam's largest city, located on the lower reaches of the Sai Gon-Dong Nai (SG-DN) river system, is facing increasingly severe flooding due to changes in river flow and water levels. This article presents the results of a study to assess the impact of hydraulic structures located in the upper reaches on the water level in the lower reaches of the SG-DN River. As part of a study to assess the impact of upstream reservoirs and flood control structures on the water level in the lower reaches of the SG-DN River, hydrological data of the river network were collected. A hydraulic model was developed based on a digital elevation model (DEM) using the software package Mike 11, Mike 21 and Mike Flood. The water level of the Sai Gon River from the upper reaches to the Thu Dau Mot measuring station depends on the Dau Tieng reservoir, and the Tri An reservoir directly affects the water level in the river section from behind the Tri An dam to the Dong Nai section in the Tam An - Long Phuoc area. In the sections of the Sai Gon and Dong Nai rivers, which are less affected by the two overlying reservoirs, it is necessary to develop preventive measures to supply sufficient fresh water to meet the population's and industries' needs. In areas prone to flooding and underflooding due to the operation of anti-flood locks, it is also necessary to reconstruct hydraulic structures (raise the elevations of foundations, expand drainage systems, build reservoirs for collecting flood water, etc.)

Influence Of Flood Control Facilities On The Water Level In The Downstream Of The River System Sai Gon - Dong Nai

Ho Chi Minh City, Vietnam’s largest city, located on the lower reaches of the Sai Gon-Dong Nai (SG-DN) river system, is facing increasingly severe flooding due to changes in river flow and water levels. This article presents the results of a study to assess the impact of hydraulic structures located in the upper reaches on the water level in the lower reaches of the SG-DN River. As part of a study to assess the impact of upstream reservoirs and flood control structures on the water level in the lower reaches of the SG-DN River, hydrological data of the river network were collected and a hydraulic model was developed based on a digital elevation model (DEM) using the software package Mike 11, Mike 21 and Mike Flood. The water level of the Sai Gon River from the upper reaches to the Thu Dau Mot measuring station directly depends on the Dau Tieng reservoir, and the Tri An reservoir directly affects the water level in the river section from behind the Tri An dam to the Dong Nai section in the Tam An - Long Phuoc area. In the sections of the Sai Gon and Dong Nai rivers, which are less affected by the two overlying reservoirs, it is necessary to develop preventive measures to supply sufficient fresh water to meet the needs of the population and industries. In areas prone to flooding and underflooding as a result of the operation of anti-flood locks, it is also necessary to reconstruct hydraulic structures (raise the elevations of foundations, expand drainage systems, build reservoirs for collecting flood water etc.)

Microplastics and solutions to remove microplastics in wastewater from wastewater treatment plants in the Saigon–Dong Nai river basin, Vietnam

Microplastics and solutions to remove microplastics in wastewater from wastewater treatment plants in the Saigon–Dong Nai river basin, Vietnam

Assessing Microplastic Prevalence and Dispersion from Saigon Urban Canals via Can Gio Mangrove Reserve to East Sea by Raman Scattering Microscopy

Plastic pollution is one of the significant environmental concerns due to the threefold increase in global plastic waste. Marine microplastics, including petroleum-based plastic pieces and synthetic and artificial fibers smaller than 5 mm, are not only ubiquitous in natural water but also high in wastewater streams due to the direct discharge, transfer and breakdown of plastic items. This research aims to investigate the presence and dispersion of microplastics in the downtown area and coastal suburban area of Ho-Chi-Minh City by using Raman microscopy. As a result, the most common plastics (PE, PET, PA, PP, PVC, PS and PMMA) were detected, and most of them were fibrous shorter than 500 μm. The total microplastics decreased gradually from the urban waterborne (up to 220 MPs/L) via Can Gio UNESCO Mangrove Biosphere Reserve (10 MPs/L) and to the East Sea (3 MPs/L), which reveals the potential role of the mangrove in reducing marine contaminants including microplastics. This study provides important insights into microplastic pollution in the Western Pacific Region, especially the Saigon-Dong Nai river systems, supporting useful data for natural water resources management.

Late Holocene Morphodynamic Feedback in Can Gio Mangrove Tide-Dominated River Mouth Systems, Vietnam

Can Gio (CG), a mangrove forest with a dense network of tidal creeks, gradually grew and spread seaward on a coastal platform, which was built since about 8 ka before present (BP). Along with this development, a sand ridge began to form and moved back with the shoreline withdrawal landward in the Late Holocene. This mangrove environment is likely abandoned from the mainland but was, however, the place for settlement of ancient Vietnamese a few centuries BC. The CG mangrove forest was severely destroyed during the American War and was restored since 1980. However, the historical change of the landscape along the Saigon-Dong Nai River (SG-DNR) since the Late Holocene is not completely unraveled. By analyzing sediment cores with a multiproxy approach, we investigated the recent geological development with regard to the variation of the intensity of the East Asian palaeomonsoon and regarding the accommodation space, as both regulate the development of this coastal environment. A recently significant shift in the coastline, mainly due to a change of hydroclimatic factors, was observed. A continuous coastline retreat occurred over the last millennium, changing the depositional environment and reshaping the CG mangrove landscape. Along the present coast and tidal channels, partially strong erosion and bank failures occur, alternating with accretion at other coastal sections. This development tends to increase progressively.

Organochlorine Compounds in Commercial Bivalves from the Mekong and Saigon–Dong Nai River Deltas (South Vietnam)

Organochlorine Compounds in Commercial Bivalves from the Mekong and Saigon–Dong Nai River Deltas (South Vietnam)

Statistical and Hydrological Evaluations of Water Dynamics in the Lower Sai Gon-Dong Nai River, Vietnam

The water levels downstream of the Sai Gon and Dong Nai river in Southern Vietnam have been significantly changed over the last three decades, leading to severe impacts on urban flooding and salinity intrusion and threating the socio-economic development of the region and lives of many local people. In this study, the Mann-Kendall (MK) and trend-free prewhitening (TFPW) tests were applied to detect the water level trends and changepoints based on a water level time series at six gauging stations that were located along the main rivers to the sea over 1980–2019. The results indicated that the water level has rapidly increased by about 0.17 to 1.8 cm/year at most gauge stations surrounding Ho Chi Minh City, strongly relating to urbanization and the dike polder system’s impacts that eliminates the water storage space. In addition, the operation of upstream reservoirs has contributed to water level changes with significant consequences since the high-water level at Tri An station on the Dong Nai river occurs 1000–1500 times compared to 300–500 times before the operation. Although the effects of the flows from the sea are less than the two other factors, the local government should seriously consider water level changes, especially in the coastal regions. Our study contributes empirical evidence to evaluate the water level trends in the planning and development of infrastructure, which is necessary to adapt to future changes in Southern Vietnam’s hydrologic system.

Hydrologic modeling by means of a hybrid downscaling approach: an application to the Sai Gon–Dong Nai Rivers Basin

Abstract The spatial and temporal availability and reliability of hydrological data are substantial contributions to the accuracy of watershed modeling; unfortunately, such data requirements are challenging and perhaps impossible in many regions of the world. In this study, hydrological conditions are simulated using the hydrologic model-WEHY, whose data input are obtained from a hybrid downscaling technique to provide reliable and high temporal and spatial resolution hydrological data. The hybrid downscaling technique is coupled to a hydroclimate and machine learning models; wherein the global atmospheric reanalysis data, including ERA-Interim, ERA-20C, and CFSR are used for initial and boundary conditions of dynamical downscaling utilizing the Weather Research and Forecasting model (WRF). The machine learning model (ANN) then follows to further downscale the WRF outputs to a finer resolution over the studied watershed. An application of the combination of mentioned techniques is applied to the third-largest river basin in Vietnam, the Sai Gon–Dong Nai Rivers Basin. The validation of hybrid model is in the ‘satisfactory’ range. After the estimation of geomorphology and land cover within the watershed, WEHY's calibration and validation are performed based on observed rainfall data. The simulation results matched well with flow observation data with respect to magnitude for both the rising and recession time segments. In comparison, among the three selected reanalysis data sets, the best calibration and validation results were obtained from the CFSR data set. These results are closer to the observation data than those using only the dynamic downscaling technique in combination with the WEHY model.

Modeling high-resolution precipitation by coupling a regional climate model with a machine learning model: an application to Sai Gon–Dong Nai Rivers Basin in Vietnam

Modeling high-resolution precipitation by coupling a regional climate model with a machine learning model: an application to Sai Gon–Dong Nai Rivers Basin in Vietnam

Nutrient budgets in the Saigon–Dongnai River basin: Past to future inputs from the developing Ho Chi Minh megacity (Vietnam)

AbstractHo Chi Minh City (HCMC, Vietnam) is one of the fastest growing megacities in the world. In this paper, we attempt to analyse the dynamics of nutrients, suspended sediments, and water discharges in its aquatic systems today and in the future. The work is based on nine sampling sites along the Saigon River and one on the Dongnai River to identify the reference water status upstream from the urban area and the increase in fluxes that occur within the city and its surroundings. For the first time, the calculated fluxes allow drawing up sediment and nutrient budgets at the basin scale and the quantification of total nutrient loading to the estuarine and coastal zones (2012–2016 period). Based on both national Vietnamese and supplementary monitoring programs, we estimated the water, total suspended sediment, and nutrients (Total N, Total P, and dissolved silica: DSi) fluxes at 137 m3 year−1, 3,292 × 103 tonSS year−1, 5,323 tonN year−1, 450 tonP year−1, and 2,734 tonSi year−1 for the Saigon River and 1,693 m3 year−1, 1,175 × 103 tonSS year−1, 31,030 tonN year−1, 1,653 tonP year−1, and 31,138 tonSi year−1 for the Dongnai River, respectively. Nutrient fluxes provide an indicator of coastal eutrophication potential (indicator of coastal eutrophication potential), using nutrient stoichiometry ratios. Despite an excess of nitrogen and phosphorus over silica, estuarine waters downstream of the megacity are not heavily impacted by HCMC. Finally, we analysed scenarios of future trends (2025–2050) for the nutrient inputs on the basis of expected population growth in HCMC and improvement of wastewater treatment capacity. We observed that without the construction of a large number of additional wastewater treatment plants, the eutrophication problem is likely to worsen. The results are discussed in the context of the wastewater management policy.

Spatio-temporal pattern of water quality in the Saigon-Dong Nai river system due to waste water pollution sources

ABSTRACT This paper studies the current status of water quality, using both statistical and modelling approaches, in the waterways of the Saigon-Dong Nai river basin in relation to the nature of its environment and the effect of point and diffuse pollution sources. These sources are located mainly in the urban and industrial areas of Ho Chi Minh City (HCMC) and Dong Nai province. The statistical analysis of monitoring data allows us to determine the state of water quality while the modelling approach provides the means to manage the pollution sources. Both approaches are used in this work. Our statistical analysis of the water quality data collected at many stations from the upper reach of the Saigon and Dong Nai rivers to the urban waterways and the lower end of the rivers near the sea shows a contrast of water quality in different basin areas. These differences are consistent in both dry and rainy seasons and during the high tide and low tide. The results show that several hot spots of some water quality variables require management focus, such as organic waste water pollution at Binh Dien and Thay Cai in HCMC mainly due to local sources. Moderately and highly degraded water quality occurs at Binh Phuoc, Phu An and Cat Lai which are downstream from the industrial areas of Binh Duong (Binh Duong province) and Bien Hoa (Dong Nai province) before entering HCMC. Modelling of some important water quality variables also confirms the spatial extent of the areas where water quality is different as analysed from the statistical analysis of monitoring data. The MIKE-11 modelling system is shown to be a valuable tool for predicting the effect of different sources in HCMC metropolitan area on the waterway areas where water quality is important to protect the ecosystem and people health.

A possible solution for flood risk mitigation in Ho Chi Minh City and the lower Sai Gon-Dong Nai River Basin

The Sai Gon-Dong Nai Basin plays a very important role in the socio-economic development of Vietnam. The area of Ho Chi Minh (HCM) City is about 2095 km2, 60% of which lying under 2 m above MSL. Its population is about 8.136 million. Economic development has led to flood-related problems. The causes of floods are monsoon rainfalls, high tides, and outflows from the Dau Tieng Reservoir, upstream of HCM City. This paper proposed a plausible solution for flood mitigation in HCM City by uplifting the Dau Tieng dam crest. This solution can be recommended based on the results of an extensive simulation study which used: (i) a statistical downscaling procedure for evaluating the climate change (CC) impacts on precipitations; (ii) the MARINE model for simulating the rainfall-runoff process; (iii) the Telemac2D model for simulating the inundation; and (iv) the GIS tool for representing the inundated areas under different CC scenarios. It was found that under the A2 scenario an increase of rainfall by 2050s and added 40% of this rainfall (assuming due to tropical depression), the maximum regulated discharges released from the Dau Tieng dam could reach 1650, 500 and 300 m3s−1 without any enhancement then with the dam enhancement of 1.0 and 1.5 m, respectively. As comparing to event occurred on July 21, 2009 due to the combined effect of a heavy rainfall and a high tide condition, the inner city flooding area increases by 1.2, 1.3 and 8.2% with the dam enhancement of 1.5, 1.0 m and without dam enhancement, respectively. Results of this study have therefore provided critical information for making a logical decision concerning the possibility of uplifting the height of the crest of the Dau Tieng dam to mitigate the urban flooding in HCM City under the threat of CC and sea level rise.

Combining rainfall–runoff and hydrodynamic models for simulating flow under the impact of climate change to the lower Sai Gon-Dong Nai River basin

This study presented simulation results of runoff discharge combining the Mike NAM and Mike SHE models for lower Sai Gon-Dong Nai River basin (SG-DNRB). Sai Gon-Dong Nai River basin is Vietnam’s largest population center and main industrial area in Ho Chi Minh City. In recent years, the area faces flooding problems because of heavy rainfalls and high tides, as part of the impacts of climate change and sea level rise. The lower of SG-DNRB was selected as a case study to highlight the necessity to investigate combination of the rainfall–runoff model and the hydrodynamic model for long-term strategies to resource water in the future. The models were calibrated using water level and runoff discharge data during low and flood seasons in 2014. The calibrated results showed satisfactory coefficients (NASH index, R2 up to 0.70 and RMSE is smaller than 0.20). The results confirmed that the combination of Mike NAM and Mike SHE models is well suitable to simulate runoff discharge in the lower SG-DNRB. Combination of the models can be considered a useful tool to help professional agency operator water resources management projects in other areas in the context of climate change and sea level rise.

DISTRIBUTION OF HEAVY METALS IN SURFACE WATER, SUSPENDED PARTICULATE MATTER, SEDIMENT AND CLAM (MERETRIX LYRATA) FROM DOWNSTREAM OF SAIGON-DONG NAI RIVER, VIETNAM

This study aimed to evaluate distribution of selected heavy metals (Cu, Zn, Pb, Cr and Cd) in clams Meretrixlyrata (clam), suspended particulate matter (SPM), water and sediment in the downstream area of Saigon – Dong Nai (SG-DN) River. During March to September 2015, the contamination of those metals at four sampling sites from fresh water to brackish water zone and Meretrix Lyrata clams, which were cultured at many clam farms at Can Thanh beach at Can Gio District, were monitored. The concentrations of metals in clam samples were also determined at a comparative sampling site at Tan Thanh beach (Tien Giang province). Generally, the order of metal concentrations in all environmental components along the SG-DN River was Zn>Cu>Cr>Pb>Cd while the metal concentrations in different environmental components at Can Thanh area were in different orders. According to the results, the increasing tendency of only Cu, Zn and Cd concentrations in SPM and sediment from river upstream to estuary were found. All trace metal concentrations in clam samples were higher than in water and smaller than in sediment and SPM at Can Thanh. Only Cr concentrations in medium and small clam samples had positive significant correlations with those in sediment and SPM (medium size only). In comparison with concentrations of trace metals in water, sediment, SPM and clams at Tan Thanh, those at Can Thanh were higher.

Sanility intrustion in Sai Gon-Dong Nai river system under the effects of the tides and sea level rising in Vung Tau estuary – East Sea, South of Vietnam

A mathematical model was used by the authors (software developed by Dr. F28 Le Song Giang) to study the change of the salt boundary river systems Saigon - Dong Nai under the effect of sea level rise in the different cases for Ho Chi Minh City, taking into account the change of amplitude and phase shift of the South China Sea tide.
 Results of the study indicated that:
 1. There is a pretty good resemblance between model running results and results of water levels measurement. Salinity, calculated results have a larger amplitude slightly from measured data but this difference and oscillation phase can be acceptable.
 2. Salinity 1 g / l - 3 g / l is increasingly encroaching into the infield under the sea level rise scenarios. Salt accounts is greater than 5 g / l and the margin of 10-15 g / l is also approaching deeply, so the future of Ho Chi Minh City will face to some water supply problems.
 3. Saline in basin downstream Saigon - Dong Nai river is quite sensitive to the hydrological regime of the river, therefore, domestic regulation of irrigation reservoirs upstream can be used to push salt and improve salinity regime in the downstream part of the river