Table of contents

Preface

Since the Doi Moi policy launched in 1986, Vietnam opened up the country's economic liberalization over the past 3 decades. While achieving remarkable economic growth, Vietnam has faced considerable challenges in environmental and resources management. The rapid growth of urbanization and industrialization has placed an increase in pressures on the environments and available resources, through excessive exploitation and use. Further, the utilization, management and use of environment and natural resources have increasingly drawn much attention from both researchers and managers under the effects of global climate change impacts. The application of advance technologies and management practices have become a vital of concern in the age of the 4^th industrial revolution with an emerging of advance technologies.

We would like to welcome you to the International Conference on Environment, Resources and Earth Sciences (ICERES 2020) in associated with the National GIS Conference 2020 (GIS for Smart Cities towards Sustainable Development) which the will be held during 1 – 5 December 2020 at Ho Chi Minh City University of Technology (HCMUT), Vietnam National University Ho Chi Minh City. ICERES 2020 is co-organized by HCMUT, Nong Lam University (NLU) and Esri Vietnam in which. The Conference is financially supported by Ho Chi Minh City University of Technology, Vietnam National University Ho Chi Minh City, Nong Lam University and Esri Vietnam.

The main objective of the conference is to provide a platform for researchers, academicians, engineers, businessmen, managers, and postgraduate students in the field of environmental and resources management, geospatial technologies, and earth sciences to present their recent studies and latest research results. In addition, this conference aims to provide a setting environment for scientists and managers to exchange new ideas, innovative thinking, and to explore applicable experiences via face-to-face discussions, as well as establishing collaborative research projects or business relations, and to enable partners for their future collaborations.

The conference program was organized into ten (10) sessions covering topics of environment and natural resources management, geospatial technologies, and earth sciences, imcluding: Smart Cities, Digital Twin Cities (Cyber Cities), Smart Building; (ii) Application of GIS in State Management; (iii) Disaster Reduction and Risk Management; (iv) Environment, Natural Resources Management and Sustainable Development; (v) 3D GIS, Laser Scanning, and Ground Penetrating Radar (GPR); (vi) Digital Imagery Processing (Satellite, UAV, Air plane); (vii) IoTs, AI, and Big Data for WebGIS; (viii) Integration of Lidar and GIS; (ix) Building Information Model (BIM) Technology; and (x) Global Navigation Satellite System (GNSS). Overall, the conference has attracted more than 138 papers, and among them, 46 high-quality papers were recommended to submit for the IOP Conference Series: Earth and Environmental Science proceedings book for peer-reviewing. Then, the double-blind review process was carried out for the 46 papers, in which each paper has been reviewed for its merit and novelty by at least two reviewers and one editor by matching the content areas. As a result, a total of 25 papers have been finally selected for this proceedings book. We believe that this proceedings book provides a broad overview of recent advance studies in the fields of environment, natural resources, disaster reduction and risk management, sustainable development, geospatial technologies (GIS and remote sensing) and earth resources for readers.

Finally, we would like to express our sincere thanks to (i) Department of Science and Technology – Vietnam National University Ho Chi Minh City; (ii) the Rector of HCMUT (Assoc. Prof. Mai Thanh Phong); (iii) the Rector of Nong Lam University (Prof. ) for their help and assistance in administrative works and other supports. Special thanks go to Kayleigh Parsons for always responding promptly. We would like to thank all the reviewers for their timely and rigorous reviews of the papers and thank all the authors for their submissions.

Ho Chi Minh City, November 2020

Armando A. Apan

Le Van Trung

Nguyen Kim Loi

Vo Le Phu

Tanita Suepa

Garik Gutman

Nguyen Danh Thao

Le Van Thang

Vo Quang Minh

Lam Dao Nguyen

List of Scientific Committee are available in this pdf.

All papers published in this volume of IOP Conference Series: Earth and Environmental Science have been peer reviewed through processes administered by the Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

• Type of peer review: Double-blind

• Describe criteria used by Reviewers when accepting/declining papers: The reviewers accept or decline the manuscript based on the scope of the conference, the originality of idea, the scientific content of the work, and the English writing of the manuscript.

Was there the opportunity to resubmit articles after revisions?: The editorial board based on the recommendation of the reviewers (e.g. Publishable without revision (No Revision), Publishable after a few revision (Minor Revision), Publishable only after correcting as recommended, HUGE Revision must be done (Major revision), and REJECT) to decide that the manuscript should be revised or rejected. Once rejected, there has not been any changed for resubmission.

• Conference submission management system: via EasyChair system

• Number of submissions received: 138 (for the whole conference), 46 (selected and invited for IOP submission)

• Number of submissions sent for review: 28

• Number of submissions accepted: 25

• Acceptance Rate (Number of Submissions Accepted / Number of Submissions Received X 100): 54.3%

• Average number of reviews per paper: 2

• Total number of reviewers involved: 28 (19 responded)

• Any additional info on review process (ie plagiarism check system): None

• Contact person for queries: Assoc. Prof. Le Van Trung Ho Chi Minh City University of Technology - Vietnam National University Ho Chi Minh City (lvtrung@hcmut.edu.vn)

Rice production in Vietnam has been developing rapidly and sustainably in recent years, contributing to ensuring national food security. However, it is facing the effect of climate change, sea-level rise, salinity intrusion, drought, and flood which threatens food production, especially in the Vietnamese Mekong Delta. For this reason, building a tool that allows estimating rice yield is necessary. SAR (Synthetic Aperture Radar) remote sensing data from Sentinel-1 satellites is provided by European Space Agency (ESA) with no cost, large coverage, and high spatio-temporal resolution, which has the advantage of observation in cloudy, foggy, rainy weather and independent of solar radiation. Therefore, this data is suitable for rice monitoring in countries with tropical monsoon climate like Vietnam. This paper presents the results of estimating the Winter-Spring rice yield in 2018 by using multitemporal Sentinel-1 data with C-band. The estimated rice yield was compared with the in-situ yield, which shows that the average values of the samples of estimated and surveyed yield were equivalent with 6.5 ton/ha and 6.6 ton/ha respectively, and the standard deviation between the estimated and surveyed yield was 0.80 ton/ha. The results demonstrate the applicability of the multitemporal SAR Sentinel-1 data for estimating rice yield in the study area, An Giang province, the Vietnamese Mekong Delta.

Different spatial resolutions of optical satellite imagery provide different details in land use/land cover (LULC) mapping. Therefore, it is essential to decide the appropriate classification system for specific spatial resolution. This study used the same classification system to extract land use/land cover for District 2 and District7 of Ho Chi Minh City, Vietnam in 2018 from two different spatial resolutions, Sentinel-2 (10 m) and VNREDSat-1 (2.5 m), images. Using the same set of ground truth data, the accuracy of the classified maps was assessed to select the right image for the study area corresponding to the given classification system. The outcomes revealed that both optical satellite images produced high overall accuracy (83% for Sentinel-2 images and 86% for VNREDSat-1 images) on the same classification system. It is easier to classify the cropland, grassland, roads, and industrial zones with VNREDSat-1 image whereas perennials, bare land, and aquaculture were easily classified with Sentinel-2 due to their homogeneity at a lower spatial resolution. This shows the importance of choosing the right spatial resolution following the requirements of the classification system.

Danang is a coastal city in the Central Region, VietNam which is considered as a sensitive area under the high risks of natural disasters and climate change. Located in downstream of Vu Gia - Thu Bon river system, Da Nang city is often inundated in flood season. Hoa Vang district is considered as the most flood damaged region in Danang City due to its location and topography. Assessing socio-economic vulnerability of floods is important in the management of natural disaster risks, from that developing solutions to mitigate the damage caused by floods. This study develops a flood vulnerability assessment method for the Hoa Vang district, Danang City based on the Geographic Information System (GIS). Through analyzing the inundation situation and local socio-economic conditions, the research has selected and developed a set of criteria to assess the flood vulnerability for the study area and presented in GIS environment. Based on the spatial analysis methods in GIS, the study has identified Flood Vulnerability Index (FVI) and generated the flood vulnerability map for Hoa Vang district, Danang city. The results from this study are important in order to propose the solutions for responding to flood hazard in Da Nang City.

Large urban areas are currently facing the problem of increasingly serious air pollution, which greatly affects human health and economic development. The sources of air pollution are mainly from industrial activities, transportation and human activities. Air pollutants data can be monitored and extracted from remote sensing images. This research aims to assess the level of NO₂ and SO₂ pollution in the air from data collected by OMI (Ozone Monitoring Instrument) on AURA satellite of A-Train group. Pollution levels of NO₂ and SO₂ will be calculated, assessed. Then, a map illustrating the trend of NO₂ and SO₂ in Ho Chi Minh City during the period of 2015-2019 will be made. The results of the study showed that NO₂ concentration varies significantly with the seasons, relatively high in the dry season reaching 70 (μg/m³) and decreasing in the rainy season. The concentration of SO₂ varies relatively evenly in the area and increases in industrial areas with concentrations ranging from 0.1 to 1.37 mg/m³. Therefore, it is necessary to speed up the rapid monitoring of air pollution in urban areas and large cities in order to get accurate, fast and timely air pollution information to have more appropriate and effective mitigation and prevention measures.

Groundwater in the Southeastern coastal region of Vietnam is exploited for many purposes, including irrigation, livestock, domestic and production activities. In this study, Groundwater Quality Index calculated by Entropy weight method (EWQI) and Geographic Information System (GIS) are applied for zoning water quality through determining the weight of each parameter in accordance with the variation of each value in terms of. Spatial distribution the suitability of groundwater use in the study area. Groundwater samples were collected from 46 wells in the dry and wet seasons in 2018 for analyzing seven selected water quality parameters, including: pH, total dissolved solids (TDS), total hardness (TH), ammonium (NH₄⁺-N), nitrate (NO₃⁻-N), sulphate (SO₄^2-) and ferrous (Fe²⁺). The groundwater quality is divided into five (05) categories corresponding to Entropy Water Quality Index (EWQI), comprising: excellent, good, medium, poor and extremely poor. The analysis results of Entropy weight indicated that pH, NH₄⁺-N, NO₃⁻-N are the most affected on the quality of groundwater at the study area. According to EWQI results, more than 41.30% of wells' water quality are "very good" in both the dry and wet seasons, mainly in the coastal of Ba Ria - Vung Tau province and 13.04% of the total surveyed wells in the study area are "extremely poor", mainly in Ho Chi Minh city. Accordingly, the zoning map of Entropy weighted Water Quality Index (EWQI), showed that the area with good quality of groundwater accounts for 34.3% and 37.72% of the total study area in the dry and the rainy season, respectively.

Saltwater intrusion is widely observed in coastal aquifers because fresh groundwater is over exploited and abstraction wells were installed too close to saltwater intrusion zone. Identification of salt/fresh groundwater interface is important for fresh groundwater protection. This study presents an application of combination groundwater investigation methods including vertical electric sounding (VES), geochemistry and geographic information system (GIS) tools for delineation of salt/fresh groundwater interface in Mekong Delta. Twenty-seven groundwater samples are collected in existing wells for chemical analysis. Vertical electric sounding (VES) method was conducted for 37 sites to delineate freshwater zone (TDS <1g/L) and saline groundwater zone (TDS>1 g/L). Two new wells are also installed after VES measurement for groundwater sampling. Result of geochemical analysis show that TDS values of groundwater samples range from 0.25 g/L to 1.3 g/L and Cl from 8.8 to 758.6 mg/L. Electrical resistivity values range from 2 to 18.4 Ωm. The electrical resistivity values less than 10.4 Ωm is well correlated to saline groundwater. The study shows that even though VES can be an effective tool for identification of fresh/saline groundwater distribution, the method could not identify the saltwater intrusion zone. Combination of geochemical and GIS methods can clearly delineate saltwater intrusion zone. The study results show that fresh groundwater is limited in a small area of upper-middle Pleistocene aquifers. The fresh groundwater is highly affected by salinization. Therefore, the area urgently needs to take proper measures for sustainable groundwater development.

In 2019, Ho Chi Minh City has a total population of 8.99 million with GRDP around 6.021 USD/year [1]. Given the population size and the above GDP level, the electricity consumption demand for production and living purposes in the City was 83 million kWh per day in 2019 [2]. With high electricity demand, it must have developed the rate of renewable energy supply. And in Tan Binh district area, the population is considered quite high and is one of the economic development areas of the city. In Ho Chi Minh City, the sufficient supply of electricity is the top concern. And Tan Binh district is one of 24 districts belong to Ho Chi Minh City with crowded residential and industrial parks, that also has 1-2 houses applying solar energy. In there, solar energy is developing with industrial scale in many enterprises. So, this research was initial survey the potential using solar energy for household and the challenges of resident in Tan Binh district about applying solar energy for their home. According this study, now there is 1 house using and rating positively about solar energy combine national power grid. Around 92% people (1,500 interviewers in 15 wards) think that using solar energy is potential applying in their home because it gains the economic efficiency for reducing electricity fee. But it's only 23% household interested in using solar energy in their house, when 50% citizens unsure about that. As the results, the factors effective their decision are the policies support from national government about using solar energy and the increasing of electricity bill. It's a point for encounrage the applying solar energy in household scale in Ho Chi Minh.

The Can Tho River plays an important role in ensuring water supply for life and socio-economic activities of Can Tho city. The problem is that the water supply and water demand in the future are difficult to predict. Therefore, it needs an approach which is capable of analyzing the water balance. This study aims to identify the impact of climate change and socio-economic development on the water balance and water quality in the future (2030s and 2050s). We used the Vietnam Water Quality Index (VN-WQI) as an analysis tool and the Water Evaluation and Planning (WEAP) model. Results show that in the period of 2010-2019, both water quality and quantity of the Can Tho River can still meet the water demands. However, the Can Tho River will not be able to use due to pollution of BOD, COD and NH₄⁺-N matters in the future. The water demand increases significantly under the impacts of rapid urbanization and industrialization. Thus, this also increases wastewater discharged into the Can Tho River. The surface water of the Can Tho River is projected to be declined under the impacts of climate change. We found that the water supply is much higher than the water demand in Can Tho city, so the water quality is the deciding factor for different purposes.

Vietnam is a country that is heavily affected by global climate change, with the coastal zone and low-lying river deltas being especially vulnerable. The coastal zone has rapidly evolved over the past few decades, as coastal tourism and other social-economic developments and industries all seek fortune and exploit resources in this area. Along with this rapid economic growth, the coastal zone has suffered severe impacts of both human activities and global climate change, resulting in an increasing number of coastal hazards, such as typhoons, floods, saline intrusion, and coastal erosion. The purpose of this paper is to identify natural and human factors that affect coastal erosion through case studies in the south-central coastline. Measures for minimizing threats to both socio-economic activities and the surrounding natural environments are brought forward, in which integrated coastal zone management approach plays a key role. In addition to addressing the issues and potential management strategies, selected coastal areas in Vietnam characterized by severe coastal erosion are studied in terms of coastline dynamics, changing beach morphologies and coastal engineering structures through on-site measurements and aerial images. Seasonal variations and changing beach morphologies after the construction of coastal engineering works are clearly visible.

Nowadays, antibiotics are used with increasing frequency to meet the needs of human life. The excretion of humans and animals in the livestock industry into the environment generates emerging pollutants with a potentially high risk for cancer, antibiotic resistance, and ecological imbalance. Among strategy for antibiotic removal, advanced oxidation processes such as photocatalysis using TiO₂ material is a promising technology. This study is aimed to optimize the operational factors for removing enrofloxacin from water using TiO₂ photocatalyst under UV-A irradiation. The experiments were designed with 30 experiments and 6 center repetitions to test the effects of initial enrofloxacin concentration, catalyst dosage, reaction time, and solution pH on the treatment performance. An optimal condition was found at the catalytic dosage of 1.0811 g/L, the initial enrofloxacin concentration of 21.405 mg/L, pH 5.946, and the reaction time of 120 min. Under these conditions, the enrofloxacin was almost eliminated. It can be concluded that the photocatalysis with TiO₂ is fully capable of thoroughly treating enrofloxacin in water.

This paper describes a new approach for urban land use management by using Unmanned Aerial Vehicles (UAV). Experimental result covers 121 ha (1.21 km²) at Binh Tho ward, Thu Duc district of the Ho Chi Minh city and shows that UAV technology is most suitable and cost effective for cadastral mapping and updating the database with high accuracy. In this research, 36 GCPs (Ground Control Points) and 2433 parcel boundaries (GIS data) were used to compare the achieved accuracy of UAV method in which 10381 orthophoto imageries produced had a resolution of 1.8 cm (with flying altitude 70 m) to be used to inform urban database. This technology opens a new way that is most suitable and cost effective for small areas, where digital maps and 3D models need to be produced in a short period of time with high data quality and accuracy. There are no significant barriers to imbed the technology at the local level and it can speed up the process of updating database in developing the Spatial Data Infrastructure (SDI) of the smart city.

In recent years, Ho Chi Minh City has been faced with stark challenges in urban flooding affected by the impact of climate change in associated with the rapid urbanization and unadequate urban planning. Although many flood mitigation solutions were invested and implemented such as upgrading drainage systems, transport infrastructure, flood control pumps, etc. the problem remains unsolved and even worse. The purpose of this study is to propose a calculation model of the sustainable urban drainage system (SuDS) integrated with of GIS and remote sensing technology to assess and predict flooding degree in a specific basin in HCMC. Further, the results of this calculation model are just a pre-testing and pre-simulation of the proposed model for future studies on the application of sustainable urban drainage techniques, including rainwater harvesting, green roofs, urban green space and pervious pavement.

In natural water, colloidal particles play an important role in the transport of organic compounds, including pollutants. The analysis of colloidal particles creates more bases for the selection of river water treatment technology, making the treatment more efficient. In this study, the size and zeta potential of colloidal particles in Saigon river water were determined. Seven sampling sites were randomly selected along the river length in Ho Chi Minh City. One of the locations was selected to investigate colloidal properties at different times (i.e. 10 samples). The results showed that the colloidal particles have poor stability with Zeta potentials in the range from -19 mV to -12 mV. Besides, statistical analysis showed that the zeta potential had an inverse correlation with the pH value and the permanganate index with the significant coefficients of -0.67 and -0.73, respectively. The size of colloidal particles in water is not uniform; however, due to poor stability, part of the particles join together and settle down. Coagulation-flocculation-sedimentation-rapid sand filtration experiments were also performed to remove colloidal particles from the water. The treated water has low turbidity with a removal efficiency of 97%. This shows that the colloidal particles presented in the Saigon River water could be easily removed by the traditional physicochemical method. However, the parameters of the permanganate index and Coliforms did not meet the standard of QCVN 01-1/2018/BYT for drinking purposes, which still require further treatment.

In the Ba river basin, the natural forest area has been decreasing and agriculture area has been increasing at an uneven rate for the last 30 years. Objective of this research is analysing the change in the agricultural and forest areas under the impact of socioeconomic activities in this basin. Landsat satellite images with a resolution of 30 m acquired from 1989 to 2019 were used to assess the changes. To enhance the classification speed of data, this research applied the online Google Earth Engine platform and GIS tools to process and edit results. The results showed that the largest decrease in forest area was from 1989-2000 (-159,000 ha) while the agricultural area increased the most in the period 2010-2017 with more than 176,000 ha. The main reasons of conversion forest land into agricultural land such as fruit trees and perennial industrial crops were the increasing of population and agricultural prices. Besides, the demand of electricity caused the deforestation for hydropower plantations.

This study used 487 MODIS MCD43A4 images, 1-day resolution, 500-meter spatial resolution to evaluate the efficiency of using the MODIS image series in monitoring the rice planting calendar in the Mekong Delta in 2019. The Savitzky-Golay filter method was applied to eliminate noise and smooth the time series of NDVI imagery. The rice plating date was then determined using TIMESAT software based on the threshold of increasing NDVI to 20% of the amplitude each season. The reliability of the model for mapping rice planting calendar was evaluated by compared to field data and local statistics. The results showed that the series of MODIS MCD43A4 images was used effectively in map of rice planting calendar for the Winter-Spring season, with area error was less than 10% and different of sowing date was less than 15 days (N = 21, MAE = 15 days, RMSE = 18 days). However, the series of MCD43A4 images was limited in monitoring the rice crop calendar of the other two remaining seasons (Summer-Autumn and Autumn-Winter) with an area error was greater than 30% and a higher difference in the time of sowing compared to the Winter-Spring season, especially in the Autumn-Winter season (N = 20, MAE = 22 days, RMSE = 23 days). The above results showed that the MODIS image series was effectively used in the dry season (Winter-Spring) and limited in the rainy season due to the influence of weather and clouds. Further studies combining the use of other types of satellite images or methods to replace cloud-affected pixels needed to be taken into consideration.

This study tested solutions aiming to improve the estimates of tropical forest stand volume (SV) for the large area using SPOT 5 data and field data. Firstly, forests were stratified into four forest strata using a hybrid classification of ISODATA (Iterative Self - Organization Data Analysis) unsupervised, and Maximum likelihood supervised (MLC) based on SPOT 5 image and field data. A set of 111 sample plots was distributed in these four forest strata, which represented disturbed forests under different levels by human-induced. Within the sample plots, diameter at breast height (DBH) and tree height (H) were measured to calculate standing volume using the SV equation from the previous study for the area. The method of k-NN (k-Nearest Neighbour) was applied to estimate the stand volume for different datasets of SPOT 5 bands, normalized difference vegetation index (NDVI), and combination of SPOT 5 bands and NDVI. The estimates were separately tested for the whole area and each forest stratum. Leave one out cross-validation method was employed to validate the quality of the predictions. The results indicated the accuracy of the estimate was significantly improved when applying for each stratum comparing to for the whole area with both SPOT 5 and NDVI data. The lower errors were found in the forest strata that are fewer disturbances than the heavily degraded stratum. Among the image data, the estimates were based on the NDVI give a lower accuracy compared to others.

Land use/land cover (LULC) changes may lead to vulnerable land resource and imbalanced ecosystem. This paper aimed to identify the change of LULC in the center of the Ba river basin. As well, the risk of land use change (LUC) was assessed based on remote sensing data and Analytic Hierarchy Process to determine the areas where LULC can modify with varying degrees. The LULC and Normalized Difference Vegetation Index (NDVI) data processed from Landsat images on Google Earth Engine platform were overlayed to create a zoning map of LUC risk levels in dry season of 2010 and 2020. Over 10 years, the largest increased area was bare land with a growth of 4.98%; whereas the most reduced area was shrub with a decrease of 4.21%. Forest area accounted for the highest proportion of the whole area. LULC classes and NDVI values were assigned different risk weightages to produce the risk distribution map of LUC levels and susceptible areas. The results revealed the most risk zones (High and Very high) constituted more than 50% and stayed steadily from 2010 to 2020, in which shrub areas were partially transformed to bare land or agricultural land due to economic development.

Groundwater in Xuyen Moc district is currently exploited for many purposes such as irrigation, domestic, production and livestock activities. In this study, the health risk assessment (HRA) method was used to determine the risks of public health for local people consuming groundwater for their domestic purposes by using the hazard quotient (HQ). This method calculated HQ of parameters exceeding the allowable limit in drinking water through monitoring data and the survey of households in the study area. Fourteen (14) groundwater samples were collected in the dry and wet seasons in 2017. Eleven (11) water quality parameters (pH, total hardness, TDS, SO₄^2-, Cl⁻, NO₃⁻, F⁻, Mn²⁺, Fe²⁺, Zn²⁺ and Pb) were selected for analysis. Results of calculation of HQ showed that fluoride is a parameter affecting the health of children when using groundwater for a long-term (HQ > 1). HQ values ranged from 1.9 to 2.2 through ingestion of water and HQ through the dermal absorption ranged from 4.710⁻⁴ - 8.610⁻⁴.

Environmental quality (EQ) has always been paid more attention in big cities, where urbanization is on the rise because it greatly affects urban natural ecosystems and people's health. The paper presents the results of applying Landsat satellite images to evaluate the Natural Environmental Quality (NEQ) from the integrated index NEQI (Natural Environmental Quality Index) through the calculation of biophysical variables, including vegetation index NDVI, water surface index NDWI, construction index NDBI and land surface temperature LST. The study area is the north of Ho Chi Minh City (HCMC), divided into 3 sub-regions for analysis, including 13 old inner-city districts, 6 new inner-city districts, and 4 suburban districts. The results showed that there is a difference in NEQI between inner and suburban areas. Low NEQI is concentrated in urban areas with high urbanization rate, industrial zones, areas with large impervious surface areas and low greenery density. In the suburbs, in contrast, NEQ is better than in the inner city. If considering by the acquisited time of two satellite images in February of 2005 and 2020, the NEQ of the study area showed signs of decreasing and gradually expanding area from the inner city to the suburbs. Particularly in the suburbs, due to the urbanization process in recent years, there are spontaneous and unplanned development areas, so NEQ has changed towards a decrease. The results of the study can be used to support urban environmental planning and management.

Drought is one of a major natural disaster that causes tremendous damage to the ecological environment and social-economic in the Vietnamese Mekong Delta (VMD). Drought characteristics are invaluable knowledge for better management of water resources and agriculture production, especially under climate change context. This study investigated the spatiotemporal trend, intensity, duration, and frequency of meteorological droughts over VMD by using the Standardized Precipitation Evaporation Index (SPEI). The SPEI at multiple time scales (3, 6 and 12 months) are determined by using the monthly precipitation and temperature data between 1985 and 2018 obtained from ten meteorological stations in VMD namely Ba Tri, Cang Long, Soc Trang, Bac Lieu, Rach Gia, Ca Mau, Chau Doc, Can Tho, Cao Lanh, and My Tho. SPEI detected ten extreme drought events from 1985-2018 that matches with the historical extreme drought events reported in VMD. It means SPEI could be a useful indicator to support for drought management and mitigation in the future. The extreme drought event from October 2013 to September 2016 was the highest intensity and most prolonged duration from 1985-2018. The El Niño is considered to strongly influence on extreme drought events in VMD as all extreme drought events are highly associated with El Niño periods. The intensity, duration and frequency of drought events increased from 1985 to 2018. Drought events are more severe in VMD in recent years. Extreme drought also tends to cover for over VMD region. Adaption measures are essential to cope with drought disaster, especially in the agricultural and aquacultural sectors.

The current study used a combination of Sentinel-1A (SE-1A) radar and Sentinel-2A (SE-2A) optical images in mapping land use/land cover (LULC) in Dak Nong province in 2018. The Random Forest (RF) algorithm was adopted to digitally categorize Landsat images into LULC maps according to ten different LULC classes included: evergreen forest, semi-evergreen forest, deciduous forest, plantation, rubber, industrial plants, crop land, residential area, water surface and others. The results indicated an overall accuracy (OA) and kappa coefficient of 81.40%, Kappa = 0.79, respectively. Based on the results of classified image, a 2018 LULC map of the study area was simulated. Accordingly, the natural forests account for 34.27% of the total area of the province, distributed scattered in districts. In which, the evergreen forest occupies the highest area with more than 166.600 ha, equivalent to 74.54% of the total natural forest area, and concentrated in the high mountain areas. Non-forest covers occupy more than 63% area of Dak Nong province. The industrial and agricultural cropland indicated a high area in the study area with a rate of 34.82% and 11.38%, respectively. This shows a strong development in the scale of industrial and agricultural crops in the study area. The objective information on current land use/land cover in this study can serve as the basis for policymakers to orient the local forest resource sustainability strategies. Besides, the study also shows that the use of a combination of Sentinel-1A radar and Sentinel-2A optical image to classify and construct the LU/LC map is a high-efficiency research direction.

Trend detection in rainfall time series is a prime task to provide reliable outcomes for better planning and management of water resources under climate change. This study investigated the rainfall trends in seasonal and monthly rainfall over Vietnam, using high-resolution gridded datasets from 1980 to 2010. Possible trends in rainfall values were detected by a recently proposed Innovative-Şen Analysis (ITA) method, which allows identifying the trends of the low, medium, and high values of a series. The outcomes showed high domination of significantly increasing trends in annual rainfall. Moreover, the analysis of partial trends in the time series identified a sequence of alternating decreasing, increasing, and trendless seasonal and monthly rainfall. On the other hand, opposite trends were found for extreme rainfall, in which the high values in the rainy season showed negative trends, while the positive trends of low values in the dry season were indicated. Besides, based on categorization, the low, medium, and high monthly rainfall values of the seven sub-regions were mainly evaluated, which occurred in different trends. The high values in monthly of the rainy season had also detected an upward trend, and the low values in monthly dry season existed downward trends that are expected that these results will be associate with rainfall trends with floods and droughts. Besides, the study showed that the ITA method could be successfully used in trends analysis for gridded datasets of rainfall variables.

GIS and Remote Sensing technology had been widely applied in Viet Nam. However, research orientation and development of Web GIS and Remote Sensing solutions for regional management approach also indicates many difficulties and challenges. This paper aims to introduce Web GIS and Remote sensing solutions that can be used in monitoring salinity intrusion and land cover mapping to support the implementation of sustainable development strategy of the Mekong Delta region. The experimental results show the online mapping applications based on Landsat images open a new way that can be effectively applied in monitoring salinity intrusion in river network, updating the status of land cover changes and analysing the trend of forest-cover changes in this region. Results of this study also illustrate the suitable technology available to support regional organizations to create thematic maps in monitoring and managing the natural resources and environment of provinces/cities that can achieve high accuracy and save time.

The reverse osmosis (RO) water desalination system powered by the photovoltaic (PV) unit is commonly used to produce drinking water due to their reasonable price. This review focused to display different designs of small-scale PV powered brackish water RO (PV-BWRO) systems that were installed to improve the water productivity at remote areas. The configuration of BWRO units, which determined the operating cost, permeate flow and amount of rejected water, is of great concerns in this work. The specific energy consumption (SEC), total capital cost and water production cost are also analysed to display the feasibility of application of PV unit for small-scale BWRO desalination system. The single-stage configuration was suitable for most of small-scale BWRO systems owning high recovery rates (i.e., higher than 50%). The PV solar system pairing with batteries was not recommended at production capacities below 5 m³ for their high cost and short lifetime. Independently operated PV-BWRO systems required the highest capital cost while produced the lowest operating and overall production costs compared to hybrid systems.

Vietnam's urban areas have faced with serious environmental pollution issues, including: water pollution, municipal waste and air pollution. Air in Ho Chi Minh city is polluted by PM_2.5 (particle matter with the diameter is less than 2.5 μm, so-called PM_2.5), O3, CO, NO2 and TSP which greatly affects public health. In 2017, Ho Chi Minh City (HCMC) had 8,640,000 inhabitants with a total of 7,339,552 motorcycles and 637,323 automobiles. There are about 2,500 factories, 2,061,957 household and 5,096 restaurants in the city. The aim of this study is to (i) conduct a detailed air pollution emission inventory for PM_2.5; (ii) stimulate PM_2.5's dispersion in HCMC and (iii) propose mitigation measures for PM_2.5 in the city. Simulations of air pollution were conducted in HCMC by using TAPM-CTM system model. The model performance was evaluated using observed meteorological data at Tan Son Hoa station and air quality data at the Ho Chi Minh City University of Science. The result states that the sum of air pollutants from main sources of disposal in HCMC is 3,978.32 ton of PM_2.5 in 2017. Average maximum 1 hours, 24 hours and annual of PM_2.5 concentration in 2017 does not exceed QCVN 05:2013/BTNMT, but it is 1.3 to 2.3 times higher than the WHO's guideline. Therefore, the PM_2.5 in HCMC impacts on public health of HCMC. To control and manage the air's quality and minimize the generation of PM_2.5 in HCMC there are possible solutions such as the control of air pollutants from the main source, the creation of encouraging policy, the regulation of air pollutants in HCMC and the raising people's awareness of environmental protection.