In this study, spatiotemporal fluctuations in surface water quality in Vinh Long province, Vietnam, were conducted using entropy weighting, water quality index (WQI), and multivariate statistical techniques, such as cluster analysis (CA), principal component analysis (PCA), and discriminant analysis (DA). The samples collected at 63 monitoring locations in March, June, and September were measured for 15 parameters. Compared to the Vietnamese standard, surface water was contaminated with organic matters, nutrients, microorganisms, and salinity. DA identified the most typical parameters (pH, turbidity, TSS, EC, DO, Cl−, E. coli, coliform) in distinguishing temporal variations in water quality with greater than 75% of the correction. CA group 63 sampling sites into 22 clusters representing different land use patterns. WQI determined the worst water quality was found in the agricultural areas. Based on the results of entropy weighting, EC, coliform, N-NH4+, BOD, N-NO3−, and Fe had significantly controlled surface water quality. Four principal components obtained from PCA explained 66.45% of the variance, suggesting the influences of geohydrological factors and anthropogenic activities, such as domestic, market area, agriculture, and industry. The findings of this study can provide useful information for authorities to evaluate the effectiveness of monitoring systems and plan for water quality management strategies.

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This paper presents a comprehensive analysis of sea level variations around the Mekong Delta, and their causes and consequences on the environment, based on the tidal records from several stations. The results of the analysis revealed significant spatio-temporal sea level variations along the delta coast. Tidal fluctuations showed their local peaks around the river mouth with shallow bottom areas. The prevailing winds were identified as the factor governing the remarkable seasonal variability of the mean sea levels along the southern coast of the delta. From 1985 to 2010, the relative sea level along the southern coast of the delta rose by about 3.3 mm y -1 . This rate of rise combined with the effect of land subsidence renders the Mekong Delta alarmingly susceptible to frequent inundation. Moreover, the immediate impacts, including saline intrusion and occasional inundation due to seasonal sea level fluctuation, are also found to be critical and require urgent attention. These findings suggest the need to revise coastal management strategies to prioritize the immediate effects of short-term sea level fluctuations and to increase the focus on local management issues such as groundwater pumping causing land subsidence and local sea level trends in addition to the global threats.

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