APPLICATION OF MULTIVARIATE STATISTICAL METHODS TO ASSESS WATER QUALITY VARIABILITY IN BIỂN HỒ LAKE, CENTRAL HIGHLANDS OF VIETNAM
Main Article Content
Abstract
This study applies multivariate statistical approaches, with an emphasis on Principal Component Analysis (PCA), to investigate temporal variability and controlling factors of surface water quality in Biển Hồ (T’Nưng Lake), a volcanic freshwater lake in the Central Highlands of Vietnam. Biển Hồ is a strategic domestic water source for Pleiku City and a sensitive lacustrine system strongly influenced by monsoonal seasonality. High-frequency water quality data were collected from an automatic monitoring station over a five-year period (2020–2024) and aggregated into daily mean values for analysis. Ten physicochemical parameters were examined, including temperature, pH, dissolved oxygen (DO), chemical oxygen demand (COD), total suspended solids (TSS), turbidity, ammonium (NH₄⁺), iron (Fe), manganese (Mn), and salinity.
Descriptive analysis indicates that most parameters remained within the regulatory limits of QCVN 08:2023/BTNMT (Column A), suggesting generally suitable conditions for domestic water supply. Nevertheless, clear seasonal and interannual variability was observed, particularly for TSS, turbidity, Fe, Mn, and DO. Elevated suspended solids and turbidity during the rainy season reflect enhanced surface runoff and catchment wash-off, whereas higher Fe and Mn concentrations during the dry season suggest the influence of internal geochemical and redox-related processes under longer water residence times.
PCA extracted two principal components explaining 48% of the total variance, capturing the dominant hydrochemical gradients of the system. The first component represents a hydro-physical and oxygenation gradient associated with temperature, DO, pH, turbidity, and Fe, while the second reflects a particulate–organic and redox-related gradient dominated by TSS, COD, and Mn. Cluster analysis further identified distinct seasonal hydrochemical regimes, indicating that seasonal forcing exerts stronger control on water quality variability than interannual changes.
Overall, the results demonstrate that multivariate analysis of long-term, high-frequency monitoring data provides an effective framework for elucidating water quality dynamics in tropical volcanic lakes. Although Biển Hồ currently maintains generally good water quality, increasing variability in recent years highlights the need for sustained monitoring to support long-term water security.
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