Importance of baseline assessments: monitoring of Brunei River's water quality

This study illustrated the changes, pollution status, and significant pollution causes for Brunei River, Brunei Darussalam. Eleven parameters (pH, temperature, oxidation–reduction potential (ORP), dissolved oxygen, biochemical oxygen demand, conductivity, total dissolved solids (TDS), salinity, turbidity, ammonia-nitrogen (NH3-N), and total coliform) were analyzed from eight monitoring sites in 1984, 2019, 2020, and 2021. Box plots were used for a comparative study between 1984 and 2019+ data, while hierarchical cluster analysis (HCA) and principal component analysis (PCA) tests were performed on data from recent years (2019+). The box plot analysis showed that pollution levels in 2019, 2020, and 2021 increased compared to 1984 values, especially for total coliform bacteria. The doubling of the coliform bacteria concentration in the river between 1984 and 2019+ is concerning because the Malaysia National Water Quality Standards (NWQS) guideline values for fishing have now been exceeded. HCA pointed out that upstream stations are more polluted than downstream. PCA of the 11 water quality datasets generated five factors with a total variance of 75.21% and identified anthropogenic activities, seawater intrusion, and hydrological processes as possible causes for Brunei River water quality degradation.