Spatial and Temporal Analysis of Surface Water Pollution Indices Using Statistical Methods

This study was conducted to evaluate surface water quality using pollution indices including the organic pollution index (OPI), comprehensive pollution index (CPI), and water quality index (WQI), cluster analysis (CA), with the support of one-way analysis of variance (One-way ANOVA), and principal component analysis (PCA). Water quality data at 42 locations, with 22 water quality parameters including temperature, pH, turbidity, salinity, chloride, total dissolved solids, electrical conductivity, sulfate, dissolved oxygen, total suspended solids, biological oxygen demand, chemical oxygen demand, nitrite, nitrate, ammonium, orthophosphate, coliform, E. coli , arsenic, cadmium, lead, and copper, were used for the evaluation. The results showed that all the pollution indices fluctuated spatially and temporally. The OPI index ranged from slight organic pollution to heavy organic pollution, and the OPI values in February and April were higher than those in other months. OPI values were classified as moderate with 54.76% of the locations and heavily polluted with 45.24%. Assessment based on the CPI revealed that 16.7% and 83.3% of locations were classified as moderately contaminated and heavily contaminated, respectively. The WQI classified 45% of the locations as poor and 55% of the locations as having average water quality. In particular, the water quality in August, October, and December was better than that in other months. PCA results showed that eight polluting sources were responsible for 77.1% of the water quality variation. The main surface water polluting sources could be natural sources (riverbank erosion, rainwater runoff), wastewater (domestic, agricultural, and industrial), water discharge from the national park, and livestock areas. Local environmental management agencies need to have appropriate solutions to improve water quality. Future research should focus on the contribution sources to surface water degradation.