SPATIAL VARIATIONS OF SURFACE WATER QUALITY AND POLLUTION SOURCES IN KHLONG U-TAPAO RIVER BASIN

Multivariate statistical analysis, cluster analysis, parametric analysis, as well as factor analysis was applied to analyze water quality dataset including 9 parameters at 21 sites of the Khlong U-Tapao river basin in Songkhla province, Thailand, from 2007–2015 to investigate spatial variations of water quality and identify potential sources of pollution. Using cluster analysis to classify the three-periods of water quality variation in each monitoring site has shown 3 water quality measures: high, moderate and low. Using parametric study to describe variations of water quality and the significantly identified land use variables affecting water quality, such as urbanization and industrial land use which are sources of pollution in upstream. However, in midstream, Economical urbanization is the pollution source while agricultural land use is the pollution source in downstream. Factor analysis identified that the major pollutants in the upstream were turbidity and conductivity matter from soil erosion in the rainy season and industrial wastewater, in the midstream, the biochemical oxygen demand of organic matters from wastewater discharge from domestic settlements were the main pollutants while in downstream, nutrients from agricultural practices were the major pollutants. From upstream to downstream, bacterial pollutants were the main pollutants from all activities. These results provide fundamental information for developing better water pollution control strategies for the Khlong U-Tapao river basin.