Abstract

This study aimed to analyze the surface waterquality of the Huai Luang River using the water quality index(WQI) method. Five parameters were analyzed to assess thewater quality of the Huai Luang River; they were dissolvedoxygen (DO), biochemical oxygen demand (BOD), total coliformbacteria (TCB), fecal coliform bacteria (FCB), and ammonia(NH3). The Huai Luang River is the municipality’s primaryconsumption water source in Udon Thani province, Thailand.WQI classifications were calculated by using the surface waterquality standards program of Thailand’s Pollution ControlDepartment (PCD-WQI). The results showed that the waterquality in the Huai Luang River was bad status, in the WQIrange of 54-60 scores. The major sources of pollutants in theHuai Luang River were wastewater from communities,agriculture, and animal farms are the main contributors towater pollution. Seasonal water quality variations wereobserved at each monitoring site from March 2022 to February2023. WQI concentration in the rainy season (March to June)was generally among the highest (57 score) compared with otherseasons (56 score in winter and 54 score in summer). While theWQI concentration of the upstream sampling site (domesticwastewater) had the lowest (55 score) compared with the othersites (59 score for midstream and 60 score for downstream).Therefore, this research study presented valuable informationon WQI for the Huai Luang River for water qualitymanagement by administrators and local communityparticipation.