Chiang Mai Journal of Science

        The water quality monitoring of the Ping River was carried out from June 2001-August 2002. Five sampling sites were collected from the upper part to the lower part, along the river. In each site, some physico-chemical and biological parameters were measured twice during each season. According to the monitoring, nutrients and macroalgae levels in benthic form were the major factor measured. Nutrients were mainly analyzed in term of nitrogen compounds and phosphorus compounds. The nutrient concentration of the Ping River increased from the upper to the lower part but diversity of macroalgae decreased along the river. In the upper part of the Ping River, most of the macroalgae were low nutrient and clean environment biomonitor-species. The distributions of macroalgae was directly related to the quality of water and could be used as the biomonitor in the Ping River. The assessment of water quality by using the physico-chemical and biological indicate that the upper part of The Ping River was oligo-mesotriphic status but the middle and lower parts were meso-eutrophic status. Considering the water quality according to the standard surface water of Thailand. The upper part was in second category and the middle and lower part were in third to fourth category.