This study investigated present status of water quality and nutrient loads in the Abukuma River Watershed under normal flow condition. The analysis of routinely measured data showed typical transversal patterns of BOD, TN and TP concentrations along the mainstream, which can be related to the agricultural, domestic and livestock pollutant sources. Water quality in tributaries showed strong correspondence to the land use. NO3-N is strongly related to the percentage of cropland, and BOD, NH4-N and TP to the percentage of built area in each sub-basin. The total nutrient and BOD loads from tributaries and wastewater treatment plants are greatly reduced in the main stream, probably because of the deposition and nutrient uptake enhanced by dams in the mainstream. Phosphorus in the mainstream is likely deposited by chemical and/or physical processes in the flow such as adsorption and flocculation.
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