Nutrient status evaluation for tributary of Three Gorges Reservoir

On the basis of comprehensive applying the methods for making nutrient control standards in domestic and international lakes and reservoirs, an improved comprehensive method for nutrient state index was expressed, and the eutrophication assessment to the tributary of Three Gorges Reservoir was studied. Tributaries of the reservoir were mainly at middle-eutrophication level during the investigation. Among the 30 tributaries, 19 tributaries were at the level of eutrophication, while the others were at the level of mid-etrophication. The average integrated nutrient state index of tributaries was high from April to September, and these tributaries all reached the level of eutrophication. The maximum value of tributaries was 55.43 in August. Tributaries had a higher risk of eutrophication in Spring and Summer. April to September should be a sensitive period which should control the occurrence of eutrophication in the reservoir. The comprehensive nutrient index method proposed was consistent with actual water quality condition of tributaries in Three Gorges Reservoir, and is suitable for eutrophication evaluation of tributaries in Three Gorges Reservoir.