Seasonal differences in water quality between Lake Taihu and its inflow/outflow rivers in China were studied. Nutrient levels in the rivers were higher than in the lake, with a strong impact on lake water quality. Nutrient concentrations varied seasonally, with the highest levels in the rivers in March and December, and in the lake in July. Heavy rainfall temporarily decreased nutrient levels in the rivers but ultimately increased nutrient loading. Inflow pollution significantly influenced the distribution of water quality indicators in the lake. Factors like wind-induced algae movement and sediment resuspension also affected nutrient levels in the lake.