Spatio-Temporal Changes of Water Quality Characteristics and Pollution Factors in the Chaohu Lake Basin (China)

To clarify the spatio-temporal changes of water quality, pollution factors, and sources in Chaohu Lake Basin over the past five years, this study focused on the Chaohu Lake and its tributaries as the research zone. By analyzing the water quality parameters, the pollution factors of Chaohu Lake were clarified and the water quality was comprehensively evaluated using the water quality index (WQI). Correlation analysis, cluster analysis and principal component analysis (PCA) were conducted in SPSS 26.0 to identify pollutant sources. The results showed that the water of Chaohu Lake and its tributaries were, to some extent, polluted during the dry and wet seasons over the past five years. The primary excessive pollutants were COD, nitrogen, and phosphorus. The average total nitrogen (TN) and total phosphorus (TP) concentrations of Chaohu Lake were 1.74 and 0.09 mg/L in dry seasons and 1.39 and 0.08 mg/L in wet seasons, respectively, which belonged to Class IV water quality standard regulated by GB 3838-2002. Notably, in the Nanfei, Paihe, and Baishishan Rivers, TN concentrations consistently exceeded the Class V water quality standard threshold in both seasons, while TP levels exceeded the Class IV standard. Water quality assessment revealed that the water quality state was classified as “good” in Chaohu Lake, but “moderate” in its tributaries, especially in wet seasons. This finding indicated that while eutrophication remained the primary pollution issue in the lake, the overall physicochemical condition of the water body has not undergone comprehensive deterioration and still maintains a certain degree of ecological health. Source analysis indicated that domestic and industrial wastewater, and agricultural activities were the primary sources of pollution in Chaohu Lake and its tributaries. Therefore, integrated management strategies are required, including enhanced monitoring and control of nitrogen and phosphorus inputs from inflow rivers, rational industrial restructuring, and optimization of agricultural and industrial water use.