Abstract: Elucidating the spatiotemporal dynamics of water quality and pollutant fluxes in rivers discharging into lakes, along with their impacts and contributions to water quality fluctuations in different lake zones, is crucial for the precise prevention and control of eutrophication and algal blooms. Based on daily automated monitoring data from 2024 collected at sections of eight major rivers in the Lake Chaohu Basin as well as at eight national control stations within the lake body, this study estimated the daily discharge of major inflow rivers such as the Nanfei River using a runoff coefficient scaling model based on water balance. Combined with numerical integration, range analysis, and a spatiotemporal double-dimensional approach, we systematically analyzed the temporal and spatial distribution characteristics of concentrations and inflow fluxes of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₃-N), and other indicators in the inflow/outflow rivers and the lake zones. The response characteristics of each lake section to the pollutant concentrations and inflow pollution fluxes of the major rivers were investigated. The results revealed that: (1) The Hangbu River and the Nanfei River contributed 42.4% and 25.9% of the total nitrogen inflow flux, and 36.4% and 33.0% of the total phosphorus inflow flux, respectively, identifying them as the primary sources of nitrogen and phosphorus pollution in Lake Chaohu. (2) Pollutant concentrations exhibited significant spatiotemporal fluctuations. Temporally, TN and NH₃-N peaked during winter and spring (December to April) due to combined point and non-point source inputs, whereas TP and chlorophyll-a increased synchronously during summer and autumn (June to October) driven by rainfall runoff and algal activity. Spatially, a "high in the west, low in the east" pattern was observed. The western lake zone, affected by high-intensity river inputs and water retention, showed significantly higher concentrations than the central and eastern zones, where dilution, sedimentation, and degradation processes occur. (3) Dynamic response mechanisms of lake water quality to riverine inputs were characterized by synchronous changes and hysteresis effects. These were manifested as a widespread and persistent response for TN, a rapid yet transient one for NH₃-N, and a highly complex response for TP. The complexity of TP was evidenced by its frequent concentration exceedance in the lake compared to the rivers—driven by internal release—and a "dilution effect" where an initial positive correlation turned negative. A significant west-to-east decay in response strength was evident spatially.