Abstract: In October 2021, the Danjiangkou Reservoir reached its normal water storage level of 170 meters for the first time, resulting in the formation of a new bay ecosystem in the waters near the Taocha sluice head area. To explore the spatiotemporal distribution patterns of nutrients and their relationships with environmental factors during high water level operation, we selected a typical reservoir bay at Taocha as the research area. Field sampling was conducted in October (initial high water level period) and December (receding high water level period) of 2021. The spatiotemporal distribution characteristics of total phosphorus (TP), ammonia nitrogen (NH₃-N), total nitrogen (TN), permanganate index, and chlorophyll-a in the bay, transitional zone, and main reservoir body were analyzed. The influences of physicochemical parameters such as water temperature, pH, and dissolved oxygen on water quality indicators were also investigated. The results showed that in October, TP and chlorophyll-a exhibited a significant gradient of "bay>transitional zone>main reservoir body, " which attenuated in December. Both TN and NH₃-N were significantly higher in December than in October, reflecting the cumulative effect of inundation during high water level periods. Water temperature and conductivity were significantly negatively correlated with nutrient concentrations, while pH and dissolved oxygen showed significant positive correlations. The study indicates that during high water level operation, reservoir bays are key areas for nutrient release and algal growth. It is necessary to strengthen coordinated management of non-point source pollution control and hydrological regulation to ensure the water quality safety of the source area.