A comparative analysis of phosphate occurrence and its genesis during different dispatching periods of representative level I tributaries of the Three Gorges Reservoir was conducted. For this, water quality, hydrodynamic force, and environmental data were examined for backwater areas of the Xiangxi River and Shennong River during the low-water-level period (June), storage period (September) and high-water-level period (December) in 2018. The results suggest that the mass concentration of total phosphorus (TP) in the water body of the coves of Xiangxi River and Shennong River range from 0.049 mg·L