Backwater regions in tributaries affect nutrient cycling in Three Gorge Reservoirs. Nutrient levels in Caotang River backwater are similar to the mainstream, with nutrients mainly coming from the mainstream. Nutrients are retained by plants in spring and summer, then released in late autumn and winter. This cycle changes how nutrients are transported seasonally. Tributaries impact the nutrient flow in the reservoir, with over 40 tributaries influencing the main nutrient fluxes.