[Influence of Optimal Land Use Allocation on Phosphorus Loss in the Process of Rainfall and Runoff].

In order to explore the impact of optimized land use allocation on phosphorus loss in the runoff process of a small watershed in the Three Gorges Reservoir area, a traditional agricultural model catchment area (CG) and a catchment area after optimized land use allocation in the Shipanqiu watershed in Zhong County, Chongqing (EG) were selected as the research object, sampling at the outlets of the two catchment areas, respectively, to monitor the runoff process and different forms of phosphorus in rainfall events and to analyze the influence of land use configuration on the law of phosphorus loss. The results showed that:① in the 10 monitored rainfall and runoff processes, the [total phosphorus (TP)] of EG was lower than that of CG, and the ranges of the two were 0.09-0.75 mg·L and 0.13-2.82 mg·L, respectively. Compared with that of CG, EG significantly reduced the peak value of TP. ② The average EMC of TP, total dissolved phosphorus (TDP), dissolved inorganic phosphorus (DIP), and particulate phosphorus (PP) in the process of rainfall and runoff was lower than that of CG, and EG and CG showed significant differences in EMC of TP, TDP, and DIP (<0.05); the main form of phosphorus loss in the two catchment areas in the process of rainfall and runoff was TDP, but the average TDP/TP of EG was larger. ③ The output load of EG was 45%, 43%, 57%, and 47% lower than that of the TP, TDP, DIP, and PP in CG. The output load of EG and CG of various forms of phosphorus was significantly correlated with the total runoff (<0.01). In addition, the slope of the linear fitting of various phosphorus forms in the CG catchment area to the total amount of runoff was 1.66 to 1.75 times that of EG. The output load of various phosphorus forms of CG was more sensitive to runoff than that of EG, and the output per unit area in the process of rainfall and runoff was more sensitive than that of EG. The amount of sand could have caused the difference in phosphorus concentration and output load more than the output per unit area. Optimizing land use configuration can effectively reduce the loss of various forms of phosphorus and provide a reference for the prevention and control of phosphorus loss in small watersheds in the Three Gorges Reservoir area.