| In response to substandard water quality observed in parts of Xishuangbanna Prefecture, this study assessed the water quality status of major rivers, including the Nanguo, Liusha, Nana, Luosuo, and Nanla Rivers. The spatial distribution of pollution sources was analyzed, and the MIKE11 model was employed to estimate the water environmental carrying capacities for chemical oxygen demand (COD), ammonia nitrogen (NH?-N), and total phosphorus (TP) across designated control units. Strategies for the control and reduction of both point- and nonpoint-source pollution were also proposed. Results show that COD pollution primarily originates from urban domestic sewage (37%), rural domestic sewage (26%), and livestock and poultry farming (25%); NH?-N predominantly stems from urban domestic sewage (60%); and TP mainly arises from agricultural nonpoint sources (49%). The calculated carrying capacities for point sources are 14,657 t/a (COD), 1,274.35 t/a (NH?-N), and 167.80 t/a (TP), while those for nonpoint sources are 35,278 t/a (COD), 3,291.36 t/a (NH?-N), and 367.61 t/a (TP). Specifically, TP concentration in the Nanguo River (from the prefectural boundary to the Nagouba section) and both COD and TP concentrations in the Nanla River (from upstream to the Mengpengchahe section) exceed the total allowable loads for nonpoint-source pollution, requiring reductions of 2.01 t/a, 182.40 t/a, and 22.24 t/a, respectively. Overall, water quality of major rivers remains relatively good; however, exceedances during the rainy season are primarily driven by agricultural runoff and livestock farming. Strengthening soil testing (i.e., precise fertilization practices) and enhancing the utilization of livestock and poultry manure are recommended to effectively mitigate nonpoint source pollution. This study provides a scientific basis for water environment management and supports the implementation of the River Chief System (RCS) in Xishuangbanna Prefecture. |
