The water quality in the Nansi Lake basin has improved significantly over five years. The levels of pollutants like CODCr, NH3-N, TP, and TN have decreased by around 45-85%. The overall pollution index has dropped from 11.4 to 4.0. TN is the main pollutant in the area. The water quality is close to meeting standards for fish habitat. To continue improving, we need to focus on controlling pollution sources, especially non-point sources, and target the main polluted rivers and pollutants effectively.