Abstract: Taking a typical watershed in the Three Gorges Reservoir Area (TGRA) as test object, the AnnAGNPS model was used to evaluate the reduction effects of different cropping, different fertilization level, conservation tillage practice (CTP), conservation reserve program (CRP), and conversion of cropland into forestland program (CCFP) on the output of agricultural nonpoint source pollution (NPS) in the watershed. The simulation results showed that different cropping had no significant difference in the effect of reducing sediment yield, but had significant difference in the effect of reducing phosphorus output. Fertilization level had significant effects on the outputs of total nitrogen and total phosphorus. CTP decreased the sediment yield significantly but increased the nutrient output. CRP reduced sediment yield, but had less effect in reducing nutrient output. CCFP reduced both sediment yield and nutrient output significantly. After the implementation of CCFP, the sediment yield output on the croplands with a slope greater than 10° was less than 5 t·hm^-2, and the nutrient output was within the permissible limit.

Key words: non-point source pollution, agricultural management practice, sediment yield, nutrient, Three Gorges Reservoir Area, functional flow, emergy analysis, system dynamics, scenario analysis, sustainable development.