[Characteristics of nutrient loss of Lanlingxi watershed in the Three Gorges Reservoir area].

The water flow velocity of part of the tributaries in the Three Gorges Reservoir area has become slower after the water storage period, and agricultural non-point source pollution (AGNPS) is an urgent problem to be solved. Based on a closed catchment of Lanlingxi watershed, the process and the load of nitrogen and phosphorus loss were monitored, and the different ways of nitrogen (N) and phosphorus (P) loss under typical rainfall conditions in watershed scale were compared. The results showed that: (1) The concentration of total nitrogen (TN) gradually decreased with the increasing runoff, and slowly increased after the rain stopped, while the total phosphorus (TP) was contrary to that of TN; (2) The TN loss process had a close relation with rainfall, as TP loss was influenced by the rainfall intensity. N loss was mainly in the form of dissolvable nitrogen, while particle phosphorus was the dominant form for P loss. (3) Surface runoff was the important way of nutrient loss, as interflow greatly influenced the N loss; (4) Various forms of N and P loss showed a significant linear relationship with runoff. (5) The annual TP loss was 28.94 kg x (a x km)(-2) and TN loss was 1040.41 kg x (a x km2)(-1) in this watershed.