The study of the rate loss of nitrogenous non-point source pollution loads in different precipitation levels

A SWAT model was calibrated using data from runoff, sediment and nitrogen pollution in 1998 in the Heihe river basin. The conception of rate loss in the watershed (RL) for non-point source pollution loads was presented, and the RLs of farmland, town, grass, bush and forest were calculated under different precipitation levels. The comparative study of the RLs of N pollution which was calculated by two methods (the SWAT model and the export coefficient method) was also shown; the correlation numbers were up to 0.9 (the significance level is 0.005). In the end, it was demonstrated that the different adsorptive N RLs for different land uses in descending order were that farmland, town, grass, bush and forest. The descending order of dissolved N RLs were shown as farmland, grass, bush, forest and town.