Spatial-temporal Features of Nitrogen and Phosphorus Losses of Jingui River Watershed in the upstream of Lijiang River

To find out the nitrogen and phosphorus concentration and load emission regularity and its effect during the rainy season + irrigation period and dry season + non-irrigation period in the small watershed, five spatial scales (3.35 ∼27.25 km²) nested in the Jingui river watershed are selected and regularly monitored from October 2017 to September 2018. The results showed that the nitrogen and phosphorus concentrations in the rainy season + irrigation period and dry season + non-irrigation period increased with the increase of the scale. The total nitrogen and total phosphorus load per unit area in the rainy season + irrigation period decreased with the increase of the scale; the dry season + non-irrigation period increased slightly. The same nitrogen and phosphorus index concentration was significantly different at different spatial scales. The main reason for the scale effect was the distribution pattern of land-use. Affected by this, scale D, the critical scale of nitrogen and phosphorus load in Jingui river watershed, its average load of total nitrogen, ammonium nitrogen, total phosphorus and total dissolved phosphate reached the highest value of the watershed. The contribution rate of nitrogen and phosphorus load in rainy season + irrigation period and dry season + non-irrigation period of research areas with different area depends on precipitation and the distribution pattern of land-use. Therefore, the nitrogen and phosphorus emission control and pollutant reduction in the rice irrigation districts of Lijiang river basin should consider the spatial-temporal features and effects of nitrogen and phosphorus pollutant transport. (paper)