Impact of non-point pollution of phosphorus on water quality: a case study of the middle and lower reaches of Hanjiang River

As one of the major source of river eutrophication,non-point source pollution has become a most important problem in watershed management.However,there are few researches about the impact of non-point source phosphorus load on the water quality.In the study,we take the middle and lower reaches of Hanjiang River as a case,basing on Landsat image,DEM,soil data,meteorological data,hydrological data,as well as socioeconomic data.SCS model and load export empirical equation are introduced into the study.Moreover according to the basin characteristics and pollutant migration as well as transformation rules,a one-dimensional water quality model is established,verified with measurements from monitoring sections.The results show that the phosphorus load of non-point source pollution is as high as 5381.30 t/a in 2007,contributed about 60% to the water pollution,among which the non-point source pollution from agriculture and city plays a most significant part and becomes the main type in the study region.