Abstract:Based on routine monitoring data in Xiangxi River and its main tributary Gaolan River from September 2000 to June 2005, this paper estimates the contribution of riverine nutrients, and analyzes the monthly dynamics of concentrations and fluxes of nutrients. The results show that Xiangxi Bay annually receives 1623.49 tons of total nitrogen and 331.85 tons of total phosphorus; Xiangxi River alone accounts for 68.50% of the total nitrogen fluxes and 91.74% of the total phosphorus fluxes. In these two rivers, dissolved inorganic nitrogen (DIN) is the dominating form; fluxes of DIN and TN are high during the summer (July), medial in spring and autumn, and relatively low in winter; non-point source pollutants that flow into rivers are the most important pathway of nitrogen. Phosphate is the dominating form in Xiangxi River, relatively low in Gaolan River; fluxes of phosphorus are high during the late spring and summer, relatively low during the late autumn and winter periods in Gaolan River, but fluctuates irregularly in Xiangxi River; phosphorus in Gaolan River has been caused by non-point source pollutants, while point source pollutants of phosphorus play an important role in Xiangxi River. Soil erosion probably represents the major pollutants of non-point source，while the drainages of phosphorus diggings and factory discharges play the most important role in the point source of phosphorus. This research suggests that measures must be taken to control the point source pollutants of phosphorus in Xiangxi River in order to protect Xiangxi Bay of the Three-Gorge Reservoir.