[Spatial-temporal Distribution of Suspended Solids and Its Sedimentation Flux and Nutrients Effects in Xin'anjiang...

To analyze the spatial-temporal distribution and sedimentation characteristics of suspended solids in reservoirs, high-frequency monitoring of a sediment trap and buoy, combined with three-dimensional water sampling, was conducted and analyzed in Xin'anjiang Reservoir for a year. The results showed that the turbidity data of the buoy has significant correlation with rainfall, inflow, and suspended solids (SS), particularly for SS (P<0.01, R²=0.86). There is an obvious spatial difference in SS between spring and summer, when the rainfall season occurs (river area > transition area > lake area). However, there is little difference in SS concentration between autumn and winter. There is a spatial trend of river area > transition area > lake area (with rates of 27.82, 4.34, and 0.26 g·(m²·d)^-1, respectively), and a temporal trend of spring and summer > autumn and winter. The sedimentation flux of the whole lake is 2.57×10⁶ t·a^-1 combined with the investigation of the four-season SS at 60 points across the whole lake, and the settlement flux in spring and summer is higher than that in autumn and winter. The contents of particulate nitrogen (PN) in JK, XJS, and DB were 6812, 15886, and 21986 mg·kg^-1, and the particulate phosphorus (PP) contents were 2545, 3269, and 3077 mg·kg^-1, respectively. Statistical analysis shows that there is a good exponential relationship between moderate rainfall and turbidity growth rate in the river area of the reservoir (R²=0.81). Moreover, the continuous heavy rainfall affects turbidity in river area, but has little effect on the transition area. The concentration of SS has a good exponential decay with distance from the river to the dam (R²=0.84), especially in spring and summer. Research shows that the average annual deposition rate in Xin'anjiang Reservoir is 0.07%, lower than other large reservoirs in the country; however, there are certain risks in front of the dam because the nutrient sediments are high. The results suggest that reservoir managers should pay attention to water and soil conservation in the watershed to reduce the impact of rainfall on reservoir water quality. Meanwhile, the potential nutrient internal release risk in the downstream area before the dam should be considered.