Abstract:
Abstract: In this paper, sediment delivery ratio was spatially rasterized, and the model of sediment delivery ratio was constructed by the motivation cofficient and the resistance cofficient. Among them, the motivation cofficient was expressed by topographic index which reflected hydrological process, and the resistance cofficient was expressed by the vegetation interception resistance. Finally, the exsting soil erosion model, sediment load model and absorbed nitrogen and phosphorus load model were used to estimated the pollution load of absorbed nitrogen and phosphorus in the Three Gorges Reservoir area from 1990 to 2010. The results showed that the motivation coefficient affacting sediment delivery was primarily on median range from 0.4 to 0.8 in the Three Gorges Reservoir area. Moreover, its spatial heterogeneity was not significant (p > 0.05?). However, the performance of resistance coefficient was more complicated. The parallel ridge and valley zone, river alluvial gentle slope zone and mesa zone had high resistance coefficient, due to low gradience of slopes, while the northern zone of Qinba Mountain area, and the Alpine and Valley zone of Wuling Mountain area possessed low resistance coefficient due to steeper slopes. The results also showed that the sediment delivery ratio was in approximately normal distribution in the Three Gorges Reservoir area with a single peak. Its mean value was 0.48. It exhibited significant spatial heterogeneity. The ratio of sediment delivery in the middle and western parallel ridge and valley zone was much smaller than the Qinba Mountain and Wuling Mountain areas. At the same time, it had the tendancy of the gradient increase from the center of the river to the sides. Moreover, the change trend of mean sediment load was the same as the interannual variation of total sediment load in the Three Gorges Reservoir area. Simulation of the total sediment load (0.9 t) and the value of monitoring from bulletin (0.92 t) was the most close in 1995. At the spatial patterns, the spatial distribution of the low value zone and high value zone of sediment load were relatively stable due to little change in mean sediment load during 1990-2010. The distribution ranges of the low value zone was very wide with a high concentration degree. The distribution of high value area was very discrete and broken. In addition, absorbed nitrogen and phosphorus load possessed on value year-on-year growth with soil erosion modulus and sediment load in the Three Gorges Reservoir area. The maximum values of the total load in 2010 reached 1.2 tons and 0.6 tons respectively for nitrogen and phosphorus. Overall, they had similar spatial distribution with an unbalanced characteristics. Absorbed nitrogen and phosphorus load presented gradually decreasing tendency from east to west. The simulation result of adsorbed of nitrogen load was better than adsorbed phosphorus load when their correlation analysis was made with monitoring data. Absorbed nitrogen and phosphorus load had spatial correlation within in the Three Gorges Reservoir area.