Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazar...Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.展开更多
Vegetative filter strip (VFS) is a main kind of Best Management Practices for the control of non-point source pollution. The goal of this paper is to evaluate the effectiveness of VFS in Chinese northwest regions. Thr...Vegetative filter strip (VFS) is a main kind of Best Management Practices for the control of non-point source pollution. The goal of this paper is to evaluate the effectiveness of VFS in Chinese northwest regions. Three VFSs with natural grass and Hippophae rhamnoides/grass patterns have been constructed in the bank slope of Xiaohuashan reservoir, Huaxian County, Shannxi Province. The removal effects of VFS and influencing factors have been analyzed based on field experiment data. The result reveals a positive effect on reducing the transportation of suspended solids, phosphorus and nitrogen in surface runoff, and it is more efficient on suspended solids removal. The experiment also shows that most of the suspended particles and pollutants bound to them were entrapped in the first 10 m of VFS. The main factors influencing effectiveness of VFS include vegetation patterns and inflow rate. In addition, inflow pollutant concentration has a larger impact on reducing total nitrogen and total phosphorus by VFS, but the reduction effect on SS has no significant difference.展开更多
文摘Purple soil is highly susceptible for overland flow and surface erosion, therefore understanding surface runoff and soil erosion processes in the purple soil region are important to mitigate flooding and erosion hazards. Slope angle is an important parameter that affects the magnitude of runoff and thus surface erosion in hilly landscapes or bare land area. However, the effect of slope on runoff generation remains unclear in many different soils including Chinese purple soil. The aim of this study was to investigate the relationship between different slope gradients and surface runoff for bare-fallow purple soil, using 5 m × 1.5 m experimental plots under natural rainfall conditions. Four experimental plots(10°, 16°, 20° and 26°) were established in theYanting Agro-ecological Experimental Station of Chinese Academy of Science in central Sichuan Basin. The plot was equipped with water storage tank to monitor water level change. Field monitoring from July 1 to October 31, 2012 observed 42 rainfall events which produced surface runoff from the experimental plots. These water level changes were converted to runoff. The representative eight rainfall events were selected for further analysis, the relationship between slope and runoff coefficient were determined using ANOVA, F-test, and z-score analysis. The results indicated a strong correlation between rainfall and runoff in cumulative amount basis. The mean value of the measured runoff coefficient for four experimental plots was around 0.1. However, no statistically significant relationship was found between slope and runoff coefficient. We reviewed the relationship between slope and runoff in many previous studiesand calculated z-score to compare with our experimental results. The results of z-score analysis indicated that both positive and negative effects of slope on runoff coefficient were obtained, however a moderate gradient(16°-20° in this study) could be a threshold of runoff generation for many different soils including the Chinese purple soil.
文摘Vegetative filter strip (VFS) is a main kind of Best Management Practices for the control of non-point source pollution. The goal of this paper is to evaluate the effectiveness of VFS in Chinese northwest regions. Three VFSs with natural grass and Hippophae rhamnoides/grass patterns have been constructed in the bank slope of Xiaohuashan reservoir, Huaxian County, Shannxi Province. The removal effects of VFS and influencing factors have been analyzed based on field experiment data. The result reveals a positive effect on reducing the transportation of suspended solids, phosphorus and nitrogen in surface runoff, and it is more efficient on suspended solids removal. The experiment also shows that most of the suspended particles and pollutants bound to them were entrapped in the first 10 m of VFS. The main factors influencing effectiveness of VFS include vegetation patterns and inflow rate. In addition, inflow pollutant concentration has a larger impact on reducing total nitrogen and total phosphorus by VFS, but the reduction effect on SS has no significant difference.
