Effect of soil conservation engineering practice on the soil erosion in the upper reach of Guanting Reservoir

摘要

The engineering practice is one of main measures which control soil and water loss. In this study, 28 runoff event data from natural rainfall (2002～2004) and simulated rainfall data were used to study the effect of engineering practice (fish-scale pit, narrow terrace and tree tray) on the reduction in sediment and on supporting practice factor P. The results showed that average soil loss from fallow land was 11, 13 and 25 times that from narrow terrace, fish pit and tree tray land under the natural condition. The soil loss from fallow land was 5, 4 and 9 times that from narrow terrace, fish pit and tree tray land under the heavy storm condition. Reduction in sediment of fish-scale pit, narrow terrace and tree tray were 92%, 91% and 96% under natural condition, and 74%, 79% and 89% under simulated rainfall (heavy rainstorm). Reduction in sediment increased with rainfall amount at first and then decreased and tended to keep constant. Soil conservation engineering practices can effectively reduce sediment even if the spillover and damage of their ridges occurred. Supporting practice factor P decreased with rainfall amount firstly and then tended to increase. The power relationship between supporting practice factor P and rainfall amount R were found when rainfall amount was greater than 20 mm. The results can be used to determine the reduction in sediment yield and supporting practice factor of the three engineering practices for different rainfall occurrences.