Sediment Retention Effect of Reservoirs and Microscale Surface Depressions

Abstract

On watershed scale, the reservoir dam has a significant regulating effect on runoff and sediment. Once the runoff enters the reservoir area, the sediment will be gradually deposited because of the lower flow velocity of runoff and the blocking effect of the dam. On microscale, soil surface depressions also can intercept runoff and promote sedimentation distinctly. In order to comparative study whether there was a high degree of correlation or consistency between these two sediment retention mechanisms, the sediment retention effect of reservoirs on watershed scale and that of soil surface depressions on microscale were comparatively studied and analyzed from the following 5 aspects: water–sediment relationship, double cumulative curve of runoff and sediment, deposition rate, sediment trapping coefficient, and sediment reduction coefficient. The results showed that there was a high correlation of sediment retention effect between reservoirs and soil surface depressions, and their sediment trapping coefficients were 0.113 and 0.097, respectively. In addition, the sediment retention effect was only related to topographic relief, but not to scale. It was feasible to use the sediment retention effect on microscale to predict that of reservoirs on macroscale, and the prediction results were accurate. In addition, with the increase of reservoir size, the annual total amount of sediment deposition showed an increasing trend, while the deposition rate, the error between calculated sedimentation and the measured value, and the sediment reduction coefficient showed a decreasing trend.