Evaluating soil-water conserving performance of land management strategies for spoil tips on the Chinese Loess Plateau

Surface runoff decrease (SRD) and sediment concentration change (SCC) are accountable for sediment reduction by anti-erosion strategies. Using a design of horizontal stages, contour trenches, fish-scale pits, as well as their combinations, this study evaluated the two components for sediment reduction after the implementation of various land management strategies on steep spoil tips. The study highlighted the interactions between SRD and SCC in reducing sediment, and characterized the temporal variations of sediment-reducing capacity by SRD and SCC. Results showed that slope erosion was well controlled with control ratios of sediment yield ranging from 0.4 to 0.59, 0.2 to 0.22, for horizontal stage-and contour trench-based strategies, respectively. Sediment-reducing benefit by SRD accounted for 52%-77% of the total sediment reduction and highly determined the perfor-mance of SCC. Quadratic relationships between sediment-reducing capacity by SCC and that by SRD were observed. The function of SCC only operated when the sediment-reducing capacity by SRD reached a certain threshold. These thresholds varied greatly in the range of 0.75 kg m- 3-0.91 kg m(- 3) and 0.61 kg m(- 3) 3-0.66 kg m(- 3) for horizontal stage-and contour trench-based strategies, respectively. The upper limits for sediment -reducing capacity by SCC varied in the range of 0.32 kg m- 3-0.44 kg m(- 3) and 0.63 kg m- 3-0.76 kg m- 3 for horizontal stage-and contour trench-based strategies, respectively. An efficiency coefficient of 55% and an M -N ratio of 1:1 indicated that sediment-reducing benefits by SRD and SCC were effectively exerted by combining contour trenches and fish-scale pits. The findings emphasized that the application of land management strategies must be considered based on particular goals to restore spoil tips. In practice, if targeted to enhancing sediment -reducing efficiency, contour trenches and fish-scale pits should be primarily considered. However, if the aim is to decrease water consumed for sediment control, then horizontal stages should be principally considered.