Key Laboratory of the Soil and Water Conservation on the Loess Plateau of Ministry of Water Resources, Yellow River Institute of Hydraulic Research, Yellow River Conservancy Commission, No. 45, Shunhe Road, Zhengzhou 450003, China.
Henan Key Laboratory of Yellow Basin Ecological Protection and Restoration, No. 45, Shunhe Road, Zhengzhou 450003, China.
Int J Environ Res Public Health. 2022 Jul 26;19(15):9089. doi: 10.3390/ijerph19159089.
The flow-sediment relationship is important to understand soil erosion and sediment transport in severely eroded areas, such as Loess Plateau. Previous research focused on the variation and driving forces of runoff and sediment at the different scales in a watershed. However, the variations of the flow-sediment relationship on multispatial scales (slope, subgully, gully, and watershed scales) and multitemporal scales (annual, flood events, and flood process) were less focused. Taking the Peijiamao watershed, which includes whole slope runoff plot (0.25 ha, slope scale), branch gully (6.9 ha, subgully scale), gully (45 ha, gully scale), and watershed (3930 ha, watershed scale), four different geomorphic units located at the Chinese Loess Plateau, as the research site, a total of 31 flood events from 1986 to 2008 were investigated, and two flood process data were recorded across all the four geomorphic units. The results showed that on the annual timescale, the average sediment transport modulus and runoff depth at four scales exhibited a linear relationship, with determination coefficients of 0.81, 0.72, 0.74, and 0.77, respectively. At the flood event timescale, the relationships between sediment transport modulus and runoff depth at the gully and watershed scales could also be fitted with a linear relationship with high determination coefficients (from 0.77 to 0.99), but the determination coefficient at the slope scale was only 0.37 at the event scale. On the single rainfall event timescale, the flow-sediment relationship at the slope scale showed a figure-eight hysteretic pattern while those relationships at larger scales showed an anticlockwise loop hysteretic pattern. Under the same flow condition, the suspended sediment concentrations during the falling stage were significantly higher than those during the rising stage. Moreover, the difference was bigger as the spatial scale increased due to the wash loads in the downstream gullies, which favored the occurrence of hyper-concentration flow. The results of the study could provide useful insights into the temporal-spatial scale effects of sediment transport and their internal driving mechanisms at the watershed scale.
坡面、支沟、干沟和流域多时空尺度的水流-输沙关系变化及其内在驱动机制
在水土流失严重的地区，如黄土高原，水流-输沙关系对于理解土壤侵蚀和泥沙输移非常重要。以往的研究主要集中在流域不同尺度上的径流量和输沙量的变化及其驱动力。然而，多时空尺度（坡面、支沟、干沟和流域尺度）和多时间尺度（年际、洪水事件和洪水过程）的水流-输沙关系变化却较少受到关注。本研究以包含整个坡面径流小区（0.25 公顷，坡面尺度）、支沟（6.9 公顷，支沟尺度）、干沟（45 公顷，干沟尺度）和流域（3930 公顷，流域尺度）的砒砂岩小流域为研究区，共调查了 1986 年至 2008 年的 31 次洪水事件，并在所有四个地貌单元上记录了两次洪水过程数据。结果表明，在年际时间尺度上，四个尺度的平均输沙模数和径流水深呈线性关系，决定系数分别为 0.81、0.72、0.74 和 0.77。在洪水事件时间尺度上，干沟和流域尺度的输沙模数与径流水深之间的关系也可以用线性关系拟合，决定系数较高（从 0.77 到 0.99），但在事件尺度上，坡面尺度的决定系数仅为 0.37。在单次降雨事件时间尺度上，坡面尺度的水流-输沙关系呈“8”字形滞后模式，而较大尺度的关系呈逆时针环滞后模式。在相同的水流条件下，下降阶段的悬移质浓度明显高于上升阶段。此外，由于下游沟道的冲刷负荷，随着空间尺度的增大，差异也越大，这有利于超浓水流的发生。本研究结果可为流域尺度输沙的时空尺度效应及其内在驱动机制提供有益的见解。
