Key Laboratory of Water Cycle and Related Land Surface Processes, Institute of Geographic Sciences & Natural Resources Research, Chinese Academic of Sciences, Beijing 100101, China.
Sci Total Environ. 2018 Jul 15;630:1453-1463. doi: 10.1016/j.scitotenv.2018.02.323. Epub 2018 Mar 7.
Sediment rating curves have long been used as a tool for predicting sediment yield. In this study, the spatial and temporal variations of rating curves were examined in the loess area (~15,000km) of the Wuding River basin of the Chinese Loess Plateau. Data of mean daily water discharge per unit area, Q (mskm), and mean daily sediment discharge per unit area, SD (kgskm), were compiled for three periods of 1959-1971, 1972-1989, and 2006-2013. Soil conservation measures were rarely implemented for the pre-1971 period but were intensively implemented for the latter periods. The proportional function, i.e. SD=CQ, fitted the rating curve well for all periods. The coefficient, C, is an approximation of the mean sediment concentration of surface runoff (MSC). Contrary to the usual belief, C was ca. 730kgm whatever the location for the pre-1971 period; examinations at the instantaneous and the event time scales further demonstrated the spatial invariant MSC across six orders of magnitude in drainage area sizes (from 0.006 up to 3893km). The spatial invariant MSC forms as a result of the ready availability of mass-wasted materials in headwaters and holds on as a result of the minimal in-stream erosion and sedimentation along the stream channel. For the post-1971 periods, both C and its spatial invariability decreased in a non-monotonous way, which was related to the check-dam (i.e., sediment trapping dams) constructions but not to the implementation of revegetation and terracing measures. As a result, the non-monotonous temporal trends of C and its spatial coefficient of variation both captured the intermittency of the check-dam construction well. Temporal changes in MSC or the sediment rating curve, which is less disturbed by rainfall, provides important insights into anthropogenic impacts on river systems.
泥沙输移率曲线长期以来一直被用作预测泥沙产量的工具。本研究以中国黄土高原的无定河流域的黄土区（约 15000km）为例，探讨了泥沙输移率曲线的时空变化。本研究收集了三个时间段（1959-1971 年、1972-1989 年和 2006-2013 年）的单位面积日均径流量（Q（mskm））和单位面积日均输沙量（SD（kgskm））数据。1971 年之前很少实施水土保持措施，但在后来的两个时期，水土保持措施得到了广泛的实施。比例函数，即 SD=CQ，很好地拟合了所有时期的泥沙输移率曲线。系数 C 是地表径流平均含沙量（MSC）的近似值。与通常的看法相反，无论在 1971 年之前的时期，C 的值约为 730kgm；在瞬时和事件时间尺度上的检验进一步证明了在流域面积（从 0.006 到 3893km）六个数量级的空间不变 MSC。空间不变 MSC 的形成是由于流域上游有大量易被侵蚀的物质，而且由于沿河道的侵蚀和泥沙沉积最小，因此得以保持。对于 1971 年以后的时期，C 及其空间不变性呈非单调递减趋势，这与淤地坝（即泥沙拦截坝）的建设有关，但与植被恢复和梯田措施的实施无关。因此，C 及其空间变异系数的非单调时间趋势都很好地捕捉到了淤地坝建设的间歇性。受降雨干扰较小的泥沙输移率曲线的时间变化，为研究人类活动对河流系统的影响提供了重要的见解。
