黄土丘陵沟壑区不同时空尺度下产沙模数的变化

Sediment Yield of a Loess Hill Area at Different Temporal and Spatial Scales

本文在陕北岔巴沟流域,依据不同的时间尺度,挑选了1964年及1966年中能覆盖整个岔巴沟流域的9场降雨(次降雨尺度),包括着9次降雨的6个月份(月尺度)以及1964、1965、1966和1967连续4年(年尺度)的侵蚀产沙数据。分别在峁坡、全坡面、毛沟、支沟、干沟等不同空间尺度下,考虑次暴雨、月、年等不同时间尺度的侵蚀产沙情况。分析结果表明:坡面尺度与支沟、干沟尺度的侵蚀产沙方式有所不同,后者年际产沙模数变幅比较小(年际间产沙模数差异系数为0.42);在同一时间尺度下,产沙模数的大小,由时间不同造成的差异大于由空间不同造成的差异。在小的时间尺度,产沙模数大小变化比较随机;在大的时间尺度,产沙模数呈现一定尺度效应。相同面积区域不同时间的产沙模数差异系数分别为:不同次暴雨之间最大(1.05),不同月份之间次之(0.835),而不同年份之间最小(0.76)。本文将侵蚀产沙的能量分为质与量两个方面,分别讨论了坡面尺度与流域尺度能量变化与侵蚀产沙的关系。

Hydrological data including precipitation, runoff, and sediment Chabagou catchment in northern Shaanxi province for different time scale from 9 single rainfall events, a 6-month period, and a 4-year period sediment yield were also analyzed at several spatial scales ranging from yield were collected from the Data included measurements 1964- 1967）. Erosion and llslope to watershed. Results showed that the process of erosion and sediment yield at a hillslope scale was different from the channel or gully scale, which had a smaller range of variation in annual erosion and sediment yield. For a single time scale, variation in sediment yield among different periods was greater than the variation among different spatial scales. The sediment yield was highly variable at small temporal scales, so changes in temporal scale had more influence on the measurement of sediment yield than changes in spatial scale. For longer time scales, the use of more data points had a smoothing effect on trends. At an annual time scale, sediment yield measurements first increased and then decreased with increasing spatial scale. Erosion processes differed based on spatial scale. Sediment yield from interrills was mainly produced during single rainfall events. Mass movement and gully erosion were very serious in channels, which was apparent during low-flow periods. The variance coefficients of sediment yield measurements collected from different time scales at the same spatial scale varied significantly： the most considerable difference was between single rainfall events （1.05）, while the variance coefficient at a scale of months was more modest （0.835） and for different years was minimal （0.76）. The energy of erosion and sediment yield was discussed in terms of quantity and quality to describe the relationship of changes in energy and sediment yield at the hillslope and watershed scales.