紫色土区小流域泥沙输出过程对雨型和空间尺度的响应

Response of sediment flow behavior to storm type and spatial scale in purple soil watershed

以紫色土区3个具有不同集水面积、物理特征和土地利用方式的小流域为研究对象，在1999～2000年间对流域野外自然降雨下泥沙输出过程进行了监测，旨在从小流域尺度阐明径流含沙量过程特征及其空间约束效应。结果表明：天然降雨侵蚀过程中流域径流含沙量时间曲线表现为波浪起伏形、幂函数递减形和抛物线复合形3种类型；峰值径流流量后，含沙量降低，表现为变化幅度小的低含沙量特征。泥沙输出过程对流域空间尺度的响应受降雨型式的强烈影响。均匀型降雨侵蚀下，径流含沙量时间曲线表现为低含沙量的波浪起伏形，并且，随流域面积的增加，次降雨平均含沙量增加；间歇型降雨侵蚀下，随流域面积的增加，径流含沙量曲线从抛物线复合形向幂函数递减形过渡；中大型降雨侵蚀下，径流含沙量时间曲线表现为幂函数递减形，泥沙输出过程对流域空间尺度的响应不敏感。

The sediment output processes for natural rainfall events monitored in three purple soil small watersheds with different catchment areas, physical characteristics and types of land are used to investigate the sediment behaviors and their spatial dependence. The results show that the variation process of sediment concentration exhibits in three types： waveform, power-decreasing and parabolacompounded. After the peak runoff rate, sediment concentration decreases and variation amplitude reduces. The sediment flow output is significantly affected by the spatial scale and type of storm. The erosion of even-distributed type rainfall results in waveform hydrograph of sediment flow with low concentration and increases with the area of watershed. Whereas, following the increase of watershed area, under the action of intermittent-type rainfall the sediment hydrograph transits from parabolacompounded type into power-decreasing type. The sediment hydrograph under the erosion of mid and deluge rainfall exhibits power-decreasing type and no significant spatial dependence is found.