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汇总了西南喀斯特地区坡地土壤和洼地、塘库沉积泥沙的~(137)Cs比活度资料,并进行了对比,分析流域泥沙来源。坡地地面流失轻微的,汇水面积小于0.5 km~2的微小流域,流域产沙主要源于地下流失(裂隙土)和沟岸侵蚀(沟壁土);坡地地面流失强烈的,主要源于坡地地面流失(坡地表层土壤)。地下流失和沟岸侵蚀是小流域和较大流域的主要产沙方式,且有随着流域面积增大,产沙贡献率越高的趋势。由于裂隙土和沟壁土都基本不含~(137)Cs,~(137)Cs单一示踪法不能区分这两种源地土体的产沙贡献率。建议采用多元示踪法,研究流域的泥沙来源。区分裂隙土和沟壁土的产沙贡献率,可考虑尝试磁性法和孢粉法。通过沉积物~(137)Cs断代等方法确定洼地、河流滩地和塘库泥沙淤积量,结合径流小区和水文站输沙量资料,分析不同类型洼地、河流滩地和塘库的泥沙截留率,分析河流泥沙输移比。在查明泥沙来源,泥沙输移比和输沙量(或产沙量)的基础上,确定流域泥沙平衡,结合径流研究成果,建立喀斯特流域产沙模型。
The ~ (137) Cs specific activity data of sediment in the sloping fields and depressions and ponds in the southwest karst region are summarized and compared to analyze the sediment source of the watershed. Slightly low groundwater loss on sloping lands led to small watersheds with catchment areas of less than 0.5 km ~ 2. The sediment yield in the watershed was mainly due to underground drainage (fissure soil) and ditches erosion (ditch-wall soil). The land loss on sloping land was mainly due to slope land Loss (slope surface soil). The underground runoff and erosion at the riparian bank are the main sand production ways in the small watershed and the larger watershed. As the area of the catchment increases, the contribution rate of sand production tends to be higher. Because both fissure soil and furrow soil are basically free of ~ (137) Cs, ~ (137) Cs single tracing method can not distinguish the contribution of soil yield from the two sources. Multiple tracing methods are recommended to study sediment sources in the basin. To distinguish between the contribution of furrow and furrow soil to sediment yield, consider the magnetic method and sporopollen method. Sediment deposition in depression, river beach and ponds was determined by means of sediment ~ (137) Cs dating, sediment retention of different types of depressions, river beaches and ponds were analyzed based on sediment discharge data from runoff plots and hydrological stations , Analysis of river sediment transport ratio. On the basis of ascertaining sediment source, sediment transport ratio and sediment discharge (or sediment yield), the sediment balance in the watershed is determined. Based on the results of runoff studies, a model of sediment yield in the karst basin is established.