摘要:
文章通过人工模拟降雨试验,研究不同地下孔(裂)隙度、基岩裸露率和雨强对地表、地下产流、产沙的影响,其结果表明:(1)土壤侵蚀与地下孔(裂)隙度具有较高相关性,地表产流、产沙随地下孔(裂)隙度的增大而减小,而地下则相反;(2)坡面径流刚产生时,雨滴击溅和薄层水流冲刷,土壤细小颗粒堵塞其毛管空隙,渗漏率减小,而地表径流量增大,土壤团聚体被破坏、分散和迁移,降水与土壤渗漏率增大,地表径流量减小,雨滴击溅增强,如此循环,降水与土壤渗漏率呈波动性变化;总体而言,地表、地下悬移质均随降雨历时呈下降趋势,而地表推移质则相反,地表、地下产流量变幅较小,趋于平行;(3)地表产流、产沙量随基岩裸露率增大呈波动性变化,总体呈下降趋势;而地下产流、产沙量随基岩裸露率增大呈波动性变化,总体呈增大趋势;(4)在较小雨强30 mm/h 时,地表只产生悬移质流失,没有产生推移质流失;地表、地下产流、产沙都是随雨强增大而增大;雨强由30 mm/h 增大到150 mm/h,地表累积产流量为538.5 L,累积产沙量为2393.81 g,地下累积产流量为207.8 L,累积产沙量为687.73 g,累积产沙量的递增速率比累积产流量的递增速率要大,地表产流、产沙的递增速率大于地下产流、产沙的递增速率;(5)各因子与土壤侵蚀间相关程度为:降雨历时>雨强>地下孔(裂)隙度>基岩裸露率。该实验有助于为喀斯特地区的水土流失研究、评价及制订石漠化治理措施提供理论依据。
Abstract:
Karst is widely distributed in China where carbonate rocks,including buried karst,account for up to 3,463,000 km2 .Strata with carbonate rock formations comprise 2,060,000 km2 ,while carbonate rocks outcrop over 907,000 km2 .The karst system,which is faces serious soil erosion problems,is an ecologically fragile system due to its high sensitivity,low catastrophe capacity and small environmental capacity.There-fore,study of soil erosion in karst areas is important.The impacts of fissure porosity,bedrock outcrop per-centage and rainfall intensity on underground runoff and sediment yield were evaluated using simulated rain-fall.The results provide a theoretical basis for future evaluation and prevention of soil erosion in karst areas. The results showed,(1)Soil erosion has a high correlation with porosity or fracture aperture;(2)Soil infil-tration rate is dependent on rainfall.Surface and subsurface suspended sediment decrease with rainfall dura-tion,while surface bed material load increases;(3)In general,the amount of surface runoff and sediment decreases with the bedrock outcrop rate,while the amount of underground runoff and sediment increases;(4)Only suspended sediment loss took place on the surface.No bed material load loss occurred with rainfall intensity of 30 mm/h.The runoff and sediment yield increase with rainfall intensity.For instance,when rain intensity increased from 30 mm/h to 150 mm/h,the cumulative surface runoff was 538.5 L,cumulative sur-face sediment yield 2,393.81 g,cumulative underground runoff 207.8 L and cumulative underground sedi-ment yield 687.83 g.The rate of increase in the cumulative sediment yield is greater than the rate of increase in the cumulative runoff,and the rate of increase in the surface runoff and sediment yield is greater than that of the underground runoff and sediment yield;(5)The correlation between soil erosion and each individual factor indicates that the relative impact of each factor on soil erosion is,rainfall duration > rainfall intensity> underground porosity > bedrock outcrop.
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