【摘要】 为了研究三峡地区花岗岩林地优先流影响因子,在长江三峡地区曲溪小流域内选定的实验坡面下部,垂直开挖了一个长度为2.9 m、深度为2.60 m的土壤剖面。在降雨过程中观察优先流过程,分析降雨对优先流的影响。同时对该地区的土壤物理性质和土壤渗透特性进行了测定,分析其对优先流的影响。分析结果表明,影响长江三峡花岗岩区优先流产流的降雨量在26 mm(24 h降雨量)以上。长江三峡库区的降雨可分为递减降雨型、均匀降雨型、突发降雨型及峰值降雨型4种类型,不同降雨类型对应的优先流过程都表现出相应的降雨过程特征。不同降雨类型的优先流出现时间也各有差异,峰值降雨型降雨产生的优先流出现时间最早,其次是突发降雨型、递减降雨型、均匀降雨型。当一场降雨中的最大降雨强度>0.075 mm/m in时,就有可能产生优先流。非毛管孔隙比例较大的土壤中容易形成优先流。研究区林下土壤中粗颗粒含量呈现出由上层至下层逐渐增多的趋势。对于较深层次土壤来说,它们含有的较粗颗粒有利于优先流的形成。优先流的存在使距地表83~110 cm土层中土壤稳渗速率较其他土层得以大幅度提高,土层内快速运动的水流又加速了优先流的形成与发展。更多还原

【Abstract】 To study the affecting factors of preferential flow, a 2.9 m-length,2.6 m-depth soil profile was dug in Quxi watershed,Yangtze River.To analyze the influence of rainfall on preferential flow,the preferential flow process was observed when the rainfalls were recorded.And the soil physical and infiltration characteristics were measured to study their effect on preferential flow.The results showed that the rainfall amount that could cause preferential flow was more than 26 mm.The rainfall in the Three Gorges area can be divided into 4 types,namely gradually dropping raining,even raining,suddenly raining and peak raining.The preferential flow process was relevant to the raining process.With different rainfall types,the preferential flow appeared in different time,firstly in the peak raining,following in the suddenly raining,gradually dropping raining,and the even raining.The preferential flow would appear when the rainfall intensity was more than 0.075 mm/min.In the studied area,the coarse soil particles increased with the soil depth,and for the deeper soil layer,its coarse particles were benefit to form preferential flow.The preferential flow accelerates the saturated infiltration rate of the soil layer 83~110 cm,and the quickly moving water in this layer also enhanced further formation and development of preferential flow.更多还原