雨滴打击与壤中流交互作用对横坡垄作坡面侵蚀过程的影响

Interactive Influence of Raindrop Impact and Seepage on Soil Erosion Process Within Contour Ridge System

横坡垄作是被广泛采用的保护性耕作措施之一。垄沟低洼处的积水可诱发壤中流,并可造成雨滴打击对土壤颗粒分离/搬运的增强与减弱作用并存。因此,横坡垄作坡面雨滴打击与壤中流交互作用对土壤侵蚀过程的影响有别于传统坡面。基于人工模拟降雨试验,对有/无雨滴打击作用(RI,WRI)自由入渗(FD)和壤中流(SP)2种试验处理下的产流、产沙过程进行了探究。结果表明:(1)径流量表现为SP+WRI>SP+RI>FD+RI>FD+WRI。雨滴打击作用和壤中流对径流的贡献分别为-47.09%~54.37%和41.96%~85.62%。(2)侵蚀量表现为SP+RI>SP+WRI>FD+RI>FD+WRI。雨滴打击作用和壤中流对侵蚀量的贡献分别为12.92%~94.94%和25.83%~97.28%。(3)自由入渗试验处理下,雨滴打击作用对产流过程影响不明显;土壤饱和后,雨滴打击作用和壤中流的存在均使产流、产沙过程波动幅度更大。(4)有/无雨滴打击作用,自由入渗试验处理下的侵蚀量与产流率符合幂函数关系,而壤中流试验处理下二者符合指数关系。研究结果有助于加深对横坡垄作坡面土壤侵蚀过程的认识,为横坡垄作坡面水土流失综合治理提供理论支撑。

Contour ridge system is an effectively agricultural practice used throughout the world.Due to microtopography,rainwater from side slopes flows into furrows and ponds in lower areas of furrows,and thus induces seepage to occur more readily.In addition,the ponding results in that raindrop impact enhances or weakens the capacity of soil detachment and transport.Therefore,the interactive influence of raindrop impact and seepage on soil erosion process is more complicated relative to traditional slope systems.Runoff and sediment yielding process were analyzed under two soil surface hydrological conditions(free drainage,FD and seepage,SP)and two soil surface conditions(with and without raindrop impact,RI and WRI)through simulated rainfalls.Results showed that:(1)Runoff ranked in the order of SP+WRI>SP+RI>FD+RI>FD+WRI.Raindrop impact and seepage contributed-47.09%~54.37%and 41.96%~85.62%to the runoff,respectively.(2)Soil loss decreased in the sequence of SP+RI,SP+WRI,FD+RI,and FD+WRI.Raindrop impact and seepage made contributions of 12.92%~94.94%and 25.83%~97.28%to soil loss,respectively.(3)Raindrop impact showed a slightly influence on runoff process under FD condition.However,raindrop impact and seepage induced the temporal variation of runoff rate and sediment concentration more fluctuated when soil was saturated.(4)With or without raindrop impact,a power function relation was found between runoff rate and soil loss under FD condition,while exponential function could describe their relation under SP condition.These findings were helpful to understand soil erosion process within contour ridge systems,and supply guidance for soil and water comprehensive conservation for implementing contour ridge systems.