坡度对紫色土坡耕地产流产沙特征的影响

Effects of slope on the runoff and sediment yield in purple soil sloping farmland of Chongqing

为了研究坡度对紫色土坡耕地产流产沙特征的影响,基于2014-2017年5个不同坡度径流小区的典型次降雨条件下产流产沙数据,结合降雨、种植制度、田间管理和作物覆盖度变化,分析紫色土坡耕地的产流产沙变化特征。研究表明:1)坡耕地径流深与坡度总体呈正相关关系,径流深增加幅度随坡度增大逐渐减缓,当坡度从5°增大到10°时,径流深增幅在66.56%~1327.27%之间,从10°增加到20°则径流深增幅在2.55%~300.00%之间,最大产流坡度主要为20°,最小产流坡度主要为5°;2)产沙量随坡度增大总体呈增加趋势,当超过20°后,产沙量开始减小;最大产沙量坡度为20°,最小产沙量坡度为5°,这主要因为坡度超过20°后,坡度增大同时导致雨滴击溅侵蚀力减弱,产沙量随坡度的增大而减少;3)采用合理的种植制度可提高坡耕地作物覆盖度、增强农作物根系固土能力,通过加强对降雨截留、减缓径流和提高入渗等多种途径有效降低坡耕地径流量和产沙量。

[Background]Purple soil is one of the main types of sloping farmland in the Three Gorges Reservoir area,which causes a lot of soil erosion under the action of rainfall and runoff all the year round,posing ecological threats to the safety of the reservoir area.In order to study the effect of slope on the characteristics of sand yielding in purple soil sloping farmland,and to further clarify the characteristics of sand yielding in purple soil sloping farmland under different slopes,the process of sediment yielding in purple soil sloping farmland under rainfall conditions was studied.[Methods]Based on the typical sub-rainfall and sediment production data of 5 runoff plots with different slopes(5°,10°,15°,20°and 25°)in Tangfang Slope Runoff Observation Field,Wanzhou district,Chongqing from 2014 to 2017,combined with changes in rainfall,cropping system,field management and crop coverage,the characteristics of runoff and sediment yield in purple soil sloping farmland under different slopes were analyzed.[Results]1)The runoff depth of sloping farmland has a positive correlation with the slope as a whole.The increase of the runoff depth gradually slows down with the increase of the slope.When the slope increases from 5°to 10°,the runoff depth increases between 66.56%and 1327.27%,and increases from 10°.When it reaches 20°,the runoff depth increases between 2.55%and 300.00%,the maximum runoff gradient is mainly 20°,and the minimum runoff gradient is mainly 5°.2)The sediment yield generally increases with the increase of the slope.When the slope exceeds 20°,the sediment yield begins to decrease;the maximum sediment yield slope is 20°,and the minimum sediment yield slope is 5°,the increase of the slope also leads to the weakening of the erosive force of raindrop splashing,and the sand production decreases with the increase of the slope.3)The adoption of a reasonable planting system improved the crop coverage of sloping farmland,enhanced the soil fixation capacity of crop roots,and effectively reduced the runoff and sediment yield of sloping farmland by strengthening rainfall interception,slowing runoff and increasing infiltration.[Conclusions]Overall,the maximum 30-minute rainfall intensity and sub-rainfall in the slope and rainfall characteristics were the main factors affecting the sand yield of the purple soil sloping farmland.The research results can provide a reference for the evaluation of soil and water conservation effect of purple soil slope farmland and the layout of farming management measures,and provide a scientific basis for soil and water conservation in small watersheds.