垄沟集雨种植系统水分入渗特性模拟研究

Soil water infiltration characteristics of ridge-furrow water harvesting systems

【目的】探讨不同带型垄沟集雨种植系统水分入渗特性,为农田垄沟集雨种植的垄沟带型优化设计提供依据。【方法】采用土槽和人工降雨模拟试验,在相同的初始含水率(10%)和降雨条件(降雨强度为16mm/h,降雨量24mm,试验历时81min)下,在土槽内分别设计宽带型垄沟(垄宽和沟宽均为60cm)和窄带型垄沟(垄宽和沟宽均为45cm),2种垄沟均为1∶1带型,垄高15cm,借助数码相机记录垄沟断面土壤湿润锋动态,利用时域反射仪(TDR)测定沟中心、垄沟交界、垄腰、垄顶及垄中心0~5,5~10,10~15,15~20,20~25和25~30cm土层土壤含水率,研究垄沟集雨种植系统土壤水分入渗过程。【结果】2种带型垄沟土壤水分入渗所呈现的湿润锋具有相似的空间分布规律,在垄沟交界处土壤浸润锋水平和垂向推进速度大于其他部位,半垄沟集雨系统横截面大致呈现为垄沟交界水分富集区、沟内水分过渡区和沟中心水分次富集区3个相连接的部分。尽管2种带型垄沟湿润锋在垄沟交界处均呈现出垂直入渗和横向侧渗增大的现象,但窄带型垄沟湿润峰距垄沟交界处最大侧渗距离(6.14cm)比宽带型垄沟(7.28cm)仅降低了1.14cm。在垄沟交界处,窄带型垄沟浸润峰面积占整个湿润锋面积的比例(64%)大于宽带型垄沟(47.3%),窄带型有利于水分蓄积保墒。在0~30cm土层,同一深度垄沟交界处土壤含水率最高,其次是沟中心、垄腰,垄顶、垄中心土壤含水率与初始含水率差异不大。在相同的初始含水率和降雨事件下,2种带型垄沟湿润锋运移累计面积及变化速度存在明显差异。人工降雨后0~72h,集雨沟不同观测部位2种带型垄沟土壤含水率之差的变化规律有明显差异。【结论】2种带型垄沟集雨种植系统中,土壤水分在垄沟交界处存在富集区域,适当降低垄沟带型宽度可以减少土壤水分渗漏和蒸发损失。

【Objective】The characteristics of soil water infiltration of ridge-furrow water harvesting systems were investigated to provide basis for the optimal design.【Method】The experiment used artificial simulation of rainfall in soil bin to measure the wetted areas by digital camera in real time,and collected soil moisture content data through TDR.Under the same initial moisture content（10%）and rainfall conditions（rainfall intensity 16 mm/h,rainfall 24 mm and duration 81 min）and with same ridge height of 15 cm,a wide system（ridge width and furrow width are all 60 cm）and a narrow system（ridge width and furrow width are all 45 cm）were set up to measure soil moisture contents at furrow center,ridge and furrow junction,ridge middle,ridge top and ridge center,and the soil layers of 0-5,5-10,10-15,15-20,20-25 and25-30 cm.【Result】The wetting front of the 2 ridge and furrow systems had similar spatial distribution that the migration distances of wetting front on both lateral and vertical directions at the ridge-furrow junction were greater than at other parts.The cross section of semi-ridge furrow system had 3 connected parts of the junction water enrichment area,transition zone and the furrow center water enrichment area.Though the wetting front of the 2 systems showed greater values than other parts at the junction,the maximum lateral osmotic distance（6.14 cm）of the narrow ridge-furrow system from the wetted peak of junction was only 1.14 cm lower than that of the wide system（7.28 cm）.The ratio of infiltration area to the whole wet front area at junction of the narrow ridge and furrow system was 64%,which was larger than that of the wide system（47.3%）.Thus,the narrow ridge and furrow system was favorable for water storage and moisture conservation.In the soil layer of 0-30 cm,the soil moisture content was highest at the junction,followed by the furrow center and ridge middle.Within 0-72 hafter artificial rainfall,with same initial water content and rainfall events,there were significant differences in wetting front cumulative area and changing speed among the systems.【Conclusion】The soil water in ridge-furrow water harvesting systems is mainly concentrated on the ridge-furrow junction,and it is suggested to reduce the width of ridge-furrow for less soil water seepage and surface evaporation.