黄土高原区不同地貌类型下入渗水深度研究——以南小河沟为例

The Effect of Geomorphology on Infiltration Depth in the Loess Plateau——A Case of Nanxiaohegou

选取位于黄土高原沟壑区天然荒草地董庄沟和植被恢复的杨家沟对比小流域,利用探地雷达探测、染色和注水入渗试验以及雨后土壤含水量观测,分析了黄土高原区入渗水影响深度及其与覆被、土壤和地形之间关系。结果表明,黄土层10~20 cm内节理、裂隙、大孔隙等垂向异质性强,且呈现沟谷向梁峁坡增大趋势;为地下水补给提供了有利途径;短时段降水入渗影响小于1 m,且随着深度增加、土壤密度增大、饱和入渗系数降低,减少了入渗水向深部运动量;林地覆盖地方大孔隙发育,增大饱和入渗系数和入渗水影响范围大;浅表20 cm土壤水分随坡地成反比、与地形指数成正比,说明沟谷洼地土壤水分高,缺水量小,是主要产流区,为揭示黄土高原区不同下垫面条件下水循环规律和降雨-径流形成机制提供基础。

Catchments of Dongzhuanggou （DZG） and Yangjiagou （YJG） in the gully region of Loess Plateau were selected as the research ar- ea, and DZG has been kept in the natural soil, while YJG has been reforested with vegetation. The relationship between infiltration water in- fluencing depth and forest coverage, soil texture and topography were revealed based on the detections of ground-penetrating radar（ GPR）, dye infiltration experiments and monocyclic infiltration experiments. The results show that the ertical heterogeneity formed by the joint, frac- tures and big pore formation within 10~ 20 cm loess is strong, and it shows increasing trend from valley to gully slope. With the increasing soil depth in the range of 0 N 1 m below the surface, the soil density increases and the saturated permeability coefficient decreases. The reduc- tion of saturated infiltration coefficient in the forest covered catchment is smaller than the brush covered catchment, which because of large pores development in the forest covers catchment. The soil moisture changes strongly within the scope of the 20 cm, and is proportional to the topographic index. Based on these conclusions, the supplied channels of deep groundwater and the runoff region near the valleys are inferred. They provide the basis for revealing water cycle rules and rainfall-runoff formation mechanisms in different underlying surface conditions of lo- ess plateau areas.