流动沙丘降雨入渗和再分配过程

本文通过野外监测和模拟降雨试验对流动沙丘降雨入渗补给、再分配过程和蒸发消耗几个方面作了定量研究。结果表明：科尔沁沙地流动沙丘0～200cm深度土壤层特性具有明显的垂直变化，0～20cm为表层干沙层；20～140cm为降雨影响变化层；140cm以下为深部稳定层。土壤入渗速率受降雨强度的控制，强度大，入渗也大，入渗深度与降雨量和降雨强度之间存在线性关系。湿润锋迁移速率在降雨开始较小，而后逐渐增大，达到峰值之后，又随时间而降低，最后趋于稳定。13.4mm的降雨是无效降水和补给地下水的分界点；≥20mm的降雨可使蒸发层土壤在再分配结束后达到最小持水量；≥50mm的降雨通过土壤水分的再分配可以使120cm深度土壤水分达到饱和持水量，进而下层进行饱和排水入渗。

Infiltration and redistribution process of rainfall in desert mobile sand dune

The rainfall infiltration replenishment and redistribution process in sand dune and evaporation are studied by field observation and rainfall simulation experiment in laboratory. The result shows that the infiltration characteristic of soil varies along the depth. It may be divided into three layers: surface dry sand layer, layer affected by rainfall and stable deep layer. The infiltration rate is dependent on the rainfall intensity. The depth of infiltration is linearly related to precipitation and rainfall intensity. The rate of wetting front advancement increases at first and then tends to decrease. It reaches a steady state at last. The precipitation with 13.4mm is the critical amount dividing the useless rainfall or rainfall for supplying groundwater. When the precipitation is more than 20mm, the evaporation quantity has a little change with the increasing of rainfall. When the precipitation is more than 50mm, the soil layer of 120cm depth can reach saturated moisture capacity through redistribution and the water will infiltrate into deeper layer forming saturated drainage.