荒漠区包气带土壤物理特征及其对地下水毛管上升影响的模拟

Soil physical characteristics of shallow vadose zone and modeling its effects on upward capillary rise of groundwater in an arid-desert area

以巴丹吉林沙漠边缘荒漠区域为研究对象,选取两种典型的沙丘土壤剖面(沙壤土和砂土混合,均一砂土)进行土壤物理特征分析,并在此基础上模拟了不同土壤因素对毛管水上升过程的影响,探讨毛管水上升变化与土壤物理性质的关系,试图揭示地下水-毛管水-土壤水之间的相互作用过程.结果表明:研究区地下水毛管上升主要受土壤容重和土壤黏粒含量的影响,并且毛管水上升高度在地下潜水层以上为沙壤土的剖面中能够达到152 cm;地下潜水层以上为砂土的剖面中为120 cm.砂土中毛管水补给区域各土层水分分布更为均匀,并且从潜水面至地面方向土壤含水量呈递减趋势,沙壤土中毛管水补给区域土壤水分变异较大.借助Hydrus-3D模型能够较好模拟多因子影响下的土壤毛管水运动过程.潜水面以上土壤结构变化显著影响毛管水上升和剖面水分分布状况,但毛管水上升是否受季节性蒸发变化的影响以及毛管水与植物需水的关系有待进一步探究.

Two typical soil profiles of sand dune(mixed sandy loam with sandy soil;uniform sandy soil)were selected from the arid region on the edge of the Badain Jaran desert to analyze soil physical characteristics.The effects of soil physical characteristics on capillary rise were monitored and simulated.The relationship between two typical soil profiles of sand dune and capillary rise were investigated to reveal the interactive processes among groundwater,capillary water,and soil water.Results showed that capillary rise was mainly affected by soil bulk density and soil clay content in the arid-desert area.The capillary rise could reach to 152 cm above shallow layer in the profile of mixed sandy loam with sandy soils,and 120 cm in the profile of sandy soil,respectively.Soil water distribution driven by the capillary rise was more uniform in the profile of sandy soil.Soil water content showed a diminishing trend from the groundwater to the maximum distance of capillary rise.In contrast,soil water distribution was markedly varied in the profile of mixed sandy loam with sandy soil.The process of capillary movement could be well simulated with Hydrus-3D model.Soil structure above the groundwater was the critical factor,which could affect the capillary rise and soil water distribution.However,the effects of soil in-season evaporation and plant root uptake on capillary rise movement need to be explored in further studies.