表层土壤饱和导水率的空间变异对农田水分渗漏的影响

本文将条件模拟方法所得到的表层土壤饱和导水率(Ks)的随机场与土壤水分运动模型相结合，随机地模拟了冬小麦地1999年3月10日～6月10日这一时段的农田水分渗漏情况。总来水量为 353.8mm(灌水量270mm)的情况下，2m土体水分渗漏量最小值为23.73mm，最大值达到了64.73mm，分别占此段灌水量的8.8％和24.0％。另外，比较了实测法、克立格插值法和100次条件模拟得到的水分渗漏量结果，发现条件模拟法与实测法的结果较接近，而克立格插值法具有明显的“平滑效应”，缩小了农田水分渗漏量的范围。这3种方法均反映了表层土壤Ks空间变异对农田水分渗漏的影响，其结果均要好于传统方法。

Effect of spatial variability of surface soil saturated hydraulic conductivity on water drainage at field scale

The objective of this paper is to evaluate the effect of spatial variability of the surface soil saturated hydraulic conductivity(K_s) on water drainage.A conditional simulation(CS) method was used to get a random field of the surface soil K_s based on 117 observed values in the field.Then,a soil water movement model(HYDRUS-1D) was coupled with the random field of the surface soil K_s.During the period from March 10 to June 10,1999,water drainage was stochastically simulated with the total water income being 353.8 mm(including 270mm irrigation rate).The accumulated quantities of the water drainage ranged from 23.73 mm to 64.73 mm in the soil profile 2 m in depth,accounting for about 8.8% and 24.0% of the irrigation rate during this period.The accumulated quantities of the water drainage were calculated by measured method,ordinary Kriging(OK) method and CS method,respectively.Their results were compared.It was found that the accumulated quantities of the water drainage obtained by CS method agreed well with that by the measured method,while the water drainage range was shortened by the OK method because of its obviously'smoothing effect'.The effect of spatial variability of the surface soil K_s on water drainage could be reflected by the three methods and their results were all better than the traditional method,which does not consider the spatial variability of the surface soil K_s.