非饱和水分运动参数空间变异的研究

田块尺度土壤特性的空间变异性对水分与溶质运移具有明显的影响。该研究在野外30m×30m面积、土壤类型为砂壤土的田块的100个空间点上,分别利用张力计和取土样室内测定的方法测定了30cm土层深处土壤水张力、土壤容重ρ、饱和含水率θ_s,与初始含水率θ_i,同时利用圭尔夫仪,测定了该田块同样深度108个空间点上的饱和水力传导度K_s与孔隙大小分布参数α。利用经典统计分析与地质统计分析方法分析上述参数的空间变异特征,研究结果表明:ρ,θ_i,θ_s,K_s和容水度C遵从正态分布,而α具有对数正态分布;K_s,α和C具有较大的空间变异性,而ρ和θ_s的空间变异性则较小;K_s和logα是空间统计相关的;土壤水张力的空间变异具有时不变特征,且土壤水张力方差是其均值的二次函数

Spatial Variability of Unsaturated Flow Parameters:Field Study

The field-scale spatial variability of soil properties is one of the key factors which have considerable effect on water flow and solute transport. In this paper, an experiment was conducted in a 30 m×30 m field site with sandy loam soil. The capillary tension head was measured with 100 individual mercury tensiometers which were installed at 30 cm deep. Bulk density ρ, initial soil moisture content θi and saturated soil moisture content θs were measured with 100 soil samples collected from field site, meanwhile the measurements of saturated hydraulic conductivity Ks and soil pore-size distribution parameters α in 108 locations were carried out with Guelph Permeameter. Data sets for soil properties and capillary tension head were analyzed with classical statistical and geostatistical methods. The statistical results show that soil parameters ρ,θi, θs, Ks and soil water capacity C follow approximately normal distributions, while α has a lognormal distribution. According to coefficients of variation of soil properties, it is found that Ks, α and C exhibit large spatial variability, while ρ and θs show less variability in the same field. The geostatistical results indicate that Ks and logα are spatially correlated. It is also found that capillary tension head exhibits a moderate spatial variation which is approximately time invariant. The variance of capillary tension head is a quadratic function and increases with its mean values.