Spatial Variability Of Soil Water In Zhangye Oasis Irrigation Areas

Spatial variability of soil water content in Zhangye oasis irrigation area farmland was analyzed with traditional statistics and Geo-statistics. The mainly research results as following:1 The results showed that the scale takes a little influence on Mean and Media in Traditional of statistics, but has a greater effects on Variance and CV.. Along with sampling scale increasing, the coefficient of variation increased gradually.2 Under the same scale, the isograms of soil water content in the horizontal section distributed rule are different as well as the vertical , meanwhile, it different from the rule which reflected the traditional statistics parameter. However,changing pattern of isogram of soil moisture content are similar between near layers along vertical section.. While,Isogram of soil moisture content became more sparse,the numbers of closed center of Isogram decreased and the location of closed center of isogram moved with changing of scale.That illustrated that spatial variability of soil water could related closely with sample number of soil and sampling scale,soil water structural grade changes with the increasing of sampling scale,and the different soil water structural grade has different factors and processes which effected the soil water.3 With the increasing of sampling extent, the value of structure square variation tendency is not obvious but the space relevant of soil water content is obviously increased. In different scale, the figure of half variance have a great similarity, under the each lag behind distance, with sampling scale increasing, the value of half variance is reduced, but sample scale have no effect on I index4 The soil moisture content displays the different constitutive property along with the sampling scale change, the sampling scale division and the selection have a closed relation with the soil water content extent. According to the constitutive property under the small scale whether displays under an greater scale, may determine them whether belongs to the identical level the structure. Although in the identical level structure, along with the sampling scale increasing, the precision which estimated also can obviously reduce, if want to obtain the accuracy estimate or the simulation reality, must encrypt the sampling grid, enlarges the sampling work load.