The Couping Relationship Between Soil Water Content And The Buried Depth Of Groundwater On Yutian Oasis

Soil water is an important component of soil, and it is the important content of the soil physics research. Soil water not only affects the soil physical properties, but also restricts the dissolution and transfer of the minerals, nutrients and other elements, as well as the activities of soil microorganisms, so it is also an important factor to measure soil fertility. At the same time, it has a direct impact on crop yield and vegetation growth, as well as, to some extent, the micro-climate. And arid agriculture relys on soil water resource, which provide with 60% of the yield. Groundwater is the primary factor to maintain the life in arid area, especially in desert areas.In this context, this paper set up a pilot area of about 100km2 in the northwest of Kirkuk Town on Yutian Oasis. And it studied the spatial variability of the soil water content and the buried depth of groundwater by classical statistics and geostatistics method. Then the relationship between the soil water content and groundwater buried depth was analyzed by overlaying the two interpolation maps. Conclusions were as follow:1. The average value of soil water content of 0~50cm soil layer in the test area all gradually increases from top to bottom, and their variation coefficients all belong to strong variation. The One-Sample Kolmogorov-Smirnov (K-S) tests show that soil water content of all layers are all subject to normal distribution, and they are all consistent with the requirements of statistics and semi-variance models to establish. Except that the water content of 45~50cm is fitted with Gaussian model, the others are all fitted with the Spherical models.2. The variation coefficient of buried depth of groundwater in the test area is bigger than 30%, and it belongs to strong variation. The One-Sample Kolmogorov- Smirnov (K-S) tests show that it is subject to normal distribution, and it is fitted with Gaussian model. 3. The nuggets of soil water content are relatively bigger, indicating that there exist substrate effects because of sampling error, the randomness of sampling scale and the inherent variability, and the nugget correlation coefficient indicate that they all have mediate spacial correlation. While the nugget of buried depth of groundwater is very small, and the nugget coefficient indicate that it has servious spacial correlation.4. Through comprehensive analysis and cross-validation, the paper finds that Kriging interpolation method is the best in all interpolation methods of water content in the test area. Then the soil water content was analyzed through Kriging interpolation method in the test area. The analyse find that soil water content increases from top to bottom gradually, and the distributions pattern of all soil layers are simlar. It is low-value area in the northeast as well as the southwest corner of the test area, while the northwest and southeast is the high-value area.5. Through comprehensive analysis and cross-validation, the paper finds that Kriging interpolation method is the best in all interpolation methods of buried depth in the test area. With the help of Kriging interpolation method, the paper generates the three-dimensional map of the buried depth, the three-dimensional map of the buried depth in different altitude elevation and the gradient distribution map of the buried depth of groundwater in the test area. Through analyses, the paper finds that there is shallow depth of groundwater area in the southeastern corner and the northwest part of the test area, where the depth of groundwater is below 1 meter; There is mediate depth of groundwater area in the southeast part and the southwest corner of the test area, where the depth of groundwater is between 1 meter and 2 meters; There is deep depth of groundwater area in the middle of the test area, where the depth of groundwater is above 2 meters, and particully, the depth of groundwater is bigger than 3 meters in the north part of the test area.6. When the buried depth of groundwater increases, the water content of 0~50cm soil layers all decreases gradually; With the increase of soil profiles depth, the water content of all of 0~50cm soil layers increases gradually from upper layer to the down at each gradient distribution map of the buried depth of groundwater in the test area.7. When the buried depth of groundwater is smaller than 2.5m, the correlation relationship between the buried depth and 0~5cm water content, 15~20cm water content, 45~50cm water content and 0~50cm water content is all obvious, and the correlation relationship increases gradually from the top to the bottom.8. When the buried depth of groundwater is bigger than 2.5m, the correlation relationship between the buried depth of groundwater and the water content of 0~50cm different soil layers is a little worse. But with the the increase of soil profiles depth, the correlation relationship between the buried depth and the water content has a gradually increasing trend.