Modelling The Soil Moisture Based On DEM And Soil Moisture Sampling Data

The Loess Plateau is the most serious soil erosion in China. In order to improve the ecological environment, our country launched a large scope works of returning farmland to forests and planting trees and grass at the Loess Plateau. Because the determination of vegetation types and structure in ecological construction mainly depends on soil moisture, the soil moisture content and its distribution become one of the main factors of evaluation of regional ecological environment.In this paper, based on the soil moisture data sampled at Xiannangou Watershed in Ansai County of Shaanxi Province month by month, using digital terrain analysis methods, calculated the topographic wetness index of Xiannangou Watershed by using the single flow direction algorithm and multiple flow direction algorithm at the same time, according to the data which combined with sample soil moisture data and topographic wetness index data, analyzed the correlation of soil moisture and topographic wetness index. Then analyzed the quality of single flow direction algorithm and multiple flow direction algorithm by comparing the correlation of soil moisture and their topographic wetness index, put forward the best flow direction algorithm to soil moisture simulation. In order to achieve soil moisture simulation of the entire Xiannangou Watershed, this paper also takes other environmental variables such as aspect and land-use types which impact the soil moisture into account. Studied the method of soil moisture simulation using topographic wetness index, slope and land-use types, meanwhile, built the simulation models of soil moisture using the measured soil moisture data and evaluated the accuracy of the model. Because the process of soil moisture simulation combining procedures of topographic wetness index calculation algorithm and related software such as ArcGIS software is relatively complicated and error-prone, this paper, based on the basic algorithm of soil moisture simulation, combined with software development methods, developed a small watershed model of soil moisture simulation. The operation of the model is very easy, combined with automation and human intervention, achieved the generation and output of soil moisture raster images. Finally, this paper completed the soil moisture simulation from May to October in 2008 at Xiannangou Watershed , analyzed the characteristics of the soil moisture spatial distribution and dynamic Changes, and evaluated the status of the soil moisture.