Experimental Study On Parameter-Distribution Of Soil Water Movement In Nanxiaohegou Basin

The selection and determination of soil hydraulic parameters is the basis of predicting water movement and solute transfer in soils. Soil hydraulic parameters provide evidence for the selection and determination of soil hydraulic parameters in the study of ecological environment construction and sustainable agriculture development.The problem of spatial variability of unsaturated soil is complicated, here we make the first step study on the spatial variability of unsaturated soil hydraulic properties based on the experiment and analyse exampled for Nanxiaohegou basion. The main results are showed as fllowing:1. Stable infiltration rate were between 0.239 and 4.225 mm/min in the Nanxiaohegou basin, with the mean of 1.745mm/min. Kostiakov expression had higher accuracy in transient stage, both Kostiakov and common experience could be used to estimate infiltration, common experience and Horton expression had higher accuracy in stable stage. As a whole, Kostiakov expression was fitter to estimate infiltration rate on the plateau and shady slope.2. The one parameter models of the unsaturated soil hydraulic properties are established according to the experiments. These models had higher accuracy and could be used as the variation coefficient to describe the spatial variability of soil hydraulic properties of the large scales for unlimited by soil. The single parameter varies with soil texture and topographical feature.3. The mass fractal dimension were between 2.392 and 2.593, it varied with clay grain content, the mass fractal dimension of soil particles was significant correlated with the mass percentage of soil clay content ; and propose a correlation to predict the mass fractal dimension ,the result was satisfactory. In the soil profile of different land, both the mass percentage of soil clay content and the mass fractal dimension of soil particles showed the same tendency of increasing with the soil depth, and the mass fractal dimension relates to the land uses and topographic feature.4. Fractal model of unsaturated soil water diffusivity was proposed and applied to fit fractal dimension according to measured fractal dimension, the result proved that fractal characteristic was obvious when soil water content was low. The fractal model was deduced by fractal model of soil water characteristic curve and soil unsaturated conductivity, and it could not proved in theory, only proved by measured data.5. Soil water characteristic curve was estimated by Brooks - Coreys model in Nanxiaohegou basin, the model has high accuracy and it could be applied to the large basin.6. Based on one parameter model and fractal model, the spatial distribution maps of the parameters were established for soil hydraulic properties and the physics parameters of soil.