Studies On The Characteristics Of Soil Water Movement And Determination Of Hydraulic Parameters

On the basis of the review of the research results of soil water movement characteristics and hydraulic parameter determinations, this paper analyzed the infiltration models and methods of soil water movement parameters for different texture soils based on experimental data of horizontal one-dimensional infiltration, vertical one-dimensional infiltration, trickle irrigation and disc infiltration. The solution of theoretical analyses and laboratory experiments was adopted in the paper. The results are as follows:l.The equations for soil water characteristic curve were compared and the fitted functions were obtained for parameters of soil water characteristics curves of different soil textures. The better results were obtained when fractal theory was adapted to different soil textures. The soil water characteristics curves were calculated with the method of integral and infiltration. And the calculated values were closed to the measured ones for lower suction.2. Soil water diffusivities were calculated for different soil textures based on the observation data of horizontal one-dimensional infiltrations. Exponential functions were fitted to the relation of soil water diffusivities and soil water content. Both of soil water diffusivity and soil wateradsorption parameters decreased with the increase of clay particle content.3. On the basis of observed data, the Philip infiltration equation and Kostiakov empirical equation were analyzed. And the results showed that there is consistency in them to some extent. The fitted functions for the parameters of Green-Ampt model and Philip model were obtained. The measured data of vertical one-dimensional infiltration were used to calculate soil water conductivities for four soil textures. And the results showed that a power function was better for describing the relations of conductivities and soil water content.4. The stability analyses of disc infiltration results showed that the device of the modified disc infiltrometer is stable and available for soil water adsorption experiments the experimental results show that the cumulative infiltration decreased when negative pressure head increased for the same infiltration times and different negative pressure head. The calculations of hydraulic conductivities were conducted for different soil textures using several methods. The results showed that the larger the negative water head, the smaller the soil conductivities and soil conductivities decreased when soil clay particle content increased.5 The parameters of soil water diffusivities calculated with Burdine's mode and Mualem's mode became larger when the soil texture became coarser. Except Yulin soil, the conductivities of two soils were closed to each other for point source infiltration with disc infiltration, and one-dimensional infiltration with disc infiltration, and the larger results were found for observed values of infiltrometor and point source infiltration. To the disc infiltration observations, the calculated values of White's method was larger than those of Ankeny's and Reynolds's methods. The closer values were found for Suide soil when Ankeny's method and Reynolds's method were-IV-used, but the observed data of disc infiltrations for soil water conductivity of Suide soil was smaller than that of Xian soil.6. The equation of phreatic evaporation for different soil textures was obtained The research results provide references for calculations of phreatic evaporation in drainage design, control of salinized soils and ground water replenishment.