Estimation of soil water retention curve by using fractal dimension of soil particle size distribution

Soil water retention curve (SWRC) is an important hydraulic property in the studies of water and solute movement in soil and its direct measurement is time consuming and expensiveness. Therefore many indirect procedures like pedotransfer function and empirical models have proposed by soil scientists. In this study، a model based on fractal theory، was used to estimate water retention curve. For estimating Fractal dimension (D) that used in this model، it was tried to find out a simple relation between this parameter and feasible soil properties such as، soil particle size distribution (PSD) fractal dimension، clay، silt and sand content، ρb، dg، by applying stepwise regression analysis. The SWRC was measured for 40 soil samples، which included all soil texture classes، by pressure plate. the measured DSWRC for 33 soil samples، used for regression analysis and 7 soil samples was used for model validation. The regression analysis showed a linear relationship between DSWRC and DPSD and dg with goodness of fit، R2 = 0. 95. Estimation SWRC for 7 soil sample whit replacement estimated D by linear model، showed that the model had a good estimation، especially for light texture soils. Also there is an overestimate that can be modified by model calibration.