Prediction of Soil Water Characteristic Curve Using Physically Based Scaling Technique

Abstract

The soil water characteristic curve (SWCC) is an important hydraulic parameter for modeling water flow and contaminant transport in the vadose zone. However, direct measurement of the SWCC is still difficult. The Arya and Paris (AP) model estimates the SWCC from particle-size distribution curve (PSD) based on the shape similarity of the two curves. They introduced an empirical parameter, α, used to scale pore attributes from hypothetical formations to natural structures. Several approaches have been used to derive α. However, the calculation procedures of these approaches are either quite complicated or are developed without paying much attention to the physical significance of the soil properties. In the present paper the physically based scaling technique (PBS) was applied to derive α for the AP model. Fifty soil samples, representing a range of textures that include sand, sandy loam, loam, silt loam, and clay, were selected from UNSODA hydraulic property database for calculating α using PBS approach. In addition, nineteen soil samples with different textures were used to verify effectiveness of proposed α values. The results compared with other approaches show that the PBS technique combine with the AP model is a more useful and easier approach to predict SWCC from PSD.

Evaluating the Scale Factors of Pedo-Transfer Modeling the Soil Water Characteristic Curve of Zakho Soils

“…Another method suggested by the same researcher and also adopted by (S. Liu, et al, 2013) for the estimation of is to linear fit between and as follows: (12) The constant values of the scale factor obtained by constant method and the linear parameter and, ( that obtained by the above methods are shown in Table (2). (Vaz et al 2005), appraise the performance of the AP model by employing an expression for as a function of the soil volumetric water content, (θ); as (13) The aforementioned scaling methods have been utilized in association with the Arya and Paris algorithm for estimation the soil water characteristic curve relationships for the soil specimens of Zakho city.…”