Estimation of soil water retention curve using fractal dimension

Seyedeh Zana Mahallati,Hossein Babazadeh,Ebrahim Pazira,Fariborz Abbasi

doi:10.4314/jasem.v22i2.3

Seyedeh Zana Mahallati, Hossein Babazadeh + Show 2 more

Open Access

https://doi.org/10.4314/jasem.v22i2.3

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Abstract

The soil water retention curve (SWRC) is a fundamental hydraulic property majorly used to study flow transport in soils and calculate plant-available water. Since, direct measurement of SWRC is time-consuming and expensive, different models have been developed to estimate SWRC. In this study, a fractal-based model was developed to predict SWRC. A wide range of soil textures (130 soil samples) was used to determine the fractal dimension of SWRC (DSWRC). Moreover, the SWRC pedotransfer functions were established based on easily available soil properties such as particle size distribution and bulk density by applying multiple linear regression analysis. The measured DSWRC for 110 soil samples was considered for function parameterization and the remaining was used for model validation. The results illustrated that the DSWRC linearly correlates with clay and silt contents and soil bulk density (r2 = 0.909). The SWRC can, therefore, be easily and concisely estimated by the proposed fractal-based functions. Key words: Fractal model; Pedotransfer functions; Regression analysis; Soil water retention curve

Highlights

The increasing concern with groundwater pollution and contamination of soils has stimulated the development of numerous mathematical models of pollutant transport in soils
The measured dimension of SWRC (DSWRC) for 110 soil samples was considered for function parameterization and the remaining was used for model validation
Tyler and Wheatcraft (1990) derived the unsaturated hydraulic conductivity functions based on the fractal model for the soilwater characteristic curve (SWCC) and the relative conductive models developed by Mualem (1976) and Burdine (1953)

Summary

Introduction

The increasing concern with groundwater pollution and contamination of soils has stimulated the development of numerous mathematical models of pollutant transport in soils. The most important approaches to model transient water and solute transport in the vadose zone are based on the Richards equation To solve this equation, the knowledge of the soil hydraulic properties, namely, the soil water retention curve (SWRC) and the unsaturated hydraulic conductivity is required and on the other hand, Measurements of hydraulic properties are expensive, time-consuming and highly variable (Patil and Chore, 2014). The soil water retention curve (SWRC) is one of the important hydraulic functions in water flow modeling and solute transport in the porous medium. Toledo et al, (1990) modeled the soil-water characteristic curve (SWCC) and unsaturated hydraulic conductivity using fractal geometry and thin-film theory. Determining the DSWRC from SWRC experimental data, establishing a relationship among DSWRC and soil readily available characteristics (i.e. clay, silt and sand contents and bulk density), and validating the developed relationship in SWRC estimation were the main objectives of this study

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Results

Conclusion