Estimation of saturated hydraulic conductivity of the soil surface layer by combining transfer functions and remote sensing (Case Study: South of Ahwaz Lands)

Document Type : Research Paper

Authors

• Mansour Sorkheh Nejad ¹
• Mohammad Albaji ¹
• Abd Ali Naseri ²
• Saeed Boroomand Nasab ²

¹ Department of Irrigation and Drainage, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran

² Department of Irrigation and Drainage, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Abstract

Keywords

• Sentinel-2
• Soil properties
• Soil texture
• Vegetation index

20.1001.1.2008479.1402.54.1.7.7

Main Subjects

• آبیاری و زهکشی

EXTENDED ABSTRACT

Introduction:

 In order to absorb water, the plant needs a suitable environment. During the irrigation, the environment becomes saturated. After depletion of gravity water from the plant root zone, unsaturated state in the soil occured. Based on this, the study and measurement of soil hydraulic conductivity and penetration are the essential parameters of the soil and water resources management. Hydraulic conductivity is one of the most important physical properties of the soil, which plays a vital role in solute and pollutant transport in the porous environments such as soil.

Objective:

 This study aims to obtain pedotransfer functions (PTFs) for saturated and unsaturated hydraulic conductivity using soil properties and satellite images.

Materials and methods:

 In this regard, soil sampling was performed in some parts of the southwest of Khuzestan province at 50 points. After that, soil samples were passed through a 2 mm sieve for homogenizing, and soil properties such as soil texture, electrical conductivity, soil organic carbon, and saturated moisture were determined in the laboratory. Then, saturated hydraulic conductivity was determined at the same sampling points in the field. Then after, indicators of Sentinel-2 satellite images were obtained. For this purpose, visible, infrared, mid-infrared, and short-infrared satellite images were prepared with a spatial resolution of 20 m², and the indices of Sentinel-2 satellite images were calculated in three categories of soil, vegetation, and moisture. Finally, 11 PTFs, (PTF₁-PTF₁₁) for saturated hydraulic conductivity were obtained in four stages by combining soil properties and the aformentioned indices.

Results and discussion:

 The results of the PTFs models for saturated hydraulic conductivity showed that among the 11 models, the combination of three vegetation indices with easily measured soil properties was the most effective PTF model for estimating the saturated hydraulic conductivity (with R² = 0.57, RMSE = 0.63 and MAE = 0.40). While the PTF₇ model obtained by combination of the vegetation cover index and soil properties had R² = 0.83, RMSE = 0.4 and MAE = 0.166. Finally, the spatial distribution of saturated hydraulic conductivity using the Random Forest model showed a better performance, as compared to the others.

Conclusion:

Based on the obtained results, it was found that PTFs obtained from soil properties alone cannot estimate the soil hydraulic conductivity with appropriate accuracy. Therefore, it is suggested in addition of soil properties, satellite images indices are used for modeling PTFs, in order to improve estimation of saturated hydraulic conductivity in the soil.

 Keywords: Sentinel-2,  Soil properties,  Soil texture,  Vegetation index.