Pedosphere 34(6): 1111--1122, 2024
ISSN 1002-0160/CN 32-1315/P
©2024 Soil Science Society of China
Published by Elsevier B.V. and Science Press
| Numerical modeling of double-ring infiltrometers for determining saturated hydraulic conductivity of heterogeneous and anisotropic soils |
Xiaoting XIE1,2, Hongxiang ZHOU3, Laosheng WU4, Jun MAN1 |
1 Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008 (China)
2 Department of Geographic Science, Faculty of Arts and Sciences, Beijing Normal University at Zhuhai, Zhuhai 519087 (China)
3 College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018 (China)
4 Department of Environmental Sciences, University of California, Riverside CA 92521 (USA) |
| ABSTRACT |
| Philip’s two-term infiltration equation has been widely used to infer soil saturated hydraulic conductivity (Ks), the accuracy of which is usually influenced by the size of infiltration rings and soil conditions. Previous studies have primarily focused on exploring the ring-size dependence of Ks estimations under specific soil conditions (e.g., soil isotropy and/or uniform initial water content). This study aimed to provide a comprehensive analysis by systematically considering eight heterogeneous and anisotropic soils with nonuniform initial water contents. Specifically, we examined the validity of Philip’s infiltration equation as well as the recently proposed two forms (i.e., infiltration and time forms) of Parlange’s infiltration equation both theoretically and in practical applications of double-ring infiltration. Then the time form of Parlange’s equation was applied to infer Ks using double-ring infiltrometer measurements with different combinations of six inner ring diameters (10, 20, 40, 80, 120, and 200 cm) and three buffer index (defined as the ratio of the difference between inner and outer ring diameters to the outer ring diameter) values (0.20, 0.33, and 0.50). For each infiltrometer set, 20 stochastic Ks fields were randomly generated by adopting five standard deviation values (0.1, 0.3, 0.5, 0.7, and 0.9). Furthermore, we investigated the effects of five horizontal correlation lengths (30, 60, 150, 300, and 600 cm) on Ks estimations. The results demonstrated that Parlange’s equation, compared to Philip’s equation, was more universal in describing the cumulative infiltration relationship for the test soils. The combination of inner ring diameter and buffer index of 40 cm and 0.2, respectively, which satisfied most of the practical requirements for determining Ks in the Soil Water Infiltration Global (SWIG) database was optimal. When the horizontal correlation length exceeded a threshold (i.e., 150 cm in our study), the inner ring diameter was required to increase to 80 cm. Our findings contribute to accurate Ks estimations of different soils using double-ring infiltrometers. |
| Key Words: buffer index,horizontal correlation length,infiltration equation,inner ring diameter,soil anisotropy,soil heterogeneity |
| Citation: Xie X T, Zhou H X, Wu L S, Man J. 2024. Numerical modeling of double-ring infiltrometers for determining saturated hydraulic conductivity of heterogeneous and anisotropic soils. Pedosphere. 34(6): 1111-1122. |
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