Modeling preferential water flow and solute transport in unsaturated soil using the active region model |
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Authors: | Feng Sheng Kang Wang Renduo Zhang Huihai Liu |
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Institution: | (1) School of Environmental Science and Engineering, Sun Yat-Sen (Zhongshan) University, Guangzhou, 510275, China;(2) School of Water Conservancy, Changsha University of Science and Technology, Changsha, 410114, China;(3) State Key Laboratory of Water Resources and Hydropower Engineering Science, Wuhan University, Wuhan, 430072, China;(4) Earth Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA |
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Abstract: | Preferential flow and solute transport are common processes in the unsaturated soil, in which distributions of soil water
content and solute concentrations are often characterized as fractal patterns. An active region model (ARM) was recently proposed
to describe the preferential flow and transport patterns. In this study, ARM governing equations were derived to model the
preferential soil water flow and solute transport processes. To evaluate the ARM equations, dye infiltration experiments were
conducted, in which distributions of soil water content and Cl− concentration were measured. Predicted results using the ARM and the mobile–immobile region model (MIM) were compared with
the measured distributions of soil water content and Cl− concentration. Although both the ARM and the MIM are two-region models, they are fundamentally different in terms of treatments
of the flow region. The models were evaluated based on the modeling efficiency (ME). The MIM provided relatively poor prediction
results of the preferential flow and transport with negative ME values or positive ME values less than 0.4. On the contrary,
predicted distributions of soil water content and Cl− concentration using the ARM agreed reasonably well with the experimental data, with ME values higher than 0.8. The results
indicated that the ARM successfully captured the macroscopic behavior of preferential flow and solute transport in the unsaturated
soil. |
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